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  1.  
  2. /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  3.  *
  4.  * Last changed in libpng 1.6.2 [April 25, 2013]
  5.  * Copyright (c) 1998-2013 Glenn Randers-Pehrson
  6.  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  7.  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  8.  *
  9.  * This code is released under the libpng license.
  10.  * For conditions of distribution and use, see the disclaimer
  11.  * and license in png.h
  12.  */
  13.  
  14. #include "pngpriv.h"
  15.  
  16. #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  17.  
  18. #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  19. /* Turn on BGR-to-RGB mapping */
  20. void PNGAPI
  21. png_set_bgr(png_structrp png_ptr)
  22. {
  23.    png_debug(1, "in png_set_bgr");
  24.  
  25.    if (png_ptr == NULL)
  26.       return;
  27.  
  28.    png_ptr->transformations |= PNG_BGR;
  29. }
  30. #endif
  31.  
  32. #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  33. /* Turn on 16 bit byte swapping */
  34. void PNGAPI
  35. png_set_swap(png_structrp png_ptr)
  36. {
  37.    png_debug(1, "in png_set_swap");
  38.  
  39.    if (png_ptr == NULL)
  40.       return;
  41.  
  42.    if (png_ptr->bit_depth == 16)
  43.       png_ptr->transformations |= PNG_SWAP_BYTES;
  44. }
  45. #endif
  46.  
  47. #if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
  48. /* Turn on pixel packing */
  49. void PNGAPI
  50. png_set_packing(png_structrp png_ptr)
  51. {
  52.    png_debug(1, "in png_set_packing");
  53.  
  54.    if (png_ptr == NULL)
  55.       return;
  56.  
  57.    if (png_ptr->bit_depth < 8)
  58.    {
  59.       png_ptr->transformations |= PNG_PACK;
  60.       png_ptr->usr_bit_depth = 8;
  61.    }
  62. }
  63. #endif
  64.  
  65. #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  66. /* Turn on packed pixel swapping */
  67. void PNGAPI
  68. png_set_packswap(png_structrp png_ptr)
  69. {
  70.    png_debug(1, "in png_set_packswap");
  71.  
  72.    if (png_ptr == NULL)
  73.       return;
  74.  
  75.    if (png_ptr->bit_depth < 8)
  76.       png_ptr->transformations |= PNG_PACKSWAP;
  77. }
  78. #endif
  79.  
  80. #if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
  81. void PNGAPI
  82. png_set_shift(png_structrp png_ptr, png_const_color_8p true_bits)
  83. {
  84.    png_debug(1, "in png_set_shift");
  85.  
  86.    if (png_ptr == NULL)
  87.       return;
  88.  
  89.    png_ptr->transformations |= PNG_SHIFT;
  90.    png_ptr->shift = *true_bits;
  91. }
  92. #endif
  93.  
  94. #if defined(PNG_READ_INTERLACING_SUPPORTED) || \
  95.     defined(PNG_WRITE_INTERLACING_SUPPORTED)
  96. int PNGAPI
  97. png_set_interlace_handling(png_structrp png_ptr)
  98. {
  99.    png_debug(1, "in png_set_interlace handling");
  100.  
  101.    if (png_ptr && png_ptr->interlaced)
  102.    {
  103.       png_ptr->transformations |= PNG_INTERLACE;
  104.       return (7);
  105.    }
  106.  
  107.    return (1);
  108. }
  109. #endif
  110.  
  111. #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
  112. /* Add a filler byte on read, or remove a filler or alpha byte on write.
  113.  * The filler type has changed in v0.95 to allow future 2-byte fillers
  114.  * for 48-bit input data, as well as to avoid problems with some compilers
  115.  * that don't like bytes as parameters.
  116.  */
  117. void PNGAPI
  118. png_set_filler(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
  119. {
  120.    png_debug(1, "in png_set_filler");
  121.  
  122.    if (png_ptr == NULL)
  123.       return;
  124.  
  125.    /* In libpng 1.6 it is possible to determine whether this is a read or write
  126.     * operation and therefore to do more checking here for a valid call.
