I have a panel with transparent background which i use to draw an image. now problem here is when i draw anything on panel and save the image as a JPEG file its saving the image with black background but i want it to be saved as same, as i draw on the panel. what should be done for this? plz guide me

j Client.java

public class Client extends Thread 
{
    static DatagramSocket datasocket;
     static DatagramSocket socket;
    Point point;
    Whiteboard board;  
    Virtualboard virtualboard;
    JLayeredPane layerpane;

    BufferedImage image;
    public Client(DatagramSocket datasocket)
    {
            Client.datasocket=datasocket;
    }
    //This function is responsible to connect to the server 
    public static void connect()
    {
        try
        {           
            socket=new DatagramSocket (9000); //client connection socket port= 9000
            datasocket=new DatagramSocket (9005); //client data socket port= 9002
            ByteArrayOutputStream baos=new ByteArrayOutputStream();
            DataOutputStream dos=new DataOutputStream(baos);
            //this is to tell server that this is a connection request
            dos.writeChar('c');
            dos.close();
            byte[]data=baos.toByteArray();
            //Server IP address
            InetAddress ip=InetAddress.getByName("10.123.97.154");
            //create the UDP packet
            DatagramPacket packet=new DatagramPacket(data, data.length,ip , 8000);
            socket.send(packet);
            Client client=new Client(datasocket);
            client.createFrame();
            client.run();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
    //This function is to create the JFrame 
    public void createFrame()
    {       
         JFrame frame=new JFrame("Whiteboard");

         frame.setVisible(true);
         frame.setBackground(Color.black);
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setSize(680,501);
         frame.addWindowListener(new WindowAdapter() 
         {
             public void windowOpened(WindowEvent e) {}
             public void windowClosing(WindowEvent e) 
             {               
                 close();
             }          
         });                 

         layerpane=frame.getLayeredPane();
         board= new Whiteboard(datasocket); 

         image = new BufferedImage(590,463, BufferedImage.TYPE_INT_ARGB);
         board.setBounds(74,2,590,463);
         board.setImage(image);
         virtualboard=new Virtualboard();
         virtualboard.setImage(image);
         virtualboard.setBounds(74,2,590,463);

        layerpane.add(virtualboard,new Integer(2));//Panel where remote user draws 
        layerpane.add(board,new Integer(3));
        layerpane.add(board.colourButtons(),new Integer(1));
        layerpane.add(board.shapeButtons(),new Integer(0));

        //frame.add(paper.addButtons(),BorderLayout.WEST);
    }

    /*
     * This function is overridden from the thread class
     * This function listens for incoming packets from the server 
     * which contains the points drawn  by the other client
    */
    public void run () 
    {       
            while (true) 
            {
                try 
                {
                    byte[] buffer = new byte[512];
                    DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
                    datasocket.receive(packet);
                    InputStream in=new ByteArrayInputStream(packet.getData(), packet.getOffset(),packet.getLength());
                    DataInputStream din=new DataInputStream(in);              
                    int x=din.readInt();
                    int y=din.readInt();
                    String varname=din.readLine();
                    String var[]=varname.split("-",4);
                    point=new Point(x,y);
                    virtualboard.addPoint(point, var[0], var[1],var[2],var[3]);                 
              }
                catch (IOException ex) 
                {
                    ex.printStackTrace();
                }
        }       
    }

    //This function is to broadcast the newly drawn point to the server 
    public   void  broadcast (Point p,String varname,String shape,String event, String color) 
    {
        try
        {
            ByteArrayOutputStream baos=new ByteArrayOutputStream();
            DataOutputStream dos=new DataOutputStream(baos);
            dos.writeInt(p.x);
            dos.writeInt(p.y);
            dos.writeBytes(varname);
            dos.writeBytes("-");
            dos.writeBytes(shape);
            dos.writeBytes("-");
            dos.writeBytes(event);
            dos.writeBytes("-");
            dos.writeBytes(color);
            dos.close();
            byte[]data=baos.toByteArray();
            InetAddress ip=InetAddress.getByName("10.123.97.154");
            DatagramPacket packet=new DatagramPacket(data, data.length,ip , 8002);
            datasocket.send(packet);
        }
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }
     //This function is to close the client's connection with the server 
    public void close() 
    {
        try
        {
            ByteArrayOutputStream baos=new ByteArrayOutputStream();
            DataOutputStream dos=new DataOutputStream(baos);
            //This is to tell server that this is request to remove  the client
            dos.writeChar('r');
            dos.close();
            byte[]data=baos.toByteArray();
            //Server IP address
            InetAddress ip=InetAddress.getByName("10.123.97.154");
            DatagramPacket packet=new DatagramPacket(data, data.length,ip , 8000);
            socket.send(packet);
            System.out.println("closed");
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }
    public static  void main(String[] args) throws Exception  
    {            
        connect();
    }

