index.js

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

var reverseNames = {};

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

var cs = module.exports = {
	to: {}
};

cs.get = function (string) {
	var prefix = string.substring(0, 3).toLowerCase();
	var val;
	var model;
	switch (prefix) {
		case 'hsl':
			val = cs.get.hsl(string);
			model = 'hsl';
			break;
		case 'hwb':
			val = cs.get.hwb(string);
			model = 'hwb';
			break;
		default:
			val = cs.get.rgb(string);
			model = 'rgb';
			break;
	}

	if (!val) {
		return null;
	}

	return {model: model, value: val};
};

cs.get.rgb = function (string) {
	if (!string) {
		return null;
	}

	var abbr = /^#([a-f0-9]{3,4})$/i;
	var hex = /^#([a-f0-9]{6})([a-f0-9]{2})?$/i;
	var rgba = /^rgba?\(\s*([+-]?\d+)\s*,\s*([+-]?\d+)\s*,\s*([+-]?\d+)\s*(?:,\s*([+-]?[\d\.]+)\s*)?\)$/;
	var per = /^rgba?\(\s*([+-]?[\d\.]+)\%\s*,\s*([+-]?[\d\.]+)\%\s*,\s*([+-]?[\d\.]+)\%\s*(?:,\s*([+-]?[\d\.]+)\s*)?\)$/;
	var keyword = /(\D+)/;

	var rgb = [0, 0, 0, 1];
	var match;
	var i;
	var hexAlpha;

	if (match = string.match(hex)) {
		hexAlpha = match[2];
		match = match[1];

		for (i = 0; i < 3; i++) {
			// https://jsperf.com/slice-vs-substr-vs-substring-methods-long-string/19
			var i2 = i * 2;
			rgb[i] = parseInt(match.slice(i2, i2 + 2), 16);
		}

		if (hexAlpha) {
			rgb[3] = Math.round((parseInt(hexAlpha, 16) / 255) * 100) / 100;
		}
	} else if (match = string.match(abbr)) {
		match = match[1];
		hexAlpha = match[3];

		for (i = 0; i < 3; i++) {
			rgb[i] = parseInt(match[i] + match[i], 16);
		}

		if (hexAlpha) {
			rgb[3] = Math.round((parseInt(hexAlpha + hexAlpha, 16) / 255) * 100) / 100;
		}
	} else if (match = string.match(rgba)) {
		for (i = 0; i < 3; i++) {
			rgb[i] = parseInt(match[i + 1], 0);
		}

		if (match[4]) {
			rgb[3] = parseFloat(match[4]);
		}
	} else if (match = string.match(per)) {
		for (i = 0; i < 3; i++) {
			rgb[i] = Math.round(parseFloat(match[i + 1]) * 2.55);
		}

		if (match[4]) {
			rgb[3] = 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 null;
		}

		rgb[3] = 1;

		return rgb;
	} else {
		return null;
	}

	for (i = 0; i < 3; i++) {
		rgb[i] = clamp(rgb[i], 0, 255);
	}
	rgb[3] = clamp(rgb[3], 0, 1);

	return rgb;
};

cs.get.hsl = function (string) {
	if (!string) {
		return null;
	}

	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;
		var s = clamp(parseFloat(match[2]), 0, 100);
		var l = clamp(parseFloat(match[3]), 0, 100);
		var a = clamp(isNaN(alpha) ? 1 : alpha, 0, 1);

		return [h, s, l, a];
	}

	return null;
};

cs.get.hwb = function (string) {
	if (!string) {
		return null;
	}

	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;
		var w = clamp(parseFloat(match[2]), 0, 100);
		var b = clamp(parseFloat(match[3]), 0, 100);
		var a = clamp(isNaN(alpha) ? 1 : alpha, 0, 1);
		return [h, w, b, a];
	}

	return null;
};

cs.to.hex = function () {
	var rgba = swizzle(arguments);

	return (
		'#' +
		hexDouble(rgba[0]) +
		hexDouble(rgba[1]) +
		hexDouble(rgba[2]) +
		(rgba[3] < 1
			? (hexDouble(Math.round(rgba[3] * 255)))
			: '')
	);
};

cs.to.rgb = function () {
	var rgba = swizzle(arguments);

	return rgba.length < 4 || rgba[3] === 1
		? 'rgb(' + Math.round(rgba[0]) + ', ' + Math.round(rgba[1]) + ', ' + Math.round(rgba[2]) + ')'
		: 'rgba(' + Math.round(rgba[0]) + ', ' + Math.round(rgba[1]) + ', ' + Math.round(rgba[2]) + ', ' + rgba[3] + ')';
};

cs.to.rgb.percent = function () {
	var rgba = swizzle(arguments);

	var r = Math.round(rgba[0] / 255 * 100);
	var g = Math.round(rgba[1] / 255 * 100);
	var b = Math.round(rgba[2] / 255 * 100);

	return rgba.length < 4 || rgba[3] === 1
		? 'rgb(' + r + '%, ' + g + '%, ' + b + '%)'
		: 'rgba(' + r + '%, ' + g + '%, ' + b + '%, ' + rgba[3] + ')';
};

cs.to.hsl = function () {
	var hsla = swizzle(arguments);
	return hsla.length < 4 || hsla[3] === 1
		? 'hsl(' + hsla[0] + ', ' + hsla[1] + '%, ' + hsla[2] + '%)'
		: 'hsla(' + hsla[0] + ', ' + hsla[1] + '%, ' + hsla[2] + '%, ' + hsla[3] + ')';
};

// 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)
cs.to.hwb = function () {
	var hwba = swizzle(arguments);

	var a = '';
	if (hwba.length >= 4 && hwba[3] !== 1) {
		a = ', ' + hwba[3];
	}

	return 'hwb(' + hwba[0] + ', ' + hwba[1] + '%, ' + hwba[2] + '%' + a + ')';
};

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

// helpers
function clamp(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;
}