import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Image;
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.Point;
import org.opencv.core.Scalar;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
class CornerHarris {
private Mat srcGray = new Mat();
private Mat dst = new Mat();
private Mat dstNorm = new Mat();
private Mat dstNormScaled = new Mat();
private JFrame frame;
private JLabel imgLabel;
private JLabel cornerLabel;
private static final int MAX_THRESHOLD = 255;
public CornerHarris(
String[] args) {
String filename = args.length > 0 ? args[0] :
"../data/building.jpg";
Mat src = Imgcodecs.imread(filename);
if (src.empty()) {
System.err.println("Cannot read image: " + filename);
System.exit(0);
}
Imgproc.cvtColor(src, srcGray, Imgproc.COLOR_BGR2GRAY);
frame = new JFrame("Harris corner detector demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Image img = HighGui.toBufferedImage(src);
addComponentsToPane(frame.getContentPane(), img);
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));
sliderPanel.add(new JLabel("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();
}
});
sliderPanel.add(slider);
pane.add(sliderPanel, BorderLayout.PAGE_START);
JPanel imgPanel = new JPanel();
imgLabel = new JLabel(new ImageIcon(img));
imgPanel.add(imgLabel);
Mat blackImg = Mat.zeros(srcGray.size(), CvType.CV_8U);
cornerLabel = new JLabel(new ImageIcon(HighGui.toBufferedImage(blackImg)));
imgPanel.add(cornerLabel);
pane.add(imgPanel, BorderLayout.CENTER);
}
private void update() {
dst = Mat.zeros(srcGray.size(), CvType.CV_32F);
int blockSize = 2;
int apertureSize = 3;
double k = 0.04;
Imgproc.cornerHarris(srcGray, dst, blockSize, apertureSize, k);
Core.normalize(dst, dstNorm, 0, 255, Core.NORM_MINMAX);
Core.convertScaleAbs(dstNorm, dstNormScaled);
float[] dstNormData = new float[(int) (dstNorm.total() * dstNorm.channels())];
dstNorm.get(0, 0, dstNormData);
for (int i = 0; i < dstNorm.rows(); i++) {
for (int j = 0; j < dstNorm.cols(); j++) {
if ((
int) dstNormData[i * dstNorm.cols() + j] >
threshold) {
Imgproc.circle(dstNormScaled,
new Point(j, i), 5,
new Scalar(0), 2, 8, 0);
}
}
}
cornerLabel.setIcon(new ImageIcon(HighGui.toBufferedImage(dstNormScaled)));
frame.repaint();
}
}
public class CornerHarrisDemo {
public static void main(
String[] args) {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
javax.swing.SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new CornerHarris(args);
}
});
}
}