protected function getParams()
    {
        $aParams = [];

        if (null !== $this->getSize()) {
            $aParams['s'] = $this->getSize();
        }

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

        if (null !== $this->getMaxRating()) {
            $aParams['r'] = $this->getMaxRating();
        }

        if ($this->forcingDefault()) {
            $aParams['f'] = 'y';
        }

        return (null !== $this->sExtension ? '.'.$this->sExtension : '')
            .(empty($aParams) ? '' : '?'.http_build_query($aParams, '', '&amp;'));
    }