Get color brightness (from hexa)

getBrightness.js

export default function getBrightness(c) {
    var c = c.substring(1)      // strip #
    var rgb = parseInt(c, 16)   // convert rrggbb to decimal
    var r = (rgb >> 16) & 0xff  // extract red
    var g = (rgb >>  8) & 0xff  // extract green
    var b = (rgb >>  0) & 0xff  // extract blue

    var luma = (r * 299 + g * 587 + b * 114) / 1000

    return luma
}