Vision-Face-Quality-Request.swift

private let workQueue = DispatchQueue(label: "VisionRequest", qos: .userInitiated, attributes: [], autoreleaseFrequency: .workItem)

@objc func startVisionRequest(sender: UIButton){
                
        var bestFrameIndex = -1
        var bestThreshold : Float = 0.0

        workQueue.async {
            
            for i in 0..<self.data.count
            {
                guard let cgImage = self.data[i].frameImage.cgImage else {return}
                let request = VNDetectFaceCaptureQualityRequest()
                
                
                let requestHandler = VNImageRequestHandler(cgImage: cgImage, options: [:])
                do{
                    try requestHandler.perform([request])
                    if let faceObservation = request.results?.first as? VNFaceObservation{
                        if let faceCaptureQuality = faceObservation.faceCaptureQuality{
                            self.data[i].faceQualityValue = "\(faceCaptureQuality)"
                            if faceCaptureQuality > bestThreshold{
                                bestThreshold = faceCaptureQuality
                                bestFrameIndex = i
                            }
                        }
                    }
                    else{
                        self.data[i].faceQualityValue = "0.00"
                    }

                }catch(let error){
                    print(error.localizedDescription)
                }
            }
            
            DispatchQueue.main.async {
                self.collectionView.reloadData()
                if bestFrameIndex != -1{
                    self.imageView?.image = self.data[bestFrameIndex].frameImage
                }
            }
        }
    }