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
 #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");
          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;
-      return;
+   }
-   }
+   png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
+   png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-   png_ptr->transformations |= PNG_BACKGROUND;
+   png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
    png_memcpy(&(png_ptr->background), background_color,
+   png_ptr->background = *background_color;
-      png_sizeof(png_color_16));
+   png_ptr->background_gamma = background_gamma;
+   png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
+   if (need_expand)
-   png_ptr->background_gamma = background_gamma;
+      png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
-   png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
+   else
-   png_ptr->transformations |= (need_expand ? PNG_BACKGROUND_EXPAND : 0);
+      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 */
-      need_expand, png_fixed(png_ptr, background_gamma, "png_set_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_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  /* FLOATING_POINT */
-#endif /* READ_BACKGROUND */
+#endif
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#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_structrp png_ptr)
+{
+   png_debug(1, "in png_set_strip_alpha");
+   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.
+    */
-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if (output_gamma > 0 && output_gamma < 128)
-void PNGAPI
+      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");
+   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;
+   }
+}
 png_set_strip_alpha(png_structp png_ptr)
-{
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
-   png_debug(1, "in png_set_strip_alpha");
+void PNGAPI
 png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
    if (png_ptr == NULL)
-      return;
+   png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
       output_gamma));
    png_ptr->flags |= PNG_FLAG_STRIP_ALPHA;
 #  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)
+{
          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 */
          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))));
                   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)
       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++)
+}
 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
 #ifdef PNG_READ_GAMMA_SUPPORTED
-/* Transform the image from the file_gamma to the screen_gamma.  We
- * 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 (file_gamma <= 0)
+      png_error(png_ptr, "invalid file gamma in png_set_gamma");
-   if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) ||
+   if (scrn_gamma <= 0)
+      png_error(png_ptr, "invalid screen gamma in png_set_gamma");
-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ||
+   /* Set the gamma values unconditionally - this overrides the value in the PNG
+    * file if a gAMA chunk was present.  png_set_alpha_mode provides a
-       png_gamma_threshold(scrn_gamma, file_gamma))
+    * 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)
+void PNGAPI
-{
+png_set_gamma(png_structrp png_ptr, double scrn_gamma, double file_gamma)
    png_set_gamma_fixed(png_ptr,
-      png_fixed(png_ptr, scrn_gamma, "png_set_gamma screen gamma"),
+   png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_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");
    png_debug(1, "in png_set_expand");
    if (png_ptr == NULL)
-      return;
+   if (!png_rtran_ok(png_ptr, 0))
       return;
  */
 /* 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;
+   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+}
 /* 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)
-      return;
-   png_ptr->transformations |= PNG_EXPAND;
+   if (!png_rtran_ok(png_ptr, 0))
-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+      return;
-}
    png_ptr->transformations |= PNG_EXPAND;
+}
+/* Expand tRNS chunks to alpha channels. */
+void PNGAPI
 png_set_tRNS_to_alpha(png_structrp png_ptr)
-/* Expand tRNS chunks to alpha channels. */
 void PNGAPI
-png_set_tRNS_to_alpha(png_structp 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);
+}
+#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");
-   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;
+   png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
 }
-#endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
+#endif
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+void PNGAPI
-void PNGAPI
+png_set_gray_to_rgb(png_structrp png_ptr)
-png_set_gray_to_rgb(png_structp png_ptr)
-{
    png_debug(1, "in png_set_gray_to_rgb");
    png_debug(1, "in png_set_gray_to_rgb");
    if (png_ptr != NULL)
    if (!png_rtran_ok(png_ptr, 0))
-      /* Because rgb must be 8 bits or more: */
+      return;
       png_set_expand_gray_1_2_4_to_8(png_ptr);
-      png_ptr->transformations |= PNG_GRAY_TO_RGB;
+   /* Because rgb must be 8 bits or more: */
-      png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+   png_set_expand_gray_1_2_4_to_8(png_ptr);
+   png_ptr->transformations |= PNG_GRAY_TO_RGB;
+}
-   }
+#endif
-#endif
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 void PNGFAPI
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+png_set_rgb_to_gray_fixed(png_structrp png_ptr, int error_action,
-void PNGFAPI
+    png_fixed_point red, png_fixed_point green)
 png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
-    png_fixed_point red, png_fixed_point green)
+   png_debug(1, "in png_set_rgb_to_gray");
-   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;
-         png_ptr->transformations |= PNG_RGB_TO_GRAY;
+         break;
          break;
       case PNG_ERROR_ACTION_WARN:
-      case 2:
+         png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
-         png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
+         break;
+      case PNG_ERROR_ACTION_ERROR:
+         png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
          break;
-      case 3:
+      default:
-         png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
+         png_error(png_ptr, "invalid error action to rgb_to_gray");
          break;
+   }
-      default:
-         png_error(png_ptr, "invalid error action to rgb_to_gray");
-         break;
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-   }
+#ifdef PNG_READ_EXPAND_SUPPORTED
-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-#ifdef PNG_READ_EXPAND_SUPPORTED
+      png_ptr->transformations |= PNG_EXPAND;
+#else
+   {
-      png_ptr->transformations |= PNG_EXPAND;
+      /* Make this an error in 1.6 because otherwise the application may assume
-#else
+       * that it just worked and get a memory overwrite.
-   {
+       */
-      png_warning(png_ptr,
+      png_error(png_ptr,
+        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
+      /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
+   }
-        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
+#endif
+   {
-      png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
+      if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
-   }
+      {
-#endif
+         png_uint_16 red_int, green_int;
-   {
-      png_uint_16 red_int, green_int;
+         /* 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
+          * defaulted or set already.
+          */
+         red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
-      if (red < 0 || green < 0)
+         green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
-      {
+         png_ptr->rgb_to_gray_red_coeff   = red_int;
-         red_int   =  6968; /* .212671 * 32768 + .5 */
+         png_ptr->rgb_to_gray_green_coeff = green_int;
-         green_int = 23434; /* .715160 * 32768 + .5 */
+         png_ptr->rgb_to_gray_coefficients_set = 1;
+      }
+      else
+      {
          if (red >= 0 && green >= 0)
-      else if (red + green < 100000L)
+            png_app_warning(png_ptr,
                "ignoring out of range rgb_to_gray coefficients");
          red_int = (png_uint_16)(((png_uint_32)red*32768L)/100000L);
-         green_int = (png_uint_16)(((png_uint_32)green*32768L)/100000L);
+         /* 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
-      else
+          * the coefficients are not marked as 'set' and are not overwritten if
           * something has already provided a default.
-         png_warning(png_ptr, "ignoring out of range rgb_to_gray coefficients");
-         red_int   =  6968;
-         green_int = 23434;
           */
          if (png_ptr->rgb_to_gray_red_coeff == 0 &&
-      png_ptr->rgb_to_gray_red_coeff   = red_int;
+            png_ptr->rgb_to_gray_green_coeff == 0)
       png_ptr->rgb_to_gray_green_coeff = green_int;
-      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.
- */
+#ifdef PNG_FLOATING_POINT_SUPPORTED
-void PNGAPI
-png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
-   double green)
+/* 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.
-   if (png_ptr == NULL)
+ */
       return;
 void PNGAPI
-   png_set_rgb_to_gray_fixed(png_ptr, error_action,
+png_set_rgb_to_gray(png_structrp png_ptr, int error_action, double red,
+   double green)
+{
+   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 /* 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_structrp png_ptr, png_user_transform_ptr
+    read_user_transform_fn)
+{
+   png_debug(1, "in png_set_read_user_transform_fn");
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
+   png_ptr->transformations |= PNG_USER_TRANSFORM;
+   png_ptr->read_user_transform_fn = read_user_transform_fn;
+#endif
       png_fixed(png_ptr, red, "rgb to gray red coefficient"),
-      png_fixed(png_ptr, green, "rgb to gray green coefficient"));
+#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.
+ */
-#endif /* FLOATING POINT */
+static int /* PRIVATE */
+png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
 #endif
+   /* 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);
+}
-#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
+#endif
+/* Initialize everything needed for the read.  This includes modifying
+ * the palette.
-    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
+ */
-void PNGAPI
+/*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_palette_transformations(png_structrp png_ptr)
+{
+   /* 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;
-png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
+   if (png_ptr->num_trans > 0)
+   {
+      int i;
-    read_user_transform_fn)
+      /* Ignore if all the entries are opaque (unlikely!) */
+      for (i=0; inum_trans; ++i)
-{
+      {
-   png_debug(1, "in png_set_read_user_transform_fn");
+         if (png_ptr->trans_alpha[i] == 255)
+            continue;
+         else if (png_ptr->trans_alpha[i] == 0)
+            input_has_transparency = 1;
+         else
-   if (png_ptr == NULL)
+         {
-      return;
-#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
+            input_has_transparency = 1;
-   png_ptr->transformations |= PNG_USER_TRANSFORM;
-   png_ptr->read_user_transform_fn = read_user_transform_fn;
-#endif
-}
-#endif
             input_has_alpha = 1;
-/* Initialize everything needed for the read.  This includes modifying
+            break;
- * the palette.
+         }
  */
-void /* PRIVATE */
-png_init_read_transformations(png_structp png_ptr)
+   }
+   /* 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_debug(1, "in png_init_read_transformations");
+       */
-  {
-#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
-    defined(PNG_READ_SHIFT_SUPPORTED) || \
+      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-    defined(PNG_READ_GAMMA_SUPPORTED)
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+      if (!input_has_transparency)
+         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
+   }
-   int color_type = png_ptr->color_type;
+#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.
+    */
 #endif
+   /* The following code cannot be entered in the alpha pre-multiplication case
+    * because PNG_BACKGROUND_EXPAND is cancelled below.
+    */
+   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+       (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->background.blue  =
+             png_ptr->palette[png_ptr->background.index].blue;
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+        {
+           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+           {
+              /* 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
-#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+    * 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;
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-   /* Detect gray background and attempt to enable optimization
-    * for gray --> RGB case
+   /* 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
-    * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
+       * and ENCODE_ALPHA are irrelevant.
-    * RGB_ALPHA (in which case need_expand is superfluous anyway), the
+       */
-    * background color might actually be gray yet not be flagged as such.
+#     ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-    * 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.
-    */
-   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
-       !(color_type & PNG_COLOR_MASK_COLOR))
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
-   {
-      png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
-   }
 #     endif
    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 &&
-       png_ptr->background.red == png_ptr->background.blue)
-   {
+      if (!input_has_transparency)
-      png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
-      png_ptr->background.gray = png_ptr->background.red;
-   }
-#endif
+   }
    if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
-       (png_ptr->transformations & PNG_EXPAND))
-   {
-      if (!(color_type & PNG_COLOR_MASK_COLOR))  /* i.e., GRAY or GRAY_ALPHA */
-      {
-         /* Expand background and tRNS chunks */
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
-         switch (png_ptr->bit_depth)
+   /* png_set_background handling - deals with the complexity of whether the
-         {
-            case 1:
-               png_ptr->background.gray *= (png_uint_16)0xff;
-               png_ptr->background.red = png_ptr->background.green
+    * background color is in the file format or the screen format in the case
-                   =  png_ptr->background.blue = png_ptr->background.gray;
+    * where an 'expand' will happen.
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+    */
    /* The following code cannot be entered in the alpha pre-multiplication case
-                 png_ptr->trans_color.gray *= (png_uint_16)0xff;
+    * because PNG_BACKGROUND_EXPAND is cancelled below.
