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// 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.
// 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_POINT_IN_POLY_CROSSINGS_MULTIPLY_HPP
#define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_POINT_IN_POLY_CROSSINGS_MULTIPLY_HPP
#include <boost/geometry/core/coordinate_type.hpp>
#include <boost/geometry/util/select_calculation_type.hpp>
namespace boost { namespace geometry
{
namespace strategy { namespace within
{
/*!
\brief Within detection using cross counting,
\ingroup strategies
\tparam Point \tparam_point
\tparam PointOfSegment \tparam_segment_point
\tparam CalculationType \tparam_calculation
\see http://tog.acm.org/resources/GraphicsGems/gemsiv/ptpoly_haines/ptinpoly.c
\note Does NOT work correctly for point ON border
\qbk{
[heading See also]
[link geometry.reference.algorithms.within.within_3_with_strategy within (with strategy)]
}
*/
template
<
typename Point,
typename PointOfSegment = Point,
typename CalculationType = void
>
class crossings_multiply
{
typedef typename select_calculation_type
<
Point,
PointOfSegment,
CalculationType
>::type calculation_type;
class flags
{
bool inside_flag;
bool first;
bool yflag0;
public :
friend class crossings_multiply;
inline flags()
: inside_flag(false)
, first(true)
, yflag0(false)
{}
};
public :
typedef Point point_type;
typedef PointOfSegment segment_point_type;
typedef flags state_type;
static inline bool apply(Point const& point,
PointOfSegment const& seg1, PointOfSegment const& seg2,
flags& state)
{
calculation_type const tx = get<0>(point);
calculation_type const ty = get<1>(point);
calculation_type const x0 = get<0>(seg1);
calculation_type const y0 = get<1>(seg1);
calculation_type const x1 = get<0>(seg2);
calculation_type const y1 = get<1>(seg2);
if (state.first)
{
state.first = false;
state.yflag0 = y0 >= ty;
}
bool yflag1 = y1 >= ty;
if (state.yflag0 != yflag1)
{
if ( ((y1-ty) * (x0-x1) >= (x1-tx) * (y0-y1)) == yflag1 )
{
state.inside_flag = ! state.inside_flag;
}
}
state.yflag0 = yflag1;
return true;
}
static inline int result(flags const& state)
{
return state.inside_flag ? 1 : -1;
}
};
}} // namespace strategy::within
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_POINT_IN_POLY_CROSSINGS_MULTIPLY_HPP
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