algorithm - HSL 到 RGB 颜色转换

Question

我正在寻找一种在 HSL 颜色与 RGB 之间转换的算法。

在我看来，HSL 的使用并不是很广泛，因此我在寻找转换器方面运气不佳。

Answer 1

Garry Tan 在 his blog 上发布了 JavaScript 解决方案(他将其归因于现已不复存在的 mjijackson.com、but is archived here 和 the original author has a gist - 感谢 user2441511)。

代码重新发布如下(针对 ES5 后的约定进行更新):

HSL 到 RGB:

const { abs, min, max, round } = Math;

/**
 * Converts an HSL color value to RGB. Conversion formula
 * adapted from https://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes h, s, and l are contained in the set [0, 1] and
 * returns r, g, and b in the set [0, 255].
 *
 * @param   {number}  h       The hue
 * @param   {number}  s       The saturation
 * @param   {number}  l       The lightness
 * @return  {Array}           The RGB representation
 */
function hslToRgb(h, s, l) {
  let r, g, b;

  if (s === 0) {
    r = g = b = l; // achromatic
  } else {
    const q = l < 0.5 ? l * (1 + s) : l + s - l * s;
    const p = 2 * l - q;
    r = hueToRgb(p, q, h + 1/3);
    g = hueToRgb(p, q, h);
    b = hueToRgb(p, q, h - 1/3);
  }

  return [round(r * 255), round(g * 255), round(b * 255)];
}

function hueToRgb(p, q, t) {
  if (t < 0) t += 1;
  if (t > 1) t -= 1;
  if (t < 1/6) return p + (q - p) * 6 * t;
  if (t < 1/2) return q;
  if (t < 2/3) return p + (q - p) * (2/3 - t) * 6;
  return p;
}

##RGB 到 HSL:

/**
 * Converts an RGB color value to HSL. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSL_color_space.
 * Assumes r, g, and b are contained in the set [0, 255] and
 * returns h, s, and l in the set [0, 1].
 *
 * @param   {number}  r       The red color value
 * @param   {number}  g       The green color value
 * @param   {number}  b       The blue color value
 * @return  {Array}           The HSL representation
 */
function rgbToHsl(r, g, b) {
  (r /= 255), (g /= 255), (b /= 255);
  const vmax = max(r, g, b), vmin = min(r, g, b);
  let h, s, l = (vmax + vmin) / 2;

  if (vmax === vmin) {
    return [0, 0, l]; // achromatic
  }

  const d = vmax - vmin;
  s = l > 0.5 ? d / (2 - vmax - vmin) : d / (vmax + vmin);
  if (vmax === r) h = (g - b) / d + (g < b ? 6 : 0);
  if (vmax === g) h = (b - r) / d + 2;
  if (vmax === b) h = (r - g) / d + 4;
  h /= 6;

  return [h, s, l];
}