pngrtran.c

一套图像处理程序,支持三种图像文件格式,我调试过了,很好用

      }
   }
}
#endif

#if defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
/* expand grayscale files to rgb, with or without alpha */
void
png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
{
   png_bytep sp, dp;
   png_uint_32 i;

   if (row && row_info && row_info->bit_depth >= 8 &&
      !(row_info->color_type & PNG_COLOR_MASK_COLOR))
   {
      if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
      {
         if (row_info->bit_depth == 8)
         {
            for (i = 0, sp = row + (png_size_t)row_info->width - 1,
               dp = row + (png_size_t)row_info->width * 3 - 1;
               i < row_info->width;
               i++)
            {
               *(dp--) = *sp;
               *(dp--) = *sp;
               *(dp--) = *sp;
               sp--;
            }
         }
         else
         {
            for (i = 0, sp = row + (png_size_t)row_info->width * 2 - 1,
               dp = row + (png_size_t)row_info->width * 6 - 1;
               i < row_info->width;
               i++)
            {
               *(dp--) = *sp;
               *(dp--) = *(sp - 1);
               *(dp--) = *sp;
               *(dp--) = *(sp - 1);
               *(dp--) = *sp;
               *(dp--) = *(sp - 1);
               sp--;
               sp--;
            }
         }
      }
      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
      {
         if (row_info->bit_depth == 8)
         {
            for (i = 0, sp = row + (png_size_t)row_info->width * 2 - 1,
               dp = row + (png_size_t)row_info->width * 4 - 1;
               i < row_info->width;
               i++)
            {
               *(dp--) = *(sp--);
               *(dp--) = *sp;
               *(dp--) = *sp;
               *(dp--) = *sp;
               sp--;
            }
         }
         else
         {
            for (i = 0, sp = row + (png_size_t)row_info->width * 4 - 1,
               dp = row + (png_size_t)row_info->width * 8 - 1;
               i < row_info->width;
               i++)
            {
               *(dp--) = *(sp--);
               *(dp--) = *(sp--);
               *(dp--) = *sp;
               *(dp--) = *(sp - 1);
               *(dp--) = *sp;
               *(dp--) = *(sp - 1);
               *(dp--) = *sp;
               *(dp--) = *(sp - 1);
               sp--;
               sp--;
            }
         }
      }
      row_info->channels += (png_byte)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 = ((row_info->width *
         row_info->pixel_depth + 7) >> 3);
   }
}
#endif

/* 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. */
void
png_build_grayscale_palette(int bit_depth, png_colorp palette)
{
   int num_palette;
   int color_inc;
   int i;
   int v;

   if (!palette)
      return;

   switch (bit_depth)
   {
      case 1:
         num_palette = 2;
         color_inc = 0xff;
         break;
      case 2:
         num_palette = 4;
         color_inc = 0x55;
         break;
      case 4:
         num_palette = 16;
         color_inc = 0x11;
         break;
      case 8:
         num_palette = 256;
         color_inc = 1;
         break;
      default:
         num_palette = 0;
         color_inc = 0;
         break;
   }

   for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
   {
      palette[i].red = (png_byte)v;
      palette[i].green = (png_byte)v;
      palette[i].blue = (png_byte)v;
   }
}

/* This function is currently unused? */
#if defined(PNG_READ_DITHER_SUPPORTED) || defined(PNG_CORRECT_PALETTE_SUPPORTED)
void
png_correct_palette(png_structp png_ptr, png_colorp palette,
   int num_palette)
{
#if defined(PNG_READ_BACKGROUND_SUPPORTED) && defined(PNG_READ_GAMMA_SUPPORTED)
   if ((png_ptr->transformations & (PNG_GAMMA)) &&
      (png_ptr->transformations & (PNG_BACKGROUND)))
   {
      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
         int i;
         png_color back, back_1;

         back.red = png_ptr->gamma_table[png_ptr->background.red];
         back.green = png_ptr->gamma_table[png_ptr->background.green];
         back.blue = png_ptr->gamma_table[png_ptr->background.blue];

         back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
         back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
         back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];

         for (i = 0; i < num_palette; i++)
         {
            if (i < (int)png_ptr->num_trans &&
               png_ptr->trans[i] == 0)
            {
               palette[i] = back;
            }
            else if (i < (int)png_ptr->num_trans &&
               png_ptr->trans[i] != 0xff)
            {
               int v;

               v = png_ptr->gamma_to_1[png_ptr->palette[i].red];
               v = (int)(((png_uint_32)(v) *
                  (png_uint_32)(png_ptr->trans[i]) +
                  (png_uint_32)(back_1.red) *
                  (png_uint_32)(255 - png_ptr->trans[i]) +
                  127) / 255);
               palette[i].red = png_ptr->gamma_from_1[v];

               v = png_ptr->gamma_to_1[png_ptr->palette[i].green];
               v = (int)(((png_uint_32)(v) *
                  (png_uint_32)(png_ptr->trans[i]) +
                  (png_uint_32)(back_1.green) *
                  (png_uint_32)(255 - png_ptr->trans[i]) +
                  127) / 255);
               palette[i].green = png_ptr->gamma_from_1[v];

