iOS图像处理——人脸识别

主要用于身份识别。

人脸识别开发

人脸识别过程一般分为3个步骤：

1. 建立人脸的面纹数据库；
2. 获取单签人脸面像图片；
3. 进行比对；

面纹编码可靠性强，可以精确地辨认出某个人。

iOS5之后，通过CIDetector可以获取眼睛和嘴的特征信息，但是并不包括面纹编码提取。

CIDetector能做的是找到一张图片中的人脸，但是这张脸是谁的，无法判断。

之前可以用OpenCV和Face.com来实现。

实例：是猩猩还是小女孩

- (IBAction)detexct:(id)sender {
    CIContext *context = [CIContext contextWithOptions:nil];
    
    UIImage *imageInput = [_inputImageView image];
    CIImage *image = [CIImage imageWithCGImage:imageInput.CGImage];
    
    //设置识别参数
    NSDictionary *param = @{CIDetectorAccuracy : CIDetectorAccuracyHigh};
    //声明一个CIDetecor，并设定识别类型
    CIDetector *faceDetector = [CIDetector detectorOfType:CIDetectorTypeFace context:context options:param];
    //取得识别结果
    NSArray *detectResult = [faceDetector featuresInImage:image];
    
    UIView *resultView = [[UIView alloc] initWithFrame:_inputImageView.frame];
    [self.view addSubview:resultView];
    
    [detectResult enumerateObjectsUsingBlock:^(CIFaceFeature *faceFeature, NSUInteger idx, BOOL * _Nonnull stop)
    {
        //脸部
        UIView *faceView = [[UIView alloc] initWithFrame:faceFeature.bounds];
        faceView.layer.borderWidth = 1;
        faceView.layer.borderColor = [UIColor orangeColor].CGColor;
        [resultView addSubview:faceView];
        //左眼
        if (faceFeature.hasLeftEyePosition)
        {
            UIView *leftEyeView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 5, 5)];
            [leftEyeView setCenter:faceFeature.leftEyePosition];
            leftEyeView.layer.borderWidth = 1;
            leftEyeView.layer.borderColor = [UIColor redColor].CGColor;
            [resultView addSubview:leftEyeView];
        }
        //嘴巴
        if (faceFeature.hasMouthPosition)
        {
            UIView *mouthView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 10, 5)];
            [mouthView setCenter:faceFeature.mouthPosition];
            mouthView.layer.borderWidth = 1;
            mouthView.layer.borderColor = [UIColor redColor].CGColor;
            [resultView addSubview:mouthView];
        }
    }];
    
    [resultView setTransform:CGAffineTransformMakeScale(1, -1)];
    
    if (detectResult.count > 0)
    {
        CIImage *faceImage = [image imageByCroppingToRect:[detectResult[0] bounds]];
        UIImage *face = [UIImage imageWithCGImage:[context createCGImage:faceImage fromRect:faceImage.extent]];
        
        _outputImageView.image = face;
    }
}