}

Whiteboard.java

class   Whiteboard extends JPanel implements MouseListener,MouseMotionListener,ActionListener,KeyListener
{
    BufferedImage image;
    Boolean tooltip=false;
    int post;
    String shape;
    String selectedcolor="black";
    Color color=Color.black;
    //Color color=Color.white;
    Point start;
    Point end;
    Point mp;
    Point tip;
    int keycode;
    String fillshape;
    Point fillstart=new Point();
    Point fillend=new Point();
    int noofside;
    Button r=new Button("rect");
    Button rectangle=new Button("rect");
    Button line=new Button("line");
    Button roundrect=new Button("roundrect");
    Button polygon=new Button("poly");
    Button text=new Button("text");
    JButton save=new JButton("Save");
    Button elipse=new Button("elipse");
    ImageIcon fillicon=new ImageIcon("images/fill.jpg");
    JButton fill=new JButton(fillicon); 
    ImageIcon erasericon=new ImageIcon("images/eraser.gif");
    JButton erase=new JButton(erasericon);
    JButton[] colourbutton=new JButton[28];
    String selected;
    Point label;
    String key="";
    int ex,ey;//eraser
    DatagramSocket dataSocket;
    JButton button = new JButton("test");
    Client client;
    Boolean first;
    int w,h;
    public Whiteboard(DatagramSocket dataSocket) 
    {        
        try 
        {           
            UIManager.setLookAndFeel(
                    UIManager.getCrossPlatformLookAndFeelClassName());

        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }

        setLayout(null);
        setOpaque(false);
        setBackground(new Color(237,237,237));
        this.dataSocket=dataSocket;
        client=new Client(dataSocket);
        addKeyListener(this);
        addMouseListener(this);
        addMouseMotionListener(this);
        setBorder(BorderFactory.createLineBorder(Color.black));            
    }
       public  void paintComponent(Graphics g) 
       {          
        try
        {           
            super.paintComponent(g);
            g.drawImage(image, 0, 0, this);
            Graphics2D g2 = (Graphics2D)g;
            if(color!=null)
            g2.setPaint(color);
            if(start!=null && end!=null)
            {
                if(selected==("elipse"))
                    g2.drawOval(start.x, start.y,(end.x-start.x),(end.y-start.y));
                else if(selected==("rect"))
                    g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y));
                else if(selected==("rrect"))
                    g2.drawRoundRect(start.x, start.y, (end.x-start.x),(end.y-start.y),11,11);
                else if(selected==("line"))
                    g2.drawLine(start.x,start.y,end.x,end.y);
                else if(selected==("poly"))
                {
                    g2.drawLine(start.x,start.y,end.x,end.y);
                    client.broadcast(start, "start", "poly", "drag", selectedcolor);
                    client.broadcast(end, "end", "poly", "drag", selectedcolor);
                }
            }

            if(tooltip==true)
            {  
                System.out.println(selected);

                if(selected=="text")
                {
                    g2.drawString("|", tip.x, tip.y-5);
                    g2.drawString("Click to add text", tip.x+10, tip.y+23);
                    g2.drawString("__", label.x+post, label.y);
                }

                if(selected=="erase")
                {
                    g2.setPaint(new Color(237,237,237));
                    g2.fillRect(tip.x-10,tip.y-10,10,10);
                    g2.setPaint(color);
                    g2.drawRect(tip.x-10,tip.y-10,10,10);

