283 lines
7.8 KiB
C++
283 lines
7.8 KiB
C++
/*****************************************************************************
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*
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* This file is part of Mapnik (c++ mapping toolkit)
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*
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* Copyright (C) 2013 Artem Pavlenko
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef MAPNIK_POLYGON_CLIPPER_HPP
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#define MAPNIK_POLYGON_CLIPPER_HPP
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// stl
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#include <iostream>
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#include <deque>
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// mapnik
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#include <mapnik/box2d.hpp>
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#include <mapnik/debug.hpp>
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#include <mapnik/geometry.hpp>
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// boost
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#include <boost/tuple/tuple.hpp>
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#include <boost/geometry.hpp>
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#include <boost/geometry/geometries/point_xy.hpp>
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#include <boost/geometry/geometries/box.hpp>
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#include <boost/geometry/geometries/polygon.hpp>
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#include <boost/geometry/geometries/register/point.hpp>
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BOOST_GEOMETRY_REGISTER_POINT_2D(mapnik::coord2d, double, cs::cartesian, x, y)
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// register mapnik::box2d<double>
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namespace boost { namespace geometry { namespace traits
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{
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template<> struct tag<mapnik::box2d<double> > { typedef box_tag type; };
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template<> struct point_type<mapnik::box2d<double> > { typedef mapnik::coord2d type; };
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template <>
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struct indexed_access<mapnik::box2d<double>, min_corner, 0>
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{
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typedef coordinate_type<mapnik::coord2d>::type ct;
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static inline ct get(mapnik::box2d<double> const& b) { return b.minx();}
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static inline void set(mapnik::box2d<double> &b, ct const& value) { b.set_minx(value); }
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};
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template <>
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struct indexed_access<mapnik::box2d<double>, min_corner, 1>
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{
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typedef coordinate_type<mapnik::coord2d>::type ct;
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static inline ct get(mapnik::box2d<double> const& b) { return b.miny();}
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static inline void set(mapnik::box2d<double> &b, ct const& value) { b.set_miny(value); }
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};
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template <>
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struct indexed_access<mapnik::box2d<double>, max_corner, 0>
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{
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typedef coordinate_type<mapnik::coord2d>::type ct;
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static inline ct get(mapnik::box2d<double> const& b) { return b.maxx();}
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static inline void set(mapnik::box2d<double> &b, ct const& value) { b.set_maxx(value); }
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};
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template <>
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struct indexed_access<mapnik::box2d<double>, max_corner, 1>
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{
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typedef coordinate_type<mapnik::coord2d>::type ct;
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static inline ct get(mapnik::box2d<double> const& b) { return b.maxy();}
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static inline void set(mapnik::box2d<double> &b , ct const& value) { b.set_maxy(value); }
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};
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}}}
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namespace mapnik {
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using namespace boost::geometry;
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template <typename Geometry>
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struct polygon_clipper
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{
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typedef mapnik::coord2d point_2d;
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typedef model::polygon<mapnik::coord2d> polygon_2d;
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typedef std::deque<polygon_2d> polygon_list;
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enum
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{
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clip = 1,
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no_clip = 2,
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ignore = 3
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} state_;
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polygon_clipper(Geometry & geom)
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: state_(clip),
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clip_box_(),
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geom_(geom)
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{
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}
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polygon_clipper(box2d<double> const& clip_box, Geometry & geom)
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:state_(clip),
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clip_box_(clip_box),
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geom_(geom)
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{
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init();
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}
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void set_clip_box(box2d<double> const& clip_box)
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{
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state_ = clip;
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clip_box_ = clip_box;
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init();
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}
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unsigned type() const
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{
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return geom_.type();
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}
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void rewind(unsigned path_id)
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{
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if (state_ == clip) output_.rewind(path_id);
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else geom_.rewind(path_id);
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}
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unsigned vertex (double * x, double * y)
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{
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switch (state_)
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{
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case clip:
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return output_.vertex(x,y);
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case no_clip:
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return geom_.vertex(x,y);
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case ignore:
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return SEG_END;
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}
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return SEG_END;
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}
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private:
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void init()
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{
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geom_.rewind(0);
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box2d<double> bbox = geom_.envelope();
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if (clip_box_.contains(bbox))
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{
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// shortcut to original geometry (no-clipping)
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state_ = no_clip;
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return;
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}
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else if (!clip_box_.intersects(bbox))
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{
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// polygon is outside of clipping box
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state_ = ignore;
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return;
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}
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polygon_2d subject_poly;
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double x,y;
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double prev_x, prev_y;
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geom_.rewind(0);
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unsigned ring_count = 0;
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while (true)
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{
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unsigned cmd = geom_.vertex(&x,&y);
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if (cmd == SEG_END) break;
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if (cmd == SEG_MOVETO)
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{
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prev_x = x;
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prev_y = y;
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if (ring_count == 0)
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{
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append(subject_poly, make<point_2d>(x,y));
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}
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else
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{
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subject_poly.inners().push_back(polygon_2d::inner_container_type::value_type());
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append(subject_poly.inners().back(),make<point_2d>(x,y));
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}
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++ring_count;
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}
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else if (cmd == SEG_LINETO)
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{
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if (std::abs(x - prev_x) < 1e-12 && std::abs(y - prev_y) < 1e-12)
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{
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#ifdef MAPNIK_LOG
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MAPNIK_LOG_WARN(polygon_clipper)
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<< std::setprecision(12) << "coincident vertices:(" << prev_x << ","
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<< prev_y << ") , (" << x << "," << y << ")";
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#endif
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continue;
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}
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prev_x = x;
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prev_y = y;
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if (ring_count == 1)
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{
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append(subject_poly, make<point_2d>(x,y));
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}
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else
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{
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append(subject_poly.inners().back(),make<point_2d>(x,y));
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}
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}
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}
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polygon_list clipped_polygons;
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#ifdef MAPNIK_LOG
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double area = boost::geometry::area(subject_poly);
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if (area < 0)
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{
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MAPNIK_LOG_ERROR(polygon_clipper) << "negative area detected for polygon indicating incorrect winding order";
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}
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#endif
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try
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{
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boost::geometry::intersection(clip_box_, subject_poly, clipped_polygons);
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}
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catch (boost::geometry::exception const& ex)
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{
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std::cerr << ex.what() << std::endl;
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}
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for (polygon_2d const& poly : clipped_polygons)
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{
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bool move_to = true;
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for (point_2d const& c : boost::geometry::exterior_ring(poly))
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{
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if (move_to)
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{
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move_to = false;
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output_.move_to(c.x,c.y);
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}
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else
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{
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output_.line_to(c.x,c.y);
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}
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}
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output_.close_path();
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// interior rings
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for (polygon_2d::inner_container_type::value_type const& ring : boost::geometry::interior_rings(poly))
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{
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move_to = true;
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for (point_2d const& c : ring)
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{
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if (move_to)
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{
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move_to = false;
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output_.move_to(c.x,c.y);
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}
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else
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{
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output_.line_to(c.x,c.y);
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}
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}
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output_.close_path();
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}
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}
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}
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box2d<double> clip_box_;
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Geometry & geom_;
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mapnik::geometry_type output_;
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};
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}
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#endif //MAPNIK_POLYGON_CLIPPER_HPP
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