lwgeom_voronoi_diagram()

LWGEOM* lwgeom_voronoi_diagram	(	const LWGEOM *	g,
		const GBOX *	env,
		double	tolerance,
		int	output_edges
	)

Take vertices of a geometry and build the Voronoi diagram.

Parameters

g	the input geometry
env	an optional envelope for clipping the results
tolerance	an optional snapping tolerance for improved robustness
output_edges	if non-zero the result will be a MULTILINESTRING, otherwise it'll be a COLLECTION of polygons.

Requires GEOS-3.5.0 or higher

Definition at line 2101 of file liblwgeom/lwgeom_geos.c.

References COLLECTIONTYPE, GBOX2GEOS(), GEOS2LWGEOM(), LW_FALSE, lwcollection_as_lwgeom(), lwcollection_construct_empty(), lwerror(), lwgeom_count_vertices(), lwgeom_geos_errmsg, lwgeom_geos_error(), lwgeom_get_geos_coordseq_2d(), lwgeom_get_srid(), lwgeom_set_srid(), and lwnotice().

Referenced by assert_empty_diagram(), ST_Voronoi(), test_lwgeom_voronoi_diagram(), and test_lwgeom_voronoi_diagram_custom_envelope().

                                                                                                     {
#if POSTGIS_GEOS_VERSION < 35
        lwerror("lwgeom_voronoi_diagram: GEOS 3.5 or higher required");
        return NULL;
#else
        uint32_t num_points = lwgeom_count_vertices(g);
        LWGEOM *lwgeom_result;
        char is_3d = LW_FALSE;
        int srid = lwgeom_get_srid(g);
        GEOSCoordSequence* coords;
        GEOSGeometry* geos_geom;
        GEOSGeometry* geos_env = NULL;
        GEOSGeometry* geos_result;

        if (num_points < 2)
        {
                LWCOLLECTION* empty = lwcollection_construct_empty(COLLECTIONTYPE, lwgeom_get_srid(g), 0, 0);
                return lwcollection_as_lwgeom(empty);
        }

        initGEOS(lwnotice, lwgeom_geos_error);

        /* Instead of using the standard LWGEOM2GEOS transformer, we read the vertices of the
         * LWGEOM directly and put them into a single GEOS CoordinateSeq that can be used to
         * define a LineString.  This allows us to process geometry types that may not be
         * supported by GEOS, and reduces the memory requirements in cases of many geometries
         * with few points (such as LWMPOINT).
         */
        coords = lwgeom_get_geos_coordseq_2d(g, num_points);
        if (!coords)
                return NULL;

        geos_geom = GEOSGeom_createLineString(coords);
        if (!geos_geom)
        {
                GEOSCoordSeq_destroy(coords);
                return NULL;
        }

        if (env)
                geos_env = GBOX2GEOS(env);

        geos_result = GEOSVoronoiDiagram(geos_geom, geos_env, tolerance, output_edges);

        GEOSGeom_destroy(geos_geom);
        if (env)
                GEOSGeom_destroy(geos_env);

        if (!geos_result)
        {
                lwerror("GEOSVoronoiDiagram: %s", lwgeom_geos_errmsg);
                return NULL;
        }

        lwgeom_result = GEOS2LWGEOM(geos_result, is_3d);
        GEOSGeom_destroy(geos_result);

        lwgeom_set_srid(lwgeom_result, srid);

        return lwgeom_result;
#endif /* POSTGIS_GEOS_VERSION < 35 */
}

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