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
AimsImageSmoothing
- Jean-Francois Mangin
- Posts: 337
- Joined: Mon Mar 01, 2004 10:24 am
- Location: Neurospin, CEA, France
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Re: AimsImageSmoothing
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?
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?
-
- Posts: 44
- Joined: Wed Mar 15, 2006 10:29 am
- Location: Institut des Neurosciences de la Timone
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Re: AimsImageSmoothing
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!
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!
- Jean-Francois Mangin
- Posts: 337
- Joined: Mon Mar 01, 2004 10:24 am
- Location: Neurospin, CEA, France
- Contact:
Re: AimsImageSmoothing
Not so strange, if you resample an image with a cubic spline you get worse...