AVFoundation, DataMatrix, Swift 4 - ios

Question

Ugh. My struggle with changes in Swift 4 AVFoundation continues.
I have a data matrix "QR" code that I'm trying to read.
It reads just fine with Swift 3 compilation but with the Swift 4 changes to the code it is not picked up.
Also note that the Apple provided example that is supposed to work with Swift 4 does not read the DataMatrix code either
When I print out the available types Data Matrix is available.
print("types available:\n \(metadataOutput.availableMetadataObjectTypes)")
yields:
types available:
[__ObjC.AVMetadataObject.ObjectType(_rawValue: face), ...
__ObjC.AVMetadataObject.ObjectType(_rawValue: org.iso.DataMatrix), ...
However, didOutput metadataObjects: is never called when I run the code. It DOES get called for ever other type however.
Additionally adding in the type explicitly:
metadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.dataMatrix]
does nothing different.
Anyone have experience with scanning DataMatrix in Swift 4?
Code:
import UIKit
import AVFoundation
class ViewController: UIViewController,AVCaptureMetadataOutputObjectsDelegate {
var videoCaptureDevice: AVCaptureDevice = AVCaptureDevice.default(for: AVMediaType.video)!
var device = AVCaptureDevice.default(for: AVMediaType.video)
var output = AVCaptureMetadataOutput()
var previewLayer: AVCaptureVideoPreviewLayer?
var captureSession = AVCaptureSession()
var code: String?
var scannedCode = UILabel()
override func viewDidLoad() {
super.viewDidLoad()
self.setupCamera()
self.addLabelForDisplayingCode()
}
private func setupCamera() {
let input = try? AVCaptureDeviceInput(device: videoCaptureDevice)
if self.captureSession.canAddInput(input!) {
self.captureSession.addInput(input!)
}
self.previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
if let videoPreviewLayer = self.previewLayer {
videoPreviewLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill
videoPreviewLayer.frame = self.view.bounds
view.layer.addSublayer(videoPreviewLayer)
}
let metadataOutput = AVCaptureMetadataOutput()
if self.captureSession.canAddOutput(metadataOutput) {
self.captureSession.addOutput(metadataOutput)
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
print("types available:\n \(metadataOutput.availableMetadataObjectTypes)")
metadataOutput.metadataObjectTypes = metadataOutput.availableMetadataObjectTypes
// metadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.dataMatrix]
} else {
print("Could not add metadata output")
}
}
private func addLabelForDisplayingCode() {
view.addSubview(scannedCode)
scannedCode.translatesAutoresizingMaskIntoConstraints = false
scannedCode.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20.0).isActive = true
scannedCode.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20.0).isActive = true
scannedCode.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20.0).isActive = true
scannedCode.heightAnchor.constraint(equalToConstant: 50).isActive = true
scannedCode.font = UIFont.preferredFont(forTextStyle: .title2)
scannedCode.backgroundColor = UIColor.black.withAlphaComponent(0.5)
scannedCode.textAlignment = .center
scannedCode.textColor = UIColor.white
scannedCode.text = "Scanning...."
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if (captureSession.isRunning == false) {
captureSession.startRunning();
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if (captureSession.isRunning == true) {
captureSession.stopRunning();
}
}
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
print(metadataObjects)
for metadata in metadataObjects {
let readableObject = metadata as! AVMetadataMachineReadableCodeObject
let code = readableObject.stringValue
scannedCode.text = code
}
}
}
Thanks so much.

Answer 1

You have to make sure the connection is not mirrored.
The data matrix needs to be read in the original format.
https://developer.apple.com/documentation/avfoundation/avcaptureconnection/1389172-isvideomirrored