CGAL 6.0.2 - Shape Detection

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Shape_detection/region_growing_with_custom_classes.cpp
// STL includes.
#include <unordered_map>
#include <list>
#include <vector>
#include <string>
#include <iostream>
#include <iterator>
#include <cassert>
// CGAL includes.
#include "include/utils.h"
#include <CGAL/Simple_cartesian.h>
#include <CGAL/Shape_detection/Region_growing/Region_growing.h>
// Custom Neighbor_query and Region_type classes for region growing.
namespace Custom {
// An object that stores indices of all its neighbors.
struct Object {
std::vector<std::vector<Object>::const_iterator> neighbors;
bool operator==(const Object& obj) const {
return neighbors == obj.neighbors;
}
};
// A range of objects.
using Objects = std::vector<Object>; // std::list<Object> works as well
// The Neighbor_query functor that accesses neighbors stored in
// the object struct above.
class Neighbor_query {
const Objects& m_objects;
using Item = typename Objects::const_iterator;
using Region = std::vector<Item>;
public:
Neighbor_query(const Objects& objects) :
m_objects(objects)
{ }
void operator()(
const Item &query,
std::vector<Item>& neighbors) const {
for (auto it = m_objects.begin(); it != m_objects.end(); it++) {
if (it == query) {
neighbors = query->neighbors;
return;
}
}
}
};
// The Region_type class, where the function is_part_of_region() verifies
// a very specific condition that the first and second objects in the
// range are in fact neighbors; is_valid_region() function always
// returns true after the first call to the update() function.
// These are the only functions that have to be defined.
class Region_type {
bool m_is_valid = false;
const std::vector<Object>& m_input;
public:
Region_type(const std::vector<Object> &input) : m_input(input) { }
using Primitive = std::size_t;
using Item = std::vector<Object>::const_iterator;
using Region = std::vector<Item>;
struct hash_item {
std::size_t operator()(Item i) const {
using boost::hash_value;
return boost::hash_value(i.operator->());
}
};
using Region_unordered_map = std::unordered_map<Item, std::size_t, hash_item >;
using Region_index_map = boost::associative_property_map<Region_unordered_map>;
Region_index_map region_index_map() {
Region_index_map index_map(m_region_map);
return index_map;
}
bool is_part_of_region(
const Item query,
const Region& region) const {
if (region.size() == 0) return false;
auto it = m_input.begin();
if (query == it || query == (it + 1))
return true;
return false;
}
inline bool is_valid_region(const Region&) const {
return m_is_valid;
}
Primitive primitive() {
return Primitive();
}
bool update(const Region&) {
m_is_valid = true;
return m_is_valid;
}
private:
Region_unordered_map m_region_map;
};
} // namespace Custom
// Typedefs.
using Object = Custom::Object;
using Objects = Custom::Objects;
using Neighbor_query = Custom::Neighbor_query;
using Region_type = Custom::Region_type;
using Region_growing = CGAL::Shape_detection::Region_growing<Neighbor_query, Region_type>;
int main() {
// Define a range of objects, where the first two objects form
// the first region, while the third object forms the second region.
// Note that Objects is a random access container here, however the
// same algorithm/example can work with other containers, e.g. std::list.
Objects objects(3);
auto it = objects.begin();
// Region 1.
objects[0].neighbors.push_back(it+1);
objects[1].neighbors.push_back(it);
// The single third object constitutes the second region.
std::cout << "* number of input objects: " << objects.size() << std::endl;
assert(objects.size() == 3);
// Create instances of the classes Neighbor_query and Region_type.
Neighbor_query neighbor_query = Neighbor_query(objects);
Region_type region_type = Region_type(objects);
// Create an instance of the region growing class.
Region_growing region_growing(
objects, neighbor_query, region_type);
// Run the algorithm.
std::vector<typename Region_growing::Primitive_and_region> regions;
region_growing.detect(std::back_inserter(regions));
std::cout << "* number of found regions: " << regions.size() << std::endl;
assert(regions.size() == 2);
return EXIT_SUCCESS;
}
CGAL::Shape_detection::Region_growing
Main class/entry point for running the region growing algorithm.
Definition: Region_growing.h:72
boost::hash_value
std::size_t hash_value(const typename CGAL::internal::Point_set_3_index< Point, Vector > &i)