PostGIS  2.5.0dev-r@@SVN_REVISION@@
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 2105 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 ST_Voronoi(), test_lwgeom_voronoi_diagram(), and test_lwgeom_voronoi_diagram_custom_envelope().

2106 {
2107  uint32_t num_points = lwgeom_count_vertices(g);
2108  LWGEOM *lwgeom_result;
2109  char is_3d = LW_FALSE;
2110  int srid = lwgeom_get_srid(g);
2111  GEOSCoordSequence* coords;
2112  GEOSGeometry* geos_geom;
2113  GEOSGeometry* geos_env = NULL;
2114  GEOSGeometry* geos_result;
2115 
2116  if (num_points < 2)
2117  {
2119  return lwcollection_as_lwgeom(empty);
2120  }
2121 
2122  initGEOS(lwnotice, lwgeom_geos_error);
2123 
2124  /* Instead of using the standard LWGEOM2GEOS transformer, we read the vertices of the
2125  * LWGEOM directly and put them into a single GEOS CoordinateSeq that can be used to
2126  * define a LineString. This allows us to process geometry types that may not be
2127  * supported by GEOS, and reduces the memory requirements in cases of many geometries
2128  * with few points (such as LWMPOINT).
2129  */
2130  coords = lwgeom_get_geos_coordseq_2d(g, num_points);
2131  if (!coords)
2132  return NULL;
2133 
2134  geos_geom = GEOSGeom_createLineString(coords);
2135  if (!geos_geom)
2136  {
2137  GEOSCoordSeq_destroy(coords);
2138  return NULL;
2139  }
2140 
2141  if (env)
2142  geos_env = GBOX2GEOS(env);
2143 
2144  geos_result = GEOSVoronoiDiagram(geos_geom, geos_env, tolerance, output_edges);
2145 
2146  GEOSGeom_destroy(geos_geom);
2147  if (env)
2148  GEOSGeom_destroy(geos_env);
2149 
2150  if (!geos_result)
2151  {
2152  lwerror("GEOSVoronoiDiagram: %s", lwgeom_geos_errmsg);
2153  return NULL;
2154  }
2155 
2156  lwgeom_result = GEOS2LWGEOM(geos_result, is_3d);
2157  GEOSGeom_destroy(geos_result);
2158 
2159  lwgeom_set_srid(lwgeom_result, srid);
2160 
2161  return lwgeom_result;
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:909
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:76
uint32_t lwgeom_count_vertices(const LWGEOM *geom)
Count the total number of vertices in any LWGEOM.
Definition: lwgeom.c:1228
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...
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:90
LWGEOM * lwcollection_as_lwgeom(const LWCOLLECTION *obj)
Definition: lwgeom.c:299

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