Create a hexadecimal colour based on a string with JavaScript

user_312962 0
Viewed 149770

I want to create a function that will accept any old string (will usually be a single word) and from that somehow generate a hexadecimal value between #000000 and #FFFFFF, so I can use it as a colour for a HTML element.

Maybe even a shorthand hex value (e.g: #FFF) if that's less complicated. In fact, a colour from a 'web-safe' palette would be ideal.

hex colors javascript string
17 Answers

Here is my 2021 version with Reduce Function and HSL Color.

function getBackgroundColor(stringInput) {
    let stringUniqueHash = [...stringInput].reduce((acc, char) => {
        return char.charCodeAt(0) + ((acc << 5) - acc);
    }, 0);
    return `hsl(${stringUniqueHash % 360}, 95%, 35%)`;
}
user_10351040

If your inputs are not different enough for a simple hash to use the entire color spectrum, you can use a seeded random number generator instead of a hash function.

I'm using the color coder from Joe Freeman's answer, and David Bau's seeded random number generator.

function stringToColour(str) {
    Math.seedrandom(str);
    var rand = Math.random() * Math.pow(255,3);
    Math.seedrandom(); // don't leave a non-random seed in the generator
    for (var i = 0, colour = "#"; i < 3; colour += ("00" + ((rand >> i++ * 8) & 0xFF).toString(16)).slice(-2));
    return colour;
}
user_3995430

Javascript Solution inspired by Aslam's solution but returns a color in hex color code

/**
 * 
 * @param {String} - stringInput - 'xyz'
 * @returns {String} - color in hex color code - '#ae6204'
 */
function getBackgroundColor(stringInput) {
    const h = [...stringInput].reduce((acc, char) => {
        return char.charCodeAt(0) + ((acc << 5) - acc);
    }, 0);
    const s = 95, l = 35 / 100;
    const a = s * Math.min(l, 1 - l) / 100;
    const f = n => {
        const k = (n + h / 30) % 12;
        const color = l - a * Math.max(Math.min(k - 3, 9 - k, 1), -1);
        return Math.round(255 * color).toString(16).padStart(2, '0');   // convert to Hex and prefix "0" if needed
    };
    return `#${f(0)}${f(8)}${f(4)}`;
}
user_92796820

All you really need is a good hash function. On node, I just use

const crypto = require('crypto');
function strToColor(str) {
    return '#' + crypto.createHash('md5').update(str).digest('hex').substr(0, 6);
}
user_47452390

After having a look at the rather code intensive and rather old answers, I thought I'd review this issue from a 2021 standpoint just for fun, hope it is of use to anyone. Having the HSL color model and the crypto API implemented in pretty much all browsers (except IE of course) today, it could be solved as simple as that:

async function getColor(text, minLightness = 40, maxLightness = 80, minSaturation = 30, maxSaturation = 100) {
  let hash = await window.crypto.subtle.digest("SHA-1", new TextEncoder().encode(text));
  hash = new Uint8Array(hash).join("").slice(16);

  return "hsl(" + (hash % 360) + ", " + (hash % (maxSaturation - minSaturation) + minSaturation) + "%, " + (hash % (maxLightness - minLightness) + minLightness) + "%)";
}

function generateColor() {
  getColor(document.getElementById("text-input").value).then(color => document.querySelector(".swatch").style.backgroundColor = color);
}
input {
  padding: 5px;
}

.swatch {
  margin-left: 10px;
  width: 28px;
  height: 28px;
  background-color: white;
  border: 1px solid gray;
}

.flex {
  display: flex;
}
<html>

<body>
  <div class="flex">
    <form>
      <input id="text-input" type="text" onInput="generateColor()" placeholder="Type here"></input>
    </form>
    <div class="swatch"></div>
  </div>
</body>

</html>

This should be way faster than generating hashes manually, and also offers a way to define saturation and lightness in case you don't want colors that are too flat or too bright or too dark (e.g. if you want to write text on those colors).

user_62414290

I convert this for Java.

Tanks for all.

public static int getColorFromText(String text)
    {
        if(text == null || text.length() < 1)
            return Color.BLACK;

        int hash = 0;

        for (int i = 0; i < text.length(); i++)
        {
            hash = text.charAt(i) + ((hash << 5) - hash);
        }

        int c = (hash & 0x00FFFFFF);
        c = c - 16777216;

        return c;
    }
user_68937090

I convert this in one line for Python

import hashlib

hash = hashlib.sha1(b'user@email.com').hexdigest()

print("#" + hash[0:6])
user_153446320
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