GDAL
Static Public Member Functions | List of all members
OGRGeometryFactory Class Reference

Create geometry objects from well known text/binary. More...

#include <ogr_geometry.h>

Static Public Member Functions

static OGRErr createFromWkb (unsigned char *, OGRSpatialReference *, OGRGeometry **, int=-1, OGRwkbVariant=wkbVariantOldOgc)
 Create a geometry object of the appropriate type from it's well known binary representation. More...
 
static OGRErr createFromWkt (char **, OGRSpatialReference *, OGRGeometry **)
 Create a geometry object of the appropriate type from it's well known text representation. More...
 
static OGRErr createFromFgf (unsigned char *, OGRSpatialReference *, OGRGeometry **, int=-1, int *=NULL)
 Create a geometry object of the appropriate type from it's FGF (FDO Geometry Format) binary representation. More...
 
static OGRGeometrycreateFromGML (const char *)
 Create geometry from GML. More...
 
static OGRGeometrycreateFromGEOS (GEOSContextHandle_t hGEOSCtxt, GEOSGeom)
 Builds a OGRGeometry* from a GEOSGeom. More...
 
static void destroyGeometry (OGRGeometry *)
 Destroy geometry object. More...
 
static OGRGeometrycreateGeometry (OGRwkbGeometryType)
 Create an empty geometry of desired type. More...
 
static OGRGeometryforceToPolygon (OGRGeometry *)
 Convert to polygon. More...
 
static OGRGeometryforceToLineString (OGRGeometry *, bool bOnlyInOrder=true)
 Convert to line string. More...
 
static OGRGeometryforceToMultiPolygon (OGRGeometry *)
 Convert to multipolygon. More...
 
static OGRGeometryforceToMultiPoint (OGRGeometry *)
 Convert to multipoint. More...
 
static OGRGeometryforceToMultiLineString (OGRGeometry *)
 Convert to multilinestring. More...
 
static OGRGeometryforceTo (OGRGeometry *poGeom, OGRwkbGeometryType eTargetType, const char *const *papszOptions=NULL)
 Convert to another geometry type. More...
 
static OGRGeometryorganizePolygons (OGRGeometry **papoPolygons, int nPolygonCount, int *pbResultValidGeometry, const char **papszOptions=NULL)
 Organize polygons based on geometries. More...
 
static bool haveGEOS ()
 Test if GEOS enabled. More...
 
static OGRGeometrytransformWithOptions (const OGRGeometry *poSrcGeom, OGRCoordinateTransformation *poCT, char **papszOptions)
 Transform a geometry. More...
 
static OGRGeometryapproximateArcAngles (double dfX, double dfY, double dfZ, double dfPrimaryRadius, double dfSecondaryAxis, double dfRotation, double dfStartAngle, double dfEndAngle, double dfMaxAngleStepSizeDegrees)
 Stroke arc to linestring. More...
 
static int GetCurveParmeters (double x0, double y0, double x1, double y1, double x2, double y2, double &R, double &cx, double &cy, double &alpha0, double &alpha1, double &alpha2)
 Returns the parameter of an arc circle. More...
 
static OGRLineStringcurveToLineString (double x0, double y0, double z0, double x1, double y1, double z1, double x2, double y2, double z2, int bHasZ, double dfMaxAngleStepSizeDegrees, const char *const *papszOptions=NULL)
 Converts an arc circle into an approximate line string. More...
 
static OGRCurvecurveFromLineString (const OGRLineString *poLS, const char *const *papszOptions=NULL)
 Try to convert a linestring approximating curves into a curve. More...
 

Detailed Description

Create geometry objects from well known text/binary.

Member Function Documentation

OGRGeometry * OGRGeometryFactory::approximateArcAngles ( double  dfCenterX,
double  dfCenterY,
double  dfZ,
double  dfPrimaryRadius,
double  dfSecondaryRadius,
double  dfRotation,
double  dfStartAngle,
double  dfEndAngle,
double  dfMaxAngleStepSizeDegrees 
)
static

Stroke arc to linestring.

Stroke an arc of a circle to a linestring based on a center point, radius, start angle and end angle, all angles in degrees.

