WebSVN – Kolibri OS – Diff – /programs/develop/libraries/libpng/pngrtran.c

 /* pngrtran.c - transforms the data in a row for PNG readers
+ *
- * Last changed in libpng 1.5.1 [February 3, 2011]
+ * Last changed in libpng 1.6.4 [September 14, 2013]
- * Copyright (c) 1998-2011 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2013 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+ *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
+ *
  * This file contains functions optionally called by an application
  * in order to tell libpng how to handle data when reading a PNG.
  * Transformations that are used in both reading and writing are
  * in pngtrans.c.
  */
 #include "pngpriv.h"
 #ifdef PNG_READ_SUPPORTED
 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
 void PNGAPI
-png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
+png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
 {
    png_debug(1, "in png_set_crc_action");
    if (png_ptr == NULL)
       return;
    /* Tell libpng how we react to CRC errors in critical chunks */
    switch (crit_action)
+   {
       case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */
          break;
       case PNG_CRC_WARN_USE:                               /* Warn/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
          break;
       case PNG_CRC_QUIET_USE:                             /* Quiet/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
                            PNG_FLAG_CRC_CRITICAL_IGNORE;
          break;
       case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
          png_warning(png_ptr,
             "Can't discard critical data on CRC error");
       case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
       case PNG_CRC_DEFAULT:
       default:
          png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
          break;
+   }
    /* Tell libpng how we react to CRC errors in ancillary chunks */
    switch (ancil_action)
+   {
       case PNG_CRC_NO_CHANGE:                       /* Leave setting as is */
          break;
       case PNG_CRC_WARN_USE:                              /* Warn/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
          break;
       case PNG_CRC_QUIET_USE:                            /* Quiet/use data */
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
                            PNG_FLAG_CRC_ANCILLARY_NOWARN;
          break;
       case PNG_CRC_ERROR_QUIT:                               /* Error/quit */
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
          break;
       case PNG_CRC_WARN_DISCARD:                      /* Warn/discard data */
       case PNG_CRC_DEFAULT:
       default:
          png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
          break;
+   }
+}
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+/* Is it OK to set a transformation now?  Only if png_start_read_image or
+ * png_read_update_info have not been called.  It is not necessary for the IHDR
+ * to have been read in all cases, the parameter allows for this check too.
+ */
+static int
+png_rtran_ok(png_structrp png_ptr, int need_IHDR)
+{
+   if (png_ptr != NULL)
+   {
+      if (png_ptr->flags & PNG_FLAG_ROW_INIT)
+         png_app_error(png_ptr,
+            "invalid after png_start_read_image or png_read_update_info");
+      else if (need_IHDR && (png_ptr->mode & PNG_HAVE_IHDR) == 0)
+         png_app_error(png_ptr, "invalid before the PNG header has been read");
+      else
+      {
+         /* Turn on failure to initialize correctly for all transforms. */
+         png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
+         return 1; /* Ok */
+      }
+   }
+   return 0; /* no png_error possible! */
+}
+#endif
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
 /* Handle alpha and tRNS via a background color */
 void PNGFAPI
-png_set_background_fixed(png_structp png_ptr,
+png_set_background_fixed(png_structrp png_ptr,
     png_const_color_16p background_color, int background_gamma_code,
     int need_expand, png_fixed_point background_gamma)
+{
    png_debug(1, "in png_set_background_fixed");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0) || background_color == NULL)
       return;
    if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
+   {
       png_warning(png_ptr, "Application must supply a known background gamma");
       return;
+   }
+   png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
-   png_ptr->transformations |= PNG_BACKGROUND;
+   png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-   png_memcpy(&(png_ptr->background), background_color,
+   png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-      png_sizeof(png_color_16));
+   png_ptr->background = *background_color;
    png_ptr->background_gamma = background_gamma;
    png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
+   if (need_expand)
-   png_ptr->transformations |= (need_expand ? PNG_BACKGROUND_EXPAND : 0);
+      png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
+   else
+      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
+}
 #  ifdef PNG_FLOATING_POINT_SUPPORTED
 void PNGAPI
-png_set_background(png_structp png_ptr,
+png_set_background(png_structrp png_ptr,
     png_const_color_16p background_color, int background_gamma_code,
     int need_expand, double background_gamma)
+{
    png_set_background_fixed(png_ptr, background_color, background_gamma_code,
       need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
+}
 #  endif  /* FLOATING_POINT */
 #endif /* READ_BACKGROUND */
+/* Scale 16-bit depth files to 8-bit depth.  If both of these are set then the
+ * one that pngrtran does first (scale) happens.  This is necessary to allow the
+ * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
+ */
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+void PNGAPI
+png_set_scale_16(png_structrp png_ptr)
+{
+   png_debug(1, "in png_set_scale_16");
+   if (!png_rtran_ok(png_ptr, 0))
+      return;
+   png_ptr->transformations |= PNG_SCALE_16_TO_8;
+}
+#endif
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
-/* Strip 16 bit depth files to 8 bit depth */
+/* Chop 16-bit depth files to 8-bit depth */
 void PNGAPI
-png_set_strip_16(png_structp png_ptr)
+png_set_strip_16(png_structrp png_ptr)
+{
    png_debug(1, "in png_set_strip_16");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
    png_ptr->transformations |= PNG_16_TO_8;
+}
 #endif
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
 void PNGAPI
-png_set_strip_alpha(png_structp png_ptr)
+png_set_strip_alpha(png_structrp png_ptr)
 {
    png_debug(1, "in png_set_strip_alpha");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
+   png_ptr->transformations |= PNG_STRIP_ALPHA;
+}
+#endif
+#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
+static png_fixed_point
+translate_gamma_flags(png_structrp png_ptr, png_fixed_point output_gamma,
+   int is_screen)
+{
+   /* Check for flag values.  The main reason for having the old Mac value as a
+    * flag is that it is pretty near impossible to work out what the correct
+    * value is from Apple documentation - a working Mac system is needed to
+    * discover the value!
+    */
+   if (output_gamma == PNG_DEFAULT_sRGB ||
+      output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
+   {
+      /* If there is no sRGB support this just sets the gamma to the standard
+       * sRGB value.  (This is a side effect of using this function!)
+       */
+#     ifdef PNG_READ_sRGB_SUPPORTED
+         png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
+#     else
+         PNG_UNUSED(png_ptr)
+#     endif
+      if (is_screen)
+         output_gamma = PNG_GAMMA_sRGB;
+      else
+         output_gamma = PNG_GAMMA_sRGB_INVERSE;
+   }
+   else if (output_gamma == PNG_GAMMA_MAC_18 ||
+      output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
+   {
+      if (is_screen)
+         output_gamma = PNG_GAMMA_MAC_OLD;
+      else
+         output_gamma = PNG_GAMMA_MAC_INVERSE;
+   }
+   return output_gamma;
+}
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+static png_fixed_point
+convert_gamma_value(png_structrp png_ptr, double output_gamma)
+{
+   /* The following silently ignores cases where fixed point (times 100,000)
+    * gamma values are passed to the floating point API.  This is safe and it
+    * means the fixed point constants work just fine with the floating point
+    * API.  The alternative would just lead to undetected errors and spurious
+    * bug reports.  Negative values fail inside the _fixed API unless they
+    * correspond to the flag values.
+    */
+   if (output_gamma > 0 && output_gamma < 128)
+      output_gamma *= PNG_FP_1;
+   /* This preserves -1 and -2 exactly: */
+   output_gamma = floor(output_gamma + .5);
+   if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
+      png_fixed_error(png_ptr, "gamma value");
-   png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
+   return (png_fixed_point)output_gamma;
+}
+#  endif
+#endif /* READ_ALPHA_MODE || READ_GAMMA */
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+void PNGFAPI
+png_set_alpha_mode_fixed(png_structrp png_ptr, int mode,
+   png_fixed_point output_gamma)
+{
+   int compose = 0;
+   png_fixed_point file_gamma;
+   png_debug(1, "in png_set_alpha_mode");
+   if (!png_rtran_ok(png_ptr, 0))
+      return;
+   output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
+   /* Validate the value to ensure it is in a reasonable range. The value
+    * is expected to be 1 or greater, but this range test allows for some
+    * viewing correction values.  The intent is to weed out users of this API
+    * who use the inverse of the gamma value accidentally!  Since some of these
+    * values are reasonable this may have to be changed.
+    */
+   if (output_gamma < 70000 || output_gamma > 300000)
+      png_error(png_ptr, "output gamma out of expected range");
+   /* The default file gamma is the inverse of the output gamma; the output
+    * gamma may be changed below so get the file value first:
+    */
+   file_gamma = png_reciprocal(output_gamma);
+   /* There are really 8 possibilities here, composed of any combination
+    * of:
+    *
+    *    premultiply the color channels
+    *    do not encode non-opaque pixels
+    *    encode the alpha as well as the color channels
+    *
+    * The differences disappear if the input/output ('screen') gamma is 1.0,
+    * because then the encoding is a no-op and there is only the choice of
+    * premultiplying the color channels or not.
+    *
+    * png_set_alpha_mode and png_set_background interact because both use
+    * png_compose to do the work.  Calling both is only useful when
+    * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
+    * with a default gamma value.  Otherwise PNG_COMPOSE must not be set.
+    */
+   switch (mode)
+   {
+      case PNG_ALPHA_PNG:        /* default: png standard */
+         /* No compose, but it may be set by png_set_background! */
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+         break;
+      case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
+         compose = 1;
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+         /* The output is linear: */
+         output_gamma = PNG_FP_1;
+         break;
+      case PNG_ALPHA_OPTIMIZED:  /* associated, non-opaque pixels linear */
+         compose = 1;
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
+         /* output_gamma records the encoding of opaque pixels! */
+         break;
+      case PNG_ALPHA_BROKEN:     /* associated, non-linear, alpha encoded */
+         compose = 1;
+         png_ptr->transformations |= PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+         break;
+      default:
+         png_error(png_ptr, "invalid alpha mode");
+   }
+   /* Only set the default gamma if the file gamma has not been set (this has
+    * the side effect that the gamma in a second call to png_set_alpha_mode will
+    * be ignored.)
+    */
+   if (png_ptr->colorspace.gamma == 0)
+   {
+      png_ptr->colorspace.gamma = file_gamma;
+      png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
+   }
+   /* But always set the output gamma: */
+   png_ptr->screen_gamma = output_gamma;
+   /* Finally, if pre-multiplying, set the background fields to achieve the
+    * desired result.
+    */
+   if (compose)
+   {
+      /* And obtain alpha pre-multiplication by composing on black: */
+      memset(&png_ptr->background, 0, (sizeof png_ptr->background));
+      png_ptr->background_gamma = png_ptr->colorspace.gamma; /* just in case */
+      png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
+      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
+      if (png_ptr->transformations & PNG_COMPOSE)
+         png_error(png_ptr,
+            "conflicting calls to set alpha mode and background");
+      png_ptr->transformations |= PNG_COMPOSE;
+   }
+}
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
+{
+   png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
+      output_gamma));
+}
+#  endif
 #endif
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
-/* Dither file to 8 bit.  Supply a palette, the current number
+/* Dither file to 8-bit.  Supply a palette, the current number
  * of elements in the palette, the maximum number of elements
  * allowed, and a histogram if possible.  If the current number
  * of colors is greater then the maximum number, the palette will be
  * modified to fit in the maximum number.  "full_quantize" indicates
  * whether we need a quantizing cube set up for RGB images, or if we
  * simply are reducing the number of colors in a paletted image.
  */
 typedef struct png_dsort_struct
+{
-   struct png_dsort_struct FAR * next;
+   struct png_dsort_struct * next;
    png_byte left;
    png_byte right;
 } png_dsort;
-typedef png_dsort FAR *       png_dsortp;
+typedef png_dsort *   png_dsortp;
-typedef png_dsort FAR * FAR * png_dsortpp;
+typedef png_dsort * * png_dsortpp;
 void PNGAPI
-png_set_quantize(png_structp png_ptr, png_colorp palette,
+png_set_quantize(png_structrp png_ptr, png_colorp palette,
     int num_palette, int maximum_colors, png_const_uint_16p histogram,
     int full_quantize)
+{
    png_debug(1, "in png_set_quantize");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
    png_ptr->transformations |= PNG_QUANTIZE;
    if (!full_quantize)
+   {
       int i;
       png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
-          (png_uint_32)(num_palette * png_sizeof(png_byte)));
+          (png_uint_32)(num_palette * (sizeof (png_byte))));
       for (i = 0; i < num_palette; i++)
          png_ptr->quantize_index[i] = (png_byte)i;
+   }
    if (num_palette > maximum_colors)
+   {
       if (histogram != NULL)
+      {
          /* This is easy enough, just throw out the least used colors.
           * Perhaps not the best solution, but good enough.
           */
          int i;
          /* Initialize an array to sort colors */
          png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)(num_palette * png_sizeof(png_byte)));
+             (png_uint_32)(num_palette * (sizeof (png_byte))));
          /* Initialize the quantize_sort array */
          for (i = 0; i < num_palette; i++)
             png_ptr->quantize_sort[i] = (png_byte)i;
          /* Find the least used palette entries by starting a
           * bubble sort, and running it until we have sorted
           * out enough colors.  Note that we don't care about
           * sorting all the colors, just finding which are
           * least used.
           */
          for (i = num_palette - 1; i >= maximum_colors; i--)
+         {
             int done; /* To stop early if the list is pre-sorted */
             int j;
             done = 1;
             for (j = 0; j < i; j++)
+            {
                if (histogram[png_ptr->quantize_sort[j]]
                    < histogram[png_ptr->quantize_sort[j + 1]])
+               {
                   png_byte t;
                   t = png_ptr->quantize_sort[j];
                   png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
                   png_ptr->quantize_sort[j + 1] = t;
                   done = 0;
+               }
+            }
             if (done)
                break;
+         }
          /* Swap the palette around, and set up a table, if necessary */
          if (full_quantize)
+         {
             int j = num_palette;
             /* Put all the useful colors within the max, but don't
              * move the others.
              */
             for (i = 0; i < maximum_colors; i++)
+            {
                if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+               {
                   do
                      j--;
                   while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
                   palette[i] = palette[j];
+               }
+            }
+         }
          else
+         {
             int j = num_palette;
             /* Move all the used colors inside the max limit, and
              * develop a translation table.
              */
             for (i = 0; i < maximum_colors; i++)
+            {
                /* Only move the colors we need to */
                if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+               {
                   png_color tmp_color;
                   do
                      j--;
                   while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
                   tmp_color = palette[j];
                   palette[j] = palette[i];
                   palette[i] = tmp_color;
                   /* Indicate where the color went */
                   png_ptr->quantize_index[j] = (png_byte)i;
                   png_ptr->quantize_index[i] = (png_byte)j;
+               }
+            }
             /* Find closest color for those colors we are not using */
             for (i = 0; i < num_palette; i++)
+            {
                if ((int)png_ptr->quantize_index[i] >= maximum_colors)
+               {
                   int min_d, k, min_k, d_index;
                   /* Find the closest color to one we threw out */
                   d_index = png_ptr->quantize_index[i];
                   min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
                   for (k = 1, min_k = 0; k < maximum_colors; k++)
+                  {
                      int d;
                      d = PNG_COLOR_DIST(palette[d_index], palette[k]);
                      if (d < min_d)
+                     {
                         min_d = d;
                         min_k = k;
+                     }
+                  }
                   /* Point to closest color */
                   png_ptr->quantize_index[i] = (png_byte)min_k;
+               }
+            }
+         }
          png_free(png_ptr, png_ptr->quantize_sort);
          png_ptr->quantize_sort = NULL;
+      }
       else
+      {
          /* This is much harder to do simply (and quickly).  Perhaps
           * we need to go through a median cut routine, but those
           * don't always behave themselves with only a few colors
           * as input.  So we will just find the closest two colors,
           * and throw out one of them (chosen somewhat randomly).
           * [We don't understand this at all, so if someone wants to
           *  work on improving it, be our guest - AED, GRP]
           */
          int i;
          int max_d;
          int num_new_palette;
          png_dsortp t;
          png_dsortpp hash;
          t = NULL;
          /* Initialize palette index arrays */
          png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)(num_palette * png_sizeof(png_byte)));
+             (png_uint_32)(num_palette * (sizeof (png_byte))));
          png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)(num_palette * png_sizeof(png_byte)));
+             (png_uint_32)(num_palette * (sizeof (png_byte))));
          /* Initialize the sort array */
          for (i = 0; i < num_palette; i++)
+         {
             png_ptr->index_to_palette[i] = (png_byte)i;
             png_ptr->palette_to_index[i] = (png_byte)i;
+         }
          hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
-             png_sizeof(png_dsortp)));
+             (sizeof (png_dsortp))));
          num_new_palette = num_palette;
          /* Initial wild guess at how far apart the farthest pixel
           * pair we will be eliminating will be.  Larger
           * numbers mean more areas will be allocated, Smaller
           * numbers run the risk of not saving enough data, and
           * having to do this all over again.
+          *
           * I have not done extensive checking on this number.
           */
          max_d = 96;
          while (num_new_palette > maximum_colors)
+         {
             for (i = 0; i < num_new_palette - 1; i++)
+            {
                int j;
                for (j = i + 1; j < num_new_palette; j++)
+               {
                   int d;
                   d = PNG_COLOR_DIST(palette[i], palette[j]);
                   if (d <= max_d)
+                  {
                      t = (png_dsortp)png_malloc_warn(png_ptr,
-                         (png_uint_32)(png_sizeof(png_dsort)));
+                         (png_uint_32)(sizeof (png_dsort)));
                      if (t == NULL)
                          break;
                      t->next = hash[d];
                      t->left = (png_byte)i;
                      t->right = (png_byte)j;
                      hash[d] = t;
+                  }
+               }
                if (t == NULL)
                   break;
+            }
             if (t != NULL)
             for (i = 0; i <= max_d; i++)
+            {
                if (hash[i] != NULL)
+               {
                   png_dsortp p;
                   for (p = hash[i]; p; p = p->next)
+                  {
                      if ((int)png_ptr->index_to_palette[p->left]
                          < num_new_palette &&
                          (int)png_ptr->index_to_palette[p->right]
                          < num_new_palette)
+                     {
                         int j, next_j;
                         if (num_new_palette & 0x01)
+                        {
                            j = p->left;
                            next_j = p->right;
+                        }
                         else
+                        {
                            j = p->right;
                            next_j = p->left;
+                        }
                         num_new_palette--;
                         palette[png_ptr->index_to_palette[j]]
                             = palette[num_new_palette];
                         if (!full_quantize)
+                        {
                            int k;
                            for (k = 0; k < num_palette; k++)
+                           {
                               if (png_ptr->quantize_index[k] ==
                                   png_ptr->index_to_palette[j])
                                  png_ptr->quantize_index[k] =
                                      png_ptr->index_to_palette[next_j];
                               if ((int)png_ptr->quantize_index[k] ==
                                   num_new_palette)
                                  png_ptr->quantize_index[k] =
                                      png_ptr->index_to_palette[j];
+                           }
+                        }
                         png_ptr->index_to_palette[png_ptr->palette_to_index
                             [num_new_palette]] = png_ptr->index_to_palette[j];
                         png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
                             = png_ptr->palette_to_index[num_new_palette];
                         png_ptr->index_to_palette[j] =
                             (png_byte)num_new_palette;
                         png_ptr->palette_to_index[num_new_palette] =
                             (png_byte)j;
+                     }
                      if (num_new_palette <= maximum_colors)
                         break;
+                  }
                   if (num_new_palette <= maximum_colors)
                      break;
+               }
+            }
             for (i = 0; i < 769; i++)
+            {
                if (hash[i] != NULL)
+               {
                   png_dsortp p = hash[i];
                   while (p)
+                  {
                      t = p->next;
                      png_free(png_ptr, p);
                      p = t;
+                  }
+               }
                hash[i] = 0;
+            }
             max_d += 96;
+         }
          png_free(png_ptr, hash);
          png_free(png_ptr, png_ptr->palette_to_index);
          png_free(png_ptr, png_ptr->index_to_palette);
          png_ptr->palette_to_index = NULL;
          png_ptr->index_to_palette = NULL;
+      }
       num_palette = maximum_colors;
+   }
    if (png_ptr->palette == NULL)
+   {
       png_ptr->palette = palette;
+   }
    png_ptr->num_palette = (png_uint_16)num_palette;
    if (full_quantize)
+   {
       int i;
       png_bytep distance;
       int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
           PNG_QUANTIZE_BLUE_BITS;
       int num_red = (1 << PNG_QUANTIZE_RED_BITS);
       int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
       int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
       png_size_t num_entries = ((png_size_t)1 << total_bits);
       png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
-          (png_uint_32)(num_entries * png_sizeof(png_byte)));
+          (png_uint_32)(num_entries * (sizeof (png_byte))));
       distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
-          png_sizeof(png_byte)));
+          (sizeof (png_byte))));
-      png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));
+      memset(distance, 0xff, num_entries * (sizeof (png_byte)));
       for (i = 0; i < num_palette; i++)
+      {
          int ir, ig, ib;
          int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
          int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
          int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
          for (ir = 0; ir < num_red; ir++)
+         {
             /* int dr = abs(ir - r); */
             int dr = ((ir > r) ? ir - r : r - ir);
             int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
                 PNG_QUANTIZE_GREEN_BITS));
             for (ig = 0; ig < num_green; ig++)
+            {
                /* int dg = abs(ig - g); */
                int dg = ((ig > g) ? ig - g : g - ig);
                int dt = dr + dg;
                int dm = ((dr > dg) ? dr : dg);
                int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
                for (ib = 0; ib < num_blue; ib++)
+               {
                   int d_index = index_g | ib;
                   /* int db = abs(ib - b); */
                   int db = ((ib > b) ? ib - b : b - ib);
                   int dmax = ((dm > db) ? dm : db);
                   int d = dmax + dt + db;
                   if (d < (int)distance[d_index])
+                  {
                      distance[d_index] = (png_byte)d;
                      png_ptr->palette_lookup[d_index] = (png_byte)i;
+                  }
+               }
+            }
+         }
+      }
       png_free(png_ptr, distance);
+   }
+}
 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
 #ifdef PNG_READ_GAMMA_SUPPORTED
-/* Transform the image from the file_gamma to the screen_gamma.  We
+void PNGFAPI
- * only do transformations on images where the file_gamma and screen_gamma
- * are not close reciprocals, otherwise it slows things down slightly, and
- * also needlessly introduces small errors.
