Filtry na obrazki z Instagrama

Witam serdecznie,
Znalazłem na stronie: https://code.tutsplus.com/tutorials/create-instagram-filters-with-php--net-24504

Fajny skrypt do nakładania filtrów na obrazki (instagramowe):

 
error_reporting(ALL);
//phpinfo();
 
class Instagraph 
{
     
    public $_image = NULL;
    public $_output = NULL;
    public $_prefix = 'IMG';
    private $_width = NULL;
    private $_height = NULL;
    private $_tmp = NULL;
         
    public static function factory($image, $output)
    {
        return new Instagraph($image, $output);
    }
         
    public function __construct($image, $output)
    {
        if(file_exists($image))
        {
            $this->_image = $image;
            list($this->_width, $this->_height) = getimagesize($image);
            $this->_output = $output;
        }
        else
        {
            throw new Exception('File not found. Aborting.');
        }
    }
 
    public function tempfile()
    {
        # copy original file and assign temporary name
        $this->_tmp = $this->_prefix.rand();
        copy($this->_image, $this->_tmp);
    }
     
    public function output()
    {
        # rename working temporary file to output filename
        rename($this->_tmp, $this->_output);
    }
 
    public function execute($command)
    {
        # remove newlines and convert single quotes to double to prevent errors
        $command = str_replace(array("\n", "'"), array('', '"'), $command);
        $command = escapeshellcmd($command);
        # execute convert program
        exec($command);
    }
     
    /** ACTIONS */
     
    public function colortone($input, $color, $level, $type = 0)
    {
        $args[0] = $level;
        $args[1] = 100 - $level;
        $negate = $type == 0? '-negate': '';
 
        $this->execute("convert 
        {$input} 
        ( -clone 0 -fill '$color' -colorize 100% ) 
        ( -clone 0 -colorspace gray $negate ) 
        -compose blend -define compose:args=$args[0],$args[1] -composite 
        {$input}");
    }
 
    public function border($input, $color = 'black', $width = 20)
    {
        $this->execute("convert $input -bordercolor $color -border {$width}x{$width} $input");
    }
 
    public function frame($input, $frame)
    {
        $this->execute("convert $input ( '$frame' -resize {$this->_width}x{$this->_height}! -unsharp 1.5×1.0+1.5+0.02 ) -flatten $input");
    }
     
    public function vignette($input, $color_1 = 'none', $color_2 = 'black', $crop_factor = 1.5)
    {
        $crop_x = floor($this->_width * $crop_factor);
        $crop_y = floor($this->_height * $crop_factor);
         
        $this->execute("convert 
        ( {$input} ) 
        ( -size {$crop_x}x{$crop_y} 
        radial-gradient:$color_1-$color_2
        -gravity center -crop {$this->_width}x{$this->_height}+0+0 +repage )
        -compose multiply -flatten 
        {$input}");   
    }
     
    /** RESERVED FOR FILTER METHODS */
     
}



try
{
$instagraph = Instagraph::factory('input.jpg', 'output.jpg');
}
catch (Exception $e) 
{
    echo $e->getMessage();
    die;
}
  
// loop through all filters
 
foreach(array('gotham', 'toaster', 'nashville', 'lomo', 'kelvin') as $method)
{
    $instagraph->_output = $method.'.jpg'; // we have to change output file to prevent overwrite
    $instagraph->$method(); // apply current filter (from array)
}

Na serwerze mam zainstalowane zarówno GD jak i ImageMagick.

Po uruchomieniu skryptu na ekranie nic się nie dzieje (mam biały ekran) - bez błędów itp.
Zdjęcia także się nie generują :( Wie ktoś może dlaczego tak się dzieje?