public function toObject($dbObject = null, $skip = array())
 {
     if (is_null($dbObject)) {
         return null;
     }
     parent::toObject($dbObject, $skip);
     if ($this->dimensions) {
         $key = $this->dimensions->width . 'x' . $this->dimensions->height;
         $dbObject->setData($key);
     }
     return $dbObject;
 }