Lightweight javascript-based. Convert internal image url to blob url & add watermark.

<h3>Default</h3>
<img class="sample1" data-img2blob="img/1.png" />
<img class="sample1" data-img2blob="img/2.jpg" />
<hr>
<h3>With Watermark</h3>
<img class="sample2" data-img2blob="img/1.png" />
<img class="sample2" data-img2blob="img/2.jpg" />

<script src="https://code.jquery.com/jquery-2.1.3.min.js"></script>
<script src="js/img2blob.js"></script>        
<script>
$(function() {
// default
$(".sample1").img2blob();

// with watermark
$(".sample2").img2blob({
    watermark: '@bachors',
    fontStyle: 'Arial',
    fontSize: '30', // px
    fontColor: '#333', // default 'black'
    fontX: 50, // The x coordinate where to start painting the text
    fontY: 50 // The y coordinate where to start painting the text
});

});
</script>

Result

blob:http://...