use a set to make visvalingam a lot faster

bindings/python/mapnik_line_symbolizer.cpp

@@ -63,10 +63,6 @@ void export_line_symbolizer()
                       &line_symbolizer::smooth,
                       &line_symbolizer::set_smooth,
                       "smooth value (0..1.0)")
-        .add_property("simplify_algorithm",
-                      &line_symbolizer::simplify_algorithm,
-                      &line_symbolizer::set_simplify_algorithm,
-                      "simplfication algorithm")
         .add_property("simplify_tolerance",
                       &line_symbolizer::simplify_tolerance,
                       &line_symbolizer::set_simplify_tolerance,

bindings/python/mapnik_polygon_symbolizer.cpp

@@ -88,10 +88,6 @@ void export_polygon_symbolizer()
                       &polygon_symbolizer::smooth,
                       &polygon_symbolizer::set_smooth,
                       "smooth value (0..1.0)")
-        .add_property("simplify_algorithm",
-                      &polygon_symbolizer::simplify_algorithm,
-                      &polygon_symbolizer::set_simplify_algorithm,
-                      "simplfication algorithm")
         .add_property("simplify_tolerance",
                       &polygon_symbolizer::simplify_tolerance,
                       &polygon_symbolizer::set_simplify_tolerance,

include/mapnik/simplify_converter.hpp

@@ -8,6 +8,7 @@
 
 // STL
 #include <limits>
+#include <set>
 
 // Boost
 #include <boost/optional.hpp>
@@ -37,9 +38,9 @@ struct weighted_vertex : private boost::noncopyable {
         return std::abs((double)((A.x - C.x) * (B.y - A.y) - (A.x - B.x) * (C.y - A.y))) / 2.0;
     }
 
-    struct descending_sort {
+    struct ascending_sort {
         bool operator() (const weighted_vertex *a, const weighted_vertex *b) {
-            return a->weight > b->weight;
+            return b->weight > a->weight;
         }
     };
 };
@@ -60,6 +61,7 @@ public:
     {
         initial,
         process,
+        closing,
         end
     };
 
@@ -120,6 +122,8 @@ private:
         switch (algorithm_) {
             case visvalingam_whyatt:
                 return output_vertex_cached(x, y);
+            case radial_distance:
+                return output_vertex_distance(x, y);
             default:
                 throw std::runtime_error("simplification algorithm not yet implemented");
         }
@@ -131,13 +135,63 @@ private:
         if (pos_ >= vertices_.size())
             return SEG_END;
 
-        vertex2d const& vtx = vertices_[pos_];
+        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;
-        pos_++;
         return vtx.cmd;
     }
 
+    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
@@ -148,70 +202,76 @@ private:
         switch (algorithm_) {
             case visvalingam_whyatt:
                 return init_vertices_visvalingam_whyatt();
+            case radial_distance:
+                // Use
+                vertices_.push_back(vertex2d(vertex2d::no_init));
+                return status_ = process;
             default:
                 throw std::runtime_error("simplification algorithm not yet implemented");
         }
     }
 
     status init_vertices_visvalingam_whyatt() {
-        typedef std::vector<weighted_vertex *> WeightedVertices;
+        typedef std::set<weighted_vertex *, weighted_vertex::ascending_sort> VertexSet;
+        typedef std::vector<weighted_vertex *> VertexList;
 
-        WeightedVertices v;
+        std::vector<weighted_vertex *> v_list;
         vertex2d vtx(vertex2d::no_init);
         while ((vtx.cmd = geom_.vertex(&vtx.x, &vtx.y)) != SEG_END)
         {
-            v.push_back(new weighted_vertex(vtx));
+            v_list.push_back(new weighted_vertex(vtx));
         }
 
-        if (!v.size()) {
+        if (!v_list.size()) {
             return status_ = process;
         }
 
