ENH: Restore integer support for laplacian sharpening

Revert to using the a laplacian neighborhood operator over
the recursive laplacian filter which requires real pixel types for
input and output.

Author: blowekamp

Examples/Filtering/LaplacianSharpeningImageFilter.cxx

@@ -34,21 +34,19 @@ main(int argc, char * argv[])
   const char * inputFilename = argv[1];
   const char * outputFilename = argv[2];
 
-  using PixelType = float;
   using CharPixelType = unsigned char;
   constexpr unsigned int Dimension = 2;
 
-  using ImageType = itk::Image<PixelType, Dimension>;
   using CharImageType = itk::Image<CharPixelType, Dimension>;
 
-  using ReaderType = itk::ImageFileReader<ImageType>;
+  using ReaderType = itk::ImageFileReader<CharImageType>;
   using WriterType = itk::ImageFileWriter<CharImageType>;
 
   using RescaleFilter =
-    itk::RescaleIntensityImageFilter<ImageType, CharImageType>;
+    itk::RescaleIntensityImageFilter<CharImageType, CharImageType>;
 
   using LaplacianSharpeningFilter =
-    itk::LaplacianSharpeningImageFilter<ImageType, ImageType>;
+    itk::LaplacianSharpeningImageFilter<CharImageType, CharImageType>;
 
 
   // Setting the IO

Modules/Filtering/ImageFeature/include/itkLaplacianSharpeningImageFilter.h

@@ -93,8 +93,6 @@ class ITK_TEMPLATE_EXPORT LaplacianSharpeningImageFilter : public ImageToImageFi
 #ifdef ITK_USE_CONCEPT_CHECKING
   // Begin concept checking
   itkConceptMacro(SameDimensionCheck, (Concept::SameDimension<InputImageDimension, ImageDimension>));
-  itkConceptMacro(InputPixelTypeIsFloatingPointCheck, (Concept::IsFloatingPoint<InputPixelType>));
-  itkConceptMacro(OutputPixelTypeIsFloatingPointCheck, (Concept::IsFloatingPoint<OutputPixelType>));
   // End concept checking
 #endif
 

Modules/Filtering/ImageFeature/include/itkLaplacianSharpeningImageFilter.hxx

@@ -69,10 +69,41 @@ LaplacianSharpeningImageFilter<TInputImage, TOutputImage>::GenerateData()
 
   using RealImageType = Image<RealType, ImageDimension>;
 
-  using LaplacianImageFilter = LaplacianImageFilter<InputImageType, RealImageType>;
-  typename LaplacianImageFilter::Pointer laplacianFilter = LaplacianImageFilter::New();
+  // Create the Laplacian operator
+  LaplacianOperator<RealType, ImageDimension> oper;
+  double                                      s[ImageDimension];
+  for (unsigned int i = 0; i < ImageDimension; ++i)
+  {
+    if (localInput->GetSpacing()[i] == 0.0)
+    {
+      itkExceptionMacro("Image spacing cannot be zero");
+    }
+    else if (this->m_UseImageSpacing)
+    {
+      s[i] = 1.0 / localInput->GetSpacing()[i];
+    }
+    else
+    {
+      s[i] = 1.0;
+    }
+  }
+  oper.SetDerivativeScalings(s);
+  oper.CreateOperator();
+  // Calculate the Laplacian filtered image
+
+  // do calculations in floating point
+  using RealImageType = Image<RealType, ImageDimension>;
+  using NOIF = NeighborhoodOperatorImageFilter<InputImageType, RealImageType>;
+  ZeroFluxNeumannBoundaryCondition<InputImageType> nbc;
+
+  auto laplacianFilter = NOIF::New();
+  laplacianFilter->OverrideBoundaryCondition(static_cast<typename NOIF::ImageBoundaryConditionPointerType>(&nbc));
+
+  //
+  // set up the mini-pipeline
+  //
+  laplacianFilter->SetOperator(oper);
   laplacianFilter->SetInput(localInput);
-  laplacianFilter->SetUseImageSpacing(m_UseImageSpacing);
   laplacianFilter->Update();
 
   auto filteredMinMaxFilter = MinimumMaximumImageFilter<RealImageType>::New();