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

         {
            if (png_ptr->prev_row == NULL)
            {
               png_warning(png_ptr, "Can't add Up filter after starting");
               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                   ~PNG_FILTER_UP);
            }

            else
            {
               png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
                   (png_ptr->rowbytes + 1));
               png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
            }
         }

         if ((png_ptr->do_filter & PNG_FILTER_AVG) != 0 &&
              png_ptr->avg_row == NULL)
         {
            if (png_ptr->prev_row == NULL)
            {
               png_warning(png_ptr, "Can't add Average filter after starting");
               png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                   ~PNG_FILTER_AVG);
            }

            else
            {
               png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
                   (png_ptr->rowbytes + 1));
               png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
            }
         }

         if ((png_ptr->do_filter & PNG_FILTER_PAETH) != 0 &&
             png_ptr->paeth_row == NULL)
         {
            if (png_ptr->prev_row == NULL)
            {
               png_warning(png_ptr, "Can't add Paeth filter after starting");
               png_ptr->do_filter &= (png_byte)(~PNG_FILTER_PAETH);
            }

            else
            {
               png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
                   (png_ptr->rowbytes + 1));
               png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
            }
         }

         if (png_ptr->do_filter == PNG_NO_FILTERS)
#endif /* WRITE_FILTER */
            png_ptr->do_filter = PNG_FILTER_NONE;
      }
   }
   else
      png_error(png_ptr, "Unknown custom filter method");
}

/* This allows us to influence the way in which libpng chooses the "best"
 * filter for the current scanline.  While the "minimum-sum-of-absolute-
 * differences metric is relatively fast and effective, there is some
 * question as to whether it can be improved upon by trying to keep the
 * filtered data going to zlib more consistent, hopefully resulting in
 * better compression.
 */
#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
/* Convenience reset API. */
static void
png_reset_filter_heuristics(png_structrp png_ptr)
{
   /* Clear out any old values in the 'weights' - this must be done because if
    * the app calls set_filter_heuristics multiple times with different
    * 'num_weights' values we would otherwise potentially have wrong sized
    * arrays.
    */
   png_ptr->num_prev_filters = 0;
   png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_UNWEIGHTED;
   if (png_ptr->prev_filters != NULL)
   {
      png_bytep old = png_ptr->prev_filters;
      png_ptr->prev_filters = NULL;
      png_free(png_ptr, old);
   }
   if (png_ptr->filter_weights != NULL)
   {
      png_uint_16p old = png_ptr->filter_weights;
      png_ptr->filter_weights = NULL;
      png_free(png_ptr, old);
   }

   if (png_ptr->inv_filter_weights != NULL)
   {
      png_uint_16p old = png_ptr->inv_filter_weights;
      png_ptr->inv_filter_weights = NULL;
      png_free(png_ptr, old);
   }

   /* Leave the filter_costs - this array is fixed size. */
}

static int
png_init_filter_heuristics(png_structrp png_ptr, int heuristic_method,
   int num_weights)
{
   if (png_ptr == NULL)
      return 0;

   /* Clear out the arrays */
   png_reset_filter_heuristics(png_ptr);

   /* Check arguments; the 'reset' function makes the correct settings for the
    * unweighted case, but we must handle the weight case by initializing the
    * arrays for the caller.
    */
   if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
   {
      int i;

      if (num_weights > 0)