public function save($sString, $sPath, $iWidth = null, $iHeight = null)
    {
        $rImg = $this->generateBarcode($sString, $iWidth, $iHeight);

        if ($rImg) {

            imagepng($rImg, $sPath);
            imagedestroy($rImg);

            return true;

        } else {

            return false;
        }
    }