GDAL

Utility class to store a collection of curves. More...
#include <ogr_geometry.h>
Public Member Functions  
OGRCompoundCurve ()  
Create an empty compound curve.  
OGRCompoundCurve (const OGRCompoundCurve &other)  
Copy constructor. More...  
OGRCompoundCurve &  operator= (const OGRCompoundCurve &other) 
Assignment operator. More...  
virtual int  WkbSize () const override 
Returns size of related binary representation. More...  
virtual OGRErr  importFromWkb (const unsigned char *, int, OGRwkbVariant, int &nBytesConsumedOut) override 
Assign geometry from well known binary data. More...  
virtual OGRErr  exportToWkb (OGRwkbByteOrder, unsigned char *, OGRwkbVariant=wkbVariantOldOgc) const override 
Convert a geometry into well known binary format. More...  
virtual OGRErr  importFromWkt (char **) override 
Assign geometry from well known text data. More...  
virtual OGRErr  exportToWkt (char **ppszDstText, OGRwkbVariant=wkbVariantOldOgc) const override 
Convert a geometry into well known text format. More...  
virtual OGRGeometry *  clone () const override 
Make a copy of this object. More...  
virtual void  empty () override 
Clear geometry information. More...  
virtual void  getEnvelope (OGREnvelope *psEnvelope) const override 
Computes and returns the bounding envelope for this geometry in the passed psEnvelope structure. More...  
virtual void  getEnvelope (OGREnvelope3D *psEnvelope) const override 
Computes and returns the bounding envelope (3D) for this geometry in the passed psEnvelope structure. More...  
virtual OGRBoolean  IsEmpty () const override 
Returns TRUE (nonzero) if the object has no points. More...  
virtual double  get_Length () const override 
Returns the length of the curve. More...  
virtual void  StartPoint (OGRPoint *) const override 
Return the curve start point. More...  
virtual void  EndPoint (OGRPoint *) const override 
Return the curve end point. More...  
virtual void  Value (double, OGRPoint *) const override 
Fetch point at given distance along curve. More...  
virtual OGRLineString *  CurveToLine (double dfMaxAngleStepSizeDegrees=0, const char *const *papszOptions=nullptr) const override 
Return a linestring from a curve geometry. More...  
virtual int  getNumPoints () const override 
Return the number of points of a curve geometry. More...  
virtual double  get_AreaOfCurveSegments () const override 
Return area of curve segments. More...  
virtual double  get_Area () const override 
Get the area of the (closed) curve. More...  
virtual OGRBoolean  Equals (OGRGeometry *) const override 
Returns TRUE if two geometries are equivalent. More...  
int  getNumCurves () const 
Return the number of curves. More...  
OGRCurve *  getCurve (int) 
Fetch reference to indicated internal ring. More...  
const OGRCurve *  getCurve (int) const 
Fetch reference to indicated internal ring. More...  
virtual void  setCoordinateDimension (int nDimension) override 
Set the coordinate dimension. More...  
virtual void  set3D (OGRBoolean bIs3D) override 
Add or remove the Z coordinate dimension. More...  
virtual void  setMeasured (OGRBoolean bIsMeasured) override 
Add or remove the M coordinate dimension. More...  
virtual void  assignSpatialReference (OGRSpatialReference *poSR) override 
Assign spatial reference to this object. More...  
OGRErr  addCurve (OGRCurve *, double dfToleranceEps=1e14) 
Add a curve to the container. More...  
OGRErr  addCurveDirectly (OGRCurve *, double dfToleranceEps=1e14) 
Add a curve directly to the container. More...  
OGRCurve *  stealCurve (int) 
"Steal" reference to curve. More...  
virtual OGRPointIterator *  getPointIterator () const override 
Returns a point iterator over the curve. More...  
virtual OGRwkbGeometryType  getGeometryType () const override 
Fetch geometry type. More...  
virtual const char *  getGeometryName () const override 
