I don't know why you would want to force people to do this. There's nothing stopping someone from hand-copying code if you use text, but you're using the wrong format if you encode it as an image. So, as a result, in addition to losing copy+paste (which may be useful for someone who doesn't want to "Learn Python the Hard Way"), you also lose Ctrl + F, and if you're using an animated GIF, you also lose the ability to stop at a specific point or move around.

Overall, I think the right answer is to use the appropriate format and let people sort themselves out.