How to capture image only custom camera view area in Swift3 - ios

Question

I have the custom camera view. What I want is that I only want to capture the image inside of custom camera view when I press button.But it take the whole screen not just camera view. I also set preview layer's frame to cameraView's frame. Here is my code
class CustomCameraVC: UIViewController, AVCapturePhotoCaptureDelegate {
#IBOutlet weak var cameraView: UIView!
#IBOutlet weak var shotImage: UIImageView!
var captureSession: AVCaptureSession!
var imageOutput: AVCapturePhotoOutput!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
captureSession = AVCaptureSession()
captureSession.sessionPreset = AVCaptureSessionPresetMedium
imageOutput = AVCapturePhotoOutput()
let device = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
do {
let input = try AVCaptureDeviceInput(device: device)
if captureSession.canAddInput(input) {
captureSession.addInput(input)
if captureSession.canAddOutput(imageOutput) {
captureSession.addOutput(imageOutput)
captureSession.startRunning()
let captureVideoLayer: AVCaptureVideoPreviewLayer = AVCaptureVideoPreviewLayer.init(session: captureSession)
captureVideoLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
captureVideoLayer.frame = self.cameraView.layer.frame
self.cameraView.layer.addSublayer(captureVideoLayer)
}
}
} catch {
print("error")
}
}
#IBAction func takePhoto(_ sender: UIButton) {
let settingsForMonitoring = AVCapturePhotoSettings()
settingsForMonitoring.flashMode = .auto
settingsForMonitoring.isAutoStillImageStabilizationEnabled = true
settingsForMonitoring.isHighResolutionPhotoEnabled = false
imageOutput?.capturePhoto(with: settingsForMonitoring, delegate: self)
}
func capture(_ captureOutput: AVCapturePhotoOutput, didFinishProcessingPhotoSampleBuffer photoSampleBuffer: CMSampleBuffer?, previewPhotoSampleBuffer: CMSampleBuffer?, resolvedSettings: AVCaptureResolvedPhotoSettings, bracketSettings: AVCaptureBracketedStillImageSettings?, error: Error?) {
if let photoSampleBuffer = photoSampleBuffer {
let photoData = AVCapturePhotoOutput.jpegPhotoDataRepresentation(forJPEGSampleBuffer: photoSampleBuffer, previewPhotoSampleBuffer: previewPhotoSampleBuffer)
let image = UIImage(data: photoData!)
shotImage.image = UIImage(data: photoData!)
UIImageWriteToSavedPhotosAlbum(image!, nil, nil, nil)
}
}
}