I would like to limit the size of attachments in posts to, say, 120x120 pixels.

Just the way it works for the user-icons - they are automatically shrunk. I see how the user-icons are shrunk, in the template.

But I cannot see how to shrink the attachments in posts. The posts are called by <%post_message%>.
Do I have to go into the perl, if so, where and how?

Thanks!