Contrast Correct

Contrast Correct allows you to take arbitrary colors and modify them to be increase their contrast against any background.

Color contrast is determined by the algorithm specified in WCAG 2.1 and as such processed colors will be readable even for users with color blindness.

Usage

/**
 * Load Contrast Correct with the provided hex string color helpers. This makes
 * Contrast Correct accept and return hex string colors (such as "#000").
 */
const { correctContrast, relativeLuminance } = require("contrast-correct/hex");
 
// The color of the background for our text.
const background = "#0e0c13";
 
// Calculating the corrected color.
let usernameColor = "#003";
let newUsernameColor = correctContrast(
    // Color to correct
    usernameColor,
    // Relative luminance of the text background (can and should be pre-calculated)
    relativeLuminance(background),
    // Target contrast ratio. 7.0 is recommended for text by WCAG 2.1.
    7.0
);
 
// Log the modified color. In this case "#002fd0".
console.log(newUsernameColor);

Tips

If you already have your own methods for converting hex color strings to individual channels you can instead load contrast-correct and it will instead accept and return objects in the form { r: 0.0 to 1.0, g: 0.0 to 1.0, b: 0.0 to 1.0 }.

WCAG 2.1 contrast ratios have a few gotchas. For any background it's always possible to generate a color with a contrast of around 4.58, but high contrast ratious (around 9+) are only possible on very dark or very bright backgrounds.

License

The ISC License (ISC).

Copyright (C) 2018 Tomas Heie

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.