[Insight-users] label object manipulation

[Gaëtan Lehmann]

Le 29 juin 09 à 23:31, lynx.abraxas at freenet.de a écrit :

> Dear Gaëtan Lehmann,
>
>
> Thanks  a  lot  for You quick answer. With Your hints it was easy to  
> extend my
> little program to suit my needs further.
> I'm wondering though if the article is the best documentation to  
> work with.  I
> couldn't   find   the   Perimeter   attribute   only   
> EquivalentPerimeter  and
> EquivalentEllipsoidPerimeter. The connectivity is also only  
> mentioned  in  the
> examples.  Is there another documentation where these are explained  
> and that I
> should read before asking here?
>

No, there is no other document, but you can look at the source! All  
the attributes are listed in

   http://voxel.jouy.inra.fr/darcs/contrib-itk/binaryAttributeMorphology/itkShapeLabelObject.h
   http://voxel.jouy.inra.fr/darcs/contrib-itk/binaryAttributeMorphology/itkStatisticsLabelObject.h

And you're right, I forgot to put the perimeter in the attribute list.  
I'll try to fix that in a next revision.

> In the footnote it says there'll be more about perimeter estimation  
> in another
> article. Is that published already?
>

No, not yet.

> I  noticed  that GetEquivalentEllipsoidSize yields nan/inf if the  
> bounding box
> is only 1 pixel wide. When I used the image moments of Avizo to  
> calculate  the
> axes lengths a bounding box width of 1 pixel wasn't a problem. I'm  
> not sure if
> this result from Avizo is good but with my current understanding a   
> full  axis
> length of 1 (or 0.5 for a semi axis) would be sensible, wouldn't it?

I have this problem also, and it's quite annoying. It's caused by an  
approximation in the moment computations: the voxel thickness is not  
used.
The formulae I used are very common, and I didn't find an easy way to  
include it. In http://insight-journal.com/browse/publication/301 ,  
this information is used, but unfortunately, the spacing is not.
Also, I don't think that putting 1 (or 1/2) axis if the size is 0 on  
this axis would be nice, because it would make the result quite  
different of the case where there the size is very thin but not zero.  
Something like

    0000000000000000000000000000

and

    0000000000000000000000000000
           0


> If  it's not possible to calculate that, would it be possible to get  
> an output
> letting the filter assume only 2D for these objects?


I would prefer getting a non-approximated formulae for the moment  
computation which take care of the spacing. I'm quite sure it's not  
that complicated, but, well, that's not my field of competences.

If someone has some documentation, or has the needed knowledge on that  
point, I would really appreciate some help!

Gaëtan




-- 
Gaëtan Lehmann
Biologie du Développement et de la Reproduction
INRA de Jouy-en-Josas (France)
tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
http://voxel.jouy.inra.fr  http://www.itk.org
http://www.mandriva.org  http://www.bepo.fr

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