BrainVISA

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

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?

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!

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