Get snapshot from AVCaptureSession contaning Visionkit face detection elements - swift

Question

I use AVCaptureSession to setup a camera view and using vision kit to detect and add a rectangular on the face.
Here is how I can do it
override func viewDidLoad() {
super.viewDidLoad()
self.prepareVisionRequest()
}
fileprivate func prepareVisionRequest() {
//self.trackingRequests = []
var requests = [VNTrackObjectRequest]()
let faceDetectionRequest = VNDetectFaceRectanglesRequest(completionHandler: { (request, error) in
if error != nil {
print("FaceDetection error: \(String(describing: error)).")
}
guard let faceDetectionRequest = request as? VNDetectFaceRectanglesRequest,
let results = faceDetectionRequest.results else {
return
}
DispatchQueue.main.async {
// Add the observations to the tracking list
for observation in results {
let faceTrackingRequest = VNTrackObjectRequest(detectedObjectObservation: observation)
faceTrackingRequest.trackingLevel = .fast
requests.append(faceTrackingRequest)
}
self.trackingRequests = requests
}
})
// Start with detection. Find face, then track it.
self.detectionRequests = [faceDetectionRequest]
self.sequenceRequestHandler = VNSequenceRequestHandler()
self.setupVisionDrawingLayers()
}
// MARK: Drawing Vision Observations
fileprivate func setupVisionDrawingLayers() {
let captureDeviceResolution = self.captureDeviceResolution
let captureDeviceBounds = CGRect(x: 0,
y: 0,
width: captureDeviceResolution.width,
height: captureDeviceResolution.height)
let captureDeviceBoundsCenterPoint = CGPoint(x: captureDeviceBounds.midX,
y: captureDeviceBounds.midY)
let normalizedCenterPoint = CGPoint(x: 0.5, y: 0.5)
guard let rootLayer = self.rootLayer else {
self.presentErrorAlert(message: "view was not property initialized")
return
}
let overlayLayer = CALayer()
overlayLayer.name = "DetectionOverlay"
overlayLayer.masksToBounds = true
overlayLayer.anchorPoint = normalizedCenterPoint
overlayLayer.bounds = captureDeviceBounds
overlayLayer.position = CGPoint(x: rootLayer.bounds.midX, y: rootLayer.bounds.midY)
let faceRectangleShapeLayer = CAShapeLayer()
faceRectangleShapeLayer.name = "RectangleOutlineLayer"
faceRectangleShapeLayer.bounds = captureDeviceBounds
faceRectangleShapeLayer.anchorPoint = normalizedCenterPoint
faceRectangleShapeLayer.position = captureDeviceBoundsCenterPoint
faceRectangleShapeLayer.fillColor = UIColor.white.withAlphaComponent(0.9).cgColor
// faceLandmarksShapeLayer.strokeColor = UIColor.white.withAlphaComponent(0.7).cgColor
faceRectangleShapeLayer.lineWidth = 5
faceRectangleShapeLayer.shadowOpacity = 0.7
faceRectangleShapeLayer.shadowRadius = 5
let faceLandmarksShapeLayer = CAShapeLayer()
faceLandmarksShapeLayer.name = "FaceLandmarksLayer"
faceLandmarksShapeLayer.bounds = captureDeviceBounds
faceLandmarksShapeLayer.anchorPoint = normalizedCenterPoint
faceLandmarksShapeLayer.position = captureDeviceBoundsCenterPoint
faceLandmarksShapeLayer.fillColor = nil
faceLandmarksShapeLayer.strokeColor = nil
//
overlayLayer.addSublayer(faceRectangleShapeLayer)
faceRectangleShapeLayer.addSublayer(faceLandmarksShapeLayer)
rootLayer.addSublayer(overlayLayer)
self.detectionOverlayLayer = overlayLayer
self.detectedFaceRectangleShapeLayer = faceRectangleShapeLayer
self.detectedFaceLandmarksShapeLayer = faceLandmarksShapeLayer
self.updateLayerGeometry()
}
Now, I'm trying three ways to take snapshots
1- using UIGraphicsImageRenderer, it shows only the rectangular on the face and the camera view in not visible - it's black
2- Take image from captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) - the image from the buffer shows only the camera view, no rectangular
3- use AVCapturePhotoCaptureDelegate to capture photo from AVCaptureSession, the captured photo shows only the camera view, no rectangular
Could you please help me to take snapshot that contains both camera view and the rectangular! Thanks