# geos::geom::Geometry Class Reference

Basic implementation of Geometry, constructed and destructed by GeometryFactory. More...

`#include <geos.h>`

Inheritance diagram for geos::geom::Geometry:

List of all members.

## Public Types

typedef std::vector< const Geometry * > | ConstVect
| A vector of const Geometry pointers.
typedef std::vector< Geometry * > | NonConstVect
| A vector of non-const Geometry pointers.
typedef std::auto_ptr< Geometry > | AutoPtr
| An auto_ptr of Geometry.

## Public Member Functions

virtual Geometry * | clone () const =0
| Make a deep-copy of this Geometry.
virtual | ~Geometry ()
| Destroy Geometry and all components.
const GeometryFactory * | getFactory () const
| Gets the factory which contains the context in which this geometry was created.
void | setUserData (void *newUserData)
| A simple scheme for applications to add their own custom data to a Geometry. An example use might be to add an object representing a Coordinate Reference System.
void * | getUserData ()
| Gets the user data object for this geometry, if any.
virtual int | getSRID () const
virtual void | setSRID (int newSRID)
const PrecisionModel * | getPrecisionModel () const
| Get the PrecisionModel used to create this Geometry.
virtual const Coordinate * | getCoordinate () const =0
| Returns a vertex of this Geometry, or NULL if this is the empty geometry.
virtual CoordinateSequence * | getCoordinates () const =0
| Returns this Geometry vertices. Caller takes ownership of the returned object.
virtual size_t | getNumPoints () const =0
| Returns the count of this Geometrys vertices.
virtual bool | isSimple () const =0
| Returns false if the Geometry not simple.
virtual std::string | getGeometryType () const =0
| Return a string representation of this Geometry type.
virtual GeometryTypeId | getGeometryTypeId () const =0
| Return an integer representation of this Geometry type.
virtual size_t | getNumGeometries () const
virtual const Geometry * | getGeometryN (size_t) const
virtual bool | isValid () const
| Tests the validity of this `Geometry`.
virtual bool | isEmpty () const =0
| Returns whether or not the set of points in this Geometry is empty.
virtual Dimension::DimensionType | getDimension () const =0
| Returns the dimension of this Geometry (0=point, 1=line, 2=surface).
virtual Geometry * | getBoundary () const =0
| Returns the boundary as a newly allocated Geometry object.
virtual int | getBoundaryDimension () const =0
| Returns the dimension of this Geometrys inherent boundary.
virtual Geometry * | getEnvelope () const
| Returns this Geometrys bounding box.
virtual const Envelope * | getEnvelopeInternal () const
| Returns the minimum and maximum x and y values in this Geometry, or a null Envelope if this Geometry is empty.
virtual bool | disjoint (const Geometry *other) const
| Returns true if the DE-9IM intersection matrix for the two Geometrys is FF*FF****.
virtual bool | touches (const Geometry *other) const
| Returns true if the DE-9IM intersection matrix for the two Geometrys is FT*******, F**T***** or F***T****.
virtual bool | intersects (const Geometry *g) const
| Returns true if disjoint returns false.
virtual bool | crosses (const Geometry *g) const
| Returns true if the DE-9IM intersection matrix for the two Geometrys is T*T****** (for a point and a curve, a point and an area or a line and an area) 0******** (for two curves).
virtual bool | within (const Geometry *g) const
| Returns true if the DE-9IM intersection matrix for the two Geometrys is T*F**F***.
virtual bool | contains (const Geometry *g) const
| Returns true if other.within(this) returns true.
virtual bool | overlaps (const Geometry *g) const
| Returns true if the DE-9IM intersection matrix for the two Geometrys is T*T***T** (for two points or two surfaces) 1*T***T** (for two curves).
virtual bool | relate (const Geometry *g, const std::string &intersectionPattern) const
