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Is the fft2 output mirrored as in the fft?

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Andrea Muratori
Andrea Muratori on 28 May 2021
Answered: Manas Meena on 31 May 2021
Hi,
I know that the fft algorithm gives a mirrored spectrum as output. Now, I'm working with the fft2 and I get a spectrum which seems to be symmetric but actually peaks has different heigths and slightly different positions.
My question: is this difference due to the double performing of the one dimensional fft (as by definition is fft2 = fft(fft(X).').' ) or the fft2 output is not symmetric as in the fft case?
Thanks

Answers (1)

Manas Meena
Manas Meena on 31 May 2021
The spectrum seems to be symmetric but if you look at the spectrum matrix values you'll see that is not the case. This is caused by the round-off error. If you want to ensure a symmetric matrix you must specify the "symmetric" option on ifft2 function.
For example,
X = ifft2(Y,'symmetric')

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