text: 
  /* pngtrans.c - transforms the data in a row (used by both readers and writers)
   *
   * Last changed in libpng 1.4.6 [ April 8, 2010]
   * Copyright (c) 1998-2011 Glenn Randers-Pehrson
   * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   *
   * This code is released under the libpng license.
   * For conditions of distribution and use, see the disclaimer
   * and license in png.h
   */
  
  #define PNG_NO_PEDANTIC_WARNINGS
  #include "png.h"
  #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
  #include "pngpriv.h"
  
  #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  /* Turn on BGR-to-RGB mapping */
  void PNGAPI
  png_set_bgr(png_structp png_ptr)
  {
     png_debug(1, "in png_set_bgr");
  
     if (png_ptr == NULL)
        return;
     png_ptr->transformations |= PNG_BGR;
  }
  #endif
  
  #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  /* Turn on 16 bit byte swapping */
  void PNGAPI
  png_set_swap(png_structp png_ptr)
  {
     png_debug(1, "in png_set_swap");
  
     if (png_ptr == NULL)
        return;
     if (png_ptr->bit_depth == 16)
        png_ptr->transformations |= PNG_SWAP_BYTES;
  }
  #endif
  
  #if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
  /* Turn on pixel packing */
  void PNGAPI
  png_set_packing(png_structp png_ptr)
  {
     png_debug(1, "in png_set_packing");
  
     if (png_ptr == NULL)
        return;
     if (png_ptr->bit_depth < 8)
     {
        png_ptr->transformations |= PNG_PACK;
        png_ptr->usr_bit_depth = 8;
     }
  }
  #endif
  
  #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  /* Turn on packed pixel swapping */
  void PNGAPI
  png_set_packswap(png_structp png_ptr)
  {
     png_debug(1, "in png_set_packswap");
  
     if (png_ptr == NULL)
        return;
     if (png_ptr->bit_depth < 8)
        png_ptr->transformations |= PNG_PACKSWAP;
  }
  #endif
  
  #if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
  void PNGAPI
  png_set_shift(png_structp png_ptr, png_color_8p true_bits)
  {
     png_debug(1, "in png_set_shift");
  
     if (png_ptr == NULL)
        return;
     png_ptr->transformations |= PNG_SHIFT;
     png_ptr->shift = *true_bits;
  }
  #endif
  
  #if defined(PNG_READ_INTERLACING_SUPPORTED) || \
      defined(PNG_WRITE_INTERLACING_SUPPORTED)
  int PNGAPI
  png_set_interlace_handling(png_structp png_ptr)
  {
     png_debug(1, "in png_set_interlace handling");
  
     if (png_ptr && png_ptr->interlaced)
     {
        png_ptr->transformations |= PNG_INTERLACE;
        return (7);
     }
  
     return (1);
  }
  #endif
  
  #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
  /* Add a filler byte on read, or remove a filler or alpha byte on write.
   * The filler type has changed in v0.95 to allow future 2-byte fillers
   * for 48-bit input data, as well as to avoid problems with some compilers
   * that don't like bytes as parameters.
   */
  void PNGAPI
  png_set_filler(png_structp png_ptr, png_uint_32 filler, int filler_loc)
  {
     png_debug(1, "in png_set_filler");
  
     if (png_ptr == NULL)
        return;
     png_ptr->transformations |= PNG_FILLER;
     png_ptr->filler = (png_uint_16)filler;
     if (filler_loc == PNG_FILLER_AFTER)
        png_ptr->flags |= PNG_FLAG_FILLER_AFTER;
     else
        png_ptr->flags &= ~PNG_FLAG_FILLER_AFTER;
  
     /* This should probably go in the "do_read_filler" routine.
      * I attempted to do that in libpng-1.0.1a but that caused problems
      * so I restored it in libpng-1.0.2a
     */
  
     if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
     {
        png_ptr->usr_channels = 4;
     }
  