-        // Connect the vertices in a linked list.
+        // Connect the vertices in a linked list and insert them into the set.
-        for (WeightedVertices::iterator end = v.end(), begin = v.begin(), i = v.begin(); i != end; i++)
+        VertexSet v;
+        for (VertexList::iterator i = v_list.begin(); i != v_list.end(); i++)
         {
-            (*i)->prev = i == begin ? NULL : *(i - 1);
+            (*i)->prev = i == v_list.begin() ? NULL : *(i - 1);
-            (*i)->next = i + 1 == end ? NULL : *(i + 1);
+            (*i)->next = i + 1 == v_list.end() ? NULL : *(i + 1);
             (*i)->weight = (*i)->nominalWeight();
+            v.insert(*i);
         }
 
-        weighted_vertex *front = v.front();
-
-        typename weighted_vertex::descending_sort descending;
-
-        std::sort(v.begin(), v.end(), descending);
         // Use Visvalingam-Whyatt algorithm to calculate each point's weight.
-        while (v.size() > 0 && v.back()->weight < tolerance_)
+        while (v.size() > 0)
         {
-            weighted_vertex *removed = v.back();
+            VertexSet::iterator lowest = v.begin();
-            v.pop_back();
+            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;
-            if (removed->prev) removed->prev->weight = std::max(removed->weight, removed->prev->nominalWeight());
+            // Adjust weight and reinsert prev/next to move them to their correct position.
-            if (removed->next) removed->next->weight = std::max(removed->weight, removed->next->nominalWeight());
+            if (removed->prev) {
-
+                v.erase(removed->prev);
-            if (front == removed) {
+                removed->prev->weight = std::max(removed->weight, removed->prev->nominalWeight());
-                front = removed->next;
+                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);
             }
-
-            delete removed;
-
-            // TODO: find a way so that we can efficiently resort the vector.
-            // We only changed remove->prev and removed->next, so we should only
-            // have to deal with them. E.g. use binary search to find prev/next
-            // using the old value, determine new position using binary search
-            // and if different, move it.
-            std::sort(v.begin(), v.end(), descending);
         }
 
+        v.clear();
+
         // Traverse the remaining list and insert them into the vertex cache.
-        for (weighted_vertex *vtx = front; vtx;) {
+        for (VertexList::iterator i = v_list.begin(); i != v_list.end(); i++)
-            vertices_.push_back(vtx->coord);
+        {
-            weighted_vertex *removed = vtx;
+            if ((*i)->weight >= tolerance_) {
-            vtx = vtx->next;
+                vertices_.push_back((*i)->coord);
-            delete removed;
+            }
+            delete *i;
         }
 
         // Initialization finished.
@@ -224,7 +284,7 @@ private:
     simplify_algorithm_e            algorithm_;
     size_t                          pos_;
     std::vector<vertex2d>           vertices_;
-
+    vertex2d                        previous_vertex_;
 };
 
 }

include/mapnik/vertex_converters.hpp

@@ -107,6 +107,7 @@ struct converter_traits<T,mapnik::simplify_tag>
     template <typename Args>
     static void setup(geometry_type & geom, Args const& args)
     {
+        geom.set_simplify_algorithm(boost::fusion::at_c<2>(args).simplify_algorithm());
         geom.set_simplify_tolerance(boost::fusion::at_c<2>(args).simplify_tolerance());
     }
 };

src/load_map.cpp

@@ -883,7 +883,7 @@ void map_parser::parse_symbolizer_base(symbolizer_base &sym, xml_node const &pt)
     if (clip) sym.set_clip(*clip);
 
     // simplify algorithm
-    optional<std::string> simplify_algorithm_name = pt.get_opt_attr<std::string>("simlify-op");
+    optional<std::string> simplify_algorithm_name = pt.get_opt_attr<std::string>("simplify-algorithm");
     if (simplify_algorithm_name)
     {
         optional<simplify_algorithm_e> simplify_algorithm = simplify_algorithm_from_string(*simplify_algorithm_name);