private function getParams($email)
    {
        $params = $this->cachedParams;

        if (is_null($this->cachedParams)) {
            $params['s'] = $this->getSize();
            $params['r'] = $this->getRating();

            if ($this->getDefaultImage() !== false) {
                $params['d'] = $this->getDefaultImage();
            }

            $this->cachedParams = $params;
        }

        if (empty($email)) {
            $params['f'] = 'y';
        }

        return (array) $params;
    }