swift 的相机扫描

func scaning(){

        //获取摄像设备
        guard let device = AVCaptureDevice.default(for: .video) else { return }

        //输入流
        let input: AVCaptureDeviceInput
        do{
            input  = try AVCaptureDeviceInput.init(device: device)
        }catch{
            return
        }

        //输出流
        let output = AVCaptureMetadataOutput()
        //设置代理,并且在主线程刷新
        output.setMetadataObjectsDelegate(self, queue:DispatchQueue.main)
        output.rectOfInterest = CGRect(x: kScreenWidth/2-100, y: kScreenHeight/2-100, width: 200/kScreenWidth, height: 200/kScreenHeight)

        //初始化链接对象 / 高质量采集率
        session = AVCaptureSession()
        session.canSetSessionPreset(.high)

        if session.canAddInput(input) {
            session.addInput(input)
        }else {
            failed()
            return
        }

        if session.canAddOutput(output) {
            session.addOutput(output)
        }else {
            failed()
            return
        }

        //先添加输入输出流,后设置支持的扫码所支持的格式,不然报错
        //设置扫码支持的编码格式
        output.metadataObjectTypes = [.ean8, .ean13, .code128, .qr]

        preview = AVCaptureVideoPreviewLayer(session: session)
        preview.videoGravity = .resizeAspectFill
        preview.connection?.videoOrientation = .portrait
        preview.frame = view.bounds
        view.layer.insertSublayer(preview, at: 0)

        //开始捕捉
        session.startRunning()
    }

修改：output 的 restOfInterest应该为：

output.rectOfInterest = CGRect(x: (kScreenHeight/2-100)/kScreenHeight, y: (kScreenWidth/2-100)/kScreenWidth, width: 200/kScreenHeight, height: 200/kScreenWidth)