java TrayIcon使用具有透明背景的图像

我使用以下代码在Windows和Linux中设置托盘图标。它在Windows中工作得很好，在Linux中工作得很好。在Linux（Ubuntu）中，我的面板设置为（有点）透明，当我添加GIF（具有透明背景）时，图标的背景显示为灰色和丑陋（见图像，绿色菱形“！”）....关于如何使我正在添加的GIF图像“保留”其透明背景的任何想法？

可选文字 http://unarm.org/stackoverflow/panel_task.jpg

和我正在使用的图像，如果你想测试：

替代文本 http://unarm.org/stackoverflow/green_info.gif

import java.awt.*;
import java.awt.event.*;

public class TrayFun {


  static class ShowMessageListener implements ActionListener {
    TrayIcon trayIcon;
    String title;
    String message;
    TrayIcon.MessageType messageType;
    ShowMessageListener(
        TrayIcon trayIcon,
        String title,
        String message,
        TrayIcon.MessageType messageType) {
      this.trayIcon = trayIcon;
      this.title = title;
      this.message = message;
      this.messageType = messageType;
    }
    public void actionPerformed(ActionEvent e) {
      trayIcon.displayMessage(title, message, messageType);
    }
  }

  public static void main(String args[]) {
    Runnable runner = new Runnable() {
      public void run() {
        if (SystemTray.isSupported()) {
          final SystemTray tray = SystemTray.getSystemTray();
          Image image = Toolkit.getDefaultToolkit().getImage("green_info.png");
          PopupMenu popup = new PopupMenu();
          final TrayIcon trayIcon = new TrayIcon(image, "The Tip Text", popup);
          trayIcon.setImageAutoSize(true);

          MenuItem item = new MenuItem("Close");
      item.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
          tray.remove(trayIcon);
            }
      });
          popup.add(item);
          try {
            tray.add(trayIcon);
          } catch (AWTException e) {
            System.err.println("Can't add to tray");
          }
        } else {
          System.err.println("Tray unavailable");
        }
      }
    };
    EventQueue.invokeLater(runner);
  }
}