获取触摸时像素的颜色

Question

当用户点击摄像机视图上的Point时，我试图获取RGB颜色。我的方法如下：但是，即使我点击相机视图的较亮部分，我也只能获得0,0,0,0。我用来打印的代码是print(color)。

我认为颜色是在sRGB中给出的。

更新：我打印时得到的输出

  

[   （kCGColorSpaceICCBased; kCGColorSpaceModelRGB; sRGB IEC61966-2.1;   扩展范围）]（0 0 0 0）

我该如何解决这个问题？

 override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        let touch = touches.first
        if let point = touch?.location(in: view) {

            let color:CGColor = self.colorOfPoint(point: point)
            print(color)
        }
    }


        func colorOfPoint(point:CGPoint) -> CGColor {

            let pixel = UnsafeMutablePointer<CUnsignedChar>.allocate(capacity: 4)

            let colorSpace = CGColorSpaceCreateDeviceRGB()
            let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)

            let context = CGContext(data: pixel, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

            context!.translateBy(x: -point.x, y: -point.y)



            self.previewLayer.render(in: context!)

            let red: CGFloat   = CGFloat(pixel[0]) / 255.0
            let green: CGFloat = CGFloat(pixel[1]) / 255.0
            let blue: CGFloat  = CGFloat(pixel[2]) / 255.0
            let alpha: CGFloat = CGFloat(pixel[3]) / 255.0

            let color = UIColor(red:red, green: green, blue:blue, alpha:alpha)



            return color.cgColor
        }

更新：2

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {

    let captureSession = AVCaptureSession()
    var previewLayer:CALayer!

    let dataOutput = AVCaptureVideoDataOutput()

    var captureDevice:AVCaptureDevice!

    var takePhoto = false

    override func viewDidLoad() {
        super.viewDidLoad()

        if let availableDevices = AVCaptureDeviceDiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaTypeVideo, position: .back).devices {
                captureDevice = availableDevices.first
                beginSession()
            }

do {
            let captureDeviceInput = try AVCaptureDeviceInput(device: captureDevice)

            captureSession.addInput(captureDeviceInput)

        }catch {
            print(error.localizedDescription)
        }


        if let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession) {
            self.previewLayer = previewLayer
            self.view.layer.addSublayer(self.previewLayer)
            self.previewLayer.frame = self.view.layer.frame
            captureSession.startRunning()


            dataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString):NSNumber(value:kCVPixelFormatType_32BGRA)]

            dataOutput.alwaysDiscardsLateVideoFrames = true

            if captureSession.canAddOutput(dataOutput) {
                captureSession.addOutput(dataOutput)
            }

            captureSession.commitConfiguration()


            let queue = DispatchQueue(label: "com.brianadvent.captureQueue")
            dataOutput.setSampleBufferDelegate(self, queue: queue)



        }

     ...

    }