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src/Source/FreeImage/WuQuantizer.cpp  view on Meta::CPAN

			break;
	}

	return 0;
}


// Compute remainder of Vol(cube, mmt), substituting pos for
// r1, g1, or b1 (depending on dir)

LONG 
WuQuantizer::Top(Box *cube, BYTE dir, int pos, LONG *mmt) {
    switch(dir)
	{
		case FI_RGBA_RED:
			return( mmt[INDEX(pos, cube->g1, cube->b1)] 
				   -mmt[INDEX(pos, cube->g1, cube->b0)]
				   -mmt[INDEX(pos, cube->g0, cube->b1)]
				   +mmt[INDEX(pos, cube->g0, cube->b0)] );
			break;
		case FI_RGBA_GREEN:
			return( mmt[INDEX(cube->r1, pos, cube->b1)] 
				   -mmt[INDEX(cube->r1, pos, cube->b0)]
				   -mmt[INDEX(cube->r0, pos, cube->b1)]
				   +mmt[INDEX(cube->r0, pos, cube->b0)] );
			break;
		case FI_RGBA_BLUE:
			return( mmt[INDEX(cube->r1, cube->g1, pos)]
				   -mmt[INDEX(cube->r1, cube->g0, pos)]
				   -mmt[INDEX(cube->r0, cube->g1, pos)]
				   +mmt[INDEX(cube->r0, cube->g0, pos)] );
			break;
	}

	return 0;
}

// Compute the weighted variance of a box 
// NB: as with the raw statistics, this is really the variance * ImageSize 

float
WuQuantizer::Var(Box *cube) {
    float dr = (float) Vol(cube, mr); 
    float dg = (float) Vol(cube, mg); 
    float db = (float) Vol(cube, mb);
    float xx =  gm2[INDEX(cube->r1, cube->g1, cube->b1)] 
			-gm2[INDEX(cube->r1, cube->g1, cube->b0)]
			 -gm2[INDEX(cube->r1, cube->g0, cube->b1)]
			 +gm2[INDEX(cube->r1, cube->g0, cube->b0)]
			 -gm2[INDEX(cube->r0, cube->g1, cube->b1)]
			 +gm2[INDEX(cube->r0, cube->g1, cube->b0)]
			 +gm2[INDEX(cube->r0, cube->g0, cube->b1)]
			 -gm2[INDEX(cube->r0, cube->g0, cube->b0)];

    return (xx - (dr*dr+dg*dg+db*db)/(float)Vol(cube,wt));    
}

// We want to minimize the sum of the variances of two subboxes.
// The sum(c^2) terms can be ignored since their sum over both subboxes
// is the same (the sum for the whole box) no matter where we split.
// The remaining terms have a minus sign in the variance formula,
// so we drop the minus sign and MAXIMIZE the sum of the two terms.

float
WuQuantizer::Maximize(Box *cube, BYTE dir, int first, int last , int *cut, LONG whole_r, LONG whole_g, LONG whole_b, LONG whole_w) {
	LONG half_r, half_g, half_b, half_w;
	int i;
	float temp;

    LONG base_r = Bottom(cube, dir, mr);
    LONG base_g = Bottom(cube, dir, mg);
    LONG base_b = Bottom(cube, dir, mb);
    LONG base_w = Bottom(cube, dir, wt);

    float max = 0.0;

    *cut = -1;

    for (i = first; i < last; i++) {
		half_r = base_r + Top(cube, dir, i, mr);
		half_g = base_g + Top(cube, dir, i, mg);
		half_b = base_b + Top(cube, dir, i, mb);
		half_w = base_w + Top(cube, dir, i, wt);

        // now half_x is sum over lower half of box, if split at i

		if (half_w == 0) {		// subbox could be empty of pixels!
			continue;			// never split into an empty box
		} else {
			temp = ((float)half_r*half_r + (float)half_g*half_g + (float)half_b*half_b)/half_w;
		}

		half_r = whole_r - half_r;
		half_g = whole_g - half_g;
		half_b = whole_b - half_b;
		half_w = whole_w - half_w;

        if (half_w == 0) {		// subbox could be empty of pixels!
			continue;			// never split into an empty box
		} else {
			temp += ((float)half_r*half_r + (float)half_g*half_g + (float)half_b*half_b)/half_w;
		}

    	if (temp > max) {
			max=temp;
			*cut=i;
		}
    }

    return max;
}

bool
WuQuantizer::Cut(Box *set1, Box *set2) {
	BYTE dir;
	int cutr, cutg, cutb;

    LONG whole_r = Vol(set1, mr);
    LONG whole_g = Vol(set1, mg);
    LONG whole_b = Vol(set1, mb);
    LONG whole_w = Vol(set1, wt);