write_unknown_chunks  183 pngwrite.c           write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
write_unknown_chunks  337 pngwrite.c        write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE);
write_unknown_chunks  430 pngwrite.c           write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT);