How do I make drawn sprite?

How would I make so that the player could draw on a canvas, and then whatever he drew became the image for a already made sprite?

Like where he draws his worst fear and then it attacks him :3

There apparently is a way to take a snapshot of an canvas, or even part of it, and if I have correctly read the manual, that snapshot can then be loaded to Sprite object. I have no idea, how to implement it, though.

Closest thread I found was, unfortunately it has no examples etc.

scirra.com/forum/take-a-snapshot-of-specific-area-of-canvas_topic83441_post486661.html

I haven't used it, but there's also a Canvas plugin. Luk et up im too lazee