Creating custom JButton from images containing transparent pixels

Question

Read edit 2 for what I\'m actually missing to make it work

I\'m currently trying to create some custom JButtons using images created in photoshop that have an

Answer 1

Since there were good elements in multiple answers, but none of the answers were complete on their own, I'll answer my own question so other people that have the same problem can try something similar.

I created my buttons using a new class which extends JButton, with a new constructor that takes a BufferedImage as parameter instead of an icon. The reason for that is that when I did something like myButton.getIcon(), it would return an Icon, then I'd have to make various manipulations on it to make it a BufferedImage of the right size, and it ended up not working anyway because it seems like the first cast to Icon made it lose the alpha data in the pixels, so I couldn't check to see if the user was clicking on transparent pixels or not.

So I did something like this for the constructor:

public class MyButton extends JButton
{
   private BufferedImage bufImg;

   public MyButton(BufferedImage bufImg)
   {
      super(new ImageIcon(bufImg));
      this.bufImg = bufImg;
   }
 }

Then I created an accessor for my bufImg that resized the image to fit the JButton using the getSize() method and then returned an image resized at the right size. I do the transformations in the getBufImg() accessor because the image size might change when the window gets resized. When you call the getBufImg(), it's usually because you clicked on the button and thus you're not currently resizing the window.

Something a little bit like this will return the image at the right size:

 public BufferedImage getBufImg()
    {
      BufferedImage newImg = new BufferedImage(getSize().getWidth(), getSize().getHeight(), BufferedImage.TYPE_INT_ARGB); //Create a new buffered image the right size
      Graphics2D g2d = newImg.createGraphics();
      g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);

      g2d.drawImage(bufImg, 0, 0, getSize().getWidth(), getSize().getHeight(), null);
      g2d.dispose();

      return newImg;
    }

With that buffered image, you can then code a method like this:

  private int clickAlphaValue(BufferedImage bufImg, int posX, int posY) 
  {
    int alpha;

    alpha = (bufImg.getRGB(posX, posY) >>24) & 0x000000FF; //Gets the bit that contains alpha information

    return alpha;
  }

That you call on the button that implements a MouseListener, like this:

myButton.addMouseListener(new MouseListener()
    {

    public void mouseClicked(MouseEvent e)
    {
    }

    public void mousePressed(MouseEvent e)
    {
    }

    public void mouseReleased(MouseEvent e)
    {
      if(clickAlphaValue(((myButton)e.getSource()).getBufImg(), e.getX(), e.getY()) != 0) //If alpha is not set to 0
        System.exit(0); //Or other things you want your button to do
    }

    public void mouseEntered(MouseEvent e)
    {
    }

    public void mouseExited(MouseEvent e)
    {
    }
  });

And voila! The button will only do the action if you clicked on non-transparent pixels.

Thanks for the help everyone, I couldn't have come up with this solutions on my own.