OpenCV Java imshow()的实现

喜欢用OpenCV和Java的人往往会使用官网提供的OpenCV的包，OpenCV除了用于图像处理，本身也是一个优秀的数学库。而且对于Java而言，配置方便，编写容易，可扩展性也强。Java效率虽然低，但是核心计算部分仍然是C写的。

然而对于初学者来说，一个非常重要的函数——

imshow(Mat m, string window)

在Java中被阉割掉了，这使我们观察图像输出时只能通过

imwrite()

保存为图片后再查看，用起来非常不爽。因此，我动手自己实现了一个java类，实现了该函数以及

waitKey(int time)

两个函数，主要使用了java的swing框架，以及obj的wait()和notify()函数实现

waitKey(int time)

。其中，

函数名	参数	功能
ImageGui(Mat m, String window)	要显示的图像和窗口名	构造
ig.imshow()	无	显示图片
ig.waitKey(int time);	需要暂停的毫秒数	参数为0则阻塞线程且等待用户输入，不为0则等待指定毫秒数后继续运行，并返回键盘输入值

实现效果如下。



是不是和C++中的imshow()一样好用呢？

下面是源码。

1. ImageGui.java

package com.meng.highgui;

import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;

import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.python.modules.synchronize;
/**
* An Gui extention for opencv3.0 using Swing, which can't display images in java.
* @author Dechao
*
* Description:
*
* examples:
*  System.loadLibrary("opencv_java300");
*  Mat mat = Mat.eye(1000, 2000, CvType.CV_8UC3);
*  String window_name = "mat"
*  ImageGui ig = new ImageGui(mat,window_name);
*  ig.imshow();
*  ig.waitKey(0);
*
*/
public class ImageGui extends JPanel implements KeyListener {

public ImageGui(Mat m, String window) {
super();
init(m, window);
}

//Elements for paint.
private Mat mat;
private boolean firstPaint = true;
private BufferedImage out;
int type;
private String WINDOW = "";
private JFrame jframe = new JFrame();
byte[] data;
private void Mat2BufIm(){
mat.get(0, 0, data);
out.getRaster().setDataElements(0, 0, mat.cols(), mat.rows(), data);
}
private void init(Mat m,String window){
this.mat = m;
data = new byte[mat.cols() * mat.rows() * (int)mat.elemSize()];

WINDOW = window;

if(mat.channels() == 1)
type = BufferedImage.TYPE_BYTE_GRAY;
else
type = BufferedImage.TYPE_3BYTE_BGR;
out = new BufferedImage(mat.cols(), mat.rows(), type);
Mat2BufIm();
jframe.add(this);
jframe.setSize(mat.cols(), mat.rows());
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jframe.setTitle(WINDOW);
jframe.addKeyListener(this);

}
@Override
public void paintComponent(Graphics g) {
g.drawImage(out, 0, 0, null);
}
public void imshow(){
if(firstPaint){
jframe.setVisible(true);
firstPaint = false;
}
Mat2BufIm();
this.repaint();
}

//Elements for waitKey.
private static Object mt = new Object();
private static int lastKey = 0;
private static int key = 0;
public static int waitKey(int millisecond){
//TODO 实现监听键盘
try {
if(millisecond == 0){
synchronized(mt){
mt.wait();
}

}
Thread.sleep(millisecond);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int ret = -1;
if(key != lastKey){
ret = key;
lastKey = key;
}

return ret;

}
@Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
//      System.out.println(e.getKeyChar() + ", " + e.getKeyCode()
//                + ", " + KeyEvent.getKeyText(e.getKeyCode())
//                + ", isActionKey: " + e.isActionKey());
synchronized(mt){
mt.notifyAll();
}
this.key = e.getKeyCode();

}
@Override
public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub

}
@Override
public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub

}

}