Does vector analysis using the geos library and handles import, export, exception handling*. More...

#include <qgsgeos.h>

Inheritance diagram for QgsGeos:

Public Member Functions
	QgsGeos (const QgsAbstractGeometry *geometry, double precision=0)
	GEOS geometry engine constructor. More...

double	area (QString *errorMsg=nullptr) const override

QgsAbstractGeometry *	buffer (double distance, int segments, Qgis::EndCapStyle endCapStyle, Qgis::JoinStyle joinStyle, double miterLimit, QString *errorMsg=nullptr) const override
	Buffers a geometry. More...

QgsAbstractGeometry *	buffer (double distance, int segments, QString *errorMsg=nullptr) const override

QgsPoint *	centroid (QString *errorMsg=nullptr) const override
	Calculates the centroid of this. More...

std::unique_ptr< QgsAbstractGeometry >	clip (const QgsRectangle &rectangle, QString *errorMsg=nullptr) const
	Performs a fast, non-robust intersection between the geometry and a rectangle. More...

QgsGeometry	closestPoint (const QgsGeometry &other, QString *errorMsg=nullptr) const
	Returns the closest point on the geometry to the other geometry. More...

QgsAbstractGeometry *	combine (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Calculate the combination of this and geom. More...

QgsAbstractGeometry *	combine (const QVector< QgsAbstractGeometry * > &geomList, QString *errorMsg) const override
	Calculate the combination of this and geometries. More...

QgsAbstractGeometry *	combine (const QVector< QgsGeometry > &, QString *errorMsg=nullptr) const override
	Calculate the combination of this and geometries. More...

bool	contains (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom contains this. More...

QgsAbstractGeometry *	convexHull (QString *errorMsg=nullptr) const override
	Calculate the convex hull of this. More...

bool	crosses (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom crosses this. More...

QgsGeometry	delaunayTriangulation (double tolerance=0.0, bool edgesOnly=false, QString *errorMsg=nullptr) const
	Returns the Delaunay triangulation for the vertices of the geometry. More...

QgsAbstractGeometry *	difference (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Calculate the difference of this and geom. More...

bool	disjoint (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom is disjoint from this. More...

double	distance (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Calculates the distance between this and geom. More...

bool	distanceWithin (const QgsAbstractGeometry geom, double maxdistance, QString errorMsg=nullptr) const override
	Checks if geom is within maxdistance distance from this geometry. More...

QgsAbstractGeometry *	envelope (QString *errorMsg=nullptr) const override

double	frechetDistance (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const
	Returns the Fréchet distance between this geometry and geom, restricted to discrete points for both geometries. More...

double	frechetDistanceDensify (const QgsAbstractGeometry geom, double densifyFraction, QString errorMsg=nullptr) const
	Returns the Fréchet distance between this geometry and geom, restricted to discrete points for both geometries. More...

void	geometryChanged () override
	Should be called whenever the geometry associated with the engine has been modified and the engine must be updated to suit. More...

double	hausdorffDistance (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const
	Returns the Hausdorff distance between this geometry and geom. More...

double	hausdorffDistanceDensify (const QgsAbstractGeometry geom, double densifyFraction, QString errorMsg=nullptr) const
	Returns the Hausdorff distance between this geometry and geom. More...

QgsAbstractGeometry *	interpolate (double distance, QString *errorMsg=nullptr) const override

QgsAbstractGeometry *	intersection (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Calculate the intersection of this and geom. More...

bool	intersects (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom intersects this. More...

bool	isEmpty (QString *errorMsg=nullptr) const override

bool	isEqual (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if this is equal to geom. More...

bool	isSimple (QString *errorMsg=nullptr) const override
	Determines whether the geometry is simple (according to OGC definition). More...

bool	isValid (QString errorMsg=nullptr, bool allowSelfTouchingHoles=false, QgsGeometry errorLoc=nullptr) const override
	Returns `true` if the geometry is valid. More...

std::unique_ptr< QgsAbstractGeometry >	largestEmptyCircle (double tolerance, const QgsAbstractGeometry boundary=nullptr, QString errorMsg=nullptr) const
	Constructs the Largest Empty Circle for a set of obstacle geometries, up to a specified tolerance. More...

double	length (QString *errorMsg=nullptr) const override

double	lineLocatePoint (const QgsPoint &point, QString *errorMsg=nullptr) const
	Returns a distance representing the location along this linestring of the closest point on this linestring geometry to the specified point. More...

std::unique_ptr< QgsAbstractGeometry >	maximumInscribedCircle (double tolerance, QString *errorMsg=nullptr) const
	Returns the maximum inscribed circle. More...

QgsGeometry	mergeLines (QString *errorMsg=nullptr) const
	Merges any connected lines in a LineString/MultiLineString geometry and converts them to single line strings. More...

double	minimumClearance (QString *errorMsg=nullptr) const
	Computes the minimum clearance of a geometry. More...

std::unique_ptr< QgsAbstractGeometry >	minimumClearanceLine (QString *errorMsg=nullptr) const
	Returns a LineString whose endpoints define the minimum clearance of a geometry. More...

std::unique_ptr< QgsAbstractGeometry >	minimumWidth (QString *errorMsg=nullptr) const
	Returns a linestring geometry which represents the minimum diameter of the geometry. More...

std::unique_ptr< QgsAbstractGeometry >	node (QString *errorMsg=nullptr) const
	Returns a (Multi)LineString representing the fully noded version of a collection of linestrings. More...

