AVCaptureVideoPreviewLayer 的比例

Question

我目前正在我的 Swift 应用程序中处理 QR 扫描视图。我想在我的视图中间将 VideoPreview 居中。

视图如下所示：

视图（白色）被调用ScanView，我想让图像预览与 的大小相同ScanView并将其居中。

代码片段：

感谢您的每一个帮助！

Answer 1

这是一个有效的解决方案：

import UIKit
import AVFoundation

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureMetadataOutputObjectsDelegate {
  @IBOutlet weak var innerView: UIView!
  var session: AVCaptureSession?
  var input: AVCaptureDeviceInput?
  var previewLayer: AVCaptureVideoPreviewLayer?
    
  override func viewDidLoad() {
    super.viewDidLoad()
    createSession()
  }
    
  override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    self.previewLayer?.frame.size = self.innerView.frame.size
  }
    
  private func createSession() {
    do {
      self.session = AVCaptureSession()
      if let device = AVCaptureDevice.default(for: AVMediaType.video) {
        self.input = try AVCaptureDeviceInput(device: device)
        self.session?.addInput(self.input!)
        self.previewLayer = AVCaptureVideoPreviewLayer(session: self.session!)
        self.previewLayer?.frame.size = self.innerView.frame.size
        self.previewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        self.innerView.layer.addSublayer(self.previewLayer!)

        //______ 1. solution with Video camera ______//
        let videoOutput = AVCaptureVideoDataOutput()
        videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue.main)
        self.session?.canAddOutput(videoOutput)
        self.session?.addOutput(videoOutput)
        self.session?.startRunning()

        //______ 2. solution with QR code ______//
        let videoOutput = AVCaptureMetadataOutput()
        videoOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
        self.session?.canAddOutput(videoOutput)
        self.session?.addOutput(videoOutput)
        // explanation here: /sf/answers/2494999671/
        videoOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.qr]
        self.session?.startRunning()
      }
    } catch _ {
    }
  }

  //MARK: AVCaptureVideoDataOutputSampleBufferDelegate
  public func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
    if let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
        let cameraImage = CIImage(cvPixelBuffer: pixelBuffer)
        // awesome stuff here
    }
  }

  //MARK: AVCaptureMetadataOutputObjectsDelegate
  func setMetadataObjectsDelegate(_ objectsDelegate: AVCaptureMetadataOutputObjectsDelegate?, queue objectsCallbackQueue: DispatchQueue?) {
    
  }
}

要求：

• 设置： Privacy - Camera Usage Description
• innerView 必须初始化，我通过 Storyboard 做了以下约束：

结果如下：