Camera Barcode Scanning Works on iPhone, But Not iPad - ios

Question

I'm using AVCaptureDevice API for scanning barcode and it works very well on iPhone, but very similar code I have doesn't work on iPad and I'm not quite sure why (not detecting any barcode at all). The main differences are the size of scan area, position and orientation. I tested using iPhone 12 mini (iOS 15 beta) and the original iPad Pro 9.7" (iOS 14.6). Not sure if that matters.
Below is the code for the scanner. Please let me know if you noticed something that should be changed.
import Foundation
import AVFoundation
import UIKit
class ScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
var barcodeCallback: (String) -> Void
var cameraScanDismissedCallback: (Bool) -> Void
var scanned = false
var currentDevice: AVCaptureDevice!
var scanRectView: UIView!
init(barcodeCallback: #escaping (String) -> Void, cameraScanDismissedCallback: #escaping (Bool) -> Void) {
self.barcodeCallback = barcodeCallback;
self.cameraScanDismissedCallback = cameraScanDismissedCallback;
super.init(nibName: nil, bundle: nil)
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.black
captureSession = AVCaptureSession()
guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
let videoInput: AVCaptureDeviceInput
do {
videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
} catch {
return
}
if (captureSession.canAddInput(videoInput)) {
captureSession.addInput(videoInput)
} else {
failed()
return
}
let metadataOutput = AVCaptureMetadataOutput()
if (captureSession.canAddOutput(metadataOutput)) {
captureSession.addOutput(metadataOutput)
metadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
metadataOutput.metadataObjectTypes = [.qr, .ean8, .ean13, .pdf417, .code128, .aztec, .code39, .code39Mod43, .code93, .dataMatrix, .face, .interleaved2of5, .itf14, .upce]
} else {
failed()
return
}
let windowSize = UIScreen.main.bounds.size
var scanSize: CGSize!;
var scanRect: CGRect!;
if(UIDevice.current.userInterfaceIdiom == .pad){
scanSize = CGSize(width:windowSize.width*1/3, height:windowSize.width*1/7);
scanRect = CGRect(x: UIScreen.main.bounds.midX - scanSize.width/2,
y: UIScreen.main.bounds.midY - scanSize.height/2,
width:scanSize.width, height:scanSize.height);
}else{
scanSize = CGSize(width:windowSize.width*2/3, height:windowSize.width*1/3);
scanRect = CGRect(x: UIScreen.main.bounds.midX - scanSize.width/2,
y: UIScreen.main.bounds.midY - scanSize.height/2,
width:scanSize.width, height:scanSize.height);
}
scanRect = CGRect(x:scanRect.origin.y/windowSize.height,
y:scanRect.origin.x/windowSize.width,
width:scanRect.size.height/windowSize.height,
height:scanRect.size.width/windowSize.width);
metadataOutput.rectOfInterest = scanRect
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
if(UIDevice.current.userInterfaceIdiom == .pad){
let orientation: UIDeviceOrientation = UIDevice.current.orientation
previewLayer.connection?.videoOrientation = {
switch (orientation) {
case .faceUp:
return .landscapeLeft
case .portrait:
return .portrait
case .landscapeRight:
return .landscapeLeft
case .landscapeLeft:
return .landscapeRight
default:
return .portrait
}
}()
}
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.addSublayer(previewLayer)
scanRectView = UIView();
view.addSubview(self.scanRectView)
scanRectView.frame = CGRect(x:0, y:0, width: scanSize.width,
height: scanSize.height);
if(UIDevice.current.userInterfaceIdiom == .pad){
scanRectView.center = CGPoint( x:UIScreen.main.bounds.midX - scanSize.width/2,
y:UIScreen.main.bounds.midY - scanSize.height/2)
}else{
scanRectView.center = CGPoint( x:UIScreen.main.bounds.midX,
y:UIScreen.main.bounds.midY)
}
scanRectView.layer.borderColor = UIColor.yellow.cgColor
scanRectView.layer.borderWidth = 5;
currentDevice = videoCaptureDevice
captureSession.startRunning()
toggleTorch(on: true)
}
func toggleTorch(on: Bool) {
guard let device = currentDevice else { return }
if device.hasTorch {
do {
try device.lockForConfiguration()
if(UIDevice.current.userInterfaceIdiom == .pad){
device.videoZoomFactor = 1.3
}else{
device.videoZoomFactor = 1.5
}
if on == true {
device.torchMode = .on
} else {
device.torchMode = .off
}
device.unlockForConfiguration()
} catch {
print("Torch could not be used")
}
} else {
print("Torch is not available")
}
}
func failed() {
let ac = UIAlertController(title: "Scanning not supported", message: "Your device does not support scanning a code from an item. Please use a device with a camera.", preferredStyle: .alert)
ac.addAction(UIAlertAction(title: "OK", style: .default))
present(ac, animated: true)
captureSession = nil
toggleTorch(on: false)
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if (captureSession?.isRunning == false) {
captureSession.startRunning()
toggleTorch(on: true)
}
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if (captureSession?.isRunning == true) {
captureSession.stopRunning()
toggleTorch(on: false)
}
cameraScanDismissedCallback(scanned)
}
func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
captureSession.stopRunning()
if let metadataObject = metadataObjects.first {
guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else { return }
guard let stringValue = readableObject.stringValue else { return }
AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
found(code: stringValue)
scanned = true
}
dismiss(animated: true)
}
func found(code: String) {
print(code)
barcodeCallback(code)
}
override var prefersStatusBarHidden: Bool {
return true
}
override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
if(UIDevice.current.userInterfaceIdiom == .pad){
return .landscape
}else{
return .portrait
}
}
}

Answer 1

Just in case anyone ran into a similar issue, check for the following:
Orientation of the video
The position of AVCaptureMetadataOutput.rectOfInterest
I'm still having an issue with the rectOfInterest not positioned at the center, but it works. Once I can figure out how to center it, I will post the solution here.

Answer 2

it isn't center probably because of your navigationBar.
Try set rectOfInterest as below, remember that camer use different coordinate than UIView, posX and posY are in UIView coordinates
let aimRect = CGRect(x: (posY - navBar.height) / UIScreen.main.bounds.height,
y: posX / UIScreen.main.bounds.width,
width: rectHeight / UIScreen.main.bounds.height,
height: rectWidth / UIScreen.main.bounds.width)