一般大家将做的线图做成jpg都是怎样完成的？

//看看这个例子吧
import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import java.awt.image.*;
import java.awt.*;public class ChartGraphics {
  BufferedImage image;
  public void createImage(String fileLocation) {
    try {
      FileOutputStream fos = new FileOutputStream(fileLocation);
      BufferedOutputStream bos = new BufferedOutputStream(fos);
      JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
      encoder.encode(image);
      bos.close(); 
    } catch(Exception e) {
      System.out.println(e);
    }
  }  
  
  public void graphicsGeneration() {
    int h1,int h2,int h3,int h4,int h5;
    final int X=10;
    int imageWidth = 300;//图片的宽度
    int imageHeight = 300;//图片的高度   
    int columnWidth=30;//柱的宽度
    int columnHeight=200;//柱的最大高度
   
    h1=h2=h3=h4=h5=100;    
    ChartGraphics chartGraphics = new ChartGraphics();
    chartGraphics.image = new BufferedImage(imageWidth, imageHeight, BufferedImage.TYPE_INT_RGB); 
    Graphics graphics = chartGraphics.image.getGraphics();
    graphics.setColor(Color.white);
    graphics.fillRect(0,0,imageWidth,imageHeight);    
    graphics.setColor(Color.red);
    graphics.drawRect(X+1*columnWidth, columnHeight-h1, columnWidth, h1);
    graphics.drawRect(X+2*columnWidth, columnHeight-h2, columnWidth, h2);
    graphics.drawRect(X+3*columnWidth, columnHeight-h3, columnWidth, h3);    
    graphics.drawRect(X+4*columnWidth, columnHeight-h4, columnWidth, h4);
    graphics.drawRect(X+5*columnWidth, columnHeight-h5, columnWidth, h5);    
    chartGraphics.createImage("E:\\resin211\\doc\\chart\\chart.jpg");
  } 
}