AimsImageSmoothing

AIMS library and commands usage

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guillaume
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Location: Institut des Neurosciences de la Timone
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AimsImageSmoothing

Postby guillaume » Fri Jan 23, 2009 4:53 pm

Hello everybody,

when i apply a gaussian smoothing to a volume, the resulting image shows multiple voxels at around +or- 10^ -40.
( comand : ~/SHFJ_pack-stable-linux-3.0.2/bin/AimsImageSmoothing -i myVol.ima -o myVolSmooth.ima -t 2 -s 0)


I tried to convert my volume from FLOAT to DOUBLE (this looks like a cast error), but AimsImageSmoothing doesn't take DOUBLE.
The problem already occurs with ohter version i've installed (more recent is cartopack-Fedora-4-i686-3.1.3-2008_10_01)

Don't you know what goes wrong?

thanks

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Jean-Francois Mangin
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Location: Neurospin, CEA, France
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Re: AimsImageSmoothing

Postby Jean-Francois Mangin » Mon Jan 26, 2009 1:15 pm

I do not thing anything goes wrong. As far as I am aware, this command is based
on the recursive implementation of R. Deriche, which is a very efficient way
to approximate Gaussian smoothing. Hence getting this +/- epsilon in some places
is possible if you smooth a binary image. If it is a pb for you, you can perform
some thresholding afterwards?

guillaume
Posts: 44
Joined: Wed Mar 15, 2006 10:29 am
Location: Institut des Neurosciences de la Timone
Contact:

Re: AimsImageSmoothing

Postby guillaume » Tue Jan 27, 2009 2:12 pm

Hi Jeff,
The thresholding solves this issue, but it is strange to obtain negative values by smoothing a non negative mask...
Matthieu said to me that it comes from numerical approximations, as you confirm.

Thank you!

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Jean-Francois Mangin
Posts: 337
Joined: Mon Mar 01, 2004 10:24 am
Location: Neurospin, CEA, France
Contact:

Re: AimsImageSmoothing

Postby Jean-Francois Mangin » Tue Jan 27, 2009 10:30 pm

Not so strange, if you resample an image with a cubic spline you get worse...


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