                }
            }

        }
            catch(Exception e)
            {}
    }
    //Function to draw the shape on image
    public  void draw()
    {       
        Graphics2D g2 = (Graphics2D) image.createGraphics();
        Font font=new Font("Times New Roman",Font.PLAIN,14);
        g2.setFont(font);
        g2.setPaint(color);
        if(start!=null && end!=null)
        {
            if(selected=="line")
                    g2.drawLine(start.x, start.y, end.x, end.y);
            else if(selected=="elipse")
                    g2.drawOval(start.x, start.y, (end.x-start.x),(end.y-start.y));
            else if(selected=="rect")
                    g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y));
            else if(selected==("rrect"))
                g2.drawRoundRect(start.x, start.y, (end.x-start.x),(end.y-start.y),11,11);
            else if(selected==("poly"))
            {
                g2.drawLine(start.x,start.y,end.x,end.y);
                client.broadcast(start, "start", "poly", "release", selectedcolor);
                client.broadcast(end, "end", "poly", "release", selectedcolor);
            }
            fillstart=start;
            fillend=end;
            fillshape=selected;
        }
        if(selected!="poly")
        {
            start=null;
            end=null;
        }
        if(label!=null)
        {
            if(selected==("text"))
            {
                g2.drawString(key,label.x,label.y);
                client.broadcast(label, key, "text", "release", selectedcolor);
            }
        }
        repaint();
        g2.dispose();
    } 

    //Function which provides the erase functionality
    public  void erase() 
    {
        Graphics2D pic=(Graphics2D) image.createGraphics();
        Color erasecolor=new Color(237,237,237);
        pic.setPaint(erasecolor);
        if(start!=null)
        pic.fillRect(start.x-10, start.y-10, 10, 10);
    }
    //To set the size of the image
    public void setImage(BufferedImage image)
    {
        this.image = image;
     }
    //Function to add buttons into the panel, calling this function returns a panel  
    public JPanel shapeButtons()
    {       
        JPanel shape=new JPanel();
        shape.setBackground(new Color(181, 197, 210));
        shape.setLayout(new GridLayout(5,2,2,4));
        shape.setBounds(0, 2, 74, 166);

        rectangle.addActionListener(this);
        rectangle.setToolTipText("Rectangle");
        line.addActionListener( this);
        line.setToolTipText("Line");
        erase.addActionListener(this);
        erase.setToolTipText("Eraser");
        roundrect.addActionListener(this);
        roundrect.setToolTipText("Round edge Rectangle");
        polygon.addActionListener(this);
        polygon.setToolTipText("Polygon");
        text.addActionListener(this);
        text.setToolTipText("Text");
        fill.addActionListener(this);
        fill.setToolTipText("Fill with colour");
        elipse.addActionListener(this);
        elipse.setToolTipText("Elipse");
        save.addActionListener(this);
        shape.add(elipse);
        shape.add(rectangle);
        shape.add(roundrect);
        shape.add(polygon);
        shape.add(line);
        shape.add(text);
        shape.add(fill);
        shape.add(erase);
        shape.add(save);

        return shape;
    }

    public JPanel colourButtons()
    {
        JPanel colourbox=new JPanel();

        colourbox.setBackground(new Color(181, 197, 210));
        colourbox.setLayout(new GridLayout(8,2,8,8));
        colourbox.setBounds(0,323,70,140);
        //colourbox.add(empty);
        for(int i=0;i<16;i++)
        {
            colourbutton[i]=new JButton();
            colourbox.add(colourbutton[i]);

            if(i==0)
                colourbutton[0].setBackground(Color.black);
            else if(i==1)
                colourbutton[1].setBackground(Color.white);
            else if(i==2)
                colourbutton[2].setBackground(Color.red);
            else if(i==3)
                colourbutton[3].setBackground(Color.orange);
            else if(i==4)
                colourbutton[4].setBackground(Color.blue);
            else if(i==5)
                colourbutton[5].setBackground(Color.green);
            else if(i==6)
                colourbutton[6].setBackground(Color.pink);
            else if(i==7)
                colourbutton[7].setBackground(Color.magenta);
            else if(i==8)
                colourbutton[8].setBackground(Color.cyan);
            else if(i==9)
                colourbutton[9].setBackground(Color.black);
            else if(i==10)
                colourbutton[10].setBackground(Color.yellow);
            else if(i==11)
                colourbutton[11].setBackground(new Color(131,168,43));
            else if(i==12)
                colourbutton[12].setBackground(new Color(132,0,210));
            else if(i==13)
                colourbutton[13].setBackground(new Color(193,17,92));
            else if(i==14)
                colourbutton[14].setBackground(new Color(129,82,50));
            else if(i==15)
                colourbutton[15].setBackground(new Color(64,128,128));

            colourbutton[i].addActionListener(this);
        }
        return colourbox;
    }
    public void fill()
    {
        if(selected=="fill")
        {
            Graphics2D g2 = (Graphics2D) image.getGraphics();

