Customizing the links around image attachments in posts

Question

Hi. I am trying to customize the links that wrap each image attached to my posts. I'm currently getting something like this:

<a href="http://www.example.com/images/uploads/2010/10/image.jpg"&gt;
    <img src="http://www.example.com/images/uploads/2010/10/image_thumb.jpg" alt="Test alt" title="image" width="630" height="541" class="alignnone size-medium wp-image-1509" />
</a>

I would like to be able to add rel and class attributes to the link element, but I can't figure out how to filter it. I'm looking at functions like wp_get_attachment_link() or wp_get_attachment_url(), but I can't figure out how to filter either of them.

Any thoughts? Thanks in advance.

Marcus