Re: Leeres FFT Image erzeugen

Posted by Thomas Boudier-2 on Dec 15, 2006; 10:09am
URL: http://imagej.273.s1.nabble.com/Leeres-FFT-Image-erzeugen-tp3700819p3700822.html

Christophe CHAMOT a écrit :

> Johannes Schindelin a écrit :
>> Hi,
>>
>> On Wed, 13 Dec 2006, Maja Temerinac wrote:
>>  
>> Since I _am_ fluent in German, and this is an English-only mailing
>> list, I will just translate here:
>>
>> "My problem: I have to FFT images, and need to create just one by
>> taking the maximum of both FFT images. I did that by using
>> 'Process->Image Calculator...' with the 'MAX' operation. When I tried
>> to apply the inverse transformation ('Process->FFT->InverseFFT') it
>> failed with 'Frequency domain image required', though. Help?"
>>
>> Dear Maja, as Kriss pointed out, you can use the image calculator
>> without creating a new image, keeping the information FHT needs.
>>
>> Alternatively, I _think_ that renaming the resulting ("MAX") image to
>> "FHT of result" and _then_ applying the inverse FFT should work (I
>> get that impression from reading the source; unfortunately I do not
>> have a means to test right now).
>>
>> Hth,
>> Dscho
>>  
> Hi Johannes,
>
> And thanks for the translation ;-)
>
> Just as a new clue about what Maja said, I tried to duplicate an
> foreward FFT image (no more angular informations when you pass the
> mouse on the duplicated image) then rename with "FHT of blabla..." and
> you were right. The inverse FFT can be performed but the result is a
> noisy 32bits image (original was a 8bits Lena).
>
> Any idea ?

Hi Kriss,

The pb is that half of the FFT information is hidden (only the power
spectrum is displayed but the "phase" is missing). So u need all the
information, that can be done using the FHT, so select the option FHT in
FFT option, a new FHT window will be created, that u can duplicate,
modify if u know what you're doing.... (u can use swap quadrants for a
more normal view).

hope this helps

a+

Thomas
>
> Thanks in advance.
>
> Kriss
>
>
>


--
/*****************************************************/
 Thomas Boudier, MCU Université Pierre et Marie Curie
 Imagerie Intégrative,Institut Curie - INSERM U759.
 Tél : [phone]  Fax : [phone]
/*****************************************************/