JS - Check Brightness of Background Color.js

// Experimental : Detect background color brightness and change the font color accordingly
$(".subject-icon").each(function() {
  var isBright = (parseInt(get_brightness(rgb2hex($(this).css("background-color")))) > 160);
  if (!isBright) $(this).addClass('subject-icon-dark');
});

// Check color brightness
// returns brightness value from 0 to 255
// http://www.webmasterworld.com/forum88/9769.htm
function get_brightness(hexCode) {
  // strip off any leading #
  hexCode = hexCode.replace('#', '');

  var c_r = parseInt(hexCode.substr(0, 2),16);
  var c_g = parseInt(hexCode.substr(2, 2),16);
  var c_b = parseInt(hexCode.substr(4, 2),16);

  return ((c_r * 299) + (c_g * 587) + (c_b * 114)) / 1000;
}

// convert RGB to hex
// http://stackoverflow.com/questions/1740700/get-hex-value-rather-than-rgb-value-using-jquery
function rgb2hex(rgb) {
     if (  rgb.search("rgb") == -1 ) {
          return rgb;
     } else {
          rgb = rgb.match(/^rgba?\((\d+),\s*(\d+),\s*(\d+)(?:,\s*(\d+))?\)$/);
          function hex(x) {
               return ("0" + parseInt(x).toString(16)).slice(-2);
          }
          return "#" + hex(rgb[1]) + hex(rgb[2]) + hex(rgb[3]); 
     }
}