Draw dot/line on the current Jframe

Question

I am working on drawing a line or dot on the current Jframe.

I have already generated it and now i want to draw on it, without losing the frame data. I have gone through some suggestions but most of them suggests to redraw the Jframe. Some of them suggested to use Jpanel. Problem is that I am new here, and I dont think I am getting anywhere now without any help. So please can anyone help me with this..?

Sample code is given below

private static JFrame showImage(BufferedImage src){
    ImageIcon icon = new ImageIcon(img);
    JLabel lbl = new JLabel();
    lbl.setIcon(icon);
    JFrame frame = new JFrame("JFrame");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(lbl, BorderLayout.CENTER);
    frame.setSize(800, 600);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    return frame;
}

public static void main(String[] args) {
    try {

        //read image
        try{
            File f = new File("/home/amit/workspacenew/autocrop/screenshot_full_solid.png");
            img = ImageIO.read(f);
        }catch(IOException e){
            System.out.println(e);
        }

        JFrame frame = showImage(img);
        frame.addMouseListener(new MouseListener() {            
            @Override
            public void mouseClicked(MouseEvent e) {
                int x=e.getX();
                int y=e.getY();


                //need suggestion here
                drawdot(x, y);  
            }

        });                 

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