text: //
  // Copyright 2005-2007 Adobe Systems Incorporated
  //
  // Distributed under the Boost Software License, Version 1.0
  // See accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt
  //
  #ifndef BOOST_GIL_EXTENSION_DYNAMIC_IMAGE_GIL_REDUCE_HPP
  #define BOOST_GIL_EXTENSION_DYNAMIC_IMAGE_GIL_REDUCE_HPP
  
  #ifdef BOOST_GIL_DOXYGEN_ONLY
  #undef BOOST_GIL_REDUCE_CODE_BLOAT
  #endif
  
  #ifdef BOOST_GIL_REDUCE_CODE_BLOAT
  
  #include <boost/gil/extension/dynamic_image/dynamic_at_c.hpp>
  
  #include <boost/gil/metafunctions.hpp>
  #include <boost/gil/typedefs.hpp>
  
  #include <boost/mpl/back.hpp>
  #include <boost/mpl/insert.hpp>
  #include <boost/mpl/insert_range.hpp>
  #include <boost/mpl/long.hpp>
  #include <boost/mpl/logical.hpp>
  #include <boost/mpl/range_c.hpp>
  #include <boost/mpl/vector.hpp>
  #include <boost/mpl/vector_c.hpp>
  #include <boost/mpl/transform.hpp>
  
  // Max number of cases in the cross-expension of binary operation for it to be reduced as unary
  #define GIL_BINARY_REDUCE_LIMIT 226
  
  namespace boost { namespace mpl {
  
  // Constructs for static-to-dynamic integer convesion
  
  ///////////////////////////////////////////////////////
  /// Mapping vector - represents the mapping of one type vector to another
  ///  It is not a full-blown MPL Random Access Type sequence; just has at_c and size implemented
  ///
  /// SrcTypes, DstTypes: MPL Random Access Type Sequences
  ///
  /// Implements size and at_c to behave as if this is an MPL vector of integers
  ///////////////////////////////////////////////////////
  
  template <typename SrcTypes, typename DstTypes>
  struct mapping_vector {};
  
  template <typename SrcTypes, typename DstTypes, long K>
  struct at_c<mapping_vector<SrcTypes,DstTypes>, K>
  {
      static const std::size_t value=size<DstTypes>::value - order<DstTypes, typename gil::at_c<SrcTypes,K>::type>::type::value +1;
      using type = size_t<value>;
  };
  
  template <typename SrcTypes, typename DstTypes>
  struct size<mapping_vector<SrcTypes,DstTypes>>
  {
      using type = typename size<SrcTypes>::type;
      static const std::size_t value=type::value;
  };
  
  ///////////////////////////////////////////////////////
  /// copy_to_vector - copies a sequence (mpl::set) to vector.
  ///
  /// Temporary solution because I couldn't get mpl::copy to do this.
  /// This is what I tried:
  /// mpl::copy<SET, mpl::back_inserter<mpl::vector<>>>::type;
  /// It works when SET is mpl::vector, but not when SET is mpl::set...
  ///////////////////////////////////////////////////////
  
  namespace detail {
      template <typename SFirst, std::size_t NLeft>
      struct copy_to_vector_impl {
      private:
          using T = typename deref<SFirst>::type;
          using next = typename next<SFirst>::type;
          using rest = typename copy_to_vector_impl<next, NLeft-1>::type;
      public:
          using type = typename push_front<rest, T>::type;
      };
  
      template <typename SFirst>
      struct copy_to_vector_impl<SFirst,1>
      {
          using type = vector<typename deref<SFirst>::type>;
      };
  }
  
  template <typename Src>
  struct copy_to_vector
  {
      using type = typename detail::copy_to_vector_impl<typename begin<Src>::type, size<Src>::value>::type;
  };
  
  template <>
  struct copy_to_vector<set<>>
  {
      using type = vector0<>;
  };
  
  } } // boost::mpl
  
  namespace boost { namespace gil {
  
  
  ///////////////////////////////////////////////////////
  ///
  /// unary_reduce, binary_reduce - given an MPL Random Access Sequence,
  /// dynamically specified index to that container, the bits of an instance of the corresponding type and
  /// a generic operation, invokes the operation on the given type
  ///
  ///////////////////////////////////////////////////////
  
  
  