     /* Also I added this in libpng-1.0.2a (what happens when we expand
      * a less-than-8-bit grayscale to GA? */
  
     if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY && png_ptr->bit_depth >= 8)
     {
        png_ptr->usr_channels = 2;
     }
  }
  
  /* Added to libpng-1.2.7 */
  void PNGAPI
  png_set_add_alpha(png_structp png_ptr, png_uint_32 filler, int filler_loc)
  {
     png_debug(1, "in png_set_add_alpha");
  
     if (png_ptr == NULL)
        return;
     png_set_filler(png_ptr, filler, filler_loc);
     png_ptr->transformations |= PNG_ADD_ALPHA;
  }
  
  #endif
  
  #if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
      defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
  void PNGAPI
  png_set_swap_alpha(png_structp png_ptr)
  {
     png_debug(1, "in png_set_swap_alpha");
  
     if (png_ptr == NULL)
        return;
     png_ptr->transformations |= PNG_SWAP_ALPHA;
  }
  #endif
  
  #if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
      defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
  void PNGAPI
  png_set_invert_alpha(png_structp png_ptr)
  {
     png_debug(1, "in png_set_invert_alpha");
  
     if (png_ptr == NULL)
        return;
     png_ptr->transformations |= PNG_INVERT_ALPHA;
  }
  #endif
  
  #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
  void PNGAPI
  png_set_invert_mono(png_structp png_ptr)
  {
     png_debug(1, "in png_set_invert_mono");
  
     if (png_ptr == NULL)
        return;
     png_ptr->transformations |= PNG_INVERT_MONO;
  }
  
  /* Invert monochrome grayscale data */
  void /* PRIVATE */
  png_do_invert(png_row_infop row_info, png_bytep row)
  {
     png_debug(1, "in png_do_invert");
  
    /* This test removed from libpng version 1.0.13 and 1.2.0:
     *   if (row_info->bit_depth == 1 &&
     */
     if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
     {
        png_bytep rp = row;
        png_uint_32 i;
        png_uint_32 istop = row_info->rowbytes;
  
        for (i = 0; i < istop; i++)
        {
           *rp = (png_byte)(~(*rp));
           rp++;
        }
     }
     else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
        row_info->bit_depth == 8)
     {
        png_bytep rp = row;
        png_uint_32 i;
        png_uint_32 istop = row_info->rowbytes;
  
        for (i = 0; i < istop; i+=2)
        {
           *rp = (png_byte)(~(*rp));
           rp+=2;
        }
     }
     else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
        row_info->bit_depth == 16)
     {
        png_bytep rp = row;
        png_uint_32 i;
        png_uint_32 istop = row_info->rowbytes;
  
        for (i = 0; i < istop; i+=4)
        {
           *rp = (png_byte)(~(*rp));
           *(rp+1) = (png_byte)(~(*(rp+1)));
           rp+=4;
        }
     }
  }
  #endif
  
  #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  /* Swaps byte order on 16 bit depth images */
  void /* PRIVATE */
  png_do_swap(png_row_infop row_info, png_bytep row)
  {
     png_debug(1, "in png_do_swap");
  
     if (
         row_info->bit_depth == 16)
     {
        png_bytep rp = row;
        png_uint_32 i;
        png_uint_32 istop= row_info->width * row_info->channels;
  
        for (i = 0; i < istop; i++, rp += 2)
        {
           png_byte t = *rp;
           *rp = *(rp + 1);
           *(rp + 1) = t;
        }
     }
  }
  #endif
  
