How to save image drawn on a JPanel?

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 DataOutputS开发者_Python百科tream(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);

    }
}

If you want transparency, you must use an RGBA image and save it as a PNG or a GIF. The JPEG format is for photos, not for the kind of drawings you are doing here.

Well, I'm not about to look at all that code to try and figure out what you are doing.

I'm not sure if it will work but you can try using the Screen Image class which tries to handle non-opaque backgrounds.