- png_debug(1, "in png_set_filter_heuristics_fixed");
-
- /* The internal API allocates all the arrays and ensures that the elements of
- * those arrays are set to the default value.
- */
- if (png_init_filter_heuristics(png_ptr, heuristic_method, num_weights) == 0)
- return;
-
- /* If using the weighted method copy in the weights. */
- if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
- {
- int i;
- for (i = 0; i < num_weights; i++)
- {
- if (filter_weights[i] <= 0)
- {
- png_ptr->inv_filter_weights[i] =
- png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
- }
-
- else
- {
- png_ptr->inv_filter_weights[i] = (png_uint_16)
- ((PNG_WEIGHT_FACTOR*filter_weights[i]+PNG_FP_HALF)/PNG_FP_1);
-
- png_ptr->filter_weights[i] = (png_uint_16)((PNG_WEIGHT_FACTOR*
- PNG_FP_1+(filter_weights[i]/2))/filter_weights[i]);
- }
- }
-
- /* Here is where we set the relative costs of the different filters. We
- * should take the desired compression level into account when setting
- * the costs, so that Paeth, for instance, has a high relative cost at low
- * compression levels, while it has a lower relative cost at higher
- * compression settings. The filter types are in order of increasing
- * relative cost, so it would be possible to do this with an algorithm.
- */
- for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
- if (filter_costs[i] >= PNG_FP_1)
- {
- png_uint_32 tmp;
-
- /* Use a 32 bit unsigned temporary here because otherwise the
- * intermediate value will be a 32 bit *signed* integer (ANSI rules)
- * and this will get the wrong answer on division.
- */
- tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
- tmp /= filter_costs[i];
-
- png_ptr->inv_filter_costs[i] = (png_uint_16)tmp;
-
- tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;
- tmp /= PNG_FP_1;
-
- png_ptr->filter_costs[i] = (png_uint_16)tmp;
- }
- }