            g2.setPaint(color);
            System.out.println("Fill");
             if(fillshape=="elipse")
                g2.fillOval(fillstart.x, fillstart.y, (fillend.x-fillstart.x),(fillend.y-fillstart.y));
             else if(fillshape=="rect")
                g2.fillRect(fillstart.x, fillstart.y, (fillend.x-fillstart.x),(fillend.y-fillstart.y));
             else if(fillshape==("rrect"))
                g2.fillRoundRect(fillstart.x, fillstart.y, (fillend.x-fillstart.x),(fillend.y-fillstart.y),11,11);
            // else if(fillshape==("poly"))
            //   g2.drawPolygon(x,y,2);         
        }
        repaint();
    }
   //To save the image drawn
    public void save()
    {
        try 
        {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
            JFileChooser fc = new JFileChooser();
            fc.showSaveDialog(this);        
            encoder.encode(image);
            byte[] jpgData = bos.toByteArray();
            FileOutputStream fos = new FileOutputStream(fc.getSelectedFile()+".jpeg");
            fos.write(jpgData);
            fos.close();
            //add replce confirmation here          
        } 
        catch (IOException e) 
        {           
            System.out.println(e);
        }
    }
    public void mouseClicked(MouseEvent e) 
    {

    }
    @Override
    public void mouseEntered(MouseEvent e) 
    {

    }
    public void mouseExited(MouseEvent arg0) {

    }
    public void mousePressed(MouseEvent e) 
    {
            if(selected=="line"||selected=="text")
            {
                start=e.getPoint();
                client.broadcast(start,"start", selected,"press", selectedcolor);
            }
            else if(selected=="elipse"||selected=="rect"||selected=="rrect")
                mp = e.getPoint();
            else if(selected=="poly")
            {
                if(first==true)
                {
                    start=e.getPoint();
                    //client.broadcast(start,"start", selected,"press", selectedcolor);
                }
                else if(first==false)
                {
                    end=e.getPoint();
                    repaint();
                    //client.broadcast(end,"end", selected,"press", selectedcolor);
                }
            }
            else if(selected=="erase")
            {
                start=e.getPoint();
                erase();
            }
    }
    public void mouseReleased(MouseEvent e) 
    {
        if(selected=="text")
        {
            System.out.println("Reset");
            key="";
            post=0;
            label=new Point();
            label=e.getPoint();
            grabFocus();
        }
        if(start!=null && end!=null)
        {
            if(selected=="line")
            {
                end=e.getPoint();           
                client.broadcast(end,"end", selected,"release", selectedcolor);
                draw();
            }
            else if(selected=="elipse"||selected=="rect"||selected=="rrect")
            {
                end.x = Math.max(mp.x,e.getX());
                end.y = Math.max(mp.y,e.getY());
                client.broadcast(end,"end", selected,"release", selectedcolor);
                draw();
            }           
            else if(selected=="poly")
            {               
                draw();
                first=false;
                start=end;
                end=null;
            }           
        }       
    } 
    public void mouseDragged(MouseEvent e) 
    {
        if(end==null)
            end = new Point();

        if(start==null)
                start = new Point();

         if(selected=="line")
         {
            end=e.getPoint();
            client.broadcast(end,"end", selected,"drag", selectedcolor);
         }
        else if(selected=="erase")
        {
             start=e.getPoint();
             erase();
            client.broadcast(start,"start", selected,"drag", selectedcolor);
        }
        else if(selected=="elipse"||selected=="rect"||selected=="rrect")
        {
            start.x = Math.min(mp.x,e.getX());
            start.y = Math.min(mp.y,e.getY());
            end.x = Math.max(mp.x,e.getX());
            end.y = Math.max(mp.y,e.getY());
            client.broadcast(start,"start", selected,"drag", selectedcolor);
            client.broadcast(end,"end", selected,"drag", selectedcolor);
        }
        else if(selected=="poly")
            end=e.getPoint();
        System.out.println(tooltip);
        if(tooltip==true)
        {               