Fetch WKT name for geometry type. More...  
virtual OGRErr  transform (OGRCoordinateTransformation *poCT) override 
Apply arbitrary coordinate transformation to geometry. More...  
virtual void  flattenTo2D () override 
Convert geometry to strictly 2D. More...  
virtual void  segmentize (double dfMaxLength) override 
Modify the geometry such it has no segment longer then the given distance. More...  
virtual OGRBoolean  hasCurveGeometry (int bLookForNonLinear=FALSE) const override 
Returns if this geometry is or has curve geometry. More...  
virtual OGRGeometry *  getLinearGeometry (double dfMaxAngleStepSizeDegrees=0, const char *const *papszOptions=nullptr) const override 
Return, possibly approximate, noncurve version of this geometry. More...  
virtual void  swapXY () override 
Swap x and y coordinates. More...  
Public Member Functions inherited from OGRCurve  
virtual int  get_IsClosed () const 
Return TRUE if curve is closed. More...  
virtual int  getDimension () const override 
Get the dimension of this object. More...  
virtual OGRBoolean  IsConvex () const 
Returns if a (closed) curve forms a convex shape. More...  
Public Member Functions inherited from OGRGeometry  
OGRGeometry (const OGRGeometry &other)  
Copy constructor. More...  
OGRGeometry &  operator= (const OGRGeometry &other) 
Assignment operator. More...  
virtual int  getCoordinateDimension () const 
Get the dimension of the coordinates in this object. More...  
int  CoordinateDimension () const 
Get the dimension of the coordinates in this object. More...  
virtual OGRBoolean  IsValid () const 
Test if the geometry is valid. More...  
virtual OGRBoolean  IsSimple () const 
Test if the geometry is simple. More...  
OGRBoolean  Is3D () const 
OGRBoolean  IsMeasured () const 
virtual OGRBoolean  IsRing () const 
Test if the geometry is a ring. More...  
OGRErr  importFromWkb (unsigned char *, int=1, OGRwkbVariant=wkbVariantOldOgc) 
Assign geometry from well known binary data. More...  
OGRwkbGeometryType  getIsoGeometryType () const 
Get the geometry type that conforms with ISO SQL/MM Part3. More...  
virtual void  dumpReadable (FILE *, const char *=nullptr, char **papszOptions=nullptr) const 
Dump geometry in well known text format to indicated output file. More...  
virtual char *  exportToGML (const char *const *papszOptions=nullptr) const 
Convert a geometry into GML format. More...  
virtual char *  exportToKML () const 
Convert a geometry into KML format. More...  
virtual char *  exportToJson () const 
Convert a geometry into GeoJSON format. More...  
virtual GEOSGeom  exportToGEOS (GEOSContextHandle_t hGEOSCtxt) const CPL_WARN_UNUSED_RESULT 
Returns a GEOSGeom object corresponding to the geometry. More...  
virtual OGRGeometry *  getCurveGeometry (const char *const *papszOptions=nullptr) const CPL_WARN_UNUSED_RESULT 
Return curve version of this geometry. More...  
virtual void  closeRings () 
Force rings to be closed. More...  
OGRSpatialReference *  getSpatialReference (void) const 
Returns spatial reference system for object. More...  
OGRErr  transformTo (OGRSpatialReference *poSR) 
Transform geometry to new spatial reference system. More...  
virtual OGRBoolean  Intersects (const OGRGeometry *) const 
Do these features intersect? More...  
virtual OGRBoolean  Disjoint (const OGRGeometry *) const 
Test for disjointness. More...  
virtual OGRBoolean  Touches (const OGRGeometry *) const 
Test for touching. More...  
virtual OGRBoolean  Crosses (const OGRGeometry *) const 
Test for crossing. More...  
virtual OGRBoolean  Within (const OGRGeometry *) const 
Test for containment. More...  
virtual OGRBoolean  Contains (const OGRGeometry *) const 
Test for containment. More...  
virtual OGRBoolean  Overlaps (const OGRGeometry *) const 
Test for overlap. More...  
virtual OGRGeometry *  Boundary () const CPL_WARN_UNUSED_RESULT 
