Thanks, this worked well on most canvases, but on larger busier ones I ran into a browser error - failed - network error when trying to download the canvas as a png.

I can get past that error by using code here (Abhinav's answer) (I'm not using fabricjs):
http://stackoverflow.com/questions/37135417/download-canvas-as-png-in-fabric-js-giving-network-error

I found your repo and was hoping it would work as it is cleaner. I glanced at your code and it looked like it was doing somewhat the same thing, not sure what was different/why it didn't work when the other code does.