[changeImage animation] UIImageView extension to fade in UIImageView new image #swift3 #image #animation #exttension

changeImageAnimation.swift

extension UIImageView {
  func changeImage(to newImage: UIImage?) {
    let crossFade: CABasicAnimation = CABasicAnimation(keyPath: "contents")
    crossFade.duration = 0.2
    crossFade.fromValue = self.image?.cgImage
    crossFade.toValue = newImage?.cgImage
    self.image = newImage
    self.layer.add(crossFade, forKey: "animateContents")
  }
}