MMFaceDetector 接口文档

人脸检测器，检测图片获取人脸区域，关键点信息。可用于美颜，图片人脸检测等。

1. 构造方法

同步构造方法

  MMFaceDetector *facedetector = [[MCCDetectorsCenter sharedInstance] syncMakeFaceDetector:MCCFaceDetectorTypeFace];

异步构造方法

  [[MCCDetectorsCenter sharedInstance] asyncMakeFaceDetector:MCCFaceDetectorTypeFace complete:^(NSObject * _Nullable detector) {
      MMFaceDetector *facedetector = detector;
  }];

是否开启表情检测，默认是NO

@property (nonatomic) BOOL advancedExpressionDetectionEnabled;

2. 检测方法

共提供三个检测接口，MMFaceDetectOptions 字段为扫脸传参，MMFaceFeature 为单人脸信息（多人时，数组会有多值）。

- (NSArray<MMFaceFeature *> *)featuresInPixelBuffer:(CVPixelBufferRef)pixelBuffer;

- (NSArray<MMFaceFeature *> *)featuresInPixelBuffer:(CVPixelBufferRef)pixelBuffer orientation:(MMCVImageOrientation)orientation;

- (NSArray<MMFaceFeature *> *)featuresInPixelBuffer:(CVPixelBufferRef)pixelBuffer options:(MMFaceDetectOptions *)options;

3. MMFaceDetectOptions 字段介绍

图片帧类型，是否静态图

@property (nonatomic) MMFaceDetectionInputHint inputHint;

图片方向

@property (nonatomic) MMCVImageOrientation orientation;

检测算法（视频推荐MMFaceDetectionMethodNPD，能耗降低）
```
@property (nonatomic) MMFaceDetectionMethod faceDetectionMethod;
```

最大检测脸个数

@property (nonatomic) NSUInteger maximumFaceCount;

人脸点数版本（fd模型支持96，fd137支持96&137）

@property (nonatomic) MMFaceAlignmentVersion faceAlignmentVersion;

4. MMFaceFeature 字段介绍

trackId 人脸追踪标识，视频人脸追踪中不变，人脸丢失后自增
```
@property (nonatomic,readonly) NSInteger trackingIdentifier;
```
人脸五官矩形区域（相对于图形帧）
```
@property (nonatomic,readonly) CGRect bounds;
```

人脸欧拉角

@property (nonatomic,readonly) double pitch;
@property (nonatomic,readonly) double yaw;
@property (nonatomic,readonly) double roll;

图片大小

@property (nonatomic,readonly) CGSize imageSize;

4.1. MMFaceLandmarks2D 介绍

MMFaceLandmarks2D 可以通过 MMFaceFeature 调用如下接口获得

typedef NS_ENUM(NSInteger, MMFaceLandmarks2DType) {
    MMFaceLandmarks2DType68,
    MMFaceLandmarks2DType96,
    MMFaceLandmarks2DType104,
    MMFaceLandmarks2DType137
};
- (MMFaceLandmarks2D *)landmarksOfType:(MMFaceLandmarks2DType)type NS_SWIFT_NAME(landmarks(ofType:));

脸部关键点的个数

@property (readonly) NSUInteger pointCount;

脸部关键点(相对视频帧坐标)

@property (nonatomic, readonly) const simd_float2 *points NS_RETURNS_INNER_POINTER;
@property (nonatomic, copy, readonly) NSArray<NSValue *> *pointValues;

脸部关键点(归一化后坐标)

@property (nonatomic, readonly) const simd_float2 *normalizedPoints NS_RETURNS_INNER_POINTER;