STYLE: Declare local ImageRegion variables const

Replaced lines of code like the following:

    RegionType region;
    region.SetIndex(index);
    region.SetSize(size);

With:

    const RegionType region(index, size);

Following C++ Core Guidelines, August 19, 2021, "By default, make objects immutable"
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rconst-immutable

Author: N-Dekker

Modules/Bridge/VTK/include/itkVTKImageExport.hxx

@@ -358,9 +358,7 @@ VTKImageExport<TInputImage>::PropagateUpdateExtentCallback(int * extent)
     size[i] = (extent[i * 2 + 1] - extent[i * 2]) + 1;
   }
 
-  InputRegionType region;
-  region.SetSize(size);
-  region.SetIndex(index);
+  const InputRegionType region(index, size);
 
   InputImagePointer input = this->GetInput();
   if (!input)

Modules/Bridge/VTK/include/itkVTKImageImport.hxx

@@ -193,9 +193,7 @@ VTKImageImport<TOutputImage>::GenerateOutputInformation()
       size[i] = (extent[i * 2 + 1] - extent[i * 2]) + 1;
     }
 
-    OutputRegionType region;
-    region.SetIndex(index);
-    region.SetSize(size);
+    const OutputRegionType region(index, size);
     output->SetLargestPossibleRegion(region);
   }
   if (m_SpacingCallback)
@@ -325,9 +323,7 @@ VTKImageImport<TOutputImage>::GenerateData()
       importSize *= size[i];
     }
 
-    OutputRegionType region;
-    region.SetIndex(index);
-    region.SetSize(size);
+    const OutputRegionType region(index, size);
     output->SetBufferedRegion(region);
 
     void * data = (m_BufferPointerCallback)(m_CallbackUserData);

Modules/Core/Common/include/itkConstNeighborhoodIterator.hxx

@@ -201,10 +201,7 @@ auto
 ConstNeighborhoodIterator<TImage, TBoundaryCondition>::GetBoundingBoxAsImageRegion() const -> RegionType
 {
   const IndexValueType zero = NumericTraits<IndexValueType>::ZeroValue();
-  RegionType           ans;
-
-  ans.SetIndex(this->GetIndex(zero));
-  ans.SetSize(this->GetSize());
+  const RegionType     ans(this->GetIndex(zero), this->GetSize());
 
   return ans;
 }

Modules/Core/Common/include/itkConstNeighborhoodIteratorWithOnlyIndex.hxx

@@ -121,9 +121,7 @@ auto
 ConstNeighborhoodIteratorWithOnlyIndex<TImage>::GetBoundingBoxAsImageRegion() const -> RegionType
 {
   const IndexValueType zero = NumericTraits<IndexValueType>::ZeroValue();
-  RegionType           ans;
-  ans.SetIndex(this->GetIndex(zero));
-  ans.SetSize(this->GetSize());
+  const RegionType     ans(this->GetIndex(zero), this->GetSize());
 
   return ans;
 }

Modules/Core/Common/include/itkOctree.hxx

@@ -265,11 +265,9 @@ Octree<TPixel, ColorTableSize, MappingFunctionType>::GetImage() -> ImageTypePoin
   sizes[1] = m_TrueDims[1];
   sizes[2] = m_TrueDims[2];
   imageSize.SetSize(sizes);
-  const typename ImageType::IndexType imageIndex = { { 0, 0, 0 } };
-  typename ImageType::RegionType      region;
-  region.SetSize(imageSize);
-  region.SetIndex(imageIndex);
-  auto img = ImageType::New();
+  const typename ImageType::IndexType  imageIndex = { { 0, 0, 0 } };
+  const typename ImageType::RegionType region(imageIndex, imageSize);
+  auto                                 img = ImageType::New();
   img->SetLargestPossibleRegion(region);
   img->SetBufferedRegion(region);
   img->SetRequestedRegion(region);

Modules/Core/Mesh/include/itkTriangleMeshToBinaryImageFilter.hxx

@@ -156,10 +156,7 @@ TriangleMeshToBinaryImageFilter<TInputMesh, TOutputImage>::GenerateData()
       itkExceptionMacro(<< "Must Set Image Size");
     }
 
-    typename OutputImageType::RegionType region;
-
-    region.SetSize(m_Size);
-    region.SetIndex(m_Index);
+    const typename OutputImageType::RegionType region(m_Index, m_Size);
 
     OutputImage->SetLargestPossibleRegion(region); //
     OutputImage->SetBufferedRegion(region);        // set the region

Modules/Core/SpatialObjects/include/itkMetaImageConverter.hxx

@@ -65,11 +65,9 @@ MetaImageConverter<NDimensions, PixelType, TSpatialObjectType>::AllocateImage(co
     }
   }
 
-  RegionType region;
-  region.SetSize(size);
   itk::Index<NDimensions> zeroIndex;
   zeroIndex.Fill(0);
-  region.SetIndex(zeroIndex);
+  const RegionType region(zeroIndex, size);
   rval->SetLargestPossibleRegion(region);
   rval->SetBufferedRegion(region);
   rval->SetRequestedRegion(region);

Modules/Core/SpatialObjects/include/itkSpatialObjectToImageStatisticsCalculator.hxx

@@ -186,9 +186,7 @@ SpatialObjectToImageStatisticsCalculator<TInputImage, TInputSpatialObject, TSamp
       }
     }
 
-    RegionType region;
-    region.SetIndex(indMin);
-    region.SetSize(size);
+    const RegionType region(indMin, size);
 
     using IteratorType = ImageRegionConstIteratorWithIndex<ImageType>;
     IteratorType it = IteratorType(m_Image, region);

Modules/Core/TestKernel/include/itkRandomImageSource.hxx

@@ -204,9 +204,7 @@ RandomImageSource<TOutputImage>::GenerateOutputInformation()
 
   output = this->GetOutput(0);
 
-  typename TOutputImage::RegionType largestPossibleRegion;
-  largestPossibleRegion.SetSize(this->m_Size);
-  largestPossibleRegion.SetIndex(index);
+  const typename TOutputImage::RegionType largestPossibleRegion(index, this->m_Size);
   output->SetLargestPossibleRegion(largestPossibleRegion);
 
   output->SetSpacing(m_Spacing);

Modules/Core/Transform/include/itkBSplineBaseTransform.hxx

@@ -265,12 +265,10 @@ BSplineBaseTransform<TParametersValueType, NDimensions, VSplineOrder>::
   this->m_WeightsFunction->Evaluate(index, weights, supportIndex);
 
   // For each dimension, copy the weight to the support region
-  RegionType supportRegion;
-  SizeType   supportSize;
+  SizeType supportSize;
   supportSize.Fill(SplineOrder + 1);
-  supportRegion.SetSize(supportSize);
-  supportRegion.SetIndex(supportIndex);
-  unsigned long counter = 0;
+  const RegionType supportRegion(supportIndex, supportSize);
+  unsigned long    counter = 0;
 
   using IteratorType = ImageRegionIterator<ImageType>;