Adding barcode in Event confirmation email
I just found this forum post : https://forum.civicrm.org/index.php?topic=23767.0 which seems to propose a solution based on a old version of CiviCRM but the method is still valid in principle :


either using an existing service on the web (https://developers.google.com/chart/infographics/docs/qr_codes?csw=1) or configure your own that generate a QR code image 
calling the url from within the src image in your template : &lt;img src="https://chart.googleapis.com/chart?cht=qr&amp;chs=120x120&amp;chl={$participantID}&amp;choe=UTF-8" alt="Ticket ID: {$participantID}"&gt;