gray-percentage

Convenience function to get a gray value by percentage e.g. gray(60) -> "hsla(0,0%,100%, 0.4)"

The function takes a required "lightness" value from 0-100 and an optional second parameter to mixin color to the gray value. The second parameter can either be a "hue" value from 0-360 or one of three named hues, "cool", "slate", and "warm".

As suggested by Google Material Design we color lightness using opacity instead of gray values. Quoting Google: "Black or white text that is transparent remains legible and vibrant against background color changes. This makes it more flexible than grey text in the same contexts."

We assume when picking the opacity/lightness that the background is light. If, for example, you have dark background with light text, set the third paramter, darkBackground to true e.g. gray(80, 0, true).

We use color theory to choose an appropriate saturation value. Basically the darker the gray, the higher the saturation value that is choosen. This article was very helpful in picking appropriate saturation values http://ianstormtaylor.com/design-tip-never-use-black/

The following is the curve that choose saturation values and is used here in the code.

Install

npm install gray-percentage

Usage

var gray = require('gray-percentage');

var textColor = gray(30);
// textColor = "hsla(0,0%,100%,0.7)"

// Get a "cool" gray.
var background = gray(93, "cool")
// background = "hsla(237,0.9935851860000025%,100%,0.07)"

// Mixin arbitrary hues e.g. Red.
var sidebarBg = gray(15, 360)
// sidebarBg = "hsla(360,14.84301465%,100%,0.85)"

// Get color for dark background
var lightGray = gray(85, 0, true)
// lightGray = "hsla(0, 0%, 100%, 0.85)"