Chris@16: // Boost.Geometry (aka GGL, Generic Geometry Library)
Chris@16: 
Chris@16: // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
Chris@16: // Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
Chris@16: // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
Chris@16: 
Chris@16: // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
Chris@16: // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
Chris@16: 
Chris@16: // Use, modification and distribution is subject to the Boost Software License,
Chris@16: // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_GEOMETRY_ALGORITHMS_AREA_HPP
Chris@16: #define BOOST_GEOMETRY_ALGORITHMS_AREA_HPP
Chris@16: 
Chris@16: #include <boost/concept_check.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/range/functions.hpp>
Chris@16: #include <boost/range/metafunctions.hpp>
Chris@101: 
Chris@101: #include <boost/variant/apply_visitor.hpp>
Chris@16: #include <boost/variant/static_visitor.hpp>
Chris@16: #include <boost/variant/variant_fwd.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/core/closure.hpp>
Chris@16: #include <boost/geometry/core/exterior_ring.hpp>
Chris@16: #include <boost/geometry/core/interior_rings.hpp>
Chris@16: #include <boost/geometry/core/point_order.hpp>
Chris@101: #include <boost/geometry/core/point_type.hpp>
Chris@16: #include <boost/geometry/core/ring_type.hpp>
Chris@101: #include <boost/geometry/core/tags.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/geometries/concepts/check.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/algorithms/detail/calculate_null.hpp>
Chris@16: #include <boost/geometry/algorithms/detail/calculate_sum.hpp>
Chris@16: // #include <boost/geometry/algorithms/detail/throw_on_empty_input.hpp>
Chris@101: #include <boost/geometry/algorithms/detail/multi_sum.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/strategies/area.hpp>
Chris@16: #include <boost/geometry/strategies/default_area_result.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/strategies/concepts/area_concept.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/util/math.hpp>
Chris@16: #include <boost/geometry/util/order_as_direction.hpp>
Chris@16: #include <boost/geometry/views/closeable_view.hpp>
Chris@16: #include <boost/geometry/views/reversible_view.hpp>
Chris@16: 
Chris@16: 
Chris@16: namespace boost { namespace geometry
Chris@16: {
Chris@16: 
Chris@16: #ifndef DOXYGEN_NO_DETAIL
Chris@16: namespace detail { namespace area
Chris@16: {
Chris@16: 
Chris@16: struct box_area
Chris@16: {
Chris@16:     template <typename Box, typename Strategy>
Chris@16:     static inline typename coordinate_type<Box>::type
Chris@16:     apply(Box const& box, Strategy const&)
Chris@16:     {
Chris@16:         // Currently only works for 2D Cartesian boxes
Chris@16:         assert_dimension<Box, 2>();
Chris@16: 
Chris@16:         return (get<max_corner, 0>(box) - get<min_corner, 0>(box))
Chris@16:              * (get<max_corner, 1>(box) - get<min_corner, 1>(box));
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template
Chris@16: <
Chris@16:     iterate_direction Direction,
Chris@16:     closure_selector Closure
Chris@16: >
Chris@16: struct ring_area
Chris@16: {
Chris@16:     template <typename Ring, typename Strategy>
Chris@16:     static inline typename Strategy::return_type
Chris@16:     apply(Ring const& ring, Strategy const& strategy)
Chris@16:     {
Chris@16:         BOOST_CONCEPT_ASSERT( (geometry::concept::AreaStrategy<Strategy>) );
Chris@16:         assert_dimension<Ring, 2>();
Chris@16: 
Chris@16:         // Ignore warning (because using static method sometimes) on strategy
Chris@16:         boost::ignore_unused_variable_warning(strategy);
Chris@16: 
Chris@16:         // An open ring has at least three points,
Chris@16:         // A closed ring has at least four points,
Chris@16:         // if not, there is no (zero) area
Chris@101:         if (boost::size(ring)
Chris@16:                 < core_detail::closure::minimum_ring_size<Closure>::value)
Chris@16:         {
Chris@16:             return typename Strategy::return_type();
Chris@16:         }
Chris@16: 
Chris@16:         typedef typename reversible_view<Ring const, Direction>::type rview_type;
Chris@16:         typedef typename closeable_view
Chris@16:             <
Chris@16:                 rview_type const, Closure
Chris@16:             >::type view_type;
Chris@16:         typedef typename boost::range_iterator<view_type const>::type iterator_type;
Chris@16: 
Chris@16:         rview_type rview(ring);
Chris@16:         view_type view(rview);
Chris@16:         typename Strategy::state_type state;
Chris@16:         iterator_type it = boost::begin(view);
Chris@16:         iterator_type end = boost::end(view);
Chris@16: 
Chris@16:         for (iterator_type previous = it++;
Chris@16:             it != end;
Chris@16:             ++previous, ++it)
Chris@16:         {
Chris@16:             strategy.apply(*previous, *it, state);
Chris@16:         }
Chris@16: 
Chris@16:         return strategy.result(state);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: }} // namespace detail::area
Chris@16: 
Chris@16: 
Chris@16: #endif // DOXYGEN_NO_DETAIL
Chris@16: 
Chris@16: 
Chris@16: #ifndef DOXYGEN_NO_DISPATCH
Chris@16: namespace dispatch
Chris@16: {
Chris@16: 
Chris@16: template
Chris@16: <
Chris@16:     typename Geometry,
Chris@16:     typename Tag = typename tag<Geometry>::type
Chris@16: >
Chris@16: struct area : detail::calculate_null
Chris@16: {
Chris@16:     template <typename Strategy>
Chris@16:     static inline typename Strategy::return_type apply(Geometry const& geometry, Strategy const& strategy)
Chris@16:     {
Chris@16:         return calculate_null::apply<typename Strategy::return_type>(geometry, strategy);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@16: template <typename Geometry>
Chris@16: struct area<Geometry, box_tag> : detail::area::box_area
Chris@16: {};
Chris@16: 
Chris@16: 
Chris@16: template <typename Ring>
Chris@16: struct area<Ring, ring_tag>
Chris@16:     : detail::area::ring_area
Chris@16:         <
Chris@16:             order_as_direction<geometry::point_order<Ring>::value>::value,
Chris@16:             geometry::closure<Ring>::value
Chris@16:         >
Chris@16: {};
Chris@16: 
Chris@16: 
Chris@16: template <typename Polygon>
Chris@16: struct area<Polygon, polygon_tag> : detail::calculate_polygon_sum
Chris@16: {
Chris@16:     template <typename Strategy>
Chris@16:     static inline typename Strategy::return_type apply(Polygon const& polygon, Strategy const& strategy)
Chris@16:     {
Chris@16:         return calculate_polygon_sum::apply<
Chris@16:             typename Strategy::return_type,
Chris@16:             detail::area::ring_area
Chris@16:                 <
Chris@16:                     order_as_direction<geometry::point_order<Polygon>::value>::value,
Chris@16:                     geometry::closure<Polygon>::value
Chris@16:                 >
Chris@16:             >(polygon, strategy);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: 
Chris@101: template <typename MultiGeometry>
Chris@101: struct area<MultiGeometry, multi_polygon_tag> : detail::multi_sum
Chris@101: {
Chris@101:     template <typename Strategy>
Chris@101:     static inline typename Strategy::return_type
Chris@101:     apply(MultiGeometry const& multi, Strategy const& strategy)
Chris@101:     {
Chris@101:         return multi_sum::apply
Chris@101:                <
Chris@101:                    typename Strategy::return_type,
Chris@101:                    area<typename boost::range_value<MultiGeometry>::type>
Chris@101:                >(multi, strategy);
Chris@101:     }
Chris@101: };
Chris@101: 
Chris@101: 
Chris@101: } // namespace dispatch
Chris@101: #endif // DOXYGEN_NO_DISPATCH
Chris@101: 
Chris@101: 
Chris@101: namespace resolve_variant {
Chris@101: 
Chris@16: template <typename Geometry>
Chris@101: struct area
Chris@16: {
Chris@16:     template <typename Strategy>
Chris@16:     static inline typename Strategy::return_type apply(Geometry const& geometry,
Chris@16:                                                        Strategy const& strategy)
Chris@16:     {
Chris@101:         return dispatch::area<Geometry>::apply(geometry, strategy);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template <BOOST_VARIANT_ENUM_PARAMS(typename T)>
Chris@101: struct area<boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)> >
Chris@16: {
Chris@16:     template <typename Strategy>
Chris@16:     struct visitor: boost::static_visitor<typename Strategy::return_type>
Chris@16:     {
Chris@16:         Strategy const& m_strategy;
Chris@16: 
Chris@16:         visitor(Strategy const& strategy): m_strategy(strategy) {}
Chris@16: 
Chris@16:         template <typename Geometry>
Chris@16:         typename Strategy::return_type operator()(Geometry const& geometry) const
Chris@16:         {
Chris@101:             return area<Geometry>::apply(geometry, m_strategy);
Chris@16:         }
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Strategy>
Chris@16:     static inline typename Strategy::return_type
Chris@16:     apply(boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)> const& geometry,
Chris@16:           Strategy const& strategy)
Chris@16:     {
Chris@16:         return boost::apply_visitor(visitor<Strategy>(strategy), geometry);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@101: } // namespace resolve_variant
Chris@16: 
Chris@16: 
Chris@16: /*!
Chris@16: \brief \brief_calc{area}
Chris@16: \ingroup area
Chris@16: \details \details_calc{area}. \details_default_strategy
Chris@16: 
Chris@16: The area algorithm calculates the surface area of all geometries having a surface, namely
Chris@16: box, polygon, ring, multipolygon. The units are the square of the units used for the points
Chris@16: defining the surface. If subject geometry is defined in meters, then area is calculated
Chris@16: in square meters.
Chris@16: 
Chris@16: The area calculation can be done in all three common coordinate systems, Cartesian, Spherical
Chris@16: and Geographic as well.
Chris@16: 
Chris@16: \tparam Geometry \tparam_geometry
Chris@16: \param geometry \param_geometry
Chris@16: \return \return_calc{area}
Chris@16: 
Chris@16: \qbk{[include reference/algorithms/area.qbk]}
Chris@16: \qbk{[heading Examples]}
Chris@16: \qbk{[area] [area_output]}
Chris@16: */
Chris@16: template <typename Geometry>
Chris@16: inline typename default_area_result<Geometry>::type area(Geometry const& geometry)
Chris@16: {
Chris@16:     concept::check<Geometry const>();
Chris@16: 
Chris@101:     // TODO put this into a resolve_strategy stage
Chris@101:     //      (and take the return type from resolve_variant)
Chris@16:     typedef typename point_type<Geometry>::type point_type;
Chris@16:     typedef typename strategy::area::services::default_strategy
Chris@16:         <
Chris@16:             typename cs_tag<point_type>::type,
Chris@16:             point_type
Chris@16:         >::type strategy_type;
Chris@16: 
Chris@16:     // detail::throw_on_empty_input(geometry);
Chris@101: 
Chris@101:     return resolve_variant::area<Geometry>::apply(geometry, strategy_type());
Chris@16: }
Chris@16: 
Chris@16: /*!
Chris@16: \brief \brief_calc{area} \brief_strategy
Chris@16: \ingroup area
Chris@16: \details \details_calc{area} \brief_strategy. \details_strategy_reasons
Chris@16: \tparam Geometry \tparam_geometry
Chris@16: \tparam Strategy \tparam_strategy{Area}
Chris@16: \param geometry \param_geometry
Chris@16: \param strategy \param_strategy{area}
Chris@16: \return \return_calc{area}
Chris@16: 
Chris@16: \qbk{distinguish,with strategy}
Chris@16: 
Chris@16: \qbk{
Chris@16: [include reference/algorithms/area.qbk]
Chris@16: 
Chris@16: [heading Example]
Chris@16: [area_with_strategy]
Chris@16: [area_with_strategy_output]
Chris@16: 
Chris@16: [heading Available Strategies]
Chris@16: \* [link geometry.reference.strategies.strategy_area_surveyor Surveyor (cartesian)]
Chris@16: \* [link geometry.reference.strategies.strategy_area_huiller Huiller (spherical)]
Chris@16: }
Chris@16:  */
Chris@16: template <typename Geometry, typename Strategy>
Chris@16: inline typename Strategy::return_type area(
Chris@16:         Geometry const& geometry, Strategy const& strategy)
Chris@16: {
Chris@16:     concept::check<Geometry const>();
Chris@16: 
Chris@16:     // detail::throw_on_empty_input(geometry);
Chris@101: 
Chris@101:     return resolve_variant::area<Geometry>::apply(geometry, strategy);
Chris@16: }
Chris@16: 
Chris@16: 
Chris@16: }} // namespace boost::geometry
Chris@16: 
Chris@16: 
Chris@16: #endif // BOOST_GEOMETRY_ALGORITHMS_AREA_HPP