[vtkusers] VtkConnectivity filter

[Bill Lorensen]

I'm pretty sure that itk's cc algorithms are n-d.

Also, there are other benefits to linking to ITK. It has a much broader
selection of image filters and segmentation techniques.


On Tuesday, March 12, 2013, Richard Frank wrote:

> Thanks David,
>
> Yes, I looked at the threshold connectivity filter and noticed the
> required seeds.
>
> I have some 2d connected components/union find code that I will try to
> reimplement  for 3d.
>
> I just wanted to see if the connectivity filter would do what I want, and
> it does seem to....
>
> Do you happen to know if ITK has a general cc region find in n dimensions?
> We may want to link our app at some point to make use of ITK ( in spite of
> the different image layouts).
>
> I think your class would be a good contribution VTK- it's a basic tool
> that seems to be missing....
>
> Thanks
>
> Rick Frank
>
> On Mar 12, 2013, at 7:57 AM, David Gobbi <david.gobbi at gmail.com<javascript:;>>
> wrote:
>
> > Hi Richard,
> >
> > If your data is a volume, then vtkImageThresholdConnectivity might be
> > more suitable.  It requires you to set seeds, though, and I'm not sure
> > if that's what you want.
> >
> > I also have a filter in my personal collection that selects image
> > regions based on size (rather than requiring you to set seed
> > locations) and I could potentially contribute it to VTK.  Internally
> > it computes labels for each region, up to a max of 254, and the code
> > could be modified so that it outputs the labels.
> >
> > - David
> >
> > On Tue, Mar 12, 2013 at 5:43 AM, Richard Frank <rickfrank at me.com<javascript:;>>
> wrote:
> >>
> >> I'm having trouble understanding the usages of the connectivity filter.
> >>
> >> I'm trying to use this filter to find and filter out regions in a
> volume, as one might do with bwlabeln() in matlab....
> >>
> >> What does AddRegion() do? Does that usage imply that I already know how
> many regions there are? Why/when would I use DeleteRegion()?
> >>
> >>
> >> If I ask for all regions, I get the whole volume even if I set a tight
> scalar threshold. If I ask for the largest region, I get what I would
> expect,  but that's not what I need.
> >>
> >> If I set specific regions, and add 0,1,2 and use a threshold that I
> know should work, I get nothing.
> >>
> >> So, I guess I don't understand the correct use.
> >>
> >> Any advice welcome.....
> >>
> >>
> >> Thanks
> >> Rick Frank
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