png_set_compression_level  129 contrib/gregbook/writepng.c     png_set_compression_level(png_ptr, Z_BEST_COMPRESSION);
png_set_compression_level 1667 png.h          PNG_EXPORT(69, void, png_set_compression_level, (png_structrp png_ptr,
png_set_compression_level 2276 pngwrite.c           png_set_compression_level(png_ptr, 3);