CodeIgniter image cropping - image not affected by crop() parameters

I have this model to crop the user's image

function crop_avatar()
{
    $id = $this->tank_auth->get_user_id();

    //get current avatar
    $query = $this->db->get_where('user_profiles', array('id' => $id));
    foreach ($query->result() as $row) {
        $j[$row->avatar] = $row->avatar;
    }

    $config['image_library'] = 'gd';
    $config['source_image'] = '.' . substr("$row->avatar", 18);
    $config['x_axis'] = '10';
    $config['y_axis']开发者_如何转开发 = '60';
    $this->load->library('image_lib');      
    $this->image_lib->initialize($config); 

    if ( ! $this->image_lib->crop())
    {
        echo $this->image_lib->display_errors();
    }

//      print_r($config);


}

which generates this array (via print_r)

Array
(
    [image_library] => gd
    [source_image] => ./images/avatars/b0b623057.jpg
    [x_axis] => 10
    [y_axis] => 60
)

For some reason unknown to me - there's no cropping going on. The original image passes straight thru this model, and is unchanged.

I do have GD on my server -- any ideas what might be wrong here?

Thanks a ton.

---

You need to define the width and height you want your image to be cropped at.

The x_axis and y_axis config values are the point in your existing image where the crop should start.

To put it another way, you need 4 measurements to crop the image : where to start vertically (y_axis), where to start horizontally (x_axis), where to end vertically (height) and where to end horizontally (width)

If one of the dimensions of your cropped image is the same as that of your original image, don't forget to set maintain_ratio to false