QGIS API Documentation  3.17.0-Master (7a14973234)
Public Member Functions | Static Public Member Functions | List of all members
QgsInternalGeometryEngine Class Reference

This class offers geometry processing methods. More...

#include <qgsinternalgeometryengine.h>

Public Member Functions

 QgsInternalGeometryEngine (const QgsGeometry &geometry)
 The caller is responsible that the geometry is available and unchanged for the whole lifetime of this object. More...
 
QgsGeometry convertToCurves (double distanceTolerance, double angleTolerance) const
 Attempts to convert a non-curved geometry into a curved geometry type (e.g. More...
 
QgsGeometry densifyByCount (int extraNodesPerSegment) const
 Densifies the geometry by adding the specified number of extra nodes within each segment of the geometry. More...
 
QgsGeometry densifyByDistance (double distance) const
 Densifies the geometry by adding regularly placed extra nodes inside each segment so that the maximum distance between any two nodes does not exceed the specified distance. More...
 
QgsGeometry extrude (double x, double y) const
 Will extrude a line or (segmentized) curve by a given offset and return a polygon representation of it. More...
 
QString lastError () const
 Returns an error string referring to the last error encountered. More...
 
QgsGeometry orientedMinimumBoundingBox (double &area, double &angle, double &width, double &height) const
 Returns the oriented minimum bounding box for the geometry, which is the smallest (by area) rotated rectangle which fully encompasses the geometry. More...
 
QgsGeometry orthogonalize (double tolerance=1.0E-8, int maxIterations=1000, double angleThreshold=15.0) const
 Attempts to orthogonalize a line or polygon geometry by shifting vertices to make the geometries angles either right angles or flat lines. More...
 
QgsGeometry poleOfInaccessibility (double precision, double *distanceFromBoundary=nullptr) const
 Calculates the approximate pole of inaccessibility for a surface, which is the most distant internal point from the boundary of the surface. More...
 
QgsGeometry taperedBuffer (double startWidth, double endWidth, int segments) const
 Calculates a tapered width buffer for a (multi)curve geometry. More...
 
QgsGeometry variableWidthBuffer (int segments, const std::function< std::unique_ptr< double[] >(const QgsLineString *line) > &widthFunction) const
 Calculates a variable width buffer for a (multi)curve geometry. More...
 
QgsGeometry variableWidthBufferByM (int segments) const
 Calculates a variable width buffer using the m-values from a (multi)line geometry. More...
 

Static Public Member Functions

static QVector< QgsPointXYrandomPointsInPolygon (const QgsGeometry &polygon, int count, const std::function< bool(const QgsPointXY &) > &acceptPoint, unsigned long seed=0, QgsFeedback *feedback=nullptr, int maxTriesPerPoint=0)
 Returns a list of count random points generated inside a polygon geometry (if acceptPoint is specified, and restrictive, the number of points returned may be less than count). More...
 

Detailed Description

This class offers geometry processing methods.

The methods are available via QgsGeometry::[geometryfunction] and therefore this does not need to be accessed directly.

Note
not available in Python bindings

Definition at line 41 of file qgsinternalgeometryengine.h.

Constructor & Destructor Documentation

◆ QgsInternalGeometryEngine()

QgsInternalGeometryEngine::QgsInternalGeometryEngine ( const QgsGeometry geometry)
explicit

The caller is responsible that the geometry is available and unchanged for the whole lifetime of this object.

Parameters
geometry

Definition at line 38 of file qgsinternalgeometryengine.cpp.

Member Function Documentation

◆ convertToCurves()

QgsGeometry QgsInternalGeometryEngine::convertToCurves ( double  distanceTolerance,
double  angleTolerance 
) const

Attempts to convert a non-curved geometry into a curved geometry type (e.g.

LineString to CompoundCurve, Polygon to CurvePolygon).

The distanceTolerance specifies the maximum deviation allowed between the original location of vertices and where they would fall on the candidate curved geometry.

This method only consider a segments as suitable for replacing with an arc if the points are all regularly spaced on the candidate arc. The pointSpacingAngleTolerance parameter specifies the maximum angular deviation (in radians) allowed when testing for regular point spacing.

Note
The API is considered EXPERIMENTAL and can be changed without a notice
Since
QGIS 3.14

Definition at line 1409 of file qgsinternalgeometryengine.cpp.

◆ densifyByCount()

QgsGeometry QgsInternalGeometryEngine::densifyByCount ( int  extraNodesPerSegment) const

Densifies the geometry by adding the specified number of extra nodes within each segment of the geometry.

If the geometry has z or m values present then these will be linearly interpolated at the added nodes. Curved geometry types are automatically segmentized by this routine.

Since
QGIS 3.0

Definition at line 660 of file qgsinternalgeometryengine.cpp.

◆ densifyByDistance()

QgsGeometry QgsInternalGeometryEngine::densifyByDistance ( double  distance) const

Densifies the geometry by adding regularly placed extra nodes inside each segment so that the maximum distance between any two nodes does not exceed the specified distance.

E.g. specifying a distance 3 would cause the segment [0 0] -> [10 0] to be converted to [0 0] -> [2.5 0] -> [5 0] -> [7.5 0] -> [10 0], since 3 extra nodes are required on the segment and spacing these at 2.5 increments allows them to be evenly spaced over the segment. If the geometry has z or m values present then these will be linearly interpolated at the added nodes. Curved geometry types are automatically segmentized by this routine.

