getbrightness

getBrightness

This is a mini module to get the Rec.601 Luma value of a given hex colour. But that sounds boring and not useful, so instead it's called getBrightness which sounds more useful.

This function takes a hex string (or hex number) and returns a number between 0 and 1, which can identify if a colour is "dark" or "light". A dark-ish colour is likely to have a value of 0.5 or less, while a light-ish colour will likely have a value of 0.5 or more.

You might use this to determine if a foreground text color should be white or black given a random hex colour. For example:

import getBrightness from 'getbrightness'
randomBackground = el => {
  const hex = '#' + Math.floor(Math.random()*16777215).toString(16);
  el.style.backgroundColor = hex
  // Should the foreground be black or white? Let's ask getBrightness!
  el.style.color = getBrightness(hex) > 0.6 ? 'black' : 'white'
}