QgsAbstractGeometry *	offsetCurve (double distance, int segments, Qgis::JoinStyle joinStyle, double miterLimit, QString *errorMsg=nullptr) const override
	Offsets a curve. More...

bool	overlaps (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom overlaps this. More...

QgsPoint *	pointOnSurface (QString *errorMsg=nullptr) const override
	Calculate a point that is guaranteed to be on the surface of this. More...

void	prepareGeometry () override
	Prepares the geometry, so that subsequent calls to spatial relation methods are much faster. More...

QString	relate (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Returns the Dimensional Extended 9 Intersection Model (DE-9IM) representation of the relationship between the geometries. More...

bool	relatePattern (const QgsAbstractGeometry geom, const QString &pattern, QString errorMsg=nullptr) const override
	Tests whether two geometries are related by a specified Dimensional Extended 9 Intersection Model (DE-9IM) pattern. More...

std::unique_ptr< QgsAbstractGeometry >	reshapeGeometry (const QgsLineString &reshapeWithLine, EngineOperationResult errorCode, QString errorMsg=nullptr) const
	Reshapes the geometry using a line. More...

std::unique_ptr< QgsAbstractGeometry >	sharedPaths (const QgsAbstractGeometry other, QString errorMsg=nullptr) const
	Find paths shared between the two given lineal geometries (this and other). More...

QgsGeometry	shortestLine (const QgsAbstractGeometry other, QString errorMsg=nullptr) const
	Returns the shortest line joining this geometry to the other geometry. More...

QgsGeometry	shortestLine (const QgsGeometry &other, QString *errorMsg=nullptr) const
	Returns the shortest line joining this geometry to the other geometry. More...

QgsAbstractGeometry *	simplify (double tolerance, QString *errorMsg=nullptr) const override

std::unique_ptr< QgsAbstractGeometry >	singleSidedBuffer (double distance, int segments, Qgis::BufferSide side, Qgis::JoinStyle joinStyle, double miterLimit, QString *errorMsg=nullptr) const
	Returns a single sided buffer for a geometry. More...

EngineOperationResult	splitGeometry (const QgsLineString &splitLine, QVector< QgsGeometry > &newGeometries, bool topological, QgsPointSequence &topologyTestPoints, QString *errorMsg=nullptr, bool skipIntersectionCheck=false) const override
	Splits this geometry according to a given line. More...

std::unique_ptr< QgsAbstractGeometry >	subdivide (int maxNodes, QString *errorMsg=nullptr) const
	Subdivides the geometry. More...

QgsAbstractGeometry *	symDifference (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Calculate the symmetric difference of this and geom. More...

bool	touches (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom touches this. More...

QgsGeometry	voronoiDiagram (const QgsAbstractGeometry extent=nullptr, double tolerance=0.0, bool edgesOnly=false, QString errorMsg=nullptr) const
	Creates a Voronoi diagram for the nodes contained within the geometry. More...

bool	within (const QgsAbstractGeometry geom, QString errorMsg=nullptr) const override
	Checks if geom is within this. More...

Public Member Functions inherited from QgsGeometryEngine
virtual	~QgsGeometryEngine ()=default

void	setLogErrors (bool enabled)
	Sets whether warnings and errors encountered during the geometry operations should be logged. More...

Static Public Member Functions
static Qgis::GeometryOperationResult	addPart (QgsGeometry &geometry, GEOSGeometry *newPart)
	Adds a new island polygon to a multipolygon feature. More...

static geos::unique_ptr	asGeos (const QgsAbstractGeometry *geometry, double precision=0)
	Returns a geos geometry - caller takes ownership of the object (should be deleted with GEOSGeom_destroy_r) More...

static geos::unique_ptr	asGeos (const QgsGeometry &geometry, double precision=0)
	Returns a geos geometry - caller takes ownership of the object (should be deleted with GEOSGeom_destroy_r) More...

static QgsPoint	coordSeqPoint (const GEOSCoordSequence *cs, int i, bool hasZ, bool hasM)

static std::unique_ptr< QgsAbstractGeometry >	fromGeos (const GEOSGeometry *geos)
	Create a geometry from a GEOSGeometry. More...

static std::unique_ptr< QgsPolygon >	fromGeosPolygon (const GEOSGeometry *geos)

static QgsGeometry	geometryFromGeos (const geos::unique_ptr &geos)
	Creates a new QgsGeometry object, feeding in a geometry in GEOS format. More...

static QgsGeometry	geometryFromGeos (GEOSGeometry *geos)
	Creates a new QgsGeometry object, feeding in a geometry in GEOS format. More...

static GEOSContextHandle_t	getGEOSHandler ()

static QgsGeometry	polygonize (const QVector< const QgsAbstractGeometry * > &geometries, QString *errorMsg=nullptr)
	Creates a GeometryCollection geometry containing possible polygons formed from the constituent linework of a set of geometries. More...

