A: 

Are you sure you should be using Graphics? I think it is semi-deprecated, and you're supposed to use Graphics2D nowadays.

With Graphics2D you can set the background color, which might help to prevent the unwanted transparency.

unwind
+1  A: 

Use g.setComposite(AlphaComposite.Src), like so:

Graphics2D g;
...
g.setComposite(AlphaComposite.Src)
g.copyArea(x,y,w,h,dx,dy);

Thanks to unwind for suggesting the use of Graphics2D.

ste