/usr/include/mapnik/simplify_converter.hpp is in libmapnik-dev 2.2.0+ds1-7+b2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#define MAPNIK_SIMPLIFY_CONVERTER_HPP
// mapnik
#include <mapnik/config.hpp>
#include <mapnik/box2d.hpp>
#include <mapnik/vertex.hpp>
#include <mapnik/simplify.hpp>
#include <mapnik/noncopyable.hpp>
// stl
#include <limits>
#include <set>
#include <vector>
#include <deque>
#include <cmath>
#include <stdexcept>
// boost
#include <boost/optional.hpp>
namespace mapnik
{
struct weighted_vertex : private mapnik::noncopyable
{
vertex2d coord;
double weight;
weighted_vertex *prev;
weighted_vertex *next;
weighted_vertex(vertex2d coord_) :
coord(coord_),
weight(std::numeric_limits<double>::infinity()),
prev(NULL),
next(NULL) {}
double nominalWeight()
{
if (prev == NULL || next == NULL || coord.cmd != SEG_LINETO) {
return std::numeric_limits<double>::infinity();
}
vertex2d const& A = prev->coord;
vertex2d const& B = next->coord;
vertex2d const& C = coord;
return std::abs((double)((A.x - C.x) * (B.y - A.y) - (A.x - B.x) * (C.y - A.y))) / 2.0;
}
struct ascending_sort
{
bool operator() (const weighted_vertex *a, const weighted_vertex *b)
{
return b->weight > a->weight;
}
};
};
struct sleeve
{
vertex2d v[5];
sleeve(vertex2d const& v0, vertex2d const& v1, double offset)
{
double a = std::atan2((v1.y - v0.y), (v1.x - v0.x));
double dx = offset * std::cos(a);
double dy = offset * std::sin(a);
v[0].x = v0.x + dy;
v[0].y = v0.y - dx;
v[1].x = v0.x - dy;
v[1].y = v0.y + dx;
v[2].x = v1.x - dy;
v[2].y = v1.y + dx;
v[3].x = v1.x + dy;
v[3].y = v1.y - dx;
v[4].x = v0.x + dy;
v[4].y = v0.y - dx;
}
bool inside(vertex2d const& q)
{
bool inside=false;
for (unsigned i=0;i<4;++i)
{
if ((((v[i+1].y <= q.y) && (q.y < v[i].y)) ||
((v[i].y <= q.y) && (q.y < v[i+1].y))) &&
(q.x < (v[i].x - v[i+1].x) * (q.y - v[i+1].y)/ (v[i].y - v[i+1].y) + v[i+1].x))
inside=!inside;
}
return inside;
}
void print()
{
std::cerr << "LINESTRING("
<< v[0].x << " " << -v[0].y << ","
<< v[1].x << " " << -v[1].y << ","
<< v[2].x << " " << -v[2].y << ","
<< v[3].x << " " << -v[3].y << ","
<< v[0].x << " " << -v[0].y << ")" << std::endl;
}
};
template <typename Geometry>
struct MAPNIK_DECL simplify_converter
{
public:
simplify_converter(Geometry& geom)
: geom_(geom),
tolerance_(0.0),
status_(initial),
algorithm_(radial_distance),
pos_(0)
{}
enum status
{
initial,
process,
closing,
end,
cache
};
simplify_algorithm_e get_simplify_algorithm()
{
return algorithm_;
}
void set_simplify_algorithm(simplify_algorithm_e value)
{
if (algorithm_ != value)
{
algorithm_ = value;
reset();
}
}
double get_simplify_tolerance()
{
return tolerance_;
}
void set_simplify_tolerance(double value)
{
if (tolerance_ != value) {
tolerance_ = value;
reset();
}
}
void reset()
{
geom_.rewind(0);
vertices_.clear();
status_ = initial;
pos_ = 0;
}
void rewind(unsigned int) const
{
pos_ = 0;
}
unsigned vertex(double* x, double* y)
{
if (tolerance_ == 0.0)
return geom_.vertex(x, y);
if (status_ == initial)
init_vertices();
return output_vertex(x, y);