Additional Inherited Members
Public Types inherited from QgsGeometryEngine
enum	EngineOperationResult { Success = 0 , NothingHappened = 1000 , MethodNotImplemented , EngineError , NodedGeometryError , InvalidBaseGeometry , InvalidInput , SplitCannotSplitPoint }
	Success or failure of a geometry operation. More...

Protected Member Functions inherited from QgsGeometryEngine
	QgsGeometryEngine (const QgsAbstractGeometry *geometry)

void	logError (const QString &engineName, const QString &message) const
	Logs an error message encountered during an operation. More...

Protected Attributes inherited from QgsGeometryEngine
const QgsAbstractGeometry *	mGeometry = nullptr

bool	mLogErrors = true

Detailed Description

Does vector analysis using the geos library and handles import, export, exception handling*.

Note: not available in Python bindings

Definition at line 103 of file qgsgeos.h.

Constructor & Destructor Documentation

◆ QgsGeos()

QgsGeos::QgsGeos	(	const QgsAbstractGeometry *	geometry,
		double	precision = `0`
	)

GEOS geometry engine constructor.

Parameters

geometry	The geometry
precision	The precision of the grid to which to snap the geometry vertices. If 0, no snapping is performed.

Definition at line 142 of file qgsgeos.cpp.

Member Function Documentation

◆ addPart()

Qgis::GeometryOperationResult QgsGeos::addPart	(	QgsGeometry &	geometry,
		GEOSGeometry *	newPart
	)

static

Adds a new island polygon to a multipolygon feature.

Parameters

geometry	geometry to add part to
newPart	part to add. Ownership is NOT transferred.

Returns: OperationResult a result code: success or reason of failure

Definition at line 191 of file qgsgeos.cpp.

◆ area()

double QgsGeos::area ( QString * errorMsg = nullptr ) const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 730 of file qgsgeos.cpp.

◆ asGeos() [1/2]

geos::unique_ptr QgsGeos::asGeos	(	const QgsAbstractGeometry *	geometry,
		double	precision = `0`
	)

static

Returns a geos geometry - caller takes ownership of the object (should be deleted with GEOSGeom_destroy_r)

Parameters

geometry	geometry to convert to GEOS representation
precision	The precision of the grid to which to snap the geometry vertices. If 0, no snapping is performed.

Definition at line 1466 of file qgsgeos.cpp.

◆ asGeos() [2/2]

geos::unique_ptr QgsGeos::asGeos	(	const QgsGeometry &	geometry,
		double	precision = `0`
	)

static

Returns a geos geometry - caller takes ownership of the object (should be deleted with GEOSGeom_destroy_r)

Parameters

geometry	geometry to convert to GEOS representation
precision	The precision of the grid to which to snap the geometry vertices. If 0, no snapping is performed.

Definition at line 181 of file qgsgeos.cpp.

◆ buffer() [1/2]

QgsAbstractGeometry * QgsGeos::buffer	(	double	distance,
		int	segments,
		Qgis::EndCapStyle	endCapStyle,
		Qgis::JoinStyle	joinStyle,
		double	miterLimit,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Buffers a geometry.

Implements QgsGeometryEngine.

Definition at line 1700 of file qgsgeos.cpp.

◆ buffer() [2/2]

QgsAbstractGeometry * QgsGeos::buffer	(	double	distance,
		int	segments,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 1684 of file qgsgeos.cpp.

◆ centroid()

QgsPoint * QgsGeos::centroid ( QString * errorMsg = nullptr ) const

overridevirtual

Calculates the centroid of this.

May return a \c nullptr.

Since: QGIS 3.0 the centroid is returned

Implements QgsGeometryEngine.

Definition at line 1746 of file qgsgeos.cpp.

◆ clip()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::clip	(	const QgsRectangle &	rectangle,
		QString *	errorMsg = `nullptr`
	)		const

Performs a fast, non-robust intersection between the geometry and a rectangle.

The returned geometry may be invalid.

Definition at line 251 of file qgsgeos.cpp.

◆ closestPoint()

QgsGeometry QgsGeos::closestPoint	(	const QgsGeometry &	other,
		QString *	errorMsg = `nullptr`
	)		const

Returns the closest point on the geometry to the other geometry.

See also: shortestLine()

Since: QGIS 2.14

Definition at line 2511 of file qgsgeos.cpp.

◆ combine() [1/3]

QgsAbstractGeometry * QgsGeos::combine	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Calculate the combination of this and geom.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 386 of file qgsgeos.cpp.

◆ combine() [2/3]

QgsAbstractGeometry * QgsGeos::combine	(	const QVector< QgsAbstractGeometry * > &	geomList,
		QString *	errorMsg
	)		const

overridevirtual

Calculate the combination of this and geometries.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 391 of file qgsgeos.cpp.

◆ combine() [3/3]

QgsAbstractGeometry * QgsGeos::combine	(	const QVector< QgsGeometry > &	geometries,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Calculate the combination of this and geometries.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 415 of file qgsgeos.cpp.

