Đăng Nguyễn Đăng Nguyễn - 4 months ago 45
Java Question

Save image from JPanel after draw

I'm newbie in jave, my first project is draw, and save a image from JPanel, my draw is done, but I cant save it after I draw in JPanel :(, So can you help me to fix it
when I open the image after draw, It doesn't contain anything :(
here my codes:

package image;
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.nio.file.Path;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;


public class paint extends JFrame{
private Point points[] = new Point[10000];
private Point pointends[] = new Point[10000];
private int pointCount = 0;
private JButton save_btn;
public paint()
{
panel paint2 = new panel();
add(paint2,BorderLayout.CENTER);
}
private class panel extends JPanel
{
private paint my_paint;
public panel()
{
setBackground(Color.WHITE);
save_btn = new JButton();
save_btn.setText("123");
this.add(save_btn);
ButtonHandler handler1 = new ButtonHandler();
save_btn.addActionListener(handler1);
MouseHandler handler = new MouseHandler();
this.addMouseMotionListener(handler);

this.addMouseListener(handler);
}
private class ButtonHandler implements ActionListener
{

@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
savefile();
}

}
@Override
protected void paintComponent(Graphics g)
{
// TODO Auto-generated method stub
super.paintComponent(g);
for(int i = 0;i <pointCount;i++)
{
g.setColor(Color.RED);
g.drawLine(points[i].x, points[i].y, pointends[i].x, pointends[i].y);
}
}



private class MouseHandler extends MouseAdapter
{
@Override
public void mouseDragged(MouseEvent e)
{
// TODO Auto-generated method stub
pointends[ pointCount-1] = e.getPoint();
repaint();


}
@Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub
super.mousePressed(e);
if(pointCount < points.length)
{
points[ pointCount ] = e.getPoint();
pointends[ pointCount ] = e.getPoint();
pointCount++;
repaint();
}
}
@Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub
super.mouseReleased(e);
/*pointends[pointCount]=e.getPoint();
repaint();
pointCount++;
*/
}

}

}
public void savefile()
{
BufferedImage image2 = new BufferedImage(panel.WIDTH, panel.HEIGHT, BufferedImage.TYPE_INT_RGB);
JFileChooser jFile = new JFileChooser();
jFile.showSaveDialog(null);
Path pth = jFile.getSelectedFile().toPath();
JOptionPane.showMessageDialog(null, pth.toString());
Graphics2D graphics2D = image2.createGraphics();
try {
ImageIO.write(image2, "", new File(pth.toString()));
} catch (IOException ox) {
// TODO: handle exception
ox.printStackTrace();

}
}
}

Answer

Create BufferedImage to store your painting. When you paint, paint on BufferedImage.

When you need to display paint on JPanel, draw BufferedImage on JPanel.

This way, you can load / save painting to file.

Something like this:

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JPanel;

public class Paint extends JPanel{
    private BufferedImage paintImage = new BufferedImage(500, 400, BufferedImage.TYPE_3BYTE_BGR);

    @Override
    protected void paintComponent(Graphics g){
        super.paintComponent(g);
        g.drawImage(paintImage, 0, 0, null);
    }

    // draw painting
    public void updatePaint(){
        Graphics g = paintImage.createGraphics();

        // draw on paintImage using Graphics

        g.dispose();
        // repaint panel with new modified paint
        repaint();
    }

    public void save() throws IOException{
        ImageIO.write(paintImage, "PNG", new File("filename.png"));
    }

    public void load() throws IOException {
        paintImage = ImageIO.read(new File("filename.png"));
        // update panel with new paint image
        repaint();
    }
}
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