How to make an custom button with an self-stretching image?

I slightly remember that there is an class which is capable of stretching an image in such a way, that the first x pixels and the last y pixels won't get stretched.

For example if you have an button image with r开发者_开发问答ound corners, you would want those round corners to stay intact while the middle part of that image gets stretched.

This is a feature of class UIImage itself.

- (UIImage *)stretchableImageWithLeftCapWidth:(NSInteger)leftCapWidth  topCapHeight:(NSInteger)topCapHeight

You can assign the resulting image to the appropriate property of UIButton as required.