If the dfMaxAngleStepSizeDegrees is zero, then a default value will be used. This is currently 4 degrees unless the user has overridden the value with the OGR_ARC_STEPSIZE configuration variable.

See also
CPLSetConfigOption()
Parameters
dfCenterXcenter X
dfCenterYcenter Y
dfZcenter Z
dfPrimaryRadiusX radius of ellipse.
dfSecondaryRadiusY radius of ellipse.
dfRotationrotation of the ellipse clockwise.
dfStartAngleangle to first point on arc (clockwise of X-positive)
dfEndAngleangle to last point on arc (clockwise of X-positive)
dfMaxAngleStepSizeDegreesthe largest step in degrees along the arc, zero to use the default setting.
Returns
OGRLineString geometry representing an approximation of the arc.
Since
OGR 1.8.0
OGRErr OGRGeometryFactory::createFromFgf ( unsigned char *  pabyData,
OGRSpatialReference poSR,
OGRGeometry **  ppoReturn,
int  nBytes = -1,
int *  pnBytesConsumed = NULL 
)
static

Create a geometry object of the appropriate type from it's FGF (FDO Geometry Format) binary representation.

Also note that this is a static method, and that there is no need to instantiate an OGRGeometryFactory object.

The C function OGR_G_CreateFromFgf() is the same as this method.

Parameters
pabyDatapointer to the input BLOB data.
poSRpointer to the spatial reference to be assigned to the created geometry object. This may be NULL.
ppoReturnthe newly created geometry object will be assigned to the indicated pointer on return. This will be NULL in case of failure, but NULL might be a valid return for a NULL shape.
nBytesthe number of bytes available in pabyData.
pnBytesConsumedif not NULL, it will be set to the number of bytes consumed (at most nBytes).
Returns
OGRERR_NONE if all goes well, otherwise any of OGRERR_NOT_ENOUGH_DATA, OGRERR_UNSUPPORTED_GEOMETRY_TYPE, or OGRERR_CORRUPT_DATA may be returned.
OGRGeometry * OGRGeometryFactory::createFromGEOS ( GEOSContextHandle_t  hGEOSCtxt,
GEOSGeom  geosGeom 
)
static

Builds a OGRGeometry* from a GEOSGeom.

Parameters
hGEOSCtxtGEOS context
geosGeomGEOS geometry
Returns
a OGRGeometry*
OGRGeometry * OGRGeometryFactory::createFromGML ( const char *  pszData)
static

Create geometry from GML.

This method translates a fragment of GML containing only the geometry portion into a corresponding OGRGeometry. There are many limitations on the forms of GML geometries supported by this parser, but they are too numerous to list here.

The following GML2 elements are parsed : Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, MultiGeometry.

(OGR >= 1.8.0) The following GML3 elements are parsed : Surface, MultiSurface, PolygonPatch, Triangle, Rectangle, Curve, MultiCurve, LineStringSegment, Arc, Circle, CompositeSurface, OrientableSurface, Solid, Tin, TriangulatedSurface.

Arc and Circle elements are stroked to linestring, by using a 4 degrees step, unless the user has overridden the value with the OGR_ARC_STEPSIZE configuration variable.

The C function OGR_G_CreateFromGML() is the same as this method.

Parameters
pszDataThe GML fragment for the geometry.
Returns
a geometry on success, or NULL on error.
OGRErr OGRGeometryFactory::createFromWkb ( unsigned char *  pabyData,
OGRSpatialReference poSR,
OGRGeometry **  ppoReturn,
int  nBytes = -1,
OGRwkbVariant  eWkbVariant = wkbVariantOldOgc 
)
static

Create a geometry object of the appropriate type from it's well known binary representation.

Note that if nBytes is passed as zero, no checking can be done on whether the pabyData is sufficient. This can result in a crash if the input data is corrupt. This function returns no indication of the number of bytes from the data source actually used to represent the returned geometry object. Use OGRGeometry::WkbSize() on the returned geometry to establish the number of bytes it required in WKB format.

Also note that this is a static method, and that there is no need to instantiate an OGRGeometryFactory object.

The C function OGR_G_CreateFromWkb() is the same as this method.

