实时视频框上的iOS人脸检测在人脸周围重复

Question

我正在和Apples CIDetector玩耍，以使用手机的前置摄像头从实时视频中检测到面部。我一直在关注这个article，并且几乎可以正常使用。我遇到的问题是，在每个帧上都会创建一个新的红色框，而不是重复使用相同的框。

我正在遵循的教程旨在编写代码来阻止这种情况的发生，但是它似乎没有用。我对Swift还是很陌生，正在努力解决。

这是我正在使用的代码：

    func drawFaceMasksFor(features: [CIFaceFeature], bufferFrame: CGRect) {

    CATransaction.begin()
    CATransaction.setValue(kCFBooleanTrue, forKey: kCATransactionDisableActions)

    //Hide all current masks
    view.layer.sublayers?.filter({ $0.name == "MaskFace" }).forEach { $0.isHidden = true }

    //Do nothing if no face is dected
    guard !features.isEmpty else {
        CATransaction.commit()
        return
    }

    //The problem is we detect the faces on video image size
    //but when we show on the screen which might smaller or bigger than your video size
    //so we need to re-calculate the faces bounds to fit to your screen

    let xScale = view.frame.width / bufferFrame.width
    let yScale = view.frame.height / bufferFrame.height
    let transform = CGAffineTransform(rotationAngle: .pi).translatedBy(x: -bufferFrame.width,
                                                                       y: -bufferFrame.height)

    for feature in features {
        var faceRect = feature.bounds.applying(transform)
        faceRect = CGRect(x: faceRect.minX * xScale,
                          y: faceRect.minY * yScale,
                          width: faceRect.width * xScale,
                          height: faceRect.height * yScale)

        //Reuse the face's layer
        var faceLayer = view.layer.sublayers?
            .filter { $0.name == "MaskFace" && $0.isHidden == true }
            .first
        if faceLayer == nil {                
            // prepare layer
            faceLayer = CALayer()
            faceLayer?.backgroundColor = UIColor.clear.cgColor
            faceLayer?.borderColor = UIColor.red.cgColor
            faceLayer?.borderWidth = 3.0
            faceLayer?.frame = faceRect
            faceLayer?.masksToBounds = true
            faceLayer?.contentsGravity = kCAGravityResizeAspectFill
            view.layer.addSublayer(faceLayer!)

        } else {
            faceLayer?.frame = faceRect
            faceLayer?.position = faceRect.origin
            faceLayer?.isHidden = false
        }

        //You can add some masks for your left eye, right eye, mouth
    }

    CATransaction.commit()
}