(PECL imagick 3 >= 3.3.0)
Imagick::autoLevelImage — Adjusts the levels of a particular image channel
Adjusts the levels of a particular image channel by scaling the minimum and maximum values to the full quantum range.
channelWhich channel should the auto-levelling should be done on.
   Restituisce true in caso di successo.
  
Example #1 Imagick::autoLevelImage()
<?php
function autoLevelImage($imagePath) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->autoLevelImage();
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?>