[Insight-users] OtsuThresholdImageFilter

[Radhika Sivaramakrishna]

Hi Luis,
An OtsuMultipleThresholdImageFilter would be a great idea where we can
Pass in the input image and the number of expected thresholds, and it
will
do the whole thing and return a labeled image. Yes, so I would love to
have such a filter. 

Thanks for your suggestions on the EM model and Markov random fields.
However, I didn't understand your comment regarding the problem with the
GMM. Could you explain?

Thanks
Radhika



-----Original Message-----
From: Luis Ibanez [mailto:luis.ibanez at kitware.com] 
Sent: Thursday, October 28, 2004 9:28 AM
To: Radhika Sivaramakrishna
Cc: insight-users at itk.org
Subject: Re: [Insight-users] OtsuThresholdImageFilter


Hi Radhika,

It seems that what you want is a sort of

    OstsuMultipleThresholdImageFilter

that is, an image filter that will package
the entire operation for you. Including,
the instatntiation and computation of a
histogram, the instantiation and computation
of an OtsuMultipleThreshold Calculator and
the actual filtering of the image in order
to produce a labeled image.

Please confirm is this is what you are looking
for, and in that case we can put together such
a filter, since this seems to be a functionality
that will be useful for many users.

Note that there is a point where this is actually
a problem for a Gaussian Mixture Model. In which
case, there are other classes in ITK that are well
suited for solving that classification problem.


In fact, there is a "Expectation Maximization
Mixture Model Estimation" example in the ITK
Software Guide

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

Section 10.3.3, pdf-page 475,


Yet another option is to use Markov Random Fields,
for which ITK have several filters too.



    Regards,



       Luis



-------------------------------
Radhika Sivaramakrishna wrote:
> Hi Luis,
> Thanks for your prompt response. Yes, I did have a couple of
questions.
> 
> 1) I checked the documentation for OtsuMultipleThresholds. It is
> templated on input histogram. It says you have to specify the target
> histogram. What does this mean? Is there a way to just pass the
original
> image with the number of thresholds you want to identify, and it
should
> return the thresholds that best separate the multiple classes?
> 
> 2) Do you have recommendations for other types of filters/methods I
can
> use to separate an image into essentially three portions, a background
> which is darker, a foreground, another region within foreground which
in
> general is brighter than the rest of the foreground.
> 
> Thanks
> Radhika
> 
> 
> -----Original Message-----
> From: Luis Ibanez [mailto:luis.ibanez at kitware.com] 
> Sent: Wednesday, October 27, 2004 3:41 PM
> To: Radhika Sivaramakrishna
> Cc: insight-users at itk.org
> Subject: Re: [Insight-users] OtsuThresholdImageFilter
> 
> 
> Hi Radhika,
> 
> 
> In the Doxygen documentation, there are entries for the three classes
> 
>
http://www.itk.org/Insight/Doxygen/html/classitk_1_1OtsuThresholdImageFi
> lter.html
>
http://www.itk.org/Insight/Doxygen/html/classitk_1_1OtsuMultipleThreshol
> dsCalculator.html
>
http://www.itk.org/Insight/Doxygen/html/classitk_1_1OtsuThresholdImageCa
> lculator.html
> 
> 
> The classes
> 
>         OtsuMultipleThresholdsCalculator
>         OtsuThresholdImageFilter
> 
> are relatively new,
> 
> 
> the first one dates from March, (contributed by Luca Antiga)
> the second dates from July
> 
> 
> 
> OtsuMultipleThresholds allows you to compute thresholds from
> gray scale statistical distributlis that are multimodal, while
> the original OtsuThreshold calculator was intended for Bimodal
> distributions.
> 
> 
> The OtsuThresholdImageFilter it a thresholding filter that
> internally computes the threshold for you image by using
> an OtsuThresholdCalculator.
> 
> 
> 
>    Please let us know if you have further questions,
> 
> 
>      Thanks
> 
> 
>        Luis
> 
> 
> 
> ------------------------------
> Radhika Sivaramakrishna wrote:
> 
> 
>>Hi all,
>>
>>In the documentation only the OtsuThresholdImageCalculator is written.
> 
> 
>>However, in the Insight library, we also have 
>>OtsuMultipleThresholdsCalculator and OtsuThresholdImageFilter.
>>
>>Does anyone know how to use these, and why are they not available in
> 
> the 
> 
>>documentation?
>>
>>Thanks
>>
>>Radhika
>>
>> 
>>
>>
>>
> 
>
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> 
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> 
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