It would probably be better to capture just the rectangle that the
irregularly shaped splash screen spans.

Hi all,
I figured it out myself. Here is the code if anyone may need it in the
future.

package mypackage;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JWindow;

public class TransparentSplash extends JPanel
{
   BufferedImage img = null;
   JLabel lblImage = null ;
   JWindow wind = new JWindow ( (Frame)null );
   
   public TransparentSplash ( String strSplashImageFile, int iWidth,
int iHeight ) throws Exception
   {
       setLayout ( new GridLayout ( 1,1 ) );
       setOpaque ( false );
       Robot rob = new Robot ( );
       
       Dimension screenSize = Toolkit.getDefaultToolkit (
).getScreenSize ( ) ;
       Dimension frameSize = new Dimension ( iWidth , iHeight ) ;
       if ( frameSize.height > screenSize.height )
       {
           frameSize.height = screenSize.height;
       }
       if ( frameSize.width > screenSize.width )
       {
           frameSize.width = screenSize.width;
       }
       int iX = ( screenSize.width - frameSize.width ) / 2 ;
       int iY = ( screenSize.height - frameSize.height ) / 2 ;
       
       img = rob.createScreenCapture ( new Rectangle ( iX , iY ,
iWidth , iHeight ) );
       
       lblImage = new JLabel ( new ImageIcon ( strSplashImageFile )
);
       lblImage.setOpaque ( false ) ;
       add ( lblImage );
       
       wind.setContentPane ( this );
       wind.setBounds(iX,iY,iWidth,iHeight);
       
       wind.addMouseListener( new MouseAdapter () {
           public void mouseClicked ( MouseEvent me )
           {
               wind.dispose();
               System.exit ( 0 );
           }
       });
       
       wind.setVisible(true);
   }
   
   public void paintComponent ( Graphics g )
   {
       g.drawImage ( img , 0 , 0 , getWidth ( ) , getHeight ( ) ,
this ) ;
       super.paintComponent ( g ) ;
   }

   /**
    *
    * @param args
    */
   public static void main(String[] args) throws Exception
   {
       TransparentSplash transparentSplash = new
TransparentSplash("/tmp/key.png", 600, 400);//this is a transparent
GIF which is the background of the spash screen
   }
}