iOS 11之Vision人脸检测

>大道如青天，我独不得出

#####前言
在上一篇`iOS Core ML与Vision初识`中，初步了解到了`vision`的作用，并在文章最后留了个疑问，就是类似下面的一些函数有什么用
```
- (instancetype)initWithCIImage:(CIImage *)image options:(NSDictionary<VNImageOption, id> *)options;

- (instancetype)initWithCVPixelBuffer:(CVPixelBufferRef)pixelBuffer options:(NSDictionary<VNImageOption, id> *)options;
```
在查阅一些资料后，最终通过这些函数得到了如下的效果

![face.gif](/contentImages/image/jianshu/2525768-c45ee7c16299c64a.gif)
对，没错，这就是通过`initWithCVPixelBuffer`函数来实现的。当然`vision`的作用远不于此，还有如下的效果
1、图像匹配（上篇文章中的效果）
2、矩形检测
3、二维码、条码检测
4、目标跟踪
5、文字检测
6、人脸检测
7、人脸面部特征检测
由于对人脸识别比较感兴趣，所以这里就主要简单了解了下人脸部分，下面就针对人脸检测和面部检测写写

#####Vision支持的图片类型
通过查看`VNRequestHandler.h`文件，我们可以看到里面的所有初始化函数，通过这些初始化函数，我们可以了解到支持的类型有：
1、`CVPixelBufferRef`
2、`CGImageRef`
3、`CIImage`
4、`NSURL`
5、`NSData`

#####Vision使用
在使用`vision`的时候，我们首先需要明确自己需要什么效果，然后根据想要的效果来选择不同的类，最后实现自己的效果
1、需要一个`RequestHandler`，在创建`RequestHandler`的时候，需要一个合适的输入源，及`图片`类型
2、需要一个`Request `，在创建`Request `的时候，也需要根据实际情况来选择，`Request `大概有如下这么些

![request.jpeg](/contentImages/image/jianshu/2525768-cc3cd22263666ea1.jpeg)
3、通过`requestHandler`将`request`联系起来，然后得到结果
```
[handler performRequests:@[requset] error:&error];
```
4、处理结果`VNObservation`，在`VNRequest`的`results`数组中，包含了`VNObservation`结果，`VNObservation`也分很多种，这和你`Request`的类型是相关联的

![Vision结果继承关系.png](/contentImages/image/jianshu/2525768-deced22145c609ef.png)

在完成上述步骤后，我们就可以根据结果来实现一些我们想要的效果

#####人脸矩形检测
这里我们需要用到`VNDetectFaceRectanglesRequest`
```
requset = [[VNDetectFaceRectanglesRequest alloc] initWithCompletionHandler:completionHandler];
```
在得到结果后，我们需要处理下坐标
```
    for (VNFaceObservation *faceObservation in observations) {
        //boundingBox
        CGRect transFrame = [self convertRect:faceObservation.boundingBox imageSize:image.size];
        [rects addObject:[NSValue valueWithCGRect:transFrame]];
    }
```

```
// 转换Rect
- (CGRect)convertRect:(CGRect)boundingBox imageSize:(CGSize)imageSize{
    CGFloat w = boundingBox.size.width * imageSize.width;
    CGFloat h = boundingBox.size.height * imageSize.height;
    CGFloat x = boundingBox.origin.x * imageSize.width;
    CGFloat y = imageSize.height * (1 - boundingBox.origin.y - boundingBox.size.height);//- (boundingBox.origin.y * imageSize.height) - h;
    return CGRectMake(x, y, w, h);
}
```
在返回结果中的`boundingBox `中的坐标，我们并不能立即使用，而是需要进行转换，因为这里是相对于`image`的一个比例，这里需要注意的是`y`坐标的转换，因为坐标系的`y`轴和`UIView`的`y`轴是相反的。
最后就是通过返回的坐标进行矩形的绘制
```
+ (UIImage *)gl_drawImage:(UIImage *)image withRects:(NSArray *)rects
{
    UIImage *newImage = nil;
    UIGraphicsBeginImageContextWithOptions(image.size, NO, [UIScreen mainScreen].scale);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetLineCap(context,kCGLineCapRound); //边缘样式
    CGContextSetLineJoin(context, kCGLineJoinRound);
    CGContextSetLineWidth(context,2); //线宽
    CGContextSetAllowsAntialiasing(context,YES); //打开抗锯齿
    CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
    CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
    
    //绘制图片
    [image drawInRect:CGRectMake(0, 0,image.size.width, image.size.height)];
    CGContextBeginPath(context);
    for (int i = 0; i < rects.count; i ++) {
        CGRect rect = [rects[i] CGRectValue];
        CGPoint sPoints[4];//坐标点
        sPoints[0] = CGPointMake(rect.origin.x, rect.origin.y);//坐标1
        sPoints[1] = CGPointMake(rect.origin.x + rect.size.width, rect.origin.y);//坐标2
        sPoints[2] = CGPointMake(rect.origin.x + rect.size.width, rect.origin.y + rect.size.height);//坐标3
        sPoints[3] = CGPointMake(rect.origin.x , rect.origin.y + rect.size.height);
        
        CGContextAddLines(context, sPoints, 4);//添加线
        CGContextClosePath(context); //封闭
    }
    CGContextDrawPath(context, kCGPathFillStroke); //根据坐标绘制路径
    
    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}
```
效果如下

![faceRect.jpg](/contentImages/image/jianshu/2525768-a5febef321afbcaf.jpg)

#####人脸特征识别
这里我们需要用到`VNDetectFaceLandmarksRequest`
```
            requset = [[VNDetectFaceLandmarksRequest alloc] initWithCompletionHandler:completionHandler];

```
处理结果
```
    for (VNFaceObservation *faceObservation in observations) {
        //boundingBox
        CGRect transFrame = [self convertRect:faceObservation.boundingBox imageSize:image.size];
        [rects addObject:[NSValue valueWithCGRect:transFrame]];
    }
    pointModel.faceRectPoints = rects;
    return pointModel;
}

- (GLDiscernPointModel *)handlerFaceLandMark:(NSArray *)observations image:(UIImage *)image
{
    GLDiscernPointModel *pointModel = [[GLDiscernPointModel alloc] init];
    NSMutableArray *rects = @[].mutableCopy;

for (VNFaceObservation *faceObservation in observations) {
        
        VNFaceLandmarks2D *faceLandMarks2D = faceObservation.landmarks;
        
        [self getKeysWithClass:[VNFaceLandmarks2D class] block:^(NSString *key) {
            if ([key isEqualToString:@"allPoints"]) {
                return ;
            }
            VNFaceLandmarkRegion2D *faceLandMarkRegion2D = [faceLandMarks2D valueForKey:key];
            
            NSMutableArray *sPoints = [[NSMutableArray alloc] initWithCapacity:faceLandMarkRegion2D.pointCount];
            
            for (int i = 0; i < faceLandMarkRegion2D.pointCount; i ++) {
                CGPoint point = faceLandMarkRegion2D.normalizedPoints[i];
                
                CGFloat rectWidth = image.size.width * faceObservation.boundingBox.size.width;
                CGFloat rectHeight = image.size.height * faceObservation.boundingBox.size.height;
                CGPoint p = CGPointMake(point.x * rectWidth + faceObservation.boundingBox.origin.x * image.size.width, faceObservation.boundingBox.origin.y * image.size.height + point.y * rectHeight);
                [sPoints addObject:[NSValue valueWithCGPoint:p]];
            }
            
            [rects addObject:sPoints];
        }];
    }
```
在这里，我们需要注意到`landmarks `这个属性，这是一个`VNFaceLandmarks2D`类型的对象，里面包含着许多面部特征的`VNFaceLandmarkRegion2D`对象，如：`faceContour`，`leftEye`，`nose`....分别表示面部轮廓、左眼、鼻子。这些对象中，又包含下面这么一个属性
```
@property (readonly, assign, nullable) const CGPoint* normalizedPoints
```
这是一个包含该面部特征的的数组，所以我们可以通过下面的方式取出里面的坐标
```
CGPoint point = faceLandMarkRegion2D.normalizedPoints[i];
```
当然这里面也存在坐标的转换，见上面代码
最后也是画线，代码如下
```
+ (UIImage *)gl_drawImage:(UIImage *)image faceLandMarkPoints:(NSArray *)landMarkPoints
{
    UIImage * newImage = image;
    for (NSMutableArray *points in landMarkPoints) {
        
        CGPoint sPoints [points.count];
        
        for (int i = 0;i <points.count;i++) {
            NSValue *pointValue = points[i];
            CGPoint point = pointValue.CGPointValue;
            sPoints[i] = point;
        }
        //画线
        UIGraphicsBeginImageContextWithOptions(newImage.size, NO, [UIScreen mainScreen].scale);
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSetLineCap(context,kCGLineCapRound); //边缘样式
        CGContextSetLineJoin(context, kCGLineJoinRound);
        CGContextSetLineWidth(context,2); //线宽
        CGContextSetAllowsAntialiasing(context,YES); //打开抗锯齿
        // 设置翻转
        CGContextTranslateCTM(context, 0, newImage.size.height);
        CGContextScaleCTM(context, 1.0, -1.0);
        
        CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);
        CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
        
        CGContextDrawImage(context, CGRectMake(0, 0,newImage.size.width,newImage.size.height), newImage.CGImage);
        
        CGContextBeginPath(context);
        CGContextAddLines(context, sPoints,points.count);//添加线
        CGContextClosePath(context); //封闭
        CGContextDrawPath(context, kCGPathFillStroke); //根据坐标绘制路径
        newImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    return newImage;
}

