hsl-to-rgb.js

// expected hue range: [0, 360)
// expected saturation range: [0, 1]
// expected lightness range: [0, 1]
module.exports = function(hue, saturation, lightness){
  // based on algorithm from http://en.wikipedia.org/wiki/HSL_and_HSV#Converting_to_RGB
  if( hue == undefined ){
    return [0, 0, 0];
  }

  var chroma = (1 - Math.abs((2 * lightness) - 1)) * saturation;
  var huePrime = hue / 60;
  var secondComponent = chroma * (1 - Math.abs((huePrime % 2) - 1));

  huePrime = Math.floor(huePrime);
  var red;
  var green;
  var blue;

  if( huePrime === 0 ){
    red = chroma;
    green = secondComponent;
    blue = 0;
  }else if( huePrime === 1 ){
    red = secondComponent;
    green = chroma;
    blue = 0;
  }else if( huePrime === 2 ){
    red = 0;
    green = chroma;
    blue = secondComponent;
  }else if( huePrime === 3 ){
    red = 0;
    green = secondComponent;
    blue = chroma;
  }else if( huePrime === 4 ){
    red = secondComponent;
    green = 0;
    blue = chroma;
  }else if( huePrime === 5 ){
    red = chroma;
    green = 0;
    blue = secondComponent;
  }

  var lightnessAdjustment = lightness - (chroma / 2);
  red += lightnessAdjustment;
  green += lightnessAdjustment;
  blue += lightnessAdjustment;

  return [Math.round(red * 255), Math.round(green * 255), Math.round(blue * 255)];

};