PNG_BACKGROUND_IS_GRAY 1403 3rdparty/libpng/pngrtran.c          png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
PNG_BACKGROUND_IS_GRAY 1418 3rdparty/libpng/pngrtran.c             png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
PNG_BACKGROUND_IS_GRAY 2197 3rdparty/libpng/pngrtran.c        !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
PNG_BACKGROUND_IS_GRAY 2282 3rdparty/libpng/pngrtran.c        (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))