NAME

       QwtTransform -

       A transformation between coordinate systems.

SYNOPSIS

       #include <qwt_transform.h>

       Inherited by QwtLogTransform, QwtNullTransform, and QwtPowerTransform.

   Public Member Functions
       QwtTransform ()
           Constructor.
       virtual ~QwtTransform ()
           Destructor.
       virtual double bounded (double value) const
       virtual double transform (double value) const =0
       virtual double invTransform (double value) const =0
       virtual QwtTransform * copy () const =0
           Virtualized copy operation.

Detailed Description

       A transformation between coordinate systems.

       QwtTransform manipulates values, when being mapped between the scale and the paint device
       coordinate system.

       A transformation consists of 2 methods:

       • transform

       • invTransform

       where one is is the inverse function of the other.

       When p1, p2 are the boundaries of the paint device coordinates and s1, s2 the boundaries
       of the scale, QwtScaleMap uses the following calculations:

       • p = p1 + ( p2 - p1 ) * ( T( s ) - T( s1 ) / ( T( s2 ) - T( s1 ) );

       • s = invT ( T( s1 ) + ( T( s2 ) - T( s1 ) ) * ( p - p1 ) / ( p2 - p1 ) );

Member Function Documentation

   double QwtTransform::bounded (doublevalue) const [virtual]
       Modify value to be a valid value for the transformation. The default implementation does
       nothing.

       Parameters:
           value Value to be bounded

       Returns:
           value unmodified

       Reimplemented in QwtLogTransform.

   virtual double QwtTransform::invTransform (doublevalue) const [pure virtual]
       Inverse transