<link rel="stylesheet" href="libs/magnific/magnific-popup.css">
<script src="libs/magnific/jquery.magnific-popup.js"></script>

$('.gallery').magnificPopup({type: 'image'});

<a class="gallery" href="img/quality-sertificate-1.png">
<img src="img/quality-sertificate-1.png">
</a>