Facial Recognition using CIDetector.

CoreImageFacialRecognition.swift

import UIKit
import CoreImage


extension UIImage {
    /** Returns an Array of all detected faces as *UIImages.* If none are found empty Array will be returned.
    - Author: Kai Aldag
    */
    func findFacesInImage() throws -> [UIImage] {
        guard let image = UIKit.CIImage(image: self),
              let detector = CIDetector(ofType: CIDetectorTypeFace,
                                        context: nil,
                                        options: nil) else { throw FacialRecognitionError.internalError }

        let faces = detector.features(in: image)

        let images: [UIImage] = faces.flatMap { feature -> UIImage? in
            guard let face = feature as? CIFaceFeature,
                let ciFaceImage = UIKit.CIImage(image: self)?.cropping(to: face.bounds)
                else { return nil }
            return UIImage(ciImage: ciFaceImage, scale: 0.9, orientation: imageOrientation)
        }

        return images
    }
}

enum FacialRecognitionError: Error {
    case internalError
}