Save a JPG from movie

What I’m looking to do is save out part of a movie as a jpg from the movie itself. We have a movie that allows you to customize images in a canvas area. We would like to save this canvas area out as an image of some sort…preferably a jpg. I’ve done a search and found the drawing api’s but I don’t really see how to make the connection between the save function and the other portion of the project. Any help or direction would be appreciated.