  
  ///////////////////////////////////////////////////////
  ///
  /// \brief Unary reduce.
  ///
  /// Given a set of types and an operation, reduces each type in the set (to reduced_t), then removes duplicates (to unique_t)
  /// To apply the operation, first constructs a lookup table that maps each element from Types to its place in unique_t and uses it to map
  /// the index to anther index (in map_index). Then invokes apply_operation_base on the unique types with the new index.
  ///
  ///////////////////////////////////////////////////////
  
  template <typename Types, typename Op>
  struct unary_reduce_impl {
      using reduced_t = typename mpl::transform<Types, detail::reduce<Op, mpl::_1> >::type;
      using unique_t = typename mpl::copy<reduced_t, mpl::inserter<mpl::set<>, mpl::insert<mpl::_1,mpl::_2>>>::type;
      static const bool is_single=mpl::size<unique_t>::value==1;
  };
  
  template <typename Types, typename Op, bool IsSingle=unary_reduce_impl<Types,Op>::is_single>
  struct unary_reduce : public unary_reduce_impl<Types,Op>
  {
      using reduced_t = typename unary_reduce_impl<Types,Op>::reduced_t;
      using unique_t = typename unary_reduce_impl<Types,Op>::unique_t;
  
      static unsigned short inline map_index(std::size_t index)
      {
          using indices_t = typename mpl::mapping_vector<reduced_t, unique_t>;
          return gil::at_c<indices_t, unsigned short>(index);
      }
      template <typename Bits> BOOST_FORCEINLINE static typename Op::result_type applyc(const Bits& bits, std::size_t index, Op op) {
          return apply_operation_basec<unique_t>(bits,map_index(index),op);
      }
  
      template <typename Bits> BOOST_FORCEINLINE static typename Op::result_type apply(Bits& bits, std::size_t index, Op op) {
          return apply_operation_base<unique_t>(bits,map_index(index),op);
      }
  };
  
  template <typename Types, typename Op>
  struct unary_reduce<Types,Op,true> : public unary_reduce_impl<Types,Op> {
      using unique_t = typename unary_reduce_impl<Types,Op>::unique_t;
      static unsigned short inline map_index(std::size_t index) { return 0; }
  
      template <typename Bits> BOOST_FORCEINLINE static typename Op::result_type applyc(const Bits& bits, std::size_t index, Op op) {
          return op(*gil_reinterpret_cast_c<const typename mpl::front<unique_t>::type*>(&bits));
      }
  
      template <typename Bits> BOOST_FORCEINLINE static typename Op::result_type apply(Bits& bits, std::size_t index, Op op) {
          return op(*gil_reinterpret_cast<typename       mpl::front<unique_t>::type*>(&bits));
      }
  };
  
  
  ///////////////////////////////////////////////////////
  ///
  /// \brief Binary reduce.
  ///
  /// Given two sets of types, Types1 and Types2, first performs unary reduction on each. Then checks if the product of their sizes is above
  /// the GIL_BINARY_REDUCE_LIMIT limit. If so, the operation is too complex to be binary-reduced and uses a specialization of binary_reduce_impl
  /// to simply call the binary apply_operation_base (which performs two nested 1D apply operations)
  /// If the operation is not too complex, uses the other specialization of binary_reduce_impl to create a cross-product of the input types
  /// and performs unary reduction on the result (bin_reduced_t). To apply the binary operation, it simply invokes a unary apply_operation_base
  /// on the reduced cross-product types
  ///
  ///////////////////////////////////////////////////////
  
  namespace detail {
      struct pair_generator {
          template <typename Vec2> struct apply
          {
              using type = std::pair<const typename mpl::at_c<Vec2,0>::type*, const typename mpl::at_c<Vec2,1>::type*>;
          };
      };
  
