[Insight-users] Where to find more info on OtsuMultipleThresholds?

[Luca Antiga]

Hi,
  I just noticed that I should also have replied to this one.
Lassi's email summarizes the meat of what there was to say.

What the method does is basically to find the thresholds (by  
performing an exhaustive search on the image histogram) that minimize  
the between-class variance, which is (in latex notation - pdf render  
attached for convenience)

\sigma^2_b = \sum_{i=1}^{N_c}{\omega_i (\mu_i - \mu)^2

where \omega_i is the class proportion, \mu_i is the class mean  
intensity and \mu is the overall mean intensity.

I hope this helps, let me know if you need more details

Luca



On Nov 14, 2009, at 10:07 PM, Lassi Paavolainen wrote:

> Hi,
>
> I'm not Luca, but this filter works as basic  
> OtsuThresholdImageFilter with a one difference that it is able to  
> divide intensities to multiple classes, not just to two classes.  
> Number of classes+1 can be set using SetNumberOfThresholds method.  
> Output of the filter is label image where pixels of class 1 are  
> marked as 0, pixels of class 2 marked as 1 and so on.
>
> There is lots of information about Otsu available. One place to  
> start is Wikipedia (http://en.wikipedia.org/wiki/Otsu's_method)  
> which includes a reference to original paper by Otsu and also a  
> reference to paper where different thresholding methods are compared.
>
> Lassi
>
> On Sat, 14 Nov 2009, Bill Lorensen wrote:
>
>> Roman,
>>
>> This class was contributed by Luca Antiga. Perhaps he can provide you
>> with a reference.
>>
>> Bill
>>
>> On Sat, Nov 14, 2009 at 6:39 AM, Roman Grothausmann
>> <roman.grothausmann at helmholtz-berlin.de> wrote:
>>> Dear mailing list members,
>>>
>>>
>>> I'm looking for filters that generate multiple thresholds/segments  
>>> (if
>>> possible without subjective judgement). I found  
>>> OtsuMultipleThresholds but
>>> cannot find more info on it than in:
>>> http://www.itk.org/Doxygen/html/classitk_1_1OtsuMultipleThresholdsImageFilter.html
>>>
>>> Shouldn't there be an insight journal article to any filter? It  
>>> would be
>>> nice if the Doxygen filter descriptions would have a link to the  
>>> insight
>>> journal article for that filter.
>>>
>>> Are there any guide lines on what automated multi-threshold filter  
>>> one
>>> should use when?
>>>
>>> Many thanks for any help.
>>> Roman
>>>
>>>
>>>
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>
> -- 
> Lassi Paavolainen, M.Sc
> PhD Student in Computer Science
> University of Jyväskylä
> Software Engineer
> BioImageXD (http://www.bioimagexd.net)
> lassi.paavolainen at jyu.fi_____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.html
>
> Please keep messages on-topic and check the ITK FAQ at:
> http://www.itk.org/Wiki/ITK_FAQ
>
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--
Luca Antiga, PhD
Head, Medical Imaging Unit,
Biomedical Engineering Department,
Mario Negri Institute.
mail: Villa Camozzi, 24020, Ranica (BG), Italy
phone: +39 035 4535-381
email: antiga at marionegri.it
web: http://villacamozzi.marionegri.it/~luca

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