# OGRGeometryCollection Class Reference

`#include <ogr_geometry.h>`

Inheritance diagram for OGRGeometryCollection:

List of all members.

## Public Member Functions
| OGRGeometryCollection ()
| Create an empty geometry collection.
virtual const char * | getGeometryName () const
| Fetch WKT name for geometry type.
virtual OGRwkbGeometryType | getGeometryType () const
| Fetch geometry type.
virtual OGRGeometry * | clone () const
| Make a copy of this object.
virtual void | empty ()
| Clear geometry information. This restores the geometry to it's initial state after construction, and before assignment of actual geometry.
virtual OGRErr | transform (OGRCoordinateTransformation *poCT)
| Apply arbitrary coordinate transformation to geometry.
virtual void | flattenTo2D ()
| Convert geometry to strictly 2D. In a sense this converts all Z coordinates to 0.0.
virtual OGRBoolean | IsEmpty () const
| Returns TRUE (non-zero) if the object has no points.
virtual void | segmentize (double dfMaxLength)
| Modify the geometry such it has no segment longer then the given distance.
virtual int | WkbSize () const
| Returns size of related binary representation.
virtual OGRErr | importFromWkb (unsigned char *, int=-1)
| Assign geometry from well known binary data.
virtual OGRErr | exportToWkb (OGRwkbByteOrder, unsigned char *) const
| Convert a geometry into well known binary format.
virtual OGRErr | importFromWkt (char **)
| Assign geometry from well known text data.
virtual OGRErr | exportToWkt (char **ppszDstText) const
| Convert a geometry into well known text format.
virtual double | get_Length () const
| Compute the length of a multicurve.
virtual double | get_Area () const
| Compute area of geometry collection.
virtual int | getDimension () const
| Get the dimension of this object.
virtual void | getEnvelope (OGREnvelope *psEnvelope) const
| Computes and returns the bounding envelope for this geometry in the passed psEnvelope structure.
virtual void | getEnvelope (OGREnvelope3D *psEnvelope) const
| Computes and returns the bounding envelope (3D) for this geometry in the passed psEnvelope structure.
int | getNumGeometries () const
| Fetch number of geometries in container.
OGRGeometry * | getGeometryRef (int)
| Fetch geometry from container.
virtual OGRBoolean | Equals (OGRGeometry *) const
| Returns TRUE if two geometries are equivalent.
virtual void | setCoordinateDimension (int nDimension)
| Set the coordinate dimension.
virtual OGRErr | addGeometry (const OGRGeometry *)
| Add a geometry to the container.
virtual OGRErr | addGeometryDirectly (OGRGeometry *)
| Add a geometry directly to the container.
virtual OGRErr | removeGeometry (int iIndex, int bDelete=TRUE)
| Remove a geometry from the container.
void | closeRings ()
| Force rings to be closed.
virtual void | swapXY ()
| Swap x and y coordinates.

## Detailed Description

A collection of 1 or more geometry objects.

All geometries must share a common spatial reference system, and Subclasses may impose additional restrictions on the contents.

## Member Function Documentation

const char * OGRGeometryCollection::getGeometryName | ( |  | ) | const`[virtual]`

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().

Returns:
  name used for this geometry type in well known text format. The returned pointer is to a static internal string and should not be modified or freed.

Implements OGRGeometry.

Reimplemented in OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

Referenced by exportToWkt(), and get_Area().

OGRwkbGeometryType OGRGeometryCollection::getGeometryType | ( |  | ) | const`[virtual]`

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().

Returns:
  the geometry type code.

Implements OGRGeometry.

Reimplemented in OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

References OGRGeometry::getCoordinateDimension(), wkbGeometryCollection, and wkbGeometryCollection25D.

Referenced by closeRings(), Equals(), and exportToWkb().

OGRGeometry * OGRGeometryCollection::clone | ( |  | ) | const`[virtual]`

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().

Returns:
  a new object instance with the same geometry, and spatial reference system as the original.

Implements OGRGeometry.

Reimplemented in OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

References addGeometry(), OGRGeometry::assignSpatialReference(), and OGRGeometry::getSpatialReference().

void OGRGeometryCollection::empty | ( |  | ) | `[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().

Implements OGRGeometry.

Referenced by OGRMultiPolygon::importFromWkt(), OGRMultiPoint::importFromWkt(), and OGRMultiLineString::importFromWkt().

OGRErr OGRGeometryCollection::transform | ( | OGRCoordinateTransformation * | poCT | ) | `[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.

Implements OGRGeometry.

References OGRGeometry::assignSpatialReference(), OGRCoordinateTransformation::GetTargetCS(), and OGRGeometry::transform().

void OGRGeometryCollection::flattenTo2D | ( |  | ) | `[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().

Implements OGRGeometry.

OGRBoolean OGRGeometryCollection::IsEmpty | ( |  | ) | const`[virtual]`

Returns TRUE (non-zero) 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.

Returns:
  TRUE if object is empty, otherwise FALSE.

Implements OGRGeometry.

