| // Boost.Geometry (aka GGL, Generic Geometry Library) |
| // QuickBook Example |
| |
| // Copyright (c) 2011 Barend Gehrels, Amsterdam, the Netherlands. |
| |
| // Use, modification and distribution is subject to the Boost Software License, |
| // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt) |
| |
| //[correct |
| //` Shows how to correct a polygon with respect to its orientation and closure |
| |
| #include <iostream> |
| |
| #include <boost/geometry.hpp> |
| #include <boost/geometry/geometries/polygon.hpp> |
| #include <boost/geometry/geometries/adapted/boost_tuple.hpp> |
| |
| BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian) |
| |
| #include <boost/assign.hpp> |
| |
| int main() |
| { |
| using boost::assign::tuple_list_of; |
| |
| typedef boost::geometry::model::polygon |
| < |
| boost::tuple<int, int> |
| > clockwise_closed_polygon; |
| |
| clockwise_closed_polygon cwcp; |
| |
| // Fill it counterclockwise (so wrongly), forgetting the closing point |
| boost::geometry::exterior_ring(cwcp) = tuple_list_of(0, 0)(10, 10)(0, 9); |
| |
| // Add a counterclockwise closed inner ring (this is correct) |
| boost::geometry::interior_rings(cwcp).push_back(tuple_list_of(1, 2)(4, 6)(2, 8)(1, 2)); |
| |
| // Its area should be negative (because of wrong orientation) |
| // and wrong (because of omitted closing point) |
| double area_before = boost::geometry::area(cwcp); |
| |
| // Correct it! |
| boost::geometry::correct(cwcp); |
| |
| // Check its new area |
| double area_after = boost::geometry::area(cwcp); |
| |
| // And output it |
| std::cout << boost::geometry::dsv(cwcp) << std::endl; |
| std::cout << area_before << " -> " << area_after << std::endl; |
| |
| return 0; |
| } |
| |
| //] |
| |
| |
| //[correct_output |
| /*` |
| Output: |
| [pre |
| (((0, 0), (0, 9), (10, 10), (0, 0)), ((1, 2), (4, 6), (2, 8), (1, 2))) |
| -7 -> 38 |
| ] |
| */ |
| //] |