}
private:
unsigned output_vertex(double* x, double* y)
{
switch (algorithm_)
{
case visvalingam_whyatt:
return output_vertex_cached(x, y);
case radial_distance:
return output_vertex_distance(x, y);
case zhao_saalfeld:
return output_vertex_sleeve(x, y);
default:
throw std::runtime_error("simplification algorithm not yet implemented");
}
return SEG_END;
}
unsigned output_vertex_cached(double* x, double* y) {
if (pos_ >= vertices_.size())
return SEG_END;
previous_vertex_ = vertices_[pos_];
*x = previous_vertex_.x;
*y = previous_vertex_.y;
pos_++;
return previous_vertex_.cmd;
}
unsigned output_vertex_distance(double* x, double* y) {
if (status_ == closing) {
status_ = end;
return SEG_CLOSE;
}
vertex2d last(vertex2d::no_init);
vertex2d vtx(vertex2d::no_init);
while ((vtx.cmd = geom_.vertex(&vtx.x, &vtx.y)) != SEG_END)
{
if (vtx.cmd == SEG_LINETO) {
if (distance_to_previous(vtx) > tolerance_) {
// Only output a vertex if it's far enough away from the previous
break;
} else {
last = vtx;
// continue
}
} else if (vtx.cmd == SEG_CLOSE) {
if (last.cmd == vertex2d::no_init) {
// The previous vertex was already output in the previous call.
// We can now safely output SEG_CLOSE.
status_ = end;
} else {
// We eliminated the previous point because it was too close, but
// we have to output it now anyway, since this is the end of the
// vertex stream. Make sure that we output SEG_CLOSE in the next call.
vtx = last;
status_ = closing;
}
break;
} else if (vtx.cmd == SEG_MOVETO) {
break;
} else {
throw std::runtime_error("Unknown vertex command");
}
}
previous_vertex_ = vtx;
*x = vtx.x;
*y = vtx.y;
return vtx.cmd;
}
template <typename Iterator>
bool fit_sleeve(Iterator itr,Iterator end, vertex2d const& v)
{
sleeve s(*itr,v,tolerance_);
++itr; // skip first vertex
for (; itr!=end; ++itr)
{
if (!s.inside(*itr))
{
return false;
}
}
return true;
}
unsigned output_vertex_sleeve(double* x, double* y)
{
vertex2d vtx(vertex2d::no_init);
std::size_t min_size = 1;
while ((vtx.cmd = geom_.vertex(&vtx.x, &vtx.y)) != SEG_END)
{
//if ((std::fabs(vtx.x - previous_vertex_.x) < 0.5) &&
// (std::fabs(vtx.y - previous_vertex_.y) < 0.5))
// continue;
if (status_ == cache &&
vertices_.size() >= min_size)
status_ = process;
previous_vertex_ = vtx;
if (vtx.cmd == SEG_MOVETO)
{
if (sleeve_cont_.size() > 1)
{
vertices_.push_back(sleeve_cont_.back());
sleeve_cont_.clear();
}
vertices_.push_back(vtx);
sleeve_cont_.push_back(vtx);
if (status_ == process) break;
}
else if (vtx.cmd == SEG_LINETO)
{
if (sleeve_cont_.size() > 1 && !fit_sleeve(sleeve_cont_.begin(), sleeve_cont_.end(), vtx))
{
vertex2d last = vtx;
vtx = sleeve_cont_.back();
sleeve_cont_.clear();
sleeve_cont_.push_back(vtx);
sleeve_cont_.push_back(last);
vertices_.push_back(vtx);
if (status_ == process) break;
}
else
{
sleeve_cont_.push_back(vtx);
}
}
else if (vtx.cmd == SEG_CLOSE)
{
if (sleeve_cont_.size() > 1)
{
vertices_.push_back(sleeve_cont_.back());
sleeve_cont_.clear();
}
vertices_.push_back(vtx);
if (status_ == process) break;
}
}
if (status_ == cache)
