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OpenCV Java Highgui Class
The objective is to: *Reduce greatly the number of lines of code in the Java codes; *Make it easy for Java users to add a trackbar and show the results; *Get the code more similar between C++, Java and Python, making the tutorials more uniform.
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‎modules/highgui/CMakeLists.txt

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set(the_description "High-level GUI")
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ocv_add_module(highgui opencv_imgproc opencv_imgcodecs OPTIONAL opencv_videoio WRAP python)
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if(ANDROID)
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ocv_add_module(highgui opencv_imgproc opencv_imgcodecs OPTIONAL opencv_videoio WRAP python)
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else()
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ocv_add_module(highgui opencv_imgproc opencv_imgcodecs OPTIONAL opencv_videoio WRAP python java)
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endif()
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# ----------------------------------------------------------------------------
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# CMake file for highgui. See root CMakeLists.txt

‎modules/highgui/misc/java/src/java/highgui+HighGui.java

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package org.opencv.highgui;
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import org.opencv.core.Mat;
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import javax.swing.*;
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import java.awt.*;
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import java.awt.event.KeyEvent;
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import java.awt.event.KeyListener;
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import java.awt.image.BufferedImage;
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import java.awt.image.DataBufferByte;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.Map;
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import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.TimeUnit;
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/**
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* This class was designed for use in Java applications
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* to recreate the OpenCV HighGui functionalities.
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*/
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public final class HighGui {
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// Constants for namedWindow
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public final static int WINDOW_NORMAL = ImageWindow.WINDOW_NORMAL;
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public final static int WINDOW_AUTOSIZE = ImageWindow.WINDOW_AUTOSIZE;
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// Control Variables
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public static int n_closed_windows = 0;
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public static int pressedKey = -1;
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public static CountDownLatch latch = new CountDownLatch(1);
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// Windows Map
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public static Map<String, ImageWindow> windows = new HashMap<String, ImageWindow>();
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public static void namedWindow(String winname) {
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namedWindow(winname, HighGui.WINDOW_AUTOSIZE);
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}
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public static void namedWindow(String winname, int flag) {
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ImageWindow newWin = new ImageWindow(winname, flag);
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if (windows.get(winname) == null) windows.put(winname, newWin);
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}
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public static void imshow(String winname, Mat img) {
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if (img.empty()) {
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System.err.println("Error: Empty image in imshow");
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System.exit(-1);
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} else {
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ImageWindow tmpWindow = windows.get(winname);
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if (tmpWindow == null) {
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ImageWindow newWin = new ImageWindow(winname, img);
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windows.put(winname, newWin);
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} else {
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tmpWindow.setMat(img);
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}
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}
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}
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public static Image toBufferedImage(Mat m) {
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int type = BufferedImage.TYPE_BYTE_GRAY;
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if (m.channels() > 1) {
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type = BufferedImage.TYPE_3BYTE_BGR;
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}
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int bufferSize = m.channels() * m.cols() * m.rows();
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byte[] b = new byte[bufferSize];
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m.get(0, 0, b); // get all the pixels
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BufferedImage image = new BufferedImage(m.cols(), m.rows(), type);
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final byte[] targetPixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
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System.arraycopy(b, 0, targetPixels, 0, b.length);
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return image;
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}
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public static JFrame createJFrame(String title, int flag) {
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JFrame frame = new JFrame(title);
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frame.addWindowListener(new java.awt.event.WindowAdapter() {
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@Override
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public void windowClosing(java.awt.event.WindowEvent windowEvent) {
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n_closed_windows++;
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if (n_closed_windows == windows.size()) latch.countDown();
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}
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});
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frame.addKeyListener(new KeyListener() {
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@Override
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public void keyTyped(KeyEvent e) {
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}
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@Override
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public void keyReleased(KeyEvent e) {
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}
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@Override
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public void keyPressed(KeyEvent e) {
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pressedKey = e.getKeyCode();
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latch.countDown();
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}
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});
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if (flag == WINDOW_AUTOSIZE) frame.setResizable(false);
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return frame;
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}
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public static void waitKey(){
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waitKey(0);
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}
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public static int waitKey(int delay) {
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// Reset control values
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latch = new CountDownLatch(1);
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n_closed_windows = 0;
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pressedKey = -1;
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// If there are no windows to be shown return
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if (windows.isEmpty()) {
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System.err.println("Error: waitKey must be used after an imshow");
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System.exit(-1);
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}
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// Remove the unused windows
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Iterator<Map.Entry<String,
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ImageWindow>> iter = windows.entrySet().iterator();
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while (iter.hasNext()) {
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Map.Entry<String,
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ImageWindow> entry = iter.next();
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ImageWindow win = entry.getValue();
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if (win.alreadyUsed) {
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iter.remove();
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win.frame.dispose();
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}
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}
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// (if) Create (else) Update frame
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for (ImageWindow win : windows.values()) {
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if (win.img != null) {
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ImageIcon icon = new ImageIcon(toBufferedImage(win.img));
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if (win.lbl == null) {
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JFrame frame = createJFrame(win.name, win.flag);
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JLabel lbl = new JLabel(icon);
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win.setFrameLabelVisible(frame, lbl);
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} else {
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win.lbl.setIcon(icon);
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}
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} else {
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System.err.println("Error: no imshow associated with" + " namedWindow: \"" + win.name + "\"");
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System.exit(-1);
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}
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}
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try {
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if (delay == 0) {
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latch.await();
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} else {
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latch.await(delay, TimeUnit.MILLISECONDS);
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}
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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// Set all windows as already used
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for (ImageWindow win : windows.values())
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win.alreadyUsed = true;
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return pressedKey;
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}
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public static void destroyWindow(String winname) {
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ImageWindow tmpWin = windows.get(winname);
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if (tmpWin != null) windows.remove(winname);
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}
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public static void destroyAllWindows() {
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windows.clear();
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}
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public static void resizeWindow(String winname, int width, int height) {
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ImageWindow tmpWin = windows.get(winname);
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if (tmpWin != null) tmpWin.setNewDimension(width, height);
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}
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public static void moveWindow(String winname, int x, int y) {
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ImageWindow tmpWin = windows.get(winname);
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if (tmpWin != null) tmpWin.setNewPosition(x, y);
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}
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}

