gil_concept.hpp

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/*
    Copyright 2005-2007 Adobe Systems Incorporated
   
    Use, modification and distribution are subject to 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).

    See http://opensource.adobe.com/gil for most recent version including documentation.
*/

/*************************************************************************************************/

#ifndef GIL_CONCEPT_H
#define GIL_CONCEPT_H


#include <functional>
#include "gil_config.hpp"
#include <boost/type_traits.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/concept_check.hpp>
#include <boost/iterator/iterator_concepts.hpp>
#include <boost/mpl/and.hpp>
#include <boost/mpl/size.hpp>

namespace boost { namespace gil {

#if defined(__GNUC__) && (__GNUC__ >= 4)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-local-typedefs"
#endif

#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) 
#pragma warning(push) 
#pragma warning(disable:4510) //default constructor could not be generated
#pragma warning(disable:4512) //assignment operator could not be generated
#pragma warning(disable:4610) //can never be instantiated - user defined constructor required
#endif

template <typename T> struct channel_traits;
template <typename P> struct is_pixel;
template <typename dstT, typename srcT>
typename channel_traits<dstT>::value_type channel_convert(const srcT& val);
template <typename T> class point2;
template <std::size_t K, typename T> const T& axis_value(const point2<T>& p);
template <std::size_t K, typename T>       T& axis_value(      point2<T>& p);
template <typename ColorBase, int K> struct kth_element_type;
template <typename ColorBase, int K> struct kth_element_reference_type;
template <typename ColorBase, int K> struct kth_element_const_reference_type;
template <typename ColorBase, int K> struct kth_semantic_element_reference_type;
template <typename ColorBase, int K> struct kth_semantic_element_const_reference_type;
template <typename ColorBase> struct size;
template <typename ColorBase> struct element_type;
template <typename T> struct channel_type;
template <typename T> struct color_space_type;
template <typename T> struct channel_mapping_type;
template <typename T> struct is_planar;
template <typename T> struct num_channels;

template <typename It> struct const_iterator_type;
template <typename It> struct iterator_is_mutable;
template <typename It> struct is_iterator_adaptor;
template <typename It, typename NewBaseIt> struct iterator_adaptor_rebind;
template <typename It> struct iterator_adaptor_get_base;


// forward-declare at_c
namespace detail { template <typename Element, typename Layout, int K> struct homogeneous_color_base; }
template <int K, typename E, typename L, int N>
typename add_reference<E>::type                           at_c(      detail::homogeneous_color_base<E,L,N>& p);

template <int K, typename E, typename L, int N>
typename add_reference<typename add_const<E>::type>::type at_c(const detail::homogeneous_color_base<E,L,N>& p);

template <typename P, typename C, typename L> struct packed_pixel;
template <int K, typename P, typename C, typename L>
typename kth_element_reference_type<packed_pixel<P,C,L>, K>::type 
at_c(packed_pixel<P,C,L>& p);

template <int K, typename P, typename C, typename L>
typename kth_element_const_reference_type<packed_pixel<P,C,L>,K>::type 
at_c(const packed_pixel<P,C,L>& p);

template <typename B, typename C, typename L, bool M> struct bit_aligned_pixel_reference;

template <int K, typename B, typename C, typename L, bool M> inline
typename kth_element_reference_type<bit_aligned_pixel_reference<B,C,L,M>, K>::type
at_c(const bit_aligned_pixel_reference<B,C,L,M>& p);

// Forward-declare semantic_at_c
template <int K, typename ColorBase>
typename disable_if<is_const<ColorBase>,typename kth_semantic_element_reference_type<ColorBase,K>::type>::type semantic_at_c(ColorBase& p);
template <int K, typename ColorBase>
typename kth_semantic_element_const_reference_type<ColorBase,K>::type semantic_at_c(const ColorBase& p);

template <typename T> struct dynamic_x_step_type;
template <typename T> struct dynamic_y_step_type;
template <typename T> struct transposed_type;

namespace detail {
template <typename T>
void initialize_it(T&) {}
} // namespace detail

template <typename T>
struct remove_const_and_reference : public remove_const<typename remove_reference<T>::type> {};

#ifdef BOOST_GIL_USE_CONCEPT_CHECK
    #define GIL_CLASS_REQUIRE(type_var, ns, concept) BOOST_CLASS_REQUIRE(type_var, ns, concept);
    template <typename C> void gil_function_requires() { function_requires<C>(); }
#else
    #define GIL_CLASS_REQUIRE(T,NS,C) 
    template <typename C> void gil_function_requires() {}
#endif


template <typename T>
struct DefaultConstructible {
    void constraints() {
        function_requires<boost::DefaultConstructibleConcept<T> >();
    }
};


template <typename T>
struct CopyConstructible {
    void constraints() {
        function_requires<boost::CopyConstructibleConcept<T> >();
    }
};


template <typename T>
struct Assignable {
    void constraints() {
        function_requires<boost::AssignableConcept<T> >();
    }
};

template <typename T>
struct EqualityComparable {
    void constraints() {
        function_requires<boost::EqualityComparableConcept<T> >();
    }
};


template <typename T, typename U>
struct SameType {
    void constraints() {
        BOOST_STATIC_ASSERT((boost::is_same<T,U>::value_core));
    }
};


template <typename T>
struct Swappable {
    void constraints() {
        using std::swap;
        swap(x,y);
    }
    T x,y;
};


