src/ImboClient/Http/ImageUrl.php
public function level($amount = 1, $channel = null) {
        $params = array('amount=' . $amount);

        if ($channel) {
            $params[] = 'channel=' . $channel;
        }

        return $this->addTransformation('level:' . implode(',', $params));
    }
public function level($amount = 1, $channel = null) {
        $params = array('amount=' . $amount);

        if ($channel) {
            $params[] = 'channel=' . $channel;
        }

        return $this->addTransformation('level:' . implode(',', $params));
    }
public function level ( $ amount = 1 , $ channel = null ) { $ params = array ( 'amount=' . $ amount ) ; if ( $ channel ) { $ params [ ] = 'channel=' . $ channel ; } return $ this -> addTransformation ( 'level:' . implode ( ',' , $ params ) ) ; }
Add a level transformation to the image, adjusting the levels of an image

@param int $amount Amount to adjust, on a scale from -100 to 100
@param string $channel Optional channel to adjust. Possible values:
r, g, b, c, m, y, k - can be combined to adjust multiple.
@return self
Add a level transformation to the image adjusting the levels of an image