draw darkened bufferedimage without touching it

Question

I'm currently making a tile-based strategy game, with its map made of a bunch of sprites (BufferedImages), drawn by java.awt.Graphics.drawimage(..)

What i want is to be able to draw those sprites a tone darker if the player is too far away from them. I've seen a lot of similar questions but haven't found what i wanted. Is there a way to do this WITHOUT touching the original sprite? perhaps some other drawing function? or do i absolutely need to make a copy of each sprite? That'd make a mess of my game, sadly...

Answer 1

You can use Graphics2D.drawImage(BufferedImage image, BufferedImageOp op, int x, int y) and a RescaleOp to alter the colours when drawing the image:

g2.drawImage(image, new RescaleOp(
        new float[]{0.5f, 0.5f, 0.5f, 1f}, // scale factors for red, green, blue, alpha
        new float[]{0, 0, 0, 0}, // offsets for red, green, blue, alpha
        null), // You can supply RenderingHints here if you want to
    0, 0);

Note that how many scale factors/offsets you need and what band they operate on depend on the type of your image, the above will darken a BufferedImage of type ARGB but may produce other results for images of different types (or throw an exception if the image doesn't have 4 bands).