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Imagick::autoLevelImage — Description
$CHANNEL = Imagick::CHANNEL_DEFAULT
  ] )Adjusts the levels of a particular image channel by scaling the minimum and maximum values to the full quantum range.
CHANNELWhich channel should the auto-levelling should be done on.
Example #1 Imagick::autoLevelImage()
<?php
function autoLevelImage($imagePath) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->autoLevelImage();
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}
?>