STYLE: Declare m_SmoothingFilters as std::array, instead of C array

Increased the consistency of `m_SmoothingFilters` declarations of recursive
Gaussian filters.

Following pull request #5730
commit 529d8f9 and a837ee5

Author: N-Dekker

Modules/Filtering/ImageFeature/include/itkLaplacianRecursiveGaussianImageFilter.h

@@ -21,6 +21,7 @@
 #include "itkRecursiveGaussianImageFilter.h"
 #include "itkImage.h"
 #include "itkCommand.h"
+#include <array>
 
 namespace itk
 {
@@ -129,8 +130,8 @@ class ITK_TEMPLATE_EXPORT LaplacianRecursiveGaussianImageFilter : public ImageTo
   EnlargeOutputRequestedRegion(DataObject * output) override;
 
 private:
-  GaussianFilterPointer   m_SmoothingFilters[NumberOfSmoothingFilters]{};
-  DerivativeFilterPointer m_DerivativeFilter{};
+  std::array<GaussianFilterPointer, NumberOfSmoothingFilters> m_SmoothingFilters{};
+  DerivativeFilterPointer                                     m_DerivativeFilter{};
 
   /** Normalize the image across scale space */
   bool m_NormalizeAcrossScale{};

Modules/Filtering/ImageGradient/include/itkGradientMagnitudeRecursiveGaussianImageFilter.h

@@ -24,6 +24,7 @@
 #include "itkRecursiveGaussianImageFilter.h"
 #include "itkSqrtImageFilter.h"
 #include "itkBinaryGeneratorImageFilter.h"
+#include <array>
 
 namespace itk
 {
@@ -161,10 +162,10 @@ class ITK_TEMPLATE_EXPORT GradientMagnitudeRecursiveGaussianImageFilter
   using SqrSpacingFilterType = BinaryGeneratorImageFilter<RealImageType, RealImageType, RealImageType>;
   using SqrSpacingFilterPointer = typename SqrSpacingFilterType::Pointer;
 
-  GaussianFilterPointer   m_SmoothingFilters[ImageDimension - 1]{};
-  DerivativeFilterPointer m_DerivativeFilter{};
-  SqrSpacingFilterPointer m_SqrSpacingFilter{};
-  SqrtFilterPointer       m_SqrtFilter{};
+  std::array<GaussianFilterPointer, ImageDimension - 1> m_SmoothingFilters{};
+  DerivativeFilterPointer                               m_DerivativeFilter{};
+  SqrSpacingFilterPointer                               m_SqrSpacingFilter{};
+  SqrtFilterPointer                                     m_SqrtFilter{};
 
   /** Normalize the image across scale space */
   bool m_NormalizeAcrossScale{};

Modules/Filtering/Smoothing/include/itkSmoothingRecursiveGaussianImageFilter.h

@@ -24,6 +24,7 @@
 #include "itkImage.h"
 #include "itkPixelTraits.h"
 #include "itkCommand.h"
+#include <array>
 
 namespace itk
 {
@@ -167,9 +168,9 @@ class ITK_TEMPLATE_EXPORT SmoothingRecursiveGaussianImageFilter : public InPlace
   EnlargeOutputRequestedRegion(DataObject * output) override;
 
 private:
-  InternalGaussianFilterPointer m_SmoothingFilters[ImageDimension - 1]{};
-  FirstGaussianFilterPointer    m_FirstSmoothingFilter{};
-  CastingFilterPointer          m_CastingFilter{};
+  std::array<InternalGaussianFilterPointer, ImageDimension - 1> m_SmoothingFilters{};
+  FirstGaussianFilterPointer                                    m_FirstSmoothingFilter{};
+  CastingFilterPointer                                          m_CastingFilter{};
 
   bool m_NormalizeAcrossScale{ false };