  127.     */
  128.    if (png_ptr->mode & PNG_IS_READ_STRUCT)
  129.    {
  130. #     ifdef PNG_READ_FILLER_SUPPORTED
  131.          /* On read png_set_filler is always valid, regardless of the base PNG
  132.           * format, because other transformations can give a format where the
  133.           * filler code can execute (basically an 8 or 16-bit component RGB or G
  134.           * format.)
  135.           *
  136.           * NOTE: usr_channels is not used by the read code!  (This has led to
  137.           * confusion in the past.)  The filler is only used in the read code.
  138.           */
  139.          png_ptr->filler = (png_uint_16)filler;
  140. #     else
  141.          png_app_error(png_ptr, "png_set_filler not supported on read");
  142.          PNG_UNUSED(filler) /* not used in the write case */
  143.          return;
  144. #     endif
  145.    }
  146.  
  147.    else /* write */
  148.    {
  149. #     ifdef PNG_WRITE_FILLER_SUPPORTED
  150.          /* On write the usr_channels parameter must be set correctly at the
  151.           * start to record the number of channels in the app-supplied data.
  152.           */
  153.          switch (png_ptr->color_type)
  154.          {
  155.             case PNG_COLOR_TYPE_RGB:
  156.                png_ptr->usr_channels = 4;
  157.                break;
  158.  
  159.             case PNG_COLOR_TYPE_GRAY:
  160.                if (png_ptr->bit_depth >= 8)
  161.                {
  162.                   png_ptr->usr_channels = 2;
  163.                   break;
  164.                }
  165.  
  166.                else
  167.                {
  168.                   /* There simply isn't any code in libpng to strip out bits
  169.                    * from bytes when the components are less than a byte in
  170.                    * size!
  171.                    */
  172.                   png_app_error(png_ptr,
  173.                      "png_set_filler is invalid for low bit depth gray output");
  174.                   return;
  175.                }
  176.  
  177.             default:
  178.                png_app_error(png_ptr,
  179.                   "png_set_filler: inappropriate color type");
  180.                return;
  181.          }
  182. #     else
  183.          png_app_error(png_ptr, "png_set_filler not supported on write");
  184.          return;
  185. #     endif
  186.    }
  187.  
  188.    /* Here on success - libpng supports the operation, set the transformation
  189.     * and the flag to say where the filler channel is.
  190.     */
  191.    png_ptr->transformations |= PNG_FILLER;
  192.  
  193.    if (filler_loc == PNG_FILLER_AFTER)
  194.       png_ptr->flags |= PNG_FLAG_FILLER_AFTER;
  195.  
  196.    else
  197.       png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;
  198. }
  199.  
  200. /* Added to libpng-1.2.7 */
  201. void PNGAPI
  202. png_set_add_alpha(png_structrp png_ptr, png_uint_32 filler, int filler_loc)
  203. {
  204.    png_debug(1, "in png_set_add_alpha");
  205.  
  206.    if (png_ptr == NULL)
  207.       return;
  208.  
  209.    png_set_filler(png_ptr, filler, filler_loc);
  210.    /* The above may fail to do anything. */
  211.    if (png_ptr->transformations & PNG_FILLER)
  212.       png_ptr->transformations |= PNG_ADD_ALPHA;
  213. }
  214.  
  215. #endif
  216.  
  217. #if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
  218.     defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
  219. void PNGAPI
  220. png_set_swap_alpha(png_structrp png_ptr)
  221. {
  222.    png_debug(1, "in png_set_swap_alpha");
  223.  
  224.    if (png_ptr == NULL)
  225.       return;
  226.  
  227.    png_ptr->transformations |= PNG_SWAP_ALPHA;
  228. }
  229. #endif
  230.  
  231. #if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
  232.     defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
  233. void PNGAPI
  234. png_set_invert_alpha(png_structrp png_ptr)
  235. {
  236.    png_debug(1, "in png_set_invert_alpha");
  237.  
  238.    if (png_ptr == NULL)
  239.       return;
  240.  
  241.    png_ptr->transformations |= PNG_INVERT_ALPHA;
  242. }
  243. #endif
  244.  
  245. #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
  246. void PNGAPI
  247. png_set_invert_mono(png_structrp png_ptr)
  248. {
  249.    png_debug(1, "in png_set_invert_mono");
  250.  
  251.    if (png_ptr == NULL)
  252.       return;
  253.  
  254.    png_ptr->transformations |= PNG_INVERT_MONO;
  255. }
  256.  
  257. /* Invert monochrome grayscale data */
  258. void /* PRIVATE */
  259. png_do_invert(png_row_infop row_info, png_bytep row)
  260. {
  261.    png_debug(1, "in png_do_invert");
  262.  
  263.   /* This test removed from libpng version 1.0.13 and 1.2.0:
  264.    *   if (row_info->bit_depth == 1 &&
  265.    */
  266.    if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
  267.    {
  268.       png_bytep rp = row;
  269.       png_size_t i;
  270.       png_size_t istop = row_info->rowbytes;
  271.  
  272.       for (i = 0; i < istop; i++)
  273.       {
  274.          *rp = (png_byte)(~(*rp));
  275.          rp++;
  276.       }
  277.    }
  278.  
  279.    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
  280.       row_info->bit_depth == 8)
  281.    {
  282.       png_bytep rp = row;
  283.       png_size_t i;
  284.       png_size_t istop = row_info->rowbytes;
  285.  
  286.       for (i = 0; i < istop; i += 2)
  287.       {
  288.          *rp = (png_byte)(~(*rp));
  289.          rp += 2;
  290.       }
  291.    }
  292.  
  293. #ifdef PNG_16BIT_SUPPORTED
  294.    else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
  295.       row_info->bit_depth == 16)
  296.    {
  297.       png_bytep rp = row;
  298.       png_size_t i;
  299.       png_size_t istop = row_info->rowbytes;
  300.  
  301.       for (i = 0; i < istop; i += 4)
  302.       {
  303.          *rp = (png_byte)(~(*rp));
  304.          *(rp + 1) = (png_byte)(~(*(rp + 1)));
  305.          rp += 4;
  306.       }
  307.    }
  308. #endif
  309. }
  310. #endif
  311.  
  312. #ifdef PNG_16BIT_SUPPORTED
  313. #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  314. /* Swaps byte order on 16 bit depth images */
  315. void /* PRIVATE */
  316. png_do_swap(png_row_infop row_info, png_bytep row)
  317. {
  318.    png_debug(1, "in png_do_swap");
  319.  
  320.    if (row_info->bit_depth == 16)
  321.    {
  322.       png_bytep rp = row;
  323.       png_uint_32 i;
  324.       png_uint_32 istop= row_info->width * row_info->channels;
  325.  
  326.       for (i = 0; i < istop; i++, rp += 2)
  327.       {
  328.          png_byte t = *rp;
  329.          *rp = *(rp + 1);
  330.          *(rp + 1) = t;
  331.       }
  332.    }
  333. }
  334. #endif
  335. #endif
  336.  
  337. #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  338. static PNG_CONST png_byte onebppswaptable[256] = {
  339.    0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
  340.    0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
  341.    0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
  342.    0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
  343.    0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
  344.    0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
  345.    0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
  346.    0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
  347.    0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
  348.    0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
  349.    0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
  350.    0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
  351.    0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
  352.    0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
  353.    0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
  354.    0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
  355.    0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
  356.    0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
  357.    0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
  358.    0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
  359.    0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
  360.    0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
  361.    0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
  362.    0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
  363.    0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
  364.    0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
  365.    0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
  366.    0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
  367.    0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
  368.    0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
  369.    0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
  370.    0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
  371. };
  372.  
