It's a color picker from any UIView, Instagram-like color picker. - Swift 5.2

INSColorPickerView.swift

import UIKit

private var INSColorPickerWindow: UIWindow?

class INSColorPickerView: UIViewController {
    
    private var screenshotForCollectionViewAsImage: UIImage?
    private var completion: ((UIColor) -> Void)?
    
    private let penView = UIView()
    private let pen = UIImageView()
    private let penBg = UIView()
    private let penPoint = UIView()
    
    
    public static func show(screenshot: UIImage?, completion: @escaping (UIColor) -> Void) {
        let vc = INSColorPickerView()
        vc.screenshotForCollectionViewAsImage = screenshot
        vc.completion = completion
        if INSColorPickerWindow == nil {
            INSColorPickerWindow = UIWindow(frame: UIScreen.main.bounds)
        }
        INSColorPickerWindow?.rootViewController = vc
        INSColorPickerWindow?.windowLevel = UIWindow.Level.alert
        INSColorPickerWindow?.makeKeyAndVisible()
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setupViews()
    }
    
    private func setupViews() {
        view.backgroundColor = UIColor.black
        
        let imageView = UIImageView()
        imageView.image = screenshotForCollectionViewAsImage
        imageView.contentMode = .scaleAspectFill
        view.addSubview(imageView)
        imageView.snp.makeConstraints {
            $0.edges.equalToSuperview()
        }
        
        let penW: CGFloat = 120
        let penH: CGFloat = 120
        let penX: CGFloat = (view.bounds.size.width - penW) / 2
        let penY: CGFloat = (view.bounds.size.width - penW) / 2
        penView.frame = CGRect(x: penX, y: penY, width: penW, height: penH)
        view.addSubview(penView)
        penView.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(willDragPenView(_:))))
        
        penBg.backgroundColor = UIColor.clear
        penView.addSubview(penBg)
        penBg.snp.makeConstraints {
            $0.top.equalToSuperview()
            $0.centerX.equalToSuperview()
            $0.width.equalTo(88)
            $0.height.equalTo(95)
        }
        
        pen.image = UIImage(named: "colorpicker-pen")
        penBg.addSubview(pen)
        pen.snp.makeConstraints {
            $0.top.equalTo(12)
            $0.left.equalTo(1.0)
            $0.right.equalTo(-1.0)
            $0.height.equalTo(84)
        }
        
        penPoint.backgroundColor = UIColor.white
        penPoint.layer.borderWidth = 0.5
        penPoint.layer.borderColor = UIColor.white.cgColor
        penPoint.layer.cornerRadius = 6
        penView.addSubview(penPoint)
        penPoint.snp.makeConstraints {
            $0.centerX.equalToSuperview()
            $0.bottom.equalToSuperview()
            $0.width.height.equalTo(12)
        }
    }
    
    @objc private func willDragPenView(_ gesture: UIPanGestureRecognizer) {
        // 1.drag pentView to anywhere by your finger moving
        guard let theView = gesture.view else { return }
        let translation = gesture.translation(in: self.view)
        gesture.view?.center = CGPoint(x: theView.center.x + translation.x, y: theView.center.y + translation.y)
        gesture.setTranslation(CGPoint(), in: self.view)
        
        // 2.Extract the point of center in the bottom of penView variable
        var point = penView.frame.origin
        point.x = point.x + penView.frame.size.width / 2
        point.y = penView.frame.origin.y + penView.frame.size.height
        
        // 3.Get the color of CGPoint {x, y}  
        let color = self.view.getColourFromPoint(point: point)
        penPoint.backgroundColor = color
        
        // 4.As we use BezierPath to create a custom shape, and fill the color to the area that BezierPath goes through it
        penBg.InsColorPickerShape(with: color)
        
        if gesture.state == .ended {
            completion?(color)
            INSColorPickerWindow?.removeFromSuperview()
            INSColorPickerWindow = nil
        }
    }
    
    deinit {
        print("\(self) deinit")
    }

}


extension UIView {
    
    // Reference Doc: https://www.appcoda.com/bezier-paths-introduction/
    // This function returns a shape just as follow
    func InsColorPickerShape(with color: UIColor) {
        /*
          The function draw the shape as follows:
           *****
          *     *
         *       *
         *       *
         *       *
          *     *
           *   *
             *
         
          The degress of a Circle
                 270
             180     0
                 90
         */
        let width: CGFloat = self.frame.size.width
        let height: CGFloat = self.frame.size.height
        let path = UIBezierPath()
        path.addArc(withCenter: CGPoint(x: width / 2, y: height / 2),
                    radius: 35,
                    startAngle: CGFloat(270.0).toRadians(),
                    endAngle: CGFloat(150.0).toRadians(),
                    clockwise: false)
        path.addLine(to: CGPoint(x: width / 2, y: height))
        path.addLine(to: CGPoint(x: width - 9, y: height / 2 + 13))
        path.addArc(withCenter: CGPoint(x: width / 2, y: height / 2),
                    radius: 35,
                    startAngle: CGFloat(30.0).toRadians(),
                    endAngle: CGFloat(270.0).toRadians(),
                    clockwise: false)
        path.close()
        
        let shapeLayer = CAShapeLayer()
        shapeLayer.path = path.cgPath
     
        self.backgroundColor = color
        self.layer.mask = shapeLayer
    }
    
}
 

extension CGFloat {
    
  /**
   * Converts an angle in degrees to radians.
   */
  func toRadians() -> CGFloat {
    return self * .pi / 180
  }
    
}

Call the function

INSColorPickerView.show(screenshot: self.screenshotForCollectionViewAsImage) { (suckedColor) in
               
}

The function self.view.getColourFromPoint(point: point) is here.

The variable screenshotForCollectionViewAsImage comes from here.