InsightSoftwareConsortium · hjmjohnson · Oct 9, 2018
diff --git a/Modules/Core/Common/include/itkConstantBoundaryImageNeighborhoodPixelAccessPolicy.h b/Modules/Core/Common/include/itkConstantBoundaryImageNeighborhoodPixelAccessPolicy.h
@@ -0,0 +1,159 @@
+/*=========================================================================
+*
+*  Copyright Insight Software Consortium
+*
+*  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
+*
+*         http://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.
+*
+*=========================================================================*/
+
+#ifndef itkConstantBoundaryImageNeighborhoodPixelAccessPolicy_h
+#define itkConstantBoundaryImageNeighborhoodPixelAccessPolicy_h
+
+#include "itkIndex.h"
+#include "itkOffset.h"
+#include "itkSize.h"
+
+namespace itk
+{
+namespace Experimental
+{
+
+/**
+ * \class ConstantBoundaryImageNeighborhoodPixelAccessPolicy
+ * ImageNeighborhoodPixelAccessPolicy class for ShapedImageNeighborhoodRange.
+ * Allows getting and setting the value of a pixel, located in a specified
+ * neighborhood location, at a specified offset. Uses a constant as value
+ * for pixels outside the image border.
+ *
+ * \see ShapedNeighborhoodIterator
+ * \see ConstantBoundaryCondition
+ * \ingroup ImageIterators
+ * \ingroup ITKCommon
+ */
+template <typename TImage>
+class ConstantBoundaryImageNeighborhoodPixelAccessPolicy final
+{
+private:
+  using NeighborhoodAccessorFunctorType = typename TImage::NeighborhoodAccessorFunctorType;
+  using PixelType = typename TImage::PixelType;
+  using InternalPixelType = typename TImage::InternalPixelType;
+
+  using ImageDimensionType = typename TImage::ImageDimensionType;
+  static constexpr ImageDimensionType ImageDimension = TImage::ImageDimension;
+
+  using IndexType = Index<ImageDimension>;
+  using OffsetType = Offset<ImageDimension>;
+  using ImageSizeType = Size<ImageDimension>;
+  using ImageSizeValueType = SizeValueType;
+
+  // Index value to the image buffer, indexing the current pixel. -1 is used to indicate out-of-bounds.
+  const IndexValueType m_PixelIndexValue;
+
+  // A reference to the accessor of the image.
+  const NeighborhoodAccessorFunctorType& m_NeighborhoodAccessor;
+
+  // The constant whose value is returned a pixel value outside the image is queried.
+  const PixelType m_Constant;
+
+
+  // Private helper function. Tells whether the pixel at 'pixelIndex' is inside the image.
+  static bool IsInside(
+    const IndexType& pixelIndex,
+    const ImageSizeType& imageSize) ITK_NOEXCEPT
+  {
+    bool result = true;
+
+    for (ImageDimensionType i = 0; i < ImageDimension; ++i)
+    {
+      const IndexValueType indexValue = pixelIndex[i];
+
+      // Note: Do not 'quickly' break or return out of the for-loop when the
+      // result is false! For performance reasons (loop unrolling, etc.) it
+      // appears preferable to complete the for-loop iteration in this case!
+      result = result &&
+        (indexValue >= 0) &&
+        (static_cast<ImageSizeValueType>(indexValue) < imageSize[i]);
+    }
+    return result;
+  }
+
+
+  // Private helper function. Calculates and returns the index value of the
+  // current pixel within the image buffer.
+  static IndexValueType CalculatePixelIndexValue(
+    const OffsetType& offsetTable,
+    const IndexType& pixelIndex) ITK_NOEXCEPT
+  {
+    IndexValueType result = 0;
+
+    for (ImageDimensionType i = 0; i < ImageDimension; ++i)
+    {
+      result += pixelIndex[i] * offsetTable[i];
+    }
+    return result;
+  }
+
+public:
+  // Deleted member functions:
+  ConstantBoundaryImageNeighborhoodPixelAccessPolicy() = delete;
+  ConstantBoundaryImageNeighborhoodPixelAccessPolicy& operator=(const ConstantBoundaryImageNeighborhoodPixelAccessPolicy&) = delete;
+
+  // Explicitly-defaulted functions:
+  ~ConstantBoundaryImageNeighborhoodPixelAccessPolicy() = default;
+  ConstantBoundaryImageNeighborhoodPixelAccessPolicy(
+    const ConstantBoundaryImageNeighborhoodPixelAccessPolicy&) = default;
+
+  /** Constructor called directly by the pixel proxy of
+   * ShapedImageNeighborhoodRange. */
+  ConstantBoundaryImageNeighborhoodPixelAccessPolicy(
+    const ImageSizeType& imageSize,
+    const OffsetType& offsetTable,
+    const NeighborhoodAccessorFunctorType& neighborhoodAccessor,
+    const IndexType& pixelIndex,
+    const PixelType constant = {}) ITK_NOEXCEPT
+    :
+  m_PixelIndexValue
+  {
+    IsInside(pixelIndex, imageSize) ? CalculatePixelIndexValue(offsetTable, pixelIndex) : -1
+  },
+  m_NeighborhoodAccessor(neighborhoodAccessor),
+  m_Constant{constant}
+  {
+  }
+
+
+  /** Retrieves the pixel value from the image buffer, at the current
+   * index. When the index is out of bounds, it returns the constant
+   * value specified during construction. */
+  PixelType GetPixelValue(const InternalPixelType* const imageBufferPointer) const ITK_NOEXCEPT
+  {
+    return (m_PixelIndexValue < 0) ?
+      m_Constant :
+      m_NeighborhoodAccessor.Get(imageBufferPointer + m_PixelIndexValue);
+  }
+
+  /** Sets the value of the image buffer at the current index value to the
+   * specified value.  */
+  void SetPixelValue(InternalPixelType* const imageBufferPointer, const PixelType& pixelValue) const ITK_NOEXCEPT
+  {
+    if (m_PixelIndexValue >= 0)
+    {
+      m_NeighborhoodAccessor.Set(imageBufferPointer + m_PixelIndexValue, pixelValue);
+    }
+  }
+};
+
+} // namespace Experimental
+} // namespace itk
+
+#endif
diff --git a/Modules/Core/Common/include/itkShapedImageNeighborhoodRange.h b/Modules/Core/Common/include/itkShapedImageNeighborhoodRange.h
@@ -35,6 +35,16 @@ namespace itk
 namespace Experimental
 {
 