Referenced by OGRMultiPoint::exportToWkt(), and getEnvelope().

void OGRGeometryCollection::segmentize | ( | double | dfMaxLength | ) | `[virtual]`

Modify the geometry such it has no segment longer then the given distance.

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()

Parameters:

  | dfMaxLength | the maximum distance between 2 points after segmentization

Reimplemented from OGRGeometry.

int OGRGeometryCollection::WkbSize | ( |  | ) | const`[virtual]`

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().

Returns:
  size of binary representation in bytes.

Implements OGRGeometry.

References OGRGeometry::WkbSize().

OGRErr OGRGeometryCollection::importFromWkb | ( | unsigned char * | pabyData,
|  | int | nSize = `-1` |
| ) |  |  | `[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.

Implements OGRGeometry.

OGRErr OGRGeometryCollection::exportToWkb | ( | OGRwkbByteOrder | eByteOrder,
|  | unsigned char * | pabyData |
| ) |  |  | const`[virtual]`

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().

Parameters:

  | 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.

Returns:
  Currently OGRERR_NONE is always returned.

Implements OGRGeometry.

References OGRGeometry::exportToWkb(), getGeometryType(), and OGRGeometry::WkbSize().

OGRErr OGRGeometryCollection::importFromWkt | ( | char ** | ppszInput | ) | `[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.

Implements OGRGeometry.

Reimplemented in OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

OGRErr OGRGeometryCollection::exportToWkt | ( | char ** | ppszDstText | ) | const`[virtual]`

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().

Parameters:

  | ppszDstText | a text buffer is allocated by the program, and assigned to the passed pointer.

Returns:
  Currently OGRERR_NONE is always returned.

Implements OGRGeometry.

Reimplemented in OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

References OGRGeometry::exportToWkt(), getGeometryName(), and getNumGeometries().

double OGRGeometryCollection::get_Length | ( |  | ) | const`[virtual]`

Compute the length of a multicurve.

The length is computed as the sum of the length of all members in this collection.

Note:
  No warning will be issued if a member of the collection does not support the get_Length method.

Returns:
  computed area.

References OGRGeometry::getGeometryType(), wkbGeometryCollection, wkbLinearRing, and wkbLineString.

double OGRGeometryCollection::get_Area | ( |  | ) | const`[virtual]`

Compute area of geometry collection.

The area is computed as the sum of the areas of all members in this collection.

Note:
  No warning will be issued if a member of the collection does not support the get_Area method.

Returns:
  computed area.

Reimplemented in OGRMultiPolygon.

References getGeometryName(), OGRGeometry::getGeometryType(), wkbGeometryCollection, wkbLinearRing, wkbLineString, wkbMultiPolygon, and wkbPolygon.

int OGRGeometryCollection::getDimension | ( |  | ) | const`[virtual]`

Get the dimension of this object.

This method corresponds to the SFCOM IGeometry::GetDimension() method. It indicates the dimension of the object, but does not indicate the dimension of the underlying space (as indicated by OGRGeometry::getCoordinateDimension()).

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

Returns:
  0 for points, 1 for lines and 2 for surfaces.

Implements OGRGeometry.

void OGRGeometryCollection::getEnvelope | ( | OGREnvelope * | psEnvelope | ) | const`[virtual]`

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().

Parameters:

  | psEnvelope | the structure in which to place the results.

Implements OGRGeometry.

References OGRGeometry::getEnvelope(), IsEmpty(), OGREnvelope::MaxX, OGREnvelope::MaxY, OGREnvelope::MinX, and OGREnvelope::MinY.

void OGRGeometryCollection::getEnvelope | ( | OGREnvelope3D * | psEnvelope | ) | const`[virtual]`

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().

Parameters:

  | psEnvelope | the structure in which to place the results.

Since:
  OGR 1.9.0

Implements OGRGeometry.

References OGRGeometry::getEnvelope(), IsEmpty(), OGREnvelope::MaxX, OGREnvelope::MaxY, OGREnvelope3D::MaxZ, OGREnvelope::MinX, OGREnvelope::MinY, and OGREnvelope3D::MinZ.

int OGRGeometryCollection::getNumGeometries | ( |  | ) | const

Fetch number of geometries in container.

This method relates to the SFCOM IGeometryCollect::get_NumGeometries() method.

Returns:
  count of children geometries. May be zero.

Referenced by OGRMultiPolygon::clone(), OGRMultiPoint::clone(), OGRMultiLineString::clone(), OGRGeometry::dumpReadable(), Equals(), OGRMultiPolygon::exportToWkt(), OGRMultiPoint::exportToWkt(), OGRMultiLineString::exportToWkt(), exportToWkt(), OGRGeometryFactory::forceToMultiLineString(), OGRGeometryFactory::forceToMultiPoint(), OGRGeometryFactory::forceToMultiPolygon(), OGRGeometryFactory::forceToPolygon(), OGRMultiPolygon::get_Area(), OGRBuildPolygonFromEdges(), and OGRGeometry::Polygonize().

