qwt_spline_polynomial.h

/******************************************************************************
 * Qwt Widget Library
 * Copyright (C) 1997   Josef Wilgen
 * Copyright (C) 2002   Uwe Rathmann
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the Qwt License, Version 1.0
 *
 * Modified by ChenZongYan in 2024 <czy.t@163.com>
 *   Summary of major modifications (see ChangeLog.md for full history):
 *   1. CMake build system & C++11 throughout.
 *   2. Core panner/ zoomer refactored:
 *        - QwtPanner → QwtCachePanner (pixmap-cache version)
 *        - New real-time QwtPlotPanner derived from QwtPicker.
 *   3. Zoomer supports multi-axis.
 *   4. Parasite-plot framework:
 *        - QwtFigure, QwtPlotParasiteLayout, QwtPlotTransparentCanvas,
 *        - QwtPlotScaleEventDispatcher, built-in pan/zoom on axis.
 *   5. New picker: QwtPlotSeriesDataPicker (works with date axis).
 *   6. Raster & color-map extensions:
 *        - QwtGridRasterData (2-D table + interpolation)
 *        - QwtLinearColorMap::stopColors(), stopPos() API rename.
 *   7. Bar-chart: expose pen/brush control.
 *   8. Amalgamated build: single QwtPlot.h / QwtPlot.cpp pair in src-amalgamate.
 *****************************************************************************/
 
#ifndef QWT_SPLINE_POLYNOMIAL_H
#define QWT_SPLINE_POLYNOMIAL_H
 
#include "qwt_global.h"
 
#include <qpoint.h>
#include <qmetatype.h>
 
class QWT_EXPORT QwtSplinePolynomial
{
public:
    QwtSplinePolynomial(double c3 = 0.0, double c2 = 0.0, double c1 = 0.0);
 
    bool operator==(const QwtSplinePolynomial&) const;
    bool operator!=(const QwtSplinePolynomial&) const;
 
    double valueAt(double x) const;
    double slopeAt(double x) const;
    double curvatureAt(double x) const;
 
    static QwtSplinePolynomial fromSlopes(const QPointF& p1, double m1, const QPointF& p2, double m2);
 
    static QwtSplinePolynomial fromSlopes(double x, double y, double m1, double m2);
 
    static QwtSplinePolynomial fromCurvatures(const QPointF& p1, double cv1, const QPointF& p2, double cv2);
 
    static QwtSplinePolynomial fromCurvatures(double dx, double dy, double cv1, double cv2);
 
public:
    double c3;
 
    double c2;
 
    double c1;
};
 
Q_DECLARE_TYPEINFO(QwtSplinePolynomial, Q_MOVABLE_TYPE);
Q_DECLARE_METATYPE(QwtSplinePolynomial)
 
 
inline QwtSplinePolynomial::QwtSplinePolynomial(double a3, double a2, double a1) : c3(a3), c2(a2), c1(a1)
{
}
 
inline bool QwtSplinePolynomial::operator==(const QwtSplinePolynomial& other) const
{
    return (c3 == other.c3) && (c2 == other.c2) && (c1 == other.c1);
}
 
inline bool QwtSplinePolynomial::operator!=(const QwtSplinePolynomial& other) const
{
    return (!(*this == other));
}
 
inline double QwtSplinePolynomial::valueAt(double x) const
{
    return (((c3 * x) + c2) * x + c1) * x;
}
 
inline double QwtSplinePolynomial::slopeAt(double x) const
{
    return (3.0 * c3 * x + 2.0 * c2) * x + c1;
}
 
inline double QwtSplinePolynomial::curvatureAt(double x) const
{
    return 6.0 * c3 * x + 2.0 * c2;
}
 
inline QwtSplinePolynomial QwtSplinePolynomial::fromSlopes(const QPointF& p1, double m1, const QPointF& p2, double m2)
{
    return fromSlopes(p2.x() - p1.x(), p2.y() - p1.y(), m1, m2);
}
 
inline QwtSplinePolynomial QwtSplinePolynomial::fromSlopes(double dx, double dy, double m1, double m2)
{
    const double c2 = (3.0 * dy / dx - 2 * m1 - m2) / dx;
    const double c3 = ((m2 - m1) / dx - 2.0 * c2) / (3.0 * dx);
 
    return QwtSplinePolynomial(c3, c2, m1);
}
 
inline QwtSplinePolynomial QwtSplinePolynomial::fromCurvatures(const QPointF& p1, double cv1, const QPointF& p2, double cv2)
{
    return fromCurvatures(p2.x() - p1.x(), p2.y() - p1.y(), cv1, cv2);
}
 
inline QwtSplinePolynomial QwtSplinePolynomial::fromCurvatures(double dx, double dy, double cv1, double cv2)
{
    const double c3 = (cv2 - cv1) / (6.0 * dx);
    const double c2 = 0.5 * cv1;
    const double c1 = dy / dx - (c3 * dx + c2) * dx;
 
    return QwtSplinePolynomial(c3, c2, c1);
}
 
#ifndef QT_NO_DEBUG_STREAM
 
class QDebug;
QWT_EXPORT QDebug operator<<(QDebug, const QwtSplinePolynomial&);
 
#endif
 
#endif