-                 png_ptr->trans_color.red = png_ptr->trans_color.green
-                     = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
+    */
    if ((png_ptr->transformations & PNG_BACKGROUND_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 */
+         int gray = png_ptr->background.gray;
+         int trans_gray = png_ptr->trans_color.gray;
-               break;
+         switch (png_ptr->bit_depth)
+         {
+            case 1:
+               gray *= 0xff;
+               trans_gray *= 0xff;
+               break;
             case 2:
-               png_ptr->background.gray *= (png_uint_16)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;
+               gray *= 0x55;
+               trans_gray *= 0x55;
+               break;
+            case 4:
+               gray *= 0x11;
+               trans_gray *= 0x11;
+               break;
-                  png_ptr->trans_color.red = png_ptr->trans_color.green
+            default:
+            case 8:
+               /* FALL THROUGH (Already 8 bits) */
-                      = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
+            case 16:
+               /* Already a full 16 bits */
                break;
+         }
+         png_ptr->background.red = png_ptr->background.green =
-               break;
+            png_ptr->background.blue = (png_uint_16)gray;
+         if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-            case 4:
                png_ptr->background.gray *= (png_uint_16)0x11;
+            png_ptr->trans_color.red = png_ptr->trans_color.green =
+               png_ptr->trans_color.blue = (png_uint_16)trans_gray;
+         }
+      }
+   } /* background expand and (therefore) no alpha association. */
-               png_ptr->background.red = png_ptr->background.green
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
-                   = png_ptr->background.blue = png_ptr->background.gray;
+}
                if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                  png_ptr->trans_color.gray *= (png_uint_16)0x11;
-                  png_ptr->trans_color.red = png_ptr->trans_color.green
-                      = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
+void /* PRIVATE */
-               }
-               break;
+png_init_read_transformations(png_structrp png_ptr)
+{
+   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
+    * the tests were repeated for the PALETTE color type here - this is no
+    * longer necessary (and doesn't seem to have been necessary before.)
+    */
+   {
+      /* The following temporary indicates if overall gamma correction is
+       * required.
+       */
+      int gamma_correction = 0;
+      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
+            /* Assume the output matches the input; a long time default behavior
+             * of libpng, although the standard has nothing to say about this.
              */
-            default:
+            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)
-            case 8:
+    * 20) PNG_INVERT_ALPHA
     * 21) PNG_SWAP_ALPHA
-            case 16:
+    * 22) PNG_SWAP_BYTES
+    * 23) PNG_USER_TRANSFORM [must be last]
+    */
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
-               png_ptr->background.red = png_ptr->background.green
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+      !(png_ptr->transformations & PNG_COMPOSE))
                    = png_ptr->background.blue = png_ptr->background.gray;
-               break;
+      /* 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
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+   /* Make sure the coefficients for the rgb to gray conversion are set
+    * appropriately.
-      else if (color_type == PNG_COLOR_TYPE_PALETTE)
+    */
-      {
+   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-         png_ptr->background.red   =
-             png_ptr->palette[png_ptr->background.index].red;
+      png_colorspace_set_rgb_coefficients(png_ptr);
-         png_ptr->background.green =
+#endif
-             png_ptr->palette[png_ptr->background.index].green;
-         png_ptr->background.blue  =
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
-             png_ptr->palette[png_ptr->background.index].blue;
+   /* Detect gray background and attempt to enable optimization for
-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
-        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+    * 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)
+   {
+      /* 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.
+       */
+      if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+      {
+         if (png_ptr->background.red == png_ptr->background.green &&
+             png_ptr->background.red == png_ptr->background.blue)
+         {
+            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+            png_ptr->background.gray = png_ptr->background.red;
+         }
+      }
+   }
+#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
-#ifdef PNG_READ_EXPAND_SUPPORTED
+    * 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
-           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+    * background support (see the comments in scripts/pnglibconf.dfa), this
-#endif
+    * allows pre-multiplication of the alpha channel to be implemented as
     * compositing on black.  This is probably sub-optimal and has been done in
-              /* Invert the alpha channel (in tRNS) unless the pixels are
+    * 1.5.4 betas simply to enable external critique and testing (i.e. to
-               * going to be expanded, in which case leave it for later
+    * 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
-              int i, istop;
+    * 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
-              istop=(int)png_ptr->num_trans;
+    * 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
-              for (i=0; i
+    * gamma encoded value.
                  png_ptr->trans_alpha[i] = (png_byte)(255 -
-                    png_ptr->trans_alpha[i]);
+    * 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.
                      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:
+               }
                if (png_gamma_significant(gs))
+               {
-                  back.red   = (png_byte)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);
+               }
+               else
+               {
-               back_1.red = png_gamma_8bit_correct(png_ptr->background.red, g);
+                  back.red   = (png_byte)png_ptr->background.red;
+                  back.green = (png_byte)png_ptr->background.green;
+                  back.blue  = (png_byte)png_ptr->background.blue;
+               }
+               if (png_gamma_significant(g))
+               {
-               back_1.green = png_gamma_8bit_correct(png_ptr->background.green,
+                  back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
-                   g);
+                     g);
+                  back_1.green = png_gamma_8bit_correct(
+                     png_ptr->background.green, g);
-               back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
+                  back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
-                   g);
+                     g);
+               }
+               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)
+               {
                   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->colorspace.gamma);
-                  g = png_reciprocal(png_ptr->gamma);
+                  gs = png_reciprocal2(png_ptr->colorspace.gamma,
-                  gs = png_reciprocal2(png_ptr->gamma, png_ptr->screen_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))
+            {
-                (png_ptr->background.red != png_ptr->background.gray))
+               /* RGB or RGBA with color background */
                if (g_sig)
                /* RGB or RGBA with color background */
-               png_ptr->background_1.red = png_gamma_correct(png_ptr,
+                  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.green, g);
-               png_ptr->background_1.green = png_gamma_correct(png_ptr,
+                  png_ptr->background_1.blue = png_gamma_correct(png_ptr,
-                   png_ptr->background.green, g);
