color.js

function dot(left, right) {
    return left[0] * right[0] + left[1] * right[1] + left[2] * right[2];
}

function clamp(vec3, lo, hi) {
    var ret = vec3.slice();
    for (var i = 0; i < 3; i++)
        ret[i] = ret[i] < lo ? lo : ret[i] > hi ? hi : ret[i];
    return ret;
}

function f(n, eps, k) {
	if (n > eps) {
		return Math.pow(n, 1.0 / 3.0);
	} else {
		return (k * n + 16.0) / 116.0;
	}
}

function xyzToRgb(xyz, clamp) {
	var m0 = [ 3.2404542, -1.5371385, -0.4985314];
	var m1 = [-0.9692660,  1.8760108,  0.0415560];
	var m2 = [ 0.0556434, -0.2040259,  1.0572252];

	var rgb = [dot(xyz, m0), dot(xyz, m1), dot(xyz, m2)];

  if (clamp)
    return clamp(rgb, 0.0, 1.0);
  else
    return rgb;
}

function labToXyz(lab) {
	var Xr = 0.95047;
	var Yr = 1.0;
	var Zr = 1.08883;

	var eps = 216.0 / 24389.0;
	var k = 24389.0 / 27.0;

	var l = lab[0];
	var a = lab[1];
	var b = lab[2];

	var fy = (l + 16.0) / 116.0;
	var fx = a / 500.0 + fy;
	var fz = -b / 200.0 + fy;

	var xr = (fx * fx * fx > eps) ? fx * fx * fx : (116.0 * fx - 16.0) / k;
	var lt = (l + 16.0) / 116.0;
	var yr = (l > k * eps) ? lt * lt * lt : l / k;
	var zr = (fz * fz * fz > eps) ? fz * fz * fz : (116.0 * fz - 16.0) / k;

	var x = xr * Xr;
	var y = yr * Yr;
	var z = zr * Zr;

	return [x, y, z];
}

function lchToLab(lch) {
	return [lch[0], lch[1] * Math.cos(lch[2]), lch[1] * Math.sin(lch[2])];
}

function labToRgb(lab) {
  return labToRgb(lab, true);
}

function labToRgb(lab, clamp) {
	return xyzToRgb(labToXyz(lab), clamp);
}

function lchToRgb(lch) {
    return xyzToRgb(labToXyz(lchToLab(lch)), true);
}

function getColors(lightness, chroma, numGroups) {
	var pi = 3.14159265358979323846264;
	var hueStep = 2.0 * pi / numGroups;
    var ret = [];
    for (var i = 0; i < numGroups; i++) {
        ret.push(lchToRgb([lightness, chroma, hueStep * i]));
    }

	return ret;
}

function lchInRange(lch) {
  var rgb = labToRgb(lchToLab(lch), false);
  return rgb[0] >= 0.0 && rgb[0] <= 1.0 &&
         rgb[1] >= 0.0 && rgb[1] <= 1.0 &&
         rgb[2] >= 0.0 && rgb[1] <= 1.0;
}

function findMaxC(L, h) {
  var lch1 = [L, 0, h];
  var lch2 = [L, 150, h];
  
  var inv = 0, outv = 100, mid = 0;
  for (var i = 0; i < 10; i++) {
    mid = (inv + outv) / 2;
    tmp = [L, mid, h];
    if (lchInRange(tmp))
      inv = mid;
    else
      outv = mid;
  }
  
  return inv;
}

function getColorsNew(L, numGroups) {
  var pi = 3.14159265358979323846264;
  
  var angle = 0.5;
  var angleOffset = pi;
  var spacing = (angleOffset * 2) / numGroups;
  
  var ret = [];
  
  for (var i = 0; i < numGroups; i++) {
    var h = spacing * i + angle - angleOffset;
    var c = findMaxC(L, h);
    
    var a = c * Math.cos(h);
    var b = c * Math.sin(h);
    ret.push(labToRgb([L, a, b]));
  }
  
  return ret;
}