Y = fft2(X)Y = fft2(X,m,n)
Y = fft2(X) performs the two-dimensional FFT. The result Y is the same size as X.
Y = fft2(X,m,n) either truncates X or pads X with 0s to create an m-by-n array before doing the transform. The result is m-by-n.
fft2(X) is simply
fft(fft(X).').'
This computes the one-dimensional FFT of each column X, then of each row of the result. The time required to compute fft2(X) depends strongly on the number of prime factors in [m,n] = size(X). It is fastest when m and n are powers of 2.
fft, fftshift, ifft2
(c) Copyright 1994 by The MathWorks, Inc.