408 lines
10 KiB
C++
408 lines
10 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) 2014 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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*****************************************************************************/
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#ifndef MAPNIK_OFFSET_CONVERTER_HPP
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#define MAPNIK_OFFSET_CONVERTER_HPP
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#ifdef MAPNIK_LOG
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#include <mapnik/debug.hpp>
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#endif
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#include <mapnik/global.hpp>
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#include <mapnik/config.hpp>
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#include <mapnik/vertex.hpp>
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// stl
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#include <cmath>
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#include <vector>
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#include <cstddef>
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namespace mapnik
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{
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template <typename Geometry>
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struct MAPNIK_DECL offset_converter
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{
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using size_type = std::size_t;
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offset_converter(Geometry & geom)
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: geom_(geom)
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, offset_(0.0)
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, threshold_(8.0)
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, half_turn_segments_(16)
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, status_(initial)
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, pre_first_(vertex2d::no_init)
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, pre_(vertex2d::no_init)
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, cur_(vertex2d::no_init)
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{}
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enum status
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{
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initial,
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process
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};
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unsigned type() const
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{
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return static_cast<unsigned>(geom_.type());
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}
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double get_offset() const
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{
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return offset_;
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}
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double get_threshold() const
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{
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return threshold_;
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}
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void set_offset(double value)
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{
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if (offset_ != value)
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{
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offset_ = value;
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reset();
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}
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}
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void set_threshold(double value)
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{
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threshold_ = value;
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// no need to reset(), since threshold doesn't affect
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// offset vertices' computation, it only controls how
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// far will we be looking for self-intersections
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}
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unsigned vertex(double * x, double * y)
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{
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if (offset_ == 0.0)
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{
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return geom_.vertex(x, y);
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}
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if (status_ == initial)
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{
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init_vertices();
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}
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if (pos_ >= vertices_.size())
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{
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return SEG_END;
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}
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pre_ = (pos_ ? cur_ : pre_first_);
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cur_ = vertices_.at(pos_++);
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if (pos_ == vertices_.size())
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{
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return output_vertex(x, y);
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}
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double const check_dist = offset_ * threshold_;
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double const check_dist2 = check_dist * check_dist;
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double t = 1.0;
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double vt, ut;
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for (size_t i = pos_; i+1 < vertices_.size(); ++i)
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{
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//break; // uncomment this to see all the curls
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vertex2d const& u0 = vertices_[i];
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vertex2d const& u1 = vertices_[i+1];
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double const dx = u0.x - cur_.x;
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double const dy = u0.y - cur_.y;
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if (dx*dx + dy*dy > check_dist2)
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{
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break;
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}
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if (!intersection(pre_, cur_, &vt, u0, u1, &ut))
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{
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continue;
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}
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if (vt < 0.0 || vt > t || ut < 0.0 || ut > 1.0)
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{
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continue;
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}
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t = vt;
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pos_ = i+1;
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}
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cur_.x = pre_.x + t * (cur_.x - pre_.x);
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cur_.y = pre_.y + t * (cur_.y - pre_.y);
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return output_vertex(x, y);
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}
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void reset()
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{
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geom_.rewind(0);
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vertices_.clear();
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status_ = initial;
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pos_ = 0;
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}
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void rewind(unsigned)
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{
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pos_ = 0;
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}
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private:
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static double explement_reflex_angle(double angle)
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{
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if (angle > M_PI)
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{
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return angle - 2 * M_PI;
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}
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else if (angle < -M_PI)
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{
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return angle + 2 * M_PI;
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}
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else
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{
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return angle;
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}
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}
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static bool intersection(vertex2d const& u1, vertex2d const& u2, double* ut,
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vertex2d const& v1, vertex2d const& v2, double* vt)
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{
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double const dx = v1.x - u1.x;
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double const dy = v1.y - u1.y;
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double const ux = u2.x - u1.x;
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double const uy = u2.y - u1.y;
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double const vx = v2.x - v1.x;
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double const vy = v2.y - v1.y;
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// the first line is not vertical
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if (ux < -1e-6 || ux > 1e-6)
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{
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double const up = ux * dy - dx * uy;
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double const dn = vx * uy - ux * vy;
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if (dn > -1e-6 && dn < 1e-6)
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{
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return false; // they are parallel
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}
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*vt = up / dn;
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*ut = (*vt * vx + dx) / ux;
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return true;
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}
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// the first line is not horizontal
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if (uy < -1e-6 || uy > 1e-6)
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{
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double const up = uy * dx - dy * ux;
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double const dn = vy * ux - uy * vx;
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if (dn > -1e-6 && dn < 1e-6)
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{
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return false; // they are parallel
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}
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*vt = up / dn;
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*ut = (*vt * vy + dy) / uy;
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return true;
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}
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// the first line is too short
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return false;
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}
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/**
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* @brief Translate (vx, vy) by rotated (dx, dy).
