[Insight-users] Forward + Inverse FFT != Identity transform

[Jordi Inglada]

Dear Stefan, all,

Has there been a proposed solution to this problem? We are having 
similar problems : the FFT of a sinusoidal surface has not the expected 
shape (see the real, imaginary, and module parts of the FFT). We have 
used the FFTImageFilter.cxx example.

Thanks for any advice.

J. Inglada

group at spellgen.com wrote:

> Trying to debug a convolution routine for two images based on Fourier
> transforms, I find that a forward FFT immediately followed by its 
> inverse does
> not produce the image I started with. The code looks straightforward 
> enough -
> it does the following:
> 1. Read the image from a grayscale char-type file
> 2. Resample to width and height both being powers of two.
> 3. Forward transform (float)
> 4. Another forward transform.
> 5. Flip data in both dimensions
> 6. Rescale to bring it into char range again
> 7 Write the image.
>
> urls for the input (black with a white dot at the origin) and the output
> images:
> http://neuromagnetics.mc.vanderbilt.edu/out/itk/point.png
> http://neuromagnetics.mc.vanderbilt.edu/out/itk/out.png
>
> The source code is there as well:
> http://neuromagnetics.mc.vanderbilt.edu/out/itk/four2-example.cxx
>
> Any suggestions as to what is going on would be appreciated...
>
> Cheers,
>
> Stefan
>
>
>
> _______________________________________________
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> Insight-users at itk.org
> http://www.itk.org/mailman/listinfo/insight-users
>


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