[Insight-users] Pixels greater than 0 in an image

[Luca Antiga]

Hi all,
OtsuMultipleThresholdsCalculator already takes a histogram in input
and produces a vector of thresholds (I contributed that class a while
ago).
Set the number of thresholds to one and you should be done.

Luca


On 5/16/08, Gaëtan Lehmann <gaetan.lehmann at jouy.inra.fr> wrote:
>
> Hi,
>
> A cleaner (and heavier) alternative would be to refactor the
> OtsuThresholdImageCalculator to take a itk::Statistics::Histogram as
> input.
> That way, it would be possible to use the mask capability of the
> histogram generator, and it would make a nice contribution to the
> insight journal :-)
>
> Regards,
>
> Gaëtan
>
>
> Le 14 mai 08 à 00:02, Luis Ibanez a écrit :
>
>>
>> Hi Suyang,
>>
>> You are probably right in that there are other placed in the code
>> that need to be modified.
>>
>> The other alternatives that came to mind were related to using the
>> IntensityWindowingImageFilter in order to make all your negative
>> pixels
>> to be set to zero, but I'm afraid that this will overpopulate the
>> histogram bin of the zero value, and shift the Otsu threshold from
>> the value that you would obtain by simply ignoring all negative
>> values.
>>
>>
>> There must be many other options that are simply escaping me now...
>>
>>
>>
>>                Suggestions anyone ??
>>
>>
>>
>>   Thanks
>>
>>
>>      Luis
>>
>>
>> --------------------
>> Suyang Mei wrote:
>>>  Thanks a lot, Luis, for your prompt response and goog suggestions.
>>>   I looked into the code itkOtsuThresholdImageCalculator.txx,
>>> besides the two places you pointed out need to change, I guess
>>> there are other places need to modify, like totalPixels, imageMin,
>>> these numbers will be different from with 0s and without 0s.
>>>   Definitely it is a way to solve my problem, just wonder if there
>>> are any other alternative ways to go...
>>>   Thanks again for you rhelp.
>>> Suyang
>>> */Luis Ibanez <luis.ibanez at kitware.com>/* wrote:
>>>    Hi Suyang,
>>>    After looking at the code of the
>>> itkOtsuThresholdImageCalculator.txx
>>>    the simplest solution seems to be insert an "infamous" if
>>> statement
>>>    in line 97, inside the while loop of the iterator, something like:
>>>    if( value <= 0 )
>>>    {
>>>    ++iter;
>>>    continue;
>>>    }
>>>    and also in line 72 add:
>>>    if( imageMin < 0 )
>>>    {
>>>    imageMin;
>>>    }
>>>    You could generalize this to any given value K (instead of zero),
>>>    modify the name of the otsu threshold calculator class, and
>>> submit it
>>>    as a contribution to the Insight Journal, or submit it as a
>>> feature
>>>    request to the bug tracker.
>>>    Just to clarify,:what we are suggesting is that you modify your
>>> local
>>>    copy of the itkOtsuThresholdImageCalculator class, in order to add
>>>    this functionality. Renaming the files will help you have access
>>> to
>>>    the new class as well as to the current ITK implementation.
>>>    Regards,
>>>    Luis
>>>    -------------------
>>>    Suyang Mei wrote:
>>>     > Hi, ITK experts -
>>>     >
>>>     > I have a simple question, just want to get some advice from -
>>>     >
>>>     > I have an image, and I want to calculate the Ostu threshold
>>> only
>>>    using
>>>     > the positive pixels in the image.
>>>     >
>>>     > What is the best way to proceed?
>>>     >
>>>     > Thanks a lot in advance.
>>>     >
>>>     > Suyang
>>>     >
>>>     >
>>>     >
>>>     >
>>>
>>> ------------------------------------------------------------------------
>>>     >
>>>     > _______________________________________________
>>>     > Insight-users mailing list
>>>     > Insight-users at itk.org
>>>     > http://www.itk.org/mailman/listinfo/insight-users
>> _______________________________________________
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>
> --
> 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.mandriva.org
> http://www.itk.org  http://www.clavier-dvorak.org
>
>

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Luca Antiga, PhD
 Biomedical Technologies Laboratory
 Bioengineering 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