content: import java.awt.BorderLayout;
  import java.awt.Container;
  import java.awt.Image;
  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.Core.MinMaxLocResult;
  import org.opencv.core.CvType;
  import org.opencv.core.Mat;
  import org.opencv.core.Point;
  import org.opencv.core.Scalar;
  import org.opencv.highgui.HighGui;
  import org.opencv.imgcodecs.Imgcodecs;
  import org.opencv.imgproc.Imgproc;
  
  class CornerDetector {
      private Mat src = new Mat();
      private Mat srcGray = new Mat();
      private Mat harrisDst = new Mat();
      private Mat shiTomasiDst = new Mat();
      private Mat harrisCopy = new Mat();
      private Mat shiTomasiCopy = new Mat();
      private Mat Mc = new Mat();
      private JFrame frame;
      private JLabel harrisImgLabel;
      private JLabel shiTomasiImgLabel;
      private static final int MAX_QUALITY_LEVEL = 100;
      private int qualityLevel = 50;
      private double harrisMinVal;
      private double harrisMaxVal;
      private double shiTomasiMinVal;
      private double shiTomasiMaxVal;
      private Random rng = new Random(12345);
  
      public CornerDetector(String[] args) {
          /// Load source image and convert it to gray
          String filename = args.length > 0 ? args[0] : "../data/building.jpg";
          src = Imgcodecs.imread(filename);
          if (src.empty()) {
              System.err.println("Cannot read image: " + filename);
              System.exit(0);
          }
  
          Imgproc.cvtColor(src, srcGray, Imgproc.COLOR_BGR2GRAY);
  
          // Create and set up the window.
          frame = new JFrame("Creating your own corner detector demo");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          // Set up the content pane.
          Image img = HighGui.toBufferedImage(src);
          addComponentsToPane(frame.getContentPane(), img);
          // Use the content pane's default BorderLayout. No need for
          // setLayout(new BorderLayout());
          // Display the window.
          frame.pack();
          frame.setVisible(true);
  
          /// Set some parameters
          int blockSize = 3, apertureSize = 3;
  
          /// My Harris matrix -- Using cornerEigenValsAndVecs
          Imgproc.cornerEigenValsAndVecs(srcGray, harrisDst, blockSize, apertureSize);
  
          /* calculate Mc */
          Mc = Mat.zeros(srcGray.size(), CvType.CV_32F);
  
          float[] harrisData = new float[(int) (harrisDst.total() * harrisDst.channels())];
          harrisDst.get(0, 0, harrisData);
          float[] McData = new float[(int) (Mc.total() * Mc.channels())];
          Mc.get(0, 0, McData);
  
          for( int i = 0; i < srcGray.rows(); i++ ) {
              for( int j = 0; j < srcGray.cols(); j++ ) {
                  float lambda1 = harrisData[(i*srcGray.cols() + j) * 6];
                  float lambda2 = harrisData[(i*srcGray.cols() + j) * 6 + 1];
                  McData[i*srcGray.cols()+j] = (float) (lambda1*lambda2 - 0.04f*Math.pow( ( lambda1 + lambda2 ), 2 ));
              }
          }
          Mc.put(0, 0, McData);
  
          MinMaxLocResult res = Core.minMaxLoc(Mc);
          harrisMinVal = res.minVal;
          harrisMaxVal = res.maxVal;
  
          /// My Shi-Tomasi -- Using cornerMinEigenVal
          Imgproc.cornerMinEigenVal(srcGray, shiTomasiDst, blockSize, apertureSize);
          res = Core.minMaxLoc(shiTomasiDst);
          shiTomasiMinVal = res.minVal;
          shiTomasiMaxVal = res.maxVal;
  
          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));
  
          sliderPanel.add(new JLabel("Max  corners:"));
          JSlider slider = new JSlider(0, MAX_QUALITY_LEVEL, qualityLevel);
          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();
                  qualityLevel = source.getValue();
                  update();
              }
          });
          sliderPanel.add(slider);
          pane.add(sliderPanel, BorderLayout.PAGE_START);
  
          JPanel imgPanel = new JPanel();
          harrisImgLabel = new JLabel(new ImageIcon(img));
          shiTomasiImgLabel = new JLabel(new ImageIcon(img));
          imgPanel.add(harrisImgLabel);
          imgPanel.add(shiTomasiImgLabel);
          pane.add(imgPanel, BorderLayout.CENTER);
      }
  
      private void update() {
          int qualityLevelVal = Math.max(qualityLevel, 1);
  
          //Harris
          harrisCopy = src.clone();
  
          float[] McData = new float[(int) (Mc.total() * Mc.channels())];
          Mc.get(0, 0, McData);
          for (int i = 0; i < srcGray.rows(); i++) {
              for (int j = 0; j < srcGray.cols(); j++) {
                  if (McData[i * srcGray.cols() + j] > harrisMinVal
                          + (harrisMaxVal - harrisMinVal) * qualityLevelVal / MAX_QUALITY_LEVEL) {
                      Imgproc.circle(harrisCopy, new Point(j, i), 4,
                              new Scalar(rng.nextInt(256), rng.nextInt(256), rng.nextInt(256)), Imgproc.FILLED);
                  }
              }
          }
  
          //Shi-Tomasi
          shiTomasiCopy = src.clone();
  
          float[] shiTomasiData = new float[(int) (shiTomasiDst.total() * shiTomasiDst.channels())];
          shiTomasiDst.get(0, 0, shiTomasiData);
          for (int i = 0; i < srcGray.rows(); i++) {
              for (int j = 0; j < srcGray.cols(); j++) {
                  if (shiTomasiData[i * srcGray.cols() + j] > shiTomasiMinVal
                          + (shiTomasiMaxVal - shiTomasiMinVal) * qualityLevelVal / MAX_QUALITY_LEVEL) {
                      Imgproc.circle(shiTomasiCopy, new Point(j, i), 4,
                              new Scalar(rng.nextInt(256), rng.nextInt(256), rng.nextInt(256)), Imgproc.FILLED);
                  }
              }
          }
  
          harrisImgLabel.setIcon(new ImageIcon(HighGui.toBufferedImage(harrisCopy)));
          shiTomasiImgLabel.setIcon(new ImageIcon(HighGui.toBufferedImage(shiTomasiCopy)));
          frame.repaint();
      }
  }
  
  public class CornerDetectorDemo {
      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 CornerDetector(args);
              }
          });
      }
  }
  