Bertrand Le Roy shows off how to create dynamic images leveraging WPF's image manipulation classes in an ASP.Net project instead of GDI+ classes to dramatically reduce creation time.
His prior post on this topic actually shows how to create them and why it is so fast. It also shows off different algorithms and their outputs with benchmarks. Some algorithms may produce great images but if they are slow, in certain cases, they can't be used.
Bertrand's method does work in a Medium Trust environment but be aware of how your processing stuff. This may not be a solution for you.
[via This week on Channel 9]