Boost C++ Libraries

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is_valid (with message)

Checks if a geometry is valid (in the OGC sense)

Synopsis

template<typename Geometry>
bool is_valid(Geometry const & geometry, std::string & message)

Parameters

Type

Concept

Name

Description

Geometry const &

Any type fulfilling a Geometry Concept

geometry

A model of the specified concept

std::string &

message

A string containing a message stating if the geometry is valid or not, and if not valid a reason why

Returns

Returns true if the geometry is valid (in the OGC sense); furthermore, the following geometries are considered valid: multi-geometries with no elements, linear geometries containing spikes, areal geometries with duplicate (consecutive) points

Header

Either

#include <boost/geometry.hpp>

Or

#include <boost/geometry/algorithms/is_valid.hpp>

Conformance

The function is_valid is not defined by OGC.

Supported geometries

Geometry

Status

Point

ok

Segment

ok

Box

ok

Linestring

ok

Ring

ok

Polygon

ok

MultiPoint

ok

MultiLinestring

ok

MultiPolygon

ok

Variant

ok

Complexity

Constant-time for points, segments, boxes and multi-points

Linear for linestrings and multi-linestrings

Linearithmic for rings

Currently, worst-case quadratic for polygons and multi-polygons

Example

Checks whether a geometry is valid and, if not valid, prints a message describing the reason

#include <iostream>
#include <string>

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/geometries/polygon.hpp>


int main()
{
    typedef boost::geometry::model::d2::point_xy<double> point_type;
    typedef boost::geometry::model::polygon<point_type> polygon_type;

    polygon_type poly;
    boost::geometry::read_wkt("POLYGON((0 0,0 10,10 10,10 0,0 0),(0 0,9 1,9 2,0 0),(0 0,2 9,1 9,0 0),(2 9,9 2,9 9,2 9))", poly);

    std::string message;
    bool valid = boost::geometry::is_valid(poly, message);
    std::cout << "is valid? " << (valid ? "yes" : "no") << std::endl;
    if (! valid)
    {
        std::cout << "why not valid? " << message << std::endl;
    }

    return 0;
}

Output:

is valid? no
why not valid? Geometry has disconnected interior

is_valid_example

See also

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