geos::algorithm::RayCrossingCounter Class Reference

Counts the number of segments crossed by a horizontal ray extending to the right from a given point, in an incremental fashion. More...

#include <RayCrossingCounter.h>

Collaboration diagram for geos::algorithm::RayCrossingCounter:

Public Member Functions
	RayCrossingCounter (const geom::Coordinate &p_point)
void	countSegment (const geom::Coordinate &p1, const geom::Coordinate &p2)
	Counts a segment. More...
bool	isOnSegment ()
	Reports whether the point lies exactly on one of the supplied segments. More...
geom::Location	getLocation ()
	Gets the Location of the point relative to the ring, polygon or multipolygon from which the processed segments were provided. More...
bool	isPointInPolygon ()
	Tests whether the point lies in or on the ring, polygon or multipolygon from which the processed segments were provided. More...

Static Public Member Functions
static geom::Location	locatePointInRing (const geom::Coordinate &p, const geom::CoordinateSequence &ring)
	Determines the Location of a point in a ring. More...
static geom::Location	locatePointInRing (const geom::Coordinate &p, const std::vector< const geom::Coordinate * > &ring)
	Semantically equal to the above, just different args encoding. More...

Private Member Functions
	RayCrossingCounter (const RayCrossingCounter &other)=delete
RayCrossingCounter &	operator= (const RayCrossingCounter &rhs)=delete

Private Attributes
const geom::Coordinate &	point
int	crossingCount
bool	isPointOnSegment

Detailed Description

Counts the number of segments crossed by a horizontal ray extending to the right from a given point, in an incremental fashion.

This can be used to determine whether a point lies in a polygonal geometry. The class determines the situation where the point lies exactly on a segment. When being used for Point-In-Polygon determination, this case allows short-circuiting the evaluation.

This class handles polygonal geometries with any number of shells and holes. The orientation of the shell and hole rings is unimportant. In order to compute a correct location for a given polygonal geometry, it is essential that all segments are counted which

• touch the ray
• lie in in any ring which may contain the point

The only exception is when the point-on-segment situation is detected, in which case no further processing is required. The implication of the above rule is that segments which can be a priori determined to not touch the ray (i.e. by a test of their bounding box or Y-extent) do not need to be counted. This allows for optimization by indexing.

Author

Martin Davis

Definition at line 65 of file RayCrossingCounter.h.

Constructor & Destructor Documentation

geos::algorithm::RayCrossingCounter::RayCrossingCounter ( const RayCrossingCounter &  other )

privatedelete

geos::algorithm::RayCrossingCounter::RayCrossingCounter ( const geom::Coordinate &  p_point )

inline

Definition at line 95 of file RayCrossingCounter.h.

Member Function Documentation

void geos::algorithm::RayCrossingCounter::countSegment	(	const geom::Coordinate &	p1,
		const geom::Coordinate &	p2
	)

Counts a segment.

Parameters

p1	an endpoint of the segment
p2	another endpoint of the segment

geom::Location geos::algorithm::RayCrossingCounter::getLocation

(

)

Gets the Location of the point relative to the ring, polygon or multipolygon from which the processed segments were provided.

This method only determines the correct location if all relevant segments must have been processed.

Returns

the Location of the point

bool geos::algorithm::RayCrossingCounter::isOnSegment ( )

inline

Reports whether the point lies exactly on one of the supplied segments.

This method may be called at any time as segments are processed. If the result of this method is true, no further segments need be supplied, since the result will never change again.

Returns

true if the point lies exactly on a segment

Definition at line 120 of file RayCrossingCounter.h.

bool geos::algorithm::RayCrossingCounter::isPointInPolygon

(

)

Tests whether the point lies in or on the ring, polygon or multipolygon from which the processed segments were provided.

This method only determines the correct location if all relevant segments must have been processed.

Returns

true if the point lies in or on the supplied polygon

static geom::Location geos::algorithm::RayCrossingCounter::locatePointInRing ( const geom::Coordinate &  p, const geom::CoordinateSequence &  ring  )

static

Determines the Location of a point in a ring.

This method is an exemplar of how to use this class.

Parameters

p	the point to test
ring	an array of Coordinates forming a ring

Returns

the location of the point in the ring

static geom::Location geos::algorithm::RayCrossingCounter::locatePointInRing ( const geom::Coordinate &  p, const std::vector< const geom::Coordinate * > &  ring  )

static

Semantically equal to the above, just different args encoding.

RayCrossingCounter& geos::algorithm::RayCrossingCounter::operator= ( const RayCrossingCounter &  rhs )

privatedelete

Member Data Documentation

int geos::algorithm::RayCrossingCounter::crossingCount

private

Definition at line 69 of file RayCrossingCounter.h.

bool geos::algorithm::RayCrossingCounter::isPointOnSegment

private

Definition at line 72 of file RayCrossingCounter.h.

const geom::Coordinate& geos::algorithm::RayCrossingCounter::point

private

Definition at line 67 of file RayCrossingCounter.h.

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

• RayCrossingCounter.h