Parameters
pabyDatapointer to the input BLOB data.
poSRpointer to the spatial reference to be assigned to the created geometry object. This may be NULL.
ppoReturnthe newly created geometry object will be assigned to the indicated pointer on return. This will be NULL in case of failure. If not NULL, *ppoReturn should be freed with OGRGeometryFactory::destroyGeometry() after use.
nBytesthe number of bytes available in pabyData, or -1 if it isn't known.
eWkbVariantWKB variant.
Returns
OGRERR_NONE if all goes well, otherwise any of OGRERR_NOT_ENOUGH_DATA, OGRERR_UNSUPPORTED_GEOMETRY_TYPE, or OGRERR_CORRUPT_DATA may be returned.
OGRErr OGRGeometryFactory::createFromWkt ( char **  ppszData,
OGRSpatialReference poSR,
OGRGeometry **  ppoReturn 
)
static

Create a geometry object of the appropriate type from it's well known text representation.

The C function OGR_G_CreateFromWkt() is the same as this method.

Parameters
ppszDatainput zero terminated string containing well known text representation of the geometry to be created. The pointer is updated to point just beyond that last character consumed.
poSRpointer to the spatial reference to be assigned to the created geometry object. This may be NULL.
ppoReturnthe newly created geometry object will be assigned to the indicated pointer on return. This will be NULL if the method fails. If not NULL, *ppoReturn should be freed with OGRGeometryFactory::destroyGeometry() after use.

Example:

   const char* wkt= "POINT(0 0)";
   // cast because OGR_G_CreateFromWkt will move the pointer
   char* pszWkt = (char*) wkt;
   OGRSpatialReferenceH ref = OSRNewSpatialReference(NULL);
   OGRGeometryH new_geom;
   OGRErr err = OGR_G_CreateFromWkt(&pszWkt, ref, &new_geom);
 
Returns
OGRERR_NONE if all goes well, otherwise any of OGRERR_NOT_ENOUGH_DATA, OGRERR_UNSUPPORTED_GEOMETRY_TYPE, or OGRERR_CORRUPT_DATA may be returned.
OGRGeometry * OGRGeometryFactory::createGeometry ( OGRwkbGeometryType  eGeometryType)
static

Create an empty geometry of desired type.

This is equivalent to allocating the desired geometry with new, but the allocation is guaranteed to take place in the context of the GDAL/OGR heap.

This method is the same as the C function OGR_G_CreateGeometry().

Parameters
eGeometryTypethe type code of the geometry class to be instantiated.
Returns
the newly create geometry or NULL on failure. Should be freed with OGRGeometryFactory::destroyGeometry() after use.
OGRCurve * OGRGeometryFactory::curveFromLineString ( const OGRLineString poLS,
const char *const *  papszOptions = NULL 
)
static

Try to convert a linestring approximating curves into a curve.

This method can return a COMPOUNDCURVE, a CIRCULARSTRING or a LINESTRING.

This method is the reverse of curveFromLineString().

Parameters
poLShandle to the geometry to convert.
papszOptionsoptions as a null-terminated list of strings. Unused for now. Must be set to NULL.
Returns
the converted geometry (ownership to caller).
Since
GDAL 2.0
OGRLineString * OGRGeometryFactory::curveToLineString ( double  x0,
double  y0,
double  z0,
double  x1,
double  y1,
double  z1,
double  x2,
double  y2,
double  z2,
int  bHasZ,
double  dfMaxAngleStepSizeDegrees,
const char *const *  papszOptions = NULL 
)
static

Converts an arc circle into an approximate line string.

The arc circle is defined by a first point, an intermediate point and a final point.

The provided dfMaxAngleStepSizeDegrees is a hint. The discretization algorithm may pick a slightly different value.

So as to avoid gaps when rendering curve polygons that share common arcs, this method is guaranteed to return a line with reversed vertex if called with inverted first and final point, and identical intermediate point.