◆ contains()

bool QgsGeos::contains	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom contains this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 655 of file qgsgeos.cpp.

◆ convexHull()

QgsAbstractGeometry * QgsGeos::convexHull ( QString * errorMsg = nullptr ) const

overridevirtual

Calculate the convex hull of this.

Implements QgsGeometryEngine.

Definition at line 1815 of file qgsgeos.cpp.

◆ coordSeqPoint()

QgsPoint QgsGeos::coordSeqPoint	(	const GEOSCoordSequence *	cs,
		int	i,
		bool	hasZ,
		bool	hasM
	)

static

Definition at line 1422 of file qgsgeos.cpp.

◆ crosses()

bool QgsGeos::crosses	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom crosses this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 640 of file qgsgeos.cpp.

◆ delaunayTriangulation()

QgsGeometry QgsGeos::delaunayTriangulation	(	double	tolerance = `0.0`,
		bool	edgesOnly = `false`,
		QString *	errorMsg = `nullptr`
	)		const

Returns the Delaunay triangulation for the vertices of the geometry.

The tolerance parameter specifies an optional snapping tolerance which can be used to improve the robustness of the triangulation. If edgesOnly is true than line string boundary geometries will be returned instead of polygons. An empty geometry will be returned if the diagram could not be calculated.

Since: QGIS 3.0

Definition at line 2717 of file qgsgeos.cpp.

◆ difference()

QgsAbstractGeometry * QgsGeos::difference	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Calculate the difference of this and geom.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 246 of file qgsgeos.cpp.

◆ disjoint()

bool QgsGeos::disjoint	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom is disjoint from this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 660 of file qgsgeos.cpp.

◆ distance()

double QgsGeos::distance	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Calculates the distance between this and geom.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 444 of file qgsgeos.cpp.

◆ distanceWithin()

bool QgsGeos::distanceWithin	(	const QgsAbstractGeometry *	geom,
		double	maxdistance,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom is within maxdistance distance from this geometry.

Since: QGIS 3.22

Implements QgsGeometryEngine.

Definition at line 478 of file qgsgeos.cpp.

◆ envelope()

QgsAbstractGeometry * QgsGeos::envelope ( QString * errorMsg = nullptr ) const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 1772 of file qgsgeos.cpp.

◆ frechetDistance()

double QgsGeos::frechetDistance	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

Returns the Fréchet distance between this geometry and geom, restricted to discrete points for both geometries.

The Fréchet distance is a measure of similarity between curves that takes into account the location and ordering of the points along the curves. Therefore it is often better than the Hausdorff distance.

This method requires a QGIS build based on GEOS 3.7 or later.

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.6 or earlier.

See also: frechetDistanceDensify()

Since: QGIS 3.20

Definition at line 571 of file qgsgeos.cpp.

◆ frechetDistanceDensify()

double QgsGeos::frechetDistanceDensify	(	const QgsAbstractGeometry *	geom,
		double	densifyFraction,
		QString *	errorMsg = `nullptr`
	)		const

Returns the Fréchet distance between this geometry and geom, restricted to discrete points for both geometries.

The Fréchet distance is a measure of similarity between curves that takes into account the location and ordering of the points along the curves. Therefore it is often better than the Hausdorff distance.

This function accepts a densifyFraction argument. The function performs a segment densification before computing the discrete Fréchet distance. The densifyFraction parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction.

This method can be used when the default approximation provided by frechetDistance() is not sufficient. Decreasing the densifyFraction parameter will make the distance returned approach the true Fréchet distance for the geometries.

This method requires a QGIS build based on GEOS 3.7 or later.

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.6 or earlier.

See also: frechetDistance()

Since: QGIS 3.20

Definition at line 600 of file qgsgeos.cpp.

◆ fromGeos()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::fromGeos ( const GEOSGeometry * geos )

static

Create a geometry from a GEOSGeometry.

Parameters

geos	GEOSGeometry. Ownership is NOT transferred.

Definition at line 1231 of file qgsgeos.cpp.

◆ fromGeosPolygon()

std::unique_ptr< QgsPolygon > QgsGeos::fromGeosPolygon ( const GEOSGeometry * geos )

static

Definition at line 1331 of file qgsgeos.cpp.

◆ geometryChanged()

void QgsGeos::geometryChanged ( )

overridevirtual

Should be called whenever the geometry associated with the engine has been modified and the engine must be updated to suit.

Implements QgsGeometryEngine.

Definition at line 206 of file qgsgeos.cpp.

◆ geometryFromGeos() [1/2]

QgsGeometry QgsGeos::geometryFromGeos ( const geos::unique_ptr & geos )

static

Creates a new QgsGeometry object, feeding in a geometry in GEOS format.

Definition at line 157 of file qgsgeos.cpp.

◆ geometryFromGeos() [2/2]

QgsGeometry QgsGeos::geometryFromGeos ( GEOSGeometry * geos )

static

Creates a new QgsGeometry object, feeding in a geometry in GEOS format.

This class will take ownership of the buffer.