- *
- * We will turn off gamma transformation later if no semitransparent entries
- * are present in the tRNS array for palette images.  We can't do it here
- * because we don't necessarily have the tRNS chunk yet.
- */
-static int /* PRIVATE */
-png_gamma_threshold(png_fixed_point scrn_gamma, png_fixed_point file_gamma)
-{
-   /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
-    * correction as a difference of the overall transform from 1.0
-    *
-    * We want to compare the threshold with s*f - 1, if we get
-    * overflow here it is because of wacky gamma values so we
-    * turn on processing anyway.
-    */
-   png_fixed_point gtest;
-   return !png_muldiv(>est, scrn_gamma, file_gamma, PNG_FP_1) ||
-       png_gamma_significant(gtest);
-}
-void PNGFAPI
-png_set_gamma_fixed(png_structp png_ptr, png_fixed_point scrn_gamma,
+png_set_gamma_fixed(png_structrp png_ptr, png_fixed_point scrn_gamma,
    png_fixed_point file_gamma)
+{
    png_debug(1, "in png_set_gamma_fixed");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
+   /* New in libpng-1.5.4 - reserve particular negative values as flags. */
+   scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
+   file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
+   /* Checking the gamma values for being >0 was added in 1.5.4 along with the
+    * premultiplied alpha support; this actually hides an undocumented feature
+    * of the previous implementation which allowed gamma processing to be
+    * disabled in background handling.  There is no evidence (so far) that this
+    * was being used; however, png_set_background itself accepted and must still
+    * accept '0' for the gamma value it takes, because it isn't always used.
+    *
+    * Since this is an API change (albeit a very minor one that removes an
+    * undocumented API feature) the following checks were only enabled in
+    * libpng-1.6.0.
+    */
-   if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
+   if (file_gamma <= 0)
+      png_error(png_ptr, "invalid file gamma in png_set_gamma");
-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ||
+   if (scrn_gamma <= 0)
+      png_error(png_ptr, "invalid screen gamma in png_set_gamma");
+   /* Set the gamma values unconditionally - this overrides the value in the PNG
-       png_gamma_threshold(scrn_gamma, file_gamma))
+    * file if a gAMA chunk was present.  png_set_alpha_mode provides a
+    * different, easier, way to default the file gamma.
-      png_ptr->transformations |= PNG_GAMMA;
+    */
+   png_ptr->colorspace.gamma = file_gamma;
-   png_ptr->gamma = file_gamma;
+   png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
    png_ptr->screen_gamma = scrn_gamma;
+}
 #  ifdef PNG_FLOATING_POINT_SUPPORTED
 void PNGAPI
-png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
+png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
 {
-   png_set_gamma_fixed(png_ptr,
+   png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
-      png_fixed(png_ptr, scrn_gamma, "png_set_gamma screen gamma"),
-      png_fixed(png_ptr, file_gamma, "png_set_gamma file gamma"));
+      convert_gamma_value(png_ptr, file_gamma));
 }
 #  endif /* FLOATING_POINT_SUPPORTED */
 #endif /* READ_GAMMA */
 #ifdef PNG_READ_EXPAND_SUPPORTED
 /* Expand paletted images to RGB, expand grayscale images of
  * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
  * to alpha channels.
  */
 void PNGAPI
-png_set_expand(png_structp png_ptr)
+png_set_expand(png_structrp png_ptr)
 {
    png_debug(1, "in png_set_expand");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
-}
 /* GRR 19990627:  the following three functions currently are identical
  *  to png_set_expand().  However, it is entirely reasonable that someone
  *  might wish to expand an indexed image to RGB but *not* expand a single,
  *  fully transparent palette entry to a full alpha channel--perhaps instead
  *  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
  *  the transparent color with a particular RGB value, or drop tRNS entirely.
  *  IOW, a future version of the library may make the transformations flag
  *  a bit more fine-grained, with separate bits for each of these three
  *  functions.
+ *
  *  More to the point, these functions make it obvious what libpng will be
  *  doing, whereas "expand" can (and does) mean any number of things.
+ *
  *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
  *  to expand only the sample depth but not to expand the tRNS to alpha
  *  and its name was changed to png_set_expand_gray_1_2_4_to_8().
  */
 /* Expand paletted images to RGB. */
 void PNGAPI
-png_set_palette_to_rgb(png_structp png_ptr)
+png_set_palette_to_rgb(png_structrp png_ptr)
 {
    png_debug(1, "in png_set_palette_to_rgb");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
-}
 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
 void PNGAPI
-png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
+png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr)
 {
    png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 0))
       return;
    png_ptr->transformations |= PNG_EXPAND;
    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
-}
 /* Expand tRNS chunks to alpha channels. */
 void PNGAPI
-png_set_tRNS_to_alpha(png_structp png_ptr)
+png_set_tRNS_to_alpha(png_structrp png_ptr)
+{
    png_debug(1, "in png_set_tRNS_to_alpha");
+   if (!png_rtran_ok(png_ptr, 0))
+      return;
    png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
 #endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
+ * it may not work correctly.)
+ */
+void PNGAPI
+png_set_expand_16(png_structrp png_ptr)
+{
+   png_debug(1, "in png_set_expand_16");
+   if (!png_rtran_ok(png_ptr, 0))
+      return;
+   png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
+}
+#endif
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
 void PNGAPI
-png_set_gray_to_rgb(png_structp png_ptr)
+png_set_gray_to_rgb(png_structrp png_ptr)
+{
    png_debug(1, "in png_set_gray_to_rgb");
-   if (png_ptr != NULL)
+   if (!png_rtran_ok(png_ptr, 0))
-   {
+      return;
-      /* Because rgb must be 8 bits or more: */
+   /* Because rgb must be 8 bits or more: */
-      png_set_expand_gray_1_2_4_to_8(png_ptr);
+   png_set_expand_gray_1_2_4_to_8(png_ptr);
-      png_ptr->transformations |= PNG_GRAY_TO_RGB;
+   png_ptr->transformations |= PNG_GRAY_TO_RGB;
       png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
-   }
-}
 #endif
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 void PNGFAPI
-png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
+png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
     png_fixed_point red, png_fixed_point green)
+{
    png_debug(1, "in png_set_rgb_to_gray");
+   /* Need the IHDR here because of the check on color_type below. */
+   /* TODO: fix this */
-   if (png_ptr == NULL)
+   if (!png_rtran_ok(png_ptr, 1))
       return;
    switch(error_action)
+   {
-      case 1:
+      case PNG_ERROR_ACTION_NONE:
          png_ptr->transformations |= PNG_RGB_TO_GRAY;
          break;
-      case 2:
+      case PNG_ERROR_ACTION_WARN:
          png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
          break;
-      case 3:
+      case PNG_ERROR_ACTION_ERROR:
          png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
          break;
       default:
          png_error(png_ptr, "invalid error action to rgb_to_gray");
          break;
+   }
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
 #ifdef PNG_READ_EXPAND_SUPPORTED
       png_ptr->transformations |= PNG_EXPAND;
 #else
+   {
-      png_warning(png_ptr,
+      /* Make this an error in 1.6 because otherwise the application may assume
+       * that it just worked and get a memory overwrite.
+       */
+      png_error(png_ptr,
         "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
-      png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
+      /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
+   }
 #endif
+   {
-      png_uint_16 red_int, green_int;
+      if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
-      if (red < 0 || green < 0)
       {
-         red_int   =  6968; /* .212671 * 32768 + .5 */
+         png_uint_16 red_int, green_int;
-         green_int = 23434; /* .715160 * 32768 + .5 */
-      }
+         /* NOTE: this calculation does not round, but this behavior is retained
+          * for consistency, the inaccuracy is very small.  The code here always
+          * overwrites the coefficients, regardless of whether they have been
-      else if (red + green < 100000L)
+          * defaulted or set already.
-      {
+          */
-         red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
+         red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
-         green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
+         green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
+         png_ptr->rgb_to_gray_red_coeff   = red_int;
+         png_ptr->rgb_to_gray_green_coeff = green_int;
+         png_ptr->rgb_to_gray_coefficients_set = 1;
+      }
       else
+      {
-         png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
+         if (red >= 0 && green >= 0)
-         red_int   =  6968;
+            png_app_warning(png_ptr,
-         green_int = 23434;
+               "ignoring out of range rgb_to_gray coefficients");
-      }
+         /* Use the defaults, from the cHRM chunk if set, else the historical
+          * values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See
+          * png_do_rgb_to_gray for more discussion of the values.  In this case
+          * the coefficients are not marked as 'set' and are not overwritten if
+          * something has already provided a default.
+          */
-      png_ptr->rgb_to_gray_red_coeff   = red_int;
+         if (png_ptr->rgb_to_gray_red_coeff == 0 &&
-      png_ptr->rgb_to_gray_green_coeff = green_int;
+            png_ptr->rgb_to_gray_green_coeff == 0)
+         {
-      png_ptr->rgb_to_gray_blue_coeff  =
+            png_ptr->rgb_to_gray_red_coeff   = 6968;
-          (png_uint_16)(32768 - red_int - green_int);
+            png_ptr->rgb_to_gray_green_coeff = 23434;
+            /* png_ptr->rgb_to_gray_blue_coeff  = 2366; */
+         }
+      }
+   }
+}
 #ifdef PNG_FLOATING_POINT_SUPPORTED
 /* Convert a RGB image to a grayscale of the same width.  This allows us,
  * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
  */
 void PNGAPI
-png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
+png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
    double green)
+{
-   if (png_ptr == NULL)
+   png_set_rgb_to_gray_fixed(png_ptr, error_action,
-      return;
-   png_set_rgb_to_gray_fixed(png_ptr, error_action,
       png_fixed(png_ptr, red, "rgb to gray red coefficient"),
       png_fixed(png_ptr, green, "rgb to gray green coefficient"));
+}
 #endif /* FLOATING POINT */
-#endif
+#endif /* RGB_TO_GRAY */
 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
     defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
 void PNGAPI
-png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
+png_set_read_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
     read_user_transform_fn)
+{
    png_debug(1, "in png_set_read_user_transform_fn");
-   if (png_ptr == NULL)
-      return;
 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    png_ptr->transformations |= PNG_USER_TRANSFORM;
    png_ptr->read_user_transform_fn = read_user_transform_fn;
 #endif
+}
 #endif
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* In the case of gamma transformations only do transformations on images where
+ * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
+ * slows things down slightly, and also needlessly introduces small errors.
+ */
+static int /* PRIVATE */
+png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
+{
+   /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
+    * correction as a difference of the overall transform from 1.0
+    *
+    * We want to compare the threshold with s*f - 1, if we get
+    * overflow here it is because of wacky gamma values so we
+    * turn on processing anyway.
+    */
+   png_fixed_point gtest;
+   return !png_muldiv(>est, screen_gamma, file_gamma, PNG_FP_1) ||
+       png_gamma_significant(gtest);
+}
+#endif
 /* Initialize everything needed for the read.  This includes modifying
  * the palette.
  */
 void /* PRIVATE */
+/*For the moment 'png_init_palette_transformations' and
+ * 'png_init_rgb_transformations' only do some flag canceling optimizations.
+ * The intent is that these two routines should have palette or rgb operations
+ * extracted from 'png_init_read_transformations'.
+ */
+static void /* PRIVATE */
-png_init_read_transformations(png_structp png_ptr)
+png_init_palette_transformations(png_structrp png_ptr)
 {
-   png_debug(1, "in png_init_read_transformations");
+   /* Called to handle the (input) palette case.  In png_do_read_transformations
+    * the first step is to expand the palette if requested, so this code must
+    * take care to only make changes that are invariant with respect to the
+    * palette expansion, or only do them if there is no expansion.
+    *
+    * STRIP_ALPHA has already been handled in the caller (by setting num_trans
+    * to 0.)
+    */
+   int input_has_alpha = 0;
+   int input_has_transparency = 0;
+   if (png_ptr->num_trans > 0)
+   {
+      int i;
+      /* Ignore if all the entries are opaque (unlikely!) */
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
+      for (i=0; inum_trans; ++i)
+      {
-    defined(PNG_READ_SHIFT_SUPPORTED) || \
+         if (png_ptr->trans_alpha[i] == 255)
+            continue;
+         else if (png_ptr->trans_alpha[i] == 0)
+            input_has_transparency = 1;
+         else
+         {
+            input_has_transparency = 1;
+            input_has_alpha = 1;
+            break;
+         }
+      }
+   }
+   /* If no alpha we can optimize. */
+   if (!input_has_alpha)
+   {
+      /* Any alpha means background and associative alpha processing is
+       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
-    defined(PNG_READ_GAMMA_SUPPORTED)
+       * and ENCODE_ALPHA are irrelevant.
+       */
+      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-   int color_type = png_ptr->color_type;
+      if (!input_has_transparency)
+         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
-#endif
+   }
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+   /* png_set_background handling - deals with the complexity of whether the
+    * background color is in the file format or the screen format in the case
+    * where an 'expand' will happen.
-#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+    */
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   /* Detect gray background and attempt to enable optimization
-    * for gray --> RGB case
-    *
-    * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
-    * RGB_ALPHA (in which case need_expand is superfluous anyway), the
-    * background color might actually be gray yet not be flagged as such.
-    * This is not a problem for the current code, which uses
-    * PNG_BACKGROUND_IS_GRAY only to decide when to do the
+   /* The following code cannot be entered in the alpha pre-multiplication case
-    * png_do_gray_to_rgb() transformation.
+    * because PNG_BACKGROUND_EXPAND is cancelled below.
     */
    if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-       !(color_type & PNG_COLOR_MASK_COLOR))
-   {
+       (png_ptr->transformations & PNG_EXPAND))
+   {
+      {
+         png_ptr->background.red   =
+             png_ptr->palette[png_ptr->background.index].red;
+         png_ptr->background.green =
+             png_ptr->palette[png_ptr->background.index].green;
-      png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+         png_ptr->background.blue  =
-   }
+             png_ptr->palette[png_ptr->background.index].blue;
-   else if ((png_ptr->transformations & PNG_BACKGROUND) &&
-       !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
        (png_ptr->transformations & PNG_GRAY_TO_RGB) &&
-       png_ptr->background.red == png_ptr->background.green &&
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+        {
+           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+           {
-       png_ptr->background.red == png_ptr->background.blue)
+              /* Invert the alpha channel (in tRNS) unless the pixels are
+               * going to be expanded, in which case leave it for later
+               */
+              int i, istop = png_ptr->num_trans;
+              for (i=0; i
                  png_ptr->trans_alpha[i] = (png_byte)(255 -
+                    png_ptr->trans_alpha[i]);
+           }
+        }
+#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
+      }
+   } /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+static void /* PRIVATE */
+png_init_rgb_transformations(png_structrp png_ptr)
+{
+   /* Added to libpng-1.5.4: check the color type to determine whether there
+    * is any alpha or transparency in the image and simply cancel the
+    * background and alpha mode stuff if there isn't.
+    */
+   int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+   int input_has_transparency = png_ptr->num_trans > 0;
+   /* If no alpha we can optimize. */
+   if (!input_has_alpha)
+   {
+      /* Any alpha means background and associative alpha processing is
+       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
+       * and ENCODE_ALPHA are irrelevant.
+       */
-      png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+#     ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+#     endif
+      if (!input_has_transparency)
+         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
+   }
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+   /* png_set_background handling - deals with the complexity of whether the
+    * background color is in the file format or the screen format in the case
+    * where an 'expand' will happen.
+    */
       png_ptr->background.gray = png_ptr->background.red;
-   }
+   /* The following code cannot be entered in the alpha pre-multiplication case
+    * because PNG_BACKGROUND_EXPAND is cancelled below.
+    */
-#endif
+   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+       (png_ptr->transformations & PNG_EXPAND) &&
-       (png_ptr->transformations & PNG_EXPAND))
+       !(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+       /* i.e., GRAY or GRAY_ALPHA */
+   {
+      {
          /* Expand background and tRNS chunks */
-      if (!(color_type & PNG_COLOR_MASK_COLOR))  /* i.e., GRAY or GRAY_ALPHA */
+         int gray = png_ptr->background.gray;
          int trans_gray = png_ptr->trans_color.gray;
          /* Expand background and tRNS chunks */
          switch (png_ptr->bit_depth)
+         {
             case 1:
-               png_ptr->background.gray *= (png_uint_16)0xff;
+               gray *= 0xff;
-               png_ptr->background.red = png_ptr->background.green
-                   =  png_ptr->background.blue = png_ptr->background.gray;
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                 png_ptr->trans_color.gray *= (png_uint_16)0xff;
+               trans_gray *= 0xff;
-                 png_ptr->trans_color.red = png_ptr->trans_color.green
+               break;
-                     = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
-               }
-               break;
             case 2:
-               png_ptr->background.gray *= (png_uint_16)0x55;
+               gray *= 0x55;
-               png_ptr->background.red = png_ptr->background.green
-                   = png_ptr->background.blue = png_ptr->background.gray;
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                  png_ptr->trans_color.gray *= (png_uint_16)0x55;
+               trans_gray *= 0x55;
-                  png_ptr->trans_color.red = png_ptr->trans_color.green
+               break;
-                      = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
-               }
-               break;
             case 4:
-               png_ptr->background.gray *= (png_uint_16)0x11;
+               gray *= 0x11;
-               png_ptr->background.red = png_ptr->background.green
-                   = png_ptr->background.blue = png_ptr->background.gray;
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                  png_ptr->trans_color.gray *= (png_uint_16)0x11;
+               trans_gray *= 0x11;
-                  png_ptr->trans_color.red = png_ptr->trans_color.green
+               break;
-                      = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
-               }
-               break;
             default:
             case 8:
                /* FALL THROUGH (Already 8 bits) */
             case 16:
-               png_ptr->background.red = png_ptr->background.green
+               /* Already a full 16 bits */
-                   = png_ptr->background.blue = png_ptr->background.gray;
                break;
+         }
+         png_ptr->background.red = png_ptr->background.green =
+            png_ptr->background.blue = (png_uint_16)gray;
+         if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+         {
+            png_ptr->trans_color.red = png_ptr->trans_color.green =
+               png_ptr->trans_color.blue = (png_uint_16)trans_gray;
+         }
+      }
-      else if (color_type == PNG_COLOR_TYPE_PALETTE)
+   } /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+void /* PRIVATE */
+png_init_read_transformations(png_structrp png_ptr)
+{
-         png_ptr->background.red   =
-             png_ptr->palette[png_ptr->background.index].red;
-         png_ptr->background.green =
-             png_ptr->palette[png_ptr->background.index].green;
-         png_ptr->background.blue  =
-             png_ptr->palette[png_ptr->background.index].blue;
+   png_debug(1, "in png_init_read_transformations");
+   /* This internal function is called from png_read_start_row in pngrutil.c
+    * and it is called before the 'rowbytes' calculation is done, so the code
+    * in here can change or update the transformations flags.