| Returns true if the elements in the DE-9IM intersection matrix for the two Geometrys match the elements in intersectionPattern.
bool | relate (const Geometry &g, const std::string &intersectionPattern) const
virtual IntersectionMatrix * | relate (const Geometry *g) const
| Returns the DE-9IM intersection matrix for the two Geometrys.
IntersectionMatrix * | relate (const Geometry &g) const
virtual bool | equals (const Geometry *g) const
| Returns true if the DE-9IM intersection matrix for the two Geometrys is T*F**FFF*.
bool | covers (const Geometry *g) const
| Returns `true` if this geometry covers the specified geometry.
bool | coveredBy (const Geometry *g) const
| Returns `true` if this geometry is covered by the specified geometry.
virtual std::string | toString () const
| Returns the Well-known Text representation of this Geometry.
virtual std::string | toText () const
virtual Geometry * | buffer (double distance) const
| Returns a buffer region around this Geometry having the given width.
virtual Geometry * | buffer (double distance, int quadrantSegments) const
| Returns a buffer region around this Geometry having the given width and with a specified number of segments used to approximate curves.
virtual Geometry * | buffer (double distance, int quadrantSegments, int endCapStyle) const
| Computes a buffer area around this geometry having the given width and with a specified accuracy of approximation for circular arcs, and using a specified end cap style.
virtual Geometry * | convexHull () const
| Returns the smallest convex Polygon that contains all the points in the Geometry.
virtual Geometry * | intersection (const Geometry *other) const
| Returns a Geometry representing the points shared by this Geometry and other.
virtual Geometry * | Union (const Geometry *other) const
| Returns a Geometry representing all the points in this Geometry and other.
virtual Geometry * | difference (const Geometry *other) const
| Returns a Geometry representing the points making up this Geometry that do not make up other.
virtual Geometry * | symDifference (const Geometry *other) const
| Returns a set combining the points in this Geometry not in other, and the points in other not in this Geometry.
virtual bool | equalsExact (const Geometry *other, double tolerance=0) const =0
| Returns true if the two Geometrys are exactly equal, up to a specified tolerance.
virtual void | apply_rw (const CoordinateFilter *filter)=0
virtual void | apply_ro (CoordinateFilter *filter) const =0
virtual void | apply_rw (GeometryFilter *filter)
virtual void | apply_ro (GeometryFilter *filter) const
virtual void | apply_rw (GeometryComponentFilter *filter)
virtual void | apply_ro (GeometryComponentFilter *filter) const
template<class T>
void | applyComponentFilter (T &f) const
| Apply a fiter to each component of this geometry. The filter is expected to provide a .filter(const Geometry*) method.
virtual void | normalize ()=0
| Converts this Geometry to normal form (or canonical form).
virtual int | compareTo (const Geometry *geom) const
virtual double | distance (const Geometry *g) const
| Returns the minimum distance between this Geometry and the Geometry g.
virtual double | getArea () const
| Returns the area of this Geometry.
virtual double | getLength () const
| Returns the length of this Geometry.
virtual bool | isWithinDistance (const Geometry *geom, double cDistance)
| Tests whether the distance from this Geometry to another is less than or equal to a specified value.
virtual Point * | getCentroid () const
| Computes the centroid of this `Geometry`.
virtual bool | getCentroid (Coordinate &ret) const
| Computes the centroid of this Geometry as a Coordinate.
virtual Point * | getInteriorPoint () const
| Computes an interior point of this `Geometry`.
virtual void | geometryChanged ()
void | geometryChangedAction ()
| Notifies this Geometry that its Coordinates have been changed by an external party.