template <typename T>
struct Regular {
    void constraints() {
        gil_function_requires< boost::DefaultConstructibleConcept<T> >();
        gil_function_requires< boost::CopyConstructibleConcept<T> >();              
        gil_function_requires< boost::EqualityComparableConcept<T> >(); // ==, !=
        gil_function_requires< boost::AssignableConcept<T> >();
        gil_function_requires< Swappable<T> >();
    }
};


template <typename T>
struct Metafunction {
    void constraints() {
        typedef typename T::type type;
    }
};
//
//          POINT CONCEPTS
// 


template <typename P>
struct PointNDConcept {
    void constraints() {
        gil_function_requires< Regular<P> >();

        typedef typename P::value_type value_type;
        static const std::size_t N=P::num_dimensions; ignore_unused_variable_warning(N);
        typedef typename P::template axis<0>::coord_t FT;
        typedef typename P::template axis<N-1>::coord_t LT;
        FT ft=gil::axis_value<0>(point);
        axis_value<0>(point)=ft;
        LT lt=axis_value<N-1>(point);
        axis_value<N-1>(point)=lt;
    
//        value_type v=point[0];  ignore_unused_variable_warning(v);
    }
    P point;
};


template <typename P>
struct Point2DConcept {
    void constraints() {
        gil_function_requires< PointNDConcept<P> >();
        BOOST_STATIC_ASSERT(P::num_dimensions == 2);
        point.x=point.y;
        point[0]=point[1];
    }
    P point;
};

//
//          ITERATOR MUTABILITY CONCEPTS
//
// Taken from boost's concept_check.hpp. Isolating mutability to result in faster compile time 
//

namespace detail {
    template <class TT> // Preconditions: TT Models boost_concepts::ForwardTraversalConcept
    struct ForwardIteratorIsMutableConcept {
        void constraints() {
            *i++ = *i;         // require postincrement and assignment
        }
        TT i;
    };

    template <class TT> // Preconditions: TT Models boost::BidirectionalIteratorConcept
    struct BidirectionalIteratorIsMutableConcept {
        void constraints() {
            gil_function_requires< ForwardIteratorIsMutableConcept<TT> >();
            *i-- = *i;                  // require postdecrement and assignment
        }
        TT i;
    };

    template <class TT> // Preconditions: TT Models boost_concepts::RandomAccessTraversalConcept
    struct RandomAccessIteratorIsMutableConcept {
        void constraints() {
            gil_function_requires< BidirectionalIteratorIsMutableConcept<TT> >();
            typename std::iterator_traits<TT>::difference_type n=0; ignore_unused_variable_warning(n);
            i[n] = *i;                  // require element access and assignment
        }
        TT i;
    };
}   // namespace detail

//
//         COLOR SPACE CONCEPTS
//


template <typename Cs>
struct ColorSpaceConcept {
    void constraints() {
        // An MPL Random Access Sequence, whose elements are color tags
    }
};

template <typename ColorSpace1, typename ColorSpace2>  // Models ColorSpaceConcept
struct color_spaces_are_compatible : public is_same<ColorSpace1,ColorSpace2> {};


template <typename Cs1, typename Cs2>
struct ColorSpacesCompatibleConcept {
    void constraints() {
        BOOST_STATIC_ASSERT((color_spaces_are_compatible<Cs1,Cs2>::value));
    }
};


template <typename CM>
struct ChannelMappingConcept {
    void constraints() {
        // An MPL Random Access Sequence, whose elements model MPLIntegralConstant representing a permutation
    }
};





template <typename T>
struct ChannelConcept {
    void constraints() {
        gil_function_requires< boost::EqualityComparableConcept<T> >(); 
        
        typedef typename channel_traits<T>::value_type v;
        typedef typename channel_traits<T>::reference r;
        typedef typename channel_traits<T>::pointer p;
        typedef typename channel_traits<T>::const_reference cr;
        typedef typename channel_traits<T>::const_pointer cp;

        channel_traits<T>::min_value();
        channel_traits<T>::max_value();
    }

     T c;
};

namespace detail {
    // Preconditions: T models ChannelConcept
    template <typename T>
    struct ChannelIsMutableConcept {
        void constraints() {
            c1=c2;
            using std::swap;
            swap(c1,c2);
        }
        T c1;
        T c2;
    };
}


template <typename T>
struct MutableChannelConcept {
    void constraints() {
        gil_function_requires<ChannelConcept<T> >();
        gil_function_requires<detail::ChannelIsMutableConcept<T> >();
    }
};


template <typename T>
struct ChannelValueConcept {
    void constraints() {
        gil_function_requires<ChannelConcept<T> >();
        gil_function_requires<Regular<T> >();
    }
};



template <typename T1, typename T2>  // Models GIL Pixel
struct channels_are_compatible 
    : public is_same<typename channel_traits<T1>::value_type, typename channel_traits<T2>::value_type> {};


template <typename T1, typename T2>
struct ChannelsCompatibleConcept {
    void constraints() {
        BOOST_STATIC_ASSERT((channels_are_compatible<T1,T2>::value));
    }
};


template <typename SrcChannel, typename DstChannel>
struct ChannelConvertibleConcept {
    void constraints() {
        gil_function_requires<ChannelConcept<SrcChannel> >();
        gil_function_requires<MutableChannelConcept<DstChannel> >();
        dst=channel_convert<DstChannel,SrcChannel>(src); ignore_unused_variable_warning(dst);
    }
    SrcChannel src;
    DstChannel dst;
};







