The code Stefan mentioned is in an old pull request (PR #16). That PR is from before the switch from scikits.image to skimage. I've made a new branch in my git repo with the convolution code in the new namespace.

If you're already running skimage from git, then you can use git to clone this branch:

git remote -f add tonysyu git@github.com:tonysyu/scikits-image.git
git checkout -b convolution tonysyu/skimage-convolution

In case this isn't familiar: The first line adds my git repo to your list of remotes, and the "-f" flag fetches the tags from my repo (this ensures that you have the info about my branches). My repo is now added to your repo as a remote with the name "tonysyu" (you can change this). The second line creates a new branch "convolution", clones my "skimage-convolution" branch into it, and checks it out.

Hope that helps,
-Tony