      // When the types are not too large, applies reduce on their cross product
      template <typename Unary1, typename Unary2, typename Op, bool IsComplex>
      struct binary_reduce_impl
      {
      //private:
          using vec1_types = typename mpl::copy_to_vector<typename Unary1::unique_t>::type;
          using vec2_types = typename mpl::copy_to_vector<typename Unary2::unique_t>::type;
  
          using BIN_TYPES = mpl::cross_vector<mpl::vector2<vec1_types, vec2_types>, pair_generator>;
          using bin_reduced_t = unary_reduce<BIN_TYPES,Op>;
  
          static unsigned short inline map_index(std::size_t index1, std::size_t index2) {
              unsigned short r1=Unary1::map_index(index1);
              unsigned short r2=Unary2::map_index(index2);
              return bin_reduced_t::map_index(r2*mpl::size<vec1_types>::value + r1);
          }
      public:
          using unique_t = typename bin_reduced_t::unique_t
  
          template <typename Bits1, typename Bits2>
          static typename Op::result_type inline apply(const Bits1& bits1, std::size_t index1, const Bits2& bits2, std::size_t index2, Op op) {
              std::pair<const void*,const void*> pr(&bits1, &bits2);
              return apply_operation_basec<unique_t>(pr, map_index(index1,index2),op);
          }
      };
  
      // When the types are large performs a double-dispatch. Binary reduction is not done.
      template <typename Unary1, typename Unary2, typename Op>
      struct binary_reduce_impl<Unary1,Unary2,Op,true> {
          template <typename Bits1, typename Bits2>
          static typename Op::result_type inline apply(const Bits1& bits1, std::size_t index1, const Bits2& bits2, std::size_t index2, Op op) {
              return apply_operation_base<Unary1::unique_t,Unary2::unique_t>(bits1, index1, bits2, index2, op);
          }
      };
  }
  
  
  template <typename Types1, typename Types2, typename Op>
  struct binary_reduce
  {
  //private:
      using unary1_t = unary_reduce<Types1,Op>;
      using unary2_t = unary_reduce<Types2,Op>;
  
      static const std::size_t CROSS_SIZE = mpl::size<typename unary1_t::unique_t>::value *
                                            mpl::size<typename unary2_t::unique_t>::value;
  
      using impl = detail::binary_reduce_impl<unary1_t,unary2_t,Op, (CROSS_SIZE>GIL_BINARY_REDUCE_LIMIT)>;
  public:
      template <typename Bits1, typename Bits2>
      static typename Op::result_type inline apply(const Bits1& bits1, std::size_t index1, const Bits2& bits2, std::size_t index2, Op op) {
          return impl::apply(bits1,index1,bits2,index2,op);
      }
  };
  
  template <typename Types, typename UnaryOp>
  BOOST_FORCEINLINE typename UnaryOp::result_type apply_operation(variant<Types>& arg, UnaryOp op) {
      return unary_reduce<Types,UnaryOp>::template apply(arg._bits, arg._index ,op);
  }
  
  template <typename Types, typename UnaryOp>
  BOOST_FORCEINLINE typename UnaryOp::result_type apply_operation(const variant<Types>& arg, UnaryOp op) {
      return unary_reduce<Types,UnaryOp>::template applyc(arg._bits, arg._index ,op);
  }
  
  template <typename Types1, typename Types2, typename BinaryOp>
  BOOST_FORCEINLINE typename BinaryOp::result_type apply_operation(const variant<Types1>& arg1, const variant<Types2>& arg2, BinaryOp op) {
      return binary_reduce<Types1,Types2,BinaryOp>::template apply(arg1._bits, arg1._index, arg2._bits, arg2._index, op);
  }
  
  #undef GIL_BINARY_REDUCE_LIMIT
  
  } }  // namespace gil
  
  
  namespace boost { namespace mpl {
  ///////////////////////////////////////////////////////
  /// \brief Represents the virtual cross-product of the types generated from VecOfVecs.
  /// \ingroup CrossVector
  /// INPUT:
  ///   VecOfVecs - a vector of vector types. For example [ [A1,A2,A3], [B1,B2], [C1,C2,C3,C4] ]
  ///       Each element must be a non-empty mpl vector
  ///   TypeGen - a metafunction that generates a type from a vector of types, each of which can be
  ///       selected from the corresponding vector in VecOfVecs. For example, [A1, B2, C4]
  ///
  /// Represents the virtual cross-product of the types generated from VecOfVecs.
  /// For example, [ TypeGen[A1,B1,C1], TypeGen[A2,B1,C1], TypeGen[A3,B1,C1],
  ///                TypeGen[A1,B2,C1], TypeGen[A2,B2,C1], TypeGen[A3,B2,C1],
  ///                TypeGen[A1,B1,C2], TypeGen[A2,B1,C2], TypeGen[A3,B1,C2], ... ]
  ///
  /// Models an immutable MPL Random Access Sequence
  /// Traversal, random-access, etc, is defined, but mutable operations,
  ///  such as push_back and pop_front are not supported
  ///////////////////////////////////////////////////////
  
  template <typename VecOfVecs, typename TypeGen>
  struct cross_vector {};
  
