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
		
	}

}