ci中的图像裁剪中的疑惑

gflhx

$config['image_library'] = 'imagemagick';
$config['library_path'] = '/usr/X11R6/bin/';//这里应该怎么写?
$config['source_image'] = '/path/to/image/mypic.jpg';//已经改成自己的图片路径
$config['x_axis'] = '100';//已经从前台得到
$config['y_axis'] = '60';//已经从前台得到
$this->image_lib->initialize($config);
if ( ! $this->image_lib->crop())
{
    echo $this->image_lib->display_errors();
}

手册中这样写的!可是
$config['library_path'] = '/usr/X11R6/bin/';//这里应该怎么写?