protected function median(array $pixels)
{
sort($pixels, SORT_NUMERIC);
$middle = floor(count($pixels) / 2);
if (count($pixels) % 2) {
$median = $pixels[$middle];
} else {
$low = $pixels[$middle];
$high = $pixels[$middle + 1];
$median = ($low + $high) / 2;
}
return $median;
}