PNG_FLAG_ZTXT_CUSTOM_STRATEGY 1508 3rdparty/libpng/pngwrite.c    png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_STRATEGY;
PNG_FLAG_ZTXT_CUSTOM_STRATEGY  862 3rdparty/libpng/pngwutil.c    if (!(png_ptr->flags & PNG_FLAG_ZTXT_CUSTOM_STRATEGY))