如何仅在CGRect中使用Apple Vision检测条形码?

Question

我有一个应用程序，使用CGRect(x: 0, y: 0, width: 335, height: 150)来显示条形码扫描的相机。但当条形码相机CGRect中(不)会扫描。如何将扫描区域限制为预览层中的CGRect ?

let captureSession = AVCaptureSession()
var previewLayer: AVCaptureVideoPreviewLayer!
var activeInput: AVCaptureDeviceInput!
lazy var detectBarcodeRequest = VNDetectBarcodesRequest { request, error in
guard error == nil else {

print("Barcode Error: (String(describing: error?.localizedDescription))")

return
}

self.processBarCode(request)
}
override func viewDidLoad() {
super.viewDidLoad()

setupSession()
setupPreview()
startSession()
}
func setupSession() {

guard let camera = AVCaptureDevice.default(for: .video) else {
return

}
do {
let videoInput = try AVCaptureDeviceInput(device: camera)

for input in [videoInput] {
if captureSession.canAddInput(input) {
captureSession.addInput(input)
}
}
activeInput = videoInput
} catch {
print("Error setting device input: (error)")
return
}

let captureOutput = AVCaptureVideoDataOutput()

captureOutput.videoSettings = [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32BGRA)]
captureOutput.setSampleBufferDelegate(self, queue: DispatchQueue.global(qos: DispatchQoS.QoSClass.default))

captureSession.addOutput(captureOutput)
}
func setupPreview() {

previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

previewLayer.videoGravity = .resizeAspectFill
previewLayer.connection?.videoOrientation = .portrait
previewLayer.frame = CGRect(x: 0, y: 0, width: 335, height: 150)

view.layer.insertSublayer(previewLayer, at: 0)
}//setupPreview
func startSession() {
if !captureSession.isRunning {
DispatchQueue.global(qos: .default).async { [weak self] in
self?.captureSession.startRunning()
}
}
}
// MARK: - processBarCode
func processBarCode(_ request: VNRequest) {


DispatchQueue.main.async {
guard let results = request.results as? [VNBarcodeObservation] else {
return
}

if let payload = results.first?.payloadStringValue, let symbology = results.first?.symbology {
print("payload is (payload) (symbology) ")

}

}

}//processBarCode

<标题>编辑:

// MARK: - AVCaptureVideoDataOutputSampleBufferDelegate
extension CameraViewController: AVCaptureVideoDataOutputSampleBufferDelegate {

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {

guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }

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

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

}//extension

Answer 1

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 2

您可以使用VNDetectBarcodesRequest的regionOfInterest属性来设置检测区域。根据Apple文档

，默认值为{{0,0}，{1,1}}。

Answer 3

在func captureOutput(_:didOutput:from:)中，您最有可能将整个图像传递到VNImageRequestHandler.
相反，您需要裁剪图像到您的可见矩形。
另一种方法是通过regionOfInterest将视觉锁定为图像的可见部分，如下面的@飓风onthemoon建议。