hsv.js

import {color, rgb} from "d3-color";

var darker = 0.7,
    brighter = 1 / darker;

function hsvConvert(o) {
  if (o instanceof Hsv) return new Hsv(o.h, o.s, o.v, o.opacity);
  if (!(o instanceof rgb)) o = rgb(o);
  var r = o.r / 255,
      g = o.g / 255,
      b = o.b / 255,
      min = Math.min(r, g, b),
      max = Math.max(r, g, b),
      d = max - min,
      h = NaN,
      s = d / max,
      v = max;
  if (d) {
    if (r === max) h = (g - b) / d + (g < b) * 6;
    else if (g === max) h = (b - r) / d + 2;
    else h = (r - g) / d + 4;
    h *= 60;
  }
  return new Hsv(h, s, v, o.opacity);
}

export default function hsv(h, s, v, opacity) {
  return arguments.length === 1 ? hsvConvert(h) : new Hsv(h, s, v, opacity == null ? 1 : opacity);
}

export function Hsv(h, s, v, opacity) {
  this.h = +h;
  this.s = +s;
  this.v = +v;
  this.opacity = +opacity;
}

var hsvPrototype = Hsv.prototype = hsv.prototype = Object.create(color.prototype);

hsvPrototype.constructor = Hsv;

hsvPrototype.brighter = function(k) {
  k = k == null ? brighter : Math.pow(brighter, k);
  return new Hsv(this.h, this.s, this.v * k, this.opacity);
};

hsvPrototype.darker = function(k) {
  k = k == null ? darker : Math.pow(darker, k);
  return new Hsv(this.h, this.s, this.v * k, this.opacity);
};

hsvPrototype.rgb = function() {
  var h = isNaN(this.h) ? 0 : this.h % 360 + (this.h < 0) * 360,
      s = isNaN(this.h) || isNaN(this.s) ? 0 : this.s,
      v = this.v,
      a = this.opacity,
      c = v * s,
      x = c * (1 - Math.abs((h / 60) % 2 - 1)),
      m = v - c;
  return h < 60 ? hsv2rgb(c, x, 0, m, a)
      : h < 120 ? hsv2rgb(x, c, 0, m, a)
      : h < 180 ? hsv2rgb(0, c, x, m, a)
      : h < 240 ? hsv2rgb(0, x, c, m, a)
      : h < 300 ? hsv2rgb(x, 0, c, m, a)
      : hsv2rgb(c, 0, x, m, a);
};

hsvPrototype.displayable = function() {
  return (0 <= this.s && this.s <= 1 || isNaN(this.s))
      && (0 <= this.v && this.v <= 1)
      && (0 <= this.opacity && this.opacity <= 1);
};

function hsv2rgb(r1, g1, b1, m, a) {
  return rgb((r1 + m) * 255, (g1 + m) * 255, (b1 + m) * 255, a);
}