qwt_spline_polynomial.h

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/******************************************************************************
 * 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
 *****************************************************************************/

#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