+                      png_ptr->background.blue, g);
+               }
                png_ptr->background_1.blue = png_gamma_correct(png_ptr,
-                   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
-            else
+                   = png_ptr->background_1.blue = png_ptr->background_1.gray;
-               /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
+               png_ptr->background.red = png_ptr->background.green
-               png_ptr->background_1.red = png_ptr->background_1.green
+                   = png_ptr->background.blue = png_ptr->background.gray;
-                   = png_ptr->background_1.blue = png_ptr->background_1.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
-               png_ptr->background.red = png_ptr->background.green
+      /* Transformation does not include PNG_BACKGROUND */
-                   = png_ptr->background.blue = png_ptr->background.gray;
+#endif /* PNG_READ_BACKGROUND_SUPPORTED */
       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
       else
       /* Transformation does not include PNG_BACKGROUND */
-#endif /* PNG_READ_BACKGROUND_SUPPORTED */
+         png_colorp palette = png_ptr->palette;
-      if (color_type == PNG_COLOR_TYPE_PALETTE)
+         int num_palette = png_ptr->num_palette;
          int i;
          png_colorp palette = png_ptr->palette;
-         int num_palette = png_ptr->num_palette;
+         /* NOTE: there are other transformations that should probably be in
-         int i;
+          * 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].green = png_ptr->gamma_table[palette[i].green];
+            palette[i].blue = png_ptr->gamma_table[palette[i].blue];
-            palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+         }
-         }
+         /* Done the gamma correction. */
-         /* Done the gamma correction. */
+         png_ptr->transformations &= ~PNG_GAMMA;
-         png_ptr->transformations &= ~PNG_GAMMA;
+      } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
+   }
 #ifdef PNG_READ_BACKGROUND_SUPPORTED
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   else
                 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) &&
-   if ((png_ptr->transformations & PNG_SHIFT) &&
+      !(png_ptr->transformations & PNG_EXPAND) &&
-       (color_type == PNG_COLOR_TYPE_PALETTE))
+       (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 sg = 8 - png_ptr->sig_bit.green;
-      int sb = 8 - png_ptr->sig_bit.blue;
+      int shift = 8 - png_ptr->sig_bit.red;
+      png_ptr->transformations &= ~PNG_SHIFT;
+      /* significant bits can be in the range 1 to 7 for a meaninful result, if
-      if (sr < 0 || sr > 8)
+       * the number of significant bits is 0 then no shift is done (this is an
+       * error condition which is silently ignored.)
-         sr = 0;
+       */
+      if (shift > 0 && shift < 8)
+         for (i=0; i
+         {
-      if (sg < 0 || sg > 8)
+            int component = png_ptr->palette[i].red;
+            component >>= shift;
-         sg = 0;
+            png_ptr->palette[i].red = (png_byte)component;
+         }
+      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;
+         }
-      if (sb < 0 || sb > 8)
+      shift = 8 - png_ptr->sig_bit.blue;
-         sb = 0;
+      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;
-      }
-   }
-#endif  /* PNG_READ_SHIFT_SUPPORTED */
- }
-#if !defined(PNG_READ_GAMMA_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED) \
- && !defined(PNG_READ_BACKGROUND_SUPPORTED)
+            png_ptr->palette[i].blue = (png_byte)component;
    if (png_ptr)
       return;
-#endif
+#endif  /* PNG_READ_SHIFT_SUPPORTED */
+}
 /* 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)
+   {
-#ifdef PNG_READ_EXPAND_SUPPORTED
+      if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
    if (png_ptr->transformations & PNG_EXPAND)
          /* This check must match what actually happens in
+      }
+   }
 #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
+   /* 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
-   if (png_ptr->transformations & PNG_GAMMA)
+    * sometimes does the gamma transform and cancels the flag.
+    *
+    * 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
-      info_ptr->gamma = png_ptr->gamma;
+    * the info_ptr is used by the app after the rows have been read.
+    */
    info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
 #endif
    if (info_ptr->bit_depth == 16)
+   {
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+#  ifdef PNG_READ_16BIT_SUPPORTED
-#ifdef PNG_READ_16BIT_SUPPORTED
+#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+         if (png_ptr->transformations & PNG_SCALE_16_TO_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;
-   if ((png_ptr->transformations & PNG_16_TO_8) && (info_ptr->bit_depth == 16))
+#     endif
-      info_ptr->bit_depth = 8;
+#  else
-#else
+      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
-   /* Force chopping 16-bit input down to 8 */
+       * the app program can chose if both APIs are available by setting the
+       * 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
-   if (info_ptr->bit_depth == 16)
+          * 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;
+#     else
+#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+            png_ptr->transformations |= PNG_SCALE_16_TO_8;
+            info_ptr->bit_depth = 8;
+#        else
       info_ptr->bit_depth = 8;
             CONFIGURATION ERROR: you must enable at least one 16 to 8 method
+#        endif
+#    endif
-#endif
+#endif /* !READ_16BIT_SUPPORTED */
 #endif
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+   if (png_ptr->transformations & PNG_GRAY_TO_RGB)
-   if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+      info_ptr->color_type = (png_byte)(info_ptr->color_type |
-      info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
+         PNG_COLOR_MASK_COLOR);
+#endif
-#endif
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
-      info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
+         ~PNG_COLOR_MASK_COLOR);
+      }
+   }
 #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
    else
       info_ptr->channels = 1;
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if (png_ptr->transformations & PNG_STRIP_ALPHA)
+   {
-   if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_ALPHA);
+      info_ptr->num_trans = 0;
       info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
 #endif
        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
  * 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
-      char msg[50];
-      png_snprintf2(msg, 50,
+      /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
-          "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
+   }
+   /* 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.
+    */
-#ifdef PNG_WARN_UNINITIALIZED_ROW
+   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");
-#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
+      {
          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));
+                &(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->transformations & PNG_STRIP_ALPHA) &&
+      !(png_ptr->transformations & PNG_COMPOSE) &&
-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
-   if (png_ptr->flags & PNG_FLAG_STRIP_ALPHA)
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
-      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      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,
     * 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_RGB_TO_GRAY_SUPPORTED
+      /* Because RGB_TO_GRAY does the gamma transform. */
+      !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
-   if ((png_ptr->transformations & PNG_GAMMA) &&
+#endif
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
+   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.)
-#ifdef PNG_READ_BACKGROUND_SUPPORTED
+       */
-       !((png_ptr->transformations & PNG_BACKGROUND) &&
+       !((png_ptr->transformations & PNG_COMPOSE) &&
        ((png_ptr->num_trans != 0) ||
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
+#endif
+      /* Because png_init_read_transformations transforms the palette, unless
+       * RGB_TO_GRAY will do the transform.
