Ratings not visible with existing Exif/XMP tag
gThumb does not recognize the XMP Rating tag, if it is set from command line. I've tried setting Xmp.xmp.Rating with exiv2 and "Rating" from exiftool but gThumb does not show any ratings after that. But if I set the rating from gThumb, it changes that very same tag, but only in this case the rating shows in the application. I have no idea how that is possible, but somehow gThumb reads that tag correctly only if it is set from within.