Please download the haarcascade_frontalface_default.xml into the data folder. In addition to the Haar Cascades file, we also need the face landmark definition. If we build the OpenCV with the Face module, it will download automatically. Otherwise, we can also download from face_landmark_model.dat.
The folder also contains the 2 photos, daniel.jpg and george.jpg for testing.
The CVImage library is also required for this sketch. It can be installed properly as a Processing library or temporarily in the code folder.