QwtSplineLocal(3) Qwt User's Guide QwtSplineLocal(3) NAME QwtSplineLocal - A spline with C1 continuity. SYNOPSIS #include Inherits QwtSplineC1. Public Types enum Type { Cardinal, ParabolicBlending, Akima, PChip } Spline interpolation type. Public Member Functions QwtSplineLocal (Type type) Constructor. virtual ~QwtSplineLocal () Destructor. Type type () const virtual uint locality () const override virtual QPainterPath painterPath (const QPolygonF &) const override Interpolate a curve with Bezier curves. virtual QVector< QLineF > bezierControlLines (const QPolygonF &) const override Interpolate a curve with Bezier curves. virtual QVector< QwtSplinePolynomial > polynomials (const QPolygonF &) const override Calculate the interpolating polynomials for a non parametric spline. virtual QVector< double > slopes (const QPolygonF &) const override Find the first derivative at the control points. 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. Definition at line 24 of file qwt_spline_local.h. Member Enumeration Documentation 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. Definition at line 34 of file qwt_spline_local.h. Constructor & Destructor Documentation QwtSplineLocal::QwtSplineLocal (Type type) Constructor. Parameters type Spline type, specifying the type of interpolation See also type() Definition at line 450 of file qwt_spline_local.cpp. Member Function Documentation QVector< QLineF > QwtSplineLocal::bezierControlLines (const QPolygonF & points) const [override], [virtual] 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. Definition at line 502 of file qwt_spline_local.cpp. uint QwtSplineLocal::locality () const [override], [virtual] 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. Definition at line 552 of file qwt_spline_local.cpp. QPainterPath QwtSplineLocal::painterPath (const QPolygonF & points) const [override], [virtual] 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. Definition at line 482 of file qwt_spline_local.cpp. QVector< QwtSplinePolynomial > QwtSplineLocal::polynomials (const QPolygonF & points) const [override], [virtual] 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. Definition at line 537 of file qwt_spline_local.cpp. QVector< double > QwtSplineLocal::slopes (const QPolygonF & points) const [override], [virtual] 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. Definition at line 521 of file qwt_spline_local.cpp. QwtSplineLocal::Type QwtSplineLocal::type () const Returns Spline type, specifying the type of interpolation Definition at line 468 of file qwt_spline_local.cpp. Author Generated automatically by Doxygen for Qwt User's Guide from the source code. Version 6.2.0 Sun Jul 18 2021 QwtSplineLocal(3)