title: ImageIO ignores PNG alpha channel
body: <p>It seems that PNG loaded with ImageIO.read ignore the alpha channel. 
  (I tried with JRE 6 update 20)</p>
  
  <p>Bug ?</p>
  
  <p>Example : </p>
  
  <pre><code>public class Test extends JFrame
  {
  
  public Test()
  {
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      JButton b = new JButton("Test");
      try
      {
          b.setIcon(new ImageIcon(ImageIO.read(new File("D:\\image.png"))));
      }
      catch (IOException e2)
      {
      }
      b.addActionListener(new ActionListener()
      {
          public void actionPerformed(ActionEvent e)
          {
          }
      });
      getContentPane().add(b, BorderLayout.CENTER);
      setSize(500,500);
      setVisible(true);
  }
  
  /**
   * @param args
   */
  public static void main(String[] args)
  {
      new Test();
  }
  </code></pre>
  
  <p>}</p>