Possible to layer ImageIcons?

Question

I was wondering if it were possible to layer ImageIcons in Java. I will be working with GIF images, and will have a grid of ImageIcons representing the "background" of my JPane.

When a certain condition is true, I need to be able to add an image that has transparency on top of the other image.

Regards, Jack Hunt

Answer 1

You could simply use g.drawImage(...) to draw them onto the panel in an overriden paintComponent method. That would be the easiest way to do that.

Because your question mentions ImageIcon, it would be correct to use it if your gif's are animated. Otherwise, BufferedImage is generally preferred. If you decide to keep to ImageIcon, you should use paintIcon(Component c, Graphics g, int x, int y) instead of g.drawImage(...).

If you want to add images dynamically, consider storing them in an array or ArrayList, then simply iterate through the array / list in your paintComponent.

For example:

JPanel panel = new JPanel(){
    @Override
    public void paintComponent(Graphics g){
       super.paintComponent(g);
       if(yourCondition){
           g.drawImage(img, x, y, this); // for example.
       }
    }
};

The other alternative is to create a private class which extends JPanel. For example:

public class OuterClass{
    // fields, constructors, methods etc..

    private class MyPanel extends JPanel{   
       // fields, constructors, methods etc..

       @Override
       public void paintComponent(Graphics g){
          super.paintComponent(g);
          if(yourCondition){
             g.drawImage(img, x, y, this); // for example.
          }
       }

    }
}

Side note: Any particular reason why you need to use GIF? PNG is generally better.

EDIT: (according to Andrew Thompson's idea)

In order to take a snapshot of all the images contained in the background...
A variant of the following idea:

BufferedImage background;

public void captureBackground(){
    BufferedImage img = GraphicsConfiguration.createCompatibleImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
    Graphics2D g = img.createGraphics();
    for(ImageIcon i : imageIconArray){ // could be for(BufferedImage i : imageArray){
         i.paintIcon(this, g, 0, 0);   // g.drawImage(i, 0, 0, null);
    }
    g.dispose();
    background = img;
    // either paint 'background' or add it to your background panel here.
}

Answer 2

yes that's possible and there are two correct ways

1) if is there only one Image then put JLabel with Icon to the GlassPane

2) use LayeredPane for <= Java6 (not Java7 user there is JLayer)

Answer 3

You can use the modes of AlphaComposite to achieve a variety of effects. There's an example and utility here.

Addendum: Note that the default composite mode for a platform's concrete implementation of Graphics2D is AlphaComposite.SRC_OVER, which may or may not be what you want.

Answer 4

You could use the Overlay Layout to stack JLabels on top of one another.

Or you could use the Compound Icon to stack icons on top of one another.