CoreImage识别相机的人脸

import UIKit

class CameraViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    @IBOutlet weak var imageView: UIImageView!
    let imagePicker = UIImagePickerController()
    override func viewDidLoad() {
        super.viewDidLoad()
        imagePicker.delegate = self;
    }
    
    @IBAction func takePhoto(_ sender: Any) {
        if !UIImagePickerController.isSourceTypeAvailable(.camera) {
            return
        }
        imagePicker.allowsEditing = false
        imagePicker.sourceType = .camera
        present(imagePicker, animated: true, completion: nil)
    }
    
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        if let pickerImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
            imageView.contentMode = .scaleAspectFit
            imageView.image = pickerImage
        }
        dismiss(animated: true, completion: nil)
        self.detect()
    }
    
    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        dismiss(animated: true, completion: nil)
    }
    
    func detect() {
        let imageOptions = NSDictionary(object: NSNumber(value: 5) as NSNumber, forKey: CIDetectorImageOrientation as NSString)
        let personCiImage = CIImage(cgImage: imageView.image!.cgImage!)
        let accuracy = [CIDetectorAccuracy: CIDetectorAccuracyHigh]
        let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: nil, options: accuracy)
        let faces = faceDetector?.features(in: personCiImage, options: imageOptions as? [String : AnyObject])
        
        if let face = faces?.first as? CIFaceFeature {
            print("found bounds are \(face.bounds)")
            
            let alert = UIAlertController(title: "Say Cheese!", message: "We detected a face!", preferredStyle: UIAlertControllerStyle.alert)
            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
            self.present(alert, animated: true, completion: nil)
            
            if face.hasSmile {
                print("face is smiling");
            }
            
            if face.hasLeftEyePosition {
                print("Left eye bounds are \(face.leftEyePosition)")
            }
            
            if face.hasRightEyePosition {
                print("Right eye bounds are \(face.rightEyePosition)")
            }
        } else {
            let alert = UIAlertController(title: "No Face!", message: "No face was detected", preferredStyle: UIAlertControllerStyle.alert)
            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil))
            self.present(alert, animated: true, completion: nil)
        }
    }
    
}