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1. 从相机里扫描

1.1 申请相机权限

• 导入： import AVFoundation
• 在项目的 Info.plist 文件里添加 Privacy - Camera Usage Descriptio 描述申请使用相机权限。
• 查询相机权限： AVCaptureDevice.authorizationStatus(for: .video)
• 权限类型：AVAuthorizationStatus

swift">notDetermined   未申请
restricted      受限制
denied          已拒绝
authorized      已授权

• 请求相机权限，系统弹出授权申请提示：

swift">AVCaptureDevice.requestAccess(for: .video) { (status) in
    // handle request result
}

1.2 创建Scanner

• 获得设备:

swift"> guard let device = AVCaptureDevice.default(for: .video) else {
    print("device error")
    return
}

• 创建input:

swift"> let input: AVCaptureDeviceInput
do {
  input = try AVCaptureDeviceInput(device: device)
} catch {
  print("input error")
  return
}
if self.captureSession.canAddInput(input) {
    self.captureSession.addInput(input)
} else {
    print("session can't add input")
    return
}

• 创建 output:

swift">let output = AVCaptureMetadataOutput()
if self.captureSession.canAddOutput(output) {
    // Tips: add output must before of set output
    self.captureSession.addOutput(output)
} else {
    print("session can't add output")
    return
}

// Set metadata identification type qr: QR code; Other: Barcode
// 设置扫描类型（qr：二维码，其他：条形码）
let hopeSupportTypes = [AVMetadataObject.ObjectType.qr,
                        AVMetadataObject.ObjectType.ean13,
                        AVMetadataObject.ObjectType.ean8,
                        AVMetadataObject.ObjectType.pdf417]
var types: [AVMetadataObject.ObjectType] = []
for type in hopeSupportTypes {
    if output.availableMetadataObjectTypes.contains(type) {
        types.append(type)
    }
}
output.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
output.metadataObjectTypes = types        
output.rectOfInterest = CGRect(x: 0, y: 0,
                               width: self.view.bounds.size.width,
                               height: self.view.bounds.size.height)

• 设置预览视图:

swift">let previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
previewLayer.frame = scanView.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
scanView.layer.addSublayer(previewLayer)

1.3 开始扫描

Tips: 不能在主线程中扫描，否则会无法响应用户操作，导致卡死现象

swift">DispatchQueue.global(qos: .userInitiated).async {
    self.captureSession.startRunning()
}

1.4 处理扫描结果

遵循 AVCaptureMetadataOutputObjectsDelegate 协议，实现扫描回调方法：

swift"> func metadataOutput(_ output: AVCaptureMetadataOutput,
                    didOutput metadataObjects: [AVMetadataObject],
                    from connection: AVCaptureConnection) {
    guard let metadataObject = metadataObjects.first else {
        captureSession.stopRunning()
        return
    }
    guard let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject else {
        print("as? AVMetadataMachineReadableCodeObject faliue")
        return
    }
    guard let stringValue = readableObject.stringValue else {
        print("stringValue faliue")
        return
    }
    AudioServicesPlaySystemSound(SystemSoundID(kSystemSoundID_Vibrate))
    print("scan result: \(stringValue)")   // print result
    captureSession.stopRunning()
}

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2. 从相册里扫描

2.1 获取相册权限

• 导入： import Photos
• 在项目的 Info.plist 文件里添加 Privacy - Photo Library Usage Description 描述申请访问相册权限。
• 查询相机权限：PHPhotoLibrary.authorizationStatus()
• 权限类型：PHAuthorizationStatus

swift">notDetermined   未申请
restricted      受限制
denied          已拒绝
authorized      已授权
limited         已授权有限库访问

• 请求相册权限，系统弹出授权申请提示：

swift">PHPhotoLibrary.requestAuthorization { (status) in
    // handle request result
}

2.2 打开相册

Tips: 打开相册必须在主线程中执行

swift"> /// have photos permission
DispatchQueue.main.async {
    self.openPhotoLabrary()
}

private func openPhotoLabrary() {
    let picker = UIImagePickerController()
    picker.title = "Photos"
    picker.delegate = self
    picker.allowsEditing = true
    picker.sourceType = .photoLibrary
    picker.navigationBar.barStyle = .default
    self.present(picker, animated: true, completion: nil)
}

2.3 获得选择结果

遵循 UIImagePickerControllerDelegate 和 UINavigationControllerDelegate 协议，并实现选中相片后触发的协议方法：

swift">func imagePickerController(_ picker: UIImagePickerController,
                           didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    dismiss(animated: true)
    
    guard let image = info[.originalImage] as? UIImage else {
        print("choose not image")
        return
    }
    parseBarCode(image: image)
}

2.4 解析相片中的二维码或条形码

导入：import Vision

swift"> /// parse qrCode or barCode
private func parseBarCode(image: UIImage) {
    guard let cgimg = image.cgImage else {
        return
    }
    
    let request = VNDetectBarcodesRequest { req, err in
        if let error = err {
            print("parseBarCode error: \(error)")
            return
        }
        self.handleResults(req.results)
    }
    
    let handler = VNImageRequestHandler(cgImage: cgimg)
    do {
        try handler.perform([request])
    } catch {
        print("parseBarCode error: \(error)")
    }
}

private func handleResults(_ result: [VNObservation]?) {
    guard let results = result, results.count > 0 else {
        print("parseBarCode result is nil: \(String(describing: result))")
        return
    }
    for result in results {
        self.handleResult(result)
    }
}

private func handleResult(_ result: VNObservation) {
    guard let barcode = result as? VNBarcodeObservation,
          let value = barcode.payloadStringValue else {
        print("handleResult covert to string error: \(result)")
        return
    }
    
    if barcode.symbology == .qr {
        print("二维码: \(value)")
    } else {
        print("条形码: \(value), \(barcode.symbology.rawValue)")
    }
}

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github demo

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参考：
iOS16 Swift二维码/条形码扫描+相册获取识别