  373. static PNG_CONST png_byte twobppswaptable[256] = {
  374.    0x00, 0x40, 0x80, 0xC0, 0x10, 0x50, 0x90, 0xD0,
  375.    0x20, 0x60, 0xA0, 0xE0, 0x30, 0x70, 0xB0, 0xF0,
  376.    0x04, 0x44, 0x84, 0xC4, 0x14, 0x54, 0x94, 0xD4,
  377.    0x24, 0x64, 0xA4, 0xE4, 0x34, 0x74, 0xB4, 0xF4,
  378.    0x08, 0x48, 0x88, 0xC8, 0x18, 0x58, 0x98, 0xD8,
  379.    0x28, 0x68, 0xA8, 0xE8, 0x38, 0x78, 0xB8, 0xF8,
  380.    0x0C, 0x4C, 0x8C, 0xCC, 0x1C, 0x5C, 0x9C, 0xDC,
  381.    0x2C, 0x6C, 0xAC, 0xEC, 0x3C, 0x7C, 0xBC, 0xFC,
  382.    0x01, 0x41, 0x81, 0xC1, 0x11, 0x51, 0x91, 0xD1,
  383.    0x21, 0x61, 0xA1, 0xE1, 0x31, 0x71, 0xB1, 0xF1,
  384.    0x05, 0x45, 0x85, 0xC5, 0x15, 0x55, 0x95, 0xD5,
  385.    0x25, 0x65, 0xA5, 0xE5, 0x35, 0x75, 0xB5, 0xF5,
  386.    0x09, 0x49, 0x89, 0xC9, 0x19, 0x59, 0x99, 0xD9,
  387.    0x29, 0x69, 0xA9, 0xE9, 0x39, 0x79, 0xB9, 0xF9,
  388.    0x0D, 0x4D, 0x8D, 0xCD, 0x1D, 0x5D, 0x9D, 0xDD,
  389.    0x2D, 0x6D, 0xAD, 0xED, 0x3D, 0x7D, 0xBD, 0xFD,
  390.    0x02, 0x42, 0x82, 0xC2, 0x12, 0x52, 0x92, 0xD2,
  391.    0x22, 0x62, 0xA2, 0xE2, 0x32, 0x72, 0xB2, 0xF2,
  392.    0x06, 0x46, 0x86, 0xC6, 0x16, 0x56, 0x96, 0xD6,
  393.    0x26, 0x66, 0xA6, 0xE6, 0x36, 0x76, 0xB6, 0xF6,
  394.    0x0A, 0x4A, 0x8A, 0xCA, 0x1A, 0x5A, 0x9A, 0xDA,
  395.    0x2A, 0x6A, 0xAA, 0xEA, 0x3A, 0x7A, 0xBA, 0xFA,
  396.    0x0E, 0x4E, 0x8E, 0xCE, 0x1E, 0x5E, 0x9E, 0xDE,
  397.    0x2E, 0x6E, 0xAE, 0xEE, 0x3E, 0x7E, 0xBE, 0xFE,
  398.    0x03, 0x43, 0x83, 0xC3, 0x13, 0x53, 0x93, 0xD3,
  399.    0x23, 0x63, 0xA3, 0xE3, 0x33, 0x73, 0xB3, 0xF3,
  400.    0x07, 0x47, 0x87, 0xC7, 0x17, 0x57, 0x97, 0xD7,
  401.    0x27, 0x67, 0xA7, 0xE7, 0x37, 0x77, 0xB7, 0xF7,
  402.    0x0B, 0x4B, 0x8B, 0xCB, 0x1B, 0x5B, 0x9B, 0xDB,
  403.    0x2B, 0x6B, 0xAB, 0xEB, 0x3B, 0x7B, 0xBB, 0xFB,
  404.    0x0F, 0x4F, 0x8F, 0xCF, 0x1F, 0x5F, 0x9F, 0xDF,
  405.    0x2F, 0x6F, 0xAF, 0xEF, 0x3F, 0x7F, 0xBF, 0xFF
  406. };
  407.  
