import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.imageio.ImageIO;


public class ImageIOTest {
	public static void main(String[] args) throws IOException {
		BufferedImage buf;
		buf = new BufferedImage(128, 128, BufferedImage.TYPE_INT_BGR);
		Graphics2D g = buf.createGraphics();
		g.setColor(Color.MAGENTA);
		g.drawRect(0, 0, 100, 60);
		ByteArrayOutputStream bo = new ByteArrayOutputStream();
		ImageIO.write(buf, "PNG", bo);
		byte[] bytes = bo.toByteArray();
	}
}