// r,g,b values are from 0 to 1
// h = [0,360], s = [0,1], v = [0,1]
//		if s == 0, then h = -1 (undefined)
void RGBtoHSV( float r, float g, float b, float *h, float *s, float *v )
{
	float min, max, delta;
	min = MIN( r, g, b );
	max = MAX( r, g, b );
	*v = max;				// v
	delta = max - min;
	if( max != 0 )
		*s = delta / max;		// s
	else {
		// r = g = b = 0		// s = 0, v is undefined
		*s = 0;
		*h = -1;
		return;
	}
	if( r == max )
		*h = ( g - b ) / delta;		// between yellow & magenta
	else if( g == max )
		*h = 2 + ( b - r ) / delta;	// between cyan & yellow
	else
		*h = 4 + ( r - g ) / delta;	// between magenta & cyan
	*h *= 60;				// degrees
	if( *h < 0 )
		*h += 360;
}
void HSVtoRGB( float *r, float *g, float *b, float h, float s, float v )
{
	int i;
	float f, p, q, t;
	if( s == 0 ) {
		// achromatic (grey)
		*r = *g = *b = v;
		return;
	}
	h /= 60;			// sector 0 to 5
	i = floor( h );
	f = h - i;			// factorial part of h
	p = v * ( 1 - s );
	q = v * ( 1 - s * f );
	t = v * ( 1 - s * ( 1 - f ) );
	switch( i ) {
		case 0:
			*r = v;
			*g = t;
			*b = p;
			break;
		case 1:
			*r = q;
			*g = v;
			*b = p;
			break;
		case 2
			*r = p;
			*g = v;
			*b = t;
			break;
		case 3:
			*r = p;
			*g = q;
			*b = v;
			break;
		case 4:
			*r = t;
			*g = p;
			*b = v;
			break;
		default:		// case 5:
			*r = v;
			*g = p;
			*b = q;
			break;
	}
}