Change the alpha value of a BufferedImage?

Question

How do I change the global alpha value of a BufferedImage in Java? (I.E. make every pixel in the image that has a alpha value of 100 have a alpha value of 80)

Answer 1

I'm 99% sure the methods that claim to deal with an "RGB" value packed into an int actually deal with ARGB. So you ought to be able to do something like:

for (all x,y values of image) {
  int argb = img.getRGB(x, y);
  int oldAlpha = (argb >>> 24);
  if (oldAlpha == 100) {
    argb = (80 << 24) | (argb & 0xffffff);
    img.setRGB(x, y, argb);
  }
}

For speed, you could maybe use the methods to retrieve blocks of pixel values.