视觉框架条码检测iOS 11

Question

我一直在实施对苹果在WWDC2017中引入的新Vision视觉框架的测试。我专门研究条形码检测 - 从相机/图库扫描图像后，我能够得到它是否是条形码图像。但是，在查看barcodeDescriptor时，我看不到实际的条形码值或有效负载数据。在https://developer.apple.com/documentation/coreimage/cibarcodedescriptor页面上似乎没有任何内容可以识别任何属性。

我得到这些错误：

• 无法连接到远程服务：错误域= NSCocoaErrorDomain代码= 4097 “连接服务命名为
  com.apple.BarcodeSupport.BarcodeNotificationService”
• libMobileGestalt MobileGestalt.c：555：无法访问InverseDeviceID（请参阅问题/ 11744455>）
• 连接到名为com.apple.BarcodeSupport.BarcodeNotificationService的服务错误
  域= NSCocoaErrorDomain代码= 4097

有什么办法来访问从VNBarcodeObservation条形码价值？ 任何帮助将不胜感激。谢谢！ 这里是我使用的代码：

@IBAction func chooseImage(_ sender: Any) { 
     imagePicker.allowsEditing = true 
     imagePicker.sourceType = .photoLibrary 

     present(imagePicker, animated: true, completion: nil) 
    } 

    @IBAction func takePicture(_ sender: Any) { 
     if(UIImagePickerController .isSourceTypeAvailable(UIImagePickerControllerSourceType.camera)){ 
      imagePicker.sourceType = UIImagePickerControllerSourceType.camera 
      self .present(imagePicker, animated: true, completion: nil) 
     } 
     else{ 
      let alert = UIAlertController(title: "Warning", message: "Camera not available", preferredStyle: UIAlertControllerStyle.alert) 
      alert.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.default, handler: nil)) 
      self.present(alert, animated: true, completion: nil) 
     } 
    } 

    //PickerView Delegate Methods 

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) { 

     imagePicker .dismiss(animated: true, completion: nil) 
     classificationLabel.text = "Analyzing Image…" 

     guard let pickedImage = info[UIImagePickerControllerOriginalImage] as? UIImage 
      else { fatalError("no image from image picker") } 
     guard let ciImage = CIImage(image: pickedImage) 
      else { fatalError("can't create CIImage from UIImage") } 

     imageView.image = pickedImage 
     inputImage = ciImage 

     // Run the rectangle detector, which upon completion runs the ML classifier. 
     let handler = VNImageRequestHandler(ciImage: ciImage, options: [.properties : ""]) 
     DispatchQueue.global(qos: .userInteractive).async { 
      do { 
       try handler.perform([self.barcodeRequest]) 
      } catch { 
       print(error) 
      } 
     } 
    } 

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController){ 
     picker .dismiss(animated: true, completion: nil) 
     print("picker cancel.") 
    } 

    lazy var barcodeRequest: VNDetectBarcodesRequest = { 
     return VNDetectBarcodesRequest(completionHandler: self.handleBarcodes) 
    }() 

    func handleBarcodes(request: VNRequest, error: Error?) { 
     guard let observations = request.results as? [VNBarcodeObservation] 
      else { fatalError("unexpected result type from VNBarcodeRequest") } 
     guard observations.first != nil else { 
      DispatchQueue.main.async { 
       self.classificationLabel.text = "No Barcode detected." 
      } 
      return 
     } 

     // Loop through the found results 
     for result in request.results! { 

      // Cast the result to a barcode-observation 
      if let barcode = result as? VNBarcodeObservation { 

       // Print barcode-values 
       print("Symbology: \(barcode.symbology.rawValue)") 

       if let desc = barcode.barcodeDescriptor as? CIQRCodeDescriptor { 
        let content = String(data: desc.errorCorrectedPayload, encoding: .utf8) 

        // FIXME: This currently returns nil. I did not find any docs on how to encode the data properly so far. 
        print("Payload: \(String(describing: content))\n") 
        print("Error-Correction-Level: \(desc.errorCorrectedPayload)\n") 
        print("Symbol-Version: \(desc.symbolVersion)\n") 
       } 
      } 
     } 
    } 

Answer 1

如果苹果不打算为此提供一个图书馆，像下面的工作：

extension CIQRCodeDescriptor { 
    var bytes: Data? { 
     return errorCorrectedPayload.withUnsafeBytes { (pointer: UnsafePointer<UInt8>) in 
      var cursor = pointer 

      let representation = (cursor.pointee >> 4) & 0x0f 
      guard representation == 4 /* byte encoding */ else { return nil } 

      var count = (cursor.pointee << 4) & 0xf0 
      cursor = cursor.successor() 
      count |= (cursor.pointee >> 4) & 0x0f 

      var out = Data(count: Int(count)) 
      guard count > 0 else { return out } 

      var prev = (cursor.pointee << 4) & 0xf0 
      for i in 2...errorCorrectedPayload.count { 
       if (i - 2) == count { break } 

       let cursor = pointer.advanced(by: Int(i)) 
       let byte = cursor.pointee 
       let current = prev | ((byte >> 4) & 0x0f) 
       out[i - 2] = current 
       prev = (cursor.pointee << 4) & 0xf0 
      } 
      return out 
     } 
    } 
} 

然后

String(data: descriptor.bytes!, encoding: .utf8 /* or whatever */) 

Answer 2

显然，在iOS 11 beta 5 Apple中引入了新的payloadStringValue属性VNBarcodeObservation。现在，您可以读取QR码的信息，没有任何问题

if let payload = barcodeObservation.payloadStringValue { 
    print("payload is \(payload)") 
}