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Using fourier plug-in with GIMP

I would like to use the new fourier plug-in with Gimp, and I have no idea how to make it work.

I am using Windows 7 64 bit, and all versions of Gimp seem to install and work properly on my computer. But whichever one I have installed, when I click to run the downloaded fourier plug-in from, I always get an error message (which differ in their details depending on the version of Gimp installed).

I have some old screened illustrations in printed books that I want to work with, and altho I get usable results using Gausian blur followed by unsharpe mask, I am wonder whether the fourier filter will give better results.

The G' MIC Spectral Handling tool works fine for me, but what are the extra five data-sets below the first fft? I gather that they have something to do with the RGB channels. Anyone?

Yes, actually, the FFT transform is a float-valued transform, so if one wants to avoid loosing to much informations, you need to store all the float-valued numbers of the transform (to be able to compute the inverse transform accurately for instance). As GIMP is only able to manage images with 8bits/pixel (so integers in [0,255]), the float-valued FFT of an image cannot be stored easily without some 'hacks'. One of the hack used by the G'MIC plug-in is then to convert the float numbers of the FFT into fixed-point numbers (32bits), and append these informations as several images.
What you see on the top is in fact the most-significant part of the FFT (so the classical log-magnitude image), while all the others are the lowest-significant data. They are indeed useful to invert the FFT process accurately. Probably, you shouldn't want to modify it !

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