## Protected Member Functions

virtual bool | isEquivalentClass (const Geometry *other) const
| Returns whether the two Geometrys are equal, from the point of view of the equalsExact method.
virtual Envelope::AutoPtr | computeEnvelopeInternal () const =0
virtual int | compareToSameClass (const Geometry *geom) const =0
int | compare (std::vector< Coordinate > a, std::vector< Coordinate > b) const
int | compare (std::vector< Geometry * > a, std::vector< Geometry * > b) const
bool | equal (const Coordinate &a, const Coordinate &b, double tolerance) const
virtual bool | isRectangle () const
| Geometry (const Geometry &geom)
| Geometry (const GeometryFactory *factory)
| Construct a geometry with the given GeometryFactory. Will keep a reference to the factory, so don't delete it until al Geometry objects referring to it are deleted.

## Static Protected Member Functions

static bool | hasNonEmptyElements (const std::vector< Geometry * > *geometries)
| Returns true if the array contains any non-empty Geometrys.
static bool | hasNullElements (const CoordinateSequence *list)
| Returns true if the CoordinateSequence contains any null elements.
static bool | hasNullElements (const std::vector< Geometry * > *lrs)
| Returns true if the vector contains any null elements.
static void | checkNotGeometryCollection (const Geometry *g)

## Protected Attributes

std::auto_ptr< Envelope > | envelope
int | SRID

## Friends

class | GeometryFactory
std::ostream & | operator<< (std::ostream &os, const Geometry &geom)
| Write the Well-known Binary representation of this Geometry as an HEX string to the given output stream.

## Detailed Description

Basic implementation of Geometry, constructed and destructed by GeometryFactory.

`clone` returns a deep copy of the object. Use GeometryFactory to construct.

### Binary Predicates

Because it is not clear at this time what semantics for spatial analysis methods involving `GeometryCollection`s would be useful, `GeometryCollection`s are not supported as arguments to binary predicates (other than `convexHull`) or the `relate` method.

### Set-Theoretic Methods

The spatial analysis methods will return the most specific class possible to represent the result. If the result is homogeneous, a `Point`, `LineString`, or `Polygon` will be returned if the result contains a single element; otherwise, a `MultiPoint`, `MultiLineString`, or `MultiPolygon` will be returned. If the result is heterogeneous a `GeometryCollection` will be returned.

Because it is not clear at this time what semantics for set-theoretic methods involving `GeometryCollection`s would be useful, `GeometryCollections` are not supported as arguments to the set-theoretic methods.

#### Representation of Computed Geometries

The SFS states that the result of a set-theoretic method is the "point-set" result of the usual set-theoretic definition of the operation (SFS 3.2.21.1). However, there are sometimes many ways of representing a point set as a `Geometry`.

The SFS does not specify an unambiguous representation of a given point set returned from a spatial analysis method. One goal of JTS is to make this specification precise and unambiguous. JTS will use a canonical form for `Geometry`s returned from spatial analysis methods. The canonical form is a `Geometry` which is simple and noded:

- Simple means that the Geometry returned will be simple according to the JTS definition of `isSimple`.
- Noded applies only to overlays involving `LineString`s. It means that all intersection points on `LineString`s will be present as endpoints of `LineString`s in the result.

This definition implies that non-simple geometries which are arguments to spatial analysis methods must be subjected to a line-dissolve process to ensure that the results are simple.

#### Constructed Points And The Precision Model

The results computed by the set-theoretic methods may contain constructed points which are not present in the input Geometry. These new points arise from intersections between line segments in the edges of the input Geometry. In the general case it is not possible to represent constructed points exactly. This is due to the fact that the coordinates of an intersection point may contain twice as many bits of precision as the coordinates of the input line segments. In order to represent these constructed points explicitly, JTS must truncate them to fit the PrecisionModel.

Unfortunately, truncating coordinates moves them slightly. Line segments which would not be coincident in the exact result may become coincident in the truncated representation. This in turn leads to "topology collapses" -- situations where a computed element has a lower dimension than it would in the exact result.

When JTS detects topology collapses during the computation of spatial analysis methods, it will throw an exception. If possible the exception will report the location of the collapse.

equals(Object) and hashCode are not overridden, so that when two topologically equal Geometries are added to HashMaps and HashSets, they remain distinct. This behaviour is desired in many cases.

## Member Function Documentation

const GeometryFactory* geos::geom::Geometry::getFactory | ( |  | ) | const`[inline]`

Gets the factory which contains the context in which this geometry was created.

Returns:
  the factory for this geometry

void geos::geom::Geometry::setUserData | ( | void * | newUserData | ) | `[inline]`

A simple scheme for applications to add their own custom data to a Geometry. An example use might be to add an object representing a Coordinate Reference System.

Note that user data objects are not present in geometries created by construction methods.

