如何使用UIViewContentModeAspectFit将图像添加到UIButton？

I add an image file to to UIButton image property. But my image resized and looks ugly. So if I'll added my image to UIImageView, I can set contentMode property to UIViewContentModeAspectFit and image will look nice. But if I'll do the same for UIButton nothing changed.I add an image file to to UIButton image proper