ceph/src/boost/libs/geometry/include/boost/geometry/extensions/algorithms/inverse.hpp

   1 // Boost.Geometry (aka GGL, Generic Geometry Library)
   2 //
   3 // Copyright (c) 2015 Barend Gehrels, Amsterdam, the Netherlands.
   4
   5 // Use, modification and distribution is subject to the Boost Software License,
   6 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   7 // http://www.boost.org/LICENSE_1_0.txt)
   8
   9
  10 #ifndef BOOST_GEOMETRY_ALGORITHMS_INVERSE_HPP
  11 #define BOOST_GEOMETRY_ALGORITHMS_INVERSE_HPP
  12
  13 #include <boost/geometry.hpp>
  14
  15 namespace boost { namespace geometry
  16 {
  17
  18 // TODO: this is shared with sectionalize, move to somewhere else (assign?)
  19 template <typename Box, typename Value>
  20 inline void enlarge_box(Box& box, Value value)
  21 {
  22     geometry::set<0, 0>(box, geometry::get<0, 0>(box) - value);
  23     geometry::set<0, 1>(box, geometry::get<0, 1>(box) - value);
  24     geometry::set<1, 0>(box, geometry::get<1, 0>(box) + value);
  25     geometry::set<1, 1>(box, geometry::get<1, 1>(box) + value);
  26 }
  27
  28 // TODO: when this might be moved outside extensions it should of course
  29 // input/output a Geometry, instead of a WKT
  30 template <typename Geometry, typename Value>
  31 inline std::string inverse(std::string const& wkt, Value margin)
  32 {
  33     Geometry geometry;
  34     read_wkt(wkt, geometry);
  35
  36     geometry::correct(geometry);
  37
  38     geometry::model::box<typename point_type<Geometry>::type> env;
  39     geometry::envelope(geometry, env);
  40
  41     // Make its envelope a bit larger
  42     enlarge_box(env, margin);
  43
  44     Geometry env_as_polygon;
  45     geometry::convert(env, env_as_polygon);
  46
  47     Geometry inversed_result;
  48     geometry::difference(env_as_polygon, geometry, inversed_result);
  49
  50     std::ostringstream out;
  51
  52     out << geometry::wkt(inversed_result);
  53     return out.str();
  54 }
  55
  56 }} // namespace boost::geometry
  57
  58
  59 #endif // BOOST_GEOMETRY_ALGORITHMS_INVERSE_HPP