A spline with C1 continuity. More...

#include <qwt_spline_local.h>

Inheritance diagram for QwtSplineLocal:

Public Types
enum	Type { Cardinal , ParabolicBlending , Akima , PChip }
	Spline interpolation type. More...

Public Types inherited from QwtSpline
enum	BoundaryType { ConditionalBoundaries , PeriodicPolygon , ClosedPolygon }
	Boundary type specifying the spline at its endpoints. More...

enum	BoundaryPosition { AtBeginning , AtEnd }
	position of a boundary condition More...

enum	BoundaryCondition { Clamped1 , Clamped2 , Clamped3 , LinearRunout }
	Boundary condition. More...

Public Member Functions
	QwtSplineLocal (Type type)
	Constructor with spline type.

	~QwtSplineLocal () override
	Destructor.

Type	type () const
	Get spline type.

virtual uint	locality () const override
	Get locality (number of points used for calculation)

virtual QPainterPath	painterPath (const QPolygonF &) const override
	Get painter path from polygon.

virtual QVector< QLineF >	bezierControlLines (const QPolygonF &) const override
	Get Bezier control lines.

virtual QVector< QwtSplinePolynomial >	polynomials (const QPolygonF &) const override
	Get polynomials from polygon.

virtual QVector< double >	slopes (const QPolygonF &) const override
	Get slopes at control points.

Public Member Functions inherited from QwtSplineC1
	QwtSplineC1 ()
	Constructor.

	~QwtSplineC1 () override
	Destructor.

virtual QPolygonF	equidistantPolygon (const QPolygonF &, double distance, bool withNodes) const override
	Find an interpolated polygon with "equidistant" points.

virtual double	slopeAtBeginning (const QPolygonF &, double slopeNext) const
	Calculate the slope at the beginning of the spline.

virtual double	slopeAtEnd (const QPolygonF &, double slopeBefore) const
	Calculate the slope at the end of the spline.

Public Member Functions inherited from QwtSplineG1
	QwtSplineG1 ()
	Constructor.

	~QwtSplineG1 () override
	Destructor.

Public Member Functions inherited from QwtSplineInterpolating
	QwtSplineInterpolating ()
	Constructor.

	~QwtSplineInterpolating () override
	Destructor.

virtual QPolygonF	polygon (const QPolygonF &, double tolerance) const override
	Interpolate a curve by a polygon.

Public Member Functions inherited from QwtSpline
	QwtSpline ()
	Constructor.

virtual	~QwtSpline ()
	Destructor.

void	setParametrization (int type)
	Set parametrization by type.

void	setParametrization (QwtSplineParametrization *)
	Set parametrization object.

const QwtSplineParametrization *	parametrization () const
	Get parametrization.

void	setBoundaryType (BoundaryType)
	Set boundary type.

BoundaryType	boundaryType () const
	Get boundary type.

void	setBoundaryValue (BoundaryPosition, double value)
	Set boundary value.

double	boundaryValue (BoundaryPosition) const
	Get boundary value.

void	setBoundaryCondition (BoundaryPosition, int condition)
	Set boundary condition.

int	boundaryCondition (BoundaryPosition) const
	Get boundary condition.

void	setBoundaryConditions (int condition, double valueBegin=0.0, double valueEnd=0.0)
	Set boundary conditions for both ends.

Detailed Description

A spline with C1 continuity.

QwtSplineLocal offers several standard algorithms for interpolating a curve with polynomials having C1 continuity at the control points. All algorithms are local in a sense, that changing one control point only few polynomials.

Member Enumeration Documentation

◆ Type

enum QwtSplineLocal::Type

Spline interpolation type.

All type of spline interpolations are lightweight algorithms calculating the slopes at a point by looking 1 or 2 points back and ahead.

Enumerator
Cardinal	A cardinal spline The cardinal spline interpolation is a very cheap calculation with a locality of 1.
ParabolicBlending	Parabolic blending is a cheap calculation with a locality of 1. Sometimes it is also called Cubic Bessel interpolation.
Akima	The algorithm of H.Akima is a calculation with a locality of 2.
PChip	Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) is an algorithm that is popular because of being offered by MATLAB. It preserves the shape of the data and respects monotonicity. It has a locality of 1.

Constructor & Destructor Documentation

◆ QwtSplineLocal()

QwtSplineLocal::QwtSplineLocal ( Type type )

explicit

Constructor with spline type.

Constructor.

Parameters

[in] type Spline type, specifying the type of interpolation

See also: type()

Member Function Documentation

◆ bezierControlLines()

QVector< QLineF > QwtSplineLocal::bezierControlLines ( const QPolygonF & points ) const

overridevirtual

Get Bezier control lines.

Interpolate a curve with Bezier curves.

Interpolates a polygon piecewise with cubic Bezier curves and returns the 2 control points of each curve as QLineF.

Parameters

points Control points

Returns: Control points of the interpolating Bezier curves

Reimplemented from QwtSplineC1.

◆ locality()

uint QwtSplineLocal::locality ( ) const

overridevirtual

Get locality (number of points used for calculation)

Get the locality of the spline interpolation.

The locality of an spline interpolation identifies how many adjacent polynomials are affected, when changing the position of one point.

The Cardinal, ParabolicBlending and PChip algorithms have a locality of 1, while the Akima interpolation has a locality of 2.

Returns: 1 or 2.

Reimplemented from QwtSpline.

◆ painterPath()

QPainterPath QwtSplineLocal::painterPath ( const QPolygonF & points ) const

overridevirtual

Get painter path from polygon.

Interpolate a curve with Bezier curves.

Interpolates a polygon piecewise with cubic Bezier curves and returns them as QPainterPath.

Parameters

points Control points

Returns: Painter path, that can be rendered by QPainter

Reimplemented from QwtSplineC1.

◆ polynomials()

QVector< QwtSplinePolynomial > QwtSplineLocal::polynomials ( const QPolygonF & points ) const

overridevirtual

Get polynomials from polygon.

Calculate the interpolating polynomials for a non parametric spline.

Parameters

points Control points

Returns: Interpolating polynomials

Note: The x coordinates need to be increasing or decreasing; The implementation simply calls QwtSplineC1::polynomials(), but is intended to be replaced by a one pass calculation some day.

Reimplemented from QwtSplineC1.

◆ slopes()

QVector< double > QwtSplineLocal::slopes ( const QPolygonF & points ) const

overridevirtual

Get slopes at control points.

Find the first derivative at the control points.

Parameters

points Control nodes of the spline

Returns: Vector with the values of the 2nd derivate at the control points

Note: The x coordinates need to be increasing or decreasing

Implements QwtSplineC1.

◆ type()

QwtSplineLocal::Type QwtSplineLocal::type ( ) const

Get spline type.

Returns: Spline type, specifying the type of interpolation

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

/home/runner/work/QWT/QWT/src/plot/qwt_spline_local.h
/home/runner/work/QWT/QWT/src/plot/qwt_spline_local.cpp

Public Types

Public Member Functions

Detailed Description

Member Enumeration Documentation

◆ Type

Constructor & Destructor Documentation

◆ QwtSplineLocal()

Member Function Documentation

◆ bezierControlLines()

◆ locality()

◆ painterPath()

◆ polynomials()

◆ slopes()

◆ type()