hsv2rgb/hsv2rgb.js

convert from hsv/hsb to rgb

// based on http://www.kasperkamperman.com/blog/arduino/arduino-programming-hsb-to-rgb/
// which is based on http://www.codeproject.com/miscctrl/CPicker.asp
var TAU = Math.PI*2;
var round = Math.round;
var min = Math.min;
var max = Math.max;
var ceil = Math.ceil;
module.exports = hsv2rgb;

function set(r, g, b, out) {
  out[0] = round(r * 255);
  out[1] = round(g * 255);
  out[2] = round(b * 255);
}

function clamp(v, l, u) {
  return max(l, min(v, u));
}

function hsv2rgb(h, s, v, out) {
  out = out || [0, 0, 0];
  h = h % 360;
  s = clamp(s, 0, 1);
  v = clamp(v, 0, 1);

  // Grey
  if (!s) {
    out[0] = out[1] = out[2] = ceil(v * 255);
  } else {
    var b = ((1 - s) * v);
    var vb = v - b;
    var hm = h % 60;
    switch((h/60)|0) {
      case 0: set(v, vb * h / 60 + b, b, out); break;
      case 1: set(vb * (60 - hm) / 60 + b, v, b, out); break;
      case 2: set(b, v, vb * hm / 60 + b, out); break;
      case 3: set(b, vb * (60 - hm) / 60 + b, v, out); break;
      case 4: set(vb * hm / 60 + b, b, v, out); break;
      case 5: set(v, b, vb * (60 - hm) / 60 + b, out); break;
    }
  }
  return out;
}