Simple Captcha is as it's name points out is probably the simplest captcha plugin out there. It's a little old and not really updated these days (although there is some SimpleCaptcha3 activity) but still working as expected, at least on Rails 2.
Now, I know there's creatures among us developers who don't really prefer
RMagick, which is the core brick of the plugin. Some popular image related "magick" plugins give us alternative options, probably the most common
MiniMagick. Besides the usual reasons against
RMagickI do found one crucial to be JRuby compatibility. There's an attempt to fix this called
RMagick4Jbut it seems to be incomplete (at least for simple captcha it did not play correctly).
Turns out for captcha generation,
MiniMagickain't an option, it misses support for creating images from scratch which is essential. Fortunately, there's still hope thanks to
QuickMagick, well that's about enough magick isn't it ?! Sure is, but it's worth it.
QuickMagickmixes the simplicity of
MiniMagickwith the flexibility of
RMagick(and works with JRuby).
Enough chit-chat, here's how to enjoy the simplest captcha plugin for Rails without
The updated plugin lives at http://github.com/kares/simple_captcha.
UPDATE: The latest plugin version now works on Rails 3.0.0+ !