...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Checks if a geometry is valid (in the OGC sense)
template<typename Geometry> bool is_valid(Geometry const & geometry, std::string & message)
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 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
Either
#include <boost/geometry.hpp>
Or
#include <boost/geometry/algorithms/is_valid.hpp>
The function is_valid is not defined by OGC.
Geometry |
Status |
---|---|
Point |
|
Segment |
|
Box |
|
Linestring |
|
Ring |
|
Polygon |
|
MultiPoint |
|
MultiLinestring |
|
MultiPolygon |
|
Variant |
|
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
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