I remember that I saw once a product, which could do this. I think it used the PIL-library from python. I can´t find it on Zope.org. Any hints ?

I'm not sure if there is any special products, however it is quite easy to create an external python method, which uses the PIL-library to generate images. THe only tricky bit is making sure that the module is loaded correctly and then you should have a problem. Oh also make sure to set the content type correctly. Cheers, Benno