If you are looking for a way to generate a "CAPTCHA" image for a form verification (to verify it is not a robot), have a look at this : http://blog.theoconcept.com/static/distortion/
It gives an animated image with the parameter string, with distortion, here is an example :
http://blog.theoconcept.com/static/distortion/distortion.php
(*) You'll need GD + Freetype support
(**) You'll need ImageMagick on the machine