iOS: 检测拍摄的图片中是否有人脸

最近开发的app中有个实名认证的环节，需要上传一张自拍照，为了检测用
户上传审核的是人脸照片而非其他的东西，就用到了系统自带的检测人脸的方
法，废话不多说直接上代码：

- (BOOL)detectionOfFaceWithImage:(UIImage *)image {
    NSDictionary *imageOptions = [NSDictionary dictionaryWithObject:@(5) forKey:CIDetectorImageOrientation];
    CIImage *personciImage = [CIImage imageWithCGImage:image.CGImage];
    NSDictionary *opts = [NSDictionary dictionaryWithObject:CIDetectorAccuracyHigh forKey:CIDetectorAccuracy];
    CIDetector *faceDetector = [CIDetector detectorOfType:CIDetectorTypeFace context:nil options:opts];
    NSArray *features = [faceDetector featuresInImage:personciImage options:imageOptions];
    if (features.count > 0) return YES; else return NO;
}

检测到人脸.png