+/**
+ * \class EmptyPixelAccessParameter
+ * Empty struct, used by ShapedImageNeighborhoodRange to denote that
+ * there is no pixel access parameter specified.
+ *
+ * \ingroup ImageIterators
+ * \ingroup ITKCommon
+ */
+struct EmptyPixelAccessParameter {};
+
 /**
  * \class ShapedImageNeighborhoodRange
  * Modern C++11 range to iterate over a neighborhood of pixels.
@@ -90,7 +100,8 @@ namespace Experimental
  * \ingroup ITKCommon
  */
 template<typename TImage,
-  typename TImageNeighborhoodPixelAccessPolicy = ZeroFluxNeumannImageNeighborhoodPixelAccessPolicy<TImage>>
+  typename TImageNeighborhoodPixelAccessPolicy = ZeroFluxNeumannImageNeighborhoodPixelAccessPolicy<TImage>,
+  typename TOptionalPixelAccessParameter = EmptyPixelAccessParameter>
 class ShapedImageNeighborhoodRange final
 {
 private:
@@ -139,13 +150,10 @@ class ShapedImageNeighborhoodRange final
     // Constructor, called directly by operator*() of the iterator class.
     PixelProxy(
       const InternalPixelType* const imageBufferPointer,
-      const ImageSizeType& imageSize,
-      const OffsetType& offsetTable,
-      const NeighborhoodAccessorFunctorType& neighborhoodAccessor,
-      const IndexType& pixelIndex) ITK_NOEXCEPT
+      const TImageNeighborhoodPixelAccessPolicy& pixelAccessPolicy) ITK_NOEXCEPT
       :
     m_ImageBufferPointer{imageBufferPointer},
-    m_PixelAccessPolicy{ imageSize, offsetTable, neighborhoodAccessor, pixelIndex }
+    m_PixelAccessPolicy{pixelAccessPolicy}
     {
     }
 
@@ -192,13 +200,10 @@ class ShapedImageNeighborhoodRange final
     // Constructor, called directly by operator*() of the iterator class.
     PixelProxy(
       InternalPixelType* const imageBufferPointer,
-      const ImageSizeType& imageSize,
-      const OffsetType& offsetTable,
-      const NeighborhoodAccessorFunctorType& neighborhoodAccessor,
-      const IndexType& pixelIndex) ITK_NOEXCEPT
+      const TImageNeighborhoodPixelAccessPolicy& pixelAccessPolicy) ITK_NOEXCEPT
       :
     m_ImageBufferPointer{imageBufferPointer},
-    m_PixelAccessPolicy{ imageSize, offsetTable, neighborhoodAccessor, pixelIndex }
+    m_PixelAccessPolicy{pixelAccessPolicy}
     {
     }
 
@@ -284,6 +289,8 @@ class ShapedImageNeighborhoodRange final
     // The accessor of the image.
     NeighborhoodAccessorFunctorType m_NeighborhoodAccessor;
 
+    TOptionalPixelAccessParameter m_OptionalPixelAccessParameter;
+
     // The pixel coordinates of the location of the neighborhood.
     // May be outside the image!
     IndexType m_Location = { {} };
@@ -297,6 +304,7 @@ class ShapedImageNeighborhoodRange final
       const ImageSizeType& imageSize,
       const OffsetType& offsetTable,
       const NeighborhoodAccessorFunctorType& neighborhoodAccessor,
+      const TOptionalPixelAccessParameter optionalPixelAccessParameter,
       const IndexType& location,
       const OffsetType* const offset) ITK_NOEXCEPT
       :
@@ -306,12 +314,29 @@ class ShapedImageNeighborhoodRange final
     m_ImageSize(imageSize),
     m_OffsetTable(offsetTable),
     m_NeighborhoodAccessor(neighborhoodAccessor),
+    m_OptionalPixelAccessParameter(optionalPixelAccessParameter),
     m_Location(location),
     m_CurrentOffset{offset}
     {
       assert(m_ImageBufferPointer != nullptr);
     }
 
+
+    TImageNeighborhoodPixelAccessPolicy CreatePixelAccessPolicy(EmptyPixelAccessParameter) const
+    {
+      return TImageNeighborhoodPixelAccessPolicy{ m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_Location + *m_CurrentOffset };
+    }
+
+    template <typename TPixelAccessParameter>
+    TImageNeighborhoodPixelAccessPolicy CreatePixelAccessPolicy(const TPixelAccessParameter pixelAccessParameter) const
+    {
+      static_assert(std::is_same< TPixelAccessParameter, TOptionalPixelAccessParameter>::value,
+        "This helper function should only be used for TOptionalPixelAccessParameter!");
+      static_assert(!std::is_same< TPixelAccessParameter, EmptyPixelAccessParameter>::value,
+        "EmptyPixelAccessParameter indicates that there is no pixel access parameter specified!");
+      return TImageNeighborhoodPixelAccessPolicy{ m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_Location + *m_CurrentOffset, pixelAccessParameter };
+    }
+
   public:
     // Types conforming the iterator requirements of the C++ standard library:
     using difference_type = std::ptrdiff_t;
@@ -347,8 +372,7 @@ class ShapedImageNeighborhoodRange final
     /**  Returns a reference to the current pixel. */
     reference operator*() const ITK_NOEXCEPT
     {
-      return reference{m_ImageBufferPointer, m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_Location + *m_CurrentOffset};
-    }
+      return {m_ImageBufferPointer, CreatePixelAccessPolicy(m_OptionalPixelAccessParameter)};
 