  /// \brief Iterator of cross_vector
  /// \ingroup CrossVectorIterator
  template <typename VecOfVecs, typename TypeGen, std::size_t K>
  struct cross_iterator
  {
      using category = mpl::random_access_iterator_tag;
  };
  
  ///////////////////////////////////////////////////////
  /// Implementation of the iterator functions of cross vector
  ///////////////////////////////////////////////////////
  
  /// \brief Dereferences a cross-vector iterator
  /// \ingroup CrossVectorIterator
  /// Creates a vector of the sizes of each type vector in VecOfVecs, then uses it as a basis
  /// to represent the iterator's position K as a vector of indices. Extracts the corresponding type of
  /// each input vector and passes the element types to the type generation function, which returns the dereferenced type
  template <typename VecOfVecs, typename TypeGen, std::size_t K>
  struct deref<cross_iterator<VecOfVecs,TypeGen,K>>
  {
  private:
      using DerefTypes = typename detail::select_subvector_c<VecOfVecs, K>::type;
  public:
      using type = typename TypeGen::template apply<DerefTypes>::type;
  };
  
  /// \brief Increments a cross-vector iterator.
  /// \ingroup CrossVectorIterator
  template <typename VecOfVecs, typename TypeGen, std::size_t K>
  struct next<cross_iterator<VecOfVecs,TypeGen,K>>
  {
      using type = cross_iterator<VecOfVecs,TypeGen,K+1>;
  };
  
  /// \brief Decrements a cross-vector iterator.
  /// \ingroup CrossVectorIterator
  template <typename VecOfVecs, typename TypeGen, std::size_t K>
  struct prior<cross_iterator<VecOfVecs,TypeGen,K>>
  {
      using type = cross_iterator<VecOfVecs,TypeGen,K-1>;
  };
  
  /// \brief Advances a cross-vector iterator.
  /// \ingroup CrossVectorIterator
  template <typename VecOfVecs, typename TypeGen, std::size_t K, typename Distance>
  struct advance<cross_iterator<VecOfVecs,TypeGen,K>, Distance>
  {
      using type = cross_iterator<VecOfVecs,TypeGen,K+Distance::value>;
  };
  
  /// \brief Computes the distance between two cross-vector iterator-s.
  /// \ingroup CrossVectorIterator
  // (shortened the names of the template arguments - otherwise doxygen cannot parse this...)
  template <typename VecOfVecs, typename TypeGen, std::size_t K1, std::size_t K2>
  struct distance<cross_iterator<VecOfVecs,TypeGen,K1>, cross_iterator<VecOfVecs,TypeGen,K2>>
  {
      using type = size_t<K2-K1>;
  };
  
  ///////////////////////////////////////////////////////
  /// Implementation of cross vector
  ///////////////////////////////////////////////////////
  /// \brief Computes the size of a cross vector as the product of the sizes of all vectors in VecOfVecs
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen>
  struct size<cross_vector<VecOfVecs,TypeGen>>
  {
      using type = typename fold<VecOfVecs, size_t<1>, times<_1, size<_2>>>::type;
      static const std::size_t value=type::value;
  };
  
  /// \brief Determines whether a cross vector is empty
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen>
  struct empty<cross_vector<VecOfVecs,TypeGen>> {
      using type = typename empty<VecOfVecs>::type;
  };
  
  /// \brief Returns the K-th element of a cross vector
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen, typename K>
  struct at<cross_vector<VecOfVecs,TypeGen>, K>
  {
  private:
      using KthIterator = cross_iterator<VecOfVecs,TypeGen,K::value>;
  public:
      using type = typename deref<KthIterator>::type;
  };
  
  /// \brief Returns an iterator to the first element of a cross vector
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen>
  struct begin<cross_vector<VecOfVecs,TypeGen>>
  {
      using type = cross_iterator<VecOfVecs,TypeGen,0>;
  };
  
