I'm not completely sure about what exactly it is that youre looking for but have you thought of checking out a script directory to find something that may already exist to do what youre looking to accomplish? I used to use scripts.com but recently got hooked on
www.codango.com for web programming related stuff.
Anyway, I think you may find something somewhat relevant in the graphics area...theres some categories of image editors and stuff too, i'm not entirely sure what you want but if it exists you may find it here...
http://codango.com/php/dir/components/graphics/
From my understanding of what you want to do - PHP is probably the best bet as anyone visiting your site will be able to properly view the charts with no other little worries. It stinks to have to buy some hosting space, but on the brightside PHP hosting is cheap and even better - your users should all view it problem free than
Good luck!