-#endif
+       */
+       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
+      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 ||
-       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
+/* 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
-      png_do_gamma(&(png_ptr->row_info), png_ptr->row_buf + 1,
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
-          png_ptr->gamma_table, png_ptr->gamma_16_table,
+   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_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.
-#ifdef PNG_READ_16_TO_8_SUPPORTED
+    */
    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 (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->row_info.rowbytes == 0)
+   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
-         png_error(png_ptr, "png_do_quantize returned rowbytes=0");
+       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-   }
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
-#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+#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(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(row_info, png_ptr->row_buf + 1);
-      png_do_unshift(&(png_ptr->row_info), png_ptr->row_buf + 1,
+#endif
           &(png_ptr->shift));
-#endif
+#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
+   /* Added at libpng-1.5.10 */
-#ifdef PNG_READ_PACK_SUPPORTED
+   if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
-   if (png_ptr->transformations & PNG_PACK)
+       png_ptr->num_palette_max >= 0)
-      png_do_unpack(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      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);
-#endif
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+#ifdef PNG_READ_BGR_SUPPORTED
-#endif
+   if (png_ptr->transformations & PNG_BGR)
+      png_do_bgr(row_info, png_ptr->row_buf + 1);
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+#endif
    /* If gray -> RGB, do so now only if we did not do so above */
-   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+#ifdef PNG_READ_PACKSWAP_SUPPORTED
-       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+   if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_packswap(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 color_type;     color type of pixels */
-                /*  png_byte channels;       number of channels (1-4) */
+                /*  png_byte bit_depth;      bit depth of samples */
-                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
-             png_ptr->row_buf + 1);    /* start of pixel data for row */
+                /*  png_byte channels;       number of channels (1-4) */
-#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
+                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
-      if (png_ptr->user_transform_depth)
+             png_ptr->row_buf + 1);    /* start of pixel data for row */
-         png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
+#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
 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;
-      png_uint_16 value = 0;
-      png_uint_32 row_width = row_info->width;
+      int bit_depth = row_info->bit_depth;
-      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;
+      }
+      {
+         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
-      for (c = 0; c < channels; c++)
+             * gets ignored here.
-      {
+             */
-         if (shift[c] <= 0)
+            if (shift[c] <= 0 || shift[c] >= bit_depth)
-            shift[c] = 0;
+               shift[c] = 0;
+            else
-         else
+               have_shift = 1;
             value = 1;
+         if (!have_shift)
+            return;
+      }
       if (!value)
+      switch (bit_depth)
+      {
-         return;
+         default:
+         /* Must be 1bpp gray: should not be here! */
-      switch (row_info->bit_depth)
-      {
+            /* NOTREACHED */
-         default:
+            break;
             break;
+         case 2:
-         case 2:
+         /* Must be 2bpp gray */
          /* assert(channels == 1 && shift[0] == 1) */
             png_bytep bp;
-            png_size_t i;
+            png_bytep bp = row;
-            png_size_t istop = row_info->rowbytes;
+            png_bytep bp_end = bp + row_info->rowbytes;
+            while (bp < bp_end)
+            {
-            for (bp = row, i = 0; i < istop; i++)
+               int b = (*bp >> 1) & 0x55;
-            {
-               *bp >>= 1;
+               *bp++ = (png_byte)b;
-               *bp++ &= 0x55;
+            }
-            }
+            break;
+         }
-            break;
+         case 4:
          /* Must be 4bpp gray */
+         /* assert(channels == 1) */
-         case 4:
+         {
             png_bytep bp = row;
-            png_bytep bp = row;
+            png_bytep bp_end = bp + row_info->rowbytes;
-            png_size_t i;
+            int gray_shift = shift[0];
-            png_size_t istop = row_info->rowbytes;
+            int mask =  0xf >> gray_shift;
-            png_byte mask = (png_byte)((((int)0xf0 >> shift[0]) & (int)0xf0) |
+            mask |= mask << 4;
                 (png_byte)((int)0xf >> shift[0]));
+            while (bp < bp_end)
-            for (i = 0; i < istop; i++)
+            {
-            {
+               int b = (*bp >> gray_shift) & mask;
-               *bp >>= shift[0];
+               *bp++ = (png_byte)b;
-               *bp++ &= mask;
+            }
+            break;
+         }
          case 8:
-            break;
+         /* Single byte components, G, GA, RGB, RGBA */
+         {
             png_bytep bp = row;
-         case 8:
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int channel = 0;
-            png_bytep bp = row;
+            while (bp < bp_end)
-            png_uint_32 i;
+            {
-            png_uint_32 istop = row_width * channels;
+               int b = *bp >> shift[channel];
+               if (++channel >= channels)
-            for (i = 0; i < istop; i++)
+                  channel = 0;
-            {
+               *bp++ = (png_byte)b;
+            }
-               *bp++ >>= shift[i%channels];
+            break;
+         }
 #ifdef PNG_READ_16BIT_SUPPORTED
-            break;
+         case 16:
          /* Double byte components, G, GA, RGB, RGBA */
+         {
-#ifdef PNG_READ_16BIT_SUPPORTED
+            png_bytep bp = row;
+   }
+}
 #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_uint_32 i;
+      png_bytep dp = row; /* destination */
-      png_uint_32 istop = row_info->width * row_info->channels;
+      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
-      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
+          * specification) is:
+          *
-       * value, rather than a simple low-byte truncation.
