color.js

function rgbIntsOfHexadecimalColor(hex){
    if (hex.indexOf('#') === 0) {
        hex = hex.slice(1);
    }
    // convert 3-digit hex to 6-digits.
    if (hex.length === 3) {
        hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2];
    }
    if (hex.length !== 6) {
        throw new Error('Invalid HEX color.' + hex);
    }
    var r = parseInt(hex.slice(0, 2), 16),
        g = parseInt(hex.slice(2, 4), 16),
        b = parseInt(hex.slice(4, 6), 16);
    return [r, g, b];
}

function invertColor(hex, bw) {
    var [r, g, b] = rgbIntsOfHexadecimalColor(hex);
    if (bw) {
        // http://stackoverflow.com/a/3943023/112731
        return (r * 0.299 + g * 0.587 + b * 0.114) > 186
            ? '#000000'
            : '#FFFFFF';
    }
    // invert color components
    r = (255 - r).toString(16);
    g = (255 - g).toString(16);
    b = (255 - b).toString(16);
    // pad each with zeros and return
    return "#" + padZero(r) + padZero(g) + padZero(b);
}

function getIntColor(num) {
  var moddedNumber = num % 0x1000000; // Only 6 hex digits needed
  var flooredNumber = Math.floor(moddedNumber); // Just in case?
  return "#" + padZero(moddedNumber.toString(16), 6);
}

function generateDeterministicColor(constantProperties, rngSettings) {
  var scale = constantProperties[0];
  var seedString = JSON.stringify(constantProperties);
  var tempRNG = new RNG(seedString);
  // The prng should make different colors based on scale
  var randomIterations = rngSettings.minimumIterations + 
    Math.abs(scale*2-(scale<0 ? 1 : 0));
  var randomNumber = 0;
  for(var i = 0; i < randomIterations; i++){
    randomNumber = (
      (tempRNG.nextByte() << 16) | 
      (tempRNG.nextByte() << 8) | 
      (tempRNG.nextByte() & 0xFF)
    );
  }
  var color = getIntColor(randomNumber);
  return color;
}

function mixColors(colorList) {
  var rNumerator = 0;
  var rDenominator = 0;
  var gNumerator = 0;
  var gDenominator = 0;
  var bNumerator = 0;
  var bDenominator = 0;
  for (var i = 0; i < colorList.length; i++) {
    var [r, g, b] = rgbIntsOfHexadecimalColor(colorList[i]);
    rNumerator += r;
    rDenominator += 1;
    gNumerator += g;
    gDenominator += 1;
    bNumerator += b;
    bDenominator += 1;
  }
  return "#" + 
    padZero(Math.round(rNumerator/rDenominator).toString(16)) + 
    padZero(Math.round(gNumerator/gDenominator).toString(16)) + 
    padZero(Math.round(bNumerator/bDenominator).toString(16))
  ;
}