iOS 相机面部跟踪 (Swift 3 Xcode 8)

Question

我正在尝试制作一个前置摄像头可以检测人脸的简单相机应用程序。这应该很简单：

创建一个继承自 UIImage 的 CameraView class，并将其放置在 UI 中。确保它实现了 AVCaptureVideoDataOutputSampleBufferDelegate，以便实时处理来自相机的帧。
```
class CameraView: UIImageView, AVCaptureVideoDataOutputSampleBufferDelegate 
```

在实例化 CameraView 时调用的函数 handleCamera 中，设置一个 AVCapture 会话。添加来自相机的输入。

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)
    }

创建输出。创建一个串行输出队列以将数据传递到该队列，然后由 AVCaptureVideoDataOutputSampleBufferDelegate（在本例中为 class 本身）进行处理。将输出添加到会话。

    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")
    }

设置相机预览视图和运行会话

    // 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()

在委托的captureOutput函数运行中，将接收到的样本缓冲区转换为CIImage以检测人脸。如果找到人脸，请反馈。

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：我可以得到摄像头运行ning，但是我在整个互联网上尝试了多种不同的代码，但我从来没有能够得到 captureOutput 来检测人脸。要么应用程序没有进入函数，要么因为变量不起作用而崩溃，最常见的情况是 sampleBuffer 变量为 nul。我做错了什么？

Answer 1

您需要将 captureOutput 函数参数更改为以下内容：func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!)

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

iOS 相机面部跟踪 (Swift 3 Xcode 8)

iOS camera facetracking (Swift 3 Xcode 8)

camera

core-image

face-detection

ios

swift