color-string.js

/* MIT license */
var colorNames = require('color-name');

module.exports = {
   getRgba: getRgba,
   getHsla: getHsla,
   getRgb: getRgb,
   getHsl: getHsl,
   getHwb: getHwb,
   getAlpha: getAlpha,

   hexString: hexString,
   rgbString: rgbString,
   rgbaString: rgbaString,
   percentString: percentString,
   percentaString: percentaString,
   hslString: hslString,
   hslaString: hslaString,
   hwbString: hwbString,
   keyword: keyword
}

function getRgba(string) {
   if (!string) {
      return;
   }
   var abbr =  /^#([a-fA-F0-9]{3})$/,
       hex =  /^#([a-fA-F0-9]{6})$/,
       rgba = /^rgba?\(\s*([+-]?\d+)\s*,\s*([+-]?\d+)\s*,\s*([+-]?\d+)\s*(?:,\s*([+-]?[\d\.]+)\s*)?\)$/,
       per = /^rgba?\(\s*([+-]?[\d\.]+)\%\s*,\s*([+-]?[\d\.]+)\%\s*,\s*([+-]?[\d\.]+)\%\s*(?:,\s*([+-]?[\d\.]+)\s*)?\)$/,
       keyword = /(\D+)/;

   var rgb = [0, 0, 0],
       a = 1,
       match = string.match(abbr);
   if (match) {
      match = match[1];
      for (var i = 0; i < rgb.length; i++) {
         rgb[i] = parseInt(match[i] + match[i], 16);
      }
   }
   else if (match = string.match(hex)) {
      match = match[1];
      for (var i = 0; i < rgb.length; i++) {
         rgb[i] = parseInt(match.slice(i * 2, i * 2 + 2), 16);
      }
   }
   else if (match = string.match(rgba)) {
      for (var i = 0; i < rgb.length; i++) {
         rgb[i] = parseInt(match[i + 1]);
      }
      a = parseFloat(match[4]);
   }
   else if (match = string.match(per)) {
      for (var i = 0; i < rgb.length; i++) {
         rgb[i] = Math.round(parseFloat(match[i + 1]) * 2.55);
      }
      a = parseFloat(match[4]);
   }
   else if (match = string.match(keyword)) {
      if (match[1] == "transparent") {
         return [0, 0, 0, 0];
      }
      rgb = colorNames[match[1]];
      if (!rgb) {
         return;
      }
   }

   for (var i = 0; i < rgb.length; i++) {
      rgb[i] = scale(rgb[i], 0, 255);
   }
   if (!a && a != 0) {
      a = 1;
   }
   else {
      a = scale(a, 0, 1);
   }
   rgb[3] = a;
   return rgb;
}

function getHsla(string) {
   if (!string) {
      return;
   }
   var hsl = /^hsla?\(\s*([+-]?\d*[\.]?\d+)(?:deg)?\s*,\s*([+-]?[\d\.]+)%\s*,\s*([+-]?[\d\.]+)%\s*(?:,\s*([+-]?[\d\.]+)\s*)?\)/;
   var match = string.match(hsl);
   if (match) {
      var alpha = parseFloat(match[4]);
      var h = ((parseFloat(match[1]) % 360) + 360) % 360,
          s = scale(parseFloat(match[2]), 0, 100),
          l = scale(parseFloat(match[3]), 0, 100),
          a = scale(isNaN(alpha) ? 1 : alpha, 0, 1);
      return [h, s, l, a];
   }
}

function getHwb(string) {
   if (!string) {
      return;
   }
   var hwb = /^hwb\(\s*([+-]?\d*[\.]?\d+)(?:deg)?\s*,\s*([+-]?[\d\.]+)%\s*,\s*([+-]?[\d\.]+)%\s*(?:,\s*([+-]?[\d\.]+)\s*)?\)/;
   var match = string.match(hwb);
   if (match) {
      var alpha = parseFloat(match[4]);
      var h = ((parseFloat(match[1]) % 360) + 360) % 360,
          w = scale(parseFloat(match[2]), 0, 100),
          b = scale(parseFloat(match[3]), 0, 100),
          a = scale(isNaN(alpha) ? 1 : alpha, 0, 1);
      return [h, w, b, a];
   }
}

function getRgb(string) {
   var rgba = getRgba(string);
   return rgba && rgba.slice(0, 3);
}

function getHsl(string) {
  var hsla = getHsla(string);
  return hsla && hsla.slice(0, 3);
}

function getAlpha(string) {
   var vals = getRgba(string);
   if (vals) {
      return vals[3];
   }
   else if (vals = getHsla(string)) {
      return vals[3];
   }
   else if (vals = getHwb(string)) {
      return vals[3];
   }
}

// generators
function hexString(rgb) {
   return "#" + hexDouble(rgb[0]) + hexDouble(rgb[1])
              + hexDouble(rgb[2]);
}

function rgbString(rgba, alpha) {
   if (alpha < 1 || (rgba[3] && rgba[3] < 1)) {
      return rgbaString(rgba, alpha);
   }
   return "rgb(" + rgba[0] + ", " + rgba[1] + ", " + rgba[2] + ")";
}

function rgbaString(rgba, alpha) {
   if (alpha === undefined) {
      alpha = (rgba[3] !== undefined ? rgba[3] : 1);
   }
   return "rgba(" + rgba[0] + ", " + rgba[1] + ", " + rgba[2]
           + ", " + alpha + ")";
}

function percentString(rgba, alpha) {
   if (alpha < 1 || (rgba[3] && rgba[3] < 1)) {
      return percentaString(rgba, alpha);
   }
   var r = Math.round(rgba[0]/255 * 100),
       g = Math.round(rgba[1]/255 * 100),
       b = Math.round(rgba[2]/255 * 100);

   return "rgb(" + r + "%, " + g + "%, " + b + "%)";
}

function percentaString(rgba, alpha) {
   var r = Math.round(rgba[0]/255 * 100),
       g = Math.round(rgba[1]/255 * 100),
       b = Math.round(rgba[2]/255 * 100);
   return "rgba(" + r + "%, " + g + "%, " + b + "%, " + (alpha || rgba[3] || 1) + ")";
}

function hslString(hsla, alpha) {
   if (alpha < 1 || (hsla[3] && hsla[3] < 1)) {
      return hslaString(hsla, alpha);
   }
   return "hsl(" + hsla[0] + ", " + hsla[1] + "%, " + hsla[2] + "%)";
}

function hslaString(hsla, alpha) {
   if (alpha === undefined) {
      alpha = (hsla[3] !== undefined ? hsla[3] : 1);
   }
   return "hsla(" + hsla[0] + ", " + hsla[1] + "%, " + hsla[2] + "%, "
           + alpha + ")";
}

// hwb is a bit different than rgb(a) & hsl(a) since there is no alpha specific syntax
// (hwb have alpha optional & 1 is default value)
function hwbString(hwb, alpha) {
   if (alpha === undefined) {
      alpha = (hwb[3] !== undefined ? hwb[3] : 1);
   }
   return "hwb(" + hwb[0] + ", " + hwb[1] + "%, " + hwb[2] + "%"
           + (alpha !== undefined && alpha !== 1 ? ", " + alpha : "") + ")";
}

function keyword(rgb) {
  return reverseNames[rgb.slice(0, 3)];
}

// helpers
function scale(num, min, max) {
   return Math.min(Math.max(min, num), max);
}

function hexDouble(num) {
  var str = num.toString(16).toUpperCase();
  return (str.length < 2) ? "0" + str : str;
}


//create a list of reverse color names
var reverseNames = {};
for (var name in colorNames) {
   reverseNames[colorNames[name]] = name;
}