  /// \brief Returns an iterator to the last element of a cross vector
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen>
  struct end<cross_vector<VecOfVecs,TypeGen>>
  {
  private:
      using this_t = cross_vector<VecOfVecs,TypeGen>;
  public:
      using type = cross_iterator<VecOfVecs,TypeGen,size<this_t>::value>;
  };
  
  /// \brief Returns the first element of a cross vector
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen>
  struct front<cross_vector<VecOfVecs,TypeGen>> {
  private:
      using this_t = cross_vector<VecOfVecs,TypeGen>;
  public:
      using type = typename deref<typename begin<this_t>::type>::type;
  };
  
  /// \brief Returns the last element of a cross vector
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen>
  struct back<cross_vector<VecOfVecs,TypeGen>>
  {
  private:
      using this_t = cross_vector<VecOfVecs,TypeGen>;
      using size = typename size<this_t>::type;
      using last_index = typename minus<size, size_t<1>>::type;
  public:
      using type = typename at<this_t, last_index>::type;
  };
  
  /// \brief Transforms the elements of a cross vector
  /// \ingroup CrossVector
  template <typename VecOfVecs, typename TypeGen, typename OPP>
  struct transform<cross_vector<VecOfVecs,TypeGen>, OPP>
  {
      using Op = typename lambda<OPP>::type;
      struct adapter
      {
          template <typename Elements>
          struct apply
          {
              using orig_t = typename TypeGen::template apply<Elements>::type;
              using type = typename Op::template apply<orig_t>::type;
          };
      };
      using type = cross_vector<VecOfVecs, adapter>;
  };
  
  } } // boost::mpl
  
  namespace boost { namespace gil {
  
  template <typename Types, typename T> struct type_to_index;
  template <typename V> struct view_is_basic;
  struct rgb_t;
  struct lab_t;
  struct hsb_t;
  struct cmyk_t;
  struct rgba_t;
  struct error_t;
  
  
  namespace detail {
      ////////////////////////////////////////////////////////
      ////
      ////   Generic reduce operation
      ////
      ////////////////////////////////////////////////////////
      template <typename Op, typename T>
      struct reduce
      {
          using type = T;
      };
  
      ////////////////////////////////////////////////////////
      ////
      ////   Unary reduce_view operation. Splits into basic and non-basic views.
      ////   Algorithm-specific reduce should specialize for basic views
      ////
      ////////////////////////////////////////////////////////
  
      template <typename Op, typename View, bool IsBasic>
      struct reduce_view_basic
      {
          using type = View;
      };
  
      template <typename Op, typename Loc>
      struct reduce<Op, image_view<Loc>>
          : public reduce_view_basic<Op,image_view<Loc>,view_is_basic<image_view<Loc>>::value> {};
  
      ////////////////////////////////////////////////////////
      ////
      ////   Unary reduce_image operation. Splits into basic and non-basic images.
      ////   Algorithm-specific reduce should specialize for basic images
      ////
      ////////////////////////////////////////////////////////
  
      template <typename Op, typename Img, bool IsBasic>
      struct reduce_image_basic
      {
          using type = Img;
      };
  
      template <typename Op, typename V, typename Alloc>
      struct reduce<Op, image<V,Alloc>> : public reduce_image_basic<Op,image<V,Alloc>,image_is_basic<image<V,Alloc>>::value > {};
  
      ////////////////////////////////////////////////////////
      ////
      ////   Binary reduce_view operation. Splits into basic and non-basic views.
      ////   Algorithm-specific reduce should specialize for basic views
      ////
      ////////////////////////////////////////////////////////
  
      template <typename Op, typename V1, typename V2, bool AreBasic>
      struct reduce_views_basic
      {
          using type = std::pair<const V1*, const V2*>;
      };
  
      template <typename Op, typename L1, typename L2>
      struct reduce<Op, std::pair<const image_view<L1>*, const image_view<L2>*>>
          : public reduce_views_basic<Op,image_view<L1>,image_view<L2>,
                   mpl::and_<view_is_basic<image_view<L1>>, view_is_basic<image_view<L2>>>::value >
      {};
  
