iPhone SDK:访问索引颜色的PNG图像

guard let image = UIImage(named: "myImage.png") else { return }
let imageView = UIImageView(image: image)
imageView.frame = CGRect(x: 0, y: 0, width: 200, height: 200)
view.addSubview(imageView)

guard let image = CIImage(named: "myImage.png") else { return }
let filter = CIFilter(name: "CIPhotoEffectChrome")!
filter.setValue(image, forKey: kCIInputImageKey)
let outputImage = filter.outputImage
let imageView = UIImageView(image: UIImage(ciImage: outputImage))
imageView.frame = CGRect(x: 0, y: 0, width: 200, height: 200)
view.addSubview(imageView)