Shift RGB colors along RYB artistic color wheel

RGB_hue_shift_on_RYB_wheel.js

// Preview online
// http://www.deathbysoftware.com/colors/index.html

function rgb2ryb ( iRed, iGreen, iBlue )
{
	// Remove the white from the color
	var iWhite = Math.min( iRed, iGreen, iBlue );
	
	iRed   -= iWhite;
	iGreen -= iWhite;
	iBlue  -= iWhite;
	
	var iMaxGreen = Math.max( iRed, iGreen, iBlue );
	
	// Get the yellow out of the red+green
	
	var iYellow = Math.min( iRed, iGreen );
	
	iRed   -= iYellow;
	iGreen -= iYellow;
	
	// If this unfortunate conversion combines blue and green, then cut each in half to
	// preserve the value's maximum range.
	if (iBlue > 0 && iGreen > 0)
	{
		iBlue  /= 2;
		iGreen /= 2;
	}
	
	// Redistribute the remaining green.
	iYellow += iGreen;
	iBlue   += iGreen;
	
	// Normalize to values.
	var iMaxYellow = Math.max( iRed, iYellow, iBlue );
	
	if ( iMaxYellow > 0 )
	{
		var iN = iMaxGreen / iMaxYellow;
		
		iRed    *= iN;
		iYellow *= iN;
		iBlue   *= iN;
	}
	
	// Add the white back in.
	iRed    += iWhite;
	iYellow += iWhite;
	iBlue   += iWhite;
	
	return [ iRed, iYellow, iBlue ];
}

function ryb2rgb ( iRed, iYellow, iBlue )
{
	// Remove the whiteness from the color.
	var iWhite = Math.min( iRed, iYellow, iBlue );
	
	iRed    -= iWhite;
	iYellow -= iWhite;
	iBlue   -= iWhite;

	var iMaxYellow = Math.max( iRed, iYellow, iBlue );

	// Get the green out of the yellow and blue
	var iGreen = Math.min( iYellow, iBlue );
	
	iYellow -= iGreen;
	iBlue   -= iGreen;

	if ( iBlue > 0 && iGreen > 0 )
	{
		iBlue  *= 2.0;
		iGreen *= 2.0;
	}
	
	// Redistribute the remaining yellow.
	iRed   += iYellow;
	iGreen += iYellow;

	// Normalize to values.
	var iMaxGreen = Math.max( iRed, iGreen, iBlue );
	
	if ( iMaxGreen > 0 )
	{
		var iN = iMaxYellow / iMaxGreen;
		
		iRed   *= iN;
		iGreen *= iN;
		iBlue  *= iN;
	}
	
	// Add the white back in.
	iRed   += iWhite;
	iGreen += iWhite;
	iBlue  += iWhite;

	// Save the RGB	
	return [ iRed, iGreen, iBlue ];
}

// RGB2HSV and HSV2RGB are based on Color Match Remix [http://color.twysted.net/]
// which is based on or copied from ColorMatch 5K [http://colormatch.dk/]
function rgbToHsl( r, g, b )
{
	var h, s, l
	max = max3( r, g, b )
	dif = max - min3( r, g, b )
	s = ( max == 0.0 ) ? 0 : ( dif / max )
	if ( s == 0 ) h = 0
	else if ( r == max ) h = 60.0 * ( g - b ) / dif
	else if ( g == max ) h = 120.0 + 60.0 * ( b - r ) / dif
	else if ( b == max ) h = 240.0 + 60.0 * ( r - g ) / dif
	if ( h < 0.0 ) h += 360.0
	l = max
	h /= 360.0
	return [ h, s, l ]
}
 
function hslToRgb( h, s, l )
{
	var r, g, b
	if ( s == 0 ) return [ l, l, l ]
	else
	{
		var i, f, p ,q ,t
		h *= 6
		i = Math.floor( h )
		f = h - i
		p = l * ( 1 - s )
		q = l * ( 1 - s * f )
		t = l * ( 1 - s * ( 1 - f ) )
		switch( i ) 
		{
		case 0:  return [ l, t, p ]
		case 1:  return [ q, l, p ]
		case 2:  return [ p, l, t ]
		case 3:  return [ p, q, l ]
		case 4:  return [ t, p, l ]
		default: return [ l, p, q ]
		}
	}
}