Compute boundary. More...  
virtual double  Distance (const OGRGeometry *) const 
Compute distance between two geometries. More...  
virtual OGRGeometry *  ConvexHull () const CPL_WARN_UNUSED_RESULT 
Compute convex hull. More...  
virtual OGRGeometry *  Buffer (double dfDist, int nQuadSegs=30) const CPL_WARN_UNUSED_RESULT 
Compute buffer of geometry. More...  
virtual OGRGeometry *  Intersection (const OGRGeometry *) const CPL_WARN_UNUSED_RESULT 
Compute intersection. More...  
virtual OGRGeometry *  Union (const OGRGeometry *) const CPL_WARN_UNUSED_RESULT 
Compute union. More...  
virtual OGRGeometry *  UnionCascaded () const CPL_WARN_UNUSED_RESULT 
Compute union using cascading. More...  
virtual OGRGeometry *  Difference (const OGRGeometry *) const CPL_WARN_UNUSED_RESULT 
Compute difference. More...  
virtual OGRGeometry *  SymDifference (const OGRGeometry *) const CPL_WARN_UNUSED_RESULT 
Compute symmetric difference. More...  
virtual OGRErr  Centroid (OGRPoint *poPoint) const 
Compute the geometry centroid. More...  
virtual OGRGeometry *  Simplify (double dTolerance) const CPL_WARN_UNUSED_RESULT 
Simplify the geometry. More...  
OGRGeometry *  SimplifyPreserveTopology (double dTolerance) const CPL_WARN_UNUSED_RESULT 
Simplify the geometry while preserving topology. More...  
virtual OGRGeometry *  DelaunayTriangulation (double dfTolerance, int bOnlyEdges) const CPL_WARN_UNUSED_RESULT 
Return a Delaunay triangulation of the vertices of the geometry. More...  
virtual OGRGeometry *  Polygonize () const CPL_WARN_UNUSED_RESULT 
Polygonizes a set of sparse edges. More...  
virtual double  Distance3D (const OGRGeometry *poOtherGeom) const 
Returns the 3D distance between two geometries. More...  
Additional Inherited Members  
Static Public Member Functions inherited from OGRCurve  
static OGRCompoundCurve *  CastToCompoundCurve (OGRCurve *puCurve) 
Cast to compound curve. More...  
static OGRLineString *  CastToLineString (OGRCurve *poCurve) 
Cast to linestring. More...  
static OGRLinearRing *  CastToLinearRing (OGRCurve *poCurve) 
Cast to linear ring. More...  
Static Public Member Functions inherited from OGRGeometry  
static GEOSContextHandle_t  createGEOSContext () 
Create a new GEOS context. More...  
static void  freeGEOSContext (GEOSContextHandle_t hGEOSCtxt) 
Destroy a GEOS context. More...  
Protected Member Functions inherited from OGRCurve  
virtual int  ContainsPoint (const OGRPoint *p) const 
Returns if a point is contained in a (closed) curve. More...  
virtual int  IntersectsPoint (const OGRPoint *p) const 
Returns if a point intersects a (closed) curve. More...  
Utility class to store a collection of curves.
Used as a member of OGRCompoundCurve and OGRCurvePolygon.
This class is only exported because of linking issues. It should never be directly used.
Compatibility: ISO SQL/MM Part 3.
OGRCompoundCurve::OGRCompoundCurve  (  const OGRCompoundCurve &  other  ) 
Copy constructor.
Note: before GDAL 2.1, only the default implementation of the constructor existed, which could be unsafe to use.
Add a curve to the container.
The passed geometry is cloned to make an internal copy.
There is no ISO SQL/MM analog to this method.
This method is the same as the C function OGR_G_AddGeometry().
poCurve  geometry to add to the container. 
dfToleranceEps  tolerance when checking that the first point of a segment matches then end point of the previous one. Default value: 1e14. 
Add a curve directly to the container.
Ownership of the passed geometry is taken by the container rather than cloning as addCurve() does.
There is no ISO SQL/MM analog to this method.
This method is the same as the C function OGR_G_AddGeometryDirectly().
poCurve  geometry to add to the container. 
dfToleranceEps  tolerance when checking that the first point of a segment matches then end point of the previous one. Default value: 1e14. 

