複数パスの図形を反転してマスク

combinationMask.swift

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        view.backgroundColor = .white
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        present(PresentedViewController(), animated: true)
    }

}

class PresentedViewController: UIViewController {
    init() {
        super.init(nibName: nil, bundle: nil)

        modalPresentationStyle = .custom
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.darkGray.withAlphaComponent(0.5)

        let image = UIGraphicsImageRenderer(bounds: view.bounds).image { context in
            for angle: CGFloat in [0, -8, 12] {
                let additional = UIBezierPath(roundedRect: .init(x: -60, y: -60, width: 120, height: 120), cornerRadius: 4)
                additional.apply(CGAffineTransform(rotationAngle: angle))
                additional.apply(CGAffineTransform(translationX: 125 + 60, y: 350 + 60))
                additional.fill()
            }

            context.fill(view.bounds, blendMode: .sourceOut)
        }

        let maskLayer = CALayer()
        maskLayer.contents = image.cgImage
        maskLayer.frame = view.frame

        view.layer.mask = maskLayer
    }
}