  408. static PNG_CONST png_byte fourbppswaptable[256] = {
  409.    0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70,
  410.    0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0,
  411.    0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71,
  412.    0x81, 0x91, 0xA1, 0xB1, 0xC1, 0xD1, 0xE1, 0xF1,
  413.    0x02, 0x12, 0x22, 0x32, 0x42, 0x52, 0x62, 0x72,
  414.    0x82, 0x92, 0xA2, 0xB2, 0xC2, 0xD2, 0xE2, 0xF2,
  415.    0x03, 0x13, 0x23, 0x33, 0x43, 0x53, 0x63, 0x73,
  416.    0x83, 0x93, 0xA3, 0xB3, 0xC3, 0xD3, 0xE3, 0xF3,
  417.    0x04, 0x14, 0x24, 0x34, 0x44, 0x54, 0x64, 0x74,
  418.    0x84, 0x94, 0xA4, 0xB4, 0xC4, 0xD4, 0xE4, 0xF4,
  419.    0x05, 0x15, 0x25, 0x35, 0x45, 0x55, 0x65, 0x75,
  420.    0x85, 0x95, 0xA5, 0xB5, 0xC5, 0xD5, 0xE5, 0xF5,
  421.    0x06, 0x16, 0x26, 0x36, 0x46, 0x56, 0x66, 0x76,
  422.    0x86, 0x96, 0xA6, 0xB6, 0xC6, 0xD6, 0xE6, 0xF6,
  423.    0x07, 0x17, 0x27, 0x37, 0x47, 0x57, 0x67, 0x77,
  424.    0x87, 0x97, 0xA7, 0xB7, 0xC7, 0xD7, 0xE7, 0xF7,
  425.    0x08, 0x18, 0x28, 0x38, 0x48, 0x58, 0x68, 0x78,
  426.    0x88, 0x98, 0xA8, 0xB8, 0xC8, 0xD8, 0xE8, 0xF8,
  427.    0x09, 0x19, 0x29, 0x39, 0x49, 0x59, 0x69, 0x79,
  428.    0x89, 0x99, 0xA9, 0xB9, 0xC9, 0xD9, 0xE9, 0xF9,
  429.    0x0A, 0x1A, 0x2A, 0x3A, 0x4A, 0x5A, 0x6A, 0x7A,
  430.    0x8A, 0x9A, 0xAA, 0xBA, 0xCA, 0xDA, 0xEA, 0xFA,
  431.    0x0B, 0x1B, 0x2B, 0x3B, 0x4B, 0x5B, 0x6B, 0x7B,
  432.    0x8B, 0x9B, 0xAB, 0xBB, 0xCB, 0xDB, 0xEB, 0xFB,
  433.    0x0C, 0x1C, 0x2C, 0x3C, 0x4C, 0x5C, 0x6C, 0x7C,
  434.    0x8C, 0x9C, 0xAC, 0xBC, 0xCC, 0xDC, 0xEC, 0xFC,
  435.    0x0D, 0x1D, 0x2D, 0x3D, 0x4D, 0x5D, 0x6D, 0x7D,
  436.    0x8D, 0x9D, 0xAD, 0xBD, 0xCD, 0xDD, 0xED, 0xFD,
  437.    0x0E, 0x1E, 0x2E, 0x3E, 0x4E, 0x5E, 0x6E, 0x7E,
  438.    0x8E, 0x9E, 0xAE, 0xBE, 0xCE, 0xDE, 0xEE, 0xFE,
  439.    0x0F, 0x1F, 0x2F, 0x3F, 0x4F, 0x5F, 0x6F, 0x7F,
  440.    0x8F, 0x9F, 0xAF, 0xBF, 0xCF, 0xDF, 0xEF, 0xFF
  441. };
  442.  
  443. /* Swaps pixel packing order within bytes */
  444. void /* PRIVATE */
  445. png_do_packswap(png_row_infop row_info, png_bytep row)
  446. {
  447.    png_debug(1, "in png_do_packswap");
  448.  
  449.    if (row_info->bit_depth < 8)
  450.    {
  451.       png_bytep rp;
  452.       png_const_bytep end, table;
  453.  
  454.       end = row + row_info->rowbytes;
  455.  
  456.       if (row_info->bit_depth == 1)
  457.          table = onebppswaptable;
  458.  
  459.       else if (row_info->bit_depth == 2)
  460.          table = twobppswaptable;
  461.  
  462.       else if (row_info->bit_depth == 4)
  463.          table = fourbppswaptable;
  464.  
  465.       else
  466.          return;
  467.  
  468.       for (rp = row; rp < end; rp++)
  469.          *rp = table[*rp];
  470.    }
  471. }
  472. #endif /* PNG_READ_PACKSWAP_SUPPORTED or PNG_WRITE_PACKSWAP_SUPPORTED */
  473.  
  474. #if defined(PNG_WRITE_FILLER_SUPPORTED) || \
  475.     defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
  476. /* Remove a channel - this used to be 'png_do_strip_filler' but it used a
  477.  * somewhat weird combination of flags to determine what to do.  All the calls
  478.  * to png_do_strip_filler are changed in 1.5.2 to call this instead with the
  479.  * correct arguments.
  480.  *
  481.  * The routine isn't general - the channel must be the channel at the start or
  482.  * end (not in the middle) of each pixel.