Definition at line 150 of file qgsgeos.cpp.

◆ getGEOSHandler()

GEOSContextHandle_t QgsGeos::getGEOSHandler ( )

static

Definition at line 3222 of file qgsgeos.cpp.

◆ hausdorffDistance()

double QgsGeos::hausdorffDistance	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

Returns the Hausdorff distance between this geometry and geom.

This is basically a measure of how similar or dissimilar 2 geometries are.

This algorithm is an approximation to the standard Hausdorff distance. This approximation is exact or close enough for a large subset of useful cases. Examples of these are:

computing distance between Linestrings that are roughly parallel to each other, and roughly equal in length. This occurs in matching linear networks.
Testing similarity of geometries.

If the default approximate provided by this method is insufficient, use hausdorffDistanceDensify() instead.

See also: hausdorffDistanceDensify()

Since: QGIS 3.0

Definition at line 525 of file qgsgeos.cpp.

◆ hausdorffDistanceDensify()

double QgsGeos::hausdorffDistanceDensify	(	const QgsAbstractGeometry *	geom,
		double	densifyFraction,
		QString *	errorMsg = `nullptr`
	)		const

Returns the Hausdorff distance between this geometry and geom.

This is basically a measure of how similar or dissimilar 2 geometries are.

This function accepts a densifyFraction argument. The function performs a segment densification before computing the discrete Hausdorff distance. The densifyFraction parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction.

This method can be used when the default approximation provided by hausdorffDistance() is not sufficient. Decreasing the densifyFraction parameter will make the distance returned approach the true Hausdorff distance for the geometries.

See also: hausdorffDistance()

Since: QGIS 3.0

Definition at line 548 of file qgsgeos.cpp.

◆ interpolate()

QgsAbstractGeometry * QgsGeos::interpolate	(	double	distance,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 1731 of file qgsgeos.cpp.

◆ intersection()

QgsAbstractGeometry * QgsGeos::intersection	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Calculate the intersection of this and geom.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 241 of file qgsgeos.cpp.

◆ intersects()

bool QgsGeos::intersects	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom intersects this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 630 of file qgsgeos.cpp.

◆ isEmpty()

bool QgsGeos::isEmpty ( QString * errorMsg = nullptr ) const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 1909 of file qgsgeos.cpp.

◆ isEqual()

bool QgsGeos::isEqual	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if this is equal to geom.

If both are Null geometries, \c false is returned.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 1889 of file qgsgeos.cpp.

◆ isSimple()

bool QgsGeos::isSimple ( QString * errorMsg = nullptr ) const

overridevirtual

Determines whether the geometry is simple (according to OGC definition).

Since: QGIS 3.0

Implements QgsGeometryEngine.

Definition at line 1923 of file qgsgeos.cpp.

◆ isValid()

bool QgsGeos::isValid	(	QString *	errorMsg = `nullptr`,
		bool	allowSelfTouchingHoles = `false`,
		QgsGeometry *	errorLoc = `nullptr`
	)		const

overridevirtual

Returns true if the geometry is valid.

If the geometry is invalid, errorMsg will be filled with the reported geometry error.

The allowSelfTouchingHoles argument specifies whether self-touching holes are permitted. OGC validity states that self-touching holes are NOT permitted, whilst other vendor validity checks (e.g. ESRI) permit self-touching holes.

If errorLoc is specified, it will be set to the geometry of the error location.

Implements QgsGeometryEngine.

Definition at line 1831 of file qgsgeos.cpp.

◆ largestEmptyCircle()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::largestEmptyCircle	(	double	tolerance,
		const QgsAbstractGeometry *	boundary = `nullptr`,
		QString *	errorMsg = `nullptr`
	)		const

Constructs the Largest Empty Circle for a set of obstacle geometries, up to a specified tolerance.

The Largest Empty Circle is the largest circle which has its center in the convex hull of the obstacles (the boundary), and whose interior does not intersect with any obstacle. The circle center is the point in the interior of the boundary which has the farthest distance from the obstacles (up to tolerance). The circle is determined by the center point and a point lying on an obstacle indicating the circle radius. The implementation uses a successive-approximation technique over a grid of square cells covering the obstacles and boundary. The grid is refined using a branch-and-bound algorithm. Point containment and distance are computed in a performant way by using spatial indexes. Returns a two-point linestring, with one point at the center of the inscribed circle and the other on the boundary of the inscribed circle.

This method requires a QGIS build based on GEOS 3.9 or later.

Warning: the tolerance value must be a value greater than 0, or the algorithm may never converge on a solution

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.8 or earlier.

Since: QGIS 3.20

Definition at line 2248 of file qgsgeos.cpp.

◆ length()

double QgsGeos::length ( QString * errorMsg = nullptr ) const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 747 of file qgsgeos.cpp.

◆ lineLocatePoint()

double QgsGeos::lineLocatePoint	(	const QgsPoint &	point,
		QString *	errorMsg = `nullptr`
	)		const

Returns a distance representing the location along this linestring of the closest point on this linestring geometry to the specified point.