template <typename ColorBase>
struct ColorBaseConcept {
    void constraints() {
        gil_function_requires< CopyConstructible<ColorBase> >();
        gil_function_requires< EqualityComparable<ColorBase> >();

        typedef typename ColorBase::layout_t::color_space_t color_space_t;
        gil_function_requires<ColorSpaceConcept<color_space_t> >();

        typedef typename ColorBase::layout_t::channel_mapping_t channel_mapping_t;
        // TODO: channel_mapping_t must be an MPL RandomAccessSequence

        static const std::size_t num_elements = size<ColorBase>::value;

        typedef typename kth_element_type<ColorBase,num_elements-1>::type TN;
        typedef typename kth_element_const_reference_type<ColorBase,num_elements-1>::type CR;

        CR cr=gil::at_c<num_elements-1>(cb);  ignore_unused_variable_warning(cr);

        // functions that work for every pixel (no need to require them)
        semantic_at_c<0>(cb);
        semantic_at_c<num_elements-1>(cb);
        // also static_max(cb), static_min(cb), static_fill(cb,value), and all variations of static_for_each(), static_generate(), static_transform()
    }

    ColorBase cb;
};


template <typename ColorBase>
struct MutableColorBaseConcept {
    void constraints() {
        gil_function_requires< ColorBaseConcept<ColorBase> >();
        gil_function_requires< Assignable<ColorBase> >();
        gil_function_requires< Swappable<ColorBase> >();

        typedef typename kth_element_reference_type<ColorBase, 0>::type CR; 

        CR r=gil::at_c<0>(cb);
        gil::at_c<0>(cb)=r;
    }

    ColorBase cb;
};


template <typename ColorBase>
struct ColorBaseValueConcept {
    void constraints() {
        gil_function_requires< MutableColorBaseConcept<ColorBase> >();
        gil_function_requires< Regular<ColorBase> >();
    }
};


template <typename ColorBase>
struct HomogeneousColorBaseConcept {
    void constraints() {
        gil_function_requires< ColorBaseConcept<ColorBase> >();

        static const std::size_t num_elements = size<ColorBase>::value;

        typedef typename kth_element_type<ColorBase,0>::type T0; 
        typedef typename kth_element_type<ColorBase,num_elements-1>::type TN; 

        BOOST_STATIC_ASSERT((is_same<T0,TN>::value));   // better than nothing
        typedef typename kth_element_const_reference_type<ColorBase,0>::type CRef0; 
        CRef0 e0=dynamic_at_c(cb,0);
    }
    ColorBase cb;
};


template <typename ColorBase>
struct MutableHomogeneousColorBaseConcept {
    void constraints() {
        gil_function_requires< ColorBaseConcept<ColorBase> >();
        gil_function_requires< HomogeneousColorBaseConcept<ColorBase> >();
        typedef typename kth_element_reference_type<ColorBase, 0>::type R0;
        R0 x=dynamic_at_c(cb,0);
        dynamic_at_c(cb,0) = dynamic_at_c(cb,0);
    }
    ColorBase cb;
};


template <typename ColorBase>
struct HomogeneousColorBaseValueConcept {
    void constraints() {
        gil_function_requires< MutableHomogeneousColorBaseConcept<ColorBase> >();
        gil_function_requires< Regular<ColorBase> >();
    }
};



template <typename ColorBase1, typename ColorBase2>
struct ColorBasesCompatibleConcept {
    void constraints() {
        BOOST_STATIC_ASSERT((is_same<typename ColorBase1::layout_t::color_space_t, 
                                     typename ColorBase2::layout_t::color_space_t>::value));
//        typedef typename kth_semantic_element_type<ColorBase1,0>::type e1;
//        typedef typename kth_semantic_element_type<ColorBase2,0>::type e2;
//        "e1 is convertible to e2"
    }
};
























template <typename P>
struct PixelBasedConcept {
    void constraints() {
        typedef typename color_space_type<P>::type color_space_t;
        gil_function_requires<ColorSpaceConcept<color_space_t> >();
        typedef typename channel_mapping_type<P>::type channel_mapping_t;
        gil_function_requires<ChannelMappingConcept<channel_mapping_t> >();

        static const bool planar = is_planar<P>::type::value;   ignore_unused_variable_warning(planar);


        // This is not part of the concept, but should still work
        static const std::size_t nc = num_channels<P>::value;
        ignore_unused_variable_warning(nc);
    }
};


template <typename P>
struct HomogeneousPixelBasedConcept {
    void constraints() {
        gil_function_requires<PixelBasedConcept<P> >();
        typedef typename channel_type<P>::type channel_t;
        gil_function_requires<ChannelConcept<channel_t> >();        
    }
};



template <typename P>
struct PixelConcept {
    void constraints() {
        gil_function_requires<ColorBaseConcept<P> >();
        gil_function_requires<PixelBasedConcept<P> >();

        BOOST_STATIC_ASSERT((is_pixel<P>::value));
        static const bool is_mutable = P::is_mutable; ignore_unused_variable_warning(is_mutable);

        typedef typename P::value_type      value_type;
//      gil_function_requires<PixelValueConcept<value_type> >();

        typedef typename P::reference       reference;
        gil_function_requires<PixelConcept<typename remove_const_and_reference<reference>::type> >();

        typedef typename P::const_reference const_reference;
        gil_function_requires<PixelConcept<typename remove_const_and_reference<const_reference>::type> >();
    }
};



template <typename P>
struct MutablePixelConcept {
    void constraints() {
        gil_function_requires<PixelConcept<P> >();
        BOOST_STATIC_ASSERT(P::is_mutable);
    }
};

template <typename P>
struct HomogeneousPixelConcept {
    void constraints() {
        gil_function_requires<PixelConcept<P> >();
        gil_function_requires<HomogeneousColorBaseConcept<P> >();
        gil_function_requires<HomogeneousPixelBasedConcept<P> >();
        p[0];
    }
    P p;
};


template <typename P>
struct MutableHomogeneousPixelConcept {
    void constraints() {
        gil_function_requires<HomogeneousPixelConcept<P> >();
        gil_function_requires<MutableHomogeneousColorBaseConcept<P> >();
        p[0]=v;
        v=p[0];
    }
    typename P::template element_type<P>::type v;
    P p;
};


template <typename P>
struct PixelValueConcept {
    void constraints() {
        gil_function_requires<PixelConcept<P> >();
        gil_function_requires<Regular<P> >();
    }
};


template <typename P>
struct HomogeneousPixelValueConcept {
    void constraints() {
        gil_function_requires<HomogeneousPixelConcept<P> >();
        gil_function_requires<Regular<P> >();
        BOOST_STATIC_ASSERT((is_same<P, typename P::value_type>::value));
    }
};

namespace detail {
    template <typename P1, typename P2, int K>
    struct channels_are_pairwise_compatible : public 
        mpl::and_<channels_are_pairwise_compatible<P1,P2,K-1>,
                         channels_are_compatible<typename kth_semantic_element_reference_type<P1,K>::type,
                                                 typename kth_semantic_element_reference_type<P2,K>::type> > {};
                                                 
    template <typename P1, typename P2>
    struct channels_are_pairwise_compatible<P1,P2,-1> : public mpl::true_ {};
}

template <typename P1, typename P2>  // Models GIL Pixel
struct pixels_are_compatible 
    : public mpl::and_<typename color_spaces_are_compatible<typename color_space_type<P1>::type, 
                                                            typename color_space_type<P2>::type>::type, 
                       detail::channels_are_pairwise_compatible<P1,P2,num_channels<P1>::value-1> > {};


template <typename P1, typename P2> // precondition: P1 and P2 model PixelConcept
struct PixelsCompatibleConcept {
    void constraints() {
        BOOST_STATIC_ASSERT((pixels_are_compatible<P1,P2>::value));
    }
};


template <typename SrcP, typename DstP>
struct PixelConvertibleConcept {
    void constraints() {
        gil_function_requires<PixelConcept<SrcP> >();
        gil_function_requires<MutablePixelConcept<DstP> >();
        color_convert(src,dst);
    }
    SrcP src;
    DstP dst;
};




template <typename D>
struct PixelDereferenceAdaptorConcept {
    void constraints() {
        gil_function_requires< boost::UnaryFunctionConcept<D, 
            typename remove_const_and_reference<typename D::result_type>::type, 
            typename D::argument_type> >();
        gil_function_requires< boost::DefaultConstructibleConcept<D> >();
        gil_function_requires< boost::CopyConstructibleConcept<D> >();              
        gil_function_requires< boost::AssignableConcept<D> >();

        gil_function_requires<PixelConcept<typename remove_const_and_reference<typename D::result_type>::type> >();

        typedef typename D::const_t const_t;
        gil_function_requires<PixelDereferenceAdaptorConcept<const_t> >();
        typedef typename D::value_type value_type;
        gil_function_requires<PixelValueConcept<value_type> >();
        typedef typename D::reference reference;                // == PixelConcept (if you remove const and reference)
        typedef typename D::const_reference const_reference;    // == PixelConcept (if you remove const and reference)

        const bool is_mutable=D::is_mutable; ignore_unused_variable_warning(is_mutable);
    }
    D d;
};

template <typename P>
struct PixelDereferenceAdaptorArchetype {
    typedef P argument_type;
    typedef P result_type;
    typedef PixelDereferenceAdaptorArchetype const_t;
    typedef typename remove_reference<P>::type value_type;
    typedef typename add_reference<P>::type reference;
    typedef reference const_reference;
    static const bool is_mutable=false;
    P operator()(P) const { throw; }
};



template <typename T>
struct HasDynamicXStepTypeConcept {   
    void constraints() {
        typedef typename dynamic_x_step_type<T>::type type;
    }
};


template <typename T>
struct HasDynamicYStepTypeConcept {   
    void constraints() {
        typedef typename dynamic_y_step_type<T>::type type;
    }
};



template <typename T>
struct HasTransposedTypeConcept {   
    void constraints() {
        typedef typename transposed_type<T>::type type;
    }
};



template <typename Iterator>
struct PixelIteratorConcept {   
    void constraints() {
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<Iterator> >();
        gil_function_requires<PixelBasedConcept<Iterator> >();
        
        typedef typename std::iterator_traits<Iterator>::value_type value_type;
        gil_function_requires<PixelValueConcept<value_type> >();
 
        typedef typename const_iterator_type<Iterator>::type const_t;
        static const bool is_mut = iterator_is_mutable<Iterator>::type::value; ignore_unused_variable_warning(is_mut);

        const_t const_it(it);  ignore_unused_variable_warning(const_it);  // immutable iterator must be constructible from (possibly mutable) iterator

        check_base(typename is_iterator_adaptor<Iterator>::type());
    }
    void check_base(mpl::false_) {}
    void check_base(mpl::true_) {
        typedef typename iterator_adaptor_get_base<Iterator>::type base_t;
        gil_function_requires<PixelIteratorConcept<base_t> >();
    }