Parameters:

  | newUserData | an object, the semantics for which are defined by the application using this Geometry

void* geos::geom::Geometry::getUserData | ( |  | ) | `[inline]`

Gets the user data object for this geometry, if any.

Returns:
  the user data object, or `null` if none set

virtual size_t geos::geom::Geometry::getNumGeometries | ( |  | ) | const`[inline, virtual]`

Returns the number of geometries in this collection (or 1 if this is not a collection)

Reimplemented in geos::geom::GeometryCollection.

virtual const Geometry* geos::geom::Geometry::getGeometryN | ( | size_t |  | ) | const`[inline, virtual]`

Returns a pointer to the nth Geometry int this collection (or self if this is not a collection)

Reimplemented in geos::geom::GeometryCollection.

virtual bool geos::geom::Geometry::isValid | ( |  | ) | const`[virtual]`

Tests the validity of this `Geometry`.

Subclasses provide their own definition of "valid".

Returns:
  `true` if this `Geometry` is valid

See also:
  IsValidOp

virtual Geometry* geos::geom::Geometry::getBoundary | ( |  | ) | const`[pure virtual]`

Returns the boundary as a newly allocated Geometry object.

Returned geometry is empty if this Geometry is empty.

Implemented in geos::geom::GeometryCollection, geos::geom::LineString, geos::geom::MultiLineString, geos::geom::MultiPoint, geos::geom::MultiPolygon, geos::geom::Point, and geos::geom::Polygon.

virtual bool geos::geom::Geometry::relate | ( | const Geometry * | g,
|  | const std::string & | intersectionPattern |
| ) |  |  | const`[virtual]`

Returns true if the elements in the DE-9IM intersection matrix for the two Geometrys match the elements in intersectionPattern.

IntersectionPattern elements may be: 0 1 2 T ( = 0, 1 or 2) F ( = -1) * ( = -1, 0, 1 or 2).

For more information on the DE-9IM, see the OpenGIS Simple Features Specification.

Exceptions:

  | util::IllegalArgumentException | if either arg is a collection

bool geos::geom::Geometry::covers | ( | const Geometry * | g | ) | const

Returns `true` if this geometry covers the specified geometry.

The `covers` predicate has the following equivalent definitions:

- Every point of the other geometry is a point of this geometry.
- The DE-9IM Intersection Matrix for the two geometries is `T*****FF*` or `*T****FF*` or `***T**FF*` or `****T*FF*`
- `g.coveredBy(this)` (`covers` is the inverse of `coverdBy`)

Note the difference between `covers` and `contains`

- `covers` is a more inclusive relation. In particular, unlike `contains` it does not distinguish between points in the boundary and in the interior of geometries. For most situations, `covers` should be used in preference to `contains`. As an added benefit, `covers` is more amenable to optimization, and hence should be more performant.

Parameters:

  | g | the `Geometry` with which to compare this `Geometry`

Returns:
  `true` if this `Geometry` covers `g`

See also:
  Geometry::contains

  Geometry::coveredBy

bool geos::geom::Geometry::coveredBy | ( | const Geometry * | g | ) | const`[inline]`

Returns `true` if this geometry is covered by the specified geometry.

- Every point of this geometry is a point of the other geometry.
- The DE-9IM Intersection Matrix for the two geometries is `T*F**F***` or `*TF**F***` or `**FT*F***` or `**F*TF***`
- `g.covers(this)` (`coveredBy` is the inverse of `covers`)

Note the difference between `coveredBy` and `within`

- `coveredBy` is a more inclusive relation.

Parameters:

  | g | the `Geometry` with which to compare this `Geometry`

Returns:
  `true` if this `Geometry` is covered by `g`

See also:
  Geometry::within

  Geometry::covers

virtual Geometry* geos::geom::Geometry::buffer | ( | double | distance | ) | const`[virtual]`

Returns a buffer region around this Geometry having the given width.

Exceptions:

  | util::TopologyException | if a robustness error occurs

virtual Geometry* geos::geom::Geometry::buffer | ( | double | distance,
|  | int | quadrantSegments |
| ) |  |  | const`[virtual]`

Returns a buffer region around this Geometry having the given width and with a specified number of segments used to approximate curves.

