capictcha generates CAPTCHA images from
arbitrary strings. It supports the use of any
TrueType/OpenType font and an alternate (more stable) font for punctuation and other characters, and allows you to specify the size and output text, JPG or PNG graphic output, and MD5 lookups of values you don't want to expose as plain text (which could be used to give a simple text table relating email addresses to their hex MD5 hash). Individual character tweaks, overstriking, and random lines are easily configurable.
