Java 获取象素点的值及R,G,B分量的值

package sy;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

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

public class PanelTest extends JPanel {
public BufferedImage image;
   @Override
protected void paintComponent(Graphics g) {
// TODO Auto-generated method stub
super.paintComponent(g);
BufferedImage subImage=this.image.getSubimage(30, 30, 100, 100);
g.drawImage(subImage,100,100,100,100,null);
int color_point=subImage.getRGB(24, 4);
        Color color=new Color(color_point);
        System.out.println(color_point);
        System.out.print(color.getGreen());
}
   public PanelTest()
   {
   try {
this.image=ImageIO.read(new File("D:/black.jpg"));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
   this.setSize(300, 200);
   this.setLocation(100, 100);
   this.setBorder(BorderFactory.createTitledBorder("title"));
  // repaint();
   }
}