int main(int, char**) { VideoCapture cap(0); // open the default camera if(!cap.isOpened()) return -1; // check if we succeeded Mat frame; namedWindow("tracking",1); while(true) { cap >> frame; tracker.track(frame); for(auto face_center : tracker.faces_centers){ ellipse( frame, face_center, Size( 5, 5), 0, 0, 360, Scalar( 255, 255, 0 ), 4, 8, 0 ); // could be boxe-rectangle ~ size of face } imshow("tracking", frame); if(waitKey(30) >= 0) break; } return 0; }