  
      ////////////////////////////////////////////////////////
      ////
      ////   Color space unary reduce operation. Reduce a color space to a base with the same number of channels
      ////
      ////////////////////////////////////////////////////////
  
      template <typename CS>
      struct reduce_color_space
      {
          using type = CS;
      };
  
      template <> struct reduce_color_space<lab_t> { using type = rgb_t; };
      template <> struct reduce_color_space<hsb_t> { using type = rgb_t; };
      template <> struct reduce_color_space<cmyk_t> { using type = rgba_t; };
  
      /*
      ////////////////////////////////////////////////////////
      ////
      ////   Color space binary reduce operation. Given a source and destination color spaces,
      ////   returns a reduced source and destination color spaces that have the same mapping of channels
      ////
      ////   Precondition: The two color spaces must be compatible (i.e. must have the same set of channels)
      ////////////////////////////////////////////////////////
  
      template <typename Vec, int Basis, int VecSize>
      struct type_vec_to_integer_impl {
          using last = typename mpl::back<Vec>::type;
          using rest = typename mpl::pop_back<Vec>::type;
          static const int value = type_vec_to_integer_impl<rest, Basis, VecSize-1>::value * Basis + last::value;
      };
  
      template <typename Vec, int Basis>
      struct type_vec_to_integer_impl<Vec,Basis,0> {
          static const int value=0;
      };
  
      template <typename Vec, int Basis=10>
      struct type_vec_to_integer {
          static const int value = type_vec_to_integer_impl<Vec,Basis, mpl::size<Vec>::value>::value;
      };
  
      // Given two color spaces and the mapping of the channels between them, returns the reduced pair of color spaces
      // The default version performs no reduction
      template <typename SrcColorSpace, typename DstColorSpace, int Mapping>
      struct reduce_color_spaces_impl {
          using first_t = SrcColorSpace;
          using second_t = DstColorSpace;
      };
  
      // 012: RGB-RGB, bgr-bgr, lab-lab, hsb-hsb
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,12> {
          using first_t = rgb_t;
          using second_t = rgb_t;
      };
  
      // 210: RGB-bgr, bgr-RGB
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,210> {
          using first_t = rgb_t;
          using second_t = bgr_t;
      };
  
      // 0123: RGBA-RGBA, bgra-bgra, argb-argb, abgr-abgr cmyk-cmyk
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,123> {
          using first_t = rgba_t;
          using second_t = rgba_t;
      };
  
      // 3210: RGBA-abgr, bgra-argb, argb-bgra, abgr-RGBA
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,3210> {
          using first_t = rgba_t;
          using second_t = abgr_t;
      };
  
      // 1230: RGBA-argb, bgra-abgr
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,1230> {
          using first_t = rgba_t;
          using second_t = argb_t;
      };
  
      // 2103: RGBA-bgra, bgra-RGBA (uses subclass to ensure that base color space is not reduced to derived)
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,2103> {
          using first_t = rgba_t;
          using second_t = bgra_t;
      };
  
      // 3012: argb-RGBA, abgr-bgra
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,3012> {
          using first_t = argb_t;
          using second_t = rgba_t;
      };
  
      // 0321: argb-abgr, abgr-argb
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,321> {
          using first_t = argb_t;
          using second_t = abgr_t;
      };
  
      template <typename SrcColorSpace, typename DstColorSpace>
      struct reduce_color_spaces {
          using src_order_t = typename channel_order<SrcColorSpace>::type;
          using dst_order_t = typename channel_order<DstColorSpace>::type;
          using mapping = typename mpl::transform<src_order_t, type_to_index<dst_order_t,mpl::_1>>::type;
          static const int mapping_val = type_vec_to_integer<mapping>::value;
  
          using _first_t = typename reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,mapping_val>::first_t;
          using _second_t = typename reduce_color_spaces_impl<SrcColorSpace,DstColorSpace,mapping_val>::second_t;
          using swap_t = typename mpl::and_<color_space_is_base<DstColorSpace>, mpl::not_< color_space_is_base<_second_t>>>;
      public:
          using first_t = typename mpl::if_<swap_t, _second_t, _first_t>::type;
          using second_t = typename mpl::if_<swap_t, _first_t, _second_t>::type;
      };
  */
  // TODO: Use the old code for reduce_color_spaces above to do color layout reduction
      template <typename SrcLayout, typename DstLayout>
      struct reduce_color_layouts
      {
          using first_t = SrcLayout;
          using second_t = DstLayout;
      };
  
