PostGIS  3.1.6dev-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.

Definition at line 2017 of file liblwgeom/lwgeom_geos.c.

2018 {
2019  uint32_t num_points = lwgeom_count_vertices(g);
2020  LWGEOM* lwgeom_result;
2021  char is_3d = LW_FALSE;
2022  int32_t srid = lwgeom_get_srid(g);
2023  GEOSCoordSequence* coords;
2024  GEOSGeometry* geos_geom;
2025  GEOSGeometry* geos_env = NULL;
2026  GEOSGeometry* geos_result;
2027 
2028  if (num_points < 2)
2029  {
2031  return lwcollection_as_lwgeom(empty);
2032  }
2033 
2034  initGEOS(lwnotice, lwgeom_geos_error);
2035 
2036  /* Instead of using the standard LWGEOM2GEOS transformer, we read the vertices of the LWGEOM directly and put
2037  * them into a single GEOS CoordinateSeq that can be used to define a LineString. This allows us to process
2038  * geometry types that may not be supported by GEOS, and reduces the memory requirements in cases of many
2039  * geometries with few points (such as LWMPOINT).*/
2040  coords = lwgeom_get_geos_coordseq_2d(g, num_points);
2041  if (!coords) return NULL;
2042 
2043  geos_geom = GEOSGeom_createLineString(coords);
2044  if (!geos_geom)
2045  {
2046  GEOSCoordSeq_destroy(coords);
2047  return NULL;
2048  }
2049 
2050  if (env) geos_env = GBOX2GEOS(env);
2051 
2052  geos_result = GEOSVoronoiDiagram(geos_geom, geos_env, tolerance, output_edges);
2053 
2054  GEOSGeom_destroy(geos_geom);
2055  if (env) GEOSGeom_destroy(geos_env);
2056 
2057  if (!geos_result)
2058  {
2059  lwerror("GEOSVoronoiDiagram: %s", lwgeom_geos_errmsg);
2060  return NULL;
2061  }
2062 
2063  lwgeom_result = GEOS2LWGEOM(geos_result, is_3d);
2064  GEOSGeom_destroy(geos_result);
2065 
2066  lwgeom_set_srid(lwgeom_result, srid);
2067 
2068  return lwgeom_result;
2069 }
char lwgeom_geos_errmsg[LWGEOM_GEOS_ERRMSG_MAXSIZE]
GEOSGeometry * GBOX2GEOS(const GBOX *box)
LWGEOM * GEOS2LWGEOM(const GEOSGeometry *geom, uint8_t want3d)
void lwgeom_geos_error(const char *fmt,...)
static GEOSCoordSequence * lwgeom_get_geos_coordseq_2d(const LWGEOM *g, uint32_t num_points)
#define LW_FALSE
Definition: liblwgeom.h:108
LWGEOM * lwcollection_as_lwgeom(const LWCOLLECTION *obj)
Definition: lwgeom.c:292
#define COLLECTIONTYPE
Definition: liblwgeom.h:122
int32_t lwgeom_get_srid(const LWGEOM *geom)
Return SRID number.
Definition: lwgeom.c:910
void lwgeom_set_srid(LWGEOM *geom, int32_t srid)
Set the SRID on an LWGEOM For collections, only the parent gets an SRID, all the children get SRID_UN...
Definition: lwgeom.c:1530
uint32_t lwgeom_count_vertices(const LWGEOM *geom)
Count the total number of vertices in any LWGEOM.
Definition: lwgeom.c:1229
LWCOLLECTION * lwcollection_construct_empty(uint8_t type, int32_t srid, char hasz, char hasm)
Definition: lwcollection.c:92
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
void lwnotice(const char *fmt,...)
Write a notice out to the notice handler.
Definition: lwutil.c:177

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().

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