 
     /** Prefix increment ('++it'). */
@@ -535,6 +559,8 @@ class ShapedImageNeighborhoodRange final
   // The number of neighborhood pixels.
   const std::size_t m_NumberOfNeighborhoodPixels;
 
+  const TOptionalPixelAccessParameter m_OptionalPixelAccessParameter;
+
 public:
   using const_iterator = QualifiedIterator<true>;
   using iterator = QualifiedIterator<false>;
@@ -549,7 +575,8 @@ class ShapedImageNeighborhoodRange final
     ImageType& image,
     const IndexType& location,
     const OffsetType* const shapeOffsets,
-    const std::size_t numberOfNeigborhoodPixels)
+    const std::size_t numberOfNeigborhoodPixels,
+    const TOptionalPixelAccessParameter optionalPixelAccessParameter = {})
     :
   m_ImageBufferPointer{image.ImageType::GetBufferPointer()},
   // Note: Use parentheses instead of curly braces to initialize data members,
@@ -559,7 +586,8 @@ class ShapedImageNeighborhoodRange final
   m_NeighborhoodAccessor(image.GetNeighborhoodAccessor()),
   m_Location(location),
   m_ShapeOffsets{ shapeOffsets },
-  m_NumberOfNeighborhoodPixels{ numberOfNeigborhoodPixels }
+  m_NumberOfNeighborhoodPixels{ numberOfNeigborhoodPixels },
+  m_OptionalPixelAccessParameter(optionalPixelAccessParameter)
   {
     assert(m_ImageBufferPointer != nullptr);
     const OffsetValueType* const offsetTable = image.GetOffsetTable();
@@ -580,13 +608,17 @@ class ShapedImageNeighborhoodRange final
   ShapedImageNeighborhoodRange(
     ImageType& image,
     const IndexType& location,
-    TContainerOfOffsets&& shapeOffsets)
+    TContainerOfOffsets&& shapeOffsets,
+    const TOptionalPixelAccessParameter optionalPixelAccessParameter = {})
     :
-  ShapedImageNeighborhoodRange{
+  ShapedImageNeighborhoodRange
+  {
     image,
     location,
     shapeOffsets.data(),
-    shapeOffsets.size()}
+    shapeOffsets.size(),
+    optionalPixelAccessParameter
+  }
   {
     static_assert(!std::is_rvalue_reference<decltype(shapeOffsets)>::value,
       "The container of offsets should not be a temporary (rvalue) object!");
@@ -596,14 +628,14 @@ class ShapedImageNeighborhoodRange final
   iterator begin() const ITK_NOEXCEPT
   {
     assert(m_ImageBufferPointer != nullptr);
-    return iterator(m_ImageBufferPointer, m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_Location, m_ShapeOffsets);
+    return iterator(m_ImageBufferPointer, m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_OptionalPixelAccessParameter, m_Location, m_ShapeOffsets);
   }
 
   /** Returns an 'end iterator' for this range. */
   iterator end() const ITK_NOEXCEPT
   {
     assert(m_ImageBufferPointer != nullptr);
-    return iterator(m_ImageBufferPointer, m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_Location, m_ShapeOffsets + m_NumberOfNeighborhoodPixels);
+    return iterator(m_ImageBufferPointer, m_ImageSize, m_OffsetTable, m_NeighborhoodAccessor, m_OptionalPixelAccessParameter, m_Location, m_ShapeOffsets + m_NumberOfNeighborhoodPixels);
   }
 
   /** Returns a const iterator to the first neighborhood pixel.

diff --git a/Modules/Core/Common/test/CMakeLists.txt b/Modules/Core/Common/test/CMakeLists.txt
@@ -627,6 +627,7 @@ set(ITKCommonGTests
       itkAggregateTypesTest.cxx
       itkBuildInformationTest.cxx
       itkConnectedImageNeighborhoodShapeGTest.cxx
+      itkConstantBoundaryImageNeighborhoodPixelAccessPolicyGTest.cxx
       itkImageNeighborhoodOffsetsGTest.cxx
       itkIndexRangeGTest.cxx
       itkShapedImageNeighborhoodRangeGTest.cxx