+    *
+    * First do updates that do not depend on the details of the PNG image data
+    * being processed.
+    */
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
+    * png_set_alpha_mode and this is another source for a default file gamma so
+    * the test needs to be performed later - here.  In addition prior to 1.5.4
-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+    * the tests were repeated for the PALETTE color type here - this is no
+    * longer necessary (and doesn't seem to have been necessary before.)
-        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+    */
+   {
+      /* The following temporary indicates if overall gamma correction is
+       * required.
-        {
+       */
+      int gamma_correction = 0;
-#ifdef PNG_READ_EXPAND_SUPPORTED
-           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-#endif
+      if (png_ptr->colorspace.gamma != 0) /* has been set */
+      {
+         if (png_ptr->screen_gamma != 0) /* screen set too */
+            gamma_correction = png_gamma_threshold(png_ptr->colorspace.gamma,
+               png_ptr->screen_gamma);
-           {
+         else
-              /* Invert the alpha channel (in tRNS) unless the pixels are
+            /* Assume the output matches the input; a long time default behavior
-               * going to be expanded, in which case leave it for later
+             * of libpng, although the standard has nothing to say about this.
-               */
-              int i, istop;
-              istop=(int)png_ptr->num_trans;
-              for (i=0; i
+             */
-                 png_ptr->trans_alpha[i] = (png_byte)(255 -
-                    png_ptr->trans_alpha[i]);
+            png_ptr->screen_gamma = png_reciprocal(png_ptr->colorspace.gamma);
+      }
+      else if (png_ptr->screen_gamma != 0)
+         /* The converse - assume the file matches the screen, note that this
+          * perhaps undesireable default can (from 1.5.4) be changed by calling
+          * png_set_alpha_mode (even if the alpha handling mode isn't required
+          * or isn't changed from the default.)
+          */
+         png_ptr->colorspace.gamma = png_reciprocal(png_ptr->screen_gamma);
+      else /* neither are set */
+         /* Just in case the following prevents any processing - file and screen
+          * are both assumed to be linear and there is no way to introduce a
+          * third gamma value other than png_set_background with 'UNIQUE', and,
+          * prior to 1.5.4
+          */
+         png_ptr->screen_gamma = png_ptr->colorspace.gamma = PNG_FP_1;
+      /* We have a gamma value now. */
+      png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
+      /* Now turn the gamma transformation on or off as appropriate.  Notice
+       * that PNG_GAMMA just refers to the file->screen correction.  Alpha
+       * composition may independently cause gamma correction because it needs
+       * linear data (e.g. if the file has a gAMA chunk but the screen gamma
+       * hasn't been specified.)  In any case this flag may get turned off in
+       * the code immediately below if the transform can be handled outside the
+       * row loop.
+       */
+      if (gamma_correction)
+         png_ptr->transformations |= PNG_GAMMA;
+      else
          png_ptr->transformations &= ~PNG_GAMMA;
+   }
 #endif
+   /* Certain transformations have the effect of preventing other
+    * transformations that happen afterward in png_do_read_transformations,
+    * resolve the interdependencies here.  From the code of
+    * png_do_read_transformations the order is:
+    *
+    *  1) PNG_EXPAND (including PNG_EXPAND_tRNS)
+    *  2) PNG_STRIP_ALPHA (if no compose)
+    *  3) PNG_RGB_TO_GRAY
+    *  4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
+    *  5) PNG_COMPOSE
+    *  6) PNG_GAMMA
+    *  7) PNG_STRIP_ALPHA (if compose)
+    *  8) PNG_ENCODE_ALPHA
+    *  9) PNG_SCALE_16_TO_8
+    * 10) PNG_16_TO_8
+    * 11) PNG_QUANTIZE (converts to palette)
+    * 12) PNG_EXPAND_16
+    * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
+    * 14) PNG_INVERT_MONO
+    * 15) PNG_SHIFT
+    * 16) PNG_PACK
+    * 17) PNG_BGR
+    * 18) PNG_PACKSWAP
+    * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
+    * 20) PNG_INVERT_ALPHA
+    * 21) PNG_SWAP_ALPHA
+    * 22) PNG_SWAP_BYTES
+    * 23) PNG_USER_TRANSFORM [must be last]
+    */
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+      !(png_ptr->transformations & PNG_COMPOSE))
+   {
+      /* Stripping the alpha channel happens immediately after the 'expand'
+       * transformations, before all other transformation, so it cancels out
+       * the alpha handling.  It has the side effect negating the effect of
+       * PNG_EXPAND_tRNS too:
+       */
+      png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
+         PNG_EXPAND_tRNS);
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+      /* Kill the tRNS chunk itself too.  Prior to 1.5.4 this did not happen
+       * so transparency information would remain just so long as it wasn't
+       * expanded.  This produces unexpected API changes if the set of things
+       * that do PNG_EXPAND_tRNS changes (perfectly possible given the
+       * documentation - which says ask for what you want, accept what you
+       * get.)  This makes the behavior consistent from 1.5.4:
+       */
+      png_ptr->num_trans = 0;
+   }
+#endif /* STRIP_ALPHA supported, no COMPOSE */
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+   /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
+    * settings will have no effect.
+    */
+   if (!png_gamma_significant(png_ptr->screen_gamma))
+   {
+      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+   }
 #endif
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) && defined(PNG_READ_GAMMA_SUPPORTED)
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+   /* Make sure the coefficients for the rgb to gray conversion are set
+    * appropriately.
+    */
-   png_ptr->background_1 = png_ptr->background;
+   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+      png_colorspace_set_rgb_coefficients(png_ptr);
 #endif
-#ifdef PNG_READ_GAMMA_SUPPORTED
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+   /* Detect gray background and attempt to enable optimization for
+    * gray --> RGB case.
+    *
+    * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
+    * RGB_ALPHA (in which case need_expand is superfluous anyway), the
+    * background color might actually be gray yet not be flagged as such.
+    * This is not a problem for the current code, which uses
+    * PNG_BACKGROUND_IS_GRAY only to decide when to do the
+    * png_do_gray_to_rgb() transformation.
+    *
+    * TODO: this code needs to be revised to avoid the complexity and
+    * interdependencies.  The color type of the background should be recorded in
+    * png_set_background, along with the bit depth, then the code has a record
+    * of exactly what color space the background is currently in.
+    */
+   if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
+   {
+      /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
+       * the file was grayscale the background value is gray.
+       */
+      if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+         png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+   }
+   else if (png_ptr->transformations & PNG_COMPOSE)
+   {
-   if ((color_type == PNG_COLOR_TYPE_PALETTE && png_ptr->num_trans != 0)
+      /* PNG_COMPOSE: png_set_background was called with need_expand false,
+       * so the color is in the color space of the output or png_set_alpha_mode
+       * was called and the color is black.  Ignore RGB_TO_GRAY because that
+       * happens before GRAY_TO_RGB.
+       */
-       && png_gamma_threshold(png_ptr->screen_gamma, png_ptr->gamma))
+      if (png_ptr->transformations & PNG_GRAY_TO_RGB)
-   {
+      {
-      int i, k;
-      k=0;
+         if (png_ptr->background.red == png_ptr->background.green &&
-      for (i=0; inum_trans; i++)
+             png_ptr->background.red == png_ptr->background.blue)
-      {
+         {
-        if (png_ptr->trans_alpha[i] != 0 && png_ptr->trans_alpha[i] != 0xff)
+            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+            png_ptr->background.gray = png_ptr->background.red;
            k=1; /* Partial transparency is present */
-      }
-      if (k == 0)
          png_ptr->transformations &= ~PNG_GAMMA;
+   }
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED */
+   /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
+    * can be performed directly on the palette, and some (such as rgb to gray)
+    * can be optimized inside the palette.  This is particularly true of the
+    * composite (background and alpha) stuff, which can be pretty much all done
+    * in the palette even if the result is expanded to RGB or gray afterward.
+    *
+    * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
+    * earlier and the palette stuff is actually handled on the first row.  This
+    * leads to the reported bug that the palette returned by png_get_PLTE is not
+    * updated.
+    */
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      png_init_palette_transformations(png_ptr);
+   else
+      png_init_rgb_transformations(png_ptr);
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+   defined(PNG_READ_EXPAND_16_SUPPORTED)
+   if ((png_ptr->transformations & PNG_EXPAND_16) &&
+      (png_ptr->transformations & PNG_COMPOSE) &&
+      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+      png_ptr->bit_depth != 16)
+   {
+      /* TODO: fix this.  Because the expand_16 operation is after the compose
+       * handling the background color must be 8, not 16, bits deep, but the
+       * application will supply a 16-bit value so reduce it here.
+       *
+       * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
+       * present, so that case is ok (until do_expand_16 is moved.)
+       *
+       * NOTE: this discards the low 16 bits of the user supplied background
+       * color, but until expand_16 works properly there is no choice!
+       */
+#     define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
+      CHOP(png_ptr->background.red);
+      CHOP(png_ptr->background.green);
+      CHOP(png_ptr->background.blue);
+      CHOP(png_ptr->background.gray);
+#     undef CHOP
+   }
+#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
-   }
+   (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
+   defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
+   if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
+      (png_ptr->transformations & PNG_COMPOSE) &&
+      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+      png_ptr->bit_depth == 16)
+   {
+      /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
+       * component this will also happen after PNG_COMPOSE and so the background
+       * color must be pre-expanded here.
+       *
+       * TODO: fix this too.
+       */
+      png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
+      png_ptr->background.green =
+         (png_uint_16)(png_ptr->background.green * 257);
+      png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
+      png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
+   }
+#endif
+   /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
+    * background support (see the comments in scripts/pnglibconf.dfa), this
+    * allows pre-multiplication of the alpha channel to be implemented as
+    * compositing on black.  This is probably sub-optimal and has been done in
+    * 1.5.4 betas simply to enable external critique and testing (i.e. to
+    * implement the new API quickly, without lots of internal changes.)
+    */
+#ifdef PNG_READ_GAMMA_SUPPORTED
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
+      /* Includes ALPHA_MODE */
+      png_ptr->background_1 = png_ptr->background;
+#  endif
+   /* This needs to change - in the palette image case a whole set of tables are
+    * built when it would be quicker to just calculate the correct value for
+    * each palette entry directly.  Also, the test is too tricky - why check
+    * PNG_RGB_TO_GRAY if PNG_GAMMA is not set?  The answer seems to be that
+    * PNG_GAMMA is cancelled even if the gamma is known?  The test excludes the
+    * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
+    * the gamma tables will not be built even if composition is required on a
+    * gamma encoded value.
+    *
+    * In 1.5.4 this is addressed below by an additional check on the individual
+    * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
+    * tables.
+    */
+   if ((png_ptr->transformations & PNG_GAMMA)
+      || ((png_ptr->transformations & PNG_RGB_TO_GRAY)
+         && (png_gamma_significant(png_ptr->colorspace.gamma) ||
+            png_gamma_significant(png_ptr->screen_gamma)))
+      || ((png_ptr->transformations & PNG_COMPOSE)
+         && (png_gamma_significant(png_ptr->colorspace.gamma)
+            || png_gamma_significant(png_ptr->screen_gamma)
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
+            || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
+               && png_gamma_significant(png_ptr->background_gamma))
+#  endif
+      )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
-   if ((png_ptr->transformations & (PNG_GAMMA | PNG_RGB_TO_GRAY)) &&
+         && png_gamma_significant(png_ptr->screen_gamma))
        png_ptr->gamma != 0)
+   {
       png_build_gamma_table(png_ptr, png_ptr->bit_depth);
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
-      if (png_ptr->transformations & PNG_BACKGROUND)
+      if (png_ptr->transformations & PNG_COMPOSE)
       {
-         if (color_type == PNG_COLOR_TYPE_PALETTE)
+         /* Issue a warning about this combination: because RGB_TO_GRAY is
+          * optimized to do the gamma transform if present yet do_background has
+          * to do the same thing if both options are set a
+          * double-gamma-correction happens.  This is true in all versions of
+          * libpng to date.
+          */
+         if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+            png_warning(png_ptr,
+               "libpng does not support gamma+background+rgb_to_gray");
+         if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
          {
-            /* Could skip if no transparency */
+            /* We don't get to here unless there is a tRNS chunk with non-opaque
+             * entries - see the checking code at the start of this function.
-            png_color back, back_1;
+             */
+            png_color back, back_1;
             png_colorp palette = png_ptr->palette;
             int num_palette = png_ptr->num_palette;
             int i;
             if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
+            {
                back.red = png_ptr->gamma_table[png_ptr->background.red];
                back.green = png_ptr->gamma_table[png_ptr->background.green];
                back.blue = png_ptr->gamma_table[png_ptr->background.blue];
                back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
                back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
                back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
+            }
             else
+            {
                png_fixed_point g, gs;
                switch (png_ptr->background_gamma_type)
+               {
                   case PNG_BACKGROUND_GAMMA_SCREEN:
                      g = (png_ptr->screen_gamma);
                      gs = PNG_FP_1;
                      break;
                   case PNG_BACKGROUND_GAMMA_FILE:
-                     g = png_reciprocal(png_ptr->gamma);
+                     g = png_reciprocal(png_ptr->colorspace.gamma);
-                     gs = png_reciprocal2(png_ptr->gamma,
+                     gs = png_reciprocal2(png_ptr->colorspace.gamma,
                         png_ptr->screen_gamma);
                      break;
                   case PNG_BACKGROUND_GAMMA_UNIQUE:
                      g = png_reciprocal(png_ptr->background_gamma);
                      gs = png_reciprocal2(png_ptr->background_gamma,
                         png_ptr->screen_gamma);
                      break;
                   default:
                      g = PNG_FP_1;    /* back_1 */
                      gs = PNG_FP_1;   /* back */
                      break;
+               }
                if (png_gamma_significant(gs))
+               {
-                  back.red   = (png_byte)png_ptr->background.red;
+                  back.red = png_gamma_8bit_correct(png_ptr->background.red,
-                  back.green = (png_byte)png_ptr->background.green;
-                  back.blue  = (png_byte)png_ptr->background.blue;
-               }
-               else
-               {
-                  back.red = png_gamma_8bit_correct(png_ptr->background.red,
                       gs);
                   back.green = png_gamma_8bit_correct(png_ptr->background.green,
                       gs);
                   back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
                       gs);
+               }
                back_1.red = png_gamma_8bit_correct(png_ptr->background.red, g);
+               else
+               {
+                  back.red   = (png_byte)png_ptr->background.red;
-               back_1.green = png_gamma_8bit_correct(png_ptr->background.green,
+                  back.green = (png_byte)png_ptr->background.green;
+                  back.blue  = (png_byte)png_ptr->background.blue;
+               }
+               if (png_gamma_significant(g))
+               {
+                  back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
-                   g);
+                     g);
-               back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
+                  back_1.green = png_gamma_8bit_correct(
+                     png_ptr->background.green, g);
+                  back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
-                   g);
+                     g);
+               }
             for (i = 0; i < num_palette; i++)
+               else
+               {
+                  back_1.red   = (png_byte)png_ptr->background.red;
+                  back_1.green = (png_byte)png_ptr->background.green;
+                  back_1.blue  = (png_byte)png_ptr->background.blue;
+               }
+            }
+            for (i = 0; i < num_palette; i++)
+            {
                if (i < (int)png_ptr->num_trans &&
                    png_ptr->trans_alpha[i] != 0xff)
+               {
                   if (png_ptr->trans_alpha[i] == 0)
+                  {
                      palette[i] = back;
+                  }
                   else /* if (png_ptr->trans_alpha[i] != 0xff) */
+                  {
                      png_byte v, w;
                      v = png_ptr->gamma_to_1[palette[i].red];
                      png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
                      palette[i].red = png_ptr->gamma_from_1[w];
                      v = png_ptr->gamma_to_1[palette[i].green];
                      png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
                      palette[i].green = png_ptr->gamma_from_1[w];
                      v = png_ptr->gamma_to_1[palette[i].blue];
                      png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
                      palette[i].blue = png_ptr->gamma_from_1[w];
+                  }
+               }
                else
+               {
                   palette[i].red = png_ptr->gamma_table[palette[i].red];
                   palette[i].green = png_ptr->gamma_table[palette[i].green];
                   palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+               }
+            }
             /* Prevent the transformations being done again, and make sure
+            /* Prevent the transformations being done again.
-             * that the now spurious alpha channel is stripped - the code
+             *
+             * NOTE: this is highly dubious; it removes the transformations in
-             * has just reduced background composition and gamma correction
+             * place.  This seems inconsistent with the general treatment of the
-             * to a simple alpha channel strip.
+             * transformations elsewhere.
