content: import org.opencv.core.Core;
  import org.opencv.core.Mat;
  import org.opencv.core.Point;
  import org.opencv.core.Scalar;
  import org.opencv.highgui.HighGui;
  import org.opencv.imgproc.Imgproc;
  import org.opencv.video.BackgroundSubtractor;
  import org.opencv.video.Video;
  import org.opencv.videoio.VideoCapture;
  import org.opencv.videoio.Videoio;
  
  class BackgroundSubtraction {
      public void run(String[] args) {
          String input = args.length > 0 ? args[0] : "../data/vtest.avi";
          boolean useMOG2 = args.length > 1 ? args[1] == "MOG2" : true;
  
          //! [create]
          BackgroundSubtractor backSub;
          if (useMOG2) {
              backSub = Video.createBackgroundSubtractorMOG2();
          } else {
              backSub = Video.createBackgroundSubtractorKNN();
          }
          //! [create]
  
          //! [capture]
          VideoCapture capture = new VideoCapture(input);
          if (!capture.isOpened()) {
              System.err.println("Unable to open: " + input);
              System.exit(0);
          }
          //! [capture]
  
          Mat frame = new Mat(), fgMask = new Mat();
          while (true) {
              capture.read(frame);
              if (frame.empty()) {
                  break;
              }
  
              //! [apply]
              // update the background model
              backSub.apply(frame, fgMask);
              //! [apply]
  
              //! [display_frame_number]
              // get the frame number and write it on the current frame
              Imgproc.rectangle(frame, new Point(10, 2), new Point(100, 20), new Scalar(255, 255, 255), -1);
              String frameNumberString = String.format("%d", (int)capture.get(Videoio.CAP_PROP_POS_FRAMES));
              Imgproc.putText(frame, frameNumberString, new Point(15, 15), Core.FONT_HERSHEY_SIMPLEX, 0.5,
                      new Scalar(0, 0, 0));
              //! [display_frame_number]
  
              //! [show]
              // show the current frame and the fg masks
              HighGui.imshow("Frame", frame);
              HighGui.imshow("FG Mask", fgMask);
              //! [show]
  
              // get the input from the keyboard
              int keyboard = HighGui.waitKey(30);
              if (keyboard == 'q' || keyboard == 27) {
                  break;
              }
          }
  
          HighGui.waitKey();
          System.exit(0);
      }
  }
  
  public class BackgroundSubtractionDemo {
      public static void main(String[] args) {
          // Load the native OpenCV library
          System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
  
          new BackgroundSubtraction().run(args);
      }
  }
  