iphone SDK: How to implement a signature capture?

How can I capture a users signature? The idea is that the user will use their fingers开发者_如何学Go to draw their signature in a box. Part of the saving process will be to write this image to their Photos folder.

I think this will do it.

http://www.ipodtouchfans.com/forums/showthread.php?t=132024

After that, I think the ability to save a screen capture will do the job.

UIGraphicsBeginImageContext(self.view.bounds.size); //self.view.window.frame.size
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);