PostGIS  2.3.8dev-r@@SVN_REVISION@@

◆ ST_GeometricMedian()

Datum ST_GeometricMedian ( PG_FUNCTION_ARGS  )

Definition at line 1208 of file lwgeom_functions_analytic.c.

References FP_MAX, FP_MIN, dumpnode::geom, geometry_serialize(), LW_FALSE, lwgeom_free(), lwgeom_from_gserialized(), lwgeom_get_bbox(), lwgeom_has_z(), lwgeom_median(), lwpoint_as_lwgeom(), GBOX::xmax, GBOX::xmin, GBOX::ymax, GBOX::ymin, GBOX::zmax, and GBOX::zmin.

Referenced by ST_MinimumBoundingCircle().

1209 {
1210  GSERIALIZED* geom;
1211  GSERIALIZED* result;
1212  LWGEOM* input;
1213  LWPOINT* lwresult;
1214  static const double min_default_tolerance = 1e-8;
1215  double tolerance = min_default_tolerance;
1216  bool compute_tolerance_from_box;
1217  bool fail_if_not_converged;
1218  int max_iter;
1219 
1220  /* Read and validate our input arguments */
1221  if (PG_ARGISNULL(0))
1222  PG_RETURN_NULL();
1223 
1224  compute_tolerance_from_box = PG_ARGISNULL(1);
1225 
1226  if (!compute_tolerance_from_box)
1227  {
1228  tolerance = PG_GETARG_FLOAT8(1);
1229  if (tolerance < 0)
1230  {
1231  lwpgerror("Tolerance must be positive.");
1232  PG_RETURN_NULL();
1233  }
1234  }
1235 
1236  max_iter = PG_ARGISNULL(2) ? -1 : PG_GETARG_INT32(2);
1237  fail_if_not_converged = PG_ARGISNULL(3) ? LW_FALSE : PG_GETARG_BOOL(3);
1238 
1239  if (max_iter < 0)
1240  {
1241  lwpgerror("Maximum iterations must be positive.");
1242  PG_RETURN_NULL();
1243  }
1244 
1245  /* OK, inputs are valid. */
1246  geom = PG_GETARG_GSERIALIZED_P(0);
1247  input = lwgeom_from_gserialized(geom);
1248 
1249  if (compute_tolerance_from_box)
1250  {
1251  /* Compute a default tolerance based on the smallest dimension
1252  * of the geometry's bounding box.
1253  */
1254  static const double tolerance_coefficient = 1e-6;
1255  const GBOX* box = lwgeom_get_bbox(input);
1256 
1257  if (box)
1258  {
1259  double min_dim = FP_MIN(box->xmax - box->xmin, box->ymax - box->ymin);
1260  if (lwgeom_has_z(input))
1261  min_dim = FP_MIN(min_dim, box->zmax - box->zmin);
1262 
1263  /* Apply a lower bound to the computed default tolerance to
1264  * avoid a tolerance of zero in the case of collinear
1265  * points.
1266  */
1267  tolerance = FP_MAX(min_default_tolerance, tolerance_coefficient * min_dim);
1268  }
1269  }
1270 
1271  lwresult = lwgeom_median(input, tolerance, max_iter, fail_if_not_converged);
1272  lwgeom_free(input);
1273 
1274  if(!lwresult)
1275  {
1276  lwpgerror("Error computing geometric median.");
1277  PG_RETURN_NULL();
1278  }
1279 
1280  result = geometry_serialize(lwpoint_as_lwgeom(lwresult));
1281 
1282  PG_RETURN_POINTER(result);
1283 }
LWGEOM * lwgeom_from_gserialized(const GSERIALIZED *g)
Allocate a new LWGEOM from a GSERIALIZED.
double xmax
Definition: liblwgeom.h:292
void lwgeom_free(LWGEOM *geom)
Definition: lwgeom.c:1063
#define FP_MIN(A, B)
int lwgeom_has_z(const LWGEOM *geom)
Return LW_TRUE if geometry has Z ordinates.
Definition: lwgeom.c:849
double zmax
Definition: liblwgeom.h:296
double ymin
Definition: liblwgeom.h:293
LWGEOM * geom
double xmin
Definition: liblwgeom.h:291
#define LW_FALSE
Definition: liblwgeom.h:76
const GBOX * lwgeom_get_bbox(const LWGEOM *lwgeom)
Get a non-empty geometry bounding box, computing and caching it if not already there.
Definition: lwgeom.c:653
double ymax
Definition: liblwgeom.h:294
GSERIALIZED * geometry_serialize(LWGEOM *lwgeom)
double zmin
Definition: liblwgeom.h:295
LWGEOM * lwpoint_as_lwgeom(const LWPOINT *obj)
Definition: lwgeom.c:267
LWPOINT * lwgeom_median(const LWGEOM *g, double tol, uint32_t maxiter, char fail_if_not_converged)
#define FP_MAX(A, B)
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