...one of the most highly
regarded and expertly designed C++ library projects in the
world.

— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards

Calculates the minimal set of a geometry.

The free function unique calculates the minimal set (where duplicate consecutive points are removed) of a geometry.

template<typename Geometry> void unique(Geometry & geometry)

Type |
Concept |
Name |
Description |
---|---|---|---|

Geometry & |
Any type fulfilling a Geometry Concept |
geometry |
A model of the specified concept which will be made unique |

Either

`#include <boost/geometry.hpp>`

Or

`#include <boost/geometry/algorithms/unique.hpp>`

The function unique is not defined by OGC.

The function unique conforms to the std::unique function of the C++ std-library.

Case |
Behavior |
---|---|

Point |
Nothing happens, geometry is unchanged |

Segment |
Nothing happens, geometry is unchanged |

Box |
Nothing happens, geometry is unchanged |

Linestring |
Removes all consecutive duplicate points |

Ring |
Removes all consecutive duplicate points |

Polygon |
Removes all consecutive duplicate points in all rings |

Multi Point |
Nothing happens, geometry is unchanged. Even if two equal points happen to be stored consecutively, they are kept |

Multi Linestring |
Removes all consecutive duplicate points in all contained linestrings |

Multi Polygon |
Removes all consecutive duplicate points in all contained polygons (all rings) |

Linear

Shows how to make a so-called minimal set of a polygon by removing duplicate points

#include <iostream> #include <boost/geometry.hpp> #include <boost/geometry/geometries/polygon.hpp> #include <boost/geometry/geometries/adapted/boost_tuple.hpp> BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian) int main() { boost::geometry::model::polygon<boost::tuple<double, double> > poly; boost::geometry::read_wkt("POLYGON((0 0,0 0,0 5,5 5,5 5,5 5,5 0,5 0,0 0,0 0,0 0,0 0))", poly); boost::geometry::unique(poly); std::cout << boost::geometry::wkt(poly) << std::endl; return 0; }

Output:

POLYGON((0 0,0 5,5 5,5 0,0 0))