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Thinking About Colors

  1. const { assign } = Object
  2. const { min, max, floor, round, abs } = Math
  3.  
  4. // `hslToRgb` and `rgbToHsl` functions from the amazing Raphael library
  5. // by Dmitry Baranovskiy
  6. // https://github.com/DmitryBaranovskiy/raphael/blob/master/raphael.js
  7.  
  8. export function hslToRgb({ h, s, l, a }) {
  9.   let H = h
  10.   let S = s
  11.   let L = l
  12.  
  13.   s /= 100
  14.   l /= 100
  15.  
  16.   let r, g, b, x, c
  17.   h = (h % 360) / 60
  18.   c = 2 * s * (l < .5 ? l : 1 - l)
  19.   x = c * (1 - abs(h % 2 - 1))
  20.   r = g = b = l - c / 2;
  21.   h = floor(h)
  22.   r += [c, x, 0, 0, x, c][h]
  23.   g += [x, c, c, x, 0, 0][h]
  24.   b += [0, 0, x, c, c, x][h]
  25.   r *= 255; g *= 255; b *= 255
  26.   r = round(r)
  27.   g = round(g)
  28.   b = round(b)
  29.   return { r, g, b, h: H, s: S, l: L, a }
  30. }
  31.  
  32. export function rgbToHsl({ r, g, b, a }) {
  33.   let R = r
  34.   let G = g
  35.   let B = b
  36.  
  37.   r /= 255
  38.   g /= 255
  39.   b /= 255
  40.  
  41.   let h, s, l, w, m, c;
  42.   w = max(r, g, b);
  43.   m = min(r, g, b);
  44.   c = w - m;
  45.   h = (c == 0 ? null :
  46.         w == r ? (g - b) / c :
  47.         w == g ? (b - r) / c + 2 :
  48.                  (r - g) / c + 4)
  49.   h = ((h + 360) % 6) * 60 / 360;
  50.  
  51.   l = (w + m) / 2;
  52.   s = (c == 0 ? 0 : l < .5 ?
  53.     c / (2 * l) :
  54.     c / (2 - 2 * l));
  55.   h *= 360
  56.   s *= 100
  57.   l *= 100
  58.   h = round(h)
  59.   s = round(s)
  60.   l = round(l);
  61.   return { h, s, l, r: R, g: G, b: B, a }
  62. }
  63.  
  64. const fromDec = dec => ({
  65.   r: dec >> 16,
  66.   g: dec >> 8 & 255,
  67.   b: dec & 255
  68. })
  69.  
  70. const fromHex = hex =>
  71.   fromDec(Number('0x' + hex.slice(1)))
  72.  
  73. const components = def =>
  74.   def.match(/[0-9\.]+/g).map(parseFloat)
  75.  
  76. const fromRgb = rgb => {
  77.   const [r, g, b, a] = components(rgb)
  78.   return { r, g, b, a: a ?? 1 }
  79. }
  80.  
  81. const fromHsl = hsl => {
  82.   const [h, s, l, a] = components(hsl)
  83.   return { h, s, l, a: a ?? 1 }
  84. }
  85.  
  86. const utils = {
  87.   hex: (def, o) => assign(o, rgbToHsl(
  88.     fromHex(def)), { a: o.a ?? 1 }
  89.   ),
  90.   rgb: (def, o) => assign(o, rgbToHsl(fromRgb(def))),
  91.   hsl: (def, o) => assign(o, hslToRgb(fromHsl(def))),
  92.   prop: (def, o) => {
  93.     const name = Object.keys(def)[0]
  94.     o[name] = def[name]
  95.     if (name.match(/[rgb]/)) assign(o, rgbToHsl(o))
  96.     if (name.match(/[hsl]/)) assign(o, hslToRgb(o))
  97.  
  98.     return o
  99.   }
  100. }
  101.  
  102. const types = { '#': 'hex', r: 'rgb', h: 'hsl', '[': 'prop' }
  103. const type = str => types[str[0]]
  104.  
  105. const hx = c => {
  106.   const chan = (+c).toString(16)
  107.   if (chan.length === 0) return '00'
  108.   if (chan.length === 1) return '0' + chan
  109.   return chan
  110. };
  111.  
  112. export function shade(def) {
  113.   const o = {
  114.     set(def) {
  115.       const method = utils[type(String(def))]
  116.       if (method != null) method(def, o)
  117.     },
  118.     hsl: _ => `hsla(${o.h}, ${o.s}%, ${o.l}%, ${o.a})`,
  119.     rgb: _ => `rgba(${o.r}, ${o.g}, ${o.b}, ${o.a})`,
  120.     hex: _ => `#${hx(o.r)}${hx(o.g)}${hx(o.b)}`
  121.   }
  122.   o.set(def)
  123.   return o;
  124. }

Wrote this today for something at work… it’s not done yet but figured it was worth a post… will probably post finished version tomorrow…

This can be a little golfed since it is just a demo for work and not code on a real product 😀

snippet.zone ~ 2021-22 /// {s/z}