private float Var(Box cube) {
    		/* Compute the weighted variance of a box */
    		/* NB: as with the raw statistics, this is really the variance * size */
    		float dr, dg, db, xx;
    		dr = Vol(cube, mr); 
    		dg = Vol(cube, mg); 
    		db = Vol(cube, mb);
    		xx =  m2[cube.r1][cube.g1][cube.b1] 
    			  -m2[cube.r1][cube.g1][cube.b0]
    			  -m2[cube.r1][cube.g0][cube.b1]
    			  +m2[cube.r1][cube.g0][cube.b0]
    			  -m2[cube.r0][cube.g1][cube.b1]
    			  +m2[cube.r0][cube.g1][cube.b0]
    			  +m2[cube.r0][cube.g0][cube.b1]
    			  -m2[cube.r0][cube.g0][cube.b0];
    		return  xx - (dr*dr + dg*dg + db*db)/Vol(cube,wt);    
    	}
Java port of
C Implementation of Wu's Color Quantizer (v. 2)
(see Graphics Gems vol. II, pp. 126-133)
Author:	Xiaolin Wu
Dept. of Computer Science
Univ. of Western Ontario
London, Ontario N6A 5B7
wu@csd.uwo.ca

Algorithm: Greedy orthogonal bipartition of RGB space for variance
minimization aided by inclusion-exclusion tricks.
For speed no nearest neighbor search is done. Slightly
better performance can be expected by more sophisticated
but more expensive versions.

The author thanks Tom Lane at Tom_Lane@G.GP.CS.CMU.EDU for much of
additional documentation and a cure to a previous bug.

Free to distribute, comments and suggestions are appreciated.
subs/gif-revert/src/main/java/com/engineer/gif/revert/lib/AnimatedGIFWriter.java