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*/
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static void displace(vertex2d & v, double dx, double dy, double a)
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{
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v.x += dx * std::cos(a) - dy * std::sin(a);
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v.y += dx * std::sin(a) + dy * std::cos(a);
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}
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/**
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* @brief Translate (vx, vy) by rotated (0, -offset).
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*/
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void displace(vertex2d & v, double a) const
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{
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v.x += offset_ * std::sin(a);
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v.y -= offset_ * std::cos(a);
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}
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/**
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* @brief (vx, vy) := (ux, uy) + rotated (0, -offset)
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*/
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void displace(vertex2d & v, vertex2d const& u, double a) const
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{
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v.x = u.x + offset_ * std::sin(a);
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v.y = u.y - offset_ * std::cos(a);
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v.cmd = u.cmd;
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}
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void displace2(vertex2d & v, double a, double b) const
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{
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double sa = offset_ * std::sin(a);
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double ca = offset_ * std::cos(a);
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double h = std::tan(0.5 * (b - a));
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v.x = v.x + sa + h * ca;
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v.y = v.y - ca + h * sa;
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}
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status init_vertices()
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{
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if (status_ != initial) // already initialized
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{
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return status_;
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}
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vertex2d v1(vertex2d::no_init);
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vertex2d v2(vertex2d::no_init);
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vertex2d w(vertex2d::no_init);
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v1.cmd = geom_.vertex(&v1.x, &v1.y);
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v2.cmd = geom_.vertex(&v2.x, &v2.y);
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if (v2.cmd == SEG_END) // not enough vertices in source
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{
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return status_ = process;
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}
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double angle_a = 0;
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double angle_b = std::atan2((v2.y - v1.y), (v2.x - v1.x));
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double joint_angle;
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// first vertex
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displace(v1, angle_b);
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push_vertex(v1);
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// Sometimes when the first segment is too short, it causes ugly
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// curls at the beginning of the line. To avoid this, we make up
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// a fake vertex two offset-lengths before the first, and expect
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// intersection detection smoothes it out.
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pre_first_ = v1;
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displace(pre_first_, -2 * std::fabs(offset_), 0, angle_b);
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while ((v1 = v2, v2.cmd = geom_.vertex(&v2.x, &v2.y)) != SEG_END)
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{
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angle_a = angle_b;
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angle_b = std::atan2((v2.y - v1.y), (v2.x - v1.x));
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joint_angle = explement_reflex_angle(angle_b - angle_a);
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double half_turns = half_turn_segments_ * std::fabs(joint_angle);
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int bulge_steps = 0;
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if (offset_ < 0.0)
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{
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if (joint_angle > 0.0)
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{
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joint_angle = joint_angle - 2 * M_PI;
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}
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else
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{
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bulge_steps = 1 + static_cast<int>(std::floor(half_turns / M_PI));
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}
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}
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else
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{
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if (joint_angle < 0.0)
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{
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joint_angle = joint_angle + 2 * M_PI;
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}
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else
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{
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bulge_steps = 1 + static_cast<int>(std::floor(half_turns / M_PI));
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}
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}
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#ifdef MAPNIK_LOG
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if (bulge_steps == 0)
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{
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// inside turn (sharp/obtuse angle)
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MAPNIK_LOG_DEBUG(ctrans) << "offset_converter:"
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<< " Sharp joint [<< inside turn " << int(joint_angle*180/M_PI)
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<< " degrees >>]";
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}
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else
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{
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// outside turn (reflex angle)
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MAPNIK_LOG_DEBUG(ctrans) << "offset_converter:"
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<< " Bulge joint >)) outside turn " << int(joint_angle*180/M_PI)
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<< " degrees ((< with " << bulge_steps << " segments";
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}
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#endif
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displace(w, v1, angle_a);
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push_vertex(w);
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for (int s = 0; ++s < bulge_steps;)
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{
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displace(w, v1, angle_a + (joint_angle * s) / bulge_steps);
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push_vertex(w);
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}
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displace(v1, angle_b);
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push_vertex(v1);
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}
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// last vertex
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displace(v1, angle_b);
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push_vertex(v1);
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// initialization finished
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return status_ = process;
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}
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unsigned output_vertex(double* px, double* py)
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{
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*px = cur_.x;
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*py = cur_.y;
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return cur_.cmd;
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}
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unsigned output_vertex(double* px, double* py, status st)
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{
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status_ = st;
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return output_vertex(px, py);
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}
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void push_vertex(vertex2d const& v)
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{
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vertices_.push_back(v);
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}
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Geometry & geom_;
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double offset_;
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double threshold_;
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unsigned half_turn_segments_;
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status status_;
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size_t pos_;
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std::vector<vertex2d> vertices_;
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vertex2d pre_first_;
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vertex2d pre_;
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vertex2d cur_;
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};
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}
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#endif // MAPNIK_OFFSET_CONVERTER_HPP
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