  #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  static PNG_CONST png_byte onebppswaptable[256] = {
     0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
     0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
     0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
     0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
     0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
     0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
     0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
     0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
     0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
     0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
     0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
     0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
     0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
     0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
     0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
     0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
     0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
     0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
     0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
     0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
     0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
     0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
     0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
     0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
     0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
     0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
     0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
     0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
     0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
     0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
     0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
     0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
  };
  
  static PNG_CONST png_byte twobppswaptable[256] = {
     0x00, 0x40, 0x80, 0xC0, 0x10, 0x50, 0x90, 0xD0,
     0x20, 0x60, 0xA0, 0xE0, 0x30, 0x70, 0xB0, 0xF0,
     0x04, 0x44, 0x84, 0xC4, 0x14, 0x54, 0x94, 0xD4,
     0x24, 0x64, 0xA4, 0xE4, 0x34, 0x74, 0xB4, 0xF4,
     0x08, 0x48, 0x88, 0xC8, 0x18, 0x58, 0x98, 0xD8,
     0x28, 0x68, 0xA8, 0xE8, 0x38, 0x78, 0xB8, 0xF8,
     0x0C, 0x4C, 0x8C, 0xCC, 0x1C, 0x5C, 0x9C, 0xDC,
     0x2C, 0x6C, 0xAC, 0xEC, 0x3C, 0x7C, 0xBC, 0xFC,
     0x01, 0x41, 0x81, 0xC1, 0x11, 0x51, 0x91, 0xD1,
     0x21, 0x61, 0xA1, 0xE1, 0x31, 0x71, 0xB1, 0xF1,
     0x05, 0x45, 0x85, 0xC5, 0x15, 0x55, 0x95, 0xD5,
     0x25, 0x65, 0xA5, 0xE5, 0x35, 0x75, 0xB5, 0xF5,
     0x09, 0x49, 0x89, 0xC9, 0x19, 0x59, 0x99, 0xD9,
     0x29, 0x69, 0xA9, 0xE9, 0x39, 0x79, 0xB9, 0xF9,
     0x0D, 0x4D, 0x8D, 0xCD, 0x1D, 0x5D, 0x9D, 0xDD,
     0x2D, 0x6D, 0xAD, 0xED, 0x3D, 0x7D, 0xBD, 0xFD,
     0x02, 0x42, 0x82, 0xC2, 0x12, 0x52, 0x92, 0xD2,
     0x22, 0x62, 0xA2, 0xE2, 0x32, 0x72, 0xB2, 0xF2,
     0x06, 0x46, 0x86, 0xC6, 0x16, 0x56, 0x96, 0xD6,
     0x26, 0x66, 0xA6, 0xE6, 0x36, 0x76, 0xB6, 0xF6,
     0x0A, 0x4A, 0x8A, 0xCA, 0x1A, 0x5A, 0x9A, 0xDA,
     0x2A, 0x6A, 0xAA, 0xEA, 0x3A, 0x7A, 0xBA, 0xFA,
     0x0E, 0x4E, 0x8E, 0xCE, 0x1E, 0x5E, 0x9E, 0xDE,
     0x2E, 0x6E, 0xAE, 0xEE, 0x3E, 0x7E, 0xBE, 0xFE,
     0x03, 0x43, 0x83, 0xC3, 0x13, 0x53, 0x93, 0xD3,
     0x23, 0x63, 0xA3, 0xE3, 0x33, 0x73, 0xB3, 0xF3,
     0x07, 0x47, 0x87, 0xC7, 0x17, 0x57, 0x97, 0xD7,
     0x27, 0x67, 0xA7, 0xE7, 0x37, 0x77, 0xB7, 0xF7,
     0x0B, 0x4B, 0x8B, 0xCB, 0x1B, 0x5B, 0x9B, 0xDB,
     0x2B, 0x6B, 0xAB, 0xEB, 0x3B, 0x7B, 0xBB, 0xFB,
     0x0F, 0x4F, 0x8F, 0xCF, 0x1F, 0x5F, 0x9F, 0xDF,
     0x2F, 0x6F, 0xAF, 0xEF, 0x3F, 0x7F, 0xBF, 0xFF
  };
  
