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+/* This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
+ * See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
+ * Author(s): David Salinas
+ *
+ * Copyright (C) 2014 Inria
+ *
+ * Modification(s):
+ * - YYYY/MM Author: Description of the modification
+ */
+
+#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_