PostGIS  2.4.9dev-r@@SVN_REVISION@@

◆ 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
gthe input geometry
envan optional envelope for clipping the results
tolerancean optional snapping tolerance for improved robustness
output_edgesif 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().

2101  {
2102 #if POSTGIS_GEOS_VERSION < 35
2103  lwerror("lwgeom_voronoi_diagram: GEOS 3.5 or higher required");
2104  return NULL;
2105 #else
2106  uint32_t num_points = lwgeom_count_vertices(g);
2107  LWGEOM *lwgeom_result;
2108  char is_3d = LW_FALSE;
2109  int srid = lwgeom_get_srid(g);
2110  GEOSCoordSequence* coords;
2111  GEOSGeometry* geos_geom;
2112  GEOSGeometry* geos_env = NULL;
2113  GEOSGeometry* geos_result;
2114 
2115  if (num_points < 2)
2116  {
2118  return lwcollection_as_lwgeom(empty);
2119  }
2120 
2121  initGEOS(lwnotice, lwgeom_geos_error);
2122 
2123  /* Instead of using the standard LWGEOM2GEOS transformer, we read the vertices of the
2124  * LWGEOM directly and put them into a single GEOS CoordinateSeq that can be used to
2125  * define a LineString. This allows us to process geometry types that may not be
2126  * supported by GEOS, and reduces the memory requirements in cases of many geometries
2127  * with few points (such as LWMPOINT).
2128  */
2129  coords = lwgeom_get_geos_coordseq_2d(g, num_points);
2130  if (!coords)
2131  return NULL;
2132 
2133  geos_geom = GEOSGeom_createLineString(coords);
2134  if (!geos_geom)
2135  {
2136  GEOSCoordSeq_destroy(coords);
2137  return NULL;
2138  }
2139 
2140  if (env)
2141  geos_env = GBOX2GEOS(env);
2142 
2143  geos_result = GEOSVoronoiDiagram(geos_geom, geos_env, tolerance, output_edges);
2144 
2145  GEOSGeom_destroy(geos_geom);
2146  if (env)
2147  GEOSGeom_destroy(geos_env);
2148 
2149  if (!geos_result)
2150  {
2151  lwerror("GEOSVoronoiDiagram: %s", lwgeom_geos_errmsg);
2152  return NULL;
2153  }
2154 
2155  lwgeom_result = GEOS2LWGEOM(geos_result, is_3d);
2156  GEOSGeom_destroy(geos_result);
2157 
2158  lwgeom_set_srid(lwgeom_result, srid);
2159 
2160  return lwgeom_result;
2161 #endif /* POSTGIS_GEOS_VERSION < 35 */
2162 }
void lwnotice(const char *fmt,...)
Write a notice out to the notice handler.
Definition: lwutil.c:177
char lwgeom_geos_errmsg[LWGEOM_GEOS_ERRMSG_MAXSIZE]
GEOSGeometry * GBOX2GEOS(const GBOX *box)
int32_t lwgeom_get_srid(const LWGEOM *geom)
Return SRID number.
Definition: lwgeom.c:871
static GEOSCoordSequence * lwgeom_get_geos_coordseq_2d(const LWGEOM *g, uint32_t num_points)
unsigned int uint32_t
Definition: uthash.h:78
void lwgeom_geos_error(const char *fmt,...)
#define LW_FALSE
Definition: liblwgeom.h:77
LWGEOM * GEOS2LWGEOM(const GEOSGeometry *geom, char want3d)
void lwgeom_set_srid(LWGEOM *geom, int srid)
Set the SRID on an LWGEOM For collections, only the parent gets an SRID, all the children get SRID_UN...
int lwgeom_count_vertices(const LWGEOM *geom)
Count the total number of vertices in any LWGEOM.
Definition: lwgeom.c:1189
LWCOLLECTION * lwcollection_construct_empty(uint8_t type, int srid, char hasz, char hasm)
Definition: lwcollection.c:94
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
#define COLLECTIONTYPE
Definition: liblwgeom.h:91
LWGEOM * lwcollection_as_lwgeom(const LWCOLLECTION *obj)
Definition: lwgeom.c:268
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