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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);
}
});
}
}
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