Animate circular mask of UIImageView in iOS

Question

I am wondering how to animate the scale of a mask on a uiimageview. Example images attached. The gray boxes are the image background of my uiviewcontroller and is not part of th

Answer 1

This works for me for a circular mask animation on a map view, you should be able to replace out the map view with an image view, the mask is an oval around the bounds and animates between being the original size and being inset by 5 points repeatedly:

func setupMapMask() {
    let largeCirclePath = UIBezierPath(ovalInRect: mapView.bounds).CGPath

    let mask = CAShapeLayer()
    mask.path = largeCirclePath
    mask.backgroundColor = UIColor.blackColor().CGColor

    mapView.layer.mask = mask

    let smallCirclePath = UIBezierPath(ovalInRect: CGRectInset(mapView.bounds, 5.0, 5.0)).CGPath

    let anim = CABasicAnimation(keyPath: "path")
    anim.toValue = smallCirclePath
    anim.duration = 0.5
    anim.repeatCount = Float.infinity
    anim.autoreverses = true
    mask.addAnimation(anim, forKey: "path")
}