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src/Source/LibPNG/pngrtran.c  view on Meta::CPAN

   }
}
#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.
 */
static void
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
static void
png_do_quantize(png_row_infop row_info, png_bytep row,
    png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
{
   png_bytep sp, dp;
   png_uint_32 i;
   png_uint_32 row_width=row_info->width;

   png_debug(1, "in png_do_quantize");

   if (row_info->bit_depth == 8)
   {
      if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
      {
         int r, g, b, p;
         sp = row;
         dp = row;
         for (i = 0; i < row_width; i++)
         {
            r = *sp++;
            g = *sp++;
            b = *sp++;

            /* This looks real messy, but the compiler will reduce
             * it down to a reasonable formula.  For example, with
             * 5 bits per color, we get:
             * p = (((r >> 3) & 0x1f) << 10) |
             *    (((g >> 3) & 0x1f) << 5) |
             *    ((b >> 3) & 0x1f);
             */
            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                (PNG_QUANTIZE_BLUE_BITS)) |
                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

            *dp++ = palette_lookup[p];
         }

         row_info->color_type = PNG_COLOR_TYPE_PALETTE;
         row_info->channels = 1;
         row_info->pixel_depth = row_info->bit_depth;
         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
      }

      else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
         palette_lookup != NULL)
      {
         int r, g, b, p;
         sp = row;
         dp = row;
         for (i = 0; i < row_width; i++)
         {
            r = *sp++;
            g = *sp++;
            b = *sp++;
            sp++;

            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                (PNG_QUANTIZE_BLUE_BITS)) |
                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

            *dp++ = palette_lookup[p];
         }

         row_info->color_type = PNG_COLOR_TYPE_PALETTE;
         row_info->channels = 1;
         row_info->pixel_depth = row_info->bit_depth;
         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
      }

      else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
         quantize_lookup)
      {
         sp = row;

         for (i = 0; i < row_width; i++, sp++)