Filling an Image

I have an image with index transparency.

The image renders fine and everything. The problem is that I want to draw the image’s “shadow”. Right now, I’m shearing it with a composite and using the Xor AlphaComposite because it seems to work and give me a black shadow. I want to have a grey-black shadow, instead of a solid black shadow, but when I try to give the Xor composite a 2nd parameter, nothing gets drawn.

Any recommendations here? Should I just break down and make the shadows myself?