143 lines
3.5 KiB
C
143 lines
3.5 KiB
C
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/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
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* Qwt Widget Library
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* Copyright (C) 1997 Josef Wilgen
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* Copyright (C) 2002 Uwe Rathmann
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the Qwt License, Version 1.0
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*****************************************************************************/
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#ifndef QWT_TRANSFORM_H
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#define QWT_TRANSFORM_H
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#include "qwt_global.h"
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/*!
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\brief A transformation between coordinate systems
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QwtTransform manipulates values, when being mapped between
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the scale and the paint device coordinate system.
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A transformation consists of 2 methods:
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- transform
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- invTransform
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where one is is the inverse function of the other.
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When p1, p2 are the boundaries of the paint device coordinates
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and s1, s2 the boundaries of the scale, QwtScaleMap uses the
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following calculations:
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- p = p1 + ( p2 - p1 ) * ( T( s ) - T( s1 ) / ( T( s2 ) - T( s1 ) );
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- s = invT ( T( s1 ) + ( T( s2 ) - T( s1 ) ) * ( p - p1 ) / ( p2 - p1 ) );
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*/
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class QWT_EXPORT QwtTransform
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{
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public:
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QwtTransform();
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virtual ~QwtTransform();
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/*!
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Modify value to be a valid value for the transformation.
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The default implementation does nothing.
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*/
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virtual double bounded( double value ) const;
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/*!
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Transformation function
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\param value Value
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\return Modified value
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\sa invTransform()
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*/
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virtual double transform( double value ) const = 0;
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/*!
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Inverse transformation function
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\param value Value
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\return Modified value
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\sa transform()
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*/
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virtual double invTransform( double value ) const = 0;
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//! Virtualized copy operation
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virtual QwtTransform *copy() const = 0;
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};
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/*!
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\brief Null transformation
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QwtNullTransform returns the values unmodified.
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*/
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class QWT_EXPORT QwtNullTransform: public QwtTransform
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{
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public:
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QwtNullTransform();
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virtual ~QwtNullTransform();
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virtual double transform( double value ) const;
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virtual double invTransform( double value ) const;
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virtual QwtTransform *copy() const;
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};
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/*!
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\brief Logarithmic transformation
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QwtLogTransform modifies the values using log() and exp().
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\note In the calculations of QwtScaleMap the base of the log function
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has no effect on the mapping. So QwtLogTransform can be used
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for log2(), log10() or any other logarithmic scale.
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*/
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class QWT_EXPORT QwtLogTransform: public QwtTransform
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{
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public:
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QwtLogTransform();
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virtual ~QwtLogTransform();
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virtual double transform( double value ) const;
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virtual double invTransform( double value ) const;
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virtual double bounded( double value ) const;
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virtual QwtTransform *copy() const;
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#if QT_VERSION >= 0x050400
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static const double LogMin;
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static const double LogMax;
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#else
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QT_STATIC_CONST double LogMin;
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QT_STATIC_CONST double LogMax;
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#endif
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};
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/*!
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\brief A transformation using pow()
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QwtPowerTransform preserves the sign of a value.
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F.e. a transformation with a factor of 2
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transforms a value of -3 to -9 and v.v. Thus QwtPowerTransform
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can be used for scales including negative values.
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*/
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class QWT_EXPORT QwtPowerTransform: public QwtTransform
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{
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public:
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QwtPowerTransform( double exponent );
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virtual ~QwtPowerTransform();
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virtual double transform( double value ) const;
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virtual double invTransform( double value ) const;
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virtual QwtTransform *copy() const;
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private:
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const double d_exponent;
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};
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#endif
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