Boost C++ Libraries

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

Synopsis

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

Parameters

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

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

See also