Plugin system

How would you write a plugin system for an image-processing application where one plugin is "dependant" on another plugin? For example I have an histogram plugin who has to call the grayscale plugin before showing the histogram. I could hard-code the grayscale function but it's ugly and I would have to do the same for a lot of other plugins.

I'm writing this in Qt (Trolltech) and C++, and I use the QLibrary object (not that it really matters...)

>>21
After a bit of thought I'm inclined to agree with you. The compiler handles the stack instead, and even though >>19 clearly has no idea what he's talking about, he did get one thing right: you can initialize plugins as you return, which isn't as elegant with iteration.