While I wait for a specific version of Xcode to download because the computer I'm using has no Mac OS X 10.6 SDKs anymore (thank you so much Apple), here is a post about the code of my plugin!
I've hosted my code in a repository on GitHub, but kept it private. The link is now public, and you can access the terribad coding at http://github.com/caitelatte/caitessegonal. I make version control repositories for most of my code-based assignments, so that I can track what I've been doing. It's been particularly useful for figuring out the stuff with compatibility between versions of Mac OS (thanks again Apple).
Above I've included a few of the best/most important parts of my code. Everything is commented so that hopefully other people and future me can understand what's going on. I included ASCII diagrams of the concepts I'm using to calculate what colour pixels are in front of the which_shape and inside_octagon functions.
The only other file in interest in the repository is the Makefile, which is all kinds of broken (I love Apple so much). I've included a screen shot of it.