overridevirtual 
Assign spatial reference to this object.
Any existing spatial reference is replaced, but under no circumstances does this result in the object being reprojected. It is just changing the interpretation of the existing geometry. Note that assigning a spatial reference increments the reference count on the OGRSpatialReference, but does not copy it.
Starting with GDAL 2.3, this will also assign the spatial reference to potential subgeometries of the geometry (OGRGeometryCollection, OGRCurvePolygon/OGRPolygon, OGRCompoundCurve, OGRPolyhedralSurface and their derived classes).
This is similar to the SFCOM IGeometry::put_SpatialReference() method.
This method is the same as the C function OGR_G_AssignSpatialReference().
poSR  new spatial reference system to apply. 
Reimplemented from OGRGeometry.

overridevirtual 
Make a copy of this object.
This method relates to the SFCOM IGeometry::clone() method.
This method is the same as the C function OGR_G_Clone().
Implements OGRGeometry.

overridevirtual 
Return a linestring from a curve geometry.
The returned geometry is a new instance whose ownership belongs to the caller.
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.
This method relates to the ISO SQL/MM Part 3 ICurve::CurveToLine() method.
This function is the same as C function OGR_G_CurveToLine().
dfMaxAngleStepSizeDegrees  the largest step in degrees along the arc, zero to use the default setting. 
papszOptions  options as a nullterminated list of strings or NULL. See OGRGeometryFactory::curveToLineString() for valid options. 
Implements OGRCurve.

overridevirtual 
Clear geometry information.
This restores the geometry to it's initial state after construction, and before assignment of actual geometry.
This method relates to the SFCOM IGeometry::Empty() method.
This method is the same as the C function OGR_G_Empty().
Implements OGRGeometry.

overridevirtual 
Return the curve end point.
This method relates to the SF COM ICurve::get_EndPoint() method.
poPoint  the point to be assigned the end location. 
Implements OGRCurve.

overridevirtual 
Returns TRUE if two geometries are equivalent.
This operation implements the SQL/MM ST_OrderingEquals() operation.
The comparison is done in a structural way, that is to say that the geometry types must be identical, as well as the number and ordering of subgeometries and vertices. Or equivalently, two geometries are considered equal by this method if their WKT/WKB representation is equal. Note: this must be distinguished for equality in a spatial way (which is the purpose of the ST_Equals() operation).
This method is the same as the C function OGR_G_Equals().
Implements OGRGeometry.

overridevirtual 
Convert a geometry into well known binary format.
This method relates to the SFCOM IWks::ExportToWKB() method.
This method is the same as the C function OGR_G_ExportToWkb() or OGR_G_ExportToIsoWkb(), depending on the value of eWkbVariant.
eByteOrder  One of wkbXDR or wkbNDR indicating MSB or LSB byte order respectively. 
pabyData  a buffer into which the binary representation is written. This buffer must be at least OGRGeometry::WkbSize() byte in size. 
eWkbVariant  What standard to use when exporting geometries with three dimensions (or more). The default wkbVariantOldOgc is the historical OGR variant. wkbVariantIso is the variant defined in ISO SQL/MM and adopted by OGC for SFSQL 1.2. 
Implements OGRGeometry.

overridevirtual 
Convert a geometry into well known text format.
This method relates to the SFCOM IWks::ExportToWKT() method.
This method is the same as the C function OGR_G_ExportToWkt().
ppszDstText  a text buffer is allocated by the program, and assigned to the passed pointer. After use, *ppszDstText should be freed with CPLFree(). 
eWkbVariant  the specification that must be conformed too :

Implements OGRGeometry.

overridevirtual 
Convert geometry to strictly 2D.
In a sense this converts all Z coordinates to 0.0.
This method is the same as the C function OGR_G_FlattenTo2D().
Implements OGRGeometry.

overridevirtual 
Get the area of the (closed) curve.
This method is designed to be used by OGRCurvePolygon::get_Area().
Implements OGRCurve.

overridevirtual 

overridevirtual 
Returns the length of the curve.
This method relates to the SFCOM ICurve::get_Length() method.
Implements OGRCurve.
OGRCurve * OGRCompoundCurve::getCurve  (  int  iRing  ) 
Fetch reference to indicated internal ring.
Note that the returned curve pointer is to an internal data object of the OGRCompoundCurve. It should not be modified or deleted by the application, and the pointer is only valid till the polygon is next modified. Use the OGRGeometry::clone() method to make a separate copy within the application.
Relates to the ISO SQL/MM ST_CurveN() function.
iRing  curve index from 0 to getNumCurves()  1. 
const OGRCurve * OGRCompoundCurve::getCurve  (  int  iCurve  )  const 
Fetch reference to indicated internal ring.
Note that the returned curve pointer is to an internal data object of the OGRCompoundCurve. It should not be modified or deleted by the application, and the pointer is only valid till the polygon is next modified. Use the OGRGeometry::clone() method to make a separate copy within the application.
Relates to the ISO SQL/MM ST_CurveN() function.
iCurve  curve index from 0 to getNumCurves()  1. 