Parameters
x0x of first point
y0y of first point
z0z of first point
x1x of intermediate point
y1y of intermediate point
z1z of intermediate point
x2x of final point
y2y of final point
z2z of final point
bHasZTRUE if z must be taken into account
dfMaxAngleStepSizeDegreesthe largest step in degrees along the arc, zero to use the default setting.
papszOptionsoptions as a null-terminated list of strings or NULL. Recognized options:
  • ADD_INTERMEDIATE_POINT=STEALTH/YES/NO (Default to STEALTH). Determine if and how the intermediate point must be output in the linestring. If set to STEALTH, no explicit intermediate point is added but its properties are encoded in low significant bits of intermediate points and OGRGeometryFactory::curveFromLineString() can decode them. This is the best compromise for round-tripping in OGR and better results with PostGIS ST_LineToCurve() If set to YES, the intermediate point is explicitly added to the linestring. If set to NO, the intermediate point is not explicitly added.
Returns
the converted geometry (ownership to caller).
Since
GDAL 2.0
void OGRGeometryFactory::destroyGeometry ( OGRGeometry poGeom)
static

Destroy geometry object.

Equivalent to invoking delete on a geometry, but it guaranteed to take place within the context of the GDAL/OGR heap.

This method is the same as the C function OGR_G_DestroyGeometry().

Parameters
poGeomthe geometry to deallocate.
OGRGeometry * OGRGeometryFactory::forceTo ( OGRGeometry poGeom,
OGRwkbGeometryType  eTargetType,
const char *const *  papszOptions = NULL 
)
static

Convert to another geometry type.

Tries to force the provided geometry to the specified geometry type.

It can promote 'single' geometry type to their corresponding collection type (see OGR_GT_GetCollection()) or the reverse. non-linear geometry type to their corresponding linear geometry type (see OGR_GT_GetLinear()), by possibly approximating circular arcs they may contain. Regarding conversion from linear geometry types to curve geometry types, only "wraping" will be done. No attempt to retrieve potential circular arcs by de-approximating stroking will be done. For that, OGRGeometry::getCurveGeometry() can be used.

The passed in geometry is consumed and a new one returned (or potentially the same one).

Parameters
poGeomthe input geometry - ownership is passed to the method.
eTargetTypetarget output geometry type.
papszOptionsoptions as a null-terminated list of strings or NULL.
Returns
new geometry.
Since
GDAL 2.0
OGRGeometry * OGRGeometryFactory::forceToLineString ( OGRGeometry poGeom,
bool  bOnlyInOrder = true 
)
static

Convert to line string.

Tries to force the provided geometry to be a line string. This nominally effects a change on multilinestrings. In GDAL 2.0, for polygons or curvepolygons that have a single exterior ring, it will return the ring. For circular strings or compound curves, it will return an approximated line string.

The passed in geometry is consumed and a new one returned (or potentially the same one).

Parameters
poGeomthe input geometry - ownership is passed to the method.
bOnlyInOrderflag that, if set to FALSE, indicate that the order of points in a linestring might be reversed if it enables to match the extremity of another linestring. If set to TRUE, the start of a linestring must match the end of another linestring.
Returns
new geometry.
OGRGeometry * OGRGeometryFactory::forceToMultiLineString ( OGRGeometry poGeom)
static

Convert to multilinestring.

Tries to force the provided geometry to be a multilinestring.

  • linestrings are placed in a multilinestring.
  • circularstrings and compoundcurves will be approximated and placed in a multilinestring.
  • geometry collections will be converted to multilinestring if they only contain linestrings.
  • polygons will be changed to a collection of linestrings (one per ring).
  • curvepolygons will be approximated and changed to a collection of ( linestrings (one per ring).

The passed in geometry is consumed and a new one returned (or potentially the same one).

Returns
new geometry.
OGRGeometry * OGRGeometryFactory::forceToMultiPoint ( OGRGeometry poGeom)
static

Convert to multipoint.

Tries to force the provided geometry to be a multipoint. Currently this just effects a change on points or collection of points. The passed in geometry is consumed and a new one returned (or potentially the same one).

Returns
new geometry.
OGRGeometry * OGRGeometryFactory::forceToMultiPolygon ( OGRGeometry poGeom)
static

Convert to multipolygon.

Tries to force the provided geometry to be a multipolygon. Currently this just effects a change on polygons. The passed in geometry is consumed and a new one returned (or potentially the same one).

Returns
new geometry.
OGRGeometry * OGRGeometryFactory::forceToPolygon ( OGRGeometry poGeom)
static

Convert to polygon.

