Creating an image and Drawing to it.

[Madhur Baheti]

Hi.Using a component's graphics context, you usually draw shapes on the component. How can i draw to an image. Suppose i want to draw a circle.But rather than displaying it on a window, I want it to be drawn as a gif image with a white background, how can i do that? The image does not exist and I want to create it from scratch.
Thank You.

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
 
public class CreatingAnImage
{
    public static void main(String[] args)
    {
        ImageMaker imageMaker = new ImageMaker();
        ImageSaver imageSaver = new ImageSaver(imageMaker);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(imageSaver.getUIPanel(), "North");
        f.getContentPane().add(imageMaker);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
class ImageMaker extends JPanel
{
    int width, height;
    BufferedImage image;
 
    public ImageMaker()
    {
        width = 120;
        height = 120;
        createImage();
        setBackground(Color.black);
    }
 
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        int w = getWidth();
        int h = getHeight();
        int x = (w - width)/2;
        int y = (h - height)/2;
        AffineTransform at = AffineTransform.getTranslateInstance(x, y);
        g2.drawRenderedImage(image, at);
    }
 
    /**
     * Here's how you make an image
     */
    private void createImage()
    {
        image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setPaint(Color.white);
        g2.fillRect(0, 0, width, height);
        g2.setPaint(Color.red);
        int cx = width/2;
        int cy = height/2;
        int dia = width*3/4;
        g2.draw(new Ellipse2D.Double(cx - dia/2, cy - dia/2, dia, dia));
        g2.dispose();
    }
}
 
class ImageSaver
{
    ImageMaker imageMaker;
 
    public ImageSaver(ImageMaker im)
    {
        imageMaker = im;
    }
 
    public JPanel getUIPanel()
    {
        JButton save = new JButton("save");
        save.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                try
                {
                    ImageIO.write(imageMaker.image, "png", new File("example.png"));
                }
                catch(IOException ioe)
                {
                    System.out.println("write: " + ioe.getMessage());
                }
            }
        });
        JPanel panel = new JPanel();
        panel.add(save);
        return panel;
    }
}