Server-side image transforms in Python 04 Dec 2009
miscellaneous software development python

While working at Slide, I became enamored with the concept of cooperative threads (coroutines) and the in-house library built around greenlet to implement coroutines for Python. As an engineer on the “server team” I had the joy of working in a coro-environment on a daily basis but now that I’m “out” I’ve had to find an alternative library to give me coroutines: eventlet. Interestingly enough, eventlet shares common ancestry with Slide’s internal coroutine implementation like two different species separated thousands of years ago by continental drift (a story for another day).

A few weekends ago, I had a coroutine itch to scratch one afternoon: an eventlet-based image server for applying transforms/filters/etc. After playing around for a couple hours “PILServ” started to come together. One of the key features I wanted to have in my little image server project was the ability to not only pass the server a URL of an image instead of a local path but also to “chain” transforms in a jQuery-esque style. Using segments of the URL as arguments, a user can arbitrarily chain arguments into PILServ, i.e.:

http://localhost:8080/flip/filter(blur)/rotate(45)/resize(64x64)/<url to an image>

At the end of the evening I spent on PILServ, I had something going that likely shows off more of the skills of PIL rather than eventlet itself but I still think it’s neat. Below is a sample of some images transformed by PILServ running locally: