1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283 |
- // Boost.Geometry (aka GGL, Generic Geometry Library)
- // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
- // Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
- // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
- // 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)
- //
- // Custom Triangle Example
- #include <iostream>
- #include <boost/array.hpp>
- #include <boost/geometry/algorithms/area.hpp>
- #include <boost/geometry/algorithms/centroid.hpp>
- #include <boost/geometry/geometries/point_xy.hpp>
- #include <boost/geometry/geometries/register/ring.hpp>
- #include <boost/geometry/strategies/strategies.hpp>
- #include <boost/geometry/io/dsv/write.hpp>
- struct triangle : public boost::array<boost::geometry::model::d2::point_xy<double>, 4>
- {
- inline void close()
- {
- (*this)[3] = (*this)[0];
- }
- };
- // Register triangle as a ring
- BOOST_GEOMETRY_REGISTER_RING(triangle)
- // Specializations of algorithms, where useful. If not specialized the default ones
- // (for linear rings) will be used for triangle. Which is OK as long as the triangle
- // is closed, that means, has 4 points (the last one being the first).
- namespace boost { namespace geometry {
- template<>
- inline double area<triangle>(const triangle& t)
- {
- /* C
- / \
- / \
- A-----B
- ((Bx - Ax) * (Cy - Ay)) - ((Cx - Ax) * (By - Ay))
- -------------------------------------------------
- 2
- */
- return 0.5 * ((t[1].x() - t[0].x()) * (t[2].y() - t[0].y())
- - (t[2].x() - t[0].x()) * (t[1].y() - t[0].y()));
- }
- }} // namespace boost::geometry
- int main()
- {
- triangle t;
- t[0].x(0);
- t[0].y(0);
- t[1].x(5);
- t[1].y(0);
- t[2].x(2.5);
- t[2].y(2.5);
- t.close();
- std::cout << "Triangle: " << boost::geometry::dsv(t) << std::endl;
- std::cout << "Area: " << boost::geometry::area(t) << std::endl;
- boost::geometry::model::d2::point_xy<double> c;
- boost::geometry::centroid(t, c);
- std::cout << "Centroid: " << boost::geometry::dsv(c) << std::endl;
- return 0;
- }
|