Color conversion functions (RGB, HEX, HSV, HSL)

gistfile1.js

/**
 * 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].
 *
 * @return  string           The HSL representation
 * @param r
 * @param g
 * @param b
 */
const RGB2HSL => (r, g, b) {
  r /= 255, g /= 255, b /= 255;

  let max = Math.max(r, g, b), min = Math.min(r, g, b);
  let h, s, l = (max + min) / 2;

  if (max === min) {
    h = s = 0; // achromatic
  } else {
    let d = max - min;
    s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

    switch (max) {
      case r: h = (g - b) / d + (g < b ? 6 : 0); break;
      case g: h = (b - r) / d + 2; break;
      case b: h = (r - g) / d + 4; break;
    }

    h /= 6;
  }

  return `hsv(${convertColorFractionToInteger(h)}, ${convertColorFractionToInteger(s)}, ${convertColorFractionToInteger(l)})`;
}

/**
 * Converts an HSL color value to RGB. Conversion formula
 * adapted from http://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].
 *
 * @return  string           The RGB representation
 * @param h
 * @param s
 * @param l
 */
const HSL2RGB => (h, s, l) {
  let r, g, b;

  if (s === 0) {
    r = g = b = l; // achromatic
  } else {
    function hue2rgb(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;
    }

    let q = l < 0.5 ? l * (1 + s) : l + s - l * s;
    let p = 2 * l - q;

    r = hue2rgb(p, q, h + 1/3);
    g = hue2rgb(p, q, h);
    b = hue2rgb(p, q, h - 1/3);
  }

  return `rgb(${r * 255}, ${g * 255}, ${b * 255})`;
}

/**
 * Converts an RGB color value to HSV. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
 * Assumes r, g, and b are contained in the set [0, 255] and
 * returns h, s, and v in the set [0, 1].
 *
 * @return  string           The HSV representation
 * @param r
 * @param g
 * @param b
 */
const RGB2HSV => (r, g, b) {
  r /= 255, g /= 255, b /= 255;

  let max = Math.max(r, g, b), min = Math.min(r, g, b);
  let h, s, v = max;

  let d = max - min;
  s = max === 0 ? 0 : d / max;

  if (max === min) {
    h = 0; // achromatic
  } else {
    switch (max) {
      case r: h = (g - b) / d + (g < b ? 6 : 0); break;
      case g: h = (b - r) / d + 2; break;
      case b: h = (r - g) / d + 4; break;
    }

    h /= 6;
  }

  return `hsv(${convertColorFractionToInteger(h)}, ${convertColorFractionToInteger(s)}, ${convertColorFractionToInteger(v)})`;
}

/**
 * Converts an HSV color value to RGB. Conversion formula
 * adapted from http://en.wikipedia.org/wiki/HSV_color_space.
 * Assumes h, s, and v are contained in the set [0, 1] and
 * returns r, g, and b in the set [0, 255].
 *
 * @return  string           The RGB representation
 * @param h
 * @param s
 * @param v
 */
const HSV2RGB => (h, s, v) {
  let r, g, b;

  let i = Math.floor(h * 6);
  let f = h * 6 - i;
  let p = v * (1 - s);
  let q = v * (1 - f * s);
  let t = v * (1 - (1 - f) * s);

  switch (i % 6) {
    case 0: r = v, g = t, b = p; break;
    case 1: r = q, g = v, b = p; break;
    case 2: r = p, g = v, b = t; break;
    case 3: r = p, g = q, b = v; break;
    case 4: r = t, g = p, b = v; break;
    case 5: r = v, g = p, b = q; break;
  }

  return `rgb(${r * 255}, ${g * 255}, ${b * 255})`;
}

/**
 *
 * @param hex Hex String
 * @param strObj
 * @return string rgb(r, g, b) String
 */
const HEX2RGB => (hex, strObj = false) {
  let shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
  hex = hex.replace(shorthandRegex, function(m, r, g, b) {
    return r + r + g + g + b + b;
  });

  let result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
  if ( strObj ) {
    return result ? {
      r: parseInt(result[1], 16),
      g: parseInt(result[2], 16),
      b: parseInt(result[3], 16)
    } : null;
  } else {
    return result ? `rgb(${parseInt(result[1], 16)}, ${parseInt(result[2], 16)}, ${parseInt(result[3], 16)})` : null;
  }
}

/**
 *
 * @param r
 * @param g
 * @param b
 * @returns {string} hex string
 * @return {string}
 */
const RGB2HEX => (r, g, b) {
  return "#" + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
}