```
效果如下

![faceLandmark.png](/contentImages/image/jianshu/2525768-8560904c9eaf5f52.png)

#####动态人脸矩形检测
要动态来检测，那么我们肯定需要通过相机来实时取出资源，然后再实现，所以我们这里选择了`AVCapture`，关于相机的初始化及使用方法这里就不在累赘了，我们直接上代码
在`AVCaptureVideoDataOutputSampleBufferDelegate`中，通过下面的方法
```
- (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection

```
我们可以进行这么一个转换
```
CVPixelBufferRef cvpixeBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer);
```
然后通过
```
    VNImageRequestHandler *handler = [[VNImageRequestHandler alloc] initWithCVPixelBuffer:cvpixeBufferRef options:@{}];

```
将相机返回的图片与`request`进行关联了。
后续操作如下
```
            request = [[VNDetectFaceRectanglesRequest alloc] initWithCompletionHandler:^(VNRequest * _Nonnull request, NSError * _Nullable error) {
                
                NSLog(@" 打印信息:%lu",request.results.count);
                NSArray *vnobservations = request.results;
                
                dispatch_async(dispatch_get_main_queue(), ^{
                    //先移除之前的矩形框
                    [self.rectLayers makeObjectsPerformSelector:@selector(removeFromSuperlayer)];

AVCaptureDevicePosition position = [[self.avInput device] position];

for (VNFaceObservation *faceObservation in vnobservations) {
                        //boundingBox
                        CGRect transFrame = [[GLTools sharedInstance] convertRect:faceObservation.boundingBox imageSize:self.view.frame.size];
                        //前置摄像头的时候 记得转换
                        if (position == AVCaptureDevicePositionFront){
                            transFrame.origin.x = self.view.frame.size.width - transFrame.origin.x - transFrame.size.width;
                        }
                        
                        CALayer *rectLayer = [CALayer layer];
                        rectLayer.frame = transFrame;
                        rectLayer.borderColor = [UIColor purpleColor].CGColor;
                        rectLayer.borderWidth = 2;
                        [self.view.layer addSublayer:rectLayer];
                        
                        [self.rectLayers addObject:rectLayer];
                    }
                });
            }];
```
在这里存在一个问题，就是摄像头分为前后摄像头，所以在前置摄像头和后置摄像头切换的时候，需要重新配置下
```
            //需要重新进行配置输出 特别是下面的输出方向
            AVCaptureConnection *captureConnection = [self.avOutput connectionWithMediaType:AVMediaTypeVideo];
            if ([captureConnection isVideoOrientationSupported]) {
                [captureConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];
            }
            // 视频稳定设置
            if ([captureConnection isVideoStabilizationSupported]) {
                captureConnection.preferredVideoStabilizationMode = AVCaptureVideoStabilizationModeAuto;
            }
            // 设置输出图片方向
            captureConnection.videoOrientation = AVCaptureVideoOrientationPortrait;
```
还有个问题就是在坐标转化的时候，前置摄像头的`x`轴和`UIView`的`x`轴也是相反的，所以这里也需要在进行一次转化
```
 transFrame.origin.x = self.view.frame.size.width - transFrame.origin.x - transFrame.size.width;

```
效果如下

![动态1.gif](/contentImages/image/jianshu/2525768-66b667e7e5d9a9e5.gif)

#####动态添加场景
关于动态添加场景，其实就像我们平时用的美颜相机那样，在适当的位置添加些帽子、眼镜等各种搞笑的图片。这里我们还是需要用到`AVCapture `，并且和动态添加矩形的方法类似，只是在`request`上和处理方式上不一样
下面我们先看代码
```
            request = [[VNDetectFaceLandmarksRequest alloc] initWithCompletionHandler:^(VNRequest * _Nonnull request, NSError * _Nullable error) {
                NSArray *vnobservations = request.results;
                
                
                for (VNFaceObservation *faceObservation in vnobservations) {
                    
                    
                    VNFaceLandmarks2D *faceLandMarks2D = faceObservation.landmarks;
                    
                    VNFaceLandmarkRegion2D *leftEyefaceLandMarkRegion2D = faceLandMarks2D.leftEye;
                    VNFaceLandmarkRegion2D *rightEyefaceLandMarkRegion2D = faceLandMarks2D.rightEye;
                    
                    dispatch_async(dispatch_get_main_queue(), ^{
                        
//                        //先移除之前的矩形框
//                        [self.rectLayers makeObjectsPerformSelector:@selector(removeFromSuperlayer)];
//
//                        AVCaptureDevicePosition position = [[self.avInput device] position];
//
//                        CGRect transFrame = [[GLTools sharedInstance] convertRect:faceObservation.boundingBox imageSize:self.view.frame.size];
//                        //前置摄像头的时候 记得转换
//                        if (position == AVCaptureDevicePositionFront){
//                            transFrame.origin.x = self.view.frame.size.width - transFrame.origin.x - transFrame.size.width;
//                        }
//
//                        CALayer *rectLayer = [CALayer layer];
//                        rectLayer.frame = transFrame;
//                        rectLayer.borderColor = [UIColor purpleColor].CGColor;
//                        rectLayer.borderWidth = 2;
//                        [self.view.layer addSublayer:rectLayer];
//
//                        [self.rectLayers addObject:rectLayer];
                        
                        AVCaptureDevicePosition position = [[self.avInput device] position];

CGPoint sPoints[leftEyefaceLandMarkRegion2D.pointCount + rightEyefaceLandMarkRegion2D.pointCount];
                        
                        NSMutableArray *pointXs = [[NSMutableArray alloc] init];
                        NSMutableArray *pointYs = [[NSMutableArray alloc] init];
                        
                        for (int i = 0; i < leftEyefaceLandMarkRegion2D.pointCount; i ++) {
                            CGPoint point = leftEyefaceLandMarkRegion2D.normalizedPoints[i];
                            
                            CGFloat rectWidth = self.view.bounds.size.width * faceObservation.boundingBox.size.width;
                            CGFloat rectHeight = self.view.bounds.size.height * faceObservation.boundingBox.size.height;
                            
                            CGFloat boundingBoxY = self.view.bounds.size.height * (1 - faceObservation.boundingBox.origin.y - faceObservation.boundingBox.size.height);
                            
                            CGPoint p = CGPointZero;
                            if (position == AVCaptureDevicePositionFront){
                                
                                CGFloat boundingX = self.view.frame.size.width - faceObservation.boundingBox.origin.x * self.view.bounds.size.width - rectWidth;
                                
                                p = CGPointMake(point.x * rectWidth + boundingX, boundingBoxY + (1-point.y) * rectHeight);

}else{
                              p = CGPointMake(point.x * rectWidth + faceObservation.boundingBox.origin.x * self.view.bounds.size.width, boundingBoxY + (1-point.y) * rectHeight);
                            }

sPoints[i] = p;
                            
                            [pointXs addObject:[NSNumber numberWithFloat:p.x]];
                            [pointYs addObject:[NSNumber numberWithFloat:p.y]];
                        }
                        
                        for (int j = 0; j < rightEyefaceLandMarkRegion2D.pointCount; j ++) {
                            CGPoint point = rightEyefaceLandMarkRegion2D.normalizedPoints[j];

CGFloat rectWidth = self.view.bounds.size.width * faceObservation.boundingBox.size.width;
                            CGFloat rectHeight = self.view.bounds.size.height * faceObservation.boundingBox.size.height;

CGFloat boundingBoxY = self.view.bounds.size.height * (1 - faceObservation.boundingBox.origin.y - faceObservation.boundingBox.size.height);

CGPoint p = CGPointZero;
                            if (position == AVCaptureDevicePositionFront){
                                
                                CGFloat boundingX = self.view.frame.size.width - faceObservation.boundingBox.origin.x * self.view.bounds.size.width - rectWidth;
                                
                                p = CGPointMake(point.x * rectWidth + boundingX, boundingBoxY + (1-point.y) * rectHeight);
                                
                            }else{
                                p = CGPointMake(point.x * rectWidth + faceObservation.boundingBox.origin.x * self.view.bounds.size.width, boundingBoxY + (1-point.y) * rectHeight);
                            }
                            
                            sPoints[leftEyefaceLandMarkRegion2D.pointCount + j] = p;
                            
                            [pointXs addObject:[NSNumber numberWithFloat:p.x]];
                            [pointYs addObject:[NSNumber numberWithFloat:p.y]];
                        }
                        
//                        for (UIView *view in self.view.subviews) {
//                            if ([view isKindOfClass:[UIImageView class]]) {
//                                [view removeFromSuperview];
//                            }
//                        }
//
//                        for (int i = 0; i < rightEyefaceLandMarkRegion2D.pointCount + leftEyefaceLandMarkRegion2D.pointCount; i++) {
//                            CGFloat x = sPoints[i].x;
//                            CGFloat y = sPoints[i].y;
//                            UIImageView *view = [[UIImageView alloc] initWithFrame:CGRectMake(x, y, 2, 2)];
//                            view.backgroundColor = [UIColor redColor];
//                            [self.view addSubview:view];
//                        }
                        
                        //排序 得到最小的x和最大的x
                        NSArray *sortPointXs = [pointXs sortedArrayWithOptions:NSSortStable usingComparator:
                                                ^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
                                                    int value1 = [obj1 floatValue];
                                                    int value2 = [obj2 floatValue];
                                                    if (value1 > value2) {
                                                        return NSOrderedDescending;
                                                    }else if (value1 == value2){
                                                        return NSOrderedSame;
                                                    }else{
                                                        return NSOrderedAscending;
                                                    }
                                                }];

NSArray *sortPointYs = [pointYs sortedArrayWithOptions:NSSortStable usingComparator:
                                                ^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
                                                    int value1 = [obj1 floatValue];
                                                    int value2 = [obj2 floatValue];
                                                    if (value1 > value2) {
                                                        return NSOrderedDescending;
                                                    }else if (value1 == value2){
                                                        return NSOrderedSame;
                                                    }else{
                                                        return NSOrderedAscending;
                                                    }
                                                }];
                        
                        UIImage *image =[UIImage imageNamed:@"eyes"];
                        CGFloat imageWidth = [sortPointXs.lastObject floatValue] - [sortPointXs.firstObject floatValue] + 40;
                        CGFloat imageHeight = (imageWidth * image.size.height)/image.size.width;
                        
                        self.glassesImageView.frame = CGRectMake([sortPointXs.firstObject floatValue]-20, [sortPointYs.firstObject floatValue]-5, imageWidth, imageHeight);
                    });
                }
            }];
```
由于时间关系，代码有点乱，将就将就

