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

      png_ptr->transformations |= PNG_COMPOSE;
   }
}

#  ifdef PNG_FLOATING_POINT_SUPPORTED
void PNGAPI
png_set_alpha_mode(png_structrp png_ptr, int mode, double output_gamma)
{
   png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
      output_gamma));
}
#  endif
#endif

#ifdef PNG_READ_QUANTIZE_SUPPORTED
/* 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 * next;
   png_byte left;
   png_byte right;
} png_dsort;
typedef png_dsort *   png_dsortp;
typedef png_dsort * * png_dsortpp;

void PNGAPI
png_set_quantize(png_structrp png_ptr, png_colorp palette,
    int num_palette, int maximum_colors, png_const_uint_16p histogram,
    int full_quantize)
{
   png_debug(1, "in png_set_quantize");

   if (png_rtran_ok(png_ptr, 0) == 0)
      return;

   png_ptr->transformations |= PNG_QUANTIZE;

   if (full_quantize == 0)
   {
      int i;

      png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
          (png_uint_32)(num_palette * (sizeof (png_byte))));
      for (i = 0; i < num_palette; i++)
         png_ptr->quantize_index[i] = (png_byte)i;
   }

   if (num_palette > maximum_colors)
   {
      if (histogram != NULL)
      {
         /* This is easy enough, just throw out the least used colors.
          * Perhaps not the best solution, but good enough.
          */

         int i;

         /* Initialize an array to sort colors */
         png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
             (png_uint_32)(num_palette * (sizeof (png_byte))));

         /* Initialize the quantize_sort array */
         for (i = 0; i < num_palette; i++)
            png_ptr->quantize_sort[i] = (png_byte)i;

         /* Find the least used palette entries by starting a
          * bubble sort, and running it until we have sorted
          * out enough colors.  Note that we don't care about
          * sorting all the colors, just finding which are
          * least used.
          */

         for (i = num_palette - 1; i >= maximum_colors; i--)
         {
            int done; /* To stop early if the list is pre-sorted */
            int j;

            done = 1;
            for (j = 0; j < i; j++)
            {
               if (histogram[png_ptr->quantize_sort[j]]
                   < histogram[png_ptr->quantize_sort[j + 1]])
               {
                  png_byte t;

                  t = png_ptr->quantize_sort[j];
                  png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
                  png_ptr->quantize_sort[j + 1] = t;
                  done = 0;
               }
            }

            if (done != 0)
               break;
         }

         /* Swap the palette around, and set up a table, if necessary */
         if (full_quantize != 0)
         {
            int j = num_palette;

            /* Put all the useful colors within the max, but don't
             * move the others.
             */
            for (i = 0; i < maximum_colors; i++)
            {
               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
               {
                  do
                     j--;
                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);

                  palette[i] = palette[j];