Question

我正在尝试制作一个简单的相机应用程序，前置摄像头可以检测到脸部。这应该很简单：

创建一个继承自UIImage的CameraView类并将其放在UI中。确保它实现了AVCaptureVideoDataOutputSampleBufferDelegate，以便实时处理来自摄像机的帧。
```
class CameraView: UIImageView, AVCaptureVideoDataOutputSampleBufferDelegate 
```

在实例化CameraView时调用的函数handleCamera中，设置AVCapture会话。添加相机输入。

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传递AVCaptureVideoDataOutputSampleBufferDelegate（在本例中为类本身）处理的数据。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")
    }

设置相机预览视图并运行会话

    // 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()

，将接收的样本缓冲区转换为CIImage以检测面。如果找到了面孔，请提供反馈。

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：我可以让相机运行但是我从互联网上尝试了大量不同的代码，我从来没有能够获得captureOutput来检测一张脸。应用程序没有进入函数或由于变量不起作用而崩溃，最常见的是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函数会在缓冲区丢失时调用，而不是从摄像机调用时调用。

iOS相机人脸追踪（Swift 3 Xcode 8）

1 个答案: