[ImageJ-devel] imglib2 FFT algorithm explanation

[SARA SCHIESARO]

Hi all,
I've already worked with FourierTransform and FFTConvolution classes, I've
also studied their codes in order to adapt them to my program, anyway I
still have some doubts about those classes and I hope you can help me!

First, dimensions of the output resulting from the FourierTransform and
those of the fftKernel in the FFTConvolution class differ from those of the
input images, why? Why, for example, if I transform a 256x256 image I get
back a 281x560 spectrum?

Secondly, trying to find out an answer to the first doubt I have, I find
out that the spectrum dimensions are calculated by using the package
edu.mines.jtk.dsp and in particular the classes FftReal/FftComplex, both
based on the Pfacc class. Comments to the Pfacc class said that this class
implements the PFA algorithm for the FFT computation, so my second doubt is
this: do the FourierTransform and FFTConvolution classes implement the PFA
algorithm?

I really need to find it out in order to continue my work, so any help will
be appreciated!
Thanks a lot,

Sara S.
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