如何将自动对焦添加到AVCaptureSession？迅速

Question

我正在使用AVFoundation识别文本并执行OCR.如何添加自动对焦？当用户点击屏幕时,我不想要黄色方块的东西,我只是想让它自动聚焦在对象上,例如信用卡.

这是我的会话代码.

func setupSession() {
  session = AVCaptureSession()
  session.sessionPreset = AVCaptureSessionPresetHigh

  let camera = AVCaptureDevice
     .defaultDeviceWithMediaType(AVMediaTypeVideo)

  do { input = try AVCaptureDeviceInput(device: camera) } catch { return }

  output = AVCaptureStillImageOutput()
  output.outputSettings = [ AVVideoCodecKey: AVVideoCodecJPEG ]

  guard session.canAddInput(input)
     && session.canAddOutput(output) else { return }

  session.addInput(input)
  session.addOutput(output)

  previewLayer = AVCaptureVideoPreviewLayer(session: session)

  previewLayer!.videoGravity = AVLayerVideoGravityResizeAspect
  previewLayer!.connection?.videoOrientation = .Portrait

  view.layer.addSublayer(previewLayer!)

  session.startRunning()

}

Answer 1

在我的6S上,默认的相机对焦模式是.ContinuousAutoFocus,它持续关注占据相机视野大部分的任何物体.听起来就像你想要的那样.

您可以检查您的相机是否支持自动对焦:

camera.isFocusModeSupported(.ContinuousAutoFocus)

如果尚未设置,请将其设置为:

try! camera.lockForConfiguration()
camera.focusMode = .ContinuousAutoFocus
camera.unlockForConfiguration()

Answer 2

这是我做的:

 //get instance of phone camera
 let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
 //try to enable auto focus
 if(captureDevice!.isFocusModeSupported(.continuousAutoFocus)) {
     try! captureDevice!.lockForConfiguration()
     captureDevice!.focusMode = .continuousAutoFocus
     captureDevice!.unlockForConfiguration()
 }