[Insight-users] Re : threshold parameter in watersehd segmentation

[Juliette Deniau]

Thank you Dan and Luis!
Regards 
Juliette




________________________________
De : Dan Mueller <dan.muel at gmail.com>
À : Juliette Deniau <juliette.deniau at yahoo.fr>
Cc : insight <insight-users at itk.org>
Envoyé le : Mercredi, 10 Décembre 2008, 14h48mn 10s
Objet : Re: [Insight-users] threshold parameter in watersehd segmentation

Hi Juliette,

You may also be interested in
Code/Review/itkMorphologicalWatershedFromMarkersImageFilter which does
not need level/threshold values. Instead you provide a "marker" image,
containing labels roughly corresponding to the desired output labels
(eg. a single seed in each object of interest).

The Insight Journal paper can be found here:
    http://www.insight-journal.org/browse/publication/92

Regards, Dan

2008/12/10 Luis Ibanez <luis.ibanez at kitware.com>:
>
> Hi Juliette,
>
> The Threshold parameter of the watershed filter is expected to be a
> number in the range of values of the input image intensities.
>
> This parameters will be used to define the "smallest" intensity change
> in the image that will be considered as a water basin. Usually you want
> to make this parameter something in the order of 1/100 or 1/1000 of the
> water level (this is just a guideline, not a clear cut rule).
>
> If you set the threshold value too low, then the filter will spend a lot
> of time processing very small details of the image, that you not
> actually care about. Note that if your image has a high level of noise,
> you may want to run a smoothing filter on it, before you pass it to the
> watershed segmentation filter.
>
>
>
>  Regards,
>
>
>      Luis
>
>
> --------------------
> Juliette Deniau wrote:
>>
>> Hi all,
>> Could any one explain me the meaning of the threshold parameter in
>> watersehdImageFilter?
>> I've read the SoftwareGuide and I've understand that this parameter is
>> used to generate the initial segmentation via the steepest descent stategy.
>>  its used to remove shallow background regions...but I couldn't understand
>> its a threshold of what?
>> Thank you
>> Juliette
>>
>>
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