[Insight-users] WatershedSegmentation1 example parameters

[Luis Ibanez]

Hi Pedro,


    "When everthing else fails...
           read the instructions"


The value that you are providing for the threshold
is exteremly high. This is supposed to be a number
in the interval [0:1].  You are using 50.0 right now.

Your value of water level is also very high = 0.3.
A more reasonable starting point could be 0.05.

--

Please read the SoftwareGuide instructions before
trying to use this example:

    http://www.itk.org/ItkSoftwareGuide.pdf
    Section 8.2.2, pdf-page 260.

In page 261 you will find the recommendation on the
range of values for the threshold.

In particular the example in Figure 8.8 will give
you an indication of the range of values expected.

A good starting value may be Threshold = 0.01 and
only increase it if you image is really noisy. Altough,
if the image is very noisy, the real solution is to
apply some smoothing filtering before running the
watershed filter.


Regards,


     Luis




--------------------
Pedro Patron wrote:
> Hi everybody!
> I'm trying to make run the WatershedSegmentation1 example and and I'd tried different parameter values but I always get the same answer. Example:
> 
> WatershedSegmentation1 ../../src/Examples/Data/BrainProtonDensitySlice.png out.png 3.0 5 50 0.3 0.4
> 
> itk::ExceptionObject (0x81462c0)
> Location: "Unknown"
> File: /Itk-1.2.0/Insight/src/Code/Algorithms/itkWatershedSegmentTreeGenerator.txx
> Line: 428
> Description: itk::ERROR: itk::watershed::SegmentTreeGenerator::MergeSegments:: An unexpected and fatal error has occurred. This is probably the result of overthresholding of the input image.
> 
> There are not an example of these values in the ITK Software Guide and I don't know how can I test the BrainProtonDensitySlice.png image
> 
> Could anyone help me?
> 
> Thank you in advance,
> 
> Pedro
> 
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