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

        if ($rImg) {

            header('Content-Type: image/png');
            imagepng($rImg);
            imagedestroy($rImg);
            exit(0);

        } else {

            return false;
        }
    }