strategies/cartesian/buffer_point_circle.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002
0003 // Copyright (c) 2012-2015 Barend Gehrels, Amsterdam, the Netherlands.
0004
0005 // This file was modified by Oracle on 2015, 2018.
0006 // Modifications copyright (c) 2015, 2018, Oracle and/or its affiliates.
0007
0008 // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
0009 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
0010
0011 // Use, modification and distribution is subject to the Boost Software License,
0012 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0013 // http://www.boost.org/LICENSE_1_0.txt)
0014
0015 #ifndef BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_POINT_CIRCLE_HPP
0016 #define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_POINT_CIRCLE_HPP
0017
0018 #include <cstddef>
0019
0020 #include <boost/range/value_type.hpp>
0021
0022 #include <boost/geometry/core/access.hpp>
0023 #include <boost/geometry/core/coordinate_type.hpp>
0024
0025 #include <boost/geometry/strategies/buffer.hpp>
0026
0027 #include <boost/geometry/util/math.hpp>
0028 #include <boost/geometry/util/select_most_precise.hpp>
0029
0030 namespace boost { namespace geometry
0031 {
0032
0033 namespace strategy { namespace buffer
0034 {
0035
0036 /*!
0037 \brief Create a circular buffer around a point
0038 \ingroup strategies
0039 \details This strategy can be used as PointStrategy for the buffer algorithm.
0040     It creates a circular buffer around a point. It can be applied
0041     for points and multi_points, but also for a linestring (if it is degenerate,
0042     so consisting of only one point) and for polygons (if it is degenerate).
0043     This strategy is only applicable for Cartesian coordinate systems.
0044
0045 \qbk{
0046 [heading Example]
0047 [buffer_point_circle]
0048 [heading Output]
0049 [$img/strategies/buffer_point_circle.png]
0050 [heading See also]
0051 \* [link geometry.reference.algorithms.buffer.buffer_7_with_strategies buffer (with strategies)]
0052 \* [link geometry.reference.strategies.strategy_buffer_point_square point_square]
0053 \* [link geometry.reference.strategies.strategy_buffer_geographic_point_circle geographic_point_circle]
0054 }
0055  */
0056 class point_circle
0057 {
0058 public :
0059     //! \brief Constructs the strategy
0060     //! \param count Number of points (minimum 3) for the created circle
0061     explicit point_circle(std::size_t count = default_points_per_circle)
0062         : m_count(get_point_count_for_circle(count))
0063     {}
0064
0065 #ifndef DOXYGEN_SHOULD_SKIP_THIS
0066     //! Fills output_range with a circle around point using distance_strategy
0067     template
0068     <
0069         typename Point,
0070         typename OutputRange,
0071         typename DistanceStrategy
0072     >
0073     inline void apply(Point const& point,
0074                 DistanceStrategy const& distance_strategy,
0075                 OutputRange& output_range) const
0076     {
0077         using output_point_type = typename boost::range_value<OutputRange>::type;
0078
0079         using promoted_type = typename geometry::select_most_precise
0080             <
0081                 geometry::coordinate_type_t<Point>,
0082                 geometry::coordinate_type_t<output_point_type>,
0083                 double
0084             >::type;
0085
0086         promoted_type const buffer_distance = distance_strategy.apply(point, point,
0087                         strategy::buffer::buffer_side_left);
0088
0089         promoted_type const two_pi = geometry::math::two_pi<promoted_type>();
0090
0091         promoted_type const diff = two_pi / promoted_type(m_count);
0092         promoted_type a = 0;
0093
0094         for (std::size_t i = 0; i < m_count; i++, a -= diff)
0095         {
0096             output_point_type p;
0097             set<0>(p, get<0>(point) + buffer_distance * cos(a));
0098             set<1>(p, get<1>(point) + buffer_distance * sin(a));
0099             output_range.push_back(p);
0100         }
0101
0102         // Close it:
0103         output_range.push_back(output_range.front());
0104     }
0105 #endif // DOXYGEN_SHOULD_SKIP_THIS
0106
0107 private :
0108     std::size_t m_count;
0109 };
0110
0111
0112 }} // namespace strategy::buffer
0113
0114 }} // namespace boost::geometry
0115
0116 #endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_BUFFER_POINT_CIRCLE_HPP