              */
-            png_ptr->transformations &= ~PNG_BACKGROUND;
+            png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
-            png_ptr->transformations &= ~PNG_GAMMA;
-            png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
+         } /* color_type == PNG_COLOR_TYPE_PALETTE */
-         }
          /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
-         else
-         /* color_type != PNG_COLOR_TYPE_PALETTE */
+         else /* color_type != PNG_COLOR_TYPE_PALETTE */
+         {
+            int gs_sig, g_sig;
-            png_fixed_point g = PNG_FP_1;
+            png_fixed_point g = PNG_FP_1;  /* Correction to linear */
-            png_fixed_point gs = PNG_FP_1;
+            png_fixed_point gs = PNG_FP_1; /* Correction to screen */
             switch (png_ptr->background_gamma_type)
+            {
                case PNG_BACKGROUND_GAMMA_SCREEN:
                   g = png_ptr->screen_gamma;
                   /* gs = PNG_FP_1; */
                   break;
                case PNG_BACKGROUND_GAMMA_FILE:
-                  g = png_reciprocal(png_ptr->gamma);
+                  g = png_reciprocal(png_ptr->colorspace.gamma);
-                  gs = png_reciprocal2(png_ptr->gamma, png_ptr->screen_gamma);
+                  gs = png_reciprocal2(png_ptr->colorspace.gamma,
-                  break;
+                     png_ptr->screen_gamma);
+                  break;
                case PNG_BACKGROUND_GAMMA_UNIQUE:
                   g = png_reciprocal(png_ptr->background_gamma);
                   gs = png_reciprocal2(png_ptr->background_gamma,
                       png_ptr->screen_gamma);
                   break;
                default:
                   png_error(png_ptr, "invalid background gamma type");
+            }
+            g_sig = png_gamma_significant(g);
+            gs_sig = png_gamma_significant(gs);
+            if (g_sig)
-            png_ptr->background_1.gray = png_gamma_correct(png_ptr,
+               png_ptr->background_1.gray = png_gamma_correct(png_ptr,
-                png_ptr->background.gray, g);
+                   png_ptr->background.gray, g);
+            if (gs_sig)
-            png_ptr->background.gray = png_gamma_correct(png_ptr,
+               png_ptr->background.gray = png_gamma_correct(png_ptr,
-                png_ptr->background.gray, gs);
+                   png_ptr->background.gray, gs);
             if ((png_ptr->background.red != png_ptr->background.green) ||
                 (png_ptr->background.red != png_ptr->background.blue) ||
                 (png_ptr->background.red != png_ptr->background.gray))
+            {
                /* RGB or RGBA with color background */
-               png_ptr->background_1.red = png_gamma_correct(png_ptr,
+               if (g_sig)
+               {
+                  png_ptr->background_1.red = png_gamma_correct(png_ptr,
-                   png_ptr->background.red, g);
+                      png_ptr->background.red, g);
-               png_ptr->background_1.green = png_gamma_correct(png_ptr,
+                  png_ptr->background_1.green = png_gamma_correct(png_ptr,
-                   png_ptr->background.green, g);
+                      png_ptr->background.green, g);
-               png_ptr->background_1.blue = png_gamma_correct(png_ptr,
+                  png_ptr->background_1.blue = png_gamma_correct(png_ptr,
-                   png_ptr->background.blue, g);
+                      png_ptr->background.blue, g);
+               }
+               if (gs_sig)
+               {
-               png_ptr->background.red = png_gamma_correct(png_ptr,
+                  png_ptr->background.red = png_gamma_correct(png_ptr,
-                   png_ptr->background.red, gs);
+                      png_ptr->background.red, gs);
-               png_ptr->background.green = png_gamma_correct(png_ptr,
+                  png_ptr->background.green = png_gamma_correct(png_ptr,
-                   png_ptr->background.green, gs);
+                      png_ptr->background.green, gs);
-               png_ptr->background.blue = png_gamma_correct(png_ptr,
+                  png_ptr->background.blue = png_gamma_correct(png_ptr,
-                   png_ptr->background.blue, gs);
+                      png_ptr->background.blue, gs);
+               }
+            }
             else
+            {
                /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
                png_ptr->background_1.red = png_ptr->background_1.green
                    = png_ptr->background_1.blue = png_ptr->background_1.gray;
                png_ptr->background.red = png_ptr->background.green
                    = png_ptr->background.blue = png_ptr->background.gray;
+            }
+            /* The background is now in screen gamma: */
+            png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
+         } /* color_type != PNG_COLOR_TYPE_PALETTE */
-      }
+      }/* png_ptr->transformations & PNG_BACKGROUND */
       else
       /* Transformation does not include PNG_BACKGROUND */
 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
-      if (color_type == PNG_COLOR_TYPE_PALETTE)
+      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
-      {
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+         /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
+         && ((png_ptr->transformations & PNG_EXPAND) == 0 ||
+         (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
+#endif
+         )
+      {
          png_colorp palette = png_ptr->palette;
          int num_palette = png_ptr->num_palette;
          int i;
+         /* NOTE: there are other transformations that should probably be in
+          * here too.
+          */
          for (i = 0; i < num_palette; i++)
+         {
             palette[i].red = png_ptr->gamma_table[palette[i].red];
             palette[i].green = png_ptr->gamma_table[palette[i].green];
             palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+         }
          /* Done the gamma correction. */
          png_ptr->transformations &= ~PNG_GAMMA;
       } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
    }
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
    else
 #endif
 #endif /* PNG_READ_GAMMA_SUPPORTED */
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
-   /* No GAMMA transformation */
+   /* No GAMMA transformation (see the hanging else 4 lines above) */
-   if ((png_ptr->transformations & PNG_BACKGROUND) &&
+   if ((png_ptr->transformations & PNG_COMPOSE) &&
-       (color_type == PNG_COLOR_TYPE_PALETTE))
+       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
    {
       int i;
       int istop = (int)png_ptr->num_trans;
       png_color back;
       png_colorp palette = png_ptr->palette;
       back.red   = (png_byte)png_ptr->background.red;
       back.green = (png_byte)png_ptr->background.green;
       back.blue  = (png_byte)png_ptr->background.blue;
       for (i = 0; i < istop; i++)
+      {
          if (png_ptr->trans_alpha[i] == 0)
+         {
             palette[i] = back;
+         }
          else if (png_ptr->trans_alpha[i] != 0xff)
+         {
             /* The png_composite() macro is defined in png.h */
             png_composite(palette[i].red, palette[i].red,
                 png_ptr->trans_alpha[i], back.red);
             png_composite(palette[i].green, palette[i].green,
                 png_ptr->trans_alpha[i], back.green);
             png_composite(palette[i].blue, palette[i].blue,
                 png_ptr->trans_alpha[i], back.blue);
+         }
+      }
-      /* Handled alpha, still need to strip the channel. */
-      png_ptr->transformations &= ~PNG_BACKGROUND;
+      png_ptr->transformations &= ~PNG_COMPOSE;
-      png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
+   }
 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
 #ifdef PNG_READ_SHIFT_SUPPORTED
    if ((png_ptr->transformations & PNG_SHIFT) &&
-       (color_type == PNG_COLOR_TYPE_PALETTE))
+      !(png_ptr->transformations & PNG_EXPAND) &&
+       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
    {
-      png_uint_16 i;
+      int i;
-      png_uint_16 istop = png_ptr->num_palette;
+      int istop = png_ptr->num_palette;
-      int sr = 8 - png_ptr->sig_bit.red;
+      int shift = 8 - png_ptr->sig_bit.red;
-      int sg = 8 - png_ptr->sig_bit.green;
-      int sb = 8 - png_ptr->sig_bit.blue;
-      if (sr < 0 || sr > 8)
+      png_ptr->transformations &= ~PNG_SHIFT;
-         sr = 0;
+      /* significant bits can be in the range 1 to 7 for a meaninful result, if
+       * the number of significant bits is 0 then no shift is done (this is an
+       * error condition which is silently ignored.)
+       */
+      if (shift > 0 && shift < 8)
-      if (sg < 0 || sg > 8)
+         for (i=0; i
+         {
-         sg = 0;
+            int component = png_ptr->palette[i].red;
+            component >>= shift;
+            png_ptr->palette[i].red = (png_byte)component;
+         }
-      if (sb < 0 || sb > 8)
+      shift = 8 - png_ptr->sig_bit.green;
+      if (shift > 0 && shift < 8)
+         for (i=0; i
+         {
+            int component = png_ptr->palette[i].green;
+            component >>= shift;
+            png_ptr->palette[i].green = (png_byte)component;
+         }
-         sb = 0;
+      shift = 8 - png_ptr->sig_bit.blue;
+      if (shift > 0 && shift < 8)
+         for (i=0; i
-      for (i = 0; i < istop; i++)
+         {
-      {
+            int component = png_ptr->palette[i].blue;
          png_ptr->palette[i].red >>= sr;
-         png_ptr->palette[i].green >>= sg;
+            component >>= shift;
-         png_ptr->palette[i].blue >>= sb;
+            png_ptr->palette[i].blue = (png_byte)component;
+         }
+   }
 #endif  /* PNG_READ_SHIFT_SUPPORTED */
+}
 #if !defined(PNG_READ_GAMMA_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED) \
- && !defined(PNG_READ_BACKGROUND_SUPPORTED)
-   if (png_ptr)
-      return;
-#endif
-}
 /* Modify the info structure to reflect the transformations.  The
  * info should be updated so a PNG file could be written with it,
  * assuming the transformations result in valid PNG data.
  */
 void /* PRIVATE */
-png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
+png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
 {
    png_debug(1, "in png_read_transform_info");
 #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
+   {
       if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      {
-         if (png_ptr->num_trans &&
+         /* This check must match what actually happens in
-             (png_ptr->transformations & PNG_EXPAND_tRNS))
+          * png_do_expand_palette; if it ever checks the tRNS chunk to see if
+          * it is all opaque we must do the same (at present it does not.)
+          */
+         if (png_ptr->num_trans > 0)
             info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
          else
             info_ptr->color_type = PNG_COLOR_TYPE_RGB;
          info_ptr->bit_depth = 8;
          info_ptr->num_trans = 0;
+      }
       else
+      {
          if (png_ptr->num_trans)
+         {
             if (png_ptr->transformations & PNG_EXPAND_tRNS)
                info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+         }
          if (info_ptr->bit_depth < 8)
             info_ptr->bit_depth = 8;
          info_ptr->num_trans = 0;
+      }
+   }
 #endif
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-   if (png_ptr->transformations & PNG_BACKGROUND)
+   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
-   {
-      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+   /* The following is almost certainly wrong unless the background value is in
-          ~PNG_COLOR_MASK_ALPHA);
+    * the screen space!
+    */
-      info_ptr->num_trans = 0;
+   if (png_ptr->transformations & PNG_COMPOSE)
       info_ptr->background = png_ptr->background;
-   }
 #endif
 #ifdef PNG_READ_GAMMA_SUPPORTED
-   if (png_ptr->transformations & PNG_GAMMA)
+   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
-   {
+    * however it seems that the code in png_init_read_transformations, which has
+    * been called before this from png_read_update_info->png_read_start_row
+    * sometimes does the gamma transform and cancels the flag.
+    *
-      info_ptr->gamma = png_ptr->gamma;
+    * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
+    * the screen_gamma value.  The following probably results in weirdness if
+    * the info_ptr is used by the app after the rows have been read.
-   }
+    */
-#endif
+   info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
+#endif
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+   if (info_ptr->bit_depth == 16)
+   {
-#ifdef PNG_READ_16BIT_SUPPORTED
+#  ifdef PNG_READ_16BIT_SUPPORTED
+#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-   if ((png_ptr->transformations & PNG_16_TO_8) && (info_ptr->bit_depth == 16))
+         if (png_ptr->transformations & PNG_SCALE_16_TO_8)
-      info_ptr->bit_depth = 8;
+            info_ptr->bit_depth = 8;
+#     endif
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+         if (png_ptr->transformations & PNG_16_TO_8)
+            info_ptr->bit_depth = 8;
+#     endif
-#else
+#  else
-   /* Force chopping 16-bit input down to 8 */
+      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
+       * the app program can chose if both APIs are available by setting the
-   if (info_ptr->bit_depth == 16)
+       * correct scaling to use.
-   {
+       */
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+         /* For compatibility with previous versions use the strip method by
+          * default.  This code works because if PNG_SCALE_16_TO_8 is already
+          * set the code below will do that in preference to the chop.
+          */
-      png_ptr->transformations |=PNG_16_TO_8;
+         png_ptr->transformations |= PNG_16_TO_8;
-      info_ptr->bit_depth = 8;
+         info_ptr->bit_depth = 8;
-   }
+#     else
+#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+            png_ptr->transformations |= PNG_SCALE_16_TO_8;
+            info_ptr->bit_depth = 8;
+#        else
+            CONFIGURATION ERROR: you must enable at least one 16 to 8 method
-#endif
+#        endif
-#endif
+#    endif
+#endif /* !READ_16BIT_SUPPORTED */
+   }
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    if (png_ptr->transformations & PNG_GRAY_TO_RGB)
-      info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
+      info_ptr->color_type = (png_byte)(info_ptr->color_type |
-#endif
+         PNG_COLOR_MASK_COLOR);
+#endif
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-      info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_COLOR);
 #endif
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
    if (png_ptr->transformations & PNG_QUANTIZE)
+   {
       if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
           (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
           png_ptr->palette_lookup && info_ptr->bit_depth == 8)
+      {
          info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
+      }
+   }
 #endif
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+   if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&
+      info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
+   {
+      info_ptr->bit_depth = 16;
+   }
+#endif
 #ifdef PNG_READ_PACK_SUPPORTED
    if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
       info_ptr->bit_depth = 8;
 #endif
    if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       info_ptr->channels = 1;
    else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
       info_ptr->channels = 3;
    else
       info_ptr->channels = 1;
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-   if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
+   if (png_ptr->transformations & PNG_STRIP_ALPHA)
-      info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
+   {
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_ALPHA);
-#endif
+      info_ptr->num_trans = 0;
+   }
+#endif
    if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
       info_ptr->channels++;
 #ifdef PNG_READ_FILLER_SUPPORTED
    /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
    if ((png_ptr->transformations & PNG_FILLER) &&
        ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
        (info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
+   {
       info_ptr->channels++;
       /* If adding a true alpha channel not just filler */
       if (png_ptr->transformations & PNG_ADD_ALPHA)
          info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+   }
 #endif
 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
+   {
       if (info_ptr->bit_depth < png_ptr->user_transform_depth)
          info_ptr->bit_depth = png_ptr->user_transform_depth;
       if (info_ptr->channels < png_ptr->user_transform_channels)
          info_ptr->channels = png_ptr->user_transform_channels;
+   }
 #endif
    info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
        info_ptr->bit_depth);
    info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
+   /* Adding in 1.5.4: cache the above value in png_struct so that we can later
+    * check in png_rowbytes that the user buffer won't get overwritten.  Note
+    * that the field is not always set - if png_read_update_info isn't called
+    * the application has to either not do any transforms or get the calculation
+    * right itself.
+    */
+   png_ptr->info_rowbytes = info_ptr->rowbytes;
 #ifndef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr)
       return;
 #endif
+}
 /* Transform the row.  The order of transformations is significant,
  * and is very touchy.  If you add a transformation, take care to
  * decide how it fits in with the other transformations here.
  */
 void /* PRIVATE */
-png_do_read_transformations(png_structp png_ptr)
+png_do_read_transformations(png_structrp png_ptr, png_row_infop row_info)
 {
    png_debug(1, "in png_do_read_transformations");
    if (png_ptr->row_buf == NULL)
+   {
-#ifdef PNG_CONSOLE_IO_SUPPORTED
+      /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
-      char msg[50];
-      png_snprintf2(msg, 50,
-          "NULL row buffer for row %ld, pass %d", (long)png_ptr->row_number,
+       * error is incredibly rare and incredibly easy to debug without this
-          png_ptr->pass);
+       * information.
-      png_error(png_ptr, msg);
+       */
-#else
       png_error(png_ptr, "NULL row buffer");
 #endif
-   }
 #ifdef PNG_WARN_UNINITIALIZED_ROW
+   /* The following is debugging; prior to 1.5.4 the code was never compiled in;
+    * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
+    * PNG_WARN_UNINITIALIZED_ROW removed.  In 1.6 the new flag is set only for
+    * all transformations, however in practice the ROW_INIT always gets done on
+    * demand, if necessary.
+    */
+   if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&
-   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
+      !(png_ptr->flags & PNG_FLAG_ROW_INIT))
-      /* Application has failed to call either png_read_start_image()
+   {
+      /* Application has failed to call either png_read_start_image() or
-       * or png_read_update_info() after setting transforms that expand
+       * png_read_update_info() after setting transforms that expand pixels.
-       * pixels.  This check added to libpng-1.2.19
+       * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
        */
-#if (PNG_WARN_UNINITIALIZED_ROW==1)
+      png_error(png_ptr, "Uninitialized row");
-      png_error(png_ptr, "Uninitialized row");
 #else
-      png_warning(png_ptr, "Uninitialized row");
-#endif
-#endif
 #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
+   {
-      if (png_ptr->row_info.color_type == PNG_COLOR_TYPE_PALETTE)
+      if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
       {
-         png_do_expand_palette(&(png_ptr->row_info), png_ptr->row_buf + 1,
+         png_do_expand_palette(row_info, png_ptr->row_buf + 1,
              png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
+      }
       else
+      else
+      {
          if (png_ptr->num_trans &&
              (png_ptr->transformations & PNG_EXPAND_tRNS))
-            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
+            png_do_expand(row_info, png_ptr->row_buf + 1,
                 &(png_ptr->trans_color));
          else
+         else
-            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
+            png_do_expand(row_info, png_ptr->row_buf + 1,
                 NULL);
+      }
+   }
 #endif
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-   if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
-      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      !(png_ptr->transformations & PNG_COMPOSE) &&
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
-          PNG_FLAG_FILLER_AFTER | (png_ptr->flags & PNG_FLAG_STRIP_ALPHA));
+/* at_start == false, because SWAP_ALPHA happens later */);
 #endif
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+   {
       int rgb_error =
-          png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info),
+          png_do_rgb_to_gray(png_ptr, row_info,
               png_ptr->row_buf + 1);
       if (rgb_error)
+      {
          png_ptr->rgb_to_gray_status=1;
          if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
              PNG_RGB_TO_GRAY_WARN)
             png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
          if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
              PNG_RGB_TO_GRAY_ERR)
             png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
+      }
+   }
 #endif
 /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
+ *
  *   In most cases, the "simple transparency" should be done prior to doing
  *   gray-to-RGB, or you will have to test 3x as many bytes to check if a
  *   pixel is transparent.  You would also need to make sure that the
  *   transparency information is upgraded to RGB.
+ *
  *   To summarize, the current flow is:
  *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
  *                                   with background "in place" if transparent,
  *                                   convert to RGB if necessary
  *   - Gray + alpha -> composite with gray background and remove alpha bytes,
  *                                   convert to RGB if necessary
+ *
  *   To support RGB backgrounds for gray images we need:
  *   - Gray + simple transparency -> convert to RGB + simple transparency,
  *                                   compare 3 or 6 bytes and composite with
  *                                   background "in place" if transparent
  *                                   (3x compare/pixel compared to doing
  *                                   composite with gray bkgrnd)
  *   - Gray + alpha -> convert to RGB + alpha, composite with background and
  *                                   remove alpha bytes (3x float
  *                                   operations/pixel compared with composite
  *                                   on gray background)
+ *
  *  Greg's change will do this.  The reason it wasn't done before is for
  *  performance, as this increases the per-pixel operations.  If we would check
  *  in advance if the background was gray or RGB, and position the gray-to-RGB
  *  transform appropriately, then it would save a lot of work/time.
  */
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* If gray -> RGB, do so now only if background is non-gray; else do later
     * for performance reasons
     */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
 #endif
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-   if ((png_ptr->transformations & PNG_BACKGROUND) &&
-       ((png_ptr->num_trans != 0) ||
+   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
-       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)))
+   if (png_ptr->transformations & PNG_COMPOSE)
-      png_do_background(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
-          &(png_ptr->trans_color), &(png_ptr->background)
-#ifdef PNG_READ_GAMMA_SUPPORTED
-          , &(png_ptr->background_1),
-          png_ptr->gamma_table, png_ptr->gamma_from_1,
-          png_ptr->gamma_to_1, png_ptr->gamma_16_table,
-          png_ptr->gamma_16_from_1, png_ptr->gamma_16_to_1,
-          png_ptr->gamma_shift
-#endif
-          );
 #endif
 #ifdef PNG_READ_GAMMA_SUPPORTED
    if ((png_ptr->transformations & PNG_GAMMA) &&
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+      /* Because RGB_TO_GRAY does the gamma transform. */
+      !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
+#endif
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-       !((png_ptr->transformations & PNG_BACKGROUND) &&
+   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+      /* Because PNG_COMPOSE does the gamma transform if there is something to
+       * do (if there is an alpha channel or transparency.)
+       */
+       !((png_ptr->transformations & PNG_COMPOSE) &&
        ((png_ptr->num_trans != 0) ||
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
 #endif
-       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
+      /* Because png_init_read_transformations transforms the palette, unless
+       * RGB_TO_GRAY will do the transform.
+       */
+       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
-      png_do_gamma(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+      (png_ptr->transformations & PNG_COMPOSE) &&
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
-          png_ptr->gamma_table, png_ptr->gamma_16_table,
+/* at_start == false, because SWAP_ALPHA happens later */);
+#endif
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+   if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
+      (row_info->color_type & PNG_COLOR_MASK_ALPHA))
+      png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+   if (png_ptr->transformations & PNG_SCALE_16_TO_8)
-          png_ptr->gamma_shift);
+      png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
 #endif
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+   /* There is no harm in doing both of these because only one has any effect,
+    * by putting the 'scale' option first if the app asks for scale (either by
+    * calling the API or in a TRANSFORM flag) this is what happens.
+    */
    if (png_ptr->transformations & PNG_16_TO_8)
-      png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_chop(row_info, png_ptr->row_buf + 1);
 #endif
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
    if (png_ptr->transformations & PNG_QUANTIZE)
+   {
-      png_do_quantize(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_quantize(row_info, png_ptr->row_buf + 1,
           png_ptr->palette_lookup, png_ptr->quantize_index);
-      if (png_ptr->row_info.rowbytes == 0)
+      if (row_info->rowbytes == 0)
          png_error(png_ptr, "png_do_quantize returned rowbytes=0");
+   }
 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+   /* Do the expansion now, after all the arithmetic has been done.  Notice
+    * that previous transformations can handle the PNG_EXPAND_16 flag if this
+    * is efficient (particularly true in the case of gamma correction, where
+    * better accuracy results faster!)
