1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
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);
}
});
}
}