set ImageView image
ImageView.transform = ImageView.transform.rotated(by: CGFloat(M_PI_2))
Swift 5
ImageView.transform = ImageView.transform.rotated(by: .pi) // 180˚
ImageView.transform = ImageView.transform.rotated(by: .pi / 2) // 90˚
ImageView.transform = ImageView.transform.rotated(by: .pi * 1.5) // 270˚