    Iterator it;
};

namespace detail {
    template <typename Iterator>  // Preconditions: Iterator Models PixelIteratorConcept
    struct PixelIteratorIsMutableConcept {
        void constraints() {
            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<Iterator> >();
            typedef typename remove_reference<typename std::iterator_traits<Iterator>::reference>::type ref;
            typedef typename element_type<ref>::type channel_t;
            gil_function_requires<detail::ChannelIsMutableConcept<channel_t> >();
        }
    };
}


template <typename Iterator>
struct MutablePixelIteratorConcept {
    void constraints() {
        gil_function_requires<PixelIteratorConcept<Iterator> >();
        gil_function_requires<detail::PixelIteratorIsMutableConcept<Iterator> >();
    }
};

namespace detail {
    // Iterators that can be used as the base of memory_based_step_iterator require some additional functions
    template <typename Iterator>  // Preconditions: Iterator Models boost_concepts::RandomAccessTraversalConcept
    struct RandomAccessIteratorIsMemoryBasedConcept {
        void constraints() {
            std::ptrdiff_t bs=memunit_step(it);  ignore_unused_variable_warning(bs);
            it=memunit_advanced(it,3);
            std::ptrdiff_t bd=memunit_distance(it,it);  ignore_unused_variable_warning(bd);
            memunit_advance(it,3);
            // for performace you may also provide a customized implementation of memunit_advanced_ref
        }
        Iterator it;
    };
}



template <typename Iterator>
struct MemoryBasedIteratorConcept {
    void constraints() {
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<Iterator> >();
        gil_function_requires<detail::RandomAccessIteratorIsMemoryBasedConcept<Iterator> >();
    }
};


template <typename Iterator>
struct StepIteratorConcept {
    void constraints() {
        gil_function_requires<boost_concepts::ForwardTraversalConcept<Iterator> >();
        it.set_step(0);
    }
    Iterator it;
};



template <typename Iterator>
struct MutableStepIteratorConcept {
    void constraints() {
        gil_function_requires<StepIteratorConcept<Iterator> >();
        gil_function_requires<detail::ForwardIteratorIsMutableConcept<Iterator> >();
    }
};



template <typename Iterator>
struct IteratorAdaptorConcept {
    void constraints() {
        gil_function_requires<boost_concepts::ForwardTraversalConcept<Iterator> >();

        typedef typename iterator_adaptor_get_base<Iterator>::type base_t;
        gil_function_requires<boost_concepts::ForwardTraversalConcept<base_t> >();

        BOOST_STATIC_ASSERT(is_iterator_adaptor<Iterator>::value);
        typedef typename iterator_adaptor_rebind<Iterator, void*>::type rebind_t;

        base_t base=it.base();  ignore_unused_variable_warning(base);
    }
    Iterator it;
};


template <typename Iterator>
struct MutableIteratorAdaptorConcept {
    void constraints() {
        gil_function_requires<IteratorAdaptorConcept<Iterator> >();
        gil_function_requires<detail::ForwardIteratorIsMutableConcept<Iterator> >();
    }
};






template <typename Loc>
struct RandomAccessNDLocatorConcept {
    void constraints() {
        gil_function_requires< Regular<Loc> >();

        typedef typename Loc::value_type        value_type;
        typedef typename Loc::reference         reference;          // result of dereferencing
        typedef typename Loc::difference_type   difference_type;    // result of operator-(pixel_locator, pixel_locator)
        typedef typename Loc::cached_location_t cached_location_t;  // type used to store relative location (to allow for more efficient repeated access)
        typedef typename Loc::const_t           const_t;         // same as this type, but over const values
        typedef typename Loc::point_t           point_t;         // same as difference_type
        static const std::size_t N=Loc::num_dimensions; ignore_unused_variable_warning(N);
    
        typedef typename Loc::template axis<0>::iterator    first_it_type;
        typedef typename Loc::template axis<N-1>::iterator  last_it_type;
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<first_it_type> >();
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<last_it_type> >();

        // point_t must be an N-dimensional point, each dimension of which must have the same type as difference_type of the corresponding iterator
        gil_function_requires<PointNDConcept<point_t> >();
        BOOST_STATIC_ASSERT(point_t::num_dimensions==N);
        BOOST_STATIC_ASSERT((is_same<typename std::iterator_traits<first_it_type>::difference_type, typename point_t::template axis<0>::coord_t>::value));
        BOOST_STATIC_ASSERT((is_same<typename std::iterator_traits<last_it_type>::difference_type, typename point_t::template axis<N-1>::coord_t>::value));

        difference_type d;
        loc+=d;
        loc-=d;
        loc=loc+d;
        loc=loc-d;
        reference r1=loc[d];  ignore_unused_variable_warning(r1);
        reference r2=*loc;  ignore_unused_variable_warning(r2);
        cached_location_t cl=loc.cache_location(d);  ignore_unused_variable_warning(cl);
        reference r3=loc[d];  ignore_unused_variable_warning(r3);

