protected function getThumbFilename($options)
    {
        return 'thumb_'
            .$this->id.'_'
            .$options['width'].'_'.$options['height'].'_'.$options['fit'].'_'
            .substr(md5(serialize(array_except($options, ['width', 'height', 'fit']))), 0, 8).
            '.'.$options['extension'];
    }