Exceptions:

  | util::TopologyException | if a robustness error occurs

virtual Geometry* geos::geom::Geometry::buffer | ( | double | distance,
|  | int | quadrantSegments,
|  | int | endCapStyle |
| ) |  |  | const`[virtual]`

Computes a buffer area around this geometry having the given width and with a specified accuracy of approximation for circular arcs, and using a specified end cap style.

Buffer area boundaries can contain circular arcs. To represent these arcs using linear geometry they must be approximated with line segments.

The `quadrantSegments` argument allows controlling the accuracy of the approximation by specifying the number of line segments used to represent a quadrant of a circle

The end cap style specifies the buffer geometry that will be created at the ends of linestrings. The styles provided are:

- BufferOp::CAP_ROUND - (default) a semi-circle
- BufferOp::CAP_BUTT - a straight line perpendicular to the end segment
- BufferOp::CAP_SQUARE - a half-square

Parameters:

  | distance | the width of the buffer (may be positive, negative or 0)
  | quadrantSegments | the number of line segments used to represent a quadrant of a circle
  | endCapStyle | the end cap style to use

Returns:
  an area geometry representing the buffer region

Exceptions:

  | util::TopologyException | if a robustness error occurs

See also:
  BufferOp

virtual Geometry* geos::geom::Geometry::intersection | ( | const Geometry * | other | ) | const`[virtual]`

Returns a Geometry representing the points shared by this Geometry and other.

Exceptions:

  | util::TopologyException | if a robustness error occurs
  | util::IllegalArgumentException | if either arg is a collection

virtual Geometry* geos::geom::Geometry::Union | ( | const Geometry * | other | ) | const`[virtual]`

Returns a Geometry representing all the points in this Geometry and other.

Exceptions:

  | util::TopologyException | if a robustness error occurs
  | util::IllegalArgumentException | if either arg is a collection

virtual Geometry* geos::geom::Geometry::difference | ( | const Geometry * | other | ) | const`[virtual]`

Returns a Geometry representing the points making up this Geometry that do not make up other.

Exceptions:

  | util::TopologyException | if a robustness error occurs
  | util::IllegalArgumentException | if either arg is a collection

virtual Geometry* geos::geom::Geometry::symDifference | ( | const Geometry * | other | ) | const`[virtual]`

Returns a set combining the points in this Geometry not in other, and the points in other not in this Geometry.

Exceptions:

  | util::TopologyException | if a robustness error occurs
  | util::IllegalArgumentException | if either arg is a collection

template<class T>

void geos::geom::Geometry::applyComponentFilter | ( | T & | f | ) | const`[inline]`

Apply a fiter to each component of this geometry. The filter is expected to provide a .filter(const Geometry*) method.

I intend similar templated methods to replace all the virtual apply_rw and apply_ro functions... --strk(2005-02-06);

virtual Point* geos::geom::Geometry::getCentroid | ( |  | ) | const`[virtual]`

Computes the centroid of this `Geometry`.

The centroid is equal to the centroid of the set of component Geometrys of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid)

Returns:
  a Point which is the centroid of this Geometry

virtual bool geos::geom::Geometry::getCentroid | ( | Coordinate & | ret | ) | const`[virtual]`

Computes the centroid of this Geometry as a Coordinate.

Returns false if centroid cannot be computed (EMPTY geometry)

virtual Point* geos::geom::Geometry::getInteriorPoint | ( |  | ) | const`[virtual]`

Computes an interior point of this `Geometry`.

An interior point is guaranteed to lie in the interior of the Geometry, if it possible to calculate such a point exactly. Otherwise, the point may lie on the boundary of the geometry.

Returns:
  a Point which is in the interior of this Geometry, or null if the geometry doesn't have an interior (empty)

virtual bool geos::geom::Geometry::isRectangle | ( |  | ) | const`[inline, protected, virtual]`

Deprecated:

Deprecated:

Polygon overrides to check for actual rectangle

Reimplemented in geos::geom::Polygon.

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

- Geometry.h