Custom "resizable image" drawing in iOS

Question

The UIImage API provides methods to resize an image in a way that certain areas get stretched, while others remain unaltered - great for background images for resizable UI elements.

Now I am looking for a way to customize this behavior for more complex background images.

This is what - (UIImage *)resizableImageWithCapInsets:(UIEdgeInsets)capInsets; does. The transparent areas remain unaltered, the red areas are stretched when the view size is changed.

This is what i want - finer grained control over the areas that are stretched:

I guess I'd have to do that by overwriting the -(void)drawRect: method of my UIView subclass and then use Quartz to do the drawing of the image.

I just can't figure out which of the system APIs I would have to use.

Could anybody give me a hint how to accomplish this?

Answer 1

I would just use three separate UIImageViews with resizableImageWithCapInsets inside. You could also so it in drawRect using, for example, CGPattern, but you would have performance issue when scaling the view.