add support for alpha channel (#2)

sindresorhus · Nov 4, 2016 · c638bbd · c638bbd
1 parent 19cb8cf
commit c638bbd
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Showing 4 changed files with 42 additions and 5 deletions.
diff --git a/index.js b/index.js
@@ -1,12 +1,17 @@
 'use strict';
 /* eslint-disable no-mixed-operators */
-module.exports = (red, green, blue) => {
+module.exports = (red, green, blue, alpha) => {
+	const isPercent = (red + (alpha || '')).toString().includes('%');
+
 	if (typeof red === 'string') {
-		const res = red.match(/\b\d{1,3}\b/g).map(Number);
+		const res = red.match(/(0?\.?\d{1,3})%?\b/g).map(Number);
 		// TODO: use destructuring when targeting Node.js 6
 		red = res[0];
 		green = res[1];
 		blue = res[2];
+		alpha = res[3];
+	} else if (alpha !== undefined) {
+		alpha = parseFloat(alpha);
 	}
 
 	if (typeof red !== 'number' ||
@@ -18,5 +23,18 @@ module.exports = (red, green, blue) => {
 		throw new TypeError('Expected three numbers below 256');
 	}
 
-	return ((blue | green << 8 | red << 16) | 1 << 24).toString(16).slice(1);
+	if (typeof alpha === 'number') {
+		if (!isPercent && alpha >= 0 && alpha <= 1) {
+			alpha = Math.round(255 * alpha);
+		} else if (isPercent && alpha >= 0 && alpha <= 100) {
+			alpha = Math.round(255 * alpha / 100);
+		} else {
+			throw new TypeError(`Expected alpha value (${alpha}) as a fraction or percentage`);
+		}
+		alpha = (alpha | 1 << 8).toString(16).slice(1);
+	} else {
+		alpha = '';
+	}
+
+	return ((blue | green << 8 | red << 16) | 1 << 24).toString(16).slice(1) + alpha;
 };
diff --git a/package.json b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "rgb-hex",
   "version": "2.0.0",
-  "description": "Convert RGB color to HEX",
+  "description": "Convert RGB(A) color to HEX",
   "license": "MIT",
   "repository": "sindresorhus/rgb-hex",
   "author": {

diff --git a/readme.md b/readme.md
@@ -1,6 +1,6 @@
 # rgb-hex [![Build Status](https://travis-ci.org/sindresorhus/rgb-hex.svg?branch=master)](https://travis-ci.org/sindresorhus/rgb-hex)
 
-> Convert RGB color to HEX
+> Convert RGB(A) color to HEX
 
 
 ## Install
@@ -20,6 +20,15 @@ rgbHex(65, 131, 196);
 
 rgbHex('rgb(40, 42, 54)');
 //=> '282a36'
+
+rgbHex(65, 131, 196, 0.2);
+//=> '4183c433'
+
+rgbHex(40, 42, 54, '75%');
+//=> '282a36c0'
+
+rgbHex('rgba(40, 42, 54, 75%)');
+//=> '282a36c0'
 ```
 
 

diff --git a/test.js b/test.js
@@ -6,4 +6,14 @@ test(t => {
 	t.is(m(65, 131, 196), '4183c4');
 	t.is(m('255 154 253'), 'ff9afd');
 	t.is(m('rgb(40, 42, 54)'), '282a36');
+	t.is(m(0, 0, 0, 0), '00000000');
+	t.is(m(0, 0, 0, 0.5), '00000080');
+	t.is(m(0, 0, 0, '50%'), '00000080');
+	t.is(m(0, 0, 0, '100%'), '000000ff');
+	t.is(m(65, 131, 196, 0.2), '4183c433');
+	t.is(m('255 154 253, 0.8'), 'ff9afdcc');
+	t.is(m('160 82 45 .4'), 'a0522d66');
+	t.is(m(40, 42, 54, 0.75), '282a36bf');
+	t.is(m(40, 42, 54, '75%'), '282a36bf');
+	t.is(m('rgba(40, 42, 54, 75%)'), '282a36bf');
 });