The QGis class provides vector geometry analysis functions. More...

#include <qgsgeometryanalyzer.h>

Public Member Functions
bool	buffer (QgsVectorLayer layer, const QString &shapefileName, double bufferDistance, bool onlySelectedFeatures=false, bool dissolve=false, int bufferDistanceField=-1, QProgressDialog p=nullptr)
	Create buffers for a vector layer and write it to a new shape file. More...

bool	centroids (QgsVectorLayer layer, const QString &shapefileName, bool onlySelectedFeatures=false, QProgressDialog p=nullptr)
	Calculate the true centroids, or 'center of mass' for a vector layer and write it to a new shape file. More...

bool	convexHull (QgsVectorLayer layer, const QString &shapefileName, bool onlySelectedFeatures=false, int uniqueIdField=-1, QProgressDialog p=nullptr)
	Create convex hull(s) of a vector layer and write it to a new shape file. More...

bool	dissolve (QgsVectorLayer layer, const QString &shapefileName, bool onlySelectedFeatures=false, int uniqueIdField=-1, QProgressDialog p=nullptr)
	Dissolve a vector layer and write it to a new shape file. More...

bool	eventLayer (QgsVectorLayer lineLayer, QgsVectorLayer eventLayer, int lineField, int eventField, QgsFeatureIds &unlocatedFeatureIds, const QString &outputLayer, const QString &outputFormat, int locationField1, int locationField2=-1, int offsetField=-1, double offsetScale=1.0, bool forceSingleGeometry=false, QgsVectorDataProvider memoryProvider=nullptr, QProgressDialog p=nullptr)
	Creates an event layer (multipoint or multiline) by locating features from a (non-spatial) event table along the features of a line layer. More...

bool	extent (QgsVectorLayer layer, const QString &shapefileName, bool onlySelectedFeatures=false, QProgressDialog p=0)
	Create a polygon based on the extent of all (selected) features and write it to a new shape file. More...

QgsGeometry *	locateAlongMeasure (double measure, const QgsGeometry *lineGeom)
	Returns linear reference geometry. More...

QgsGeometry *	locateBetweenMeasures (double fromMeasure, double toMeasure, const QgsGeometry *lineGeom)
	Returns linear reference geometry as a multiline (or 0 if no match). More...

bool	simplify (QgsVectorLayer layer, const QString &shapefileName, double tolerance, bool onlySelectedFeatures=false, QProgressDialog p=nullptr)
	Simplify vector layer using (a modified) Douglas-Peucker algorithm and write it to a new shape file. More...

Detailed Description

The QGis class provides vector geometry analysis functions.

Definition at line 35 of file qgsgeometryanalyzer.h.

Member Function Documentation

◆ buffer()

bool QgsGeometryAnalyzer::buffer	(	QgsVectorLayer *	layer,
		const QString &	shapefileName,
		double	bufferDistance,
		bool	onlySelectedFeatures = `false`,
		bool	dissolve = `false`,
		int	bufferDistanceField = `-1`,
		QProgressDialog *	p = `nullptr`
	)

Create buffers for a vector layer and write it to a new shape file.

Parameters

layer	input vector layer
shapefileName	path to the output shp
bufferDistance	distance for buffering (if no buffer field is specified)
onlySelectedFeatures	if true, only selected features are considered, else all the features
dissolve	if true, merge all the buffers to a big multipolygon
bufferDistanceField	index of the attribute field that contains the buffer distance (or -1 if all features have the same buffer distance)
p	progress dialog (or 0 if no progress dialog is to be shown)

Definition at line 732 of file qgsgeometryanalyzer.cpp.

◆ centroids()

bool QgsGeometryAnalyzer::centroids	(	QgsVectorLayer *	layer,
		const QString &	shapefileName,
		bool	onlySelectedFeatures = `false`,
		QProgressDialog *	p = `nullptr`
	)

Calculate the true centroids, or 'center of mass' for a vector layer and write it to a new shape file.

Parameters

layer	input vector layer
shapefileName	path to the output shp
onlySelectedFeatures	if true, only selected features are considered, else all the features
p	progress dialog (or 0 if no progress dialog is to be shown)

Definition at line 149 of file qgsgeometryanalyzer.cpp.

◆ convexHull()

bool QgsGeometryAnalyzer::convexHull	(	QgsVectorLayer *	layer,
		const QString &	shapefileName,
		bool	onlySelectedFeatures = `false`,
		int	uniqueIdField = `-1`,
		QProgressDialog *	p = `nullptr`
	)

Create convex hull(s) of a vector layer and write it to a new shape file.

Parameters

layer	input vector layer
shapefileName	path to the output shp
onlySelectedFeatures	if true, only selected features are considered, else all the features
uniqueIdField	index of the attribute field that contains the unique convex hull id (or -1 if all features have the same buffer distance)
p	progress dialog (or 0 if no progress dialog is to be shown)

Definition at line 365 of file qgsgeometryanalyzer.cpp.

