// Boost.Geometry (aka GGL, Generic Geometry Library) // QuickBook Example // Copyright (c) 2011-2012 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) //[difference //` Shows how to subtract one polygon from another polygon #include <iostream> #include <list> #include <boost/geometry.hpp> #include <boost/geometry/geometries/point_xy.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/io/wkt/wkt.hpp> #include <boost/foreach.hpp> /*<-*/ #include "create_svg_overlay.hpp" /*->*/ int main() { typedef boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > polygon; polygon green, blue; boost::geometry::read_wkt( "POLYGON((2 1.3,2.4 1.7,2.8 1.8,3.4 1.2,3.7 1.6,3.4 2,4.1 3,5.3 2.6,5.4 1.2,4.9 0.8,2.9 0.7,2 1.3)" "(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))", green); boost::geometry::read_wkt( "POLYGON((4.0 -0.5 , 3.5 1.0 , 2.0 1.5 , 3.5 2.0 , 4.0 3.5 , 4.5 2.0 , 6.0 1.5 , 4.5 1.0 , 4.0 -0.5))", blue); std::list<polygon> output; boost::geometry::difference(green, blue, output); int i = 0; std::cout << "green - blue:" << std::endl; BOOST_FOREACH(polygon const& p, output) { std::cout << i++ << ": " << boost::geometry::area(p) << std::endl; } /*<-*/ create_svg("difference_a.svg", green, blue, output); /*->*/ output.clear(); boost::geometry::difference(blue, green, output); i = 0; std::cout << "blue - green:" << std::endl; BOOST_FOREACH(polygon const& p, output) { std::cout << i++ << ": " << boost::geometry::area(p) << std::endl; } /*<-*/ create_svg("difference_b.svg", green, blue, output); /*->*/ return 0; } //] //[difference_output /*` Output: [pre green - blue: 0: 0.02375 1: 0.542951 2: 0.0149697 3: 0.226855 4: 0.839424 [$img/algorithms/difference_a.png] blue - green: 0: 0.525154 1: 0.015 2: 0.181136 3: 0.128798 4: 0.340083 5: 0.307778 [$img/algorithms/difference_b.png] ] */ //]