i'll just add one thing to flora's post regarding the FFT/IFFT. well, two things. first, she's right about throwing the computer out the window... most of us were close to that when we first ran into it
and two, there's an even simpler version in "Image Analyzer" which seems to work very well and that others use here. i've tried both and tend to use the RGB FFT/IFFT rather than image analyzer's, but mostly because i learned on FFT/IFFT and that's what i'm most used to. but, dont overlook image analyzer either. it has some very good things in it and, it's free.
and my welcome to
RP as well