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In kalman filter, how to count detected object in sequence and is there any easiest way to ignore nearest object. MOG will provide good BG subtraction but it will work only for object near to cam.

using namespace std;
using namespace cv;

 #define drawCross( img, center, color, d )\
 line(img, Point(center.x - d, center.y - d), Point(center.x + d, center.y + d), color, 2, CV_AA, 0);\
 line(img, Point(center.x + d, center.y - d), Point(center.x - d, center.y + d), color, 2, CV_AA, 0 )\

int main()
{
Mat frame, thresh_frame,src_gray;
vector<Mat> channels;
VideoCapture capture;
vector<Vec4i> hierarchy;
vector<vector<Point> > contours;
  char text[255];
  int num = 0;
  BackgroundSubtractorMOG2 mog;
  capture.open("vid.avi");

  if(!capture.isOpened())
  cerr << "Problem opening video source" << endl;

   KalmanFilter KF(4, 2, 0);
   Mat_<float> state(4, 1);
   Mat_<float> processNoise(4, 1, CV_32F);
   Mat_<float> measurement(2,1); measurement.setTo(Scalar(0));

   KF.statePre.at<float>(0) = 0;
   KF.statePre.at<float>(1) = 0;
   KF.statePre.at<float>(2) = 0;
   KF.statePre.at<float>(3) = 0;

   KF.transitionMatrix = *(Mat_<float>(4, 4) << 1,0,1,0,   0,1,0,1,  0,0,1,0,  0,0,0,1); //  Including velocity
   KF.processNoiseCov = *(cv::Mat_<float>(4,4) << 0.2,0,0.2,0,  0,0.2,0,0.2,  0,0,0.3,0,  0,0,0,0.3);

   setIdentity(KF.measurementMatrix);
   setIdentity(KF.processNoiseCov, Scalar::all(1e-4));
   setIdentity(KF.measurementNoiseCov, Scalar::all(1e-1));
   setIdentity(KF.errorCovPost, Scalar::all(.1));

   while((char)waitKey(100) != 'q' && capture.grab())
   {
    capture.retrieve(frame);
    mog(frame,src_gray,-1);

    threshold( src_gray, thresh_frame, 128, 255, THRESH_BINARY );
    medianBlur(thresh_frame,thresh_frame,9);
    erode(thresh_frame,thresh_frame,Mat());
    dilate(thresh_frame,thresh_frame,Mat());
    imshow("MOG", thresh_frame);
    findContours( thresh_frame, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

     Mat drawing = Mat::zeros(thresh_frame.size(), CV_8UC1);
     for(size_t i = 0; i < contours.size(); i++)
     {
     // cout << contourArea(contours[i]) << endl;
      if(contourArea(contours[i]) > 500)
        drawContours(drawing, contours, i, Scalar::all(255), CV_FILLED, 8, vector<Vec4i>(), 0, Point());

    }
  thresh_frame = drawing;

  vector<Moments> mu(contours.size() );
  for( size_t i = 0; i < contours.size(); i++ )
    { mu[i] = moments( contours[i], false ); }

  //  Get the mass centers:
  vector<Point2f> mc( contours.size() );
  for( size_t i = 0; i < contours.size(); i++ )
    { mc[i] = Point2f( mu[i].m10/mu[i].m00 , mu[i].m01/mu[i].m00 ); }

  Mat prediction = KF.predict();
  Point predictPt(prediction.at<float>(0),prediction.at<float>(1));

  for(size_t i = 0; i < mc.size(); i++)
    {
       cout << "\n" << mc.size();
       sprintf(text, "%d", num);
       putText(frame, text, mc[i],FONT_HERSHEY_COMPLEX_SMALL, 0.8, cvScalar(0,255,255), 1, CV_AA);
      measurement(0) = mc[i].x;
      measurement(1) = mc[i].y;
    }

  Point measPt(measurement(0),measurement(1));

  Mat estimated = KF.correct(measurement);
  Point statePt(estimated.at<float>(0),estimated.at<float>(1));

  drawCross(frame, statePt, Scalar(255, 255, 255), 5);

  KF.statePre.copyTo(KF.statePost);

  vector<vector<Point> > contours_poly( contours.size() );
  vector<Rect> boundRect( contours.size() );
  for( size_t i = 0; i < contours.size(); i++ )
   { approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true );
     boundRect[i] = boundingRect( Mat(contours_poly[i]) );
   }

  for( size_t i = 0; i < contours.size(); i++ )
   {
     rectangle( frame, boundRect[i].tl(), boundRect[i].br(), Scalar(0, 255, 0), 2, 8, 0 );
   }

  num++;
  imshow("Video", frame);
}
return 0;
}