+          *    (V * 255) / 65535
-       *
-       * What the ideal calculation should be:
-       *   *dp = (((((png_uint_32)(*sp) << 8) |
+          *
-       *          (png_uint_32)(*(sp + 1))) * 255 + 127)
-       *          / (png_uint_32)65535L;
+          * This reduces to round(V / 257), or floor((V + 128.5)/257)
-       *
+          *
-       * GRR: no, I think this is what it really should be:
-       *   *dp = (((((png_uint_32)(*sp) << 8) |
+          * Represent V as the two byte value vhi.vlo.  Make a guess that the
-       *           (png_uint_32)(*(sp + 1))) + 128L)
+          * result is the top byte of V, vhi, then the correction to this value
-       *           / (png_uint_32)257L;
+          * is:
-       *
-       * GRR: here's the exact calculation with shifts:
+          *
-       *   temp = (((png_uint_32)(*sp) << 8) |
+          *    error = floor(((V-vhi.vhi) + 128.5) / 257)
-       *           (png_uint_32)(*(sp + 1))) + 128L;
-       *   *dp = (temp - (temp >> 8)) >> 8;
+          *          = floor(((vlo-vhi) + 128.5) / 257)
-       *
+          *
-       * 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) |
-       *          (png_uint_32)((int)(*(sp + 1)) - *sp)) + 128) >> 8;
+          * shift):
+          *
+          *    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:
+          *
-       * What we actually do to avoid extra shifting and conversion:
+          *    (V * 255 + 32895) >> 16
+          */
-       */
+         png_int_32 tmp = *sp++; /* must be signed! */
+         tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
+         *dp++ = (png_byte)tmp;
-         *dp = *sp + ((((int)(*(sp + 1)) - *sp) > 128) ? 1 : 0);
+      }
-#else
+      row_info->bit_depth = 8;
+      row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+      row_info->rowbytes = row_info->width * row_info->channels;
        /* Simply discard the low order byte */
+}
+#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;
+         *dp++ = *sp;
+         sp += 2; /* skip low byte */
 #endif
       row_info->bit_depth = 8;
       row_info->pixel_depth = (png_byte)(8 * row_info->channels);
       row_info->rowbytes = row_info->width * row_info->channels;
                *(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
+ *
+ *  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):
+ *
- *  We approximate this with
+ * 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
+ *
+ *  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().
+ *  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_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+      PNG_CONST png_uint_32 bc = 32768 - rc - gc;
-      png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
-      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 row_width = row_info->width;
       PNG_CONST int have_alpha =
-      if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+      if (row_info->bit_depth == 8)
+      {
+#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
-         if (row_info->bit_depth == 8)
+          * checked the linearized values for equality; this doesn't match
           * the documentation, the original values must be checked.
-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+          */
+         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   = *(sp++);
+               png_byte green = *(sp++);
+               png_byte blue  = *(sp++);
-                  png_byte red   = png_ptr->gamma_to_1[*(sp++)];
+               if (red != green || red != blue)
                   png_byte green = png_ptr->gamma_to_1[*(sp++)];
-                  png_byte blue  = png_ptr->gamma_to_1[*(sp++)];
+                  red = png_ptr->gamma_to_1[red];
                   green = png_ptr->gamma_to_1[green];
-                  if (red != green || red != blue)
+                  blue = png_ptr->gamma_to_1[blue];
+                  rgb_error |= 1;
+                  *(dp++) = png_ptr->gamma_from_1[
+                      (rc*red + gc*green + bc*blue + 16384)>>15];
+               }
+               else
+               {
+                  /* If there is no overall correction the table will not be
+                   * set.
+                   */
-                  {
+                  if (png_ptr->gamma_table != NULL)
-                     rgb_error |= 1;
+                     red = png_ptr->gamma_table[red];
                      *(dp++) = png_ptr->gamma_from_1[
-                         (rc*red + gc*green + bc*blue)>>15];
+                  *(dp++) = red;
+               }
-                  else
+               if (have_alpha)
-                     *(dp++) = *(sp - 1);
+                  *(dp++) = *(sp++);
+            }
+         }
          else
 #endif
             else
-#endif
+            png_bytep sp = row;
             png_bytep dp = row;
-               png_bytep sp = row;
+            png_uint_32 i;
                png_bytep dp = row;
-               for (i = 0; i < row_width; i++)
+            for (i = 0; i < row_width; i++)
+            {
+               png_byte red   = *(sp++);
+               png_byte green = *(sp++);
                png_byte blue  = *(sp++);
                   png_byte red   = *(sp++);
-                  png_byte green = *(sp++);
+               if (red != green || red != blue)
+               {
+                  rgb_error |= 1;
+                  /* NOTE: this is the historical approach which simply
-                  png_byte blue  = *(sp++);
+                   * truncates the results.
