Saving from 24-bit to 256 color bitmap (HELP!)

[ef2k]

I can't find a way to do this ANYWHERE! No API code or anything, no controls, no nothing! I want to save a 256-color bitmap from a 24-bit bitmap. I've deduced that this will require some dithering of some sort most likely...any hlep appreciated! Thank you guys for all your help in the past!
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