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/* This file is part of the Gudhi Library. The Gudhi library
* (Geometric Understanding in Higher Dimensions) is a generic C++
* library for computational topology.
*
* Author(s): David Salinas
*
* Copyright (C) 2014 Inria
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef UTILS_EDGE_COLLAPSOR_H_
#define UTILS_EDGE_COLLAPSOR_H_
#include <list>
#include "utils/Edge_contractor.h"
#include "utils/UI_utils.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 Collapse num_collapses edges. If num_collapses<0 then it collapses all possible edges.
* Largest edges are collapsed first.
*
*/
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<SkBlComplex> 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 // UTILS_EDGE_COLLAPSOR_H_
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