Converting a bitmap to doom image (programatically)

subject says it all, I have a bitmap object to handle all the crazy bitmap reading and stuff (ie getting pixels from x and y etc), so thats fine

the question is, how would I go about converting it to a doom image? my brain is kinda buggered at the moment, so some pascal code or pseudo code would be nice right now.

thanks Russell

oops, I guess my post would have been better in one of the other forums, sorry about that.