Custom Polygon Set

/*
Copyright 2008 Intel Corporation
Use, modification and distribution are 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).
*/
#include <boost/polygon/polygon.hpp>
#include <list>
#include <time.h>
#include <cassert>
#include <deque>
#include <iostream>
namespace gtl = boost::polygon;
using namespace boost::polygon::operators;
//once again we make our usage of the library generic
//and parameterize it on the polygon set type
template <typename PolygonSet>
void test_polygon_set() {
using namespace gtl;
PolygonSet ps;
ps += rectangle_data<int>(0, 0, 10, 10);
PolygonSet ps2;
ps2 += rectangle_data<int>(5, 5, 15, 15);
PolygonSet ps3;
assign(ps3, ps * ps2);
PolygonSet ps4;
ps4 += ps + ps2;
assert(area(ps4) == area(ps) + area(ps2) - area(ps3));
assert(equivalence((ps + ps2) - (ps * ps2), ps ^ ps2));
rectangle_data<int> rect;
assert(extents(rect, ps ^ ps2));
assert(area(rect) == 225);
assert(area(rect ^ (ps ^ ps2)) == area(rect) - area(ps ^ ps2));
}
//first thing is first, lets include all the code from previous examples
//the CPoint example
struct CPoint {
int x;
int y;
};
namespace boost { namespace polygon {
template <>
struct geometry_concept<CPoint> { typedef point_concept type; };
template <>
struct point_traits<CPoint> {
typedef int coordinate_type;
static inline coordinate_type get(const CPoint& point,
orientation_2d orient) {
if(orient == HORIZONTAL)
return point.x;
return point.y;
}
};
template <>
struct point_mutable_traits<CPoint> {
static inline void set(CPoint& point, orientation_2d orient, int value) {
if(orient == HORIZONTAL)
point.x = value;
else
point.y = value;
}
static inline CPoint construct(int x_value, int y_value) {
CPoint retval;
retval.x = x_value;
retval.y = y_value;
return retval;
}
};
} }
//the CPolygon example
typedef std::list<CPoint> CPolygon;
//we need to specialize our polygon concept mapping in boost polygon
namespace boost { namespace polygon {
//first register CPolygon as a polygon_concept type
template <>
struct geometry_concept<CPolygon>{ typedef polygon_concept type; };
template <>
struct polygon_traits<CPolygon> {
typedef int coordinate_type;
typedef CPolygon::const_iterator iterator_type;
typedef CPoint point_type;
// Get the begin iterator
static inline iterator_type begin_points(const CPolygon& t) {
return t.begin();
}
// Get the end iterator
static inline iterator_type end_points(const CPolygon& t) {
return t.end();
}
// Get the number of sides of the polygon
static inline std::size_t size(const CPolygon& t) {
return t.size();
}
// Get the winding direction of the polygon
static inline winding_direction winding(const CPolygon& t) {
return unknown_winding;
}
};
template <>
struct polygon_mutable_traits<CPolygon> {
//expects stl style iterators
template <typename iT>
static inline CPolygon& set_points(CPolygon& t,
iT input_begin, iT input_end) {
t.clear();
while(input_begin != input_end) {
t.push_back(CPoint());
gtl::assign(t.back(), *input_begin);
++input_begin;
}
return t;
}
};
} }
//OK, finally we get to declare our own polygon set type
typedef std::deque<CPolygon> CPolygonSet;
//deque isn't automatically a polygon set in the library
//because it is a standard container there is a shortcut
//for mapping it to polygon set concept, but I'll do it
//the long way that you would use in the general case.
namespace boost { namespace polygon {
//first we register CPolygonSet as a polygon set
template <>
struct geometry_concept<CPolygonSet> { typedef polygon_set_concept type; };
//next we map to the concept through traits
template <>
struct polygon_set_traits<CPolygonSet> {
typedef int coordinate_type;
typedef CPolygonSet::const_iterator iterator_type;
typedef CPolygonSet operator_arg_type;
static inline iterator_type begin(const CPolygonSet& polygon_set) {
return polygon_set.begin();
}
static inline iterator_type end(const CPolygonSet& polygon_set) {
return polygon_set.end();
}
//don't worry about these, just return false from them
static inline bool clean(const CPolygonSet& polygon_set) { return false; }
static inline bool sorted(const CPolygonSet& polygon_set) { return false; }
};
template <>
struct polygon_set_mutable_traits<CPolygonSet> {
template <typename input_iterator_type>
static inline void set(CPolygonSet& polygon_set, input_iterator_type input_begin, input_iterator_type input_end) {
polygon_set.clear();
//this is kind of cheesy. I am copying the unknown input geometry
//into my own polygon set and then calling get to populate the
//deque
polygon_set_data<int> ps;
ps.insert(input_begin, input_end);
ps.get(polygon_set);
//if you had your own odd-ball polygon set you would probably have
//to iterate through each polygon at this point and do something
//extra
}
};
} }
int main() {
long long c1 = clock();
for(int i = 0; i < 1000; ++i)
test_polygon_set<CPolygonSet>();
long long c2 = clock();
for(int i = 0; i < 1000; ++i)
test_polygon_set<gtl::polygon_set_data<int> >();
long long c3 = clock();
long long diff1 = c2 - c1;
long long diff2 = c3 - c2;
if(diff1 > 0 && diff2)
std::cout << "library polygon_set_data is " << float(diff1)/float(diff2) << "X faster than custom polygon set deque of CPolygon" << std::endl;
else
std::cout << "operation was too fast" << std::endl;
return 0;
}

//Now you know how to map your own data type to polygon set concept
//Now you also know how to make your application code that operates on geometry
//data type agnostic from point through polygon set

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)