版本记录

前言

iOS 11+和macOS 10.13+ 新出了Vision框架，提供了人脸识别、物体检测、物体跟踪等技术，它是基于Core ML的。可以说是人工智能的一部分，接下来几篇我们就详细的解析一下Vision框架。感兴趣的看下面几篇文章。
1. Vision框架详细解析（一） —— 基本概览（一）
2. Vision框架详细解析（二） —— 基于Vision的人脸识别（一）
3. Vision框架详细解析（三） —— 基于Vision的人脸识别（二）
4. Vision框架详细解析（四） —— 在iOS中使用Vision和Metal进行照片堆叠（一）
5. Vision框架详细解析（五） —— 在iOS中使用Vision和Metal进行照片堆叠（二）
6. Vision框架详细解析（六） —— 基于Vision的显著性分析（一）
7. Vision框架详细解析（七） —— 基于Vision的显著性分析（二）
8. Vision框架详细解析（八） —— 基于Vision的QR扫描（一）

源码

1. Swift

首先看下工程组织结构：

下面就是源码了

1. ViewController.swift

import UIKit
import Vision
import AVFoundation
import SafariServices

class ViewController: UIViewController {
  // MARK: - Private Variables
  var captureSession = AVCaptureSession()

  // TODO: Make VNDetectBarcodesRequest variable
  lazy var detectBarcodeRequest = VNDetectBarcodesRequest { request, error in
    guard error == nil else {
      self.showAlert(withTitle: "Barcode error", message: error?.localizedDescription ?? "error")
      return
    }
    self.processClassification(request)
  }

  // MARK: - Override Functions
  override func viewDidLoad() {
    super.viewDidLoad()
    checkPermissions()
    setupCameraLiveView()
  }
  override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    // TODO: Stop Session
    captureSession.stopRunning()
  }
}


extension ViewController {
  // MARK: - Camera
  private func checkPermissions() {
    // TODO: Checking permissions
    switch AVCaptureDevice.authorizationStatus(for: .video) {
    case .notDetermined:
      AVCaptureDevice.requestAccess(for: .video) { [self] granted in
        if !granted {
          self.showPermissionsAlert()
        }
      }
    case .denied, .restricted:
      showPermissionsAlert()
    default:
      return
    }
  }

  private func setupCameraLiveView() {
    // TODO: Setup captureSession
    captureSession.sessionPreset = .hd1280x720

    // TODO: Add input
    let videoDevice = AVCaptureDevice
      .default(.builtInWideAngleCamera, for: .video, position: .back)

    guard
      let device = videoDevice,
      let videoDeviceInput = try? AVCaptureDeviceInput(device: device),
      captureSession.canAddInput(videoDeviceInput) else {
        showAlert(
          withTitle: "Cannot Find Camera",
          message: "There seems to be a problem with the camera on your device.")
        return
      }

    captureSession.addInput(videoDeviceInput)

    // TODO: Add output
    let captureOutput = AVCaptureVideoDataOutput()
    // TODO: Set video sample rate
    captureOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32BGRA)]
    captureOutput.setSampleBufferDelegate(self, queue: DispatchQueue.global(qos: DispatchQoS.QoSClass.default))
    captureSession.addOutput(captureOutput)

    configurePreviewLayer()

    // TODO: Run session
    captureSession.startRunning()
  }

  // MARK: - Vision
  func processClassification(_ request: VNRequest) {
    // TODO: Main logic
    guard let barcodes = request.results else { return }
    DispatchQueue.main.async { [self] in
      if captureSession.isRunning {
        view.layer.sublayers?.removeSubrange(1...)

        for barcode in barcodes {
          guard
            // TODO: Check for QR Code symbology and confidence score
            let potentialQRCode = barcode as? VNBarcodeObservation,
            potentialQRCode.symbology == .QR,
            potentialQRCode.confidence > 0.9
            else { return }

          observationHandler(payload: potentialQRCode.payloadStringValue)
        }
      }
    }
  }

  // MARK: - Handler
  func observationHandler(payload: String?) {
    // TODO: Open it in Safari
    guard
      let payloadString = payload,
      let url = URL(string: payloadString),
      ["http", "https"].contains(url.scheme?.lowercased())
    else { return }

    let config = SFSafariViewController.Configuration()
    config.entersReaderIfAvailable = true

    let safariVC = SFSafariViewController(url: url, configuration: config)
    safariVC.delegate = self
    present(safariVC, animated: true)
  }
}


// MARK: - AVCaptureDelegation
extension ViewController: AVCaptureVideoDataOutputSampleBufferDelegate {
  func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
    // TODO: Live Vision
    guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }

    let imageRequestHandler = VNImageRequestHandler(
      cvPixelBuffer: pixelBuffer,
      orientation: .right)

    do {
      try imageRequestHandler.perform([detectBarcodeRequest])
    } catch {
      print(error)
    }
  }
}


// MARK: - Helper
extension ViewController {
  private func configurePreviewLayer() {
    let cameraPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    cameraPreviewLayer.videoGravity = .resizeAspectFill
    cameraPreviewLayer.connection?.videoOrientation = .portrait
    cameraPreviewLayer.frame = view.frame
    view.layer.insertSublayer(cameraPreviewLayer, at: 0)
  }

  private func showAlert(withTitle title: String, message: String) {
    DispatchQueue.main.async {
      let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
      alertController.addAction(UIAlertAction(title: "OK", style: .default))
      self.present(alertController, animated: true)
    }
  }

  private func showPermissionsAlert() {
    showAlert(
      withTitle: "Camera Permissions",
      message: "Please open Settings and grant permission for this app to use your camera.")
  }
}


// MARK: - SafariViewControllerDelegate
extension ViewController: SFSafariViewControllerDelegate {
  func safariViewControllerDidFinish(_ controller: SFSafariViewController) {
    captureSession.startRunning()
  }
}

后记

本篇主要讲述了基于Vision的QR扫描，感兴趣的给个赞或者关注~~~