Color brightness rgb

color-brightness.php

<?php
function color_brightness($hex) {
 $hex = str_replace('#', '', $hex);
 $strl = strlen($hex)/3;

 $c_r = hexdec(substr($hex, 0, $strl));
 $c_g = hexdec(substr($hex, $strl, $strl));
 $c_b = hexdec(substr($hex, $strl*2, $strl));

 $brightness = (($c_r * 299) + ($c_g * 587) + ($c_b * 114)) / 1000;
}

$color = "#000"; 
$brightness = color_brightness($color);

if ( $brightness > 130 ) {
    echo 'bright';
} else {
    echo 'dark';
}
?>

<div style="height:100px;width:100px;background:<?php echo $color; ?>"></div>