[onion2k]

Good as html2canvas is, these days you may get more milage creating an SVG, putting the HTML content in it as a ForeignObject, and then using the browser's ability to copy an image to a canvas with the SVG as the source. I use that technique in a very complex diagramming app I work on and it never seems to fail regardless of the HTML content. Getting fonts and external styles to work is fun but that wouldn't apply here.

[xamde]

Off-topic, but please tell us more about the diagramming app.