Ie, the returned value indicates how far along this linestring you need to traverse to get to the closest location where this linestring comes to the specified point.

Parameters

point	point to seek proximity to
errorMsg	error messages emitted, if any

Returns: distance along line, or -1 on error

Note: only valid for linestring geometries

Definition at line 2615 of file qgsgeos.cpp.

◆ maximumInscribedCircle()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::maximumInscribedCircle	(	double	tolerance,
		QString *	errorMsg = `nullptr`
	)		const

Returns the maximum inscribed circle.

Constructs the Maximum Inscribed Circle for a polygonal geometry, up to a specified tolerance. The Maximum Inscribed Circle is determined by a point in the interior of the area which has the farthest distance from the area boundary, along with a boundary point at that distance. In the context of geography the center of the Maximum Inscribed Circle is known as the Pole of Inaccessibility. A cartographic use case is to determine a suitable point to place a map label within a polygon. The radius length of the Maximum Inscribed Circle is a measure of how "narrow" a polygon is. It is the distance at which the negative buffer becomes empty. The class supports polygons with holes and multipolygons. The implementation uses a successive-approximation technique over a grid of square cells covering the area geometry. The grid is refined using a branch-and-bound algorithm. Point containment and distance are computed in a performant way by using spatial indexes. Returns a two-point linestring, with one point at the center of the inscribed circle and the other on the boundary of the inscribed circle.

This method requires a QGIS build based on GEOS 3.9 or later.

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.8 or earlier.

Since: QGIS 3.20

Definition at line 2226 of file qgsgeos.cpp.

◆ mergeLines()

QgsGeometry QgsGeos::mergeLines ( QString * errorMsg = nullptr ) const

Merges any connected lines in a LineString/MultiLineString geometry and converts them to single line strings.

Parameters

errorMsg if specified, will be set to any reported GEOS errors

Returns: a LineString or MultiLineString geometry, with any connected lines joined. An empty geometry will be returned if the input geometry was not a LineString/MultiLineString geometry.

Since: QGIS 3.0

Definition at line 2492 of file qgsgeos.cpp.

◆ minimumClearance()

double QgsGeos::minimumClearance ( QString * errorMsg = nullptr ) const

Computes the minimum clearance of a geometry.

The minimum clearance is the smallest amount by which a vertex could be moved to produce an invalid polygon, a non-simple linestring, or a multipoint with repeated points. If a geometry has a minimum clearance of 'eps', it can be said that:

No two distinct vertices in the geometry are separated by less than 'eps'
No vertex is closer than 'eps' to a line segment of which it is not an endpoint.

If the minimum clearance cannot be defined for a geometry (such as with a single point, or a multipoint whose points are identical) a value of infinity will be returned.

If an error occurs while calculating the clearance NaN will be returned.

This method requires a QGIS build based on GEOS 3.6 or later.

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.5 or earlier.

Since: QGIS 3.20

Definition at line 2296 of file qgsgeos.cpp.

◆ minimumClearanceLine()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::minimumClearanceLine ( QString * errorMsg = nullptr ) const

Returns a LineString whose endpoints define the minimum clearance of a geometry.

If the geometry has no minimum clearance, an empty LineString will be returned.

This method requires a QGIS build based on GEOS 3.6 or later.

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.5 or earlier.

Since: QGIS 3.20

Definition at line 2319 of file qgsgeos.cpp.

◆ minimumWidth()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::minimumWidth ( QString * errorMsg = nullptr ) const

Returns a linestring geometry which represents the minimum diameter of the geometry.

The minimum diameter is defined to be the width of the smallest band that contains the geometry, where a band is a strip of the plane defined by two parallel lines. This can be thought of as the smallest hole that the geometry can be moved through, with a single rotation.

This method requires a QGIS build based on GEOS 3.6 or later.

Exceptions

QgsNotSupportedException on QGIS builds based on GEOS 3.5 or earlier.

Since: QGIS 3.20

Definition at line 2275 of file qgsgeos.cpp.

◆ node()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::node ( QString * errorMsg = nullptr ) const

Returns a (Multi)LineString representing the fully noded version of a collection of linestrings.

The noding preserves all of the input nodes, and introduces the least possible number of new nodes. The resulting linework is dissolved (duplicate lines are removed).

The input geometry type should be a (Multi)LineString.

Since: QGIS 3.20

Definition at line 2340 of file qgsgeos.cpp.

◆ offsetCurve()

QgsAbstractGeometry * QgsGeos::offsetCurve	(	double	distance,
		int	segments,
		Qgis::JoinStyle	joinStyle,
		double	miterLimit,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Offsets a curve.

Implements QgsGeometryEngine.

Definition at line 2185 of file qgsgeos.cpp.

◆ overlaps()

bool QgsGeos::overlaps	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom overlaps this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 650 of file qgsgeos.cpp.

◆ pointOnSurface()

QgsPoint * QgsGeos::pointOnSurface ( QString * errorMsg = nullptr ) const

overridevirtual

Calculate a point that is guaranteed to be on the surface of this.

May return a \c nullptr.

Since: QGIS 3.0 the centroid is returned

Implements QgsGeometryEngine.

