The class has four public member variables: the path to an object of type cv::CascadeClassifier called detector_fname, a set of offsets from a detection bounding box to the location and scale of the face in the image detector_offset, a reference shape to place in the bounding box reference, and a face detector detector. The primary function of use to a face tracking system is face_detector::detect, which takes an image as the input, along with standard options for the cv::CascadeClassifier class, and returns a rough estimate of the facial feature locations in the image. Its implementation is as follows: