Add 2D Butterworth

[altunenes]

I can add the Butterworth filter if you think it may be useful. I frequently use this filter in my research field...

B low is the filter response (Butterworth)
D(u,v) represents the distance from the origin in the frequency domain.
D_0 is the cutoff frequency
n is the order of the filter.

ref: Sonka, M., Hlavac, V.,, Boyle, R. (1998). Image Processing: Analysis and Machine Vision. CL-Engineering. ISBN: 053495393X

[altunenes]

the question is should I implement only the filter or full implementation (I mean 1- converting the 2D image to the frequency domain 2 applying the filter 3- then converting back to an image to get the output image)