ENH: Add default factory initialization

Leverages the `InitFactory` mechanism introduced in ITK commit c266651
to register VkFFT GPU-accelerated implementation classes as the default
backends for ITK FFT classes via the object factory.

include/itkVkComplexToComplexFFTImageFilter.h

@@ -127,6 +127,7 @@ struct FFTImageFilterTraits<VkComplexToComplexFFTImageFilter>
   using InputPixelType = std::complex<TUnderlying>;
   template <typename TUnderlying>
   using OutputPixelType = std::complex<TUnderlying>;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

include/itkVkFFTImageFilterInitFactory.h

@@ -0,0 +1,74 @@
+/*=========================================================================
+ *
+ *  Copyright NumFOCUS
+ *
+ *  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 itkVkFFTImageFilterInitFactory_h
+#define itkVkFFTImageFilterInitFactory_h
+#include "VkFFTBackendExport.h"
+
+#include "itkLightObject.h"
+
+namespace itk
+{
+/**
+ *\class VkFFTImageFilterInitFactory
+ * \brief Initialize Vk FFT image filter factory backends.
+ *
+ * The purpose of VkFFTImageFilterInitFactory is to perform
+ * one-time registration of factory objects that handle
+ * creation of Vk-backend FFT image filter classes
+ * through the ITK object factory singleton mechanism.
+ *
+ * \ingroup FourierTransform
+ * \ingroup ITKFFT
+ * \ingroup ITKSystemObjects
+ * \ingroup VkFFTBackend
+ */
+class VkFFTBackend_EXPORT VkFFTImageFilterInitFactory : public LightObject
+{
+public:
+  ITK_DISALLOW_COPY_AND_MOVE(VkFFTImageFilterInitFactory);
+
+  /** Standard class type aliases. */
+  using Self = VkFFTImageFilterInitFactory;
+  using Superclass = LightObject;
+  using Pointer = SmartPointer<Self>;
+  using ConstPointer = SmartPointer<const Self>;
+
+  /** Method for class instantiation. */
+  itkFactorylessNewMacro(Self);
+
+  /** Run-time type information (and related methods). */
+  itkTypeMacro(VkFFTImageFilterInitFactory, LightObject);
+
+  /** Mimic factory interface for Python initialization  */
+  static void
+  RegisterOneFactory()
+  {
+    RegisterFactories();
+  }
+
+  /** Register all Vk FFT factories */
+  static void
+  RegisterFactories();
+
+protected:
+  VkFFTImageFilterInitFactory();
+  ~VkFFTImageFilterInitFactory() override = default;
+};
+} // end namespace itk
+
+#endif

include/itkVkForward1DFFTImageFilter.h

@@ -134,6 +134,7 @@ struct FFTImageFilterTraits<VkForward1DFFTImageFilter>
   using InputPixelType = TUnderlying;
   template <typename TUnderlying>
   using OutputPixelType = std::complex<TUnderlying>;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

include/itkVkForwardFFTImageFilter.h

@@ -132,6 +132,7 @@ struct FFTImageFilterTraits<VkForwardFFTImageFilter>
   using InputPixelType = TUnderlying;
   template <typename TUnderlying>
   using OutputPixelType = std::complex<TUnderlying>;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

include/itkVkHalfHermitianToRealInverseFFTImageFilter.h

@@ -133,6 +133,7 @@ struct FFTImageFilterTraits<VkHalfHermitianToRealInverseFFTImageFilter>
   using InputPixelType = std::complex<TUnderlying>;
   template <typename TUnderlying>
   using OutputPixelType = TUnderlying;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

include/itkVkInverse1DFFTImageFilter.h

@@ -135,6 +135,7 @@ struct FFTImageFilterTraits<VkInverse1DFFTImageFilter>
   using InputPixelType = std::complex<TUnderlying>;
   template <typename TUnderlying>
   using OutputPixelType = TUnderlying;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

include/itkVkInverseFFTImageFilter.h

@@ -132,6 +132,7 @@ struct FFTImageFilterTraits<VkInverseFFTImageFilter>
   using InputPixelType = std::complex<TUnderlying>;
   template <typename TUnderlying>
   using OutputPixelType = TUnderlying;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

include/itkVkRealToHalfHermitianForwardFFTImageFilter.h

@@ -133,6 +133,7 @@ struct FFTImageFilterTraits<VkRealToHalfHermitianForwardFFTImageFilter>
   using InputPixelType = TUnderlying;
   template <typename TUnderlying>
   using OutputPixelType = std::complex<TUnderlying>;
+  using FilterDimensions = std::integer_sequence<unsigned int, 3, 2, 1>;
 };
 