先说说思路，我是想动态添加一个眼镜的，所以我必须先得到两个眼睛的位置，然后在计算出两个眼睛的宽高，最后适当的调整眼镜的大小，再动态的添加上去

这里必须要说的一个问题，就是我在实现过程中遇到的---`坐标`

首先是`y`坐标，如果还是按照静态图片的那种获取方式，那么得到的结果将会是完全相反的。
```
faceObservation.boundingBox.origin.y * image.size.height + point.y * rectHeight
```
这里我做了 一个假设，估计是由于摄像机成像的原因造成的，所以必须反其道而行，于是我如下改造了下
```
 CGFloat boundingBoxY = self.view.bounds.size.height * (1 - faceObservation.boundingBox.origin.y - faceObservation.boundingBox.size.height);

p = CGPointMake(point.x * rectWidth + faceObservation.boundingBox.origin.x * self.view.bounds.size.width, boundingBoxY + (1-point.y) * rectHeight);
```
从中可以看到，所有的`point.y`都用`1`减去了，这个试验的过程有点恼火，我还没怎么相通，若有知道的，希望可以告诉我下，当然我也会再研究研究。
再说完`y`坐标后，就是`x`坐标了，`x`坐标在`前置摄像头`的时候一切正常，然而在切换成`后置摄像头`的时候，又反了。心累啊，所以没办法，我就只要加判断，然后进行测试，有了如下代码
```
 CGFloat boundingX = self.view.frame.size.width - faceObservation.boundingBox.origin.x * self.view.bounds.size.width - rectWidth;
```
最后终于大功告成！
效果就是文章最顶的那个效果

#####项目文件截图如下
![](/contentImages/image/20171013/aM0ojPEagAyQAFOmZbO.jpg)
#####注意
1、在使用过程中，我发现当检测图片的时候内存和`cpu`的消耗还是很高的，比如我的`5s`就成功的崩溃过.....
2、图片方向是有要求的....
```
- (instancetype)initWithCVPixelBuffer:(CVPixelBufferRef)pixelBuffer options:(NSDictionary<VNImageOption, id> *)options;

/*!
 @brief initWithCVPixelBuffer:options creates a VNImageRequestHandler to be used for performing requests against the image passed in as buffer.
 
 @param pixelBuffer A CVPixelBuffer containing the image to be used for performing the requests. The content of the buffer cannot be modified for the lifetime of the VNImageRequestHandler.
 @param orientation The orientation of the image/buffer based on the EXIF specification. For details see kCGImagePropertyOrientation. The value has to be an integer from 1 to 8. This superceeds every other orientation information.
 @param options A dictionary with options specifying auxilary information for the buffer/image like VNImageOptionCameraIntrinsics
 */
- (instancetype)initWithCVPixelBuffer:(CVPixelBufferRef)pixelBuffer orientation:(CGImagePropertyOrientation)orientation options:(NSDictionary<VNImageOption, id> *)options;

```
通过对比上面两个函数，我们可以发现，多了一个`CGImagePropertyOrientation `类型的参数，没错，这就是指定传入图片的方向，如果指定了方向，而图片方向却不一致，那么恭喜你，检测不出来....这里我用的都是第一个方法，及没有参数，好像默认是`up`的。

iOS 11之Vision人脸检测

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