这是swift

override func viewDidLoad() {

super.viewDidLoad()

view.addSubview(tip)

view.addSubview(codeImageView)

}

lazy var tip:UILabel= {

let tip =UILabel(frame:CGRect(x:0, y:64, width:200, height:200))

tip.text="恭喜"

tip.numberOfLines=0

tip.textColor=UIColor.black

tip.textAlignment= .center

tip.font=UIFont.systemFont(ofSize:16);

return tip

}()

lazy var codeImageView:UIImageView= {

let imageView =UIImageView(image:UIImage(named:"front"))

imageView.frame=self.tip.frame

returnimageView

}()

override func touchesMoved(_touches:Set, with event:UIEvent?) {

let touchess = touches as NSSet

let touch:UITouch= touchess.anyObject() as! UITouch

let cententPoint = touch.location(in:codeImageView)

let rect =CGRect(x: cententPoint.x, y: cententPoint.y, width:20, height:20)

UIGraphicsBeginImageContextWithOptions(codeImageView.bounds.size,false,0)

let ref =UIGraphicsGetCurrentContext()

codeImageView.layer.render(in: ref!)

ref!.clear(rect)

let image =UIGraphicsGetImageFromCurrentImageContext()

UIGraphicsEndImageContext()

codeImageView.image= image

}