TestFilterViewController.swift

class TestFilterViewController: UIViewController {
	
	let sepiaSharpenBlurImageView: UIImageView = {
		let v = UIImageView()
		v.contentMode = .scaleAspectFit
		return v
	}()
	
	let sepiaBlurSharpenImageView: UIImageView = {
		let v = UIImageView()
		v.contentMode = .scaleAspectFit
		return v
	}()

	let sepiaSharpenBlurLabel = UILabel()
	let sepiaBlurSharpenLabel = UILabel()
	
	var origImage: UIImage!
	
	override func viewDidLoad() {
		super.viewDidLoad()
		
		guard let img = UIImage(named: "sampleImage") else {
			fatalError("Could not load image!!!")
		}
		origImage = img
		
		let stack = UIStackView()
		stack.axis = .vertical
		stack.distribution = .fill
		stack.spacing = 8
		stack.translatesAutoresizingMaskIntoConstraints = false

		stack.addArrangedSubview(sepiaSharpenBlurLabel)
		stack.addArrangedSubview(sepiaSharpenBlurImageView)
		stack.addArrangedSubview(sepiaBlurSharpenLabel)
		stack.addArrangedSubview(sepiaBlurSharpenImageView)

		let promptLabel = UILabel()
		promptLabel.textAlignment = .center
		promptLabel.text = "Tap Anywhere"
		stack.addArrangedSubview(promptLabel)
		
		view.addSubview(stack)
		
		let g = view.safeAreaLayoutGuide
		NSLayoutConstraint.activate([
			stack.centerXAnchor.constraint(equalTo: g.centerXAnchor),
			stack.centerYAnchor.constraint(equalTo: g.centerYAnchor),

			stack.heightAnchor.constraint(equalTo: g.heightAnchor, multiplier: 0.9),
			sepiaSharpenBlurImageView.widthAnchor.constraint(equalTo: sepiaSharpenBlurImageView.heightAnchor),
			sepiaBlurSharpenImageView.widthAnchor.constraint(equalTo: sepiaBlurSharpenImageView.heightAnchor),
		])

		[sepiaSharpenBlurLabel, sepiaBlurSharpenLabel, promptLabel].forEach {
			$0.setContentCompressionResistancePriority(.required, for: .vertical)
		}
		
		sepiaSharpenBlurImageView.image = origImage
		sepiaBlurSharpenImageView.image = origImage
		
		updateLabels()
	}
	
	var step: Int = 0
	
	func updateLabels() -> Void {
		switch step {
		case 0:
			sepiaSharpenBlurLabel.text = "Orig"
			sepiaBlurSharpenLabel.text = "Orig"
		case 1:
			if let t = sepiaSharpenBlurLabel.text {
				sepiaSharpenBlurLabel.text = t + "; Sepia"
			}
			if let t = sepiaBlurSharpenLabel.text {
				sepiaBlurSharpenLabel.text = t + "; Sepia"
			}
		case 2:
			if let t = sepiaSharpenBlurLabel.text {
				sepiaSharpenBlurLabel.text = t + "; Sharpen"
			}
			if let t = sepiaBlurSharpenLabel.text {
				sepiaBlurSharpenLabel.text = t + "; Blur"
			}
		case 3:
			if let t = sepiaSharpenBlurLabel.text {
				sepiaSharpenBlurLabel.text = t + "; Blur"
			}
			if let t = sepiaBlurSharpenLabel.text {
				sepiaBlurSharpenLabel.text = t + "; Sharpen"
			}
		default:
			()
		}
	}
	override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
		guard let imgA = sepiaBlurSharpenImageView.image,
			  let imgB = sepiaSharpenBlurImageView.image
		else {
			fatalError("Image View has no image!!!!")
		}
		switch step {
		case 0:
			let newImageA = imgA.addSepiaFilter()
			sepiaBlurSharpenImageView.image = newImageA
			let newImageB = imgB.addSepiaFilter()
			sepiaSharpenBlurImageView.image = newImageB
		case 1:
			let newImageA = imgA.addBlur(radius: 20.0)
			sepiaBlurSharpenImageView.image = newImageA
			let newImageB = imgB.adjustSharpness(sharpness: 20.0)
			sepiaSharpenBlurImageView.image = newImageB
		case 2:
			let newImageA = imgA.adjustSharpness(sharpness: 20.0)
			sepiaBlurSharpenImageView.image = newImageA
			let newImageB = imgB.addBlur(radius: 20.0)
			sepiaSharpenBlurImageView.image = newImageB
		default:
			sepiaSharpenBlurImageView.image = origImage
			sepiaBlurSharpenImageView.image = origImage
			step = -1
		}
		step += 1
		updateLabels()
	}
}

extension UIImage {
	
	static let ciContext = CIContext()

	// what is FilterType ??
//	func addFilter(filter: FilterType) -> UIImage {
//		let filter = CIFilter(name: filter.rawValue)
//
//		let ciInput = CIImage(image: self)
//		filter?.setValue(ciInput,
//						 forKey: "inputImage")
//
//		if let ciOutput = filter?.outputImage {
//			if let cgImage = UIImage.ciContext.createCGImage(ciOutput,
//															 from: (ciOutput.extent)){
//				return UIImage(cgImage: cgImage)
//			}
//		}
//
//		return self
//	}

	func addSepiaFilter() -> UIImage {
		let filter = CIFilter(name: "CISepiaTone")
		
		let ciInput = CIImage(image: self)
		filter?.setValue(ciInput,
						 forKey: "inputImage")
		
		if let ciOutput = filter?.outputImage {
			if let cgImage = UIImage.ciContext.createCGImage(ciOutput,
															 from: (ciOutput.extent)){
				return UIImage(cgImage: cgImage)
			}
		}
		
		return self
	}
	
	func addBlur(radius value:Float) -> UIImage {
		let filter = CIFilter(name: "CIBoxBlur")
		
		let ciInput = CIImage(image: self)
		
		filter?.setValue(ciInput,
						 forKey: "inputImage")
		filter?.setValue(value,
						 forKey: "inputRadius")
		
		if let ciOutput = filter?.outputImage, let ciInput = ciInput  {
			
			if let cgImage = UIImage.ciContext.createCGImage(ciOutput,
															 from: (ciInput.extent)){
				return UIImage(cgImage: cgImage)
			}
		}
		
		return self
	}
	
	func adjustSharpness(sharpness value:Float) -> UIImage {
		let filter = CIFilter(name: "CISharpenLuminance")
		
		let ciInput = CIImage(image: self)
		
		filter?.setValue(ciInput,
						 forKey: "inputImage")
		filter?.setValue(value,
						 forKey: "inputSharpness")
		
		if let ciOutput = filter?.outputImage, let ciInput = ciInput  {
			
			if let cgImage = UIImage.ciContext.createCGImage(ciOutput,
															 from: (ciInput.extent)){
				return UIImage(cgImage: cgImage)
			}
		}
		
		return self
	}
	
}