  483.  */
  484. void /* PRIVATE */
  485. png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
  486. {
  487.    png_bytep sp = row; /* source pointer */
  488.    png_bytep dp = row; /* destination pointer */
  489.    png_bytep ep = row + row_info->rowbytes; /* One beyond end of row */
  490.  
  491.    /* At the start sp will point to the first byte to copy and dp to where
  492.     * it is copied to.  ep always points just beyond the end of the row, so
  493.     * the loop simply copies (channels-1) channels until sp reaches ep.
  494.     *
  495.     * at_start:        0 -- convert AG, XG, ARGB, XRGB, AAGG, XXGG, etc.
  496.     *            nonzero -- convert GA, GX, RGBA, RGBX, GGAA, RRGGBBXX, etc.
  497.     */
  498.  
  499.    /* GA, GX, XG cases */
  500.    if (row_info->channels == 2)
  501.    {
  502.       if (row_info->bit_depth == 8)
  503.       {
  504.          if (at_start) /* Skip initial filler */
  505.             ++sp;
  506.          else          /* Skip initial channel and, for sp, the filler */
  507.             sp += 2, ++dp;
  508.  
  509.          /* For a 1 pixel wide image there is nothing to do */
  510.          while (sp < ep)
  511.             *dp++ = *sp, sp += 2;
  512.  
  513.          row_info->pixel_depth = 8;
  514.       }
  515.  
  516.       else if (row_info->bit_depth == 16)
  517.       {
  518.          if (at_start) /* Skip initial filler */
  519.             sp += 2;
  520.          else          /* Skip initial channel and, for sp, the filler */
  521.             sp += 4, dp += 2;
  522.  
  523.          while (sp < ep)
  524.             *dp++ = *sp++, *dp++ = *sp, sp += 3;
  525.  
  526.          row_info->pixel_depth = 16;
  527.       }
  528.  
  529.       else
  530.          return; /* bad bit depth */
  531.  
  532.       row_info->channels = 1;
  533.  
  534.       /* Finally fix the color type if it records an alpha channel */
  535.       if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
  536.          row_info->color_type = PNG_COLOR_TYPE_GRAY;
  537.    }
  538.  
  539.    /* RGBA, RGBX, XRGB cases */
  540.    else if (row_info->channels == 4)
  541.    {
  542.       if (row_info->bit_depth == 8)
  543.       {
  544.          if (at_start) /* Skip initial filler */
  545.             ++sp;
  546.          else          /* Skip initial channels and, for sp, the filler */
  547.             sp += 4, dp += 3;
  548.  
  549.          /* Note that the loop adds 3 to dp and 4 to sp each time. */
  550.          while (sp < ep)
  551.             *dp++ = *sp++, *dp++ = *sp++, *dp++ = *sp, sp += 2;
  552.  
  553.          row_info->pixel_depth = 24;
  554.       }
  555.  
  556.       else if (row_info->bit_depth == 16)
  557.       {
  558.          if (at_start) /* Skip initial filler */
  559.             sp += 2;
  560.          else          /* Skip initial channels and, for sp, the filler */
  561.             sp += 8, dp += 6;
  562.  
  563.          while (sp < ep)
  564.          {
  565.             /* Copy 6 bytes, skip 2 */
  566.             *dp++ = *sp++, *dp++ = *sp++;
  567.             *dp++ = *sp++, *dp++ = *sp++;
  568.             *dp++ = *sp++, *dp++ = *sp, sp += 3;
  569.          }
  570.  
  571.          row_info->pixel_depth = 48;
  572.       }
  573.  
  574.       else
  575.          return; /* bad bit depth */
  576.  
  577.       row_info->channels = 3;
  578.  
  579.       /* Finally fix the color type if it records an alpha channel */
  580.       if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
  581.          row_info->color_type = PNG_COLOR_TYPE_RGB;
  582.    }
  583.  
  584.    else
  585.       return; /* The filler channel has gone already */
  586.  
  587.    /* Fix the rowbytes value. */
  588.    row_info->rowbytes = dp-row;
  589. }
  590. #endif
  591.  
  592. #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  593. /* Swaps red and blue bytes within a pixel */
  594. void /* PRIVATE */
  595. png_do_bgr(png_row_infop row_info, png_bytep row)
  596. {
  597.    png_debug(1, "in png_do_bgr");
  598.  
