boost/geometry/algorithms/buffer.hpp

Go to the documentation of this file.

// Boost.Geometry (aka GGL, Generic Geometry Library)
//
// Copyright Barend Gehrels 2007-2009, Geodan, Amsterdam, the Netherlands.
// Copyright Bruno Lalande 2008, 2009
// 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)

#ifndef BOOST_GEOMETRY_ALGORITHMS_BUFFER_HPP
#define BOOST_GEOMETRY_ALGORITHMS_BUFFER_HPP

#include <cstddef>

#include <boost/numeric/conversion/cast.hpp>

#include <boost/geometry/geometries/concepts/check.hpp>

#include <boost/geometry/arithmetic/arithmetic.hpp>

namespace boost { namespace geometry
{

#ifndef DOXYGEN_NO_DETAIL
namespace detail { namespace buffer {

template <typename BoxIn, typename BoxOut, typename T, std::size_t C, std::size_t D, std::size_t N>
struct box_loop
{
    typedef typename coordinate_type<BoxOut>::type coordinate_type;

    static inline void apply(BoxIn const& box_in, T const& distance, BoxOut& box_out)
    {
        set<C, D>(box_out, boost::numeric_cast<coordinate_type>(get<C, D>(box_in) + distance));
        box_loop<BoxIn, BoxOut, T, C, D + 1, N>::apply(box_in, distance, box_out);
    }
};

template <typename BoxIn, typename BoxOut, typename T, std::size_t C, std::size_t N>
struct box_loop<BoxIn, BoxOut, T, C, N, N>
{
    static inline void apply(BoxIn const&, T const&, BoxOut&) {}
};

// Extends a box with the same amount in all directions
template<typename BoxIn, typename BoxOut, typename T>
inline void buffer_box(BoxIn const& box_in, T const& distance, BoxOut& box_out)
{
    assert_dimension_equal<BoxIn, BoxOut>();

    static const std::size_t N = dimension<BoxIn>::value;

    box_loop<BoxIn, BoxOut, T, min_corner, 0, N>::apply(box_in, -distance, box_out);
    box_loop<BoxIn, BoxOut, T, max_corner, 0, N>::apply(box_in, +distance, box_out);
}

}} // namespace detail::buffer
#endif // DOXYGEN_NO_DETAIL

#ifndef DOXYGEN_NO_DISPATCH
namespace dispatch
{

template <typename TagIn, typename TagOut, typename Input, typename T, typename Output>
struct buffer {};


template <typename BoxIn, typename T, typename BoxOut>
struct buffer<box_tag, box_tag, BoxIn, T, BoxOut>
{
    static inline void apply(BoxIn const& box_in, T const& distance,
                T const& chord_length, BoxIn& box_out)
    {
        detail::buffer::buffer_box(box_in, distance, box_out);
    }
};

// Many things to do. Point is easy, other geometries require self intersections
// For point, note that it should output as a polygon (like the rest). Buffers
// of a set of geometries are often lateron combined using a "dissolve" operation.
// Two points close to each other get a combined kidney shaped buffer then.

} // namespace dispatch
#endif // DOXYGEN_NO_DISPATCH


template <typename Input, typename Output, typename T>
inline void buffer(Input const& geometry_in, Output& geometry_out,
            T const& distance, T const& chord_length = -1)
{
    concept::check<const Input>();
    concept::check<Output>();

    dispatch::buffer
        <
            typename tag<Input>::type,
            typename tag<Output>::type,
            Input,
            T,
            Output
        >::apply(geometry_in, distance, chord_length, geometry_out);
}

template <typename Output, typename Input, typename T>
Output make_buffer(Input const& geometry, T const& distance, T const& chord_length = -1)
{
    concept::check<const Input>();
    concept::check<Output>();

    Output geometry_out;

    dispatch::buffer
        <
            typename tag<Input>::type,
            typename tag<Output>::type,
            Input,
            T,
            Output
        >::apply(geometry, distance, chord_length, geometry_out);

    return geometry_out;
}

}} // namespace boost::geometry

#endif // BOOST_GEOMETRY_ALGORITHMS_BUFFER_HPP

---

December 1, 2009

Copyright © 1995-2009 Barend Gehrels, Geodan, Amsterdam Copyright © 2008-2009 Bruno Lalande, Paris Copyright © 2009 Mateusz Loskot, Cadcorp, London