ENH: Add template using to ease the retrieval of input image types

Modules/Core/Functor/include/otbFunctorImageFilter.h

@@ -209,7 +209,9 @@ public:
   // the functor
   using InputHasNeighborhood = typename FunctorFilterSuperclassHelper<TFunction>::InputHasNeighborhood;
   using InputTypesTupleType = typename Superclass::InputTypesTupleType;
- 
+  template<size_t I> using InputImageType = typename Superclass::template InputImageType<I>;
+
+  
   /** Run-time type information (and related methods). */
   itkTypeMacro(FunctorImageFilter, ImageToImageFilter);
   

Modules/Core/Functor/include/otbVariadicInputsImageFilter.h

@@ -33,16 +33,18 @@ public:
   using Pointer =  itk::SmartPointer<Self>;
   using ConstPointer = itk::SmartPointer<const Self>;
   using Superclass = itk::ImageSource<TOuptut>;
-
+  
   using InputTypesTupleType = std::tuple<TInputs...>;
-
+  
+  template <size_t I> using InputImageType = typename std::tuple_element<I,InputTypesTupleType>::type;
+  
   itkNewMacro(Self);
   
   template <std::size_t I> void SetVInput(const typename std::tuple_element<I,InputTypesTupleType>::type * inputPtr)
   {
     this->SetNthInput(I,const_cast<typename std::tuple_element<I,InputTypesTupleType>::type *>(inputPtr));
   }
-
+  
 #define DefineLegacySetInputMacro(n)                                                                               \
   template<typename Tuple = InputTypesTupleType, typename Check = typename std::enable_if<n<=std::tuple_size<Tuple>::value >::type> \
   void SetInput ## n(const typename std::tuple_element<n-1,Tuple>::type * img)                                           \

Modules/Core/Functor/test/otbFunctorImageFilter.cxx

@@ -101,7 +101,7 @@ template <typename T> struct TypesCheck
   auto filter = NewFunctorFilter(functor);
 
   using FilterType = typename decltype(filter)::ObjectType;
-  static_assert(std::is_same<typename std::tuple_element<0, typename FilterType::Superclass::InputTypesTupleType>::type, InputImageType>::value, "");
+  static_assert(std::is_same<typename FilterType::template InputImageType<0>, InputImageType>::value, "");
 
   filter->SetVInputs(in);
   filter->SetInput1(in);