  599.    if ((row_info->color_type & PNG_COLOR_MASK_COLOR))
  600.    {
  601.       png_uint_32 row_width = row_info->width;
  602.       if (row_info->bit_depth == 8)
  603.       {
  604.          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
  605.          {
  606.             png_bytep rp;
  607.             png_uint_32 i;
  608.  
  609.             for (i = 0, rp = row; i < row_width; i++, rp += 3)
  610.             {
  611.                png_byte save = *rp;
  612.                *rp = *(rp + 2);
  613.                *(rp + 2) = save;
  614.             }
  615.          }
  616.  
  617.          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
  618.          {
  619.             png_bytep rp;
  620.             png_uint_32 i;
  621.  
  622.             for (i = 0, rp = row; i < row_width; i++, rp += 4)
  623.             {
  624.                png_byte save = *rp;
  625.                *rp = *(rp + 2);
  626.                *(rp + 2) = save;
  627.             }
  628.          }
  629.       }
  630.  
  631. #ifdef PNG_16BIT_SUPPORTED
  632.       else if (row_info->bit_depth == 16)
  633.       {
  634.          if (row_info->color_type == PNG_COLOR_TYPE_RGB)
  635.          {
  636.             png_bytep rp;
  637.             png_uint_32 i;
  638.  
  639.             for (i = 0, rp = row; i < row_width; i++, rp += 6)
  640.             {
  641.                png_byte save = *rp;
  642.                *rp = *(rp + 4);
  643.                *(rp + 4) = save;
  644.                save = *(rp + 1);
  645.                *(rp + 1) = *(rp + 5);
  646.                *(rp + 5) = save;
  647.             }
  648.          }
  649.  
  650.          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
  651.          {
  652.             png_bytep rp;
  653.             png_uint_32 i;
  654.  
  655.             for (i = 0, rp = row; i < row_width; i++, rp += 8)
  656.             {
  657.                png_byte save = *rp;
  658.                *rp = *(rp + 4);
  659.                *(rp + 4) = save;
  660.                save = *(rp + 1);
  661.                *(rp + 1) = *(rp + 5);
  662.                *(rp + 5) = save;
  663.             }
  664.          }
  665.       }
  666. #endif
  667.    }
  668. }
  669. #endif /* PNG_READ_BGR_SUPPORTED or PNG_WRITE_BGR_SUPPORTED */
  670.  
  671. #if defined(PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED) || \
  672.     defined(PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED)
  673. /* Added at libpng-1.5.10 */
  674. void /* PRIVATE */
  675. png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
  676. {
  677.    if (png_ptr->num_palette < (1 << row_info->bit_depth) &&
  678.       png_ptr->num_palette > 0) /* num_palette can be 0 in MNG files */
  679.    {
  680.       /* Calculations moved outside switch in an attempt to stop different
  681.        * compiler warnings.  'padding' is in *bits* within the last byte, it is
  682.        * an 'int' because pixel_depth becomes an 'int' in the expression below,
  683.        * and this calculation is used because it avoids warnings that other
  684.        * forms produced on either GCC or MSVC.
  685.        */
  686.       int padding = (-row_info->pixel_depth * row_info->width) & 7;
  687.       png_bytep rp = png_ptr->row_buf + row_info->rowbytes;
  688.  
  689.       switch (row_info->bit_depth)
  690.       {
  691.          case 1:
  692.          {
  693.             /* in this case, all bytes must be 0 so we don't need
  694.              * to unpack the pixels except for the rightmost one.
  695.              */
  696.             for (; rp > png_ptr->row_buf; rp--)
  697.             {
  698.               if (*rp >> padding != 0)
  699.                  png_ptr->num_palette_max = 1;
  700.               padding = 0;
  701.             }
  702.  
  703.             break;
  704.          }
  705.  
  706.          case 2:
  707.          {
  708.             for (; rp > png_ptr->row_buf; rp--)
  709.             {
  710.               int i = ((*rp >> padding) & 0x03);
  711.  
  712.               if (i > png_ptr->num_palette_max)
  713.                  png_ptr->num_palette_max = i;
  714.  
  715.               i = (((*rp >> padding) >> 2) & 0x03);
  716.  
