void row_fn(png_structp png_ptr, png_bytep new_row, png_uint_32 row_num,
            int pass) {
  APNGFrame* frame = (APNGFrame*)png_get_progressive_ptr(png_ptr);
  png_progressive_combine_row(png_ptr, frame->rows[row_num], new_row);
}
void row_fn(png_structp png_ptr, png_bytep new_row, png_uint_32 row_num,
            int pass) {
  APNGFrame* frame = (APNGFrame*)png_get_progressive_ptr(png_ptr);
  png_progressive_combine_row(png_ptr, frame->rows[row_num], new_row);
}