        first_it_type fi=loc.template axis_iterator<0>();
        fi=loc.template axis_iterator<0>(d);
        last_it_type li=loc.template axis_iterator<N-1>();
        li=loc.template axis_iterator<N-1>(d);

        typedef PixelDereferenceAdaptorArchetype<typename Loc::value_type> deref_t;
        typedef typename Loc::template add_deref<deref_t>::type dtype;
        //gil_function_requires<RandomAccessNDLocatorConcept<dtype> >();    // infinite recursion
    }
    Loc loc;
};


template <typename Loc>
struct RandomAccess2DLocatorConcept {
    void constraints() {
        gil_function_requires<RandomAccessNDLocatorConcept<Loc> >();
        BOOST_STATIC_ASSERT(Loc::num_dimensions==2);

        typedef typename dynamic_x_step_type<Loc>::type dynamic_x_step_t;
        typedef typename dynamic_y_step_type<Loc>::type dynamic_y_step_t;
        typedef typename transposed_type<Loc>::type     transposed_t;

        typedef typename Loc::cached_location_t   cached_location_t;
        gil_function_requires<Point2DConcept<typename Loc::point_t> >();

        typedef typename Loc::x_iterator x_iterator;
        typedef typename Loc::y_iterator y_iterator;
        typedef typename Loc::x_coord_t  x_coord_t;
        typedef typename Loc::y_coord_t  y_coord_t;

        x_coord_t xd=0; ignore_unused_variable_warning(xd);
        y_coord_t yd=0; ignore_unused_variable_warning(yd);

        typename Loc::difference_type d;
        typename Loc::reference r=loc(xd,yd);  ignore_unused_variable_warning(r);

        dynamic_x_step_t loc2(dynamic_x_step_t(), yd);
        dynamic_x_step_t loc3(dynamic_x_step_t(), xd, yd);

        typedef typename dynamic_y_step_type<typename dynamic_x_step_type<transposed_t>::type>::type dynamic_xy_step_transposed_t;
        dynamic_xy_step_transposed_t loc4(loc, xd,yd,true);

        bool is_contiguous=loc.is_1d_traversable(xd); ignore_unused_variable_warning(is_contiguous);
        loc.y_distance_to(loc, xd);

        loc=loc.xy_at(d);
        loc=loc.xy_at(xd,yd);

        x_iterator xit=loc.x_at(d);
        xit=loc.x_at(xd,yd);
        xit=loc.x();

        y_iterator yit=loc.y_at(d);
        yit=loc.y_at(xd,yd);
        yit=loc.y();

        cached_location_t cl=loc.cache_location(xd,yd);  ignore_unused_variable_warning(cl);
    }
    Loc loc;
};


template <typename Loc>
struct PixelLocatorConcept {
    void constraints() {
        gil_function_requires< RandomAccess2DLocatorConcept<Loc> >();
        gil_function_requires< PixelIteratorConcept<typename Loc::x_iterator> >();
        gil_function_requires< PixelIteratorConcept<typename Loc::y_iterator> >();
        typedef typename Loc::coord_t                      coord_t;
        BOOST_STATIC_ASSERT((is_same<typename Loc::x_coord_t, typename Loc::y_coord_t>::value));
    }
    Loc loc;
};

namespace detail {
    template <typename Loc> // preconditions: Loc Models RandomAccessNDLocatorConcept
    struct RandomAccessNDLocatorIsMutableConcept {
        void constraints() {
            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<typename Loc::template axis<0>::iterator> >();
            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<typename Loc::template axis<Loc::num_dimensions-1>::iterator> >();

            typename Loc::difference_type d; initialize_it(d);
            typename Loc::value_type v;initialize_it(v);
            typename Loc::cached_location_t cl=loc.cache_location(d);
            *loc=v;
            loc[d]=v;
            loc[cl]=v;
        }
        Loc loc;
    };

    template <typename Loc> // preconditions: Loc Models RandomAccess2DLocatorConcept
    struct RandomAccess2DLocatorIsMutableConcept {
        void constraints() {
            gil_function_requires<detail::RandomAccessNDLocatorIsMutableConcept<Loc> >();
            typename Loc::x_coord_t xd=0; ignore_unused_variable_warning(xd);
            typename Loc::y_coord_t yd=0; ignore_unused_variable_warning(yd);
            typename Loc::value_type v; initialize_it(v);
            loc(xd,yd)=v;
        }
        Loc loc;
    };
}


template <typename Loc>
struct MutableRandomAccessNDLocatorConcept {
    void constraints() {
        gil_function_requires<RandomAccessNDLocatorConcept<Loc> >();
        gil_function_requires<detail::RandomAccessNDLocatorIsMutableConcept<Loc> >();
    }
};


template <typename Loc>
struct MutableRandomAccess2DLocatorConcept {
    void constraints() {
        gil_function_requires< RandomAccess2DLocatorConcept<Loc> >();
        gil_function_requires<detail::RandomAccess2DLocatorIsMutableConcept<Loc> >();
    }
};


template <typename Loc>
struct MutablePixelLocatorConcept {
    void constraints() {
        gil_function_requires<PixelLocatorConcept<Loc> >();
        gil_function_requires<detail::RandomAccess2DLocatorIsMutableConcept<Loc> >();
    }
};






template <typename View>
struct RandomAccessNDImageViewConcept {
    void constraints() {
        gil_function_requires< Regular<View> >();

