Posted by
Kenneth R Sloan on
URL: http://imagej.273.s1.nabble.com/FFT-implementation-in-ImageJ-tp5008239p5008243.html
As always with _Numerical Recipes_, use the code with caution. The code is
explicitly intended as a *starting point*. You should also read the WORDS
in the chapter, and consider extending and hardening the sample code.
Also, if you can find it, my experience is that the C version of _NR_ is
distinctly WORSE than the original ForTran for many algorithms (I have not
checked the FFT code to see if this trend holds here). When I use _NR_ algorithms,
I always start with the original.
And…while I appreciate the reasons, it seems (to me) wrong to claim to “compute the
FFT via the FHT”. Truth in advertising, please. Most of the time, “close” is good enough.
But, not always.
I think ImageJ would be improved by offering both the FFT *and* the FHT, with appropriate
(and correct) documentation.
--
Kenneth Sloan
[hidden email]<mailto:
[hidden email]>
"La lutte elle-même vers les sommets suffit à remplir un coeur d'homme; il faut imaginer Sisyphe heureux."
On Jun 16, 2014, at 13:37 , Curtis Rueden <
[hidden email]<mailto:
[hidden email]>> wrote:
Hi Herbie & Mariam,
You may also have a look at the code in "Numerical Recipes". However, you
have to change the C code to Java, which is rather easy.
Note that Numerical Recipes code is released under a very restrictive
license. Specifically: redistribution is prohibited. So if you are
producing open source software, you will need to stay away from it.
Regards,
Curtis
On Mon, Jun 16, 2014 at 12:16 PM, Herbie <
[hidden email]<mailto:
[hidden email]>> wrote:
Mariam,
ImageJ computes the 2D FFT via the 2D FHT.
The resulting transforms (Fourier-spectra) are essentially the same as
with a (direct) "classical" 2D FFT implementation. However the computation
is faster.
There is a plugin called FFTJ which is based on "classical 2D" FFT
implementation. The source code is available.
You may also have a look at the code in "Numerical Recipes". However, you
have to change the C code to Java, which is rather easy.
HTH
Herbie
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On 16.06.14 18:58, Student1 wrote:
Hi,
I was wondering if ImageJ has standard FFT algorithm? Because I know
ImageJ has a FFT window and it also FHT window, so does the FFT
implementation based on the FHT algorithm? When I look into the code
I basically see the FHT implementation but not a standard FFT
algorithm.
Thanks.
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