               v = png_ptr->gamma_to_1[png_ptr->palette[i].blue];
               v = (int)(((png_uint_32)(v) *
                  (png_uint_32)(png_ptr->trans[i]) +
                  (png_uint_32)(back_1.blue) *
                  (png_uint_32)(255 - png_ptr->trans[i]) +
                  127) / 255);
               palette[i].blue = png_ptr->gamma_from_1[v];
            }
            else
            {
               palette[i].red = png_ptr->gamma_table[palette[i].red];
               palette[i].green = png_ptr->gamma_table[palette[i].green];
               palette[i].blue = png_ptr->gamma_table[palette[i].blue];
            }
         }
      }
      else
      {
         int i;
         png_color back;

         back.red = png_ptr->gamma_table[png_ptr->background.red];
         back.green = png_ptr->gamma_table[png_ptr->background.green];
         back.blue = png_ptr->gamma_table[png_ptr->background.blue];

         for (i = 0; i < num_palette; i++)
         {
            if (palette[i].red == png_ptr->trans_values.gray)
            {
               palette[i] = back;
            }
            else
            {
               palette[i].red = png_ptr->gamma_table[palette[i].red];
               palette[i].green = png_ptr->gamma_table[palette[i].green];
               palette[i].blue = png_ptr->gamma_table[palette[i].blue];
            }
         }
      }
   }
   else
#endif
#if defined(PNG_READ_GAMMA_SUPPORTED)
   if (png_ptr->transformations & (PNG_GAMMA))
   {
      int i;

      for (i = 0; i < num_palette; i++)
      {
         palette[i].red = png_ptr->gamma_table[palette[i].red];
         palette[i].green = png_ptr->gamma_table[palette[i].green];
         palette[i].blue = png_ptr->gamma_table[palette[i].blue];
      }
   }
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   else
#endif
#endif
#if defined(PNG_READ_BACKGROUND_SUPPORTED)
   if (png_ptr->transformations & (PNG_BACKGROUND))
   {
      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
         int i;
         png_color back;

         back.red   = (png_byte)png_ptr->background.red;
         back.green = (png_byte)png_ptr->background.green;
         back.blue  = (png_byte)png_ptr->background.blue;

         for (i = 0; i < num_palette; i++)
         {
            if (i >= (int)png_ptr->num_trans ||
               png_ptr->trans[i] == 0)
            {
               palette[i].red = back.red;
               palette[i].green = back.green;
               palette[i].blue = back.blue;
            }
            else if (i < (int)png_ptr->num_trans ||
               png_ptr->trans[i] != 0xff)
            {
               palette[i].red = (png_byte)((
                  (png_uint_32)(png_ptr->palette[i].red) *
                  (png_uint_32)(png_ptr->trans[i]) +
                  (png_uint_32)(back.red) *
                  (png_uint_32)(255 - png_ptr->trans[i]) +
                  127) / 255);
               palette[i].green = (png_byte)((
                  (png_uint_32)(png_ptr->palette[i].green) *
                  (png_uint_32)(png_ptr->trans[i]) +
                  (png_uint_32)(back.green) *
                  (png_uint_32)(255 - png_ptr->trans[i]) +
                  127) / 255);
               palette[i].blue = (png_byte)((
                  (png_uint_32)(png_ptr->palette[i].blue) *
                  (png_uint_32)(png_ptr->trans[i]) +
                  (png_uint_32)(back.blue) *
                  (png_uint_32)(255 - png_ptr->trans[i]) +
                  127) / 255);
            }
         }
      }
      else /* assume grayscale palette (what else could it be?) */
      {
         int i;

         for (i = 0; i < num_palette; i++)
         {
            if (i == (int)png_ptr->trans_values.gray)
            {
               palette[i].red = (png_byte)png_ptr->background.red;
               palette[i].green = (png_byte)png_ptr->background.green;
               palette[i].blue = (png_byte)png_ptr->background.blue;
            }
         }
      }
   }
#endif
}
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED)
/* replace any alpha or transparency with the supplied background color.
   background is the color.  note that paletted files are taken care of
   elsewhere */
void
png_do_background(png_row_infop row_info, png_bytep row,
   png_color_16p trans_values, png_color_16p background,
   png_color_16p background_1,
   png_bytep gamma_table, png_bytep gamma_from_1, png_bytep gamma_to_1,
   png_uint_16pp gamma_16, png_uint_16pp gamma_16_from_1,
   png_uint_16pp gamma_16_to_1, int gamma_shift)
{
   png_bytep sp, dp;
   png_uint_32 i;
   int shift;

   if (row && row_info && background &&
      (!(row_info->color_type & PNG_COLOR_MASK_ALPHA) ||
      (row_info->color_type != PNG_COLOR_TYPE_PALETTE &&
      trans_values)))
   {
      switch (row_info->color_type)
      {
         case PNG_COLOR_TYPE_GRAY:
         {
            switch (row_info->bit_depth)
            {
               case 1:
               {
                  sp = row;
                  shift = 7;
                  for (i = 0; i < row_info->width; i++)
                  {
                     if (((*sp >> shift) & 0x1) ==
                        trans_values->gray)
                     {
                        *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
                        *sp |= (png_byte)(background->gray << shift);
                     }
                     if (!shift)
                     {
                        shift = 7;
                        sp++;
                     }
                     else
                        shift--;
                  }
                  break;
               }
               case 2:
               {
                  sp = row;
                  shift = 6;
                  for (i = 0; i < row_info->width; i++)
                  {
                     if (((*sp >> shift) & 0x3) ==
                        trans_values->gray)
                     {
                        *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
                        *sp |= (png_byte)(background->gray << shift);
                     }
                     if (!shift)
                     {
                        shift = 6;
                        sp++;
                     }
                     else
                        shift -= 2;
                  }
                  break;
               }
               case 4:
               {