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));

}

}

static {

try {

// Load the native OpenCV library

NativeLoader.loadLibrary(Core.NATIVE_LIBRARY_NAME);

} catch (Exception e) {

}

}

public static void main(String[] args) {

// 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);

}

});

}