algorithms/detail/point_on_border.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002
0003 // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
0004 // Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
0005 // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
0006
0007 // This file was modified by Oracle on 2017-2022.
0008 // Modifications copyright (c) 2017-2022 Oracle and/or its affiliates.
0009 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
0010
0011 // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
0012 // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
0013
0014 // Use, modification and distribution is subject to the Boost Software License,
0015 // Version 1.Dimension. (See accompanying file LICENSE_1_0.txt or copy at
0016 // http://www.boost.org/LICENSE_1_0.txt)
0017
0018 #ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_POINT_ON_BORDER_HPP
0019 #define BOOST_GEOMETRY_ALGORITHMS_DETAIL_POINT_ON_BORDER_HPP
0020
0021
0022 #include <cstddef>
0023
0024 #include <boost/range/begin.hpp>
0025 #include <boost/range/end.hpp>
0026 #include <boost/static_assert.hpp>
0027
0028 #include <boost/geometry/algorithms/assign.hpp>
0029 #include <boost/geometry/algorithms/detail/convert_point_to_point.hpp>
0030 #include <boost/geometry/algorithms/detail/equals/point_point.hpp>
0031 #include <boost/geometry/core/tags.hpp>
0032 #include <boost/geometry/core/point_type.hpp>
0033 #include <boost/geometry/core/ring_type.hpp>
0034 #include <boost/geometry/geometries/concepts/check.hpp>
0035 #include <boost/geometry/util/condition.hpp>
0036 #include <boost/geometry/views/detail/indexed_point_view.hpp>
0037
0038
0039 namespace boost { namespace geometry
0040 {
0041
0042
0043 #ifndef DOXYGEN_NO_DETAIL
0044 namespace detail { namespace point_on_border
0045 {
0046
0047
0048 struct get_point
0049 {
0050     template <typename Destination, typename Source>
0051     static inline bool apply(Destination& destination, Source const& source)
0052     {
0053         detail::conversion::convert_point_to_point(source, destination);
0054         return true;
0055     }
0056 };
0057
0058
0059 struct point_on_range
0060 {
0061     // Version with iterator
0062     template<typename Point, typename Iterator>
0063     static inline bool apply(Point& point, Iterator begin, Iterator end)
0064     {
0065         if (begin == end)
0066         {
0067             return false;
0068         }
0069
0070         detail::conversion::convert_point_to_point(*begin, point);
0071         return true;
0072     }
0073
0074     // Version with range
0075     template<typename Point, typename Range>
0076     static inline bool apply(Point& point, Range const& range)
0077     {
0078         return apply(point, boost::begin(range), boost::end(range));
0079     }
0080 };
0081
0082
0083 struct point_on_polygon
0084 {
0085     template<typename Point, typename Polygon>
0086     static inline bool apply(Point& point, Polygon const& polygon)
0087     {
0088         return point_on_range::apply(point, exterior_ring(polygon));
0089     }
0090 };
0091
0092
0093 struct point_on_segment_or_box
0094 {
0095     template<typename Point, typename SegmentOrBox>
0096     static inline bool apply(Point& point, SegmentOrBox const& segment_or_box)
0097     {
0098         detail::indexed_point_view<SegmentOrBox const, 0> view(segment_or_box);
0099         detail::conversion::convert_point_to_point(view, point);
0100         return true;
0101     }
0102 };
0103
0104
0105 template <typename Policy>
0106 struct point_on_multi
0107 {
0108     template<typename Point, typename MultiGeometry>
0109     static inline bool apply(Point& point, MultiGeometry const& multi)
0110     {
0111         // Take a point on the first multi-geometry
0112         // (i.e. the first that is not empty)
0113         for (auto it = boost::begin(multi); it != boost::end(multi); ++it)
0114         {
0115             if (Policy::apply(point, *it))
0116             {
0117                 return true;
0118             }
0119         }
0120         return false;
0121     }
0122 };
0123
0124
0125 }} // namespace detail::point_on_border
0126 #endif // DOXYGEN_NO_DETAIL
0127
0128
0129 #ifndef DOXYGEN_NO_DISPATCH
0130 namespace dispatch
0131 {
0132
0133
0134 template <typename GeometryTag>
0135 struct point_on_border
0136 {};
0137
0138 template <>
0139 struct point_on_border<point_tag>
0140     : detail::point_on_border::get_point
0141 {};
0142
0143 template <>
0144 struct point_on_border<segment_tag>
0145     : detail::point_on_border::point_on_segment_or_box
0146 {};
0147
0148 template <>
0149 struct point_on_border<linestring_tag>
0150     : detail::point_on_border::point_on_range
0151 {};
0152
0153 template <>
0154 struct point_on_border<ring_tag>
0155     : detail::point_on_border::point_on_range
0156 {};
0157
0158 template <>
0159 struct point_on_border<polygon_tag>
0160     : detail::point_on_border::point_on_polygon
0161 {};
0162
0163 template <>
0164 struct point_on_border<box_tag>
0165     : detail::point_on_border::point_on_segment_or_box
0166 {};
0167
0168
0169 template <>
0170 struct point_on_border<multi_point_tag>
0171     : detail::point_on_border::point_on_range
0172 {};
0173
0174 template <>
0175 struct point_on_border<multi_polygon_tag>
0176     : detail::point_on_border::point_on_multi
0177         <
0178             detail::point_on_border::point_on_polygon
0179         >
0180 {};
0181
0182
0183 template <>
0184 struct point_on_border<multi_linestring_tag>
0185     : detail::point_on_border::point_on_multi
0186         <
0187             detail::point_on_border::point_on_range
0188         >
0189 {};
0190
0191
0192 } // namespace dispatch
0193 #endif // DOXYGEN_NO_DISPATCH
0194
0195
0196 // TODO: We should probably rename this utility because it can return point
0197 //   which is in the interior of a geometry (for PointLike and LinearRings).
0198
0199 /*!
0200 \brief Take point on a border
0201 \ingroup overlay
0202 \tparam Geometry geometry type. This also defines the type of the output point
0203 \param point to assign
0204 \param geometry geometry to take point from
0205 \return TRUE if successful, else false.
0206     It is only false if polygon/line have no points
0207 \note for a polygon, it is always a point on the exterior ring
0208  */
0209 template <typename Point, typename Geometry>
0210 inline bool point_on_border(Point& point, Geometry const& geometry)
0211 {
0212     concepts::check<Point>();
0213     concepts::check<Geometry const>();
0214
0215     return dispatch::point_on_border
0216             <
0217                 typename tag<Geometry>::type
0218             >::apply(point, geometry);
0219 }
0220
0221
0222 }} // namespace boost::geometry
0223
0224
0225 #endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_POINT_ON_BORDER_HPP