How to add autofocus to AVCaptureSession? SWIFT

Question

I'm using AVFoundation to recognize text and perform OCR. How do I add autofocus? I don't want to have the yellow square thing when user taps the screen, I just want it to automatically focus on the object, a credit card for example.

Here is my session code.

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

On my 6S the default camera focus mode is .ContinuousAutoFocus, which continuously focuses on whatever is taking up most of the camera's field of vision. Sounds like that's what you want.

You can check if your camera supports auto focus like so:

camera.isFocusModeSupported(.ContinuousAutoFocus)

and if it's not already set, set it like so:

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

Answer 2

Here is what I did:

 //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()
 }