ASCIIMathML
ASCIIMathML.js (ver 2.0): Translates ASCII math notation to MathML and graphics. It is lightweight and has wonderful capabilities.
Take a look at:
Math:
http://www1.chapman.edu/~jipsen/mathml/asciimath.html
Graphics:
http://mathcs.chapman.edu/~jipsen/math/index.php/ASCIIMathML/ASCIIMathGraphs.html
There is a plugin for pmWiki at
http://www.pmwiki.org/wiki/Cookbook/ASCIIMath which may be helpful in developing the DokuWiki plugin. It seems it can be used the same way jsMath plugin works in DokuWiki, but it needs further tunings to work for graphics.
Cheers
Atronoush