Draw 20% of one image and 80% of another?

Question

Hi all,
I'm creating a UI functionality whereby a user holds down a button and an image of a glass slowly fills up.
The way I'm thinking of implementing this is to have two different images, one of the empty glass and one of the full glass. As the user holds down the button, the image of the first is slowly replaced by the image of the second. E.g., after one second, 20% of the full image is shown at the bottom, 80% of the first is shown at the top.
The timing stuff I think I can do with a thread, so I'm not too worried about that. However, what I need is a simple method, or maybe a whole class, that can take two images and draw x% of one on the bottom and y% of the other on the top.
Can anyone think of a simple way to implement this?
Thanks,
Tim

Answer 1

Hmmm... after playing with that a while, it doesn't look like that will do the trick. As far as I can tell, the drawImage methods will always scale the image if you pass it in a rectangle of a different size. So trying to get 50% of a full glass on top of an empty glass results in a squished full glass.
Instead I realized I could do it using Graphs.clipRect, like so:
public class OverlayedImageIcon extends ImageIcon
     private Image overlayImage;
     private float overlayPercent;
     public OverlayedImageIcon(URL url)
         super(url);
     public void setOverlayImage(Image image){
          this.overlayImage = image;
          loadImage(overlayImage);
     public void setOverlayPercent(float percent){
          this.overlayPercent = percent;
     public synchronized void paintIcon(Component c, Graphics g, int x, int y) {
          super.paintIcon(c, g, x, y);
          Shape oldClip = g.getClip();
          int subtractHeight = (int) ((float)getIconHeight() * overlayPercent);
          g.clipRect(0, getIconHeight() - subtractHeight, getIconWidth(), getIconHeight());
        g.drawImage(overlayImage, x, y, getIconWidth(), getIconHeight(), getImageObserver());
        g.setClip(oldClip);
}Thanks for pointing me in the right direction, though!