如何在 swift ios 中扫描后获取二维码图像？

Question

我正在 Xcode 中使用 swift 开发一个二维码阅读器应用程序。我用以下代码扫描了二维码：

import UIKit
import AVFoundation

class ScannerViewController: UIViewController {

    var captureSession = AVCaptureSession()

    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    var qrCodeFrameView: UIView?

    var scannerMetadataObj : AVMetadataMachineReadableCodeObject?

    @IBOutlet weak var testImageView: UIImageView!


    override func viewDidLoad() {
        super.viewDidLoad()


        let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back)

        guard let captureDevice = deviceDiscoverySession.devices.first else {
            print("Failed to get the camera device")
            return
        }

        do {

            let input = try AVCaptureDeviceInput(device: captureDevice)

            captureSession.addInput(input)

            let captureMetadataOutput = AVCaptureMetadataOutput()
            captureSession.addOutput(captureMetadataOutput)

            captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            captureMetadataOutput.metadataObjectTypes = supportedCodeTypes

        } catch {
            return
        }

        videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        videoPreviewLayer?.frame = view.layer.bounds
        view.layer.addSublayer(videoPreviewLayer!)

        qrCodeFrameView = UIView()

        if let qrCodeFrameView = qrCodeFrameView {
            qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
            qrCodeFrameView.layer.borderWidth = 2
            view.addSubview(qrCodeFrameView)
            view.bringSubviewToFront(qrCodeFrameView)
        }


    }


    override func viewWillAppear(_ animated: Bool) {
        captureSession.startRunning()

    }

    override func viewWillDisappear(_ animated: Bool) {
        captureSession.stopRunning()
        qrCodeFrameView?.frame = CGRect.zero
    }

}


extension ScannerViewController: AVCaptureMetadataOutputObjectsDelegate {

    func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {
        // Check if the metadataObjects array is not nil and it contains at least one object.
        if metadataObjects.count == 0 {
            qrCodeFrameView?.frame = CGRect.zero
            return
        }


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

        scannerMetadataObj = metadataObj

        let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
        qrCodeFrameView?.frame = barCodeObject!.bounds

        self.testImageView.image = // set image with qr-code
    }

}

扫描二维码后，我想获取二维码的图像并将 testImageView 的图像设置为获取的图像。怎么可能呢？我这样做是因为我想将该图像保存在数据库中以供将来使用。这里我唯一的问题是如何从 videoPreviewLayer 获取二维码图像并将 testImageView 的图像设置为该图像。

Answer 1

您可以在需要时添加 AVCapturePhotoOutput 和 capturePhoto。

1. 在 ScannerViewController 中添加两个属性：

   private let photoOutput = AVCapturePhotoOutput()
   private var isCapturing = false
   

2. 在 viewDidLoad 处将新输出添加到 captureSession：

   captureSession.addOutput(photoOutput)
   

3. 在metadataOutput 方法中调用capturePhoto 并记住捕获状态。因为metadataOutput方法可以被频繁调用：

   let photoSettings = AVCapturePhotoSettings()
   if !isCapturing {
       isCapturing = true
       photoOutput.capturePhoto(with: photoSettings, delegate: self)
   }
   

4. 实现 AVCapturePhotoCaptureDelegate 协议：

   extension ScannerViewController: AVCapturePhotoCaptureDelegate {
       func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
           isCapturing = false
           guard let imageData = photo.fileDataRepresentation() else {
               print("Error while generating image from photo capture data.");
               return
           }
           guard let qrImage = UIImage(data: imageData) else {
               print("Unable to generate UIImage from image data.");
               return
           }
           testImageView.image = qrImage
        }
   }
   

5. 如果需要的话，进行一些额外的照片设置和错误处理也是个好主意。