Tries to force the provided geometry to be a polygon. This effects a change on multipolygons. Starting with GDAL 2.0, curve polygons or closed curves will be changed to polygons. The passed in geometry is consumed and a new one returned (or potentially the same one).

Parameters
poGeomthe input geometry - ownership is passed to the method.
Returns
new geometry.
int OGRGeometryFactory::GetCurveParmeters ( double  x0,
double  y0,
double  x1,
double  y1,
double  x2,
double  y2,
double &  R,
double &  cx,
double &  cy,
double &  alpha0,
double &  alpha1,
double &  alpha2 
)
static

Returns the parameter of an arc circle.

Parameters
x0x of first point
y0y of first point
x1x of intermediate point
y1y of intermediate point
x2x of final point
y2y of final point
Rradius (output)
cxx of arc center (output)
cyy of arc center (output)
alpha0angle between center and first point (output)
alpha1angle between center and intermediate point (output)
alpha2angle between center and final point (output)
Returns
TRUE if the points are not aligned and define an arc circle.
Since
GDAL 2.0
bool OGRGeometryFactory::haveGEOS ( )
static

Test if GEOS enabled.

This static method returns TRUE if GEOS support is built into OGR, otherwise it returns FALSE.

Returns
TRUE if available, otherwise FALSE.
OGRGeometry * OGRGeometryFactory::organizePolygons ( OGRGeometry **  papoPolygons,
int  nPolygonCount,
int *  pbIsValidGeometry,
const char **  papszOptions = NULL 
)
static

Organize polygons based on geometries.

Analyse a set of rings (passed as simple polygons), and based on a geometric analysis convert them into a polygon with inner rings, (or a MultiPolygon if dealing with more than one polygon) that follow the OGC Simple Feature specification.

All the input geometries must be OGRPolygon/OGRCurvePolygon with only a valid exterior ring (at least 4 points) and no interior rings.

The passed in geometries become the responsibility of the method, but the papoPolygons "pointer array" remains owned by the caller.

For faster computation, a polygon is considered to be inside another one if a single point of its external ring is included into the other one. (unless 'OGR_DEBUG_ORGANIZE_POLYGONS' configuration option is set to TRUE. In that case, a slower algorithm that tests exact topological relationships is used if GEOS is available.)

In cases where a big number of polygons is passed to this function, the default processing may be really slow. You can skip the processing by adding METHOD=SKIP to the option list (the result of the function will be a multi-polygon with all polygons as toplevel polygons) or only make it analyze counterclockwise polygons by adding METHOD=ONLY_CCW to the option list if you can assume that the outline of holes is counterclockwise defined (this is the convention for example in shapefiles, Personal Geodatabases or File Geodatabases).

For FileGDB, in most cases, but not always, a faster method than ONLY_CCW can be used. It is CCW_INNER_JUST_AFTER_CW_OUTER. When using it, inner rings are assumed to be counterclockwise oriented, and following immediately the outer ring (clockwise oriented) that they belong to. If that assumption is not met, an inner ring could be attached to the wrong outer ring, so this method must be used with care.

If the OGR_ORGANIZE_POLYGONS configuration option is defined, its value will override the value of the METHOD option of papszOptions (useful to modify the behaviour of the shapefile driver)

Parameters
papoPolygonsarray of geometry pointers - should all be OGRPolygons. Ownership of the geometries is passed, but not of the array itself.
nPolygonCountnumber of items in papoPolygons
pbIsValidGeometryvalue will be set TRUE if result is valid or FALSE otherwise.
papszOptionsa list of strings for passing options
Returns
a single resulting geometry (either OGRPolygon, OGRCurvePolygon, OGRMultiPolygon, OGRMultiSurface or OGRGeometryCollection).
OGRGeometry * OGRGeometryFactory::transformWithOptions ( const OGRGeometry poSrcGeom,
OGRCoordinateTransformation poCT,
char **  papszOptions 
)
static

Transform a geometry.

Parameters
poSrcGeomsource geometry
poCTcoordinate transformation object.
papszOptionsoptions. Including WRAPDATELINE=YES.
Returns
(new) transformed geometry.

The documentation for this class was generated from the following files:

Generated for GDAL by doxygen 1.8.8.