iOS11 Vision.frameworkで顔トラッキング

はじめに

リアルタイムテキスト検出を行っている、こちらの有難いソースを一部修正すればできます。
元記事はこちらをご参照ください。

ソース（変更する部分のみ）

    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        let uiImage = sampleBufferToUIImage(sampleBuffer: sampleBuffer, with: UIApplication.shared.statusBarOrientation)
        let orientation = CGImagePropertyOrientation(uiImage.imageOrientation)
        let ciImage = CIImage(image: uiImage)!

        // UI の変更はメインスレッドで実行
        DispatchQueue.main.async { [weak self] in
            if let frame = self?.imageFrameOnViewController(uiImage: uiImage) {
                self?.imageView.image = uiImage
                self?.visualizeRectanglesView.frame = frame
            }
        }

        // orientation を必ず設定すること
//        let handler = VNImageRequestHandler(ciImage: ciImage, orientation: Int32(orientation.rawValue))
        let handler = VNImageRequestHandler(ciImage: ciImage, orientation: orientation)

//        let request = VNDetectTextRectanglesRequest() { request, error in
        let request = VNDetectFaceRectanglesRequest() { request, error in
            // 顔ブロックの矩形を取得
            let rects = request.results?.flatMap { result -> [CGRect] in
//                guard let observation = result as? VNTextObservation else { return [] }
                guard let observation = result as? VNFaceObservation else { return [] }
                return [observation.boundingBox]
            } ?? []

//            // 文字ごとの矩形を取得
//            let characterRects = request.results?.flatMap { result -> [VNRectangleObservation] in
//                //guard let observation = result as? VNTextObservation else { return [] }
//                guard let observation = result as? VNFaceObservation else { return [] }
//                return observation.characterBoxes ?? []
//            } ?? []

            // UI の変更はメインスレッドで実行
            DispatchQueue.main.async { [weak self] in
                self?.visualizeRectanglesView.rectangles = rects
//                self?.visualizeRectanglesView.characterRectangles = characterRects
            }
        }

//        request.reportCharacterBoxes = true

        try! handler.perform([request])
    }