node-console-colors/rgb.js

ANSI colors for your cli with no dependencies

//--------------------------------------------------------------------------
//https://stackoverflow.com/questions/2353211/hsl-to-rgb-color-conversion
/**
 * 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  {Object}          The RGB representation
 */

function hslToRgb(h, s, l) {
  h = h > 1 ? h /= 360 : h;
  s = s > 1 ? s /= 100 : s;
  l = l > 1 ? l /= 100 : 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 {
		r:Math.round(r * 255),
		g:Math.round(g * 255),
		b:Math.round(b * 255)
	};
}

//--------------------------------------------------------------------------

function rgbToHsl(r, g, b){
  r /= 255;
  g /= 255;
  b /= 255;
  const l = Math.max(r, g, b);
  const s = l - Math.min(r, g, b);
  const h = s
    ? l === r
      ? (g - b) / s
      : l === g
      ? 2 + (b - r) / s
      : 4 + (r - g) / s
    : 0;
  return {
    h: 60 * h < 0 ? 60 * h + 360 : 60 * h,
    s: 100 * (s ? (l <= 0.5 ? s / (2 * l - s) : s / (2 - (2 * l - s))) : 0),
    l: (100 * (2 * l - s)) / 2,
	};
};

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;
}

//--------------------------------------------------------------------------

export function deltaE(rgbA, rgbB) {
  let labA = rgb2lab(rgbA);
  let labB = rgb2lab(rgbB);
  let deltaL = labA[0] - labB[0];
  let deltaA = labA[1] - labB[1];
  let deltaB = labA[2] - labB[2];
  let c1 = Math.sqrt(labA[1] * labA[1] + labA[2] * labA[2]);
  let c2 = Math.sqrt(labB[1] * labB[1] + labB[2] * labB[2]);
  let deltaC = c1 - c2;
  let deltaH = deltaA * deltaA + deltaB * deltaB - deltaC * deltaC;
  deltaH = deltaH < 0 ? 0 : Math.sqrt(deltaH);
  let sc = 1.0 + 0.045 * c1;
  let sh = 1.0 + 0.015 * c1;
  let deltaLKlsl = deltaL / (1.0);
  let deltaCkcsc = deltaC / (sc);
  let deltaHkhsh = deltaH / (sh);
  let i = deltaLKlsl * deltaLKlsl + deltaCkcsc * deltaCkcsc + deltaHkhsh * deltaHkhsh;
  return i < 0 ? 0 : Math.sqrt(i);
}

//--------------------------------------------------------------------------

function rgb2lab(rgb){
  let r = rgb[0] / 255, g = rgb[1] / 255, b = rgb[2] / 255, x, y, z;
  r = (r > 0.04045) ? Math.pow((r + 0.055) / 1.055, 2.4) : r / 12.92;
  g = (g > 0.04045) ? Math.pow((g + 0.055) / 1.055, 2.4) : g / 12.92;
  b = (b > 0.04045) ? Math.pow((b + 0.055) / 1.055, 2.4) : b / 12.92;
  x = (r * 0.4124 + g * 0.3576 + b * 0.1805) / 0.95047;
  y = (r * 0.2126 + g * 0.7152 + b * 0.0722) / 1.00000;
  z = (r * 0.0193 + g * 0.1192 + b * 0.9505) / 1.08883;
  x = (x > 0.008856) ? Math.pow(x, 1/3) : (7.787 * x) + 16/116;
  y = (y > 0.008856) ? Math.pow(y, 1/3) : (7.787 * y) + 16/116;
  z = (z > 0.008856) ? Math.pow(z, 1/3) : (7.787 * z) + 16/116;
  return [(116 * y) - 16, 500 * (x - y), 200 * (y - z)]
}

//--------------------------------------------------------------------------
export const HSLtoRGB = hslToRgb;
export const RGBtoHSL = rgbToHsl;