PostGIS  3.1.6dev-r@@SVN_REVISION@@

◆ ST_TileEnvelope()

Datum ST_TileEnvelope ( PG_FUNCTION_ARGS  )

Definition at line 2036 of file lwgeom_functions_basic.c.

2037 {
2038  GSERIALIZED *bounds;
2039  uint32_t zoomu;
2040  int32_t x, y, zoom;
2041  uint32_t worldTileSize;
2042  double tileGeoSizeX, tileGeoSizeY;
2043  double boundsWidth, boundsHeight;
2044  double x1, y1, x2, y2;
2045  double margin;
2046  /* This is broken, since 3857 doesn't mean "web mercator", it means
2047  the contents of the row in spatial_ref_sys with srid = 3857.
2048  For practical purposes this will work, but in good implementation
2049  we should de-reference in spatial ref sys to confirm that the
2050  srid of the object is EPSG:3857. */
2051  int32_t srid;
2052  GBOX bbox;
2053  LWGEOM *g = NULL;
2054 
2055  POSTGIS_DEBUG(2, "ST_TileEnvelope called");
2056 
2057  zoom = PG_GETARG_INT32(0);
2058  x = PG_GETARG_INT32(1);
2059  y = PG_GETARG_INT32(2);
2060 
2061  bounds = PG_GETARG_GSERIALIZED_P(3);
2062  /*
2063  * We deserialize the geometry and recalculate the bounding box here to get
2064  * 64b floating point precision. The serialized bbox has 32b float is not
2065  * precise enough with big numbers such as the ones used in the default
2066  * parameters, e.g: -20037508.3427892 is transformed into -20037510
2067  */
2068  g = lwgeom_from_gserialized(bounds);
2069  if (lwgeom_calculate_gbox(g, &bbox) != LW_SUCCESS)
2070  elog(ERROR, "%s: Unable to compute bbox", __func__);
2071  srid = g->srid;
2072  lwgeom_free(g);
2073 
2074  /* Avoid crashing with old signature (old sql code with 3 args, new C code with 4) */
2075  margin = PG_NARGS() < 4 ? 0 : PG_GETARG_FLOAT8(4);
2076  /* shrinking by more than 50% would eliminate the tile outright */
2077  if (margin < -0.5)
2078  elog(ERROR, "%s: Margin must not be less than -50%%, margin=%f", __func__, margin);
2079 
2080  boundsWidth = bbox.xmax - bbox.xmin;
2081  boundsHeight = bbox.ymax - bbox.ymin;
2082  if (boundsWidth <= 0 || boundsHeight <= 0)
2083  elog(ERROR, "%s: Geometric bounds are too small", __func__);
2084 
2085  if (zoom < 0 || zoom >= 32)
2086  elog(ERROR, "%s: Invalid tile zoom value, %d", __func__, zoom);
2087 
2088  zoomu = (uint32_t)zoom;
2089  worldTileSize = 0x01u << (zoomu > 31 ? 31 : zoomu);
2090 
2091  if (x < 0 || (uint32_t)x >= worldTileSize)
2092  elog(ERROR, "%s: Invalid tile x value, %d", __func__, x);
2093  if (y < 0 || (uint32_t)y >= worldTileSize)
2094  elog(ERROR, "%s: Invalid tile y value, %d", __func__, y);
2095 
2096  tileGeoSizeX = boundsWidth / worldTileSize;
2097  tileGeoSizeY = boundsHeight / worldTileSize;
2098 
2099  /*
2100  * 1 margin (100%) is the same as a single tile width
2101  * if the size of the tile with margins span more than the total number of tiles,
2102  * reset x1/x2 to the bounds
2103  */
2104  if ((1 + margin * 2) > worldTileSize)
2105  {
2106  x1 = bbox.xmin;
2107  x2 = bbox.xmax;
2108  }
2109  else
2110  {
2111  x1 = bbox.xmin + tileGeoSizeX * (x - margin);
2112  x2 = bbox.xmin + tileGeoSizeX * (x + 1 + margin);
2113  }
2114 
2115  y1 = bbox.ymax - tileGeoSizeY * (y + 1 + margin);
2116  y2 = bbox.ymax - tileGeoSizeY * (y - margin);
2117 
2118  /* Clip y-axis to the given bounds */
2119  if (y1 < bbox.ymin) y1 = bbox.ymin;
2120  if (y2 > bbox.ymax) y2 = bbox.ymax;
2121 
2122  PG_RETURN_POINTER(
2123  geometry_serialize(
2126  srid, x1, y1, x2, y2))));
2127 }
LWGEOM * lwgeom_from_gserialized(const GSERIALIZED *g)
Allocate a new LWGEOM from a GSERIALIZED.
Definition: gserialized.c:239
void lwgeom_free(LWGEOM *geom)
Definition: lwgeom.c:1138
#define LW_SUCCESS
Definition: liblwgeom.h:111
LWGEOM * lwpoly_as_lwgeom(const LWPOLY *obj)
Definition: lwgeom.c:312
LWPOLY * lwpoly_construct_envelope(int32_t srid, double x1, double y1, double x2, double y2)
Definition: lwpoly.c:98
int lwgeom_calculate_gbox(const LWGEOM *lwgeom, GBOX *gbox)
Calculate bounding box of a geometry, automatically taking into account whether it is cartesian or ge...
Definition: lwgeom.c:738
double ymax
Definition: liblwgeom.h:371
double xmax
Definition: liblwgeom.h:369
double ymin
Definition: liblwgeom.h:370
double xmin
Definition: liblwgeom.h:368
int32_t srid
Definition: liblwgeom.h:474

References LW_SUCCESS, lwgeom_calculate_gbox(), lwgeom_free(), lwgeom_from_gserialized(), lwpoly_as_lwgeom(), lwpoly_construct_envelope(), LWGEOM::srid, pixval::x, GBOX::xmax, GBOX::xmin, pixval::y, GBOX::ymax, and GBOX::ymin.

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