Basic Opencv Face Detection Tutorial

#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/objdetect.hpp>
#include <opencv2/imgproc.hpp>
#include <iostream>

using namespace cv;
using namespace std;


int main(int argc, char** argv)
{
 // capture from web camera init

 VideoCapture cap(0);
 cap.open(0);

 Mat img;

// Load cascate classifier placed in sulution folder
 CascadeClassifier detector;
 string cascadeName = "haarcascade_frontalface_alt.xml";
 bool loaded = detector.load(cascadeName);
// Parameters of detectMultiscale Cascade Classifier
 int groundThreshold = 2;
 double scaleStep = 1.1;
 Size minimalObjectSize(80, 80);
 Size maximalObjectSize(200, 200);

// Vector of returned faces
 vector found;

 for (;;)
 {
 
      // Image from camera to Mat

      cap >> img;
     // Convert input to greyscale 
      Mat image_grey;
      cvtColor(img, image_grey, CV_BGR2GRAY);

      // why not
      found.clear();
  
      // Detect faces
      detector.detectMultiScale(image_greyHead, found, scaleStep, groundThreshold, 0         | 2, minimalObjectSize,maximalObjectSize);
      // Draw the results into mat retrieved from webcam
      if (found.size() > 0) {
            for (int i = 0; i <= found.size() - 1; i++) {
             rectangle(img, found[i].br(), found[i].tl(), Scalar(0, 0, 0), 1, 8, 0);
             }
      }

    //Show the results

     imshow("wooohooo", img);
     int key2 = waitKey(20);

 }
 return 0;
}