BufferedImage and JTable

Question

I am trying to create a BufferedImage from a JTable so that I can convert it into a JPEG file, however,
I can't get seem to get the graphics into the BufferedImage unless I first put the table into a JFrame and set
it visible. Basically what I am doing is:
JTable table = new JTable("with simple parameters");
BufferedImage buf = new BufferedImage(table.getPrefferedSize.width,table.getPrefferedSize().height,TYPE_INT_RGB);
Graphics g = buf.getGraphics();
table.paint(g);
I have tried paint, paintAll, createGraphics and many more - none of them have worked unless I first put the table into a container and then set the container visible. I can get a label and button to print out this way without having to first set them visible, but I can't do it with a JTable. Does anybody know a way to fix this??
-Thanks for your help.

Answer 1

Here is an example that saves a JTable as a JPEG image:
import java.awt.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.awt.color.*;
import java.util.*;
import javax.swing.*;
import javax.swing.table.*;
import com.sun.image.codec.jpeg.*;
public class SaveJTable {
    public static void saveComponentAsJPEG(Component cmp, Container cont, String jpegfile) {
       Rectangle d = cmp.getBounds();
       BufferedImage bi = new BufferedImage(d.width, d.height, BufferedImage.TYPE_INT_RGB);
       Graphics2D g2d = bi.createGraphics();
       SwingUtilities.paintComponent(g2d,cmp,cont, 0,0,d.width,d.height);
       saveImageAsJPEG(bi, jpegfile);
   public static void saveImageAsJPEG(BufferedImage bi, String filename) {
      try {
         ByteArrayOutputStream boutstream = new ByteArrayOutputStream();
         JPEGImageEncoder enc = JPEGCodec.createJPEGEncoder(boutstream);
         enc.encode(bi);
         FileOutputStream fimage = new FileOutputStream(new File(filename));
         boutstream.writeTo(fimage);
         fimage.close();
      } catch (Exception e) { System.out.println(e); }
   public static void  main(String[] args){
      SaveJTable comp = new SaveJTable();
      JButton jb = new JButton("my button");
      jb.setSize(100,50);
      JPanel jp = new JPanel();
      String data[][] = {{"a","b","c"},
                         {"e","f","g"},
                         {"h","i","j"},
                         {"k","l","m"}};
      String colnames[] = {"col1", "col2", "col3"};
      JTable jtb = new JTable(data, colnames);
      JFrame jf = new JFrame();
      JScrollPane jsp = new JScrollPane(jtb);
      jf.getContentPane().add(jsp);
      jf.pack();
      comp.saveComponentAsJPEG(jsp,jf.getContentPane(),"jtable.jpg");
      System.exit(0);
}In the main() method, I created a sample JTable and put in in a JScrollPane. For some reason, the saved image doesn't show the column names if I don't put the JTable in a JScrollPane (no time to debug, sorry). So, I saved the JScrollPane instead of JTable.