text: #include "opencv2/optflow.hpp"
  #include "opencv2/imgproc.hpp"
  #include "opencv2/videoio.hpp"
  #include "opencv2/highgui.hpp"
  #include <time.h>
  #include <stdio.h>
  #include <ctype.h>
  
  using namespace cv;
  using namespace std;
  using namespace cv::motempl;
  
  static void help(void)
  {
      printf(
          "\nThis program demonstrated the use of motion templates -- basically using the gradients\n"
          "of thresholded layers of decaying frame differencing. New movements are stamped on top with floating system\n"
          "time code and motions too old are thresholded away. This is the 'motion history file'. The program reads from the camera of your choice or from\n"
          "a file. Gradients of motion history are used to detect direction of motion etc\n"
          "Usage :\n"
          "./motempl [camera number 0-n or file name, default is camera 0]\n"
          );
  }
  // various tracking parameters (in seconds)
  const double MHI_DURATION = 5;
  const double MAX_TIME_DELTA = 0.5;
  const double MIN_TIME_DELTA = 0.05;
  // number of cyclic frame buffer used for motion detection
  // (should, probably, depend on FPS)
  
  // ring image buffer
  vector<Mat> buf;
  int last = 0;
  
  // temporary images
  Mat mhi, orient, mask, segmask, zplane;
  vector<Rect> regions;
  
  // parameters:
  //  img - input video frame
  //  dst - resultant motion picture
  //  args - optional parameters
  static void  update_mhi(const Mat& img, Mat& dst, int diff_threshold)
  {
      double timestamp = (double)clock() / CLOCKS_PER_SEC; // get current time in seconds
      Size size = img.size();
      int i, idx1 = last;
      Rect comp_rect;
      double count;
      double angle;
      Point center;
      double magnitude;
      Scalar color;
  
      // allocate images at the beginning or
      // reallocate them if the frame size is changed
      if (mhi.size() != size)
      {
          mhi = Mat::zeros(size, CV_32F);
          zplane = Mat::zeros(size, CV_8U);
  
          buf[0] = Mat::zeros(size, CV_8U);
          buf[1] = Mat::zeros(size, CV_8U);
      }
  
      cvtColor(img, buf[last], COLOR_BGR2GRAY); // convert frame to grayscale
  
      int idx2 = (last + 1) % 2; // index of (last - (N-1))th frame
      last = idx2;
  
      Mat silh = buf[idx2];
      absdiff(buf[idx1], buf[idx2], silh); // get difference between frames
  
      threshold(silh, silh, diff_threshold, 1, THRESH_BINARY); // and threshold it
      updateMotionHistory(silh, mhi, timestamp, MHI_DURATION); // update MHI
  
      // convert MHI to blue 8u image
      mhi.convertTo(mask, CV_8U, 255. / MHI_DURATION, (MHI_DURATION - timestamp)*255. / MHI_DURATION);
  
      Mat planes[] = { mask, zplane, zplane };
      merge(planes, 3, dst);
  
      // calculate motion gradient orientation and valid orientation mask
      calcMotionGradient(mhi, mask, orient, MAX_TIME_DELTA, MIN_TIME_DELTA, 3);
  
      // segment motion: get sequence of motion components
      // segmask is marked motion components map. It is not used further
      regions.clear();
      segmentMotion(mhi, segmask, regions, timestamp, MAX_TIME_DELTA);
  
      // iterate through the motion components,
      // One more iteration (i == -1) corresponds to the whole image (global motion)
      for (i = -1; i < (int)regions.size(); i++) {
  
          if (i < 0) { // case of the whole image
              comp_rect = Rect(0, 0, size.width, size.height);
              color = Scalar(255, 255, 255);
              magnitude = 100;
          }
          else { // i-th motion component
              comp_rect = regions[i];
              if (comp_rect.width + comp_rect.height < 100) // reject very small components
                  continue;
              color = Scalar(0, 0, 255);
              magnitude = 30;
          }
  
          // select component ROI
          Mat silh_roi = silh(comp_rect);
          Mat mhi_roi = mhi(comp_rect);
          Mat orient_roi = orient(comp_rect);
          Mat mask_roi = mask(comp_rect);
  
          // calculate orientation
          angle = calcGlobalOrientation(orient_roi, mask_roi, mhi_roi, timestamp, MHI_DURATION);
          angle = 360.0 - angle;  // adjust for images with top-left origin
  
          count = norm(silh_roi, NORM_L1);; // calculate number of points within silhouette ROI
  
          // check for the case of little motion
          if (count < comp_rect.width*comp_rect.height * 0.05)
              continue;
  
          // draw a clock with arrow indicating the direction
          center = Point((comp_rect.x + comp_rect.width / 2),
              (comp_rect.y + comp_rect.height / 2));
  
          circle(img, center, cvRound(magnitude*1.2), color, 3, 16, 0);
          line(img, center, Point(cvRound(center.x + magnitude*cos(angle*CV_PI / 180)),
              cvRound(center.y - magnitude*sin(angle*CV_PI / 180))), color, 3, 16, 0);
      }
  }
  
  
  int main(int argc, char** argv)
  {
      VideoCapture cap;
  
      help();
  
      if (argc == 1 || (argc == 2 && strlen(argv[1]) == 1 && isdigit(argv[1][0])))
          cap.open(argc == 2 ? argv[1][0] - '0' : 0);
      else if (argc == 2)
          cap.open(argv[1]);
  
      if (!cap.isOpened())
      {
          printf("Could not initialize video capture\n");
          return 0;
      }
      buf.resize(2);
      Mat image, motion;
      for (;;)
      {
          cap >> image;
          if (image.empty())
              break;
  
          update_mhi(image, motion, 30);
          imshow("Image", image);
          imshow("Motion", motion);
  
          if (waitKey(10) >= 0)
              break;
      }
  
      return 0;
  }
  