Since
QGIS 3.0

Definition at line 696 of file qgsinternalgeometryengine.cpp.

◆ extrude()

QgsGeometry QgsInternalGeometryEngine::extrude ( double  x,
double  y 
) const

Will extrude a line or (segmentized) curve by a given offset and return a polygon representation of it.

Parameters
xoffset in x direction
yoffset in y direction
Returns
an extruded polygon

Definition at line 55 of file qgsinternalgeometryengine.cpp.

◆ lastError()

QString QgsInternalGeometryEngine::lastError ( ) const

Returns an error string referring to the last error encountered.

Since
QGIS 3.16

Definition at line 44 of file qgsinternalgeometryengine.cpp.

◆ orientedMinimumBoundingBox()

QgsGeometry QgsInternalGeometryEngine::orientedMinimumBoundingBox ( double &  area,
double &  angle,
double &  width,
double &  height 
) const

Returns the oriented minimum bounding box for the geometry, which is the smallest (by area) rotated rectangle which fully encompasses the geometry.

The area, angle (clockwise in degrees from North), width and height of the rotated bounding box will also be returned.

If an error was encountered while creating the result, more information can be retrieved by calling lastError().

Since
QGIS 3.16

Definition at line 1452 of file qgsinternalgeometryengine.cpp.

◆ orthogonalize()

QgsGeometry QgsInternalGeometryEngine::orthogonalize ( double  tolerance = 1.0E-8,
int  maxIterations = 1000,
double  angleThreshold = 15.0 
) const

Attempts to orthogonalize a line or polygon geometry by shifting vertices to make the geometries angles either right angles or flat lines.

This is an iterative algorithm which will loop until either the vertices are within a specified tolerance of right angles or a set number of maximum iterations is reached. The angle threshold parameter specifies how close to a right angle or straight line an angle must be before it is attempted to be straightened.

Since
QGIS 3.0

Definition at line 502 of file qgsinternalgeometryengine.cpp.

◆ poleOfInaccessibility()

QgsGeometry QgsInternalGeometryEngine::poleOfInaccessibility ( double  precision,
double *  distanceFromBoundary = nullptr 
) const

Calculates the approximate pole of inaccessibility for a surface, which is the most distant internal point from the boundary of the surface.

This function uses the 'polylabel' algorithm (Vladimir Agafonkin, 2016), which is an iterative approach guaranteed to find the true pole of inaccessibility within a specified tolerance. More precise tolerances require more iterations and will take longer to calculate. Optionally, the distance to the polygon boundary from the pole can be stored.

Definition at line 246 of file qgsinternalgeometryengine.cpp.

◆ randomPointsInPolygon()

QVector< QgsPointXY > QgsInternalGeometryEngine::randomPointsInPolygon ( const QgsGeometry polygon,
int  count,
const std::function< bool(const QgsPointXY &) > &  acceptPoint,
unsigned long  seed = 0,
QgsFeedback feedback = nullptr,
int  maxTriesPerPoint = 0 
)
static

Returns a list of count random points generated inside a polygon geometry (if acceptPoint is specified, and restrictive, the number of points returned may be less than count).

Optionally, a specific random seed can be used when generating points. If seed is 0, then a completely random sequence of points will be generated.

The acceptPoint function is used to filter result candidates. If the function returns false, then the point will not be accepted and another candidate generated.

The optional feedback argument can be used to provide cancellation support during the point generation.

When acceptPoint is specified, maxTriesPerPoint defines how many attempts to perform before giving up generating a point.

Since
QGIS 3.10

Definition at line 1058 of file qgsinternalgeometryengine.cpp.

◆ taperedBuffer()

QgsGeometry QgsInternalGeometryEngine::taperedBuffer ( double  startWidth,
double  endWidth,
int  segments 
) const

Calculates a tapered width buffer for a (multi)curve geometry.

The buffer begins at a width of startWidth at the start of each curve, and ends at a width of endWidth. Note that unlike QgsGeometry::buffer() methods, startWidth and endWidth are the diameter of the buffer at these points, not the radius.

The segments argument specifies the number of segments to approximate quarter-circle curves in the buffer.

Non (multi)curve input geometries will return a null output geometry.

Since
QGIS 3.2

Definition at line 1009 of file qgsinternalgeometryengine.cpp.

◆ variableWidthBuffer()

QgsGeometry QgsInternalGeometryEngine::variableWidthBuffer ( int  segments,
const std::function< std::unique_ptr< double[] >(const QgsLineString *line) > &  widthFunction 
) const

Calculates a variable width buffer for a (multi)curve geometry.

The width of the buffer at each node in the input linestrings is calculated by calling the specified widthFunction, which must return an array of the buffer widths for every node in the line.

The segments argument specifies the number of segments to approximate quarter-circle curves in the buffer.

Non (multi)curve input geometries will return a null output geometry.

Since
QGIS 3.2

Definition at line 903 of file qgsinternalgeometryengine.cpp.

◆ variableWidthBufferByM()

QgsGeometry QgsInternalGeometryEngine::variableWidthBufferByM ( int  segments) const

Calculates a variable width buffer using the m-values from a (multi)line geometry.

The segments argument specifies the number of segments to approximate quarter-circle curves in the buffer.

Non (multi)line input geometries will return a null output geometry.

Since
QGIS 3.2

Definition at line 1042 of file qgsinternalgeometryengine.cpp.


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