+    */
+   if (png_ptr->transformations & PNG_EXPAND_16)
+      png_do_expand_16(row_info, png_ptr->row_buf + 1);
+#endif
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+   /* NOTE: moved here in 1.5.4 (from much later in this list.) */
+   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
+#endif
 #ifdef PNG_READ_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
-      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_invert(row_info, png_ptr->row_buf + 1);
 #endif
 #ifdef PNG_READ_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
-      png_do_unshift(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_unshift(row_info, png_ptr->row_buf + 1,
           &(png_ptr->shift));
 #endif
 #ifdef PNG_READ_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
-      png_do_unpack(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_unpack(row_info, png_ptr->row_buf + 1);
 #endif
+#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
+   /* Added at libpng-1.5.10 */
+   if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
+       png_ptr->num_palette_max >= 0)
+      png_do_check_palette_indexes(png_ptr, row_info);
+#endif
 #ifdef PNG_READ_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
-      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_bgr(row_info, png_ptr->row_buf + 1);
 #endif
 #ifdef PNG_READ_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_packswap(row_info, png_ptr->row_buf + 1);
 #endif
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   /* If gray -> RGB, do so now only if we did not do so above */
-   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
-       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
-#endif
 #ifdef PNG_READ_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
-      png_do_read_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_read_filler(row_info, png_ptr->row_buf + 1,
           (png_uint_32)png_ptr->filler, png_ptr->flags);
 #endif
 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_ALPHA)
-      png_do_read_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
-      png_do_read_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 #ifdef PNG_READ_16BIT_SUPPORTED
 #ifdef PNG_READ_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
-      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_swap(row_info, png_ptr->row_buf + 1);
 #endif
 #endif
 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
+    {
       if (png_ptr->read_user_transform_fn != NULL)
          (*(png_ptr->read_user_transform_fn)) /* User read transform function */
-             (png_ptr,                    /* png_ptr */
+             (png_ptr,     /* png_ptr */
-             &(png_ptr->row_info),     /* row_info: */
+             row_info,     /* row_info: */
                 /*  png_uint_32 width;       width of row */
                 /*  png_size_t rowbytes;     number of bytes in row */
                 /*  png_byte color_type;     color type of pixels */
                 /*  png_byte bit_depth;      bit depth of samples */
                 /*  png_byte channels;       number of channels (1-4) */
                 /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
              png_ptr->row_buf + 1);    /* start of pixel data for row */
 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
       if (png_ptr->user_transform_depth)
-         png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
+         row_info->bit_depth = png_ptr->user_transform_depth;
       if (png_ptr->user_transform_channels)
-         png_ptr->row_info.channels = png_ptr->user_transform_channels;
+         row_info->channels = png_ptr->user_transform_channels;
 #endif
-      png_ptr->row_info.pixel_depth = (png_byte)(png_ptr->row_info.bit_depth *
+      row_info->pixel_depth = (png_byte)(row_info->bit_depth *
-          png_ptr->row_info.channels);
+          row_info->channels);
-      png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
-          png_ptr->row_info.width);
+      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
+   }
-#endif
 #endif
+}
 #ifdef PNG_READ_PACK_SUPPORTED
 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
  * without changing the actual values.  Thus, if you had a row with
  * a bit depth of 1, you would end up with bytes that only contained
  * the numbers 0 or 1.  If you would rather they contain 0 and 255, use
  * png_do_shift() after this.
  */
 void /* PRIVATE */
 png_do_unpack(png_row_infop row_info, png_bytep row)
+{
    png_debug(1, "in png_do_unpack");
    if (row_info->bit_depth < 8)
+   {
       png_uint_32 i;
       png_uint_32 row_width=row_info->width;
       switch (row_info->bit_depth)
+      {
          case 1:
+         {
             png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
             png_bytep dp = row + (png_size_t)row_width - 1;
             png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
             for (i = 0; i < row_width; i++)
+            {
                *dp = (png_byte)((*sp >> shift) & 0x01);
                if (shift == 7)
+               {
                   shift = 0;
                   sp--;
+               }
                else
                   shift++;
                dp--;
+            }
             break;
+         }
          case 2:
+         {
             png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
             png_bytep dp = row + (png_size_t)row_width - 1;
             png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
             for (i = 0; i < row_width; i++)
+            {
                *dp = (png_byte)((*sp >> shift) & 0x03);
                if (shift == 6)
+               {
                   shift = 0;
                   sp--;
+               }
                else
                   shift += 2;
                dp--;
+            }
             break;
+         }
          case 4:
+         {
             png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
             png_bytep dp = row + (png_size_t)row_width - 1;
             png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
             for (i = 0; i < row_width; i++)
+            {
                *dp = (png_byte)((*sp >> shift) & 0x0f);
                if (shift == 4)
+               {
                   shift = 0;
                   sp--;
+               }
                else
                   shift = 4;
                dp--;
+            }
             break;
+         }
          default:
             break;
+      }
       row_info->bit_depth = 8;
       row_info->pixel_depth = (png_byte)(8 * row_info->channels);
       row_info->rowbytes = row_width * row_info->channels;
+   }
+}
 #endif
 #ifdef PNG_READ_SHIFT_SUPPORTED
 /* Reverse the effects of png_do_shift.  This routine merely shifts the
  * pixels back to their significant bits values.  Thus, if you have
  * a row of bit depth 8, but only 5 are significant, this will shift
  * the values back to 0 through 31.
  */
 void /* PRIVATE */
 png_do_unshift(png_row_infop row_info, png_bytep row,
     png_const_color_8p sig_bits)
+{
-   png_debug(1, "in png_do_unshift");
+   int color_type;
+   png_debug(1, "in png_do_unshift");
+   /* The palette case has already been handled in the _init routine. */
+   color_type = row_info->color_type;
-   if (
-       row_info->color_type != PNG_COLOR_TYPE_PALETTE)
+   if (color_type != PNG_COLOR_TYPE_PALETTE)
+   {
       int shift[4];
       int channels = 0;
-      int c;
+      int bit_depth = row_info->bit_depth;
-      png_uint_16 value = 0;
-      png_uint_32 row_width = row_info->width;
-      if (row_info->color_type & PNG_COLOR_MASK_COLOR)
+      if (color_type & PNG_COLOR_MASK_COLOR)
+      {
-         shift[channels++] = row_info->bit_depth - sig_bits->red;
+         shift[channels++] = bit_depth - sig_bits->red;
-         shift[channels++] = row_info->bit_depth - sig_bits->green;
+         shift[channels++] = bit_depth - sig_bits->green;
-         shift[channels++] = row_info->bit_depth - sig_bits->blue;
+         shift[channels++] = bit_depth - sig_bits->blue;
+      }
       else
+      {
-         shift[channels++] = row_info->bit_depth - sig_bits->gray;
+         shift[channels++] = bit_depth - sig_bits->gray;
       }
-      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+      if (color_type & PNG_COLOR_MASK_ALPHA)
+      {
-         shift[channels++] = row_info->bit_depth - sig_bits->alpha;
+         shift[channels++] = bit_depth - sig_bits->alpha;
+      }
       for (c = 0; c < channels; c++)
       {
+         int c, have_shift;
+         for (c = have_shift = 0; c < channels; ++c)
+         {
+            /* A shift of more than the bit depth is an error condition but it
+             * gets ignored here.
+             */
-         if (shift[c] <= 0)
+            if (shift[c] <= 0 || shift[c] >= bit_depth)
-            shift[c] = 0;
+               shift[c] = 0;
-         else
+            else
-            value = 1;
+               have_shift = 1;
-      }
+         }
-      if (!value)
+         if (!have_shift)
-         return;
+            return;
+      }
-      switch (row_info->bit_depth)
+      switch (bit_depth)
+      {
+         default:
+         /* Must be 1bpp gray: should not be here! */
-         default:
+            /* NOTREACHED */
             break;
          case 2:
          /* Must be 2bpp gray */
+         /* assert(channels == 1 && shift[0] == 1) */
+         {
-            png_bytep bp;
+            png_bytep bp = row;
-            png_size_t i;
+            png_bytep bp_end = bp + row_info->rowbytes;
-            png_size_t istop = row_info->rowbytes;
-            for (bp = row, i = 0; i < istop; i++)
+            while (bp < bp_end)
+            {
-               *bp >>= 1;
+               int b = (*bp >> 1) & 0x55;
-               *bp++ &= 0x55;
+               *bp++ = (png_byte)b;
+            }
             break;
+         }
          case 4:
          /* Must be 4bpp gray */
+         /* assert(channels == 1) */
+         {
             png_bytep bp = row;
-            png_size_t i;
+            png_bytep bp_end = bp + row_info->rowbytes;
-            png_size_t istop = row_info->rowbytes;
-            png_byte mask = (png_byte)((((int)0xf0 >> shift[0]) & (int)0xf0) |
+            int gray_shift = shift[0];
-                (png_byte)((int)0xf >> shift[0]));
+            int mask =  0xf >> gray_shift;
+            mask |= mask << 4;
-            for (i = 0; i < istop; i++)
+            while (bp < bp_end)
+            {
-               *bp >>= shift[0];
+               int b = (*bp >> gray_shift) & mask;
-               *bp++ &= mask;
+               *bp++ = (png_byte)b;
+            }
             break;
+         }
          case 8:
          /* Single byte components, G, GA, RGB, RGBA */
+         {
             png_bytep bp = row;
-            png_uint_32 i;
+            png_bytep bp_end = bp + row_info->rowbytes;
-            png_uint_32 istop = row_width * channels;
+            int channel = 0;
-            for (i = 0; i < istop; i++)
+            while (bp < bp_end)
+            {
-               *bp++ >>= shift[i%channels];
+               int b = *bp >> shift[channel];
+               if (++channel >= channels)
+                  channel = 0;
+               *bp++ = (png_byte)b;
+            }
             break;
+         }
 #ifdef PNG_READ_16BIT_SUPPORTED
          case 16:
          /* Double byte components, G, GA, RGB, RGBA */
+         {
             png_bytep bp = row;
-            png_uint_32 i;
+            png_bytep bp_end = bp + row_info->rowbytes;
-            png_uint_32 istop = channels * row_width;
+            int channel = 0;
-            for (i = 0; i < istop; i++)
+            while (bp < bp_end)
+            {
-               value = (png_uint_16)((*bp << 8) + *(bp + 1));
+               int value = (bp[0] << 8) + bp[1];
-               value >>= shift[i%channels];
+               value >>= shift[channel];
+               if (++channel >= channels)
+                  channel = 0;
                *bp++ = (png_byte)(value >> 8);
                *bp++ = (png_byte)(value & 0xff);
+            }
             break;
+         }
 #endif
+      }
+   }
+}
 #endif
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-/* Chop rows of bit depth 16 down to 8 */
+/* Scale rows of bit depth 16 down to 8 accurately */
 void /* PRIVATE */
-png_do_chop(png_row_infop row_info, png_bytep row)
+png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
+{
-   png_debug(1, "in png_do_chop");
+   png_debug(1, "in png_do_scale_16_to_8");
    if (row_info->bit_depth == 16)
+   {
-      png_bytep sp = row;
+      png_bytep sp = row; /* source */
-      png_bytep dp = row;
+      png_bytep dp = row; /* destination */
-      png_uint_32 i;
+      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
-      png_uint_32 istop = row_info->width * row_info->channels;
-      for (i = 0; i
+      while (sp < ep)
       {
-#ifdef PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
+         /* The input is an array of 16 bit components, these must be scaled to
-      /* This does a more accurate scaling of the 16-bit color
+          * 8 bits each.  For a 16 bit value V the required value (from the PNG
-       * value, rather than a simple low-byte truncation.
+          * specification) is:
-       *
+          *
+          *    (V * 255) / 65535
+          *
-       * What the ideal calculation should be:
+          * This reduces to round(V / 257), or floor((V + 128.5)/257)
-       *   *dp = (((((png_uint_32)(*sp) << 8) |
-       *          (png_uint_32)(*(sp + 1))) * 255 + 127)
-       *          / (png_uint_32)65535L;
+          *
-       *
-       * GRR: no, I think this is what it really should be:
+          * Represent V as the two byte value vhi.vlo.  Make a guess that the
-       *   *dp = (((((png_uint_32)(*sp) << 8) |
+          * result is the top byte of V, vhi, then the correction to this value
-       *           (png_uint_32)(*(sp + 1))) + 128L)
-       *           / (png_uint_32)257L;
+          * is:
-       *
+          *
-       * GRR: here's the exact calculation with shifts:
+          *    error = floor(((V-vhi.vhi) + 128.5) / 257)
-       *   temp = (((png_uint_32)(*sp) << 8) |
-       *           (png_uint_32)(*(sp + 1))) + 128L;
+          *          = floor(((vlo-vhi) + 128.5) / 257)
-       *   *dp = (temp - (temp >> 8)) >> 8;
+          *
-       *
-       * Approximate calculation with shift/add instead of multiply/divide:
+          * This can be approximated using integer arithmetic (and a signed
-       *   *dp = ((((png_uint_32)(*sp) << 8) |
+          * shift):
-       *          (png_uint_32)((int)(*(sp + 1)) - *sp)) + 128) >> 8;
+          *
-       *
-       * What we actually do to avoid extra shifting and conversion:
+          *    error = (vlo-vhi+128) >> 8;
+          *
+          * The approximate differs from the exact answer only when (vlo-vhi) is
+          * 128; it then gives a correction of +1 when the exact correction is
-       */
+          * 0.  This gives 128 errors.  The exact answer (correct for all 16 bit
+          * input values) is:
+          *
+          *    error = (vlo-vhi+128)*65535 >> 24;
+          *
+          * An alternative arithmetic calculation which also gives no errors is:
+          *
+          *    (V * 255 + 32895) >> 16
+          */
+         png_int_32 tmp = *sp++; /* must be signed! */
-         *dp = *sp + ((((int)(*(sp + 1)) - *sp) > 128) ? 1 : 0);
+         tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
+         *dp++ = (png_byte)tmp;
-#else
+      }
-       /* Simply discard the low order byte */
+      row_info->bit_depth = 8;
-         *dp = *sp;
+      row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+      row_info->rowbytes = row_info->width * row_info->channels;
+   }
+}
 #endif
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+void /* PRIVATE */
+/* Simply discard the low byte.  This was the default behavior prior
+ * to libpng-1.5.4.