 } // namespace itk

itk-module.cmake

@@ -25,6 +25,8 @@ itk_module(VkFFTBackend
     ITKImageIntensity
   DESCRIPTION
     "${DOCUMENTATION}"
+  FACTORY_NAMES
+    "FFTImageFilterInit::Vk"
   EXCLUDE_FROM_DEFAULT
   ENABLE_SHARED
 )

src/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(VkFFTBackend_SRCS
   itkVkCommon.cxx
   itkVkGlobalConfiguration.cxx
+  itkVkFFTImageFilterInitFactory.cxx
   )
 
 itk_module_add_library(VkFFTBackend ${VkFFTBackend_SRCS})

src/itkVkFFTImageFilterInitFactory.cxx

@@ -0,0 +1,67 @@
+/*=========================================================================
+ *
+ *  Copyright NumFOCUS
+ *
+ *  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.
+ *
+ *=========================================================================*/
+#include "ITKFFTExport.h"
+
+#include "itkVkComplexToComplex1DFFTImageFilter.h"
+#include "itkVkComplexToComplexFFTImageFilter.h"
+#include "itkFFTImageFilterFactory.h"
+#include "itkVkForward1DFFTImageFilter.h"
+#include "itkVkForwardFFTImageFilter.h"
+#include "itkVkHalfHermitianToRealInverseFFTImageFilter.h"
+#include "itkVkInverse1DFFTImageFilter.h"
+#include "itkVkInverseFFTImageFilter.h"
+#include "itkVkRealToHalfHermitianForwardFFTImageFilter.h"
+
+#include "itkVkFFTImageFilterInitFactory.h"
+
+namespace itk
+{
+VkFFTImageFilterInitFactory::VkFFTImageFilterInitFactory()
+{
+  VkFFTImageFilterInitFactory::RegisterFactories();
+}
+
+void VkFFTImageFilterInitFactory::RegisterFactories()
+{
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkComplexToComplex1DFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkComplexToComplexFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkForward1DFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkForwardFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkHalfHermitianToRealInverseFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkInverse1DFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkInverseFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+  itk::ObjectFactoryBase::RegisterFactory(FFTImageFilterFactory<VkRealToHalfHermitianForwardFFTImageFilter>::New(),
+                                          itk::ObjectFactoryEnums::InsertionPosition::INSERT_AT_FRONT);
+}
+
+// Undocumented API used to register during static initialization.
+// DO NOT CALL DIRECTLY.
+void VkFFTBackend_EXPORT
+VkFFTImageFilterInitFactoryRegister__Private()
+{
+  VkFFTImageFilterInitFactory::RegisterFactories();
+}
+
+} // end namespace itk

test/itkVkFFTImageFilterFactoryTest.cxx

@@ -22,6 +22,7 @@
 #include "itkComplexToComplex1DFFTImageFilter.h"
 #include "itkVkComplexToComplex1DFFTImageFilter.h"
 #include "itkVnlComplexToComplex1DFFTImageFilter.h"
+#include "itkVkFFTImageFilterInitFactory.h"
 
 #include "itkFFTImageFilterFactory.h"
 #include "itkTestingMacros.h"
@@ -63,5 +64,15 @@ itkVkFFTImageFilterFactoryTest(int, char *[])
   ITK_TEST_EXPECT_TRUE(vnlFFT != nullptr);
   ITK_EXERCISE_BASIC_OBJECT_METHODS(vnlFFT, VnlComplexToComplex1DFFTImageFilter, ComplexToComplex1DFFTImageFilter);
 
+  // Verify factory initialization successfully registers factories
+  using FactoryInitializerType = itk::VkFFTImageFilterInitFactory;
+  FactoryInitializerType::RegisterFactories();
+
+  fft = FFTBaseType::New();
+  vkFFT = dynamic_cast<FFTVkSubclassType *>(fft.GetPointer());
+  ITK_TEST_EXPECT_TRUE(vkFFT != nullptr);
+  ITK_EXERCISE_BASIC_OBJECT_METHODS(vkFFT, VkComplexToComplex1DFFTImageFilter, ComplexToComplex1DFFTImageFilter);
+
+
   return EXIT_SUCCESS;
 }

wrapping/itkVkFFTImageFilterInitFactory.wrap

@@ -0,0 +1 @@
+itk_wrap_simple_class("itk::VkFFTImageFilterInitFactory" POINTER)