{
if (vertices_.size() < min_size)
return SEG_END;
status_ = process;
}
if (vtx.cmd == SEG_END)
{
if (sleeve_cont_.size() > 1)
{
vertices_.push_back(sleeve_cont_.back());
}
sleeve_cont_.clear();
vertices_.push_back(vtx);
}
if (vertices_.size() > 0)
{
vertex2d v = vertices_.front();
vertices_.pop_front();
*x = v.x;
*y = v.y;
return v.cmd;
}
return SEG_END;
}
double distance_to_previous(vertex2d const& vtx) {
double dx = previous_vertex_.x - vtx.x;
double dy = previous_vertex_.y - vtx.y;
return dx * dx + dy * dy;
}
status init_vertices()
{
if (status_ != initial) // already initialized
return status_;
reset();
switch (algorithm_) {
case visvalingam_whyatt:
return init_vertices_visvalingam_whyatt();
case radial_distance:
// Use
vertices_.push_back(vertex2d(vertex2d::no_init));
return status_ = process;
case zhao_saalfeld:
return status_ = cache;
default:
throw std::runtime_error("simplification algorithm not yet implemented");
}
}
status init_vertices_visvalingam_whyatt()
{
typedef std::set<weighted_vertex *, weighted_vertex::ascending_sort> VertexSet;
typedef std::vector<weighted_vertex *> VertexList;
std::vector<weighted_vertex *> v_list;
vertex2d vtx(vertex2d::no_init);
while ((vtx.cmd = geom_.vertex(&vtx.x, &vtx.y)) != SEG_END)
{
v_list.push_back(new weighted_vertex(vtx));
}
if (v_list.empty()) {
return status_ = process;
}
// Connect the vertices in a linked list and insert them into the set.
VertexSet v;
for (VertexList::iterator i = v_list.begin(); i != v_list.end(); ++i)
{
(*i)->prev = i == v_list.begin() ? NULL : *(i - 1);
(*i)->next = i + 1 == v_list.end() ? NULL : *(i + 1);
(*i)->weight = (*i)->nominalWeight();
v.insert(*i);
}
// Use Visvalingam-Whyatt algorithm to calculate each point's weight.
while (v.size() > 0)
{
VertexSet::iterator lowest = v.begin();
weighted_vertex *removed = *lowest;
if (removed->weight >= tolerance_) {
break;
}
v.erase(lowest);
// Connect adjacent vertices with each other
if (removed->prev) removed->prev->next = removed->next;
if (removed->next) removed->next->prev = removed->prev;
// Adjust weight and reinsert prev/next to move them to their correct position.
if (removed->prev) {
v.erase(removed->prev);
removed->prev->weight = std::max(removed->weight, removed->prev->nominalWeight());
v.insert(removed->prev);
}
if (removed->next) {
v.erase(removed->next);
removed->next->weight = std::max(removed->weight, removed->next->nominalWeight());
v.insert(removed->next);
}
}
v.clear();
// Traverse the remaining list and insert them into the vertex cache.
for (VertexList::iterator i = v_list.begin(); i != v_list.end(); ++i)
{
if ((*i)->weight >= tolerance_)
{
vertices_.push_back((*i)->coord);
}
delete *i;
}
// Initialization finished.
return status_ = process;
}
Geometry& geom_;
double tolerance_;
status status_;
simplify_algorithm_e algorithm_;
std::deque<vertex2d> vertices_;
std::deque<vertex2d> sleeve_cont_;
vertex2d previous_vertex_;
mutable size_t pos_;
};
}
#endif // MAPNIK_SIMPLIFY_CONVERTER_HPP
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