OGRGeometry Class Reference

#include <ogr_geometry.h>

Inheritance diagram for OGRGeometry:

OGRCurve OGRGeometryCollection OGRPoint OGRSurface OGRLineString OGRMultiLineString OGRMultiPoint OGRMultiPolygon OGRPolygon OGRLinearRing List of all members.

Public Member Functions

virtual void empty ()=0
virtual OGRErr importFromWkb (unsigned char *, int=-1)=0
virtual OGRErr importFromWkt (char **ppszInput)=0
virtual void dumpReadable (FILE *, const char *=NULL)
virtual void flattenTo2D ()=0
virtual char * exportToGML () const
virtual void closeRings ()
void assignSpatialReference (OGRSpatialReference *poSR)
OGRSpatialReferencegetSpatialReference (void) const
virtual OGRErr transform (OGRCoordinateTransformation *poCT)=0
OGRErr transformTo (OGRSpatialReference *poSR)
virtual OGRBoolean Intersects (OGRGeometry *) const
virtual OGRBoolean Equals (OGRGeometry *) const =0
virtual OGRBoolean Disjoint (const OGRGeometry *) const
virtual OGRBoolean Touches (const OGRGeometry *) const
virtual OGRBoolean Crosses (const OGRGeometry *) const
virtual OGRBoolean Within (const OGRGeometry *) const
virtual OGRBoolean Contains (const OGRGeometry *) const
virtual OGRBoolean Overlaps (const OGRGeometry *) const
virtual OGRGeometrygetBoundary () const
virtual double Distance (const OGRGeometry *) const
virtual OGRGeometryConvexHull () const
virtual OGRGeometryBuffer (double dfDist, int nQuadSegs=30) const
virtual OGRGeometryIntersection (const OGRGeometry *) const
virtual OGRGeometryUnion (const OGRGeometry *) const
virtual OGRGeometryDifference (const OGRGeometry *) const
virtual OGRGeometrySymmetricDifference (const OGRGeometry *) const

Detailed Description

Abstract base class for all geometry classes.

Note that the family of spatial analysis methods (Equal(), Disjoint(), ..., ConvexHull(), Buffer(), ...) are not implemented at ths time. Some other required and optional geometry methods have also been omitted at this time.


Member Function Documentation

void OGRGeometry::assignSpatialReference OGRSpatialReference poSR  ) 
 

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.

This is similar to the SFCOM IGeometry::put_SpatialReference() method.

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

Parameters:
poSR new spatial reference system to apply.

OGRGeometry * OGRGeometry::Buffer double  dfDist,
int  nQuadSegs = 30
const [virtual]
 

Compute buffer of geometry.

Builds a new geometry containing the buffer region around the geometry on which it is invoked. The buffer is a polygon containing the region within the buffer distance of the original geometry.

Some buffer sections are properly described as curves, but are converted to approximate polygons. The nQuadSegs parameter can be used to control how many segements should be used to define a 90 degree curve - a quadrant of a circle. A value of 30 is a reasonable default. Large values result in large numbers of vertices in the resulting buffer geometry while small numbers reduce the accuracy of the result.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
dfDist the buffer distance to be applied.
nQuadSegs the number of segments used to approximate a 90 degree (quadrant) of curvature.
Returns:
the newly created geometry, or NULL if an error occurs.

void OGRGeometry::closeRings  )  [virtual]
 

Force rings to be closed.

If this geometry, or any contained geometries has polygon rings that are not closed, they will be closed by adding the starting point at the end.

Reimplemented in OGRLinearRing, OGRPolygon, and OGRGeometryCollection.

OGRBoolean OGRGeometry::Contains const OGRGeometry poOtherGeom  )  const [virtual]
 

Test for containment.

Tests if the passed in geometry contains the target geometry.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the geometry to compare to this geometry.
Returns:
TRUE if poOtherGeom contains this geometry, otherwise FALSE.