  static PNG_CONST png_byte fourbppswaptable[256] = {
     0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70,
     0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0,
     0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71,
     0x81, 0x91, 0xA1, 0xB1, 0xC1, 0xD1, 0xE1, 0xF1,
     0x02, 0x12, 0x22, 0x32, 0x42, 0x52, 0x62, 0x72,
     0x82, 0x92, 0xA2, 0xB2, 0xC2, 0xD2, 0xE2, 0xF2,
     0x03, 0x13, 0x23, 0x33, 0x43, 0x53, 0x63, 0x73,
     0x83, 0x93, 0xA3, 0xB3, 0xC3, 0xD3, 0xE3, 0xF3,
     0x04, 0x14, 0x24, 0x34, 0x44, 0x54, 0x64, 0x74,
     0x84, 0x94, 0xA4, 0xB4, 0xC4, 0xD4, 0xE4, 0xF4,
     0x05, 0x15, 0x25, 0x35, 0x45, 0x55, 0x65, 0x75,
     0x85, 0x95, 0xA5, 0xB5, 0xC5, 0xD5, 0xE5, 0xF5,
     0x06, 0x16, 0x26, 0x36, 0x46, 0x56, 0x66, 0x76,
     0x86, 0x96, 0xA6, 0xB6, 0xC6, 0xD6, 0xE6, 0xF6,
     0x07, 0x17, 0x27, 0x37, 0x47, 0x57, 0x67, 0x77,
     0x87, 0x97, 0xA7, 0xB7, 0xC7, 0xD7, 0xE7, 0xF7,
     0x08, 0x18, 0x28, 0x38, 0x48, 0x58, 0x68, 0x78,
     0x88, 0x98, 0xA8, 0xB8, 0xC8, 0xD8, 0xE8, 0xF8,
     0x09, 0x19, 0x29, 0x39, 0x49, 0x59, 0x69, 0x79,
     0x89, 0x99, 0xA9, 0xB9, 0xC9, 0xD9, 0xE9, 0xF9,
     0x0A, 0x1A, 0x2A, 0x3A, 0x4A, 0x5A, 0x6A, 0x7A,
     0x8A, 0x9A, 0xAA, 0xBA, 0xCA, 0xDA, 0xEA, 0xFA,
     0x0B, 0x1B, 0x2B, 0x3B, 0x4B, 0x5B, 0x6B, 0x7B,
     0x8B, 0x9B, 0xAB, 0xBB, 0xCB, 0xDB, 0xEB, 0xFB,
     0x0C, 0x1C, 0x2C, 0x3C, 0x4C, 0x5C, 0x6C, 0x7C,
     0x8C, 0x9C, 0xAC, 0xBC, 0xCC, 0xDC, 0xEC, 0xFC,
     0x0D, 0x1D, 0x2D, 0x3D, 0x4D, 0x5D, 0x6D, 0x7D,
     0x8D, 0x9D, 0xAD, 0xBD, 0xCD, 0xDD, 0xED, 0xFD,
     0x0E, 0x1E, 0x2E, 0x3E, 0x4E, 0x5E, 0x6E, 0x7E,
     0x8E, 0x9E, 0xAE, 0xBE, 0xCE, 0xDE, 0xEE, 0xFE,
     0x0F, 0x1F, 0x2F, 0x3F, 0x4F, 0x5F, 0x6F, 0x7F,
     0x8F, 0x9F, 0xAF, 0xBF, 0xCF, 0xDF, 0xEF, 0xFF
  };
  
  /* Swaps pixel packing order within bytes */
  void /* PRIVATE */
  png_do_packswap(png_row_infop row_info, png_bytep row)
  {
     png_debug(1, "in png_do_packswap");
  
     if (
         row_info->bit_depth < 8)
     {
        png_bytep rp, end, table;
  
        end = row + row_info->rowbytes;
  
        if (row_info->bit_depth == 1)
           table = (png_bytep)onebppswaptable;
        else if (row_info->bit_depth == 2)
           table = (png_bytep)twobppswaptable;
        else if (row_info->bit_depth == 4)
           table = (png_bytep)fourbppswaptable;
        else
           return;
  
        for (rp = row; rp < end; rp++)
           *rp = table[*rp];
     }
  }
  #endif /* PNG_READ_PACKSWAP_SUPPORTED or PNG_WRITE_PACKSWAP_SUPPORTED */
  
