How to scan only certain areas through the camera with Swift5? - ios

Question

I'd like to scan QRcode through the camera. There is no problem scanning QRcode,
but I want to scan only certain areas. How can I do this?
I am currently aware of the QR code anywhere in the entire camera area.
import Foundation
import UIKit
import AVFoundation
class ScannerViewController : UIViewController, AVCaptureMetadataOutputObjectsDelegate {
#IBOutlet weak var qrcodeView: UIView!
#IBOutlet weak var mainText: UITextView!
#IBOutlet weak var headerBar: UINavigationBar!
var captureSession: AVCaptureSession!
var previewLayer: AVCaptureVideoPreviewLayer!
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = UIColor.black
self.qrcodeView.backgroundColor = UIColor.black.withAlphaComponent(0.5)
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]
} else {
failed()
return
}
previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
view.layer.insertSublayer(previewLayer, at: 0)
captureSession.startRunning()
}
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) {
// let scanRect = CGRect(x: 0, y: 0, width: 200, height: 200)
// let rectOfInterest = layer.metadataOutputRectConverted(fromLayerRect: scanRect)
// metadataObjects.rectOfInterest = rectOfInterest
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)
} else {
print("not support")
}
}
func found(code: String) {
print(code)
self.dismiss(animated: true, completion: nil)
}
func failed() {
captureSession = nil
}
}
Like the picture above, I would like to scan only within the square area.
I desperately need this.
Thanks in advance.

Answer 1

You can use rectOfInterest property to achieve this
add following code after captureSession.startRunning()
First you need to convert using rect using
let rectOfInterest = videoPreviewLayer?.metadataOutputRectConverted(fromLayerRect: self.viewAreaOfScan.frame) // videoPreviewLayer is AVCaptureVideoPreviewLayer
after that you can assign it to rectOfInterest of metadataOutput
metadataOutput.rectOfInterest = rectOfInterest ?? CGRect(x: 0, y: 0, width: 1, height: 1)