+ */
+png_do_chop(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_chop");
+   if (row_info->bit_depth == 16)
+   {
+      png_bytep sp = row; /* source */
+      png_bytep dp = row; /* destination */
+      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
+      while (sp < ep)
+      {
+         *dp++ = *sp;
+         sp += 2; /* skip low byte */
+      }
       row_info->bit_depth = 8;
       row_info->pixel_depth = (png_byte)(8 * row_info->channels);
       row_info->rowbytes = row_info->width * row_info->channels;
+   }
+}
 #endif
 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
 void /* PRIVATE */
 png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
+{
    png_debug(1, "in png_do_read_swap_alpha");
+   {
       png_uint_32 row_width = row_info->width;
       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+      {
          /* This converts from RGBA to ARGB */
          if (row_info->bit_depth == 8)
+         {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save;
             png_uint_32 i;
             for (i = 0; i < row_width; i++)
+            {
                save = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save;
+            }
+         }
 #ifdef PNG_READ_16BIT_SUPPORTED
          /* This converts from RRGGBBAA to AARRGGBB */
          else
+         {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save[2];
             png_uint_32 i;
             for (i = 0; i < row_width; i++)
+            {
                save[0] = *(--sp);
                save[1] = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save[0];
                *(--dp) = save[1];
+            }
+         }
 #endif
+      }
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
          /* This converts from GA to AG */
          if (row_info->bit_depth == 8)
+         {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save;
             png_uint_32 i;
             for (i = 0; i < row_width; i++)
+            {
                save = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save;
+            }
+         }
 #ifdef PNG_READ_16BIT_SUPPORTED
          /* This converts from GGAA to AAGG */
          else
+         {
             png_bytep sp = row + row_info->rowbytes;
             png_bytep dp = sp;
             png_byte save[2];
             png_uint_32 i;
             for (i = 0; i < row_width; i++)
+            {
                save[0] = *(--sp);
                save[1] = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = save[0];
                *(--dp) = save[1];
+            }
+         }
 #endif
+      }
+   }
+}
 #endif
 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
 void /* PRIVATE */
 png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
+{
    png_uint_32 row_width;
    png_debug(1, "in png_do_read_invert_alpha");
    row_width = row_info->width;
    if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+   {
       if (row_info->bit_depth == 8)
+      {
          /* This inverts the alpha channel in RGBA */
          png_bytep sp = row + row_info->rowbytes;
          png_bytep dp = sp;
          png_uint_32 i;
          for (i = 0; i < row_width; i++)
+         {
             *(--dp) = (png_byte)(255 - *(--sp));
 /*          This does nothing:
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             We can replace it with:
 */
             sp-=3;
             dp=sp;
+         }
+      }
 #ifdef PNG_READ_16BIT_SUPPORTED
       /* This inverts the alpha channel in RRGGBBAA */
       else
+      {
          png_bytep sp = row + row_info->rowbytes;
          png_bytep dp = sp;
          png_uint_32 i;
          for (i = 0; i < row_width; i++)
+         {
             *(--dp) = (png_byte)(255 - *(--sp));
             *(--dp) = (png_byte)(255 - *(--sp));
 /*          This does nothing:
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
             We can replace it with:
 */
             sp-=6;
             dp=sp;
+         }
+      }
 #endif
+   }
    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+   {
       if (row_info->bit_depth == 8)
+      {
          /* This inverts the alpha channel in GA */
          png_bytep sp = row + row_info->rowbytes;
          png_bytep dp = sp;
          png_uint_32 i;
          for (i = 0; i < row_width; i++)
+         {
             *(--dp) = (png_byte)(255 - *(--sp));
             *(--dp) = *(--sp);
+         }
+      }
 #ifdef PNG_READ_16BIT_SUPPORTED
       else
+      {
          /* This inverts the alpha channel in GGAA */
          png_bytep sp  = row + row_info->rowbytes;
          png_bytep dp = sp;
          png_uint_32 i;
          for (i = 0; i < row_width; i++)
+         {
             *(--dp) = (png_byte)(255 - *(--sp));
             *(--dp) = (png_byte)(255 - *(--sp));
 /*
             *(--dp) = *(--sp);
             *(--dp) = *(--sp);
 */
             sp-=2;
             dp=sp;
+         }
+      }
 #endif
+   }
+}
 #endif
 #ifdef PNG_READ_FILLER_SUPPORTED
 /* Add filler channel if we have RGB color */
 void /* PRIVATE */
 png_do_read_filler(png_row_infop row_info, png_bytep row,
     png_uint_32 filler, png_uint_32 flags)
+{
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;
 #ifdef PNG_READ_16BIT_SUPPORTED
    png_byte hi_filler = (png_byte)((filler>>8) & 0xff);
 #endif
    png_byte lo_filler = (png_byte)(filler & 0xff);
    png_debug(1, "in png_do_read_filler");
    if (
        row_info->color_type == PNG_COLOR_TYPE_GRAY)
+   {
       if (row_info->bit_depth == 8)
+      {
          if (flags & PNG_FLAG_FILLER_AFTER)
+         {
             /* This changes the data from G to GX */
             png_bytep sp = row + (png_size_t)row_width;
             png_bytep dp =  sp + (png_size_t)row_width;
             for (i = 1; i < row_width; i++)
+            {
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
+            }
             *(--dp) = lo_filler;
             row_info->channels = 2;
             row_info->pixel_depth = 16;
             row_info->rowbytes = row_width * 2;
+         }
          else
+         {
             /* This changes the data from G to XG */
             png_bytep sp = row + (png_size_t)row_width;
             png_bytep dp = sp  + (png_size_t)row_width;
             for (i = 0; i < row_width; i++)
+            {
                *(--dp) = *(--sp);
                *(--dp) = lo_filler;
+            }
             row_info->channels = 2;
             row_info->pixel_depth = 16;
             row_info->rowbytes = row_width * 2;
+         }
+      }
 #ifdef PNG_READ_16BIT_SUPPORTED
       else if (row_info->bit_depth == 16)
+      {
          if (flags & PNG_FLAG_FILLER_AFTER)
+         {
             /* This changes the data from GG to GGXX */
             png_bytep sp = row + (png_size_t)row_width * 2;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 1; i < row_width; i++)
+            {
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
+            }
             *(--dp) = hi_filler;
             *(--dp) = lo_filler;
             row_info->channels = 2;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
+         }
          else
+         {
             /* This changes the data from GG to XXGG */
             png_bytep sp = row + (png_size_t)row_width * 2;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
+            {
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
+            }
             row_info->channels = 2;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
+         }
+      }
 #endif
    } /* COLOR_TYPE == GRAY */
    else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+   {
       if (row_info->bit_depth == 8)
+      {
          if (flags & PNG_FLAG_FILLER_AFTER)
+         {
             /* This changes the data from RGB to RGBX */
             png_bytep sp = row + (png_size_t)row_width * 3;
             png_bytep dp = sp  + (png_size_t)row_width;
             for (i = 1; i < row_width; i++)
+            {
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
+            }
             *(--dp) = lo_filler;
             row_info->channels = 4;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
+         }
          else
+         {
             /* This changes the data from RGB to XRGB */
             png_bytep sp = row + (png_size_t)row_width * 3;
             png_bytep dp = sp + (png_size_t)row_width;
             for (i = 0; i < row_width; i++)
+            {
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = lo_filler;
+            }
             row_info->channels = 4;
             row_info->pixel_depth = 32;
             row_info->rowbytes = row_width * 4;
+         }
+      }
 #ifdef PNG_READ_16BIT_SUPPORTED
       else if (row_info->bit_depth == 16)
+      {
          if (flags & PNG_FLAG_FILLER_AFTER)
+         {
             /* This changes the data from RRGGBB to RRGGBBXX */
             png_bytep sp = row + (png_size_t)row_width * 6;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 1; i < row_width; i++)
+            {
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
+            }
             *(--dp) = hi_filler;
             *(--dp) = lo_filler;
             row_info->channels = 4;
             row_info->pixel_depth = 64;
             row_info->rowbytes = row_width * 8;
+         }
          else
+         {
             /* This changes the data from RRGGBB to XXRRGGBB */
             png_bytep sp = row + (png_size_t)row_width * 6;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
+            {
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = *(--sp);
                *(--dp) = hi_filler;
                *(--dp) = lo_filler;
+            }
             row_info->channels = 4;
             row_info->pixel_depth = 64;
             row_info->rowbytes = row_width * 8;
+         }
+      }
 #endif
    } /* COLOR_TYPE == RGB */
+}
 #endif
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
 /* Expand grayscale files to RGB, with or without alpha */
 void /* PRIVATE */
 png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
+{
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;
    png_debug(1, "in png_do_gray_to_rgb");
    if (row_info->bit_depth >= 8 &&
        !(row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
       if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
+      {
          if (row_info->bit_depth == 8)
+         {
             /* This changes G to RGB */
             png_bytep sp = row + (png_size_t)row_width - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
+            {
                *(dp--) = *sp;
                *(dp--) = *sp;
                *(dp--) = *(sp--);
+            }
+         }
          else
+         {
             /* This changes GG to RRGGBB */
             png_bytep sp = row + (png_size_t)row_width * 2 - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 4;
             for (i = 0; i < row_width; i++)
+            {
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *(sp--);
                *(dp--) = *(sp--);
+            }
+         }
+      }
       else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
          if (row_info->bit_depth == 8)
+         {
             /* This changes GA to RGBA */
             png_bytep sp = row + (png_size_t)row_width * 2 - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 2;
             for (i = 0; i < row_width; i++)
+            {
                *(dp--) = *(sp--);
                *(dp--) = *sp;
                *(dp--) = *sp;
                *(dp--) = *(sp--);
+            }
+         }
          else
+         {
             /* This changes GGAA to RRGGBBAA */
             png_bytep sp = row + (png_size_t)row_width * 4 - 1;
             png_bytep dp = sp  + (png_size_t)row_width * 4;
             for (i = 0; i < row_width; i++)
+            {
                *(dp--) = *(sp--);
                *(dp--) = *(sp--);
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *sp;
                *(dp--) = *(sp - 1);
                *(dp--) = *(sp--);
                *(dp--) = *(sp--);
+            }
+         }
+      }
-      row_info->channels += (png_byte)2;
+      row_info->channels = (png_byte)(row_info->channels + 2);
       row_info->color_type |= PNG_COLOR_MASK_COLOR;
       row_info->pixel_depth = (png_byte)(row_info->channels *
           row_info->bit_depth);
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+   }
+}
 #endif
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 /* Reduce RGB files to grayscale, with or without alpha
- * using the equation given in Poynton's ColorFAQ at
+ * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
- *   (THIS LINK IS DEAD June 2008)
+ *   (THIS LINK IS DEAD June 2008 but
- * New link:
+ * versions dated 1998 through November 2002 have been archived at
- *
+ * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
+ * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
  * Charles Poynton poynton at poynton.com
+ *
  *     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
+ *
- *  We approximate this with
+ *  which can be expressed with integers as
+ *
+ *     Y = (6969 * R + 23434 * G + 2365 * B)/32768
+ *
+ * Poynton's current link (as of January 2003 through July 2011):
+ *
+ * has changed the numbers slightly:
  *
- *     Y = 0.21268 * R    + 0.7151 * G    + 0.07217 * B
+ *     Y = 0.2126*R + 0.7152*G + 0.0722*B
  *
  *  which can be expressed with integers as
+ *
- *     Y = (6969 * R + 23434 * G + 2365 * B)/32768
+ *     Y = (6966 * R + 23436 * G + 2366 * B)/32768
  *
+ *  Historically, however, libpng uses numbers derived from the ITU-R Rec 709
+ *  end point chromaticities and the D65 white point.  Depending on the
+ *  precision used for the D65 white point this produces a variety of different
+ *  numbers, however if the four decimal place value used in ITU-R Rec 709 is
+ *  used (0.3127,0.3290) the Y calculation would be:
+ *
+ *     Y = (6968 * R + 23435 * G + 2366 * B)/32768
+ *
+ *  While this is correct the rounding results in an overflow for white, because
+ *  the sum of the rounded coefficients is 32769, not 32768.  Consequently
+ *  libpng uses, instead, the closest non-overflowing approximation:
+ *
- *  The calculation is to be done in a linear colorspace.
+ *     Y = (6968 * R + 23434 * G + 2366 * B)/32768
  *
- *  Other integer coefficents can be used via png_set_rgb_to_gray().
+ *  Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
+ *  (including an sRGB chunk) then the chromaticities are used to calculate the
+ *  coefficients.  See the chunk handling in pngrutil.c for more information.
+ *
+ *  In all cases the calculation is to be done in a linear colorspace.  If no
+ *  gamma information is available to correct the encoding of the original RGB
+ *  values this results in an implicit assumption that the original PNG RGB
+ *  values were linear.
+ *
+ *  Other integer coefficents can be used via png_set_rgb_to_gray().  Because
- */
+ *  the API takes just red and green coefficients the blue coefficient is
+ *  calculated to make the sum 32768.  This will result in different rounding
+ *  to that used above.
+ */
 int /* PRIVATE */
-png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
+png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
+{
-   png_uint_32 i;
-   png_uint_32 row_width = row_info->width;
    int rgb_error = 0;
    png_debug(1, "in png_do_rgb_to_gray");
    if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
        (row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
-      png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+      PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
-      png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
-      png_uint_32 bc = png_ptr->rgb_to_gray_blue_coeff;
+      PNG_CONST png_uint_32 bc = 32768 - rc - gc;
+      PNG_CONST png_uint_32 row_width = row_info->width;
+      PNG_CONST int have_alpha =
+         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
-      if (row_info->color_type == PNG_COLOR_TYPE_RGB)
-      {
-         if (row_info->bit_depth == 8)
+      if (row_info->bit_depth == 8)
+      {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
+         /* Notice that gamma to/from 1 are not necessarily inverses (if
+          * there is an overall gamma correction).  Prior to 1.5.5 this code
+          * checked the linearized values for equality; this doesn't match
+          * the documentation, the original values must be checked.
+          */
-            if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+         if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+         {
-               png_bytep sp = row;
+            png_bytep sp = row;
-               png_bytep dp = row;
+            png_bytep dp = row;
             png_uint_32 i;
-               for (i = 0; i < row_width; i++)
+            for (i = 0; i < row_width; i++)
+            {
-                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
+               png_byte red   = *(sp++);
-                  png_byte green = png_ptr->gamma_to_1[*(sp++)];
+               png_byte green = *(sp++);
-                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
+               png_byte blue  = *(sp++);
-                  if (red != green || red != blue)
+               if (red != green || red != blue)
+               {
-                     rgb_error |= 1;
+                  red = png_ptr->gamma_to_1[red];
+                  green = png_ptr->gamma_to_1[green];
+                  blue = png_ptr->gamma_to_1[blue];
+                  rgb_error |= 1;
-                     *(dp++) = png_ptr->gamma_from_1[
+                  *(dp++) = png_ptr->gamma_from_1[
-                         (rc*red + gc*green + bc*blue)>>15];
+                      (rc*red + gc*green + bc*blue + 16384)>>15];
-                  }
+               }
-                  else
+               else
                      *(dp++) = *(sp - 1);
+                  /* If there is no overall correction the table will not be
+                   * set.
+                   */
+                  if (png_ptr->gamma_table != NULL)
+                     red = png_ptr->gamma_table[red];
+                  *(dp++) = red;
+               }
+               if (have_alpha)
+                  *(dp++) = *(sp++);
-               }
+            }
+         }
-            else
+         else
 #endif
+         {
-               png_bytep sp = row;
+            png_bytep sp = row;
-               png_bytep dp = row;
+            png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+            png_uint_32 i;
+            for (i = 0; i < row_width; i++)
+            {
-                  png_byte red   = *(sp++);
+               png_byte red   = *(sp++);
-                  png_byte green = *(sp++);
+               png_byte green = *(sp++);
-                  png_byte blue  = *(sp++);
+               png_byte blue  = *(sp++);
-                  if (red != green || red != blue)
+               if (red != green || red != blue)
+               {
-                     rgb_error |= 1;
+                  rgb_error |= 1;
-                     *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+                  /* NOTE: this is the historical approach which simply
+                   * truncates the results.
+                   */
+                  *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+               }
-                  else
+               else
-                     *(dp++) = *(sp - 1);
+                  *(dp++) = red;
+               if (have_alpha)
+                  *(dp++) = *(sp++);
-               }
+            }
+         }
+      }
-         else /* RGB bit_depth == 16 */
+      else /* RGB bit_depth == 16 */
+      {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+#ifdef PNG_READ_GAMMA_SUPPORTED
-            if (png_ptr->gamma_16_to_1 != NULL &&
+         if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
-                png_ptr->gamma_16_from_1 != NULL)
-            {
+         {
-               png_bytep sp = row;
+            png_bytep sp = row;
-               png_bytep dp = row;
+            png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+            png_uint_32 i;
+            for (i = 0; i < row_width; i++)
+            {
-                  png_uint_16 red, green, blue, w;
+               png_uint_16 red, green, blue, w;
-                  red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  if (red == green && red == blue)
+               if (red == green && red == blue)
                      w = red;
+                  if (png_ptr->gamma_16_table != NULL)
+                     w = png_ptr->gamma_16_table[(red&0xff)
+                         >> png_ptr->gamma_shift][red>>8];
+                  else
+                     w = red;
+               }
-                  else
+               else
+               {
-                     png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
+                  png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
-                         >> png_ptr->gamma_shift][red>>8];
+                      >> png_ptr->gamma_shift][red>>8];
-                     png_uint_16 green_1 =
+                  png_uint_16 green_1 =
-                         png_ptr->gamma_16_to_1[(green&0xff) >>
+                      png_ptr->gamma_16_to_1[(green&0xff) >>
-                         png_ptr->gamma_shift][green>>8];
+                      png_ptr->gamma_shift][green>>8];
-                     png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
+                  png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
-                         >> png_ptr->gamma_shift][blue>>8];
+                      >> png_ptr->gamma_shift][blue>>8];
-                     png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
+                  png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
-                         + bc*blue_1)>>15);
+                      + bc*blue_1 + 16384)>>15);
-                     w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
+                  w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
-                         png_ptr->gamma_shift][gray16 >> 8];
+                      png_ptr->gamma_shift][gray16 >> 8];
-                     rgb_error |= 1;
+                  rgb_error |= 1;
+               }
-                  *(dp++) = (png_byte)((w>>8) & 0xff);
+               *(dp++) = (png_byte)((w>>8) & 0xff);
-                  *(dp++) = (png_byte)(w & 0xff);
+               *(dp++) = (png_byte)(w & 0xff);
+               if (have_alpha)
+               {
+                  *(dp++) = *(sp++);
+                  *(dp++) = *(sp++);
+               }
+            }
+         }
-            else
+         else
 #endif
+         {
-               png_bytep sp = row;
+            png_bytep sp = row;
-               png_bytep dp = row;
+            png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+            png_uint_32 i;
+            for (i = 0; i < row_width; i++)
+            {
-                  png_uint_16 red, green, blue, gray16;
+               png_uint_16 red, green, blue, gray16;
-                  red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  if (red != green || red != blue)
+               if (red != green || red != blue)
-                     rgb_error |= 1;
+                  rgb_error |= 1;
+               /* From 1.5.5 in the 16 bit case do the accurate conversion even
+                * in the 'fast' case - this is because this is where the code
+                * ends up when handling linear 16 bit data.
+                */
-                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
+               gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
+);
-                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
+               *(dp++) = (png_byte)((gray16>>8) & 0xff);
-                  *(dp++) = (png_byte)(gray16 & 0xff);
+               *(dp++) = (png_byte)(gray16 & 0xff);
-               }
-            }
-         }
-      }
-      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
-      {
-         if (row_info->bit_depth == 8)
-         {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
-            if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte green = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-                  *(dp++) =  png_ptr->gamma_from_1
-                      [(rc*red + gc*green + bc*blue)>>15];
-                  *(dp++) = *(sp++);  /* alpha */
-               }
-            }
-            else
-#endif
+               if (have_alpha)
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_byte red   = *(sp++);
-                  png_byte green = *(sp++);
-                  png_byte blue  = *(sp++);
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-                  *(dp++) =  (png_byte)((rc*red + gc*green + bc*blue)>>15);
-                  *(dp++) = *(sp++);  /* alpha */
-               }
-            }
-         }
-         else /* RGBA bit_depth == 16 */
-         {
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
-            if (png_ptr->gamma_16_to_1 != NULL &&
-                png_ptr->gamma_16_from_1 != NULL)
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_uint_16 red, green, blue, w;
-                  red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-                  if (red == green && red == blue)
-                     w = red;
-                  else
-                  {
-                     png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff) >>
-                         png_ptr->gamma_shift][red>>8];
-                     png_uint_16 green_1 =
-                         png_ptr->gamma_16_to_1[(green&0xff) >>
-                         png_ptr->gamma_shift][green>>8];
-                     png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff) >>
-                         png_ptr->gamma_shift][blue>>8];
-                     png_uint_16 gray16  = (png_uint_16)((rc * red_1
-                         + gc * green_1 + bc * blue_1)>>15);
-                     w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
-                         png_ptr->gamma_shift][gray16 >> 8];
-                     rgb_error |= 1;
-                  }
-                  *(dp++) = (png_byte)((w>>8) & 0xff);
-                  *(dp++) = (png_byte)(w & 0xff);
                   *(dp++) = *(sp++);  /* alpha */
-                  *(dp++) = *(sp++);
-               }
-            }
-            else
-#endif
-            {
-               png_bytep sp = row;
-               png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
-               {
-                  png_uint_16 red, green, blue, gray16;
-                  red   = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
-                  green = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
-                  blue  = (png_uint_16)((*(sp)<<8) | *(sp + 1)); sp += 2;
-                  if (red != green || red != blue)
-                     rgb_error |= 1;
-                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
-                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
-                  *(dp++) = (png_byte)(gray16 & 0xff);
-                  *(dp++) = *(sp++);  /* alpha */
+                  *(dp++) = *(sp++);
                   *(dp++) = *(sp++);
+               }
+            }
+         }
+      }
       row_info->channels -= 2;
+      row_info->channels = (png_byte)(row_info->channels - 2);
       row_info->color_type = (png_byte)(row_info->color_type &
           ~PNG_COLOR_MASK_COLOR);
       row_info->pixel_depth = (png_byte)(row_info->channels *
           row_info->bit_depth);
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+   }
    return rgb_error;
+}
 #endif
 #endif /* PNG_READ_TRANSFORMS_SUPPORTED */
+#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
 /* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth
  * large of png_color.  This lets grayscale images be treated as
  * paletted.  Most useful for gamma correction and simplification
- * of code.
+ * of code.  This API is not used internally.
  */
 void PNGAPI
 png_build_grayscale_palette(int bit_depth, png_colorp palette)
+{
    int num_palette;
    int color_inc;
    int i;
    int v;
    png_debug(1, "in png_do_build_grayscale_palette");
    if (palette == NULL)
       return;
    switch (bit_depth)
+   {
       case 1:
          num_palette = 2;
          color_inc = 0xff;
          break;
       case 2:
          num_palette = 4;
          color_inc = 0x55;
          break;
       case 4:
          num_palette = 16;
          color_inc = 0x11;
          break;
       case 8:
          num_palette = 256;
          color_inc = 1;
          break;
       default:
          num_palette = 0;
          color_inc = 0;
          break;
+   }
    for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
+   {
       palette[i].red = (png_byte)v;
       palette[i].green = (png_byte)v;
       palette[i].blue = (png_byte)v;
+   }
+}
 #endif
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
 /* Replace any alpha or transparency with the supplied background color.
  * "background" is already in the screen gamma, while "background_1" is
  * at a gamma of 1.0.  Paletted files have already been taken care of.
