function compare_brightness($a, $b) { $a_brightness = brightness($a); $b_brightness = brightness($b); if ($a_brightness == $b_brightness) { return 0; } return $a_brightness < $b_brightness ? -1 : 1; }
function invertColor($hexnum) { // to rgb $brightness = brightness(hex2rgb($hexnum)); if ($brightness > 130) { return '#000000'; } return '#ffffff'; }