manipulation of Images in servlets

I have a application which can convert object into image (.jpg/.gif). Acme.Jpm.Encoder.* can download from
http://www.acme.com/java/software/Acme.JPM.Encoders.GifEncoder.ht
ml

import java.awt.*;
import Acme.JPM.Encoders.*;
import java.io.*;
import java.net.*;
import java.util.*;

public class Converter extends Frame
{
  TextCanvas canvas;
  String str = "VirtualSoft";
  Image bgImg;
  int width;
  int height;

  public Converter()
  {
    setVisible(true);
    setSize(300,300);
    GraphicsEnvironment gEnv = GraphicsEnvironment.getLocalGraphicsEnvironment();
    String envfonts[] = gEnv.getAvailableFontFamilyNames();
    setFont(new Font("Speedball Regular",Font.BOLD,48));

    String imgFile = "images/back42.jpg";
    bgImg = Toolkit.getDefaultToolkit().getImage(imgFile);
    MediaTracker mt = new MediaTracker(this);
    mt.addImage(bgImg,0);
    try
    {
      mt.waitForAll();
    }
    catch(Exception e){}
    canvas = new TextCanvas();
    add(canvas);
    repaint();
    canvas.createImage(str,bgImg,width,height);
  }
  public static void main(String args[])
  {
    new Converter();
  }

  private void setImgSize(int width, int height)
  {
     this.width=width;
     this.height=height;
  }

  public void paint(Graphics g){
    super.paint(g);
    Graphics2D g2 = (Graphics2D) g;
    FontMetrics metrics = g2.getFontMetrics();
    height = metrics.getHeight();
    width  = metrics.stringWidth(str);
    setImgSize(width,height);
  }
}

class TextCanvas extends Canvas
{
  int width;
  int height;
  String str;
  Image bgImg;

  TextCanvas()
  {
    setSize(200,200);
    setVisible(true);
    setBackground(Color.blue);
    GraphicsEnvironment gEnv = GraphicsEnvironment.getLocalGraphicsEnvironment();
    String envfonts[] = gEnv.getAvailableFontFamilyNames();
    setFont(new Font("Vivacious Regular",Font.BOLD,48));
  }
  public void createImage(String str,Image bgImg,int width,int height)
  {
    this.str=str;
    this.bgImg=bgImg;
    this.width=width;
    this.height=height;
    try
    {
      Graphics g;
      System.out.println(height);
      System.out.println(width);
      OutputStream fos =  new FileOutputStream("c:/Temp/Speedball.gif");
      Image img = this.createImage(width+20,height+10);
      g = img.getGraphics();
      this.paint(g);
      GifEncoder gifEncoder = new GifEncoder(img,fos);
      gifEncoder.encode();
      fos.flush();
      fos.close();
    }
    catch(Exception e)
    {
       System.out.println("Error: "+e.toString());
    }
  }

  public void paint(Graphics g)
  {
    super.paint(g);
    g.drawImage(bgImg,0,0,this);
    g.drawString(str,5 ,height-10);
  }
}

it work fine but when I want to do this work through servlets it was given exception on getGraphics().
I am trying to do this because I need a way to save and manipulation of images (i,e rotate, etc) on the server.  I am trying to avoid using an applet, and keep the returned servlet code pure html.

Thanks