overridevirtual 
Computes and returns the bounding envelope for this geometry in the passed psEnvelope structure.
This method is the same as the C function OGR_G_GetEnvelope().
psEnvelope  the structure in which to place the results. 
Implements OGRGeometry.

overridevirtual 
Computes and returns the bounding envelope (3D) for this geometry in the passed psEnvelope structure.
This method is the same as the C function OGR_G_GetEnvelope3D().
psEnvelope  the structure in which to place the results. 
Implements OGRGeometry.

overridevirtual 
Fetch WKT name for geometry type.
There is no SFCOM analog to this method.
This method is the same as the C function OGR_G_GetGeometryName().
Implements OGRGeometry.

overridevirtual 
Fetch geometry type.
Note that the geometry type may include the 2.5D flag. To get a 2D flattened version of the geometry type apply the wkbFlatten() macro to the return result.
This method is the same as the C function OGR_G_GetGeometryType().
Implements OGRGeometry.

overridevirtual 
Return, possibly approximate, noncurve version of this geometry.
Returns a geometry that has no CIRCULARSTRING, COMPOUNDCURVE, CURVEPOLYGON, MULTICURVE or MULTISURFACE in it, by approximating curve geometries.
The ownership of the returned geometry belongs to the caller.
The reverse method is OGRGeometry::getCurveGeometry().
This method is the same as the C function OGR_G_GetLinearGeometry().
dfMaxAngleStepSizeDegrees  the largest step in degrees along the arc, zero to use the default setting. 
papszOptions  options as a nullterminated list of strings. See OGRGeometryFactory::curveToLineString() for valid options. 
Reimplemented from OGRGeometry.
int OGRCompoundCurve::getNumCurves  (  )  const 
Return the number of curves.
Note that the number of curves making this compound curve.
Relates to the ISO SQL/MM ST_NumCurves() function.

overridevirtual 
Return the number of points of a curve geometry.
This method, as a method of OGRCurve, does not relate to a standard. For circular strings or linestrings, it returns the number of points, conforming to SF COM NumPoints(). For compound curves, it returns the sum of the number of points of each of its components (non including intermediate starting/ending points of the different parts).
Implements OGRCurve.

overridevirtual 
Returns a point iterator over the curve.
The curve must not be modified while an iterator exists on it.
The iterator must be destroyed with OGRPointIterator::destroy().
Implements OGRCurve.

overridevirtual 
Returns if this geometry is or has curve geometry.
Returns if a geometry is, contains or may contain a CIRCULARSTRING, COMPOUNDCURVE, CURVEPOLYGON, MULTICURVE or MULTISURFACE.
If bLookForNonLinear is set to TRUE, it will be actually looked if the geometry or its subgeometries are or contain a nonlinear geometry in them. In which case, if the method returns TRUE, it means that getLinearGeometry() would return an approximate version of the geometry. Otherwise, getLinearGeometry() would do a conversion, but with just converting container type, like COMPOUNDCURVE > LINESTRING, MULTICURVE > MULTILINESTRING or MULTISURFACE > MULTIPOLYGON, resulting in a "lossless" conversion.
This method is the same as the C function OGR_G_HasCurveGeometry().
bLookForNonLinear  set it to TRUE to check if the geometry is or contains a CIRCULARSTRING. 
Reimplemented from OGRGeometry.

overridevirtual 
Assign geometry from well known binary data.
The object must have already been instantiated as the correct derived type of geometry object to match the binaries type. This method is used by the OGRGeometryFactory class, but not normally called by application code.
This method relates to the SFCOM IWks::ImportFromWKB() method.
This method is the same as the C function OGR_G_ImportFromWkb().
pabyData  the binary input data. 
nSize  the size of pabyData in bytes, or 1 if not known. 
eWkbVariant  if wkbVariantPostGIS1, special interpretation is done for curve geometries code 
nBytesConsumedOut  output parameter. Number of bytes consumed. 
Implements OGRGeometry.

overridevirtual 
Assign geometry from well known text data.
The object must have already been instantiated as the correct derived type of geometry object to match the text type. This method is used by the OGRGeometryFactory class, but not normally called by application code.
This method relates to the SFCOM IWks::ImportFromWKT() method.
This method is the same as the C function OGR_G_ImportFromWkt().
ppszInput  pointer to a pointer to the source text. The pointer is updated to pointer after the consumed text. 
Implements OGRGeometry.

overridevirtual 
Returns TRUE (nonzero) if the object has no points.
Normally this returns FALSE except between when an object is instantiated and points have been assigned.
This method relates to the SFCOM IGeometry::IsEmpty() method.
Implements OGRGeometry.
OGRCompoundCurve & OGRCompoundCurve::operator=  (  const OGRCompoundCurve &  other  ) 
Assignment operator.
Note: before GDAL 2.1, only the default implementation of the operator existed, which could be unsafe to use.

overridevirtual 
Modify the geometry such it has no segment longer then the given distance.
Add intermediate vertices to a geometry.
Interpolated points will have Z and M values (if needed) set to 0. Distance computation is performed in 2d only
This function is the same as the C function OGR_G_Segmentize()
dfMaxLength  the maximum distance between 2 points after segmentization 
This method modifies the geometry to add intermediate vertices if necessary so that the maximum length between 2 consecutive vertices is lower than dfMaxLength.
dfMaxLength  maximum length between 2 consecutive vertices. 
Reimplemented from OGRGeometry.

overridevirtual 
Add or remove the Z coordinate dimension.
This method adds or removes the explicit Z coordinate dimension. Removing the Z coordinate dimension of a geometry will remove any existing Z values. Adding the Z dimension to a geometry collection, a compound curve, a polygon, etc. will affect the children geometries.
bIs3D  Should the geometry have a Z dimension, either TRUE or FALSE. 
Reimplemented from OGRGeometry.

overridevirtual 
Set the coordinate dimension.
This method sets the explicit coordinate dimension. Setting the coordinate dimension of a geometry to 2 should zero out any existing Z values. Setting the dimension of a geometry collection, a compound curve, a polygon, etc. will affect the children geometries. This will also remove the M dimension if present before this call.
nNewDimension  New coordinate dimension value, either 2 or 3. 
Reimplemented from OGRGeometry.

overridevirtual 
Add or remove the M coordinate dimension.
This method adds or removes the explicit M coordinate dimension. Removing the M coordinate dimension of a geometry will remove any existing M values. Adding the M dimension to a geometry collection, a compound curve, a polygon, etc. will affect the children geometries.
bIsMeasured  Should the geometry have a M dimension, either TRUE or FALSE. 
Reimplemented from OGRGeometry.

overridevirtual 
Return the curve start point.
This method relates to the SF COM ICurve::get_StartPoint() method.
poPoint  the point to be assigned the start location. 
Implements OGRCurve.
OGRCurve * OGRCompoundCurve::stealCurve  (  int  iCurve  ) 
"Steal" reference to curve.
iCurve  curve index from 0 to getNumCurves()  1. 

overridevirtual 

overridevirtual 
Apply arbitrary coordinate transformation to geometry.
This method will transform the coordinates of a geometry from their current spatial reference system to a new target spatial reference system. Normally this means reprojecting the vectors, but it could include datum shifts, and changes of units.
Note that this method does not require that the geometry already have a spatial reference system. It will be assumed that they can be treated as having the source spatial reference system of the OGRCoordinateTransformation object, and the actual SRS of the geometry will be ignored. On successful completion the output OGRSpatialReference of the OGRCoordinateTransformation will be assigned to the geometry.
This method is the same as the C function OGR_G_Transform().
poCT  the transformation to apply. 
Implements OGRGeometry.

overridevirtual 
Fetch point at given distance along curve.
This method relates to the SF COM ICurve::get_Value() method.
This function is the same as the C function OGR_G_Value().
dfDistance  distance along the curve at which to sample position. This distance should be between zero and get_Length() for this curve. 
poPoint  the point to be assigned the curve position. 
Implements OGRCurve.

overridevirtual 
Returns size of related binary representation.
This method returns the exact number of bytes required to hold the well known binary representation of this geometry object. Its computation may be slightly expensive for complex geometries.
This method relates to the SFCOM IWks::WkbSize() method.
This method is the same as the C function OGR_G_WkbSize().
Implements OGRGeometry.