content: import java.awt.BorderLayout;
  import java.awt.Container;
  import java.awt.Image;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Random;
  
  import javax.swing.BoxLayout;
  import javax.swing.ImageIcon;
  import javax.swing.JFrame;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  import javax.swing.JSlider;
  import javax.swing.event.ChangeEvent;
  import javax.swing.event.ChangeListener;
  
  import org.opencv.core.Core;
  import org.opencv.core.CvType;
  import org.opencv.core.Mat;
  import org.opencv.core.MatOfPoint;
  import org.opencv.core.MatOfPoint2f;
  import org.opencv.core.Point;
  import org.opencv.core.Scalar;
  import org.opencv.core.Size;
  import org.opencv.highgui.HighGui;
  import org.opencv.imgcodecs.Imgcodecs;
  import org.opencv.imgproc.Imgproc;
  import org.opencv.imgproc.Moments;
  
  class MomentsClass {
      private Mat srcGray = new Mat();
      private JFrame frame;
      private JLabel imgSrcLabel;
      private JLabel imgContoursLabel;
      private static final int MAX_THRESHOLD = 255;
      private int threshold = 100;
      private Random rng = new Random(12345);
  
      public MomentsClass(String[] args) {
          //! [setup]
          /// Load source image
          String filename = args.length > 0 ? args[0] : "../data/stuff.jpg";
          Mat src = Imgcodecs.imread(filename);
          if (src.empty()) {
              System.err.println("Cannot read image: " + filename);
              System.exit(0);
          }
  
          /// Convert image to gray and blur it
          Imgproc.cvtColor(src, srcGray, Imgproc.COLOR_BGR2GRAY);
          Imgproc.blur(srcGray, srcGray, new Size(3, 3));
          //! [setup]
  
          //! [createWindow]
          // Create and set up the window.
          frame = new JFrame("Image Moments demo");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          // Set up the content pane.
          Image img = HighGui.toBufferedImage(src);
          addComponentsToPane(frame.getContentPane(), img);
          //! [createWindow]
          // Use the content pane's default BorderLayout. No need for
          // setLayout(new BorderLayout());
          // Display the window.
          frame.pack();
          frame.setVisible(true);
          update();
      }
  
      private void addComponentsToPane(Container pane, Image img) {
          if (!(pane.getLayout() instanceof BorderLayout)) {
              pane.add(new JLabel("Container doesn't use BorderLayout!"));
              return;
          }
  
          JPanel sliderPanel = new JPanel();
          sliderPanel.setLayout(new BoxLayout(sliderPanel, BoxLayout.PAGE_AXIS));
  
          //! [trackbar]
          sliderPanel.add(new JLabel("Canny threshold: "));
          JSlider slider = new JSlider(0, MAX_THRESHOLD, threshold);
          slider.setMajorTickSpacing(20);
          slider.setMinorTickSpacing(10);
          slider.setPaintTicks(true);
          slider.setPaintLabels(true);
          slider.addChangeListener(new ChangeListener() {
              @Override
              public void stateChanged(ChangeEvent e) {
                  JSlider source = (JSlider) e.getSource();
                  threshold = source.getValue();
                  update();
              }
          });
          //! [trackbar]
          sliderPanel.add(slider);
          pane.add(sliderPanel, BorderLayout.PAGE_START);
  
          JPanel imgPanel = new JPanel();
          imgSrcLabel = new JLabel(new ImageIcon(img));
          imgPanel.add(imgSrcLabel);
  
          Mat blackImg = Mat.zeros(srcGray.size(), CvType.CV_8U);
          imgContoursLabel = new JLabel(new ImageIcon(HighGui.toBufferedImage(blackImg)));
          imgPanel.add(imgContoursLabel);
  
          pane.add(imgPanel, BorderLayout.CENTER);
      }
  
      private void update() {
          //! [Canny]
          /// Detect edges using Canny
          Mat cannyOutput = new Mat();
          Imgproc.Canny(srcGray, cannyOutput, threshold, threshold * 2);
          //! [Canny]
  
          //! [findContours]
          /// Find contours
          List<MatOfPoint> contours = new ArrayList<>();
          Mat hierarchy = new Mat();
          Imgproc.findContours(cannyOutput, contours, hierarchy, Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_SIMPLE);
          //! [findContours]
  
          /// Get the moments
          List<Moments> mu = new ArrayList<>(contours.size());
          for (int i = 0; i < contours.size(); i++) {
              mu.add(Imgproc.moments(contours.get(i)));
          }
  
          /// Get the mass centers
          List<Point> mc = new ArrayList<>(contours.size());
          for (int i = 0; i < contours.size(); i++) {
              //add 1e-5 to avoid division by zero
              mc.add(new Point(mu.get(i).m10 / (mu.get(i).m00 + 1e-5), mu.get(i).m01 / (mu.get(i).m00 + 1e-5)));
          }
  
          //! [zeroMat]
          /// Draw contours
          Mat drawing = Mat.zeros(cannyOutput.size(), CvType.CV_8UC3);
          //! [zeroMat]
          //! [forContour]
          for (int i = 0; i < contours.size(); i++) {
              Scalar color = new Scalar(rng.nextInt(256), rng.nextInt(256), rng.nextInt(256));
              Imgproc.drawContours(drawing, contours, i, color, 2);
              Imgproc.circle(drawing, mc.get(i), 4, color, -1);
          }
          //! [forContour]
  
          //! [showDrawings]
          /// Show in a window
          imgContoursLabel.setIcon(new ImageIcon(HighGui.toBufferedImage(drawing)));
          frame.repaint();
          //! [showDrawings]
  
          /// Calculate the area with the moments 00 and compare with the result of the OpenCV function
          System.out.println("\t Info: Area and Contour Length \n");
          for (int i = 0; i < contours.size(); i++) {
              System.out.format(" * Contour[%d] - Area (M_00) = %.2f - Area OpenCV: %.2f - Length: %.2f\n", i,
                      mu.get(i).m00, Imgproc.contourArea(contours.get(i)),
                      Imgproc.arcLength(new MatOfPoint2f(contours.get(i).toArray()), true));
          }
      }
  }
  
  public class MomentsDemo {
      public static void main(String[] args) {
          // Load the native OpenCV library
          System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
  
          // Schedule a job for the event dispatch thread:
          // creating and showing this application's GUI.
          javax.swing.SwingUtilities.invokeLater(new Runnable() {
              @Override
              public void run() {
                  new MomentsClass(args);
              }
          });
      }
  }
  