Definition at line 1787 of file qgsgeos.cpp.

◆ polygonize()

QgsGeometry QgsGeos::polygonize	(	const QVector< const QgsAbstractGeometry * > &	geometries,
		QString *	errorMsg = `nullptr`
	)

static

Creates a GeometryCollection geometry containing possible polygons formed from the constituent linework of a set of geometries.

The input geometries must be fully noded (i.e. nodes exist at every common intersection of the geometries). The easiest way to ensure this is to first unary union these geometries by calling combine() on the set of input geometries and then pass the result to polygonize(). An empty geometry will be returned in the case of errors.

Since: QGIS 3.0

Definition at line 2646 of file qgsgeos.cpp.

◆ prepareGeometry()

void QgsGeos::prepareGeometry ( )

overridevirtual

Prepares the geometry, so that subsequent calls to spatial relation methods are much faster.

This should be called for any geometry which is used for multiple relation tests against other geometries.

See also: geometryChanged()

Implements QgsGeometryEngine.

Definition at line 213 of file qgsgeos.cpp.

◆ relate()

QString QgsGeos::relate	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Returns the Dimensional Extended 9 Intersection Model (DE-9IM) representation of the relationship between the geometries.

Parameters

geom	geometry to relate to
errorMsg	destination storage for any error message

Returns: DE-9IM string for relationship, or an empty string if an error occurred

Since: QGIS 2.12

Implements QgsGeometryEngine.

Definition at line 665 of file qgsgeos.cpp.

◆ relatePattern()

bool QgsGeos::relatePattern	(	const QgsAbstractGeometry *	geom,
		const QString &	pattern,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Tests whether two geometries are related by a specified Dimensional Extended 9 Intersection Model (DE-9IM) pattern.

Parameters

geom	geometry to relate to
pattern	DE-9IM pattern for match
errorMsg	destination storage for any error message

Returns: true if geometry relationship matches with pattern

Since: QGIS 2.14

Implements QgsGeometryEngine.

Definition at line 700 of file qgsgeos.cpp.

◆ reshapeGeometry()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::reshapeGeometry	(	const QgsLineString &	reshapeWithLine,
		EngineOperationResult *	errorCode,
		QString *	errorMsg = `nullptr`
	)		const

Reshapes the geometry using a line.

Parameters

reshapeWithLine	the line used to reshape lines or polygons
errorCode	if specified, provides result of operation (success or reason of failure)
errorMsg	if specified, provides more details about failure

Returns: the reshaped geometry

Definition at line 2376 of file qgsgeos.cpp.

◆ sharedPaths()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::sharedPaths	(	const QgsAbstractGeometry *	other,
		QString *	errorMsg = `nullptr`
	)		const

Find paths shared between the two given lineal geometries (this and other).

Returns a GeometryCollection having two elements:

first element is a MultiLineString containing shared paths having the same direction on both inputs
second element is a MultiLineString containing shared paths having the opposite direction on the two inputs

Returns nullptr on exception.

Since: QGIS 3.20

Definition at line 2356 of file qgsgeos.cpp.

◆ shortestLine() [1/2]

QgsGeometry QgsGeos::shortestLine	(	const QgsAbstractGeometry *	other,
		QString *	errorMsg = `nullptr`
	)		const

Returns the shortest line joining this geometry to the other geometry.

See also: closestPoint()

Since: QGIS 3.20

Definition at line 2568 of file qgsgeos.cpp.

◆ shortestLine() [2/2]

QgsGeometry QgsGeos::shortestLine	(	const QgsGeometry &	other,
		QString *	errorMsg = `nullptr`
	)		const

Returns the shortest line joining this geometry to the other geometry.

See also: closestPoint()

Since: QGIS 2.14

Definition at line 2558 of file qgsgeos.cpp.

◆ simplify()

QgsAbstractGeometry * QgsGeos::simplify	(	double	tolerance,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Implements QgsGeometryEngine.

Definition at line 1716 of file qgsgeos.cpp.

◆ singleSidedBuffer()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::singleSidedBuffer	(	double	distance,
		int	segments,
		Qgis::BufferSide	side,
		Qgis::JoinStyle	joinStyle,
		double	miterLimit,
		QString *	errorMsg = `nullptr`
	)		const

Returns a single sided buffer for a geometry.

The buffer is only applied to one side of the geometry.

Parameters

distance	buffer distance
segments	for round joins, number of segments to approximate quarter-circle
side	side of geometry to buffer (0 = left, 1 = right)
joinStyle	join style for corners ( Round (1) / Miter (2) / Bevel (3) )
miterLimit	limit on the miter ratio used for very sharp corners
errorMsg	error messages emitted, if any

Returns: buffered geometry, or an nullptr if buffer could not be calculated

Since: QGIS 3.0

Definition at line 2200 of file qgsgeos.cpp.

◆ splitGeometry()

QgsGeometryEngine::EngineOperationResult QgsGeos::splitGeometry	(	const QgsLineString &	splitLine,
		QVector< QgsGeometry > &	newGeometries,
		bool	topological,
		QgsPointSequence &	topologyTestPoints,
		QString *	errorMsg = `nullptr`,
		bool	skipIntersectionCheck = `false`
	)		const

overridevirtual

Splits this geometry according to a given line.