  #if defined(PNG_WRITE_FILLER_SUPPORTED) || \
      defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
  /* Remove filler or alpha byte(s) */
  void /* PRIVATE */
  png_do_strip_filler(png_row_infop row_info, png_bytep row, png_uint_32 flags)
  {
     png_debug(1, "in png_do_strip_filler");
  
     {
        png_bytep sp=row;
        png_bytep dp=row;
        png_uint_32 row_width=row_info->width;
        png_uint_32 i;
  
        if ((row_info->color_type == PNG_COLOR_TYPE_RGB ||
            (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
            (flags & PNG_FLAG_STRIP_ALPHA))) &&
            row_info->channels == 4)
        {
           if (row_info->bit_depth == 8)
           {
              /* This converts from RGBX or RGBA to RGB */
              if (flags & PNG_FLAG_FILLER_AFTER)
              {
                 dp+=3; sp+=4;
                 for (i = 1; i < row_width; i++)
                 {
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    sp++;
                 }
              }
              /* This converts from XRGB or ARGB to RGB */
              else
              {
                 for (i = 0; i < row_width; i++)
                 {
                    sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                 }
              }
              row_info->pixel_depth = 24;
              row_info->rowbytes = row_width * 3;
           }
           else /* if (row_info->bit_depth == 16) */
           {
              if (flags & PNG_FLAG_FILLER_AFTER)
              {
                 /* This converts from RRGGBBXX or RRGGBBAA to RRGGBB */
                 sp += 8; dp += 6;
                 for (i = 1; i < row_width; i++)
                 {
                    /* This could be (although png_memcpy is probably slower):
                    png_memcpy(dp, sp, 6);
                    sp += 8;
                    dp += 6;
                    */
  
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    sp += 2;
                 }
              }
              else
              {
                 /* This converts from XXRRGGBB or AARRGGBB to RRGGBB */
                 for (i = 0; i < row_width; i++)
                 {
                    /* This could be (although png_memcpy is probably slower):
                    png_memcpy(dp, sp, 6);
                    sp += 8;
                    dp += 6;
                    */
  
                    sp+=2;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                 }
              }
              row_info->pixel_depth = 48;
              row_info->rowbytes = row_width * 6;
           }
           row_info->channels = 3;
        }
        else if ((row_info->color_type == PNG_COLOR_TYPE_GRAY ||
           (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
           (flags & PNG_FLAG_STRIP_ALPHA))) &&
            row_info->channels == 2)
        {
           if (row_info->bit_depth == 8)
           {
              /* This converts from GX or GA to G */
              if (flags & PNG_FLAG_FILLER_AFTER)
              {
                 for (i = 0; i < row_width; i++)
                 {
                    *dp++ = *sp++;
                    sp++;
                 }
              }
              /* This converts from XG or AG to G */
              else
              {
                 for (i = 0; i < row_width; i++)
                 {
                    sp++;
                    *dp++ = *sp++;
                 }
              }
              row_info->pixel_depth = 8;
              row_info->rowbytes = row_width;
           }
           else /* if (row_info->bit_depth == 16) */
           {
              if (flags & PNG_FLAG_FILLER_AFTER)
              {
                 /* This converts from GGXX or GGAA to GG */
                 sp += 4; dp += 2;
                 for (i = 1; i < row_width; i++)
                 {
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                    sp += 2;
                 }
              }
              else
              {
                 /* This converts from XXGG or AAGG to GG */
                 for (i = 0; i < row_width; i++)
                 {
                    sp += 2;
                    *dp++ = *sp++;
                    *dp++ = *sp++;
                 }
              }
              row_info->pixel_depth = 16;
              row_info->rowbytes = row_width * 2;
           }
           row_info->channels = 1;
        }
        if (flags & PNG_FLAG_STRIP_ALPHA)
          row_info->color_type &= ~PNG_COLOR_MASK_ALPHA;
     }
  }
  #endif
  
