WIP: ENH: add backprojection for super short scan

include/rtkSuperShortScanBackProjectionImageFilter.h

@@ -0,0 +1,92 @@
+/*=========================================================================
+ *
+ *  Copyright RTK 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 rtkSuperShortScanBackProjectionImageFilter_h
+#define rtkSuperShortScanBackProjectionImageFilter_h
+
+#include "rtkBackProjectionImageFilter.h"
+
+namespace rtk
+{
+
+/** \class SuperShortScanBackProjectionImageFilter
+ * \brief CPU version of the backprojection of the SuperShortScan algorithm.
+ *
+ * CPU implementation of the backprojection step of the
+ * [Feldkamp, Davis, Kress, 1984] algorithm for filtered backprojection
+ * reconstruction of cone-beam CT images with a circular source trajectory.
+ *
+ * \author Simon Rit
+ *
+ * \ingroup RTK Projector
+ */
+template <class TInputImage, class TOutputImage>
+class ITK_EXPORT SuperShortScanBackProjectionImageFilter : public BackProjectionImageFilter<TInputImage, TOutputImage>
+{
+public:
+  ITK_DISALLOW_COPY_AND_ASSIGN(SuperShortScanBackProjectionImageFilter);
+
+  /** Standard class type alias. */
+  using Self = SuperShortScanBackProjectionImageFilter;
+  using Superclass = BackProjectionImageFilter<TInputImage, TOutputImage>;
+  using Pointer = itk::SmartPointer<Self>;
+  using ConstPointer = itk::SmartPointer<const Self>;
+
+  using ProjectionMatrixType = typename Superclass::ProjectionMatrixType;
+  using OutputImageRegionType = typename TOutputImage::RegionType;
+  using ProjectionImageType = typename Superclass::ProjectionImageType;
+  using ProjectionImagePointer = typename ProjectionImageType::Pointer;
+
+  /** Method for creation through the object factory. */
+  itkNewMacro(Self);
+
+  /** Run-time type information (and related methods). */
+  itkTypeMacro(SuperShortScanBackProjectionImageFilter, ImageToImageFilter);
+
+protected:
+  SuperShortScanBackProjectionImageFilter() = default;
+  ~SuperShortScanBackProjectionImageFilter() override = default;
+
+  void
+  GenerateOutputInformation() override;
+
+  void
+  DynamicThreadedGenerateData(const OutputImageRegionType & outputRegionForThread) override;
+
+  /** Optimized version when the rotation is parallel to X, i.e. matrix[1][0]
+    and matrix[2][0] are zeros. */
+  void
+  OptimizedBackprojectionX(const OutputImageRegionType & region,
+                           const ProjectionMatrixType &  matrix,
+                           const ProjectionImagePointer  projection) override;
+
+  /** Optimized version when the rotation is parallel to Y, i.e. matrix[1][1]
+    and matrix[2][1] are zeros. */
+  void
+  OptimizedBackprojectionY(const OutputImageRegionType & region,
+                           const ProjectionMatrixType &  matrix,
+                           const ProjectionImagePointer  projection) override;
+};
+
+} // end namespace rtk
+
+#ifndef ITK_MANUAL_INSTANTIATION
+#  include "rtkSuperShortScanBackProjectionImageFilter.hxx"
+#endif
+
+#endif