‎modules/highgui/misc/java/src/java/highgui+ImageWindow.java

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package org.opencv.highgui;
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import org.opencv.core.Mat;
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import org.opencv.core.Size;
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import org.opencv.imgproc.Imgproc;
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import javax.swing.*;
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import java.awt.*;
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/**
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* This class was designed to create and manipulate
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* the Windows to be used by the HighGui class.
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*/
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public final class ImageWindow {
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public final static int WINDOW_NORMAL = 0;
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public final static int WINDOW_AUTOSIZE = 1;
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public String name;
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public Mat img = null;
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public Boolean alreadyUsed = false;
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public Boolean imgToBeResized = false;
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public Boolean windowToBeResized = false;
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public Boolean positionToBeChanged = false;
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public JFrame frame = null;
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public JLabel lbl = null;
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public int flag;
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public int x = -1;
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public int y = -1;
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public int width = -1;
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public int height = -1;
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public ImageWindow(String name, Mat img) {
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this.name = name;
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this.img = img;
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this.flag = WINDOW_NORMAL;
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}
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public ImageWindow(String name, int flag) {
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this.name = name;
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this.flag = flag;
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}
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public static Size keepAspectRatioSize(int original_width, int original_height, int bound_width, int bound_height) {
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int new_width = original_width;
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int new_height = original_height;
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if (original_width > bound_width) {
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new_width = bound_width;
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new_height = (new_width * original_height) / original_width;
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}
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if (new_height > bound_height) {
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new_height = bound_height;
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new_width = (new_height * original_width) / original_height;
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}
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return new Size(new_width, new_height);
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}
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public void setMat(Mat img) {
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this.img = img;
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this.alreadyUsed = false;
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if (imgToBeResized) {
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resizeImage();
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imgToBeResized = false;
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}
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}
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public void setFrameLabelVisible(JFrame frame, JLabel lbl) {
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this.frame = frame;
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this.lbl = lbl;
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if (windowToBeResized) {
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lbl.setPreferredSize(new Dimension(width, height));
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windowToBeResized = false;
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}
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if (positionToBeChanged) {
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frame.setLocation(x, y);
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positionToBeChanged = false;
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}
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frame.add(lbl);
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frame.pack();
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frame.setVisible(true);
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}
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public void setNewDimension(int width, int height) {
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if (this.width != width || this.height != height) {
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this.width = width;
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this.height = height;
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if (img != null) {
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resizeImage();
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} else {
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imgToBeResized = true;
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}
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if (lbl != null) {
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lbl.setPreferredSize(new Dimension(width, height));
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} else {
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windowToBeResized = true;
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}
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}
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}
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public void setNewPosition(int x, int y) {
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if (this.x != x || this.y != y) {
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this.x = x;
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this.y = y;
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if (frame != null) {
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frame.setLocation(x, y);
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} else {
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positionToBeChanged = true;
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}
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}
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}
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private void resizeImage() {
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if (flag == WINDOW_NORMAL) {
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Size tmpSize = keepAspectRatioSize(img.width(), img.height(), width, height);
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Imgproc.resize(img, img, tmpSize);
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}
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}
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}

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