Generates full, unscrambled Fourier moduli from complex
Fourier transform on disk for 2-D or 3-D pictures.
The input 2D image can be real if it fits into the memory.
Operations supports multiple radix FFT, thus the input
image does not have to have power-of-two dimensions
(see 'FT').
The resulting data are real and can be displayed like
a normal picture.