Python users who use Django or Google App Engine on the Mac, will likely benefit from the python imaging library (PIL).

However, installing on Mac OS X (Snow Leopard) can be tricky. There are many blog posts on the issue. The most common problem is that PIL and libjpeg (a dependency) seem to install OK, but when you go to use it in your Python code, you get “_jpeg_resync_to_restart” errors.

A further complication is the fact that Google App Engine uses Python version 2.5 (and not the default 2.6 that comes with Snow Leopard). If you just need PIL for Django, you can ignore the 2.5 references (i.e. python2.5 becomes python).

Here’s how I got it working on my machine (the steps are a combination of others’ blog posts, but main credit goes to Michael Richardson‘s post):

1. Download the latest libjpeg .tar.gz (version v7 at time of writing): http://www.ijg.org/files/.
2. Download the latest PIL version for Python 2.5 (v1.17 at time of writing): http://www.pythonware.com/products/pil/
3. Extract libjpeg and do the standard install affair:

   export CC="gcc -arch i386"
   ./configure
   make
   sudo make install
   

   from within the directory. The first line is the gem that many other blog posts leave out (and it assumes you’re using BASH)

4. Extract the PIL and change in to that directory.
5. [optional] libjpeg will have been installed in /usr/local/lib/, by default, above. Normally this directory will be picked up automatically by the PIL install below, but just for good measure (or if you have problems later in the PIL install), edit the setup.py, look for the line

   JPEG_ROOT = None

   and change that line to

   JPEG_ROOT=libinclude( "/usr/local" )
   

   and save it.

6. Install PIL by running

   sudo python2.5 setup.py install
   

That was enough to get it running for me. I can start App Engine (I use the Google-provided launcher), and use the Image API.