设置按钮图片的填充模式

一张图片的尺寸比较小,想要填充到一个较大的按钮上,并且按比例填充满按钮.

代码如下:

        let headButton =UIButton()

        headButton.imageView?.contentMode = .scaleAspectFill

        headButton.imageEdgeInsets=UIEdgeInsetsMake(0,0,0,0)

        headButton.contentHorizontalAlignment = .fill

        headButton.contentVerticalAlignment = .fill

        headButton.setImage( imageLiteral(resourceName: "伴游_01"), for: .normal)