Custom Polygon

/*
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 <cassert>
#include <list>
namespace gtl = boost::polygon;
using namespace boost::polygon::operators;
//first lets turn our polygon usage code into a generic
//function parameterized by polygon type
template <typename Polygon>
void test_polygon() {
//lets construct a 10x10 rectangle shaped polygon
typedef typename gtl::polygon_traits<Polygon>::point_type Point;
Point pts[] = {gtl::construct<Point>(0, 0),
gtl::construct<Point>(10, 0),
gtl::construct<Point>(10, 10),
gtl::construct<Point>(0, 10) };
Polygon poly;
gtl::set_points(poly, pts, pts+4);
//now lets see what we can do with this polygon
assert(gtl::area(poly) == 100.0f);
assert(gtl::contains(poly, gtl::construct<Point>(5, 5)));
assert(!gtl::contains(poly, gtl::construct<Point>(15, 5)));
gtl::rectangle_data<int> rect;
assert(gtl::extents(rect, poly)); //get bounding box of poly
assert(gtl::equivalence(rect, poly)); //hey, that's slick
assert(gtl::winding(poly) == gtl::COUNTERCLOCKWISE);
assert(gtl::perimeter(poly) == 40.0f);
//add 5 to all coords of poly
gtl::convolve(poly, gtl::construct<Point>(5, 5));
//multiply all coords of poly by 2
gtl::scale_up(poly, 2);
gtl::set_points(rect, gtl::point_data<int>(10, 10),
gtl::point_data<int>(30, 30));
assert(gtl::equivalence(poly, rect));
}
//Now lets declare our own polygon class
//Oops, we need a point class to support our polygon, lets borrow
//the CPoint example
struct CPoint {
int x;
int y;
};
//we have to get CPoint working with boost polygon to make our polygon
//that uses CPoint working with boost polygon
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;
}
};
} }
//I'm lazy and use the stl everywhere to avoid writing my own classes
//my toy polygon is a std::list<CPoint>
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();
t.insert(t.end(), input_begin, input_end);
return t;
}
};
} }
//now there's nothing left to do but test that our polygon
//works with library interfaces
int main() {
test_polygon<CPolygon>(); //woot!
return 0;
}

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)