I already did that : the solution I choose was wM to send data to a PHP website thru web services.
It’s working very well and it’s used on daily basis on production w/o troubles.
Alternatively, you can think using SVG as suggested by other participants, or better, HTML5’s canvas if your users are using decent browsers (ms-IE excluded) : They are both texts based so a simple JAVA service can generate graphics as complex as you want.
Side note : for a future evolution of my application, I’m thinking of using Canvas but still thru PHP. The design is better as ISes are only focusing on businesses whereas graphics generation, users interfaces and such satellite activities are externalized on this PHP web site.