[Insight-users] Apply itk::HoughTransform2DCirclesImageFilter to extract circles

[Gaby Tu]

Dear all,

I was trying to apply itk::HoughTransform2DCirclesImageFilter to extract
the circle in red in the following PNG file.

[image: 內置圖片 2]
And following is my code for setting up the filter.

        typedef itk::Image<short, 2 > SliceType;
        typedef itk::Image< float, 2 > AccumulatorImageType;
typedef
itk::HoughTransform2DCirclesImageFilter<SliceType::PixelType,AccumulatorImageType::PixelType>
HoughTransformFilterType;
HoughTransformFilterType::Pointer houghFilter =
HoughTransformFilterType::New();
houghFilter->SetInput(RescaleFilter->GetOutput());
houghFilter->SetNumberOfCircles( 3);
houghFilter->SetMinimumRadius( 10 );
houghFilter->SetMaximumRadius( 30 );
houghFilter->SetSweepAngle(0.52);
try
{
houghFilter->Update();
}
catch (itk::ExceptionObject & e)
{
std::cerr << "exception in file writer " << std::endl;
std::cerr << e << std::endl;
return EXIT_FAILURE;
}

And the result is shown in the following PNG file.
[image: 內置圖片 3]
Comparing this image with previous one, there are three circles in white.

The result puzzled me a lot,
1. Two of the circles detected are not circles, obviously. And there is a
circle which is more like a circle, actually.
2. In my understanding, this filter would create many circles, which would
be organized in some order, value of radius?

And I have tried other values for SweepAngle, but still result similar to
above is present.

Expect your help!
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