PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS 1536 3rdparty/libpng/pngwrite.c    png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS;
PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS  871 3rdparty/libpng/pngwutil.c    if (!(png_ptr->flags & PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS))