[Insight-users] Obtaining shape information from a region

[Luis Ibanez]

Hi Aster,

There are filters that will extract the pixels from
the boundary and set them on in an outptu image:

SimpleContourExtractorImageFiler
http://www.itk.org/Insight/Doxygen/html/classitk_1_1SimpleContourExtractorImageFilter.html

You can also use the BinaryMaskToNarrowBandImageFilter
that will return you a PointSet with all the points
that are located at a selected distance from the edge
of your segmented object.
http://www.itk.org/Insight/Doxygen/html/classitk_1_1BinaryMaskToNarrowBandPointSetFilter.html


However, I would strongly discurage you from encoding
the information of your segmentation in a simple list
of points, because you will lose all the connectivity
information, which is very expensive to recover from
just a cloud of points.


Of course, it all depends on what is your final goal....


If you are looking for a Mesh representation of your
object, then you should consider to include not only
the points (locations of pixels as returned by the
IndexToPhysicalPoint() method in the itk::Image), but
also the neighborhood information.


You may want to read the "Data Representation" Chapter
from the ITK Software Guide:

   http://www.itk.org/ItkSoftwareGuide.pdf


in order to get familiar with the mechanisms for
representing Meshes.



   Regards



      Luis




------------------------------
Aster.Wardhani at csiro.au wrote:
> Hi Luis,
> 
> After I extract a region say using region growing, I'd like to store points that belong to the region's boundary and also points that belong to the internal region's areas. Does that make sense? Does the filter provide a method to return a list of points? Or do I need to do manually interate all pixels in the output image then push each pixel as a point into a list ?
> 
> Thanks,
> 
> Aster.
> 
> -----Original Message-----
> From:	Luis Ibanez [mailto:luis.ibanez at kitware.com]
> Sent:	Tue 8/23/2005 9:09 AM
> To:	Wardhani, Aster (ICT Centre, e-Health Res Centre)
> Cc:	insight-users at itk.org
> Subject:	Re: [Insight-users] Obtaining shape information from a region
> 
> Hi Aster,
> 
> I'm afraid that you question is too vague in
> order for us to give you any useful feedback.
> 
> Shape analysis is a wide field and you should
> usually start by framing the goal/purpose of
> your shape analysis task.
> 
> Maybe a description of the context of your problem
> would help....
> 
> 
>    Regards,
> 
> 
> 
>      Luis
> 
> 
> -------------------------------
> Aster.Wardhani at csiro.au wrote:
> 
>>Hi,
>>
>>I’ve just done some segmentation using connected component filter 
>>(region grow with a seed point). What’s the best way to analyse the 
>>shape of the region, i.e getting:
>>
>>-       its boundary
>>-       points that belong to the region.
>>
>>
>>------------------------------------------------------------------------
>>
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> 
> 
> 
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