OGRGeometry * OGRGeometry::ConvexHull  )  const [virtual]
 

Compute convex hull.

A new geometry object is created and returned containing the convex hull of the geometry on which the method is invoked.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Returns:
a newly allocated geometry now owned by the caller, or NULL on failure.

OGRBoolean OGRGeometry::Crosses const OGRGeometry poOtherGeom  )  const [virtual]
 

Test for crossing.

Tests if this geometry and the other passed into the method are crossing.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the geometry to compare to this geometry.
Returns:
TRUE if they are crossing, otherwise FALSE.

OGRGeometry * OGRGeometry::Difference const OGRGeometry poOtherGeom  )  const [virtual]
 

Compute difference.

Generates a new geometry which is the region of this geometry with the region of the second geometry removed.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the other geometry removed from "this" geometry.
Returns:
a new geometry representing the difference or NULL if the difference is empty or an error occurs.

OGRBoolean OGRGeometry::Disjoint const OGRGeometry poOtherGeom  )  const [virtual]
 

Test for disjointness.

Tests if this geometry and the other passed into the method are disjoint.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the geometry to compare to this geometry.
Returns:
TRUE if they are disjoint, otherwise FALSE.

double OGRGeometry::Distance const OGRGeometry poOtherGeom  )  const [virtual]
 

Compute distance between two geometries.

Returns the shortest distance between the two geometries.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the other geometry to compare against.
Returns:
the distance between the geometries or -1 if an error occurs.

void OGRGeometry::dumpReadable FILE *  fp,
const char *  pszPrefix = NULL
[virtual]
 

Dump geometry in well known text format to indicated output file.

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

Parameters:
fp the text file to write the geometry to.
pszPrefix the prefix to put on each line of output.

void OGRGeometry::empty  )  [pure virtual]
 

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().

Implemented in OGRPoint, OGRLineString, OGRPolygon, and OGRGeometryCollection.

int OGRGeometry::Equals OGRGeometry poOtherGeom  )  const [pure virtual]
 

Returns two if two geometries are equivalent.

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

Returns:
TRUE if equivalent or FALSE otherwise.

Implemented in OGRPoint, OGRLineString, OGRPolygon, and OGRGeometryCollection.

char * OGRGeometry::exportToGML  )  const [virtual]
 

Convert a geometry into GML format.

The GML geometry is expressed directly in terms of GML basic data types assuming the this is available in the gml namespace. The returned string should be freed with CPLFree() when no longer required.

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

Returns:
A GML fragment or NULL in case of error.

void OGRGeometry::flattenTo2D  )  [pure virtual]
 

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().

Implemented in OGRPoint, OGRLineString, OGRPolygon, and OGRGeometryCollection.

OGRGeometry * OGRGeometry::getBoundary  )  const [virtual]
 

Compute boundary.

A new geometry object is created and returned containing the boundary of the geometry on which the method is invoked.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Returns:
a newly allocated geometry now owned by the caller, or NULL on failure.

OGRSpatialReference * OGRGeometry::getSpatialReference void   )  const [inline]
 

Returns spatial reference system for object.

This method relates to the SFCOM IGeometry::get_SpatialReference() method.

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

Returns:
a reference to the spatial reference object. The object may be shared with many geometry objects, and should not be modified.

OGRErr OGRGeometry::importFromWkb unsigned char *  pabyData,
int  nSize = -1
[pure virtual]
 

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().

Parameters:
pabyData the binary input data.
nSize the size of pabyData in bytes, or zero if not known.
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.

Implemented in OGRPoint, OGRLineString, OGRLinearRing, OGRPolygon, and OGRGeometryCollection.

OGRErr OGRGeometry::importFromWkt char **  ppszInput  )  [pure virtual]
 

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().

Parameters:
ppszInput pointer to a pointer to the source text. The pointer is updated to pointer after the consumed text.
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.

Implemented in OGRPoint, OGRLineString, OGRPolygon, OGRGeometryCollection, OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

OGRGeometry * OGRGeometry::Intersection const OGRGeometry poOtherGeom  )  const [virtual]
 

Compute intersection.

Generates a new geometry which is the region of intersection of the two geometries operated on. The Intersect() method can be used to test if two geometries intersect.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the other geometry intersected with "this" geometry.
Returns:
a new geometry representing the intersection or NULL if there is no intersection or an error occurs.

OGRBoolean OGRGeometry::Intersects OGRGeometry poOtherGeom  )  const [virtual]
 

Do these features intersect?

Determines whether two geometries intersect. If GEOS is enabled, then this is done in rigerous fashion otherwise TRUE is returned if the envelopes (bounding boxes) of the two features overlap.

The poOtherGeom argument may be safely NULL, but in this case the method will always return TRUE. That is, a NULL geometry is treated as being everywhere.

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

Parameters:
poOtherGeom the other geometry to test against.
Returns:
TRUE if the geometries intersect, otherwise FALSE.

OGRBoolean OGRGeometry::Overlaps const OGRGeometry poOtherGeom  )  const [virtual]
 

Test for overlap.

Tests if this geometry and the other passed into the method overlap, that is their intersection has a non-zero area.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the geometry to compare to this geometry.
Returns:
TRUE if they are overlapping, otherwise FALSE.

OGRGeometry * OGRGeometry::SymmetricDifference const OGRGeometry poOtherGeom  )  const [virtual]
 

Compute symmetric difference.

Generates a new geometry which is the symmetric difference of this geometry and the second geometry passed into the method.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the other geometry.
Returns:
a new geometry representing the symmetric difference or NULL if the difference is empty or an error occurs.

OGRBoolean OGRGeometry::Touches const OGRGeometry poOtherGeom  )  const [virtual]
 

Test for touching.

Tests if this geometry and the other passed into the method are touching.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the geometry to compare to this geometry.
Returns:
TRUE if they are touching, otherwise FALSE.

OGRErr OGRGeometry::transform OGRCoordinateTransformation poCT  )  [pure virtual]
 

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().

Parameters:
poCT the transformation to apply.
Returns:
OGRERR_NONE on success or an error code.

Implemented in OGRPoint, OGRLineString, OGRPolygon, and OGRGeometryCollection.

OGRErr OGRGeometry::transformTo OGRSpatialReference poSR  ) 
 

Transform geometry to new spatial reference system.

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.

This method will only work if the geometry already has an assigned spatial reference system, and if it is transformable to the target coordinate system.

Because this method requires internal creation and initialization of an OGRCoordinateTransformation object it is significantly more expensive to use this method to transform many geometries than it is to create the OGRCoordinateTransformation in advance, and call transform() with that transformation. This method exists primarily for convenience when only transforming a single geometry.

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

Parameters:
poSR spatial reference system to transform to.
Returns:
OGRERR_NONE on success, or an error code.

OGRGeometry * OGRGeometry::Union const OGRGeometry poOtherGeom  )  const [virtual]
 

Compute union.

Generates a new geometry which is the region of union of the two geometries operated on.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the other geometry unioned with "this" geometry.
Returns:
a new geometry representing the union or NULL if an error occurs.

OGRBoolean OGRGeometry::Within const OGRGeometry poOtherGeom  )  const [virtual]
 

Test for containment.

Tests if the passed in geometry is within the target geometry.

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

This method is built on the GEOS library, check it for the definition of the geometry operation. If OGR is built without the GEOS library, this method will always fail, issuing a CPLE_NotSupported error.

Parameters:
poOtherGeom the geometry to compare to this geometry.
Returns:
TRUE if poOtherGeom is within this geometry, otherwise FALSE.


The documentation for this class was generated from the following files:
Generated on Mon Jan 9 18:03:32 2006 for OGR by  doxygen 1.4.6