AVCaptureMetadataOutput Region of Interest for Barcodes - ios

Question

I am looking to display a UIView subclass within a UIStackView. The subclass is called PLBarcodeScannerView and is using AVCaptureMetadataOuput to detect barcodes within the camera's field of view. Because this view is not the entire screen, I need to set the region of interest to be the same as the frame of the PLBarcodeScannerView because the user is only seeing a portion of the camera view and we want to be sure that the barcode in the visible view is the one being scanned.
Issue
I cannot seem to set the metadataOutputRectOfInterest properly, nor does the "zoom level" of the preview layer on this view seem correct, although the aspect ratio is correct. The system does receive barcodes successfully, but they are not always visible within the preview window. Codes are still scanned when they reside outside the visible preview window.
Screenshot:
The colorful photo is the PLBarcodeScannerView. Only codes which are fully visible inside this view should be considered.
Below is the code that initializes the view:
This is called within the init methods of PLBarcodeScannerView:UIView
func setupView() {
session = AVCaptureSession()
let tap = UITapGestureRecognizer(target: self, action: #selector(self.resume))
addGestureRecognizer(tap)
// Set the captureDevice.
let videoCaptureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
// Create input object.
let videoInput: AVCaptureDeviceInput?
do {
videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
} catch {
return
}
// Add input to the session.
if (session!.canAddInput(videoInput)) {
session!.addInput(videoInput)
} else {
scanningNotPossible()
}
// Create output object.
let metadataOutput = AVCaptureMetadataOutput()
// Add output to the session.
if (session!.canAddOutput(metadataOutput)) {
session!.addOutput(metadataOutput)
// Send captured data to the delegate object via a serial queue.
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
// Set barcode type for which to scan: EAN-13.
metadataOutput.metadataObjectTypes = [
AVMetadataObjectTypeCode128Code
]
} else {
scanningNotPossible()
}
// Determine the size of the region of interest
let x = self.frame.origin.x/UIScreen.main.bounds.width
let y = self.frame.origin.y/UIScreen.main.bounds.height
let width = self.frame.width/UIScreen.main.bounds.height
let height = self.frame.height/UIScreen.main.bounds.height
let scanRectTransformed = CGRect(x: x, y: y, width: 1, height: height)
metadataOutput.metadataOutputRectOfInterest(for: scanRectTransformed)
// Add previewLayer and have it show the video data.
previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.frame = self.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
layer.addSublayer(previewLayer)
// Begin the capture session.
session!.startRunning()
}