[Insight-users] Sorting watershed basins based on size

[Luis Ibanez]

Hi Remi,

It sounds like you could simply compute the Histogram
of the labeled image.

The histogram will give you the number of pixels assigned
to each one of the labels, and since the labels are unique,
you will get the number of pixels on each watersed basin.

You will find details on the use of the ITK histogram
in the Statistics chapter of the SoftwareGuide.

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

Section 9.1.3, pdf-page 320

The associated example is available in

    Insight/Examples/Statistics/Histogram.cxx

In the same chapter you will find options for sorting.



Regards,


    Luis


-------------------------------
SERIOT Rémi DEC/SPUA/LTEC wrote:
> Hi,
> 
> I would like to sort watershed basins based on size, so I need to calculate
> the size of each basin from the labeled image. I need to do that and I don't
> wont to re-invent something already done.
> I think that I could use a simple ImageIterator and an accumulator for
> compute the number of pixels in each basin from the labeled image and then
> sort this list for keep only the most significant basins.
> 
> Could I speed it up this process with
> itk::watershed::Segmenter::flat_region_t information ?
> 
> Or there is another way to do the same thing ?
> 
> After that could I have to change the EquivalencyTable ?
> 
> Thanks for your help
>  
> Rémi
> 
> 
>>-----Message d'origine-----
>>De : Joshua Cates [mailto:cates at sci . utah . edu]
>>Envoyé : vendredi 13 juin 2003 18:05
>>À : SERIOT Rémi DEC/SPUA/LTEC
>>Cc : 'insight-users at public . kitware . com'
>>Objet : RE: [Insight-users] How to create my own 
>>NeighborhoodOperator ?
>>
>>
>>Hi Rémi,
>>
>>Glad to hear the NeighborhoodOperator is working out.
>>
>>In order to sort and merge watershed basins based on size you 
>>will have to
>>modify the itkWatershedSegmenter algorithm to keep track of 
>>basin sizes.  
>>The initial size would need to be computed in the gradient 
>>descent step of
>>itkWatershedSegmenter and then updated and maintained during 
>>basin merge
>>operations.
>>
>>An alternate approach of a one-time suppression of small basins in the
>>initial output might be interesting (but will result in a different
>>algorithm and I can't guarantee you won't get some 
>>undesirable grouping of
>>basins).  You could calculate the basin sizes from the the initial
>>segmentation (zero merge level output) of the 
>>WatershedSegmenter and then
>>use some of the existing code for basin merges (in
>>itkWatershedSegmentTreeGenerator, for example) to pre-merge 
>>the smaller
>>basins in the segment tree.
>>
>>Josh.
>>______________________________
>> Josh Cates			
>> School of Computer Science	
>> University of Utah
>> Email: cates at sci . utah . edu
>> Phone: (801) 587-7697
>> URL:   http://www . sci . utah . edu/~cates
>>
> 
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