[Insight-users] FFT

[Luis Ibanez]

Hi Alexandre,


     It is *impossible* to try it all  :-)


You may have tried many combinations,...

and
certainly enough of them for generating frustration.


     So... let's start from the beginning


Take a deep breath and give us real technical
information that we could use.



1) You seem to have tried with the Circle.png file.
    Did you used the command that I suggested in my
    previous email ?:

     FFTImageFilter.exe
       Insight/Examples/Data/Circle.png
       circleReal.mhd
       circleImg.mhd

2) If it didn't work, then please tell us
    How do you arrive to the conclusion that
    it is not working.


    a) Did it crashed ?
    b) Did it throw an exception ?
    c) Did it produced an empty image ?

    From your description it seems that it
    is running and producing a:

          "The same results:
           one level of grey scale"

     which lead us to think that what you
     may have is a visualization issue.

     The FFT of a medical image will be typically
     an image full of zeros, with a few non-zero
     values concentrated in the corners.

     What are you using for visualizing the
     output images ?

     What file format are you using for storing
     the output image ?

     As an example of the correct output,
     I'm attaching to this email the files

            circleReal.png
            circleImg.png

     Please take a look at them and let us
     know if they look like the ones you get.


3) For the record:

     Yes, you can convert your DICOM images
     to PNG. but that's not the right solution
     for your problem in this case. The input
     file format, should be irrelevant here,
     *as long* as you are declaring your image
     to be of the correct pixel type.

     Tell us more about your DICOM image:

      - What is the image modality ?
      - What is the Dimension ? (2D or 3D)
      - How many pixels on each dimension ?



    Thanks


       Luis


--------------------------
alexandre govignon wrote:
> i have done everything... s
> o it's impossible with DICOM image? I think it's the reason why i am
> not successful.
> 
> I have tried all. The same results: one level of grey scale.
> 
> But when i try with other type of image (circle .png), it still doesn't work
> 
> The question is:
> 
> Can i convert a DICOM to a png and a png to a DICOM?
> 
> Do you think i can compute by my own a FFT on a DICOM image, thanks to
> the developper's guide?
> 
> 
> 
> 2008/4/3, Luis Ibanez <luis.ibanez at kitware.com>:
> 
>> Hi Alexandre,
>>
>>
>> 0) The fact that the image is being read
>>   from a DICOM file format is irrelevant
>>   for the purpose of computing an FFT.
>>
>>
>> 1) Have you enabled FFTW ?
>>
>>
>> 2) Have you run the examples:
>>
>>   Insight/Examples/Filtering/
>>     FFTDirectInverse.cxx
>>     FFTDirectInverse2.cxx
>>     FFTImageFilter.cxx
>>
>>
>> 3) In particular have you tried the following ?
>>
>> FFTImageFilter.exe
>>   Insight/Examples/Data/Circle.png circleReal.mhd
>>circleImg.mhd
>>
>>
>>
>> Please let us know,
>>
>>
>>   Thanks
>>
>>
>>      Luis
>>
>>
>> ------------------------
>>
>> alexandre govignon wrote:
>>
>>
>>>I would like to know if there is people who have succeed in fft with
>>>ITK, because, i try a lot of things, but i think that it's really
>>>impossible to make the FFT of a DICOM image in ITK...
>>>
>>>
>>
> 
>