Let's define faces and a face detector in pure C++ code without using any dependencies except OpenCV. This ensures that the computer vision functionality of ManyMasks is portable. We could reuse the core of our code on a different platform with a different set of UI libraries.

A face has a species. For our purposes, this could be Human, Cat, or Hybrid. Let's create a header file, Species.h, and define the following enum in it:

#ifndef SPECIES_H
#define SPECIES_H

enum Species {
  Human,
  Cat,
  Hybrid
};

#endif // !SPECIES_H

A face also has a matrix of image data and three feature points representing the centers of the eyes and tip of the nose. We may construct a face in any of the following ways:

Let's create another header file, Face.h, and declare the following public interface of a Face class...