我怎样才能调整UIImage的大小，因为它变得更加失真？

Question

我在UIImageView中出现了动态扭曲的UIImage（基本上用函数更新了UIImageView的图像）。每次我根据失真和触摸响应尝试裁剪图像时，我都会收到一个致命的错误 - 尝试用nil展开一个可选的回复。

有什么想法吗？

    func pincushionDistortionWithAmount(amount:CGFloat, position:CGPoint){

    //1 Remove All Subviews
    for view in subviews {
        view.removeFromSuperview()
    }

    //2
    let beginImage = CIImage(image: UIImageView.image)

    // 3
    let filter :CIFilter = CIFilter(name: "CIBumpDistortion")!
    filter.setValue(beginImage, forKey: kCIInputImageKey)
    filter.setValue(CIVector(x: position.x, y: position.y), forKey:"inputCenter")
    filter.setValue(75, forKey:"inputRadius")
    filter.setValue(-1.0 * amount, forKey:"inputScale")

    // 4
    let newImage:UIImage = UIImage(CIImage: filter.outputImage!)
    let imageViewWidth = pinImageView.frame.size.width
    let imageViewHeight = pinImageView.frame.size.height
    let imageWidth = newImage.size.width
    let imageHeight = newImage.size.height

    if imageWidth > imageViewWidth{
        print("Image is wider than ImageView")
        //Code to crop image to fit in imageView
    }
    if imageHeight > imageViewHeight{
        print("Image is taller than ImageView")
        //Code to crop image to fit in imageView

    }
    UIImageView.image = newImage
    addSubview(UIImageView)
}