Connectivity Extraction Usage

#include <boost/polygon/polygon.hpp>
#include <cassert>
namespace gtl = boost::polygon;
//This function works with both the 90 and 45 versions
//of connectivity extraction algroithm
template <typename ce_type>
void test_ce() {
//first we create an object to do the connectivity extraction
ce_type ce;
//create some test data
std::vector<gtl::rectangle_data<int> > test_data;
test_data.push_back(gtl::rectangle_data<int>(10, 10, 90, 90));
test_data.push_back(gtl::rectangle_data<int>(0, 0, 20, 20));
test_data.push_back(gtl::rectangle_data<int>(80, 0, 100, 20));
test_data.push_back(gtl::rectangle_data<int>(0, 80, 20, 100));
test_data.push_back(gtl::rectangle_data<int>(80, 80, 100, 100));
//There is one big square and four little squares covering each
//of its corners.
for(unsigned int i = 0; i < test_data.size(); ++i) {
//insert returns an id starting at zero and incrementing
//with each call
assert(ce.insert(test_data[i]) == i);
}
//notice that ids returned by ce.insert happen to match
//index into vector of inputs in this case
//make sure the vector graph has elements for our nodes
std::vector<std::set<int> > graph(test_data.size());
//populate the graph with edge data
ce.extract(graph);
//make a map type graph to compare results
std::map<int, std::set<int> > map_graph;
ce.extract(map_graph);
assert(map_graph.size() && map_graph.size() == graph.size());
for(unsigned int i = 0; i < graph.size(); ++i) {
assert(graph[i] == map_graph[i]);
if(i == 0)
assert(graph[i].size() == 4); //four little squares
else
assert(graph[i].size() == 1); //each little toches the big square
}
}
int main() {
test_ce<gtl::connectivity_extraction_90<int> >();
test_ce<gtl::connectivity_extraction_45<int> >();
return 0;
}
//Now you know how to use the connectivity extraction algorithm
//to extract the connectivity graph for overlapping geometry

Copyright: | Copyright © Intel Corporation 2008-2010.
License: | Distributed under 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)