protected function getCacheId(ImagePathInterface $path) {
        if ($cid = $this->getOption('cache_prefix')) {
            $cid .= DIRECTORY_SEPARATOR;
        }
        $cid .= $path->getPath();
        if ($sanitizer = $this->getOption('cache_id_sanitizer')) {
            $cid = call_user_func($sanitizer, $cid);
        }
        return $cid;
    }