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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 |