OGRGeometry * OGRGeometryCollection::getGeometryRef | ( | int | i | ) |

Fetch geometry from container.

This method returns a pointer to an geometry within the container. The returned geometry remains owned by the container, and should not be modified. The pointer is only valid untill the next change to the geometry container. Use IGeometry::clone() to make a copy.

This method relates to the SFCOM IGeometryCollection::get_Geometry() method.

Parameters:

  | i | the index of the geometry to fetch, between 0 and getNumGeometries() - 1.

Returns:
  pointer to requested geometry.

Referenced by OGRMultiPolygon::clone(), OGRMultiPoint::clone(), OGRMultiLineString::clone(), OGRGeometry::dumpReadable(), Equals(), OGRMultiPolygon::exportToWkt(), OGRMultiPoint::exportToWkt(), OGRMultiLineString::exportToWkt(), OGRGeometryFactory::forceToMultiLineString(), OGRGeometryFactory::forceToMultiPoint(), OGRGeometryFactory::forceToMultiPolygon(), OGRGeometryFactory::forceToPolygon(), OGRMultiPolygon::get_Area(), OGRBuildPolygonFromEdges(), and OGRGeometry::Polygonize().

OGRBoolean OGRGeometryCollection::Equals | ( | OGRGeometry * | poOtherGeom | ) | const`[virtual]`

Returns TRUE if two geometries are equivalent.

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

Returns:
  TRUE if equivalent or FALSE otherwise.

Implements OGRGeometry.

References OGRGeometry::Equals(), getGeometryRef(), getGeometryType(), OGRGeometry::getGeometryType(), and getNumGeometries().

void OGRGeometryCollection::setCoordinateDimension | ( | int | nNewDimension | ) | `[virtual]`

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 will not necessarily affect the children geometries.

Parameters:

  | nNewDimension | New coordinate dimension value, either 2 or 3.

Reimplemented from OGRGeometry.

References OGRGeometry::setCoordinateDimension().

OGRErr OGRGeometryCollection::addGeometry | ( | const OGRGeometry * | poNewGeom | ) | `[virtual]`

Add a geometry to the container.

Some subclasses of OGRGeometryCollection restrict the types of geometry that can be added, and may return an error. The passed geometry is cloned to make an internal copy.

There is no SFCOM analog to this method.

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

Parameters:

  | poNewGeom | geometry to add to the container.

Returns:
  OGRERR_NONE if successful, or OGRERR_UNSUPPORTED_GEOMETRY_TYPE if the geometry type is illegal for the type of geometry container.

References addGeometryDirectly(), and OGRGeometry::clone().

Referenced by OGRMultiPolygon::clone(), OGRMultiPoint::clone(), OGRMultiLineString::clone(), and clone().

OGRErr OGRGeometryCollection::addGeometryDirectly | ( | OGRGeometry * | poNewGeom | ) | `[virtual]`

Add a geometry directly to the container.

Some subclasses of OGRGeometryCollection restrict the types of geometry that can be added, and may return an error. Ownership of the passed geometry is taken by the container rather than cloning as addGeometry() does.

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

There is no SFCOM analog to this method.

Parameters:

  | poNewGeom | geometry to add to the container.

Returns:
  OGRERR_NONE if successful, or OGRERR_UNSUPPORTED_GEOMETRY_TYPE if the geometry type is illegal for the type of geometry container.

Reimplemented in OGRMultiPolygon, OGRMultiPoint, and OGRMultiLineString.

References OGRGeometry::getCoordinateDimension().

Referenced by addGeometry(), OGRMultiPolygon::addGeometryDirectly(), OGRMultiPoint::addGeometryDirectly(), and OGRMultiLineString::addGeometryDirectly().

OGRErr OGRGeometryCollection::removeGeometry | ( | int | iGeom,
|  | int | bDelete = `TRUE` |
| ) |  |  | `[virtual]`

Remove a geometry from the container.

Removing a geometry will cause the geometry count to drop by one, and all "higher" geometries will shuffle down one in index.

There is no SFCOM analog to this method.

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

Parameters:

  | iGeom | the index of the geometry to delete. A value of -1 is a special flag meaning that all geometries should be removed.
  | bDelete | if TRUE the geometry will be deallocated, otherwise it will not. The default is TRUE as the container is considered to own the geometries in it.

Returns:
  OGRERR_NONE if successful, or OGRERR_FAILURE if the index is out of range.

Referenced by OGRGeometryFactory::forceToMultiLineString(), OGRGeometryFactory::forceToMultiPoint(), and OGRGeometryFactory::forceToMultiPolygon().

void OGRGeometryCollection::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 from OGRGeometry.

References getGeometryType(), and wkbPolygon.

void OGRGeometryCollection::swapXY | ( |  | ) | `[virtual]`

Swap x and y coordinates.

Since:
  OGR 1.8.0

Reimplemented from OGRGeometry.

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

- ogr_geometry.h
- ogrgeometrycollection.cpp

Generated for GDAL by 1.5.6.