                    */
-                  if (red != green || red != blue)
+                  *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+               }
                      rgb_error |= 1;
-                     *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+               else
-                  }
+                  *(dp++) = red;
-                  else
-                     *(dp++) = *(sp - 1);
+               if (have_alpha)
                   *(dp++) = *(sp++);
+            }
+         }
+      }
       else /* RGB bit_depth == 16 */
          else /* RGB bit_depth == 16 */
 #ifdef PNG_READ_GAMMA_SUPPORTED
-#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)
             if (png_ptr->gamma_16_to_1 != NULL &&
-                png_ptr->gamma_16_from_1 != NULL)
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+            for (i = 0; i < row_width; i++)
+            {
+               png_uint_16 red, green, blue, w;
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-               png_bytep sp = row;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
-               png_bytep dp = row;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
                for (i = 0; i < row_width; i++)
                if (red == green && red == blue)
-                         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;
+            png_uint_32 i;
-               for (i = 0; i < row_width; i++)
+            for (i = 0; i < row_width; i++)
+            {
-                  png_uint_16 red, green, blue, gray16;
+               png_uint_16 red, green, blue, gray16;
-                  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 + 16384) >>
-                  gray16  = (png_uint_16)((rc*red + gc*green + bc*blue)>>15);
+);
-                  *(dp++) = (png_byte)((gray16>>8) & 0xff);
+               *(dp++) = (png_byte)((gray16>>8) & 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++)];
+               *(dp++) = (png_byte)(gray16 & 0xff);
-                  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
-            {
-               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);
+               if (have_alpha)
-                  *(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 */
 #endif
 #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
       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
-    , 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_ptr->gamma_from_1;
+   png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
-    png_const_bytep gamma_from_1, png_const_bytep gamma_to_1,
+   png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
-    png_const_uint_16pp gamma_16, png_const_uint_16pp gamma_16_from_1,
+   png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
+   png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
+   int gamma_shift = png_ptr->gamma_shift;
-    png_const_uint_16pp gamma_16_to_1, int gamma_shift
+   int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
-#endif
-    )
+#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");
    if (background != NULL &&
-      (!(row_info->color_type & PNG_COLOR_MASK_ALPHA) ||
+   png_debug(1, "in png_do_compose");
       (row_info->color_type != PNG_COLOR_TYPE_PALETTE && trans_color)))
+   {
       switch (row_info->color_type)
                   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;
                      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));
+                           tmp |= g << shift;
-                           *sp |= (png_byte)(g << shift);
+                           *sp = (png_byte)(tmp & 0xff);
+                        }
                         if (!shift)
+                        {
                      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;
                      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));
+                           tmp |= g << shift;
-                           *sp |= (png_byte)(g << shift);
+                           *sp = (png_byte)(tmp & 0xff);
+                        }
                         if (!shift)
+                        {
                      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 = 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];
+                     }
+                  }
+                  {
                      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;
+               }
                         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)((png_ptr->background.gray >> 8)
-                           *sp = (png_byte)((background->gray >> 8) & 0xff);
+                                & 0xff);
+                           *(sp + 1) = (png_byte)(png_ptr->background.gray
-                           *(sp + 1) = (png_byte)(background->gray & 0xff);
+                                & 0xff);
+                        }
                         else
                         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)((png_ptr->background.gray >> 8)
-                           *sp = (png_byte)((background->gray >> 8) & 0xff);
+                                & 0xff);
+                           *(sp + 1) = (png_byte)(png_ptr->background.gray
-                           *(sp + 1) = (png_byte)(background->gray & 0xff);
+                                & 0xff);
+                        }
+                     }
+                  }
                   break;
+               {
                   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 = 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) */
+            {
                      png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                          + *(sp + 5));
+                     if (r == png_ptr->trans_color.red &&
-                     if (r == trans_color->red && g == trans_color->green &&
+                         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)((png_ptr->background.green >> 8)
-                        *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                                & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                        *(sp + 3) = (png_byte)(background->green & 0xff);
+                                & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                        *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                                & 0xff);
-                        *(sp + 5) = (png_byte)(background->blue & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
                      else
                      png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
                          + *(sp + 5));
+                     if (r == png_ptr->trans_color.red &&
-                     if (r == trans_color->red && g == trans_color->green &&
+                         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)((png_ptr->background.green >> 8)
-                        *(sp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                                & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                        *(sp + 3) = (png_byte)(background->green & 0xff);
+                                & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                        *(sp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                                & 0xff);
-                        *(sp + 5) = (png_byte)(background->blue & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
+                  }
+               }
+            }
                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, png_ptr->background_1.gray);
-                        v = gamma_to_1[*sp];
+                        if (!optimize)
-                        png_composite(w, v, a, background_1->gray);
+                           w = gamma_from_1[w];
-                        *dp = gamma_from_1[w];
+                        *sp = w;
+                     }
+                  }
+               }
                else
-#endif
-               {
+#endif
                   sp = row;
-                  dp = row;
+                  sp = row;
-                  for (i = 0; i < row_width; i++, sp += 2, dp++)
+                  for (i = 0; i < row_width; i++, sp += 2)
-                  {
-                     png_byte a = *(sp + 1);
-                     if (a == 0xff)
-                        *dp = *sp;
+                  {
+                     png_byte a = *(sp + 1);
-#ifdef PNG_READ_GAMMA_SUPPORTED
-                     else if (a == 0)
-                        *dp = (png_byte)background->gray;
-                     else
-                        png_composite(*dp, *sp, a, background_1->gray);
+                     if (a == 0)
                         *sp = (png_byte)png_ptr->background.gray;
 #else
-                     *dp = (png_byte)background->gray;
+                     else if (a < 0xff)
-#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 &&
+#ifdef PNG_READ_GAMMA_SUPPORTED
-                   gamma_16_to_1 != NULL)
+               if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
                    gamma_16_to_1 != NULL)
                   sp = row;
-                  dp = row;
+                  sp = row;
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 2)
+                  for (i = 0; i < row_width; i++, sp += 4)
+                  {
                      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);
-                        *(dp + 1) = (png_byte)(v & 0xff);
+                        png_uint_16 v;
+                        v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+                        *sp = (png_byte)((v >> 8) & 0xff);
-#ifdef PNG_READ_GAMMA_SUPPORTED
+                        *(sp + 1) = (png_byte)(v & 0xff);
                      else if (a == 0)
-#else
                      else
-#endif
+                     else if (a == 0)
+                     {
                         /* Background is already in screen gamma */
-                        *dp = (png_byte)((background->gray >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.gray >> 8)
+                                & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                     }
                         *(dp + 1) = (png_byte)(background->gray & 0xff);
-                     }
+                     else
+                     {
-#ifdef PNG_READ_GAMMA_SUPPORTED
+                        png_uint_16 g, v, w;
-                     else
-                        png_uint_16 g, v, w;
+                        g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
