MATLAB: Problem with ifftn and ifftshift?

fftnfftshiftifftnifftshift

Hi there I was wondering if someone could help me. I am using the fftn fftshift functions as part of my alogrithm;

tmp = fftn(MAT); Adash = fftshift(tmp);

 Adashup=ifftshift(Adash);
 Adashup2new = ifftn(Adashup);

However, When I took everything else out and left these in as a tester I noticed that instead of the above taking me back to the original MAT, it alters the numbers quite a lot. What am I doing wrong?? Example original file MAT has a min of 0 and a max of 1.0856, however the file Adashup2new has a min of -6.792 and a max of 1.0856

Best Answer

Sounds like Imaginary components are there due to round off errors, try extracting the real part

f = real(ifft2(F));

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MATLAB: IFFT of a Hanning windowed FFT Image

Hello,

You have used your absolute values to plot your image. Now, to reverse the operation you need the full fft results which is a complex matrix for regenerating your input image. Otherwise, you get something else!

Each fft component has value and phase. You shouldn't ignore the phase component which is ignored when you only use absolute values.

This is what you should do:

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Hope it helps,

Mona

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