Question

我正在创建一个iPad应用程序，其中一项功能是扫描二维码。我有QR扫描部分工作，但我的问题是iPad屏幕非常大，我将扫描一张纸的小QR码，同时可以看到许多QR码。我想指定显示器的较小区域是唯一可以实际捕获QR码的区域，以便用户更容易扫描他们想要的特定QR码。

我目前已经制作了一个带有红色边框的临时UIView，它以页面为中心，作为我希望用户扫描QR码的示例。它看起来像这样：

我已经全神贯注地找到了如何定位AVCaptureVideoPreviewLayer的特定区域以收集QR码数据的答案，我找到的建议是使用＆＃34; rectOfInterest＆＃34;使用AVCaptureMetadataOutput。我试图这样做，但是当我将rectOfInterest设置为与我用于正确显示的UIView相同的坐标和大小时，我无法扫描/识别任何QR码。有人可以告诉我为什么可扫描区域与看到的UIView的位置不匹配，如何让rectOfInterest在我添加到屏幕的红色边框内？

以下是我目前使用的扫描功能的代码：

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

    // Get an instance of the AVCaptureDeviceInput class using the previous device object.
    var error:NSError?
    let input: AnyObject! = AVCaptureDeviceInput.deviceInputWithDevice(captureDevice, error: &error)

    if (error != nil) {
        // If any error occurs, simply log the description of it and don't continue any more.
        println("\(error?.localizedDescription)")
        return
    }

    // Initialize the captureSession object.
    captureSession = AVCaptureSession()
    // Set the input device on the capture session.
    captureSession?.addInput(input as! AVCaptureInput)

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

    // calculate a centered square rectangle with red border
    let size = 300
    let screenWidth = self.view.frame.size.width
    let xPos = (CGFloat(screenWidth) / CGFloat(2)) - (CGFloat(size) / CGFloat(2))
    let scanRect = CGRect(x: Int(xPos), y: 150, width: size, height: size)

    // create UIView that will server as a red square to indicate where to place QRCode for scanning
    scanAreaView = UIView()
    scanAreaView?.layer.borderColor = UIColor.redColor().CGColor
    scanAreaView?.layer.borderWidth = 4
    scanAreaView?.frame = scanRect

    // Set delegate and use the default dispatch queue to execute the call back
    captureMetadataOutput.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
    captureMetadataOutput.metadataObjectTypes = [AVMetadataObjectTypeQRCode]
    captureMetadataOutput.rectOfInterest = scanRect


    // 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 = view.layer.bounds
    view.layer.addSublayer(videoPreviewLayer)

    // Start video capture.
    captureSession?.startRunning()

    // Initialize QR Code Frame to highlight the QR code
    qrCodeFrameView = UIView()
    qrCodeFrameView?.layer.borderColor = UIColor.greenColor().CGColor
    qrCodeFrameView?.layer.borderWidth = 2
    view.addSubview(qrCodeFrameView!)
    view.bringSubviewToFront(qrCodeFrameView!)

    // Add a button that will be used to close out of the scan view
    videoBtn.setTitle("Close", forState: .Normal)
    videoBtn.setTitleColor(UIColor.blackColor(), forState: .Normal)
    videoBtn.backgroundColor = UIColor.grayColor()
    videoBtn.layer.cornerRadius = 5.0;
    videoBtn.frame = CGRectMake(10, 30, 70, 45)
    videoBtn.addTarget(self, action: "pressClose:", forControlEvents: .TouchUpInside)
    view.addSubview(videoBtn)

    view.addSubview(scanAreaView!)

}

更新我不认为这是重复的原因是因为引用的其他帖子在Objective-C中，而我的代码在Swift中。对于我们这些刚接触iOS的人来说，翻译这两者并不容易。此外，引用帖子的答案并未显示解决其问题的代码中的实际更新。他留下了关于必须使用metadataOutputRectOfInterestForRect方法转换矩形坐标的一个很好的解释，但我似乎仍然无法使这个方法起作用，因为我不清楚如何在没有示例的情况下如何工作。

Answer 1

let metadataOutput = AVCaptureMetadataOutput()
metadataOutput.rectOfInterest = convertRectOfInterest(rect: scanRect)

查看其他来源（https://www.jianshu.com/p/8bb3d8cb224e）后， convertRectOfInterest函数有一个小错误，返回字段应为：

return CGRect(x: newY, y: newX, width: newHeight, height: newWidth)

其中x和y，宽度和高度输入应互换以使其正常工作。

Answer 2

整个上午用import audio1 from './audio1.mp3'; import audio2 from './audio2.mp3'; import audio3 from './audio3.mp3'; import audio4 from './audio4.mp3'; import audio5 from './audio5.mp3'; const audios = { 'audio1': new Audio(audio1), 'audio2': new Audio(audio2), 'audio3': new Audio(audio3), 'audio4': new Audio(audio4), 'audio5': new Audio(audio5) }; let currentlyPlaying = null; const play = (name) => { if (currentlyPlaying) { audios[currentlyPlaying].pause(); } audios[name].play(); currentlyPlaying = name; }; const pause = (name) => { currentlyPlaying = null; audios[name].pause(); }; export default { pause, play };方法战斗后，我厌倦了它并决定自己编写转换。

metedataOutputRectOfInterestForRect

注意：我有一个带方框的图片视图，可向用户显示扫描位置，请务必使用func convertRectOfInterest(rect: CGRect) -> CGRect { let screenRect = self.view.frame let screenWidth = screenRect.width let screenHeight = screenRect.height let newX = 1 / (screenWidth / rect.minX) let newY = 1 / (screenHeight / rect.minY) let newWidth = 1 / (screenWidth / rect.width) let newHeight = 1 / (screenHeight / rect.height) return CGRect(x: newX, y: newY, width: newWidth, height: newHeight) }而不是imageView.frame，以便在屏幕上显示正确的位置。< / p>

这对我来说已经成功。

Answer 3

您需要将UIView的坐标中表示的矩形转换为AVCaptureVideoPreviewLayer的坐标系：

captureMetadataOutput.rectOfInterest = videoPreviewLayer.metadataOutputRectConverted(fromLayerRect: scanRect)

更多信息：https://stackoverflow.com/a/55778152/6898849

Answer 4

这对我有用。

extension AVCaptureVideoPreviewLayer {
    func rectOfInterestConverted(parentRect: CGRect, fromLayerRect: CGRect) -> CGRect {
        let parentWidth = parentRect.width
        let parentHeight = parentRect.height
        let newX = (parentWidth - fromLayerRect.maxX)/parentWidth
        let newY = 1 - (parentHeight - fromLayerRect.minY)/parentHeight
        let width = 1 - (fromLayerRect.minX/parentWidth + newX)
        let height = (fromLayerRect.maxY/parentHeight) - newY

        return CGRect(x: newX, y: newY, width: width, height: height)
    }
}

用法：

    if let rect = videoPreviewLayer?.rectOfInterestConverted(parentRect: self.view.frame, fromLayerRect: scanAreaView.frame) {
        captureMetadataOutput.rectOfInterest = rect
    }

Answer 5

metadataOutput.rectOfInterest = previewLayer.metadataOutputRectConverted(fromLayerRect: yourView.frame)

previewLayer 是 AVCaptureVideoPreviewLayer

如何使用Swift在AVCaptureVideoPreviewLayer的特定区域捕获QR码数据？

5 个答案: