public static function availableSizes() {
            $r = [];
            foreach ((new ReflectionClass(ThumbnailSize::class))->getMethods() as $m) {
                if (preg_match('~^w[0-9]+h[0-9]+$~', $m->getName())) {
                    $r[] = $m->getName();
                }
            };

            return $r;
        }