//min max via Hairgami_Master (see comments)
function min3(a,b,c) { return ( a < b ) ? ( ( a < c ) ? a : c ) : ( ( b < c ) ? b : c ) } 
function max3(a,b,c) { return ( a > b ) ? ( ( a > c ) ? a : c ) : ( ( b > c ) ? b : c ) }

//Adding HueShift via Jacob (see comments)
function HueShift( h, s ) { h += s; while ( h >= 360.0 ) h -= 360.0; while ( h < 0.0 ) h += 360.0; return h; }



function ryb2rgb2 ( R, Y, B ) 
{
	R = R * R * ( 3 - 2 * R )
	Y = Y * Y * ( 3 - 2 * Y )
	B = B * B * ( 3 - 2 * B )
	return [1.0 + B * ( R * (0.337 + Y * -0.137) + (-0.837 + Y * -0.163) ),
		1.0 + B * ( -0.627 + Y * 0.287) + R * (-1.0 + Y * (0.5 + B * -0.693) - B * (-0.627) ),
		1.0 + B * (-0.4 + Y * 0.6) - Y + R * ( -1.0 + B * (0.9 + Y * -1.1) + Y )]
}


/*
function rotate_ryb( h, angle )
{

//	Returns a color rotated on the artistic RYB color wheel.

//	An artistic color wheel has slightly different opposites
//	(e.g. purple-yellow instead of purple-lime).
//	It is mathematically incorrect but generally assumed
//	to provide better complementary colors.

//	http://en.wikipedia.org/wiki/RYB_color_model

	h *= 360
	angle %= 360
	
//	log += h + "\n"
//	log += angle + "\n"

	// Approximation of Itten's RYB color wheel.
	// In HSB, colors hues range from 0-360.
	// However, on the artistic color wheel these are not evenly distributed. 
	// The second tuple value contains the actual distribution.
	wheel = 
	[
		[  0,   0], 
		[ 15,   8],
		[ 30,  17], 
		[ 45,  26],
		[ 60,  34], 
		[ 75,  41],
		[ 90,  48], 
		[105,  54],
		[120,  60], 
		[135,  81],
		[150, 103], 
		[165, 123],
		[180, 138], 
		[195, 155],
		[210, 171], 
		[225, 187],
		[240, 204], 
		[255, 219],
		[270, 234], 
		[285, 251],
		[300, 267], 
		[315, 282],
		[330, 298], 
		[345, 329],
		[360, 0  ]
	]

	// Given a hue, find out under what angle it is
	// located on the artistic color wheel.
	var a, x0, x1, y0, y1
	
	for ( var i = 0; i < wheel.length - 1; i++ )
	{
		x0 = wheel[i][0]
		y0 = wheel[i][1]
		x1 = wheel[i+1][0]
		y1 = wheel[i+1][1]
		//WScript.Echo( y0 + " <= " + h + " <= " + y1 + "?\n" )
		if ( y1 < y0 ) y1 += 360
		if ( ( y0 <= h ) && ( h <= y1 ) )
		{
			a = 1.0 * x0 + ( x1 - x0 ) * ( h - y0 ) / ( y1 - y0 ) // lerp
			break
		}
	}
	
	a = ( a + angle ) % 360
	
	// For the given angle, find out what hue is
	// located there on the artistic color wheel.
	for ( var i = 0; i < wheel.length-1; i++ )
	{
		x0 = wheel[i][0]
		y0 = wheel[i][1]
		x1 = wheel[i+1][0]
		y1 = wheel[i+1][1]
		if ( y1 < y0 ) y1 += 360
		if ( ( x0 <= a ) && ( a <= x1 ) )
		{
			h = 1.0 * y0 + ( y1 - y0 ) * ( a - x0 ) / ( x1 - x0 ) // lerp
			break
		}
	}

	h %= 360
	return h/360
}
*/

//----------------------- TESTING


var c = [ 0, 0, 1 ]

c = rgb2ryb( c[0], c[1], c[2] )
c = rgbToHsl( c[0], c[1], c[2] )

c[0] = HueShift( Math.round( c[0] * 360 ), 0 ) / 360.0

c = hslToRgb( c[0], c[1], c[2] )
c = ryb2rgb2( c[0], c[1], c[2] )

WScript.Echo( "complementary = " + [ Math.round( c[0] * 255 ), Math.round( c[1] * 255 ), Math.round( c[2] * 255 ) ] )

Thank you for this :)