如何调整UIButton中的图像大小？

I have this UIButton and an image to fit in. I don't want that the image take all the space inside the button but just a little part of it right in the center, but if I resize the button it will resize the image too. How can I do that, is there an option to set whatever dimension I want independently from the size of the UIButton? Thanks!I have this UIButton and an image to fit in. I