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.

Definition at line 1872 of file liblwgeom/lwgeom_geos.c.

{
        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;
}

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 ST_Voronoi(), test_lwgeom_voronoi_diagram(), and test_lwgeom_voronoi_diagram_custom_envelope().

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