Posted by
Jan-Peter Urbach on
Sep 05, 2006; 3:22pm
URL: http://imagej.273.s1.nabble.com/FFT-bandpass-filter-exact-meaning-of-low-and-high-pass-thresshold-tp3701667p3701669.html
Yes, I did.
The only hint about the size of the filtering :
...
Filters out large structures (shading correction) and small structures
(smoothing) of the specified size by gaussian filtering in fourier
space.
...
does not seem to answer my question or am I missing something?
JP
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Dr. Jan-Peter Urbach
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-----Original Message-----
From: ImageJ Interest Group [mailto:
[hidden email]] On Behalf Of H.
Gluender
Sent: Tuesday, September 05, 2006 4:16 PM
To:
[hidden email]
Subject: Re: FFT-bandpass filter: exact meaning of low- and high-pass
thresshold
>Hello,
>I am just starting to use ImageJ for Image analysis and I am really
>impressed by the various functionalities.
>Particularily I want to convolute images with a defined convolution
kernel.
>This is where I have my question:
>To my understanding a convolution with a gaussian kernel can be
>accomplished by the Process -> FFT -> Bandpass Filter menu.
>There you can input the thresholds for large and small structures to be
>filtered out.
>My question: What exactly do those number mean? Or more precisly the
>function effectivly performs a convolution of the image in real space
>with a gaussian kernel of a given size (well actually two kernels one
>for the large and one for the small structures).
>What is the relationship between the threshold you enter in the menu
>and the size of the gaussian kernel in real space.
>For example is it the FWHM (full width half max) or is it the standard
>deviation of a normalized gaussian distribution?
>
>Thanks in advance for any hints
>Jan-Peter
Did you look at
<
http://rsb.info.nih.gov/ij/plugins/fft-filter.html>
as recommended in the ImageJ-manual?
Best
--
Herbie
------------------------
<
http://www.gluender.de>