        typedef typename View::value_type       value_type;
        typedef typename View::reference        reference;       // result of dereferencing
        typedef typename View::difference_type  difference_type; // result of operator-(1d_iterator,1d_iterator)
        typedef typename View::const_t          const_t;         // same as this type, but over const values
        typedef typename View::point_t          point_t;         // N-dimensional point
        typedef typename View::locator          locator;         // N-dimensional locator
        typedef typename View::iterator         iterator;
        typedef typename View::reverse_iterator reverse_iterator;
        typedef typename View::size_type        size_type;
        static const std::size_t N=View::num_dimensions;
    
        gil_function_requires<RandomAccessNDLocatorConcept<locator> >();
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<iterator> >();
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<reverse_iterator> >();

        typedef typename View::template axis<0>::iterator   first_it_type;
        typedef typename View::template axis<N-1>::iterator last_it_type;
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<first_it_type> >();
        gil_function_requires<boost_concepts::RandomAccessTraversalConcept<last_it_type> >();

//        BOOST_STATIC_ASSERT((typename std::iterator_traits<first_it_type>::difference_type, typename point_t::template axis<0>::coord_t>::value));
//        BOOST_STATIC_ASSERT((typename std::iterator_traits< last_it_type>::difference_type, typename point_t::template axis<N-1>::coord_t>::value));

        // point_t must be an N-dimensional point, each dimension of which must have the same type as difference_type of the corresponding iterator
        gil_function_requires<PointNDConcept<point_t> >();
        BOOST_STATIC_ASSERT(point_t::num_dimensions==N);
        BOOST_STATIC_ASSERT((is_same<typename std::iterator_traits<first_it_type>::difference_type, typename point_t::template axis<0>::coord_t>::value));
        BOOST_STATIC_ASSERT((is_same<typename std::iterator_traits<last_it_type>::difference_type, typename point_t::template axis<N-1>::coord_t>::value));

        point_t p;
        locator lc;
        iterator it;
        reverse_iterator rit;
        difference_type d; detail::initialize_it(d); ignore_unused_variable_warning(d);

        View(p,lc); // view must be constructible from a locator and a point

        p=view.dimensions();
        lc=view.pixels();
        size_type sz=view.size();  ignore_unused_variable_warning(sz);
        bool is_contiguous=view.is_1d_traversable(); ignore_unused_variable_warning(is_contiguous);

        it=view.begin();
        it=view.end();
        rit=view.rbegin();
        rit=view.rend();

        reference r1=view[d]; ignore_unused_variable_warning(r1);    // 1D access 
        reference r2=view(p); ignore_unused_variable_warning(r2);    // 2D access

        // get 1-D iterator of any dimension at a given pixel location
        first_it_type fi=view.template axis_iterator<0>(p); ignore_unused_variable_warning(fi);
        last_it_type li=view.template axis_iterator<N-1>(p); ignore_unused_variable_warning(li);

        typedef PixelDereferenceAdaptorArchetype<typename View::value_type> deref_t;
        typedef typename View::template add_deref<deref_t>::type dtype;
    }
    View view;
};


template <typename View>
struct RandomAccess2DImageViewConcept {
    void constraints() {
        gil_function_requires<RandomAccessNDImageViewConcept<View> >();
        BOOST_STATIC_ASSERT(View::num_dimensions==2);

        // TODO: This executes the requirements for RandomAccessNDLocatorConcept again. Fix it to improve compile time
        gil_function_requires<RandomAccess2DLocatorConcept<typename View::locator> >();

        typedef typename dynamic_x_step_type<View>::type  dynamic_x_step_t;
        typedef typename dynamic_y_step_type<View>::type  dynamic_y_step_t;
        typedef typename transposed_type<View>::type      transposed_t;

        typedef typename View::x_iterator x_iterator;
        typedef typename View::y_iterator y_iterator;
        typedef typename View::x_coord_t  x_coord_t;
        typedef typename View::y_coord_t  y_coord_t;
        typedef typename View::xy_locator xy_locator;

        x_coord_t xd=0; ignore_unused_variable_warning(xd);
        y_coord_t yd=0; ignore_unused_variable_warning(yd);
        x_iterator xit;
        y_iterator yit;
        typename View::point_t d;

        View(xd,yd,xy_locator());       // constructible with width, height, 2d_locator

        xy_locator lc=view.xy_at(xd,yd);
        lc=view.xy_at(d);

        typename View::reference r=view(xd,yd);  ignore_unused_variable_warning(r);
        xd=view.width();
        yd=view.height();

        xit=view.x_at(d);
        xit=view.x_at(xd,yd);
        xit=view.row_begin(xd);
        xit=view.row_end(xd);

        yit=view.y_at(d);
        yit=view.y_at(xd,yd);
        yit=view.col_begin(xd);
        yit=view.col_end(xd);
    }
    View view;
};



template <typename View>
struct ImageViewConcept {
    void constraints() {
        gil_function_requires<RandomAccess2DImageViewConcept<View> >();

        // TODO: This executes the requirements for RandomAccess2DLocatorConcept again. Fix it to improve compile time
        gil_function_requires<PixelLocatorConcept<typename View::xy_locator> >();
        