◆ dissolve()

bool QgsGeometryAnalyzer::dissolve	(	QgsVectorLayer *	layer,
		const QString &	shapefileName,
		bool	onlySelectedFeatures = `false`,
		int	uniqueIdField = `-1`,
		QProgressDialog *	p = `nullptr`
	)

Dissolve a vector layer and write it to a new shape file.

Parameters

layer	input vector layer
shapefileName	path to the output shp
onlySelectedFeatures	if true, only selected features are considered, else all the features
uniqueIdField	index of the attribute field that contains the unique id to dissolve on (or -1 if all features should be dissolved together)
p	progress dialog (or 0 if no progress dialog is to be shown)

Definition at line 575 of file qgsgeometryanalyzer.cpp.

◆ eventLayer()

bool QgsGeometryAnalyzer::eventLayer	(	QgsVectorLayer *	lineLayer,
		QgsVectorLayer *	eventLayer,
		int	lineField,
		int	eventField,
		QgsFeatureIds &	unlocatedFeatureIds,
		const QString &	outputLayer,
		const QString &	outputFormat,
		int	locationField1,
		int	locationField2 = `-1`,
		int	offsetField = `-1`,
		double	offsetScale = `1.0`,
		bool	forceSingleGeometry = `false`,
		QgsVectorDataProvider *	memoryProvider = `nullptr`,
		QProgressDialog *	p = `nullptr`
	)

Creates an event layer (multipoint or multiline) by locating features from a (non-spatial) event table along the features of a line layer.

Note that currently (until QgsGeometry supports m-values) the z-coordinate of the line layer is used for linear referencing

Parameters

lineLayer	layer with the line geometry
eventLayer	layer with features and location field
lineField	join index in line layer
eventField	join index in event layer
outputLayer	name of output file (can be empty if a memory layer is used)
outputFormat	name of output format (can be empty if a memory provider is used to store the results)
unlocatedFeatureIds	out: ids of event features where linear referencing was not successful
locationField1	attribute index of location field in event layer
locationField2	attribute index of location end field (or -1 for point layer)
offsetField	attribute index for offset field. Negative offset value = offset to left side, positive value = offset to right side
offsetScale	factor to scale offset
forceSingleGeometry	force layer to single point/line type. Feature attributes are copied in case of multiple matches
memoryProvider	memory provider to write output to (can be 0 if output is written to a file)
p	progress dialog or 0 if no progress dialog should be shown

Definition at line 890 of file qgsgeometryanalyzer.cpp.

◆ extent()

bool QgsGeometryAnalyzer::extent	(	QgsVectorLayer *	layer,
		const QString &	shapefileName,
		bool	onlySelectedFeatures = `false`,
		QProgressDialog *	p = `0`
	)

Create a polygon based on the extent of all (selected) features and write it to a new shape file.

Parameters

layer	input vector layer
shapefileName	path to the output shp
onlySelectedFeatures	if true, only selected features are considered, else all the features
p	progress dialog (or 0 if no progress dialog is to be shown)

Definition at line 265 of file qgsgeometryanalyzer.cpp.

◆ locateAlongMeasure()

QgsGeometry * QgsGeometryAnalyzer::locateAlongMeasure	(	double	measure,
		const QgsGeometry *	lineGeom
	)

Returns linear reference geometry.

Unlike the PostGIS function, this method always returns multipoint or 0 if no match (not geometry collection). Currently, the z-coordinates are considered to be the measures (no support for m-values in QGIS)

Definition at line 1214 of file qgsgeometryanalyzer.cpp.

◆ locateBetweenMeasures()

QgsGeometry * QgsGeometryAnalyzer::locateBetweenMeasures	(	double	fromMeasure,
		double	toMeasure,
		const QgsGeometry *	lineGeom
	)

Returns linear reference geometry as a multiline (or 0 if no match).

Currently, the z-coordinates are considered to be the measures (no support for m-values in QGIS)

Definition at line 1173 of file qgsgeometryanalyzer.cpp.

◆ simplify()

bool QgsGeometryAnalyzer::simplify	(	QgsVectorLayer *	layer,
		const QString &	shapefileName,
		double	tolerance,
		bool	onlySelectedFeatures = `false`,
		QProgressDialog *	p = `nullptr`
	)

Simplify vector layer using (a modified) Douglas-Peucker algorithm and write it to a new shape file.

Parameters

layer	input vector layer
shapefileName	path to the output shp
tolerance	(level of simplification)
onlySelectedFeatures	if true, only selected features are considered, else all the features
p	progress dialog (or 0 if no progress dialog is to be shown)

Definition at line 32 of file qgsgeometryanalyzer.cpp.

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

/tmp/buildd/qgis-2.18.21+99unstable/src/analysis/vector/qgsgeometryanalyzer.h
/tmp/buildd/qgis-2.18.21+99unstable/src/analysis/vector/qgsgeometryanalyzer.cpp

Public Member Functions

Detailed Description

Member Function Documentation

◆ buffer()

◆ centroids()

◆ convexHull()

◆ dissolve()

◆ eventLayer()

◆ extent()

◆ locateAlongMeasure()

◆ locateBetweenMeasures()

◆ simplify()