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/*
* Collapsor.h
*
* Created on: Sep 25, 2014
* Author: dsalinas
*/
#ifndef COLLAPSOR_H_
#define COLLAPSOR_H_
#include <list>
#include "utils/Edge_contractor.h"
/**
* Iteratively puts every vertex at the center of its neighbors
*/
template<typename SkBlComplex> class Edge_collapsor{
private:
SkBlComplex& complex_;
unsigned num_collapses_;
public:
typedef typename SkBlComplex::Vertex_handle Vertex_handle;
typedef typename SkBlComplex::Edge_handle Edge_handle;
/**
* @brief Modify complex to be the expansion of the k-nearest neighbor
* symetric graph.
*/
Edge_collapsor(SkBlComplex& complex,unsigned num_collapses):
complex_(complex),num_collapses_(num_collapses)
{
std::list<Edge_handle> edges;
edges.insert(edges.begin(),complex_.edge_range().begin(),complex_.edge_range().end());
edges.sort(
[&](Edge_handle e1,Edge_handle e2){
return squared_edge_length(e1) < squared_edge_length(e2);
});
collapse_edges(edges);
}
private:
void collapse_edges(std::list<Edge_handle>& edges){
while(!edges.empty() && num_collapses_--){
Edge_handle current_edge = edges.front();
edges.pop_front();
if(is_link_reducible(current_edge))
complex_.remove_edge(current_edge);
}
}
bool is_link_reducible(Edge_handle e){
auto link = complex_.link(e);
if(link.empty()) return false;
if(link.is_cone()) return true;
if(link.num_connected_components()>1) return false;
Edge_contractor<Complex> contractor(link,link.num_vertices()-1);
return (link.num_vertices()==1);
}
double squared_edge_length(Edge_handle e) const{
return squared_eucl_distance(complex_.point(complex_.first_vertex(e)),complex_.point(complex_.second_vertex(e)));
}
double squared_eucl_distance(const Point& p1,const Point& p2) const{
return Geometry_trait::Squared_distance_d()(p1,p2);
}
};
#endif /* COLLAPSOR_H_ */
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