使用swift通过图像选择器选择后如何镜像图像？

@IBAction func mirrorBtn(sender: AnyObject){
    self.makeMirroredImage(imageView)
    pickImage.image = imageView

}

func makeMirroredImage(image: UIImage) -> UIImage {
    var flippedOrientation: UIImageOrientation = .UpMirrored
    switch image.imageOrientation {
    case .Down:
        flippedOrientation = .DownMirrored
    case .Left:
        flippedOrientation = .LeftMirrored
    default :
        flippedOrientation = .LeftMirrored
    }

    let flippedImage: UIImage = UIImage(CGImage: image.CGImage!, scale: image.scale, orientation: flippedOrientation)
    return flippedImage
}