  */
 void /* PRIVATE */
-png_do_background(png_row_infop row_info, png_bytep row,
+png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
-    png_const_color_16p trans_color, png_const_color_16p background
+{
-#ifdef PNG_READ_GAMMA_SUPPORTED
+#ifdef PNG_READ_GAMMA_SUPPORTED
-    , png_const_color_16p background_1, png_const_bytep gamma_table,
+   png_const_bytep gamma_table = png_ptr->gamma_table;
-    png_const_bytep gamma_from_1, png_const_bytep gamma_to_1,
+   png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
-    png_const_uint_16pp gamma_16, png_const_uint_16pp gamma_16_from_1,
+   png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
+   png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
+   png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
-    png_const_uint_16pp gamma_16_to_1, int gamma_shift
+   png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
-#endif
+   int gamma_shift = png_ptr->gamma_shift;
+   int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
+#endif
-{
-   png_bytep sp, dp;
+   png_bytep sp;
    png_uint_32 i;
    png_uint_32 row_width = row_info->width;
    int shift;
-   png_debug(1, "in png_do_background");
+   png_debug(1, "in png_do_compose");
-   if (background != NULL &&
-      (!(row_info->color_type & PNG_COLOR_MASK_ALPHA) ||
       (row_info->color_type != PNG_COLOR_TYPE_PALETTE && trans_color)))
+   {
       switch (row_info->color_type)
+      {
          case PNG_COLOR_TYPE_GRAY:
+         {
             switch (row_info->bit_depth)
+            {
                case 1:
+               {
                   sp = row;
                   shift = 7;
                   for (i = 0; i < row_width; i++)
+                  {
                      if ((png_uint_16)((*sp >> shift) & 0x01)
-                        == trans_color->gray)
+                        == png_ptr->trans_color.gray)
                      {
-                        *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
+                        unsigned int tmp = *sp & (0x7f7f >> (7 - shift));
-                        *sp |= (png_byte)(background->gray << shift);
+                        tmp |= png_ptr->background.gray << shift;
-                     }
+                        *sp = (png_byte)(tmp & 0xff);
+                     }
                      if (!shift)
+                     {
                         shift = 7;
                         sp++;
+                     }
                      else
                         shift--;
+                  }
                   break;
+               }
                case 2:
+               {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
+                  {
                      sp = row;
                      shift = 6;
                      for (i = 0; i < row_width; i++)
+                     {
                         if ((png_uint_16)((*sp >> shift) & 0x03)
-                            == trans_color->gray)
+                            == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           *sp |= (png_byte)(background->gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
-                        }
+                           *sp = (png_byte)(tmp & 0xff);
+                        }
                         else
+                        {
-                           png_byte p = (png_byte)((*sp >> shift) & 0x03);
+                           unsigned int p = (*sp >> shift) & 0x03;
-                           png_byte g = (png_byte)((gamma_table [p | (p << 2) |
+                           unsigned int g = (gamma_table [p | (p << 2) |
-                               (p << 4) | (p << 6)] >> 6) & 0x03);
+                               (p << 4) | (p << 6)] >> 6) & 0x03;
-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           *sp |= (png_byte)(g << shift);
+                           tmp |= g << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
                         if (!shift)
+                        {
                            shift = 6;
                            sp++;
+                        }
                         else
                            shift -= 2;
+                     }
+                  }
                   else
 #endif
+                  {
                      sp = row;
                      shift = 6;
                      for (i = 0; i < row_width; i++)
+                     {
                         if ((png_uint_16)((*sp >> shift) & 0x03)
-                            == trans_color->gray)
+                            == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           *sp |= (png_byte)(background->gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
-                        }
+                           *sp = (png_byte)(tmp & 0xff);
+                        }
                         if (!shift)
+                        {
                            shift = 6;
                            sp++;
+                        }
                         else
                            shift -= 2;
+                     }
+                  }
                   break;
+               }
                case 4:
+               {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
+                  {
                      sp = row;
                      shift = 4;
                      for (i = 0; i < row_width; i++)
+                     {
                         if ((png_uint_16)((*sp >> shift) & 0x0f)
-                            == trans_color->gray)
+                            == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           *sp |= (png_byte)(background->gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
-                        }
+                           *sp = (png_byte)(tmp & 0xff);
+                        }
                         else
+                        {
-                           png_byte p = (png_byte)((*sp >> shift) & 0x0f);
+                           unsigned int p = (*sp >> shift) & 0x0f;
-                           png_byte g = (png_byte)((gamma_table[p |
+                           unsigned int g = (gamma_table[p | (p << 4)] >> 4) &
-                               (p << 4)] >> 4) & 0x0f);
+x0f;
-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           *sp |= (png_byte)(g << shift);
+                           tmp |= g << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
                         if (!shift)
+                        {
                            shift = 4;
                            sp++;
+                        }
                         else
                            shift -= 4;
+                     }
+                  }
                   else
 #endif
+                  {
                      sp = row;
                      shift = 4;
                      for (i = 0; i < row_width; i++)
+                     {
                         if ((png_uint_16)((*sp >> shift) & 0x0f)
-                            == trans_color->gray)
+                            == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           *sp |= (png_byte)(background->gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
-                        }
+                           *sp = (png_byte)(tmp & 0xff);
+                        }
                         if (!shift)
+                        {
                            shift = 4;
                            sp++;
+                        }
                         else
                            shift -= 4;
+                     }
+                  }
                   break;
+               }
                case 8:
+               {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_table != NULL)
+                  {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp++)
+                     {
-                        if (*sp == trans_color->gray)
+                        if (*sp == png_ptr->trans_color.gray)
-                           *sp = (png_byte)background->gray;
+                           *sp = (png_byte)png_ptr->background.gray;
                         else
                            *sp = gamma_table[*sp];
+                     }
+                  }
                   else
 #endif
+                  {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp++)
+                     {
-                        if (*sp == trans_color->gray)
+                        if (*sp == png_ptr->trans_color.gray)
-                           *sp = (png_byte)background->gray;
+                           *sp = (png_byte)png_ptr->background.gray;
                      }
+                  }
                   break;
+               }
                case 16:
+               {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                   if (gamma_16 != NULL)
+                  {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp += 2)
+                     {
                         png_uint_16 v;
                         v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-                        if (v == trans_color->gray)
+                        if (v == png_ptr->trans_color.gray)
+                        {
                            /* Background is already in screen gamma */
-                           *sp = (png_byte)((background->gray >> 8) & 0xff);
+                           *sp = (png_byte)((png_ptr->background.gray >> 8)
+                                & 0xff);
-                           *(sp + 1) = (png_byte)(background->gray & 0xff);
+                           *(sp + 1) = (png_byte)(png_ptr->background.gray
+                                & 0xff);
+                        }
                         else
+                        {
                            v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                            *sp = (png_byte)((v >> 8) & 0xff);
                            *(sp + 1) = (png_byte)(v & 0xff);
+                        }
+                     }
+                  }
                   else
 #endif
+                  {
                      sp = row;
                      for (i = 0; i < row_width; i++, sp += 2)
+                     {
                         png_uint_16 v;
                         v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-                        if (v == trans_color->gray)
+                        if (v == png_ptr->trans_color.gray)
+                        {
-                           *sp = (png_byte)((background->gray >> 8) & 0xff);
+                           *sp = (png_byte)((png_ptr->background.gray >> 8)
+                                & 0xff);
-                           *(sp + 1) = (png_byte)(background->gray & 0xff);
+                           *(sp + 1) = (png_byte)(png_ptr->background.gray
+                                & 0xff);
+                        }
+                     }
+                  }
                   break;
+               }
                default:
                   break;
+            }
             break;
+         }
          case PNG_COLOR_TYPE_RGB:
+         {
             if (row_info->bit_depth == 8)
+            {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_table != NULL)
+               {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 3)
+                  {
-                     if (*sp == trans_color->red &&
+                     if (*sp == png_ptr->trans_color.red &&
-                         *(sp + 1) == trans_color->green &&
+                         *(sp + 1) == png_ptr->trans_color.green &&
-                         *(sp + 2) == trans_color->blue)
+                         *(sp + 2) == png_ptr->trans_color.blue)
                      {
-                        *sp = (png_byte)background->red;
+                        *sp = (png_byte)png_ptr->background.red;
-                        *(sp + 1) = (png_byte)background->green;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(sp + 2) = (png_byte)background->blue;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
                      }
                      else
+                     {
                         *sp = gamma_table[*sp];
                         *(sp + 1) = gamma_table[*(sp + 1)];
                         *(sp + 2) = gamma_table[*(sp + 2)];
+                     }
+                  }
+               }
                else
 #endif
+               {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 3)
+                  {
-                     if (*sp == trans_color->red &&
+                     if (*sp == png_ptr->trans_color.red &&
-                         *(sp + 1) == trans_color->green &&
+                         *(sp + 1) == png_ptr->trans_color.green &&
-                         *(sp + 2) == trans_color->blue)
+                         *(sp + 2) == png_ptr->trans_color.blue)
                      {
-                        *sp = (png_byte)background->red;
+                        *sp = (png_byte)png_ptr->background.red;
-                        *(sp + 1) = (png_byte)background->green;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(sp + 2) = (png_byte)background->blue;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
                      }
+                  }
+               }
+            }
             else /* if (row_info->bit_depth == 16) */
+            {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL)
+               {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 6)
+                  {
                      png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                      png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
                          + *(sp + 3));
                      png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                          + *(sp + 5));
-                     if (r == trans_color->red && g == trans_color->green &&
+                     if (r == png_ptr->trans_color.red &&
+                         g == png_ptr->trans_color.green &&
-                         b == trans_color->blue)
+                         b == png_ptr->trans_color.blue)
+                     {
                         /* Background is already in screen gamma */
-                        *sp = (png_byte)((background->red >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+                                & 0xff);
-                        *(sp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
+                                & 0xff);
-                        *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+                                & 0xff);
-                        *(sp + 5) = (png_byte)(background->blue & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
                      else
+                     {
                         png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
                         *sp = (png_byte)((v >> 8) & 0xff);
                         *(sp + 1) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
                         *(sp + 2) = (png_byte)((v >> 8) & 0xff);
                         *(sp + 3) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
                         *(sp + 4) = (png_byte)((v >> 8) & 0xff);
                         *(sp + 5) = (png_byte)(v & 0xff);
+                     }
+                  }
+               }
                else
 #endif
+               {
                   sp = row;
                   for (i = 0; i < row_width; i++, sp += 6)
+                  {
                      png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                      png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
                          + *(sp + 3));
                      png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                          + *(sp + 5));
-                     if (r == trans_color->red && g == trans_color->green &&
+                     if (r == png_ptr->trans_color.red &&
+                         g == png_ptr->trans_color.green &&
-                         b == trans_color->blue)
+                         b == png_ptr->trans_color.blue)
                      {
-                        *sp = (png_byte)((background->red >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(sp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+                                & 0xff);
-                        *(sp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
+                                & 0xff);
-                        *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+                                & 0xff);
-                        *(sp + 5) = (png_byte)(background->blue & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
+                  }
+               }
+            }
             break;
+         }
          case PNG_COLOR_TYPE_GRAY_ALPHA:
+         {
             if (row_info->bit_depth == 8)
+            {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 2)
-                  for (i = 0; i < row_width; i++, sp += 2, dp++)
                   {
                      png_uint_16 a = *(sp + 1);
                      if (a == 0xff)
-                        *dp = gamma_table[*sp];
+                        *sp = gamma_table[*sp];
                      else if (a == 0)
+                     {
                         /* Background is already in screen gamma */
-                        *dp = (png_byte)background->gray;
+                        *sp = (png_byte)png_ptr->background.gray;
                      }
                      else
+                     {
                         png_byte v, w;
                         v = gamma_to_1[*sp];
-                        png_composite(w, v, a, background_1->gray);
+                        png_composite(w, v, a, png_ptr->background_1.gray);
-                        *dp = gamma_from_1[w];
+                        if (!optimize)
+                           w = gamma_from_1[w];
-                     }
+                        *sp = w;
+                     }
+                  }
+               }
                else
 #endif
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 2)
-                  for (i = 0; i < row_width; i++, sp += 2, dp++)
                   {
                      png_byte a = *(sp + 1);
-                     if (a == 0xff)
+                     if (a == 0)
-                        *dp = *sp;
-#ifdef PNG_READ_GAMMA_SUPPORTED
-                     else if (a == 0)
-                        *dp = (png_byte)background->gray;
+                        *sp = (png_byte)png_ptr->background.gray;
-                     else
+                     else if (a < 0xff)
-                        png_composite(*dp, *sp, a, background_1->gray);
-#else
-                     *dp = (png_byte)background->gray;
-#endif
+                        png_composite(*sp, *sp, a, png_ptr->background.gray);
+                  }
+               }
+            }
             else /* if (png_ptr->bit_depth == 16) */
+            {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 2)
                   {
                      png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
                          + *(sp + 3));
                      if (a == (png_uint_16)0xffff)
+                     {
                         png_uint_16 v;
                         v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
-                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(v & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
                      }
-#ifdef PNG_READ_GAMMA_SUPPORTED
                      else if (a == 0)
-#else
-                     else
-#endif
+                     {
                         /* Background is already in screen gamma */
-                        *dp = (png_byte)((background->gray >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.gray >> 8)
+                                & 0xff);
-                        *(dp + 1) = (png_byte)(background->gray & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                     }
 #ifdef PNG_READ_GAMMA_SUPPORTED
                      else
+                     {
                         png_uint_16 g, v, w;
                         g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
-                        png_composite_16(v, g, a, background_1->gray);
+                        png_composite_16(v, g, a, png_ptr->background_1.gray);
-                        w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
+                        if (optimize)
+                           w = v;
+                        else
+                           w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
-                        *dp = (png_byte)((w >> 8) & 0xff);
+                        *sp = (png_byte)((w >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(w & 0xff);
+                        *(sp + 1) = (png_byte)(w & 0xff);
                      }
 #endif
-                  }
+               }
                else
 #endif
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 2)
                   {
                      png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
                          + *(sp + 3));
-                     if (a == (png_uint_16)0xffff)
-                        png_memcpy(dp, sp, 2);
-#ifdef PNG_READ_GAMMA_SUPPORTED
-                     else if (a == 0)
+                     if (a == 0)
-#else
-                     else
-#endif
+                     {
-                        *dp = (png_byte)((background->gray >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.gray >> 8)
+                                & 0xff);
-                        *(dp + 1) = (png_byte)(background->gray & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                     }
-#ifdef PNG_READ_GAMMA_SUPPORTED
-                     else
+                     else if (a < 0xffff)
+                     {
                         png_uint_16 g, v;
                         g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
-                        png_composite_16(v, g, a, background_1->gray);
+                        png_composite_16(v, g, a, png_ptr->background.gray);
-                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(v & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
                      }
 #endif
-                  }
+               }
+            }
             break;
+         }
          case PNG_COLOR_TYPE_RGB_ALPHA:
+         {
             if (row_info->bit_depth == 8)
+            {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
                    gamma_table != NULL)
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                   {
                      png_byte a = *(sp + 3);
                      if (a == 0xff)
+                     {
-                        *dp = gamma_table[*sp];
+                        *sp = gamma_table[*sp];
-                        *(dp + 1) = gamma_table[*(sp + 1)];
+                        *(sp + 1) = gamma_table[*(sp + 1)];
-                        *(dp + 2) = gamma_table[*(sp + 2)];
+                        *(sp + 2) = gamma_table[*(sp + 2)];
                      }
                      else if (a == 0)
+                     {
                         /* Background is already in screen gamma */
-                        *dp = (png_byte)background->red;
+                        *sp = (png_byte)png_ptr->background.red;
-                        *(dp + 1) = (png_byte)background->green;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(dp + 2) = (png_byte)background->blue;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
                      }
                      else
+                     {
                         png_byte v, w;
                         v = gamma_to_1[*sp];
-                        png_composite(w, v, a, background_1->red);
+                        png_composite(w, v, a, png_ptr->background_1.red);
-                        *dp = gamma_from_1[w];
+                        if (!optimize) w = gamma_from_1[w];
+                        *sp = w;
                         v = gamma_to_1[*(sp + 1)];
-                        png_composite(w, v, a, background_1->green);
+                        png_composite(w, v, a, png_ptr->background_1.green);
-                        *(dp + 1) = gamma_from_1[w];
+                        if (!optimize) w = gamma_from_1[w];
+                        *(sp + 1) = w;
                         v = gamma_to_1[*(sp + 2)];
-                        png_composite(w, v, a, background_1->blue);
+                        png_composite(w, v, a, png_ptr->background_1.blue);
+                        if (!optimize) w = gamma_from_1[w];
-                        *(dp + 2) = gamma_from_1[w];
+                        *(sp + 2) = w;
+                     }
+                  }
+               }
                else
 #endif
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 3)
                   {
                      png_byte a = *(sp + 3);
-                     if (a == 0xff)
+                     if (a == 0)
-                     {
-                        *dp = *sp;
-                        *(dp + 1) = *(sp + 1);
-                        *(dp + 2) = *(sp + 2);
-                     }
-                     else if (a == 0)
+                     {
-                        *dp = (png_byte)background->red;
+                        *sp = (png_byte)png_ptr->background.red;
-                        *(dp + 1) = (png_byte)background->green;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
-                        *(dp + 2) = (png_byte)background->blue;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                     }
-                     else
+                     else if (a < 0xff)
                      {
-                        png_composite(*dp, *sp, a, background->red);
+                        png_composite(*sp, *sp, a, png_ptr->background.red);
-                        png_composite(*(dp + 1), *(sp + 1), a,
+                        png_composite(*(sp + 1), *(sp + 1), a,
-                            background->green);
+                            png_ptr->background.green);
-                        png_composite(*(dp + 2), *(sp + 2), a,
+                        png_composite(*(sp + 2), *(sp + 2), a,
-                            background->blue);
+                            png_ptr->background.blue);
+                     }
+                  }
+               }
+            }
             else /* if (row_info->bit_depth == 16) */
+            {
 #ifdef PNG_READ_GAMMA_SUPPORTED
                if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 8)
-                  for (i = 0; i < row_width; i++, sp += 8, dp += 6)
                   {
                      png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
                          << 8) + (png_uint_16)(*(sp + 7)));
                      if (a == (png_uint_16)0xffff)
+                     {
                         png_uint_16 v;
                         v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
-                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(v & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
-                        *(dp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 3) = (png_byte)(v & 0xff);
+                        *(sp + 3) = (png_byte)(v & 0xff);
                         v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
-                        *(dp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 5) = (png_byte)(v & 0xff);
+                        *(sp + 5) = (png_byte)(v & 0xff);
+                     }
                      else if (a == 0)
+                     {
                         /* Background is already in screen gamma */
-                        *dp = (png_byte)((background->red >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
-                        *(dp + 3) = (png_byte)(background->green & 0xff);
+                                & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                        *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                                & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                        *(dp + 5) = (png_byte)(background->blue & 0xff);
+                                & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
                      }
                      else
+                     {
-                        png_uint_16 v, w, x;
+                        png_uint_16 v, w;
                         v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
-                        png_composite_16(w, v, a, background_1->red);
+                        png_composite_16(w, v, a, png_ptr->background_1.red);
+                        if (!optimize)
-                        x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
+];
-                        *dp = (png_byte)((x >> 8) & 0xff);
+                        *sp = (png_byte)((w >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(x & 0xff);
+                        *(sp + 1) = (png_byte)(w & 0xff);
                         v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
+                        png_composite_16(w, v, a, png_ptr->background_1.green);
+                        if (!optimize)
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
-                        png_composite_16(w, v, a, background_1->green);
+];
-                        x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
-                        *(dp + 2) = (png_byte)((x >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((w >> 8) & 0xff);
-                        *(dp + 3) = (png_byte)(x & 0xff);
+                        *(sp + 3) = (png_byte)(w & 0xff);
+                        v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
+                        png_composite_16(w, v, a, png_ptr->background_1.blue);
-                        v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
+                        if (!optimize)
-                        png_composite_16(w, v, a, background_1->blue);
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
 ];
                         x = gamma_16_from_1[(w & 0xff) >> gamma_shift][w >> 8];
-                        *(dp + 4) = (png_byte)((x >> 8) & 0xff);
+                        *(sp + 4) = (png_byte)((w >> 8) & 0xff);
-                        *(dp + 5) = (png_byte)(x & 0xff);
+                        *(sp + 5) = (png_byte)(w & 0xff);
+                     }
+                  }
+               }
                else
 #endif
+               {
                   sp = row;
-                  dp = row;
+                  for (i = 0; i < row_width; i++, sp += 8)
-                  for (i = 0; i < row_width; i++, sp += 8, dp += 6)
                   {
                      png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
                          << 8) + (png_uint_16)(*(sp + 7)));
-                     if (a == (png_uint_16)0xffff)
-                     {
-                        png_memcpy(dp, sp, 6);
-                     }
-                     else if (a == 0)
+                     if (a == 0)
+                     {
-                        *dp = (png_byte)((background->red >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+                                & 0xff);
-                        *(dp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
+                                & 0xff);
-                        *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
+                                & 0xff);
-                        *(dp + 5) = (png_byte)(background->blue & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
-                     else
+                     else if (a < 0xffff)
+                     {
                         png_uint_16 v;
                         png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
                         png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
                             + *(sp + 3));
                         png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                             + *(sp + 5));
-                        png_composite_16(v, r, a, background->red);
+                        png_composite_16(v, r, a, png_ptr->background.red);
-                        *dp = (png_byte)((v >> 8) & 0xff);
+                        *sp = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(v & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
-                        png_composite_16(v, g, a, background->green);
+                        png_composite_16(v, g, a, png_ptr->background.green);
-                        *(dp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 3) = (png_byte)(v & 0xff);
+                        *(sp + 3) = (png_byte)(v & 0xff);
-                        png_composite_16(v, b, a, background->blue);
+                        png_composite_16(v, b, a, png_ptr->background.blue);
-                        *(dp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 5) = (png_byte)(v & 0xff);
+                        *(sp + 5) = (png_byte)(v & 0xff);
+                     }
+                  }
+               }
+            }
             break;
+         }
          default:
             break;
+      }
+   }
-      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
-      {
-         row_info->color_type = (png_byte)(row_info->color_type &
-             ~PNG_COLOR_MASK_ALPHA);
-         row_info->channels--;
-         row_info->pixel_depth = (png_byte)(row_info->channels *
-             row_info->bit_depth);
-         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
-      }
-   }
+}
-#endif
+#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
 #ifdef PNG_READ_GAMMA_SUPPORTED
 /* Gamma correct the image, avoiding the alpha channel.  Make sure
  * you do this after you deal with the transparency issue on grayscale
  * or RGB images. If your bit depth is 8, use gamma_table, if it
  * is 16, use gamma_16_table and gamma_shift.  Build these with
  * build_gamma_table().