  717.               if (i > png_ptr->num_palette_max)
  718.                  png_ptr->num_palette_max = i;
  719.  
  720.               i = (((*rp >> padding) >> 4) & 0x03);
  721.  
  722.               if (i > png_ptr->num_palette_max)
  723.                  png_ptr->num_palette_max = i;
  724.  
  725.               i = (((*rp >> padding) >> 6) & 0x03);
  726.  
  727.               if (i > png_ptr->num_palette_max)
  728.                  png_ptr->num_palette_max = i;
  729.  
  730.               padding = 0;
  731.             }
  732.  
  733.             break;
  734.          }
  735.  
  736.          case 4:
  737.          {
  738.             for (; rp > png_ptr->row_buf; rp--)
  739.             {
  740.               int i = ((*rp >> padding) & 0x0f);
  741.  
  742.               if (i > png_ptr->num_palette_max)
  743.                  png_ptr->num_palette_max = i;
  744.  
  745.               i = (((*rp >> padding) >> 4) & 0x0f);
  746.  
  747.               if (i > png_ptr->num_palette_max)
  748.                  png_ptr->num_palette_max = i;
  749.  
  750.               padding = 0;
  751.             }
  752.  
  753.             break;
  754.          }
  755.  
  756.          case 8:
  757.          {
  758.             for (; rp > png_ptr->row_buf; rp--)
  759.             {
  760.                if (*rp > png_ptr->num_palette_max)
  761.                   png_ptr->num_palette_max = (int) *rp;
  762.             }
  763.  
  764.             break;
  765.          }
  766.  
  767.          default:
  768.             break;
  769.       }
  770.    }
  771. }
  772. #endif /* PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED */
  773.  
  774. #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
  775.     defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
  776. #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
  777. void PNGAPI
  778. png_set_user_transform_info(png_structrp png_ptr, png_voidp
  779.    user_transform_ptr, int user_transform_depth, int user_transform_channels)
  780. {
  781.    png_debug(1, "in png_set_user_transform_info");
  782.  
  783.    if (png_ptr == NULL)
  784.       return;
  785.  
  786. #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
  787.    if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
  788.       (png_ptr->flags & PNG_FLAG_ROW_INIT) != 0)
  789.    {
  790.       png_app_error(png_ptr,
  791.             "info change after png_start_read_image or png_read_update_info");
  792.       return;
  793.    }
  794. #endif
  795.  
  796.    png_ptr->user_transform_ptr = user_transform_ptr;
  797.    png_ptr->user_transform_depth = (png_byte)user_transform_depth;
  798.    png_ptr->user_transform_channels = (png_byte)user_transform_channels;
  799. }
  800. #endif
  801.  
  802. /* This function returns a pointer to the user_transform_ptr associated with
  803.  * the user transform functions.  The application should free any memory
  804.  * associated with this pointer before png_write_destroy and png_read_destroy
  805.  * are called.
  806.  */
  807. #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
  808. png_voidp PNGAPI
  809. png_get_user_transform_ptr(png_const_structrp png_ptr)
  810. {
  811.    if (png_ptr == NULL)
  812.       return (NULL);
  813.  
  814.    return png_ptr->user_transform_ptr;
  815. }
  816. #endif
  817.  
  818. #ifdef PNG_USER_TRANSFORM_INFO_SUPPORTED
  819. png_uint_32 PNGAPI
  820. png_get_current_row_number(png_const_structrp png_ptr)
  821. {
  822.    /* See the comments in png.h - this is the sub-image row when reading and
  823.     * interlaced image.
  824.     */
  825.    if (png_ptr != NULL)
  826.       return png_ptr->row_number;
  827.  
  828.    return PNG_UINT_32_MAX; /* help the app not to fail silently */
  829. }
  830.  
  831. png_byte PNGAPI
  832. png_get_current_pass_number(png_const_structrp png_ptr)
  833. {
  834.    if (png_ptr != NULL)
  835.       return png_ptr->pass;
  836.    return 8; /* invalid */
  837. }
  838. #endif /* PNG_USER_TRANSFORM_INFO_SUPPORTED */
  839. #endif /* PNG_READ_USER_TRANSFORM_SUPPORTED ||
  840.           PNG_WRITE_USER_TRANSFORM_SUPPORTED */
  841. #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */
  842.