  #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  /* Swaps red and blue bytes within a pixel */
  void /* PRIVATE */
  png_do_bgr(png_row_infop row_info, png_bytep row)
  {
     png_debug(1, "in png_do_bgr");
  
     if (
         (row_info->color_type & PNG_COLOR_MASK_COLOR))
     {
        png_uint_32 row_width = row_info->width;
        if (row_info->bit_depth == 8)
        {
           if (row_info->color_type == PNG_COLOR_TYPE_RGB)
           {
              png_bytep rp;
              png_uint_32 i;
  
              for (i = 0, rp = row; i < row_width; i++, rp += 3)
              {
                 png_byte save = *rp;
                 *rp = *(rp + 2);
                 *(rp + 2) = save;
              }
           }
           else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
           {
              png_bytep rp;
              png_uint_32 i;
  
              for (i = 0, rp = row; i < row_width; i++, rp += 4)
              {
                 png_byte save = *rp;
                 *rp = *(rp + 2);
                 *(rp + 2) = save;
              }
           }
        }
        else if (row_info->bit_depth == 16)
        {
           if (row_info->color_type == PNG_COLOR_TYPE_RGB)
           {
              png_bytep rp;
              png_uint_32 i;
  
              for (i = 0, rp = row; i < row_width; i++, rp += 6)
              {
                 png_byte save = *rp;
                 *rp = *(rp + 4);
                 *(rp + 4) = save;
                 save = *(rp + 1);
                 *(rp + 1) = *(rp + 5);
                 *(rp + 5) = save;
              }
           }
           else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
           {
              png_bytep rp;
              png_uint_32 i;
  
              for (i = 0, rp = row; i < row_width; i++, rp += 8)
              {
                 png_byte save = *rp;
                 *rp = *(rp + 4);
                 *(rp + 4) = save;
                 save = *(rp + 1);
                 *(rp + 1) = *(rp + 5);
                 *(rp + 5) = save;
              }
           }
        }
     }
  }
  #endif /* PNG_READ_BGR_SUPPORTED or PNG_WRITE_BGR_SUPPORTED */
  
  #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
      defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
  void PNGAPI
  png_set_user_transform_info(png_structp png_ptr, png_voidp
     user_transform_ptr, int user_transform_depth, int user_transform_channels)
  {
     png_debug(1, "in png_set_user_transform_info");
  
     if (png_ptr == NULL)
        return;
  #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
     png_ptr->user_transform_ptr = user_transform_ptr;
     png_ptr->user_transform_depth = (png_byte)user_transform_depth;
     png_ptr->user_transform_channels = (png_byte)user_transform_channels;
  #else
     if (user_transform_ptr || user_transform_depth || user_transform_channels)
        png_warning(png_ptr,
          "This version of libpng does not support user transform info");
  #endif
  }
  
  /* This function returns a pointer to the user_transform_ptr associated with
   * the user transform functions.  The application should free any memory
   * associated with this pointer before png_write_destroy and png_read_destroy
   * are called.
   */
  png_voidp PNGAPI
  png_get_user_transform_ptr(png_const_structp png_ptr)
  {
     if (png_ptr == NULL)
        return (NULL);
  #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
     return ((png_voidp)png_ptr->user_transform_ptr);
  #else
     return (NULL);
  #endif
  }
  #endif /* PNG_READ_USER_TRANSFORM_SUPPORTED ||
            PNG_WRITE_USER_TRANSFORM_SUPPORTED */
  #endif /* PNG_READ_SUPPORTED || PNG_WRITE_SUPPORTED */
  