      ////////////////////////////////////////////////////////
      ////
      ////   Reduce for copy_pixels
      ////
      ////////////////////////////////////////////////////////
  
      struct copy_pixels_fn;
  
      /*
      // 1D reduce for copy_pixels reduces the channel to mutable and the color space to its base with same dimensions
      template <typename View>
      struct reduce_view_basic<copy_pixels_fn,View,true> {
      private:
          using color_space_t = typename reduce_color_space<typename View::color_space_t>::type color_space_t; // reduce the color space
          using layout_t = layout<color_space_t, typename View::channel_mapping_t>;
      public:
          using type = typename derived_view_type<View, use_default, layout_t, use_default, use_default, mpl::true_>::type;
      };
  */
      // Incompatible views cannot be used in copy_pixels - will throw std::bad_cast
      template <typename V1, typename V2, bool Compatible>
      struct reduce_copy_pixop_compat
      {
          using type = error_t;
      };
  
      // For compatible basic views, reduce their color spaces based on their channel mapping.
      // Make the source immutable and the destination mutable (they should already be that way)
      template <typename V1, typename V2>
      struct reduce_copy_pixop_compat<V1,V2,true>
      {
          using layout1 = layout<typename V1::color_space_t, typename V1::channel_mapping_t>;
          using layout2 = layout<typename V2::color_space_t, typename V2::channel_mapping_t>;
  
          using L1 = typename reduce_color_layouts<layout1,layout2>::first_t;
          using L2 = typename reduce_color_layouts<layout1,layout2>::second_t;
  
          using DV1 = typename derived_view_type<V1, use_default, L1, use_default, use_default, use_default, mpl::false_>::type;
          using DV2 = typename derived_view_type<V2, use_default, L2, use_default, use_default, use_default, mpl::true_ >::type;
  
          using type = std::pair<const DV1*, const DV2*>;
      };
  
      // The general 2D version branches into compatible and incompatible views
      template <typename V1, typename V2>
      struct reduce_views_basic<copy_pixels_fn, V1, V2, true>
          : public reduce_copy_pixop_compat<V1, V2, mpl::and_<views_are_compatible<V1,V2>, view_is_mutable<V2>>::value > {
      };
  
      ////////////////////////////////////////////////////////
      ////
      ////   Reduce for variant destructor (basic views have no destructor)
      ////
      ////////////////////////////////////////////////////////
  
      struct destructor_op;
      template <typename View>
      struct reduce_view_basic<destructor_op,View,true>
      {
          using type = gray8_view_t;
      };
  
      ////////////////////////////////////////////////////////
      ////
      ////   Reduce for get_dimensions (basic views and images have the same structure and the dimensions are contained at the beginning)
      ////
      ////////////////////////////////////////////////////////
  
      struct any_type_get_dimensions;
  
      template <typename View>
      struct reduce_view_basic<any_type_get_dimensions,View,true>
      {
          using type = gray8_view_t;
      };
  
      template <typename Img>
      struct reduce_image_basic<any_type_get_dimensions,Img,true>
      {
          using type = gray8_image_t;
      };
  
      ////////////////////////////////////////////////////////
      ////
      ////   Reduce for get_num_channels (only color space matters)
      ////
      ////////////////////////////////////////////////////////
  
      struct any_type_get_num_channels;
  
      template <typename View>
      struct reduce_view_basic<any_type_get_num_channels,View,true>
      {
          using color_space_t =  typename View::color_space_t::base;
          using type = typename view_type<uint8_t,typename reduce_color_space<color_space_t>::type>::type;
      };
  
      template <typename Img>
      struct reduce_image_basic<any_type_get_num_channels,Img,true>
      {
          using color_space_t = typename Img::color_space_t::base;
          using type = typename image_type<uint8_t,typename reduce_color_space<color_space_t>::type>::type;
      };
  
