Combining images to make a UIButton?

If I have one png which is basically a butt开发者_运维问答on image with nothing inside of it:

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|              |
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How do I lay an image onto that, to make the image part of the button, like:

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|    (image)   |
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(I could just lay a UIImageView on top, but that would not inherit button properties, like going dark when pressed)

use the image that is basically a button as the backgroundImage of the UIButton, and use the other image as the image of the UIButton.

[button setImage:[UIImage imageNamed:@"Foo"] forState:UIControlStateNormal];
[button setBackgroundImage:[UIImage imageNamed:@"Bar"] forState:UIControlStateNormal];