qwt_dimap.h

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/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
 * 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_DIMAP_H
#define QWT_DIMAP_H

#include "qwt_global.h"
#include "qwt_math.h"

/*!
  \brief Map a double interval into an integer interval

  The QwtDiMap class maps an interval of type double into an interval of
  type int. It consists
  of two intervals D = [d1, d2] (double) and I = [i1, i2] (int), which are
  specified with the QwtDiMap::setDblRange and QwtDiMap::setIntRange
  members. The point d1 is mapped to the point i1, and d2 is mapped to i2. 
  Any point inside or outside D can be mapped to a point inside or outside
  I using QwtDiMap::transform or QwtDiMap::limTransform or vice versa
  using QwtPlot::invTransform. D can be scaled linearly or
  logarithmically, as specified with QwtDiMap::setDblRange.

  <b>Usage</b>
\verbatim
#include <qwt_dimap.h>

QwtDiMap map;
int ival;
double dval;

map.setDblRange(0.0, 3.1415);   // Assign an interval of type double with
                // linear mapping
map.setIntRange(0,100);         // Assign an integer interval

ival = map.transform(1.0);      // obtain integer value corresponding to 1.0
dval = map.invTransform(77);    // obtain double value corresponding to 77
\endverbatim
*/

class QWT_EXPORT QwtDiMap
{
public:
    QwtDiMap();
    QwtDiMap(int i1, int i2, double d1, double d2, bool lg = FALSE);
    ~QwtDiMap();

    bool contains(double x) const;
    bool contains(int x) const;

    void setIntRange(int i1, int i2);
    void setDblRange(double d1, double d2, bool lg = FALSE);

    int transform(double x) const;
    double invTransform(int i) const;

    int limTransform(double x) const;
    double xTransform(double x) const;

    inline double d1() const;
    inline double d2() const;
    inline int i1() const;
    inline int i2() const;
    inline bool logarithmic() const;

    QT_STATIC_CONST double LogMin;
    QT_STATIC_CONST double LogMax;

private:
    void newFactor();   

    double d_x1, d_x2;  // double interval boundaries
    int d_y1, d_y2;     // integer interval boundaries
    double d_cnv;       // conversion factor
    bool d_log;     // logarithmic scale?
};

/*!
    \return the first border of the double interval
*/
inline double QwtDiMap::d1() const 
{
    return d_x1;
}

/*!
    \return the second border of the double interval
*/
inline double QwtDiMap::d2() const 
{
    return d_x2;
}

/*!
    \return the second border of the integer interval
*/
inline int QwtDiMap::i1() const 
{
    return d_y1;
}

/*!
    \return the second border of the integer interval
*/
inline int QwtDiMap::i2() const 
{
    return d_y2;
}

/*!
    \return TRUE if the double interval is scaled logarithmically
*/
inline bool QwtDiMap::logarithmic() const 
{
    return d_log;
}

/*!
  \brief Transform a point in double interval into an point in the
    integer interval

  \param x value
  \return
  <dl>
  <dt>linear mapping:<dd>rint(i1 + (i2 - i1) / (d2 - d1) * (x - d1))
  <dt>logarithmic mapping:<dd>rint(i1 + (i2 - i1) / log(d2 / d1) * log(x / d1))
  </dl>
  \warning The specified point is allowed to lie outside the intervals. If you
  want to limit the returned value, use QwtDiMap::limTransform.
*/
inline int QwtDiMap::transform(double x) const
{
    if (d_log)
        return d_y1 + qRound((log(x) - d_x1) * d_cnv);
    else
        return d_y1 + qRound((x - d_x1) * d_cnv);
}

#endif