image lib codeigniter add thumb

1$config_manip = array(
2        'image_library' => 'gd2',
3        'source_image' => $source_path,
4        'new_image' => $target_path,
5        'maintain_ratio' => TRUE,
6        'create_thumb' => TRUE,
7        'thumb_marker' => '_thumb',
8        'width' => 150,
9        'height' => 150
10    );
11    $this->load->library('image_lib', $config_manip);
12    if (!$this->image_lib->resize()) {
13        echo $this->image_lib->display_errors();
14    }
15    // clear //
16    $this->image_lib->clear();