Programmatically setting images as thumbnails in Magento

Magento is evil. The PHP file structure is insane and confusing. Do I want to manually set 500 products' photos to thumbnails? Fuck no. Here's how to programmatically set uploaded images as a product's thumbnail, small image, and large image.

Importing products from Magento into Spree

Magento is evil. If you're working with its PHP codebase, I'm sorry. After looking for an easier, less dangerous solution, I found Spree. Easy to use, looks purty out of the box, and built on Ruby on Rails, the slow but easy web framework. And there's a Heroku extension. Awesome.

One problem: The Magento installation had 9000 products, with names, descriptions, SKUs, and other fun attributes. Spree has no built-in import or export function. Do I want to enter all this information manually? Fuck no.

After some googling, yahooing, and asking jeeves, I found a Google group discussion, took some of the example code, tailored it to the CSV format of a standard Magento export, and ended up with this ugly hack:
If you don't have the FasterCSV gem installed, install it before running this import script:
gem install fastercsv

Use the Rails runner to run this script so it has access to the database:
script/runner import.rb

and you're done.