            if(selected=="erase")
            {
                Graphics2D g2=(Graphics2D) getGraphics();
                tip=e.getPoint();
                g2.drawRect(tip.x-10,tip.y-10,10,10);
            }           
        }
        repaint();
    }
    public void mouseMoved(MouseEvent e)    
    {   
        if(selected=="text" ||selected=="erase")
        {
            tip=new Point();
            tip=e.getPoint();
            tooltip=true;
            repaint();
        }
    } 
    public void actionPerformed(ActionEvent e) 
    {
        if(e.getSource()==elipse)
            selected="elipse";
        else if(e.getSource()==line)
            selected="line";    
        else if(e.getSource()==rectangle)
            selected="rect";
        else if(e.getSource()==erase)
        {
            selected="erase";
            tooltip=true;
            System.out.println(selected);
            erase();
        }
        else if(e.getSource()==roundrect)
                selected="rrect";
        else if(e.getSource()==polygon)
        {
            selected="poly";
            first=true;
            start=null;
        }
        else if(e.getSource()==text)
        {
            selected="text";
            tooltip=true;
        }
        else if(e.getSource()==fill)
        {
            selected="fill";
            fill();         
        }
        else if(e.getSource()==save)
            save();

        if(e.getSource()==colourbutton[0])
        {
            color=Color.black;
            selectedcolor="black";
        }
        else if(e.getSource()==colourbutton[1])
        {
            color=Color.white;
            selectedcolor="white";
        }
        else if(e.getSource()==colourbutton[2])
        {
            color=Color.red;
            selectedcolor="red";
        }
        else if(e.getSource()==colourbutton[3])
        {
            color=Color.orange;
            selectedcolor="orange";
        }
        else if(e.getSource()==colourbutton[4])
        {           
            selectedcolor="blue";
            color=Color.blue;
        }
        else if(e.getSource()==colourbutton[5])
        {
            selectedcolor="green";
            color=Color.green;
        }
        else if(e.getSource()==colourbutton[6])
        {
            selectedcolor="pink";
            color=Color.pink;
        }
        else if(e.getSource()==colourbutton[7])
        {
            selectedcolor="magenta";
            color=Color.magenta;
        }
        else if(e.getSource()==colourbutton[8])
        {
            selectedcolor="cyan";
            color=Color.cyan;
        }
    }
    @Override
    public void keyPressed(KeyEvent e) 
    {
        //System.out.println(e.getKeyChar()+" : "+e.getKeyCode());

        if(label!=null)
        {
            if(e.getKeyCode()==10) //Check for Enter key
            {
                label.y=label.y+14;
                key="";
                post=0;
                repaint();
            }
            else if(e.getKeyCode()==8) //Backspace
            {
                try{
                Graphics2D g2 = (Graphics2D) image.getGraphics();
                g2.setPaint(new Color(237,237,237));
                g2.fillRect(label.x+post-7, label.y-13, 14, 17);
                if(post>0)
                post=post-6;
                keycode=0;
                key=key.substring(0, key.length()-1);
                System.out.println(key.substring(0, key.length()));
                repaint();
                Point broadcastlabel=new Point();
                broadcastlabel.x=label.x+post-7;
                broadcastlabel.y=label.y-13;
                client.broadcast(broadcastlabel, key, "text", "backspace", selectedcolor);
                }
                catch(Exception ex)
                {}
            }
            //Block invalid keys
            else if(!(e.getKeyCode()>=16 && e.getKeyCode()<=20 
                        || e.getKeyCode()>=112 && e.getKeyCode()<=123
                        || e.getKeyCode()>=33 && e.getKeyCode()<=40
                        || e.getKeyCode()>=144 && e.getKeyCode()<=145
                        || e.getKeyCode()>=524 && e.getKeyCode()<=525
                        ||e.getKeyCode()==27||e.getKeyCode()==155
                        ||e.getKeyCode()==127))
            {
                key=key+e.getKeyChar();
                post=post+6;
                draw();
            }
        }
    }
    @Override
    public void keyReleased(KeyEvent e) 
    {

    }
    @Override
    public void keyTyped(KeyEvent e) 
    {

    }
} 

class Button extends JButton
{
    String name;
    int i;
    public Button(String name) 
    {
        this.name=name;         
        try 
        {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }
    public Button(int i) 
    {
        this.i=i;
    }
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        //g2.setStroke(new BasicStroke(1.2f));
        if (name == "line")     g.drawLine(5,5,30,30);   
        if (name == "elipse") g.drawOval(5,7,25,20);
        if (name== "rect") g.drawRect(5,5,25,23);
        if (name== "roundrect") g.drawRoundRect(5,5,25,23,10,10);
        int a[]=new int[]{20,9,20,23,20};
        int b[]=new int[]{9,23,25,20,9};
        if (name== "poly") g.drawPolyline(a, b, 5);
        if (name== "text") g.drawString("Text",8, 24);

    }
}