hexislight function for the Hexadecimal Color Clock on the SSaurel's Blog

hexislight.js

function hexislight(color) {
  var hex = color.replace('#', '');
  var red = parseInt(hex.substr(0, 2), 16);
  var green = parseInt(hex.substr(2, 2), 16);
  var blue = parseInt(hex.substr(4, 2), 16);
  // it is a known formula, nothing magical here
  var brightness = ((red * 299) + (green * 587) + (blue * 114)) / 1000; 
  return brightness > 155; 
}