Add color functions

color.js

@@ -0,0 +1,75 @@
+/**
+ * Calculate light or darker color based on the luminance arg.
+ *
+ * @param  {String} hex Color hex string to calculate on.
+ * @param  {Number} lum Luminance.
+ * @return {String}     The new color hex string.
+ */
+export const colorLuminance = (hex, lum) => {
+  // validate hex string
+  hex = String(hex).replace(/[^0-9a-f]/gi, '');
+  if (hex.length < 6) {
+    hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2];
+  }
+  lum = lum || 0;
+  // convert to decimal and change luminosity
+  let rgb = '#';
+  let c;
+  let i;
+  for (i = 0; i < 3; i++) {
+    c = parseInt(hex.substr(i * 2, 2), 16);
+    c = Math.round(Math.min(Math.max(0, c + (c * lum)), 255)).toString(16);
+    rgb += ('00' + c).substr(c.length);
+  }
+
+  return rgb;
+}
+
+/**
+ * Calculate an appropriate contrast color.
+ *
+ * @param  {String} hex   Hex string of the color we're searching for the right contrast.
+ * @param  {String} dark  Dark color to return. Defaults to #000000.
+ * @param  {String} light Light color to return. Defaults to #ffffff.
+ * @return {String}       Hex color string with the appropriate contrast color.
+ */
+export const contrastTextColor = (hex, dark, light) => {
+  dark = dark || '#000000';
+  light = light || '#ffffff';
+  const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
+  if (!result) {
+    return dark;
+  }
+  const red = parseInt(result[1], 16);
+  const green = parseInt(result[2], 16);
+  const blue = parseInt(result[3], 16);
+  let brightness;
+  brightness = (red * 299) + (green * 587) + (blue * 114);
+  brightness /= 255000;
+  // values range from 0 to 1
+  // anything greater than 0.6 should be bright enough for dark text
+  if (brightness >= 0.6) {
+    return dark;
+  }
+
+  return light;
+}
+
+/**
+ * Convert rgb(r, g, b) to hex.
+ *
+ * @param  {String} rgb   Rgb string to convert.
+ * @return {String}       The hex string.
+ */
+export const rgbToHex = rgb => {
+  const matches = rgb.match(/rgb\(([0-9]+), ([0-9]+), ([0-9]+)\)/);
+  if (matches.length !== 4) {
+    return '';
+  }
+
+  // From https://gist.github.com/lrvick/2080648.
+  const bin = matches[1] << 16 | matches[2] << 8 | matches[3];
+  return (function(h) {
+    return '#' + new Array(7 - h.length).join('0') + h;
+  })(bin.toString(16).toLowerCase());
+}

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@tp/helpers",
-  "version": "2.4.0",
+  "version": "2.5.0",
   "description": "",
   "main": "closest.js",
   "scripts": {