Wrap tc-lib-barcode library in a Clementine helper, in a way that enables you to override it easyly.
// generate a QRCODE through a resizable SVG with "qrcode" CSS class
echo $this->getHelper('barcode')
->getBarcodeObj('QRCODE', 'hello world');
->getResizableSvgCode('class="qrcode"');// inject class="foo" in the SVG tag
public function getSvgCode()
{
return str_replace('<svg ', '<svg class="foo" ', parent::getSvgCode());
}