Checks that the center of a circle detected by HoughTransform2DCirclesImageFilter is inside the circle, using ITK 4.13

CenterIsInsideCircle.cxx

// Author: Niels Dekker, LKEB, Leiden University Medical Center, The Netherlands
//
// Example code from https://discourse.itk.org/t/hough-transform-2d-circles-image-filter-getcircles-patch/350/63

#include <itkHoughTransform2DCirclesImageFilter.h>
#include <itkImage.h>
#include <iostream>

int main()
{
  // Create an image with a circle centered at [6, 8]:
  enum { centerX = 6, centerY = 8 };
  const auto image = itk::Image<unsigned>::New();
  image->SetRegions({ 16, 16 });
  image->Allocate(true);
  image->SetPixel({ centerX, centerY }, 1);
  image->SetPixel({ centerX, centerY - 1 }, 1);
  image->SetPixel({ centerX, centerY + 1 }, 1);
  image->SetPixel({ centerX - 1, centerY }, 1);
  image->SetPixel({ centerX + 1, centerY }, 1);

  const auto filter =
    itk::HoughTransform2DCirclesImageFilter<unsigned, unsigned, double>::New();
  filter->SetInput(image);
  filter->Update();

  // GetCircles() finds a circle of radius 1, centered at [6, 8].
  const auto& spatialObject = filter->GetCircles().front();
  spatialObject->ComputeObjectToWorldTransform();

  const double center[] = { centerX, centerY };
  const bool isInside = spatialObject->IsInside(center);

  std::cout << (isInside ?
    "OK: The center is inside." :
    "ERROR: The center is not inside!") << std::endl;

  return isInside ? EXIT_SUCCESS : EXIT_FAILURE;
}