Parameters

	splitLine	the line that splits the geometry
[out]	newGeometries	list of new geometries that have been created with the split
	topological	`true` if topological editing is enabled
[out]	topologyTestPoints	points that need to be tested for topological completeness in the dataset
[out]	errorMsg	error messages emitted, if any
	skipIntersectionCheck	set to `true` to skip the potentially expensive initial intersection check. Only set this flag if an intersection test has already been performed by the caller!

Returns: 0 in case of success, 1 if geometry has not been split, error else

Reimplemented from QgsGeometryEngine.

Definition at line 763 of file qgsgeos.cpp.

◆ subdivide()

std::unique_ptr< QgsAbstractGeometry > QgsGeos::subdivide	(	int	maxNodes,
		QString *	errorMsg = `nullptr`
	)		const

Subdivides the geometry.

The returned geometry will be a collection containing subdivided parts from the original geometry, where no part has more then the specified maximum number of nodes (maxNodes).

This is useful for dividing a complex geometry into less complex parts, which are better able to be spatially indexed and faster to perform further operations such as intersects on. The returned geometry parts may not be valid and may contain self-intersections.

The minimum allowed value for maxNodes is 8.

Curved geometries are not supported.

Since: QGIS 3.0

Definition at line 366 of file qgsgeos.cpp.

◆ symDifference()

QgsAbstractGeometry * QgsGeos::symDifference	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Calculate the symmetric difference of this and geom.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 439 of file qgsgeos.cpp.

◆ touches()

bool QgsGeos::touches	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom touches this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 635 of file qgsgeos.cpp.

◆ voronoiDiagram()

QgsGeometry QgsGeos::voronoiDiagram	(	const QgsAbstractGeometry *	extent = `nullptr`,
		double	tolerance = `0.0`,
		bool	edgesOnly = `false`,
		QString *	errorMsg = `nullptr`
	)		const

Creates a Voronoi diagram for the nodes contained within the geometry.

Returns the Voronoi polygons for the nodes contained within the geometry. If extent is specified then it will be used as a clipping envelope for the diagram. If no extent is set then the clipping envelope will be automatically calculated. In either case the diagram will be clipped to the larger of the provided envelope OR the envelope surrounding all input nodes. The tolerance parameter specifies an optional snapping tolerance which can be used to improve the robustness of the diagram calculation. If edgesOnly is true than line string boundary geometries will be returned instead of polygons. An empty geometry will be returned if the diagram could not be calculated.

Since: QGIS 3.0

Definition at line 2685 of file qgsgeos.cpp.

◆ within()

bool QgsGeos::within	(	const QgsAbstractGeometry *	geom,
		QString *	errorMsg = `nullptr`
	)		const

overridevirtual

Checks if geom is within this.

Since: QGIS 3.0 geom is a pointer

Implements QgsGeometryEngine.

Definition at line 645 of file qgsgeos.cpp.

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

/build/qgis-3.22.4+99unstable/src/core/geometry/qgsgeos.h
/build/qgis-3.22.4+99unstable/src/core/geometry/qgsgeos.cpp

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QgsGeos()

Member Function Documentation

◆ addPart()

◆ area()

◆ asGeos() [1/2]

◆ asGeos() [2/2]

◆ buffer() [1/2]

◆ buffer() [2/2]

◆ centroid()

◆ clip()

◆ closestPoint()

◆ combine() [1/3]

◆ combine() [2/3]

◆ combine() [3/3]

◆ contains()

◆ convexHull()

◆ coordSeqPoint()

◆ crosses()

◆ delaunayTriangulation()

◆ difference()

◆ disjoint()

◆ distance()

◆ distanceWithin()

◆ envelope()

◆ frechetDistance()

◆ frechetDistanceDensify()

◆ fromGeos()

◆ fromGeosPolygon()

◆ geometryChanged()

◆ geometryFromGeos() [1/2]

◆ geometryFromGeos() [2/2]

◆ getGEOSHandler()

◆ hausdorffDistance()

◆ hausdorffDistanceDensify()

◆ interpolate()

◆ intersection()

◆ intersects()

◆ isEmpty()

◆ isEqual()

◆ isSimple()

◆ isValid()

◆ largestEmptyCircle()

◆ length()

◆ lineLocatePoint()

◆ maximumInscribedCircle()

◆ mergeLines()

◆ minimumClearance()

◆ minimumClearanceLine()

◆ minimumWidth()

◆ node()

◆ offsetCurve()

◆ overlaps()

◆ pointOnSurface()

◆ polygonize()

◆ prepareGeometry()

◆ relate()

◆ relatePattern()

◆ reshapeGeometry()

◆ sharedPaths()

◆ shortestLine() [1/2]

◆ shortestLine() [2/2]

◆ simplify()

◆ singleSidedBuffer()

◆ splitGeometry()

◆ subdivide()

◆ symDifference()

◆ touches()

◆ voronoiDiagram()

◆ within()