[Insight-users] Bug in watershed filter

[Dženan Zukić]

I think I have discovered a bug in WatershedImageFilter. Below is MWE which
reproduces the problem. Input, output and expected image attached.

The problem is that watershed lines are wrongly placed and rough (see
attached error highlights). I first discovered it while working with 3D
images, where the problem is more pronounced. I can also supply 3D float
images (1.3MB). MorphologicalWatershedFromMarkersImageFilter suffers from
the same problem.

#include <itkImageFileReader.h>
#include <itkImageFileWriter.h>
#include <itkWatershedImageFilter.h>
#include <itkCastImageFilter.h>

typedef itk::Image<unsigned char, 2> VisualizingImageType;

void main()
{
    typedef itk::ImageFileReader<VisualizingImageType> rType;
    rType::Pointer reader=rType::New();
    reader->SetFileName("image2D.png");
    reader->Update();
    VisualizingImageType::Pointer dm=reader->GetOutput();
    typedef itk::WatershedImageFilter<VisualizingImageType> wsType;
    wsType::Pointer ws2=wsType::New();
    ws2->SetThreshold(0);
    ws2->SetLevel(0);
    ws2->SetInput(dm);
    ws2->Update();
    typedef itk::CastImageFilter<wsType::OutputImageType,
VisualizingImageType> castType;
    castType::Pointer caster=castType::New();
    caster->SetInput(ws2->GetOutput());
    caster->Update();
    typedef itk::ImageFileWriter<VisualizingImageType> wType;
    wType::Pointer writer=wType::New();
    writer->SetFileName("imageWSint.png");
    writer->SetInput(caster->GetOutput());
    writer->Update();
}
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