Saving a Canvas dataURL as a .png file (to post on a Facebook wall through an app)

I have a little Facebook application and I would like to be able to post the contents of my canvas onto someone's wall if they so choose after they save their image data.

When the save button is pressed I get a dataURL that contains the image data I would like to post onto the user's wall. I believe the only way to do this would be to save the data as .png and then post this on the wall. I was looking through开发者_C百科 the dataURL documentation and I did not see any way to easily output the dataURL as a .png file so that I can post it. What would be the best way to do this?

Updated with link from udjamaflip's comment:

http://webcache.googleusercontent.com/search?q=cache:W3YaJQJpsqEJ:maran-emil.de/nodes/how-to-convert-canvas-animation-in-hd-avi-video-file+&cd=1&hl=en&ct=clnk&gl=au&client=firefox-a