iOS :扫描条形码非常慢

Question

我正在使用swift4开发扫描条形码应用程序。

我试过使用两种流行的开源软件，分别是MTBarcode (使用AVFoundation)和iOS Vision (使用GoogleVision框架)，但扫描速度并不像我预期的那样快，大约需要2到3秒才能检测到真正的条形码。

有人建议我把sessionPreset改成AVCaptureSessionPresetMedium，但效果不好。

任何人都可以建议我如何提高扫描速度。我们应该更新另一个摄像头配置还是使用另一个开源软件？

Answer 1

帮助我加速条形码扫描的是将AVCaptureSession的sessionPreset属性设置为high：

captureSession = AVCaptureSession()
captureSession.sessionPreset = .high

希望能有所帮助。

更新

您也可以尝试使用Firebase ML Kit。当我测试它的时候，它工作得非常快。

Answer 2

我做了QRCode和BarCodeScanner，我将分享下面的代码片段

import AVFoundation

添加委派

class YOUR_VIEW_CONTROLLER: UIViewController,AVCaptureMetadataOutputObjectsDelegate 

初始化所需变量

    var captureSession:AVCaptureSession?
    var videoPreviewLayer:AVCaptureVideoPreviewLayer?
    var qrCodeFrameView:UIView?
    var qrCodeDelegate:QRCodeScannerVCDelegate?

    let supportedCodeTypes = [AVMetadataObjectTypeUPCECode,
                              AVMetadataObjectTypeCode39Code,
                              AVMetadataObjectTypeCode39Mod43Code,
                              AVMetadataObjectTypeCode93Code,
                              AVMetadataObjectTypeCode128Code,
                              AVMetadataObjectTypeEAN8Code,
                              AVMetadataObjectTypeEAN13Code,
                              AVMetadataObjectTypeAztecCode,
                              AVMetadataObjectTypePDF417Code,
                              AVMetadataObjectTypeQRCode]

将下面的函数添加到viewController中

   func startVideoCapture(){
        // Get an instance of the AVCaptureDevice class to initialize a device object and provide the video as the media type parameter.
        let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)

        do {
            // Get an instance of the AVCaptureDeviceInput class using the previous device object.
            let input = try AVCaptureDeviceInput(device: captureDevice)

            // Initialize the captureSession object.
            captureSession = AVCaptureSession()

            // Set the input device on the capture session.
            captureSession?.addInput(input)

            // Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
            let captureMetadataOutput = AVCaptureMetadataOutput()
            captureSession?.addOutput(captureMetadataOutput)

            // Set delegate and use the default dispatch queue to execute the call back
            captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            captureMetadataOutput.metadataObjectTypes = supportedCodeTypes

            // Initialize the video preview layer and add it as a sublayer to the viewPreview view's layer.
            videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
            videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
            videoPreviewLayer?.frame = self.qrCodeView.bounds
            self.qrCodeView.layer.addSublayer(videoPreviewLayer!)
            self.qrCodeView.clipsToBounds = true
            // Start video capture.
            captureSession?.startRunning()
            qrCodeFrameView = UIView()

//            if let qrCodeFrameView = qrCodeFrameView {
//                qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
//                qrCodeFrameView.layer.borderWidth = 2
//                self.qrCodeView.addSubview(qrCodeFrameView)
//                self.qrCodeView.bringSubview(toFront: qrCodeFrameView)
//            }

        } catch {
            // If any error occurs, simply print it out and don't continue any more.
            print(error)
            return
        }
    }

    // MARK: - AVCaptureMetadataOutputObjectsDelegate Methods

    func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {

        // Check if the metadataObjects array is not nil and it contains at least one object.
        if metadataObjects == nil || metadataObjects.count == 0 {
            qrCodeFrameView?.frame = CGRect.zero
            print("No QR/barcode is detected")
            return
        }

        // Get the metadata object.
        let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject

        if supportedCodeTypes.contains(metadataObj.type) {
            // If the found metadata is equal to the QR code metadata then update the status label's text and set the bounds
            let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
            if barCodeObject != nil{
                qrCodeFrameView?.frame = barCodeObject!.bounds
            }

            if metadataObj.stringValue != nil {
                print("\(metadataObj.stringValue)")

            }
        }
    }

在你的viewWillAppear中

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(true)
    self.startVideoCapture()
}

在调用startViewCapture之前，别忘了检查摄像头权限

希望这能对你有所帮助