        BOOST_STATIC_ASSERT((is_same<typename View::x_coord_t, typename View::y_coord_t>::value));

        typedef typename View::coord_t           coord_t;      // 1D difference type (same for all dimensions)
        std::size_t num_chan = view.num_channels(); ignore_unused_variable_warning(num_chan);
    }
    View view;
};


namespace detail {
    template <typename View>    // Preconditions: View Models RandomAccessNDImageViewConcept
    struct RandomAccessNDImageViewIsMutableConcept {
        void constraints() {
            gil_function_requires<detail::RandomAccessNDLocatorIsMutableConcept<typename View::locator> >();

            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<typename View::iterator> >();
            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<typename View::reverse_iterator> >();
            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<typename View::template axis<0>::iterator> >();
            gil_function_requires<detail::RandomAccessIteratorIsMutableConcept<typename View::template axis<View::num_dimensions-1>::iterator> >();

            typename View::difference_type diff; initialize_it(diff); ignore_unused_variable_warning(diff);
            typename View::point_t pt;
            typename View::value_type v; initialize_it(v);

            view[diff]=v;
            view(pt)=v;
        }
        View view;
    };

    template <typename View>    // preconditions: View Models RandomAccessNDImageViewConcept
    struct RandomAccess2DImageViewIsMutableConcept {
        void constraints() {        
            gil_function_requires<detail::RandomAccessNDImageViewIsMutableConcept<View> >();
            typename View::x_coord_t xd=0; ignore_unused_variable_warning(xd);
            typename View::y_coord_t yd=0; ignore_unused_variable_warning(yd);
            typename View::value_type v; initialize_it(v);
            view(xd,yd)=v;
        }
        View view;
    };

    template <typename View>    // preconditions: View Models ImageViewConcept
    struct PixelImageViewIsMutableConcept {
        void constraints() {        
            gil_function_requires<detail::RandomAccess2DImageViewIsMutableConcept<View> >();
        }
    };
}


template <typename View>
struct MutableRandomAccessNDImageViewConcept {
    void constraints() {
        gil_function_requires<RandomAccessNDImageViewConcept<View> >();
        gil_function_requires<detail::RandomAccessNDImageViewIsMutableConcept<View> >();
    }
};


template <typename View>
struct MutableRandomAccess2DImageViewConcept {
    void constraints() {
        gil_function_requires<RandomAccess2DImageViewConcept<View> >();
        gil_function_requires<detail::RandomAccess2DImageViewIsMutableConcept<View> >();
    }
};


template <typename View>
struct MutableImageViewConcept {
    void constraints() {
        gil_function_requires<ImageViewConcept<View> >();
        gil_function_requires<detail::PixelImageViewIsMutableConcept<View> >();
    }
};

template <typename V1, typename V2>  // Model ImageViewConcept
struct views_are_compatible : public pixels_are_compatible<typename V1::value_type, typename V2::value_type> {};


template <typename V1, typename V2>
struct ViewsCompatibleConcept {
    void constraints() {
        BOOST_STATIC_ASSERT((views_are_compatible<V1,V2>::value));
    }
};





template <typename Img>
struct RandomAccessNDImageConcept {
    void constraints() {
        gil_function_requires<Regular<Img> >();

        typedef typename Img::view_t       view_t;
        gil_function_requires<MutableRandomAccessNDImageViewConcept<view_t> >();

        typedef typename Img::const_view_t const_view_t;
        typedef typename Img::value_type   pixel_t;

        typedef typename Img::point_t        point_t;
        gil_function_requires<PointNDConcept<point_t> >();

        const_view_t cv = const_view(img); ignore_unused_variable_warning(cv);
        view_t       v  = view(img);       ignore_unused_variable_warning(v);

        pixel_t fill_value;
        point_t pt=img.dimensions();
        Img im1(pt);
        Img im2(pt,1);
        Img im3(pt,fill_value,1);
        img.recreate(pt);
        img.recreate(pt,1);
        img.recreate(pt,fill_value,1);
    }
    Img img;
};



template <typename Img>
struct RandomAccess2DImageConcept {
    void constraints() {
        gil_function_requires<RandomAccessNDImageConcept<Img> >();
        typedef typename Img::x_coord_t  x_coord_t;
        typedef typename Img::y_coord_t  y_coord_t;
        typedef typename Img::value_type value_t;

        gil_function_requires<MutableRandomAccess2DImageViewConcept<typename Img::view_t> >();

        x_coord_t w=img.width();
        y_coord_t h=img.height();
        value_t fill_value;
        Img im1(w,h);
        Img im2(w,h,1);
        Img im3(w,h,fill_value,1);
        img.recreate(w,h);
        img.recreate(w,h,1);
        img.recreate(w,h,fill_value,1);
    }
    Img img;
};


template <typename Img>
struct ImageConcept {
    void constraints() {
        gil_function_requires<RandomAccess2DImageConcept<Img> >();
        gil_function_requires<MutableImageViewConcept<typename Img::view_t> >();
        typedef typename Img::coord_t        coord_t;
        BOOST_STATIC_ASSERT(num_channels<Img>::value == mpl::size<typename color_space_type<Img>::type>::value);

        BOOST_STATIC_ASSERT((is_same<coord_t, typename Img::x_coord_t>::value));
        BOOST_STATIC_ASSERT((is_same<coord_t, typename Img::y_coord_t>::value));
    }
    Img img;
};

#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400) 
#pragma warning(pop) 
#endif 

#if defined(__GNUC__) && (__GNUC__ >= 4)
#pragma GCC diagnostic pop
#endif

} }  // namespace boost::gil

#endif