public function register(Application $app)
 {
     $app['qrCode'] = $app->protect(function ($text, $size = null) use($app) {
         $default = $app['qr.defaults'];
         $qr = new QrWrapper(new QrCode());
         $qr->setText($text);
         $qr->setPadding($default['padding']);
         $qr->setSize(is_null($size) ? $default['size'] : $size);
         $qr->setImageType($default['imageType']);
         return $qr;
     });
 }