      ////////////////////////////////////////////////////////
      ////
      ////   Reduce for resample_pixels (same as copy_pixels)
      ////
      ////////////////////////////////////////////////////////
  
      template <typename Sampler, typename MapFn> struct resample_pixels_fn;
  
      template <typename S, typename M, typename V, bool IsBasic>
      struct reduce_view_basic<resample_pixels_fn<S,M>, V, IsBasic> : public reduce_view_basic<copy_pixels_fn, V, IsBasic> {};
  
      template <typename S, typename M, typename V1, typename V2, bool IsBasic>
      struct reduce_views_basic<resample_pixels_fn<S,M>, V1, V2, IsBasic> : public reduce_views_basic<copy_pixels_fn, V1, V2, IsBasic> {};
  
      ////////////////////////////////////////////////////////
      ////
      ////   Reduce for copy_and_convert_pixels
      ////   (the only reduction could be made when views are compatible and have the same mapping, planarity and stepness)
      ////
      ////////////////////////////////////////////////////////
  
  
      template <typename CC> class copy_and_convert_pixels_fn;
  
      // the only thing for 1D reduce is making them all mutable...
      template <typename CC, typename View, bool IsBasic>
      struct reduce_view_basic<copy_and_convert_pixels_fn<CC>, View, IsBasic>
          : public derived_view_type<View, use_default, use_default, use_default, use_default, mpl::true_> {
      };
  
      // For 2D reduce, if they have the same channels and color spaces (i.e. the same pixels) then copy_and_convert is just copy.
      // In this case, reduce their common color space. In general make the first immutable and the second mutable
      template <typename CC, typename V1, typename V2, bool AreBasic>
      struct reduce_views_basic<copy_and_convert_pixels_fn<CC>, V1, V2, AreBasic>
      {
          using Same = is_same<typename V1::pixel_t, typename V2::pixel_t>;
  
          using CsR = reduce_color_space<typename V1::color_space_t::base>;
          using Cs1 = typename mpl::if_<Same, typename CsR::type, typename V1::color_space_t>::type;
          using Cs2 = typename mpl::if_<Same, typename CsR::type, typename V2::color_space_t>::type;
  
          using DV1 = typename derived_view_type<V1, use_default, layout<Cs1, typename V1::channel_mapping_t>, use_default, use_default, mpl::false_>::type;
          using DV2 = typename derived_view_type<V2, use_default, layout<Cs2, typename V2::channel_mapping_t>, use_default, use_default, mpl::true_ >::type;
  
          using type = std::pair<const DV1*, const DV2*>;
      };
  
  
      //integral_image_generator
      //resize_clobber_image_fnobj
      //image_default_construct_fnobj
      //fill_converted_pixels_fn
      //std::bind(gil::detail::copy_pixels_fn(), std::placeholders::_1, dst)
      //std::bind(gil::detail::copy_pixels_fn(), src, std::placeholders::_1)
  
      //std::bind(detail::copy_and_convert_pixels_fn(), std::placeholders::_1, dst)
      //std::bind(detail::copy_and_convert_pixels_fn(), src, std::placeholders::_1)
      //gil::detail::fill_pixels_fn<Value>(val)
  
      //detail::copy_construct_in_place_fn<base_t>
      //detail::equal_to_fn<typename variant<Types>::base_t>
  
      //detail::any_image_get_view<typename any_image<Types>::view_t>
      //detail::any_image_get_const_view<typename any_image<Types>::view_t>
      //detail::flipped_up_down_view_fn<any_image_view<ViewTypes>>
      //detail::flipped_left_right_view_fn<typename any_image_view<ViewTypes>::dynamic_step_t>
      //detail::tranposed_view_fn<typename any_image_view<ViewTypes>::dynamic_step_t>
      //detail::rotated90cw_view_fn<typename any_image_view<ViewTypes>::dynamic_step_t>
      //detail::rotated90ccw_view_fn<typename any_image_view<ViewTypes>::dynamic_step_t>
      //detail::rotated180_view_fn<typename any_image_view<ViewTypes>::dynamic_step_t>
      //detail::subimage_view_fn<any_image_view<ViewTypes>>
      //detail::subsampled_view_fn<typename any_image_view<ViewTypes>::dynamic_step_t>
      //detail::nth_channel_view_fn<typename nth_channel_view_type<any_image_view<ViewTypes>>
      //detail::color_converted_view_fn<DstP,typename color_convert_view_type<any_image_view<ViewTypes>, DstP>::type >
  }
  
  }}  // namespace boost::gil
  
  #endif // defined(BOOST_GIL_REDUCE_CODE_BLOAT)
  
  #endif
  