153 lines
4.1 KiB
C++
153 lines
4.1 KiB
C++
// 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.
|
|
|
|
// This file was modified by Oracle on 2016, 2017.
|
|
// Modifications copyright (c) 2016-2017, Oracle and/or its affiliates.
|
|
|
|
// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
|
|
|
|
// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
|
|
// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
|
|
|
|
// 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_STRATEGIES_CARTESIAN_AREA_SURVEYOR_HPP
|
|
#define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_AREA_SURVEYOR_HPP
|
|
|
|
|
|
#include <boost/mpl/if.hpp>
|
|
|
|
//#include <boost/geometry/arithmetic/determinant.hpp>
|
|
#include <boost/geometry/core/coordinate_type.hpp>
|
|
#include <boost/geometry/core/coordinate_dimension.hpp>
|
|
#include <boost/geometry/strategies/area.hpp>
|
|
#include <boost/geometry/util/select_most_precise.hpp>
|
|
|
|
|
|
namespace boost { namespace geometry
|
|
{
|
|
|
|
namespace strategy { namespace area
|
|
{
|
|
|
|
/*!
|
|
\brief Area calculation for cartesian points
|
|
\ingroup strategies
|
|
\details Calculates area using the Surveyor's formula, a well-known
|
|
triangulation algorithm
|
|
\tparam PointOfSegment \tparam_segment_point
|
|
\tparam CalculationType \tparam_calculation
|
|
|
|
\qbk{
|
|
[heading See also]
|
|
[link geometry.reference.algorithms.area.area_2_with_strategy area (with strategy)]
|
|
}
|
|
|
|
*/
|
|
template
|
|
<
|
|
typename PointOfSegment,
|
|
typename CalculationType = void
|
|
>
|
|
class surveyor
|
|
{
|
|
public :
|
|
// If user specified a calculation type, use that type,
|
|
// whatever it is and whatever the point-type is.
|
|
// Else, use the pointtype, but at least double
|
|
typedef typename
|
|
boost::mpl::if_c
|
|
<
|
|
boost::is_void<CalculationType>::type::value,
|
|
typename select_most_precise
|
|
<
|
|
typename coordinate_type<PointOfSegment>::type,
|
|
double
|
|
>::type,
|
|
CalculationType
|
|
>::type return_type;
|
|
|
|
|
|
private :
|
|
|
|
class summation
|
|
{
|
|
friend class surveyor;
|
|
|
|
return_type sum;
|
|
public :
|
|
|
|
inline summation() : sum(return_type())
|
|
{
|
|
// Strategy supports only 2D areas
|
|
assert_dimension<PointOfSegment, 2>();
|
|
}
|
|
inline return_type area() const
|
|
{
|
|
return_type result = sum;
|
|
return_type const two = 2;
|
|
result /= two;
|
|
return result;
|
|
}
|
|
};
|
|
|
|
public :
|
|
typedef summation state_type;
|
|
typedef PointOfSegment segment_point_type;
|
|
|
|
static inline void apply(PointOfSegment const& p1,
|
|
PointOfSegment const& p2,
|
|
summation& state)
|
|
{
|
|
// Below formulas are equivalent, however the two lower ones
|
|
// suffer less from accuracy loss for great values of coordinates.
|
|
// See: https://svn.boost.org/trac/boost/ticket/11928
|
|
|
|
// SUM += x2 * y1 - x1 * y2;
|
|
// state.sum += detail::determinant<return_type>(p2, p1);
|
|
|
|
// SUM += (x2 - x1) * (y2 + y1)
|
|
//state.sum += (return_type(get<0>(p2)) - return_type(get<0>(p1)))
|
|
// * (return_type(get<1>(p2)) + return_type(get<1>(p1)));
|
|
|
|
// SUM += (x1 + x2) * (y1 - y2)
|
|
state.sum += (return_type(get<0>(p1)) + return_type(get<0>(p2)))
|
|
* (return_type(get<1>(p1)) - return_type(get<1>(p2)));
|
|
}
|
|
|
|
static inline return_type result(summation const& state)
|
|
{
|
|
return state.area();
|
|
}
|
|
|
|
};
|
|
|
|
#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
|
|
|
|
namespace services
|
|
{
|
|
template <typename Point>
|
|
struct default_strategy<cartesian_tag, Point>
|
|
{
|
|
typedef strategy::area::surveyor<Point> type;
|
|
};
|
|
|
|
} // namespace services
|
|
|
|
#endif // DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
|
|
|
|
|
|
}} // namespace strategy::area
|
|
|
|
|
|
|
|
}} // namespace boost::geometry
|
|
|
|
|
|
#endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_AREA_SURVEYOR_HPP
|