BUG: Fix bisection midpoint in ThresholdMaximumConnectedComponents

Modules/Segmentation/ConnectedComponents/include/itkThresholdMaximumConnectedComponentsImageFilter.hxx

@@ -103,7 +103,7 @@ ThresholdMaximumConnectedComponentsImageFilter<TInputImage, TOutputImage>::Gener
   m_ThresholdFilter->SetInsideValue(m_InsideValue);
   m_ThresholdFilter->SetUpperThreshold(m_UpperBoundary);
 
-  PixelType midpoint = (upperBound - lowerBound) / 2;
+  PixelType midpoint = lowerBound + (upperBound - lowerBound) / 2;
   PixelType midpointL = (lowerBound + (midpoint - lowerBound) / 2);
   PixelType midpointR = (upperBound - (upperBound - midpoint) / 2);
 

Modules/Segmentation/ConnectedComponents/test/CMakeLists.txt

@@ -204,6 +204,7 @@ set(
   ITKConnectedComponentsGTests
   itkConnectedComponentImageFilterGTest.cxx
   itkRelabelComponentImageFilterGTest.cxx
+  itkThresholdMaximumConnectedComponentsImageFilterGTest.cxx
 )
 creategoogletestdriver(ITKConnectedComponents "${ITKConnectedComponents-Test_LIBRARIES}"
                        "${ITKConnectedComponentsGTests}"

Modules/Segmentation/ConnectedComponents/test/itkThresholdMaximumConnectedComponentsImageFilterGTest.cxx

@@ -0,0 +1,75 @@
+/*=========================================================================
+ *
+ *  Copyright NumFOCUS
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *         https://www.apache.org/licenses/LICENSE-2.0.txt
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *=========================================================================*/
+
+#include "itkGTest.h"
+#include "itkImage.h"
+#include "itkThresholdMaximumConnectedComponentsImageFilter.h"
+
+namespace
+{
+itk::Image<unsigned int, 2>::Pointer
+CreateDumbbellImage(unsigned int offset)
+{
+  using namespace itk::GTest::TypedefsAndConstructors::Dimension2;
+
+  using PixelType = unsigned int;
+  using ImageType = itk::Image<PixelType, Dimension>;
+
+  auto image = ImageType::New();
+  image->SetRegions(ImageType::RegionType(itk::MakeSize(9u, 3u)));
+  image->AllocateInitialized();
+
+  for (unsigned int x = 0; x < 9; ++x)
+  {
+    image->SetPixel({ { x, 0 } }, offset);
+    image->SetPixel({ { x, 2 } }, offset);
+  }
+  for (unsigned int x = 0; x < 3; ++x)
+  {
+    image->SetPixel({ { x, 1 } }, offset + 20);
+  }
+  for (unsigned int x = 3; x < 6; ++x)
+  {
+    image->SetPixel({ { x, 1 } }, offset + 5);
+  }
+  for (unsigned int x = 6; x < 9; ++x)
+  {
+    image->SetPixel({ { x, 1 } }, offset + 20);
+  }
+
+  return image;
+}
+} // namespace
+
+TEST(ThresholdMaximumConnectedComponentsImageFilter, BisectionIsTranslationInvariant)
+{
+  using ImageType = itk::Image<unsigned int, 2>;
+  using FilterType = itk::ThresholdMaximumConnectedComponentsImageFilter<ImageType>;
+
+  auto filterA = FilterType::New();
+  filterA->SetInput(CreateDumbbellImage(0));
+  filterA->Update();
+
+  constexpr unsigned int offset{ 3000000000u };
+  auto                   filterB = FilterType::New();
+  filterB->SetInput(CreateDumbbellImage(offset));
+  filterB->Update();
+
+  EXPECT_EQ(filterB->GetNumberOfObjects(), filterA->GetNumberOfObjects());
+  EXPECT_EQ(filterB->GetThresholdValue(), filterA->GetThresholdValue() + offset);
+}