PNG_COST_FACTOR  1218 pngwrite.c              png_ptr->filter_costs[i] = PNG_COST_FACTOR;
PNG_COST_FACTOR  1286 pngwrite.c                  (png_uint_16)(PNG_COST_FACTOR / filter_costs[i] + .5);
PNG_COST_FACTOR  1289 pngwrite.c                  (png_uint_16)(PNG_COST_FACTOR * filter_costs[i] + .5);
PNG_COST_FACTOR  1347 pngwrite.c              tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
PNG_COST_FACTOR  1352 pngwrite.c              tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;