refreshing/reloading image in a Java Application (Swing)

I have made a programm to take a snapshot from the WebCam (via OpenCV) and safes it to the Project:

Colordetection
|__src
|    |
|   main.java
|
| Snapshot.png

Now I would like to refresh the taken snapshot, everytime I re-take one and repaint it.

String imgText = "Snapshot.png";

JPanel panelScreenshot = new JPanel();
panelScreenshot.setBorder(new TitledBorder(null, "Screenshot", TitledBorder.LEADING, TitledBorder.TOP, null, null));
panelScreenshot.setBounds(10, 11, 667, 543);
panelDisplay.add(panelScreenshot);
panelScreenshot.setLayout(null);

JLabel lblScreenshot = new JLabel();
lblScreenshot.setIcon(new ImageIcon(imgText));
lblScreenshot.setBounds(10, 21, 640, 480);
panelScreenshot.add(lblScreenshot);

JButton btnScreenshot = new JButton("Screenshot");
btnScreenshot.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent e) {                          
                                
                                
    VideoCapture cap = new VideoCapture(0);
                                
    if(!cap.isOpened()){
      System.out.println("Webcam not Found");
                
      } 
      else 
      {
      System.out.println("Found Webcam:" + cap.toString());
        
      Mat frame = new Mat();
      cap.retrieve(frame);
                                        
          try {
          Thread.sleep(500);
          Highgui.imwrite("Snapshot.png", frame);

          lblScreenshot.repaint();                                      
                                                
          } 
          catch (Exception e1) {
            e1.printStackTrace();
                                                
      }
      cap.release();                                    
    }           
  }
});

The Problem is, it doesn't repaint/refresh as I want to, only if I restart the programm, the new screenshot is there.

I also tryied it with:

ImageIcon icon = new ImageIcon(main.class.getResource("Snapshot.png"));

and changed the paths etc. but it didnt help.

does anyone has a clue?

thanks.