CIFilter scaling

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let img = UIImage(named: "sampleImage") else {
            fatalError("Could not load image!!!!")
        }

        /// goal is to scale twice the PIXEL size

        if let scaledImage = imageCIScale(img, dimension: 2.0, outputScale: 1.0) {

            print("original image size:", img.size)
            print("scaled x 2.0 with 1.0 scale:", scaledImage.size)

        }

        if let scaledImage = imageCIScale(img, dimension: 2.0, outputScale: UIScreen.main.scale) {

            print("original image size:", img.size)
            print("scaled x 2.0 with Screen scale:", scaledImage.size)

        }

    }

    func imageCIScale(_ image: UIImage, dimension: CGFloat, outputScale: CGFloat) -> UIImage? {

        guard let ciImage = CIImage(image: image) else {
            print("no ciImage")
            return nil
        }
        guard let scaleFilter = CIFilter(name: "CILanczosScaleTransform") else {
            print("no filter")
            return nil
        }

        scaleFilter.setValue(ciImage, forKey: kCIInputImageKey)

        scaleFilter.setValue(ciImage, forKey: kCIInputImageKey)
        scaleFilter.setValue(dimension, forKey: kCIInputScaleKey)
        scaleFilter.setValue(1.0, forKey: kCIInputAspectRatioKey)

        guard let outputImage = scaleFilter.outputImage else { return nil }

        let uiImage = UIImage(ciImage: outputImage, scale: outputScale, orientation: image.imageOrientation)

        return uiImage

    }

}