  */
 void /* PRIVATE */
-png_do_gamma(png_row_infop row_info, png_bytep row,
+png_do_gamma(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
-    png_const_bytep gamma_table, png_const_uint_16pp gamma_16_table,
+{
-    int gamma_shift)
-{
-   png_bytep sp;
+   png_const_bytep gamma_table = png_ptr->gamma_table;
+   png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;
+   int gamma_shift = png_ptr->gamma_shift;
+   png_bytep sp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
    png_debug(1, "in png_do_gamma");
    if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||
        (row_info->bit_depth == 16 && gamma_16_table != NULL)))
+   {
       switch (row_info->color_type)
+      {
          case PNG_COLOR_TYPE_RGB:
+         {
             if (row_info->bit_depth == 8)
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   *sp = gamma_table[*sp];
                   sp++;
                   *sp = gamma_table[*sp];
                   sp++;
                   *sp = gamma_table[*sp];
                   sp++;
+               }
+            }
             else /* if (row_info->bit_depth == 16) */
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   png_uint_16 v;
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
+               }
+            }
             break;
+         }
          case PNG_COLOR_TYPE_RGB_ALPHA:
+         {
             if (row_info->bit_depth == 8)
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   *sp = gamma_table[*sp];
                   sp++;
                   *sp = gamma_table[*sp];
                   sp++;
                   *sp = gamma_table[*sp];
                   sp++;
                   sp++;
+               }
+            }
             else /* if (row_info->bit_depth == 16) */
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
                   v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 4;
+               }
+            }
             break;
+         }
          case PNG_COLOR_TYPE_GRAY_ALPHA:
+         {
             if (row_info->bit_depth == 8)
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   *sp = gamma_table[*sp];
                   sp += 2;
+               }
+            }
             else /* if (row_info->bit_depth == 16) */
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 4;
+               }
+            }
             break;
+         }
          case PNG_COLOR_TYPE_GRAY:
+         {
             if (row_info->bit_depth == 2)
+            {
                sp = row;
                for (i = 0; i < row_width; i += 4)
+               {
                   int a = *sp & 0xc0;
                   int b = *sp & 0x30;
                   int c = *sp & 0x0c;
                   int d = *sp & 0x03;
                   *sp = (png_byte)(
                       ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|
                       ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
                       ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
                       ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
                   sp++;
+               }
+            }
             if (row_info->bit_depth == 4)
+            {
                sp = row;
                for (i = 0; i < row_width; i += 2)
+               {
                   int msb = *sp & 0xf0;
                   int lsb = *sp & 0x0f;
                   *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
                       | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
                   sp++;
+               }
+            }
             else if (row_info->bit_depth == 8)
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   *sp = gamma_table[*sp];
                   sp++;
+               }
+            }
             else if (row_info->bit_depth == 16)
+            {
                sp = row;
                for (i = 0; i < row_width; i++)
+               {
                   png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
                   *sp = (png_byte)((v >> 8) & 0xff);
                   *(sp + 1) = (png_byte)(v & 0xff);
                   sp += 2;
+               }
+            }
             break;
+         }
          default:
             break;
+      }
+   }
+}
 #endif
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+/* Encode the alpha channel to the output gamma (the input channel is always
+ * linear.)  Called only with color types that have an alpha channel.  Needs the
+ * from_1 tables.
+ */
+void /* PRIVATE */
+png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
+{
+   png_uint_32 row_width = row_info->width;
+   png_debug(1, "in png_do_encode_alpha");
+   if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+   {
+      if (row_info->bit_depth == 8)
+      {
+         PNG_CONST png_bytep table = png_ptr->gamma_from_1;
+         if (table != NULL)
+         {
+            PNG_CONST int step =
+               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
+            /* The alpha channel is the last component: */
+            row += step - 1;
+            for (; row_width > 0; --row_width, row += step)
+               *row = table[*row];
+            return;
+         }
+      }
+      else if (row_info->bit_depth == 16)
+      {
+         PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;
+         PNG_CONST int gamma_shift = png_ptr->gamma_shift;
+         if (table != NULL)
+         {
+            PNG_CONST int step =
+               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
+            /* The alpha channel is the last component: */
+            row += step - 2;
+            for (; row_width > 0; --row_width, row += step)
+            {
+               png_uint_16 v;
+               v = table[*(row + 1) >> gamma_shift][*row];
+               *row = (png_byte)((v >> 8) & 0xff);
+               *(row + 1) = (png_byte)(v & 0xff);
+            }
+            return;
+         }
+      }
+   }
+   /* Only get to here if called with a weird row_info; no harm has been done,
+    * so just issue a warning.
+    */
+   png_warning(png_ptr, "png_do_encode_alpha: unexpected call");
+}
+#endif
 #ifdef PNG_READ_EXPAND_SUPPORTED
 /* Expands a palette row to an RGB or RGBA row depending
  * upon whether you supply trans and num_trans.
  */
 void /* PRIVATE */
 png_do_expand_palette(png_row_infop row_info, png_bytep row,
    png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
+{
    int shift, value;
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
    png_debug(1, "in png_do_expand_palette");
    if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+   {
       if (row_info->bit_depth < 8)
+      {
          switch (row_info->bit_depth)
+         {
             case 1:
+            {
                sp = row + (png_size_t)((row_width - 1) >> 3);
                dp = row + (png_size_t)row_width - 1;
                shift = 7 - (int)((row_width + 7) & 0x07);
                for (i = 0; i < row_width; i++)
+               {
                   if ((*sp >> shift) & 0x01)
                      *dp = 1;
                   else
                      *dp = 0;
                   if (shift == 7)
+                  {
                      shift = 0;
                      sp--;
+                  }
                   else
                      shift++;
                   dp--;
+               }
                break;
+            }
             case 2:
+            {
                sp = row + (png_size_t)((row_width - 1) >> 2);
                dp = row + (png_size_t)row_width - 1;
                shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                for (i = 0; i < row_width; i++)
+               {
                   value = (*sp >> shift) & 0x03;
                   *dp = (png_byte)value;
                   if (shift == 6)
+                  {
                      shift = 0;
                      sp--;
+                  }
                   else
                      shift += 2;
                   dp--;
+               }
                break;
+            }
             case 4:
+            {
                sp = row + (png_size_t)((row_width - 1) >> 1);
                dp = row + (png_size_t)row_width - 1;
                shift = (int)((row_width & 0x01) << 2);
                for (i = 0; i < row_width; i++)
+               {
                   value = (*sp >> shift) & 0x0f;
                   *dp = (png_byte)value;
                   if (shift == 4)
+                  {
                      shift = 0;
                      sp--;
+                  }
                   else
                      shift += 4;
                   dp--;
+               }
                break;
+            }
             default:
                break;
+         }
          row_info->bit_depth = 8;
          row_info->pixel_depth = 8;
          row_info->rowbytes = row_width;
+      }
       if (row_info->bit_depth == 8)
+      {
+         {
-            if (trans_alpha != NULL)
+            if (num_trans > 0)
             {
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width << 2) - 1;
                for (i = 0; i < row_width; i++)
+               {
                   if ((int)(*sp) >= num_trans)
                      *dp-- = 0xff;
                   else
                      *dp-- = trans_alpha[*sp];
                   *dp-- = palette[*sp].blue;
                   *dp-- = palette[*sp].green;
                   *dp-- = palette[*sp].red;
                   sp--;
+               }
                row_info->bit_depth = 8;
                row_info->pixel_depth = 32;
                row_info->rowbytes = row_width * 4;
                row_info->color_type = 6;
                row_info->channels = 4;
+            }
             else
+            {
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width * 3) - 1;
                for (i = 0; i < row_width; i++)
+               {
                   *dp-- = palette[*sp].blue;
                   *dp-- = palette[*sp].green;
                   *dp-- = palette[*sp].red;
                   sp--;
+               }
                row_info->bit_depth = 8;
                row_info->pixel_depth = 24;
                row_info->rowbytes = row_width * 3;
                row_info->color_type = 2;
                row_info->channels = 3;
+            }
+         }
+      }
+   }
+}
 /* If the bit depth < 8, it is expanded to 8.  Also, if the already
  * expanded transparency value is supplied, an alpha channel is built.
  */
 void /* PRIVATE */
 png_do_expand(png_row_infop row_info, png_bytep row,
-    png_const_color_16p trans_value)
+    png_const_color_16p trans_color)
 {
    int shift, value;
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
    png_debug(1, "in png_do_expand");
+   {
       if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
+      {
-         png_uint_16 gray = (png_uint_16)(trans_value ? trans_value->gray : 0);
+         unsigned int gray = trans_color ? trans_color->gray : 0;
          if (row_info->bit_depth < 8)
+         {
             switch (row_info->bit_depth)
+            {
                case 1:
+               {
-                  gray = (png_uint_16)((gray & 0x01) * 0xff);
+                  gray = (gray & 0x01) * 0xff;
                   sp = row + (png_size_t)((row_width - 1) >> 3);
                   dp = row + (png_size_t)row_width - 1;
                   shift = 7 - (int)((row_width + 7) & 0x07);
                   for (i = 0; i < row_width; i++)
+                  {
                      if ((*sp >> shift) & 0x01)
                         *dp = 0xff;
                      else
                         *dp = 0;
                      if (shift == 7)
+                     {
                         shift = 0;
                         sp--;
+                     }
                      else
                         shift++;
                      dp--;
+                  }
                   break;
+               }
                case 2:
+               {
-                  gray = (png_uint_16)((gray & 0x03) * 0x55);
+                  gray = (gray & 0x03) * 0x55;
                   sp = row + (png_size_t)((row_width - 1) >> 2);
                   dp = row + (png_size_t)row_width - 1;
                   shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
                   for (i = 0; i < row_width; i++)
+                  {
                      value = (*sp >> shift) & 0x03;
                      *dp = (png_byte)(value | (value << 2) | (value << 4) |
                         (value << 6));
                      if (shift == 6)
+                     {
                         shift = 0;
                         sp--;
+                     }
                      else
                         shift += 2;
                      dp--;
+                  }
                   break;
+               }
                case 4:
+               {
-                  gray = (png_uint_16)((gray & 0x0f) * 0x11);
+                  gray = (gray & 0x0f) * 0x11;
                   sp = row + (png_size_t)((row_width - 1) >> 1);
                   dp = row + (png_size_t)row_width - 1;
                   shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
                   for (i = 0; i < row_width; i++)
+                  {
                      value = (*sp >> shift) & 0x0f;
                      *dp = (png_byte)(value | (value << 4));
                      if (shift == 4)
+                     {
                         shift = 0;
                         sp--;
+                     }
                      else
                         shift = 4;
                      dp--;
+                  }
                   break;
+               }
                default:
                   break;
+            }
             row_info->bit_depth = 8;
             row_info->pixel_depth = 8;
             row_info->rowbytes = row_width;
+         }
-         if (trans_value != NULL)
+         if (trans_color != NULL)
+         {
             if (row_info->bit_depth == 8)
+            {
                gray = gray & 0xff;
                sp = row + (png_size_t)row_width - 1;
                dp = row + (png_size_t)(row_width << 1) - 1;
                for (i = 0; i < row_width; i++)
+               {
                   if (*sp == gray)
                      *dp-- = 0;
                   else
                      *dp-- = 0xff;
                   *dp-- = *sp--;
+               }
+            }
             else if (row_info->bit_depth == 16)
+            {
-               png_byte gray_high = (png_byte)((gray >> 8) & 0xff);
+               unsigned int gray_high = (gray >> 8) & 0xff;
-               png_byte gray_low = (png_byte)(gray & 0xff);
+               unsigned int gray_low = gray & 0xff;
                sp = row + row_info->rowbytes - 1;
                dp = row + (row_info->rowbytes << 1) - 1;
                for (i = 0; i < row_width; i++)
+               {
                   if (*(sp - 1) == gray_high && *(sp) == gray_low)
+                  {
                      *dp-- = 0;
                      *dp-- = 0;
+                  }
                   else
+                  {
                      *dp-- = 0xff;
                      *dp-- = 0xff;
+                  }
                   *dp-- = *sp--;
                   *dp-- = *sp--;
+               }
+            }
             row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
             row_info->channels = 2;
             row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
             row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
                row_width);
+         }
+      }
-      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_value)
+      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)
       {
          if (row_info->bit_depth == 8)
+         {
-            png_byte red = (png_byte)(trans_value->red & 0xff);
+            png_byte red = (png_byte)(trans_color->red & 0xff);
-            png_byte green = (png_byte)(trans_value->green & 0xff);
+            png_byte green = (png_byte)(trans_color->green & 0xff);
-            png_byte blue = (png_byte)(trans_value->blue & 0xff);
+            png_byte blue = (png_byte)(trans_color->blue & 0xff);
             sp = row + (png_size_t)row_info->rowbytes - 1;
             dp = row + (png_size_t)(row_width << 2) - 1;
             for (i = 0; i < row_width; i++)
+            {
                if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)
                   *dp-- = 0;
                else
                   *dp-- = 0xff;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
+            }
+         }
          else if (row_info->bit_depth == 16)
+         {
-            png_byte red_high = (png_byte)((trans_value->red >> 8) & 0xff);
+            png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);
-            png_byte green_high = (png_byte)((trans_value->green >> 8) & 0xff);
+            png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);
-            png_byte blue_high = (png_byte)((trans_value->blue >> 8) & 0xff);
+            png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);
-            png_byte red_low = (png_byte)(trans_value->red & 0xff);
+            png_byte red_low = (png_byte)(trans_color->red & 0xff);
-            png_byte green_low = (png_byte)(trans_value->green & 0xff);
+            png_byte green_low = (png_byte)(trans_color->green & 0xff);
-            png_byte blue_low = (png_byte)(trans_value->blue & 0xff);
+            png_byte blue_low = (png_byte)(trans_color->blue & 0xff);
             sp = row + row_info->rowbytes - 1;
             dp = row + (png_size_t)(row_width << 3) - 1;
             for (i = 0; i < row_width; i++)
+            {
                if (*(sp - 5) == red_high &&
                    *(sp - 4) == red_low &&
                    *(sp - 3) == green_high &&
                    *(sp - 2) == green_low &&
                    *(sp - 1) == blue_high &&
                    *(sp    ) == blue_low)
+               {
                   *dp-- = 0;
                   *dp-- = 0;
+               }
                else
+               {
                   *dp-- = 0xff;
                   *dp-- = 0xff;
+               }
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
                *dp-- = *sp--;
+            }
+         }
          row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
          row_info->channels = 4;
          row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+      }
+   }
+}
 #endif
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* If the bit depth is 8 and the color type is not a palette type expand the
+ * whole row to 16 bits.  Has no effect otherwise.
+ */
+void /* PRIVATE */
+png_do_expand_16(png_row_infop row_info, png_bytep row)
+{
+   if (row_info->bit_depth == 8 &&
+      row_info->color_type != PNG_COLOR_TYPE_PALETTE)
+   {
+      /* The row have a sequence of bytes containing [0..255] and we need
+       * to turn it into another row containing [0..65535], to do this we
+       * calculate:
+       *
+       *  (input / 255) * 65535
+       *
+       *  Which happens to be exactly input * 257 and this can be achieved
+       *  simply by byte replication in place (copying backwards).
+       */
+      png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */
+      png_byte *dp = sp + row_info->rowbytes;  /* destination, end + 1 */
+      while (dp > sp)
+         dp[-2] = dp[-1] = *--sp, dp -= 2;
+      row_info->rowbytes *= 2;
+      row_info->bit_depth = 16;
+      row_info->pixel_depth = (png_byte)(row_info->channels * 16);
+   }
+}
+#endif
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
 void /* PRIVATE */
 png_do_quantize(png_row_infop row_info, png_bytep row,
     png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
+{
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
    png_debug(1, "in png_do_quantize");
    if (row_info->bit_depth == 8)
+   {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
+      {
          int r, g, b, p;
          sp = row;
          dp = row;
          for (i = 0; i < row_width; i++)
+         {
             r = *sp++;
             g = *sp++;
             b = *sp++;
             /* This looks real messy, but the compiler will reduce
              * it down to a reasonable formula.  For example, with
              * 5 bits per color, we get:
              * p = (((r >> 3) & 0x1f) << 10) |
              *    (((g >> 3) & 0x1f) << 5) |
              *    ((b >> 3) & 0x1f);
              */
             p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                 ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                 (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                 (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                 ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                 (PNG_QUANTIZE_BLUE_BITS)) |
                 ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                 ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
             *dp++ = palette_lookup[p];
+         }
          row_info->color_type = PNG_COLOR_TYPE_PALETTE;
          row_info->channels = 1;
          row_info->pixel_depth = row_info->bit_depth;
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+      }
       else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
          palette_lookup != NULL)
+      {
          int r, g, b, p;
          sp = row;
          dp = row;
          for (i = 0; i < row_width; i++)
+         {
             r = *sp++;
             g = *sp++;
             b = *sp++;
             sp++;
             p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                 ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                 (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                 (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                 ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                 (PNG_QUANTIZE_BLUE_BITS)) |
                 ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                 ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
             *dp++ = palette_lookup[p];
+         }
          row_info->color_type = PNG_COLOR_TYPE_PALETTE;
          row_info->channels = 1;
          row_info->pixel_depth = row_info->bit_depth;
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+      }
       else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
          quantize_lookup)
+      {
          sp = row;
          for (i = 0; i < row_width; i++, sp++)
+         {
             *sp = quantize_lookup[*sp];
+         }
+      }
+   }
+}
 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
 #endif /* PNG_READ_TRANSFORMS_SUPPORTED */
 #ifdef PNG_MNG_FEATURES_SUPPORTED
 /* Undoes intrapixel differencing  */
 void /* PRIVATE */
 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
+{
    png_debug(1, "in png_do_read_intrapixel");
    if (
        (row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
       int bytes_per_pixel;
       png_uint_32 row_width = row_info->width;
       if (row_info->bit_depth == 8)
+      {
          png_bytep rp;
          png_uint_32 i;
          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
             bytes_per_pixel = 3;
          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
             bytes_per_pixel = 4;
          else
             return;
          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+         {
             *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
             *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
+         }
+      }
       else if (row_info->bit_depth == 16)
+      {
          png_bytep rp;
          png_uint_32 i;
          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
             bytes_per_pixel = 6;
          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
             bytes_per_pixel = 8;
          else
             return;
          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+         {
             png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);
             png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);
             png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);
-            png_uint_32 red  = (png_uint_32)((s0 + s1 + 65536L) & 0xffffL);
+            png_uint_32 red  = (s0 + s1 + 65536) & 0xffff;
-            png_uint_32 blue = (png_uint_32)((s2 + s1 + 65536L) & 0xffffL);
+            png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
             *(rp    ) = (png_byte)((red >> 8) & 0xff);
             *(rp + 1) = (png_byte)(red & 0xff);
             *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
             *(rp + 5) = (png_byte)(blue & 0xff);
+         }
+      }
+   }
+}
 #endif /* PNG_MNG_FEATURES_SUPPORTED */
 #endif /* PNG_READ_SUPPORTED */
+>
+>
+>
+>
+>
+>
+>
+>

Subversion Repositories Kolibri OS

(root)/programs/develop/libraries/libpng/pngrtran.c – Rev 1897 → 3928