如何使相机背景比Swift 5中的rectOfInterest更暗，XCode 11

Question

我正在寻找一个条形码扫描仪应用程序。由于我是Swift和Xcode的新手，所以我设法从其他stackoverflow文章（this和this one）获得帮助，以创建一个页面，我可以在rectOfInterestArea（带角）中扫描条形码，而不是全视角相机。但是我很难使除rectOfInterestArea以外的其他区域变暗。我的整个区域越来越黑。不知道我在做什么错。结果是：

我基本上是想实现类似的东西

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下面是我的代码

import AVFoundation
import UIKit

class TestViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {


    var captureSession: AVCaptureSession!
    var previewLayer: AVCaptureVideoPreviewLayer!
    var rectOfInterestArea = UIView()
    var darkView = UIView()

    var scanRect:CGRect = CGRect(x: 0, y: 0, width: 0, height: 0)
    let metadataOutput = AVCaptureMetadataOutput()


    override func viewDidLoad() {
        super.viewDidLoad()


        captureSession = AVCaptureSession()

        guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
        let videoInput: AVCaptureDeviceInput

        do {
            videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
        } catch {
            return
        }

        if (captureSession.canAddInput(videoInput)) {
            captureSession.addInput(videoInput)
        } else {
            failed()
            return
        }

        if (captureSession.canAddOutput(metadataOutput)) {
            captureSession.addOutput(metadataOutput)

            metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            metadataOutput.metadataObjectTypes = [.qr]
        } else {
            failed()
            return
        }

        let size = 300
        let screenWidth = self.view.frame.size.width
        let xPos = (CGFloat(screenWidth) / CGFloat(2)) - (CGFloat(size) / CGFloat(2))
        scanRect = CGRect(x: Int(xPos), y: 150, width: size, height: size)

        rectOfInterestArea.frame = scanRect

        view.addSubview(rectOfInterestArea)

        print(rectOfInterestArea.frame.size.height, " ", rectOfInterestArea.frame.size.width )

        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        previewLayer.frame = view.layer.bounds
        previewLayer.videoGravity = .resizeAspectFill

        view.layer.addSublayer(previewLayer)

        print(previewLayer.frame.size.height, " ", previewLayer.frame.size.width )

        view.addSubview(rectOfInterestArea)


        captureSession.startRunning()
        metadataOutput.rectOfInterest = previewLayer.metadataOutputRectConverted(fromLayerRect: scanRect)


    }


    func failed() {
        let ac = UIAlertController(title: "Scanning not supported", message: "Your device does not support scanning a code from an item. Please use a device with a camera.", preferredStyle: .alert)
        ac.addAction(UIAlertAction(title: "OK", style: .default))
        present(ac, animated: true)
        captureSession = nil
    }



    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        self.rectOfInterestArea.layer.addSublayer(self.createFrame())
        if (captureSession?.isRunning == false) {
            captureSession.startRunning()
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        if (captureSession?.isRunning == true) {
            captureSession.stopRunning()
        }
    }

    func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
        captureSession.stopRunning()

        if let metadataObject = metadataObjects.first {
            guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
            guard let stringValue = readableObject.stringValue else { return }

            found(code: stringValue)
        }

        dismiss(animated: true)
    }

    func found(code: String) {
        print(code)
    }

    override var prefersStatusBarHidden: Bool {
        return true
    }

    override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
        return .portrait
    }

    func createFrame() -> CAShapeLayer {
        let height: CGFloat = self.rectOfInterestArea.frame.size.height
        let width: CGFloat = self.rectOfInterestArea.frame.size.width
        print(height, " " , width)
        //let h = previewLayer.frame.size.height
        let path = UIBezierPath()
        path.move(to: CGPoint(x: 5, y: 50))
        path.addLine(to: CGPoint(x: 5, y: 5))
        path.addLine(to: CGPoint(x: 50, y: 5))
        path.move(to: CGPoint(x: height - 55, y: 5))
        path.addLine(to: CGPoint(x: height - 5, y: 5))
        path.addLine(to: CGPoint(x: height - 5, y: 55))
        path.move(to: CGPoint(x: 5, y: width - 55))
        path.addLine(to: CGPoint(x: 5, y: width - 5))
        path.addLine(to: CGPoint(x: 55, y: width - 5))
        path.move(to: CGPoint(x: width - 55, y: height - 5))
        path.addLine(to: CGPoint(x: width - 5, y: height - 5))
        path.addLine(to: CGPoint(x: width - 5, y: height - 55))
        let shape = CAShapeLayer()
        shape.path = path.cgPath
        shape.strokeColor = UIColor.white.cgColor
        shape.lineWidth = 5
        shape.fillColor = UIColor.clear.cgColor
        return shape
    }

}

感谢您的任何帮助！

我正在寻找一个条形码扫描仪应用程序。由于我是Swift和Xcode的新手，所以我设法从其他stackoverflow文章（本文）中获得帮助，以创建可以扫描条形码的页面...

Answer 1

let path = CGMutablePath()
path.addRect(bounds)
path.addRect(rectOfInterest)

let maskLayer = CAShapeLayer()
maskLayer.path = path
maskLayer.fillColor = UIColor.black.withAlphaComponent(0.6).cgColor
maskLayer.fillRule = .evenOdd

addSublayer(maskLayer)