iOS相机面部跟踪（Swift 3 Xcode 8）

Question

iOS相机面部跟踪（Swift 3 Xcode 8）

4

我正在努力制作一个简单的相机应用程序，其中前置摄像头可以检测人脸。

这应该是足够简单的：

Create a CameraView class that inherits from UIImage and place it in the UI. Make sure it implements AVCaptureVideoDataOutputSampleBufferDelegate in order to process frames from the camera in real time.
```
class CameraView: UIImageView, AVCaptureVideoDataOutputSampleBufferDelegate 
```

Within a function handleCamera, called when the CameraView is instantiated, setup an AVCapture session. Add input from the camera.

override init(frame: CGRect) {
    super.init(frame:frame)

    handleCamera()
}

func handleCamera () {
    camera = AVCaptureDevice.defaultDevice(withDeviceType: .builtInWideAngleCamera,
                                           mediaType: AVMediaTypeVideo, position: .front)
    session = AVCaptureSession()

    // Set recovered camera as an input device for the capture session
    do {
        try input = AVCaptureDeviceInput(device: camera);
    } catch _ as NSError {
        print ("ERROR: Front camera can't be used as input")
        input = nil
    }

    // Add the input from the camera to the capture session
    if (session?.canAddInput(input) == true) {
        session?.addInput(input)
    }

Create output. Create a serial output queue to pass the data to which will then be processed by the AVCaptureVideoDataOutputSampleBufferDelegate (the class itself in this case). Add output to session.

    output = AVCaptureVideoDataOutput()

    output?.alwaysDiscardsLateVideoFrames = true    
    outputQueue = DispatchQueue(label: "outputQueue")
    output?.setSampleBufferDelegate(self, queue: outputQueue)

    // add front camera output to the session for use and modification
    if(session?.canAddOutput(output) == true){
        session?.addOutput(output)
    } // front camera can't be used as output, not working: handle error
    else {
        print("ERROR: Output not viable")
    }

Setup the camera preview view and run the session

    // Setup camera preview with the session input
    previewLayer = AVCaptureVideoPreviewLayer(session: session)
    previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
    previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.portrait
    previewLayer?.frame = self.bounds
    self.layer.addSublayer(previewLayer!)

    // Process the camera and run it onto the preview
    session?.startRunning()

in the captureOutput function run by the delegate, convert the recieved sample buffer to CIImage in order to detect faces. Give feedback if a face is found.

func captureOutput(_ captureOutput: AVCaptureOutput!, didDrop sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {

let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
let cameraImage = CIImage(cvPixelBuffer: pixelBuffer!)


let accuracy = [CIDetectorAccuracy: CIDetectorAccuracyHigh]
let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: nil, options: accuracy)
let faces = faceDetector?.features(in: cameraImage)

for face in faces as! [CIFaceFeature] {

      print("Found bounds are \(face.bounds)")

      let faceBox = UIView(frame: face.bounds)

      faceBox.layer.borderWidth = 3
      faceBox.layer.borderColor = UIColor.red.cgColor
      faceBox.backgroundColor = UIColor.clear
      self.addSubview(faceBox)

      if face.hasLeftEyePosition {
          print("Left eye bounds are \(face.leftEyePosition)")
      }

      if face.hasRightEyePosition {
          print("Right eye bounds are \(face.rightEyePosition)")
      }
  }
}

我的问题是：我可以让摄像头运行，但是我尝试了来自互联网各处的众多不同代码后，从未能够使captureOutput检测到人脸。要么应用程序没有进入函数，要么由于不起作用的变量而崩溃，最常见的是样本缓冲区变量为null。我做错了什么？

- KazToozs

1个回答

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- Elena Zherdeva · Accepted Answer

你需要将captureOutput函数的参数更改为以下内容：

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!)

你的captureOutput函数在缓冲区丢失时调用，而不是从相机获取时调用。