As it turns out, it’s really not as complicated as some people say. Assuming you’ve already got macports and rubygems installed, it basically comes down to this:
sudo port install freetype
sudo port install ghostscript
sudo port install imagemagick
#sudo port install graphicsmagick
sudo gem install rmagick
Somewhere I got the idea to also install graphicsmagick after imagemagick, but for some reason port doesn’t seem to be able to find the package; It tries a few dozen sites and fails, so I commented it out above, but feel free to try it yourself. But no matter, it seems to not be necessary; I can now create images, render text, write them to disk, etc.
On Ubuntu (6.10), the incantation is different, but even simpler (via EXPRESSICA:
sudo apt-get install imagemagick
sudo apt-get install libmagick9-dev ruby1.8-dev
sudo gem install rmagick
The only caveat is that if you’re running without swap space and have less than a couple hundred megs of free RAM (e.g. on a VPS server) you may need to stop some of your processes before attempting that last line, or you’ll get this not-so-helpful set of errors after it runs for a while, consumes all available RAM, and subsequently crashes:
Building native extensions. This could take a while…
ERROR: While executing gem … (Gem::Installer::ExtensionBuildError)
ERROR: Failed to build gem native extension.
Hopefully this will save someone a few hours.