GEOS  3.8.0dev
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geos::geomgraph::Label Class Reference

A Label indicates the topological relationship of a component of a topology graph to a given Geometry. This class supports labels for relationships to two Geometrys, which is sufficient for algorithms for binary operations. More...

#include <Label.h>

Public Member Functions

 Label (int onLoc)
 Construct a Label with a single location for both Geometries.
 
 Label (int geomIndex, int onLoc)
 Construct a Label with the location specified for the given Geometry. More...
 
 Label (int onLoc, int leftLoc, int rightLoc)
 Construct a Label with On, Left and Right locations for both Geometries. More...
 
 Label (const Label &l)
 Copy ctor.
 
Labeloperator= (const Label &l)
 
 Label ()
 Initialize both locations to Location::UNDEF. More...
 
 Label (int geomIndex, int onLoc, int leftLoc, int rightLoc)
 Construct a Label with On, Left and Right locations for the given Geometries. Initialize the locations for the other Geometry to Location::UNDEF.
 
void flip ()
 
int getLocation (int geomIndex, int posIndex) const
 
int getLocation (int geomIndex) const
 
void setLocation (int geomIndex, int posIndex, int location)
 
void setLocation (int geomIndex, int location)
 
void setAllLocations (int geomIndex, int location)
 
void setAllLocationsIfNull (int geomIndex, int location)
 
void setAllLocationsIfNull (int location)
 
void merge (const Label &lbl)
 Merge this label with another one. More...
 
int getGeometryCount () const
 
bool isNull () const
 
bool isNull (int geomIndex) const
 
bool isAnyNull (int geomIndex) const
 
bool isArea () const
 
bool isArea (int geomIndex) const
 
bool isLine (int geomIndex) const
 
bool isEqualOnSide (const Label &lbl, int side) const
 
bool allPositionsEqual (int geomIndex, int loc) const
 
void toLine (int geomIndex)
 Converts one GeometryLocation to a Line location.
 
std::string toString () const
 

Static Public Member Functions

static Label toLineLabel (const Label &label)
 Converts a Label to a Line label (that is, one with no side Locations) More...
 

Friends

std::ostream & operator<< (std::ostream &, const Label &)
 

Detailed Description

A Label indicates the topological relationship of a component of a topology graph to a given Geometry. This class supports labels for relationships to two Geometrys, which is sufficient for algorithms for binary operations.

Topology graphs support the concept of labeling nodes and edges in the graph. The label of a node or edge specifies its topological relationship to one or more geometries. (In fact, since JTS operations have only two arguments labels are required for only two geometries). A label for a node or edge has one or two elements, depending on whether the node or edge occurs in one or both of the input Geometrys. Elements contain attributes which categorize the topological location of the node or edge relative to the parent Geometry; that is, whether the node or edge is in the interior, boundary or exterior of the Geometry. Attributes have a value from the set {Interior, Boundary, Exterior}. In a node each element has a single attribute <On>. For an edge each element has a triplet of attributes <Left, On, Right>.

It is up to the client code to associate the 0 and 1 TopologyLocations with specific geometries.

Constructor & Destructor Documentation

geos::geomgraph::Label::Label ( int  geomIndex,
int  onLoc 
)

Construct a Label with the location specified for the given Geometry.

Other geometry location will be set to Location::UNDEF.

geos::geomgraph::Label::Label ( int  onLoc,
int  leftLoc,
int  rightLoc 
)

Construct a Label with On, Left and Right locations for both Geometries.

Initialize the locations for both Geometries to the given values.

geos::geomgraph::Label::Label ( )

Initialize both locations to Location::UNDEF.

isNull() should return true after this kind of construction

Member Function Documentation

void geos::geomgraph::Label::merge ( const Label lbl)

Merge this label with another one.

Merging updates any null attributes of this label with the attributes from lbl

static Label geos::geomgraph::Label::toLineLabel ( const Label label)
static

Converts a Label to a Line label (that is, one with no side Locations)


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