                         png_composite_16(v, g, a, png_ptr->background_1.gray);
-                        g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
+                        if (optimize)
-                        png_composite_16(v, g, a, background_1->gray);
+                           w = v;
-                        w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
+                        else
-                        *dp = (png_byte)((w >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(w & 0xff);
+                           w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
                         *sp = (png_byte)((w >> 8) & 0xff);
-#endif
+                        *(sp + 1) = (png_byte)(w & 0xff);
+                     }
-               }
-               else
-#endif
-               {
-                  sp = row;
+                  }
-                  dp = row;
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 2)
-                  {
                      png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
-                         + *(sp + 3));
+               else
+#endif
+               {
-                     if (a == (png_uint_16)0xffff)
+                  sp = row;
-                        png_memcpy(dp, sp, 2);
+                  for (i = 0; i < row_width; i++, sp += 4)
 #ifdef PNG_READ_GAMMA_SUPPORTED
-                     else if (a == 0)
+                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
-#else
+                         + *(sp + 3));
-                     else
-#endif
+                     if (a == 0)
                      {
-                        *dp = (png_byte)((background->gray >> 8) & 0xff);
+                        *sp = (png_byte)((png_ptr->background.gray >> 8)
-                        *(dp + 1) = (png_byte)(background->gray & 0xff);
                                 & 0xff);
                         *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
 #ifdef PNG_READ_GAMMA_SUPPORTED
                      else
                      else if (a < 0xffff)
                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];
-                        v = gamma_to_1[*sp];
+                        png_composite(w, v, a, png_ptr->background_1.red);
-                        png_composite(w, v, a, background_1->red);
+                        if (!optimize) w = gamma_from_1[w];
-                        *dp = gamma_from_1[w];
+                        *sp = w;
                         v = gamma_to_1[*(sp + 1)];
-                        v = gamma_to_1[*(sp + 1)];
+                        png_composite(w, v, a, png_ptr->background_1.green);
-                        png_composite(w, v, a, background_1->green);
+                        if (!optimize) w = gamma_from_1[w];
+                        *(sp + 1) = w;
                         *(dp + 1) = gamma_from_1[w];
                         v = gamma_to_1[*(sp + 2)];
-                        v = gamma_to_1[*(sp + 2)];
+                        png_composite(w, v, a, png_ptr->background_1.blue);
-                        png_composite(w, v, a, background_1->blue);
+                        if (!optimize) w = gamma_from_1[w];
-                        *(dp + 2) = gamma_from_1[w];
+                        *(sp + 2) = w;
+                     }
+                  }
-               }
-               else
+               }
-#endif
+               else
 #endif
-                  sp = row;
+               {
-                  dp = row;
-                  for (i = 0; i < row_width; i++, sp += 4, dp += 3)
-                  {
-                     png_byte a = *(sp + 3);
-                     if (a == 0xff)
-                     {
-                        *dp = *sp;
+                  sp = row;
-                        *(dp + 1) = *(sp + 1);
+                  for (i = 0; i < row_width; i++, sp += 4)
-                        *(dp + 2) = *(sp + 2);
+                  {
-                     }
+                     png_byte a = *(sp + 3);
-                     else if (a == 0)
+                     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,
                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 */
-                        /* Background is already in screen gamma */
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
-                        *dp = (png_byte)((background->red >> 8) & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
+                                & 0xff);
-                        *(dp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                        *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                                & 0xff);
-                        *(dp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                        *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                                & 0xff);
-                        *(dp + 5) = (png_byte)(background->blue & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
-                     else
+                     else
                      {
+                        png_uint_16 v, w;
-                        png_uint_16 v, w, x;
+                        v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
-                        v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
+                        png_composite_16(w, v, a, png_ptr->background_1.red);
-                        png_composite_16(w, v, a, background_1->red);
+                        if (!optimize)
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >>
+];
+                        *sp = (png_byte)((w >> 8) & 0xff);
-                        x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+                        *(sp + 1) = (png_byte)(w & 0xff);
-                        *dp = (png_byte)((x >> 8) & 0xff);
-                        *(dp + 1) = (png_byte)(x & 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 >>
+];
-                        v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
-                        png_composite_16(w, v, a, background_1->green);
+                        *(sp + 2) = (png_byte)((w >> 8) & 0xff);
-                        x = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+                        *(sp + 3) = (png_byte)(w & 0xff);
                         *(dp + 2) = (png_byte)((x >> 8) & 0xff);
-                        *(dp + 3) = (png_byte)(x & 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);
-                        *(dp + 5) = (png_byte)(x & 0xff);
+                        *(sp + 4) = (png_byte)((w >> 8) & 0xff);
                         *(sp + 5) = (png_byte)(w & 0xff);
+                     }
-               }
-               else
-#endif
-               {
-                  sp = row;
+                  }
                   dp = row;
-                  for (i = 0; i < row_width; i++, sp += 8, dp += 6)
-                  {
+               else
-                     png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
+#endif
+               {
-                         << 8) + (png_uint_16)(*(sp + 7)));
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 8)
+                  {
+                     png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
-                     if (a == (png_uint_16)0xffff)
+                         << 8) + (png_uint_16)(*(sp + 7)));
-                        png_memcpy(dp, sp, 6);
+                     if (a == 0)
+                     {
                         *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
-                     else if (a == 0)
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
                         *(sp + 2) = (png_byte)((png_ptr->background.green >> 8)
-                        *dp = (png_byte)((background->red >> 8) & 0xff);
+                                & 0xff);
-                        *(dp + 1) = (png_byte)(background->red & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green
-                        *(dp + 2) = (png_byte)((background->green >> 8) & 0xff);
+                                & 0xff);
-                        *(dp + 3) = (png_byte)(background->green & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8)
-                        *(dp + 4) = (png_byte)((background->blue >> 8) & 0xff);
+                                & 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);
-                        *(dp + 3) = (png_byte)(v & 0xff);
-                        png_composite_16(v, b, a, background->blue);
-                        *(dp + 4) = (png_byte)((v >> 8) & 0xff);
-                        *(dp + 5) = (png_byte)(v & 0xff);
-                     }
-                  }
-               }
-            }
-            break;
+                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
                         *(sp + 3) = (png_byte)(v & 0xff);
-         default:
+                        png_composite_16(v, b, a, png_ptr->background.blue);
-            break;
+                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
                         *(sp + 5) = (png_byte)(v & 0xff);
+                     }
       if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+               }
          row_info->color_type = (png_byte)(row_info->color_type &
-             ~PNG_COLOR_MASK_ALPHA);
+            break;
-         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);
+         default:
+            break;
+      }
+   }
+}
 #endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
-#endif
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   }
+}
 #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 */
       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;
  * 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;
+   {
       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++)
+               }
                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++)
+                  {
+               }
                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++)
+                  {
             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;
+            }
             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)
             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 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 &&
+   }
+}
 #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)
+{
+      }
+   }
+}
 #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_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);
+         }
+      }

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