Hi,
Saad's definitions below are correct (and may "inspire" the help-text
in the next revision of avwmaths++!)
Matt
> Hi,
>
> Here is what I think the options do :
>
> -dilM : replace zero values with the mean value inside the kernel
> -dilD : replace zero values with the mode inside the kernel (mostly
> encountered value in the case of discrete values)
> -dilF : replace all values by the maximum value inside the kernel
> -ero : replace non-zero values by zero if zero is the minimum value
> inside the kernel, otherwise do nothing
> -eroF : replace all values by the minimum value inside the kernel
>
> you are right, -ero and -eroF do the same if the masked region has a
> minimum value of zero, but they do not do the same if the kernel
> doesn't contain zero.
>
> i believe that modal filtering reduces noise in the image..
>
> I hope this helps you ?
>
> saad.
>
>
> On 23 Jun 2006, at 11:27, Ged Ridgway wrote:
>
> > Hi,
> >
> > Please can someone clarify the different options for dilation and
> > erosion that avwmaths++ offers?
> >
> > -dilM : Mean Dilation of zero voxels
> > -dilD : Modal Dilation of zero voxels
> > -dilF: Maximum filtering of all voxels
> > -ero : Erode by zeroing non-zero voxels when zero voxels found in
> > kernel
> > -eroF : Minimum filtering of all voxels
> >
> > -difF and -eroF sound like the "usual" grey-scale morphological
> > operations. My interpretation of the help message is that -ero will do
> > the same as -eroF if the kernel-masked region includes zeros, but if
> > not, it will do nothing, whereas -ero will take the minimum. Is this
> > correct?
> >
> > I've not seen the terms mean and modal dilation, (and Googling "modal
> > dilation" (with quotes) returns only one hit, and it doesn't look like
> > it's about grey-level morphology...), could someone explain what they
> > do and why it might be preferable to maximum filtering (or mean/median
> > filtering if similar)?
> >
> > Many thanks,
> > Ged.
>
> ------------------------------------------------------------------------
> ---
> Saad Jbabdi,
> Postdoctoral Research Assistant,
> Oxford University FMRIB Centre
>
> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222545 (fax 222717)
> [log in to unmask] http://www.fmrib.ox.ac.uk/~saad
> ------------------------------------------------------------------------
> ---
>
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