OpenCV face recognition example

frontal_face_recognition.cpp

#include <vector>
#include <opencv2/core.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/objdetect.hpp>
#include <iostream>
#include <vector>
using namespace cv;
using namespace std;
int main(int, char**)
{
  CascadeClassifier bodyCascade = CascadeClassifier("/usr/local/share/opencv4/haarcascades/haarcascade_frontalface_default.xml");
  Mat frame, frameGray;
  VideoCapture cap;
  int deviceID = 0;
  int apiID = cv::CAP_ANY; 
  cap.open(deviceID, apiID);
  if (!cap.isOpened()) {
      cerr << "ERROR! Unable to open camera\n";
      return -1;
  }
  cout << "Start grabbing" << endl
      << "Press any key to terminate" << endl;
  for (;;)
  {
    cap.read(frame);
    if (frame.empty()) {
      cerr << "ERROR! blank frame grabbed\n";
      break;
    }
    cvtColor(frame, frameGray, COLOR_BGR2GRAY);
    vector<Rect> bodies;
    bodyCascade.detectMultiScale(frameGray, bodies, 1.1, 3, CASCADE_FIND_BIGGEST_OBJECT, Size(30, 30), Size(200,200));
    for (int i = 0; i < bodies.size(); i++) {
      Rect r = bodies[i];
      rectangle(frame,  {r.x, r.y}, {r.x + r.width, r.y + r.height}, {0, 255, 0}, LINE_4);
    }
    cout << bodies.size() << endl;
    imshow("Live", frame);
    if (waitKey(5) >= 0) {
      break;
    }
  }
  return 0;
}