Changing Image Opacity

Question

In a project, I want to simultaneously resize and change the opacity of an image. So far I think I've got the resizing down. I use a method defined like so to accomplish the resizing:

public BufferedImage resizeImage(BufferedImage originalImage, int type){

    initialWidth += 10;
    initialHeight += 10;
    BufferedImage resizedImage = new BufferedImage(initialWidth, initialHeight, type);
    Graphics2D g = resizedImage.createGraphics();
    g.drawImage(originalImage, 0, 0, initialWidth, initialHeight, null);
    g.dispose();

    return resizedImage;
} 

I got this code from here. What I can't find a solution to is changing the opacity. That's what I'm wondering how to do (if it's possible at all). Thanks in advance.

UPDATE:

I tried this code to display a picture of a circle with transparent insides and outsides (see below image) growing and becoming less and less opaque, but it didn't work. I'm not sure what's wrong. All the code is in a class called Animation

public Animation() throws IOException{

    image = ImageIO.read(new File("circleAnimation.png"));
    initialWidth = 50;
    initialHeight = 50;
    opacity = 1;
}

public BufferedImage animateCircle(BufferedImage originalImage, int type){

      //The opacity exponentially decreases
      opacity *= 0.8;
      initialWidth += 10;
      initialHeight += 10;

      BufferedImage resizedImage = new BufferedImage(initialWidth, initialHeight, type);
      Graphics2D g = resizedImage.createGraphics();
      g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity));
      g.drawImage(originalImage, 0, 0, initialWidth, initialHeight, null);
      g.dispose();

      return resizedImage;

}

I call it like this:

Animation animate = new Animation();
int type = animate.image.getType() == 0? BufferedImage.TYPE_INT_ARGB : animate.image.getType();
BufferedImage newImage;
while(animate.opacity > 0){

    newImage = animate.animateCircle(animate.image, type);
    g.drawImage(newImage, 400, 350, this);

}

Answer 1

first make sure the type you're passing into to method contains an alpha channel, like

BufferedImage.TYPE_INT_ARGB

and then just before you paint the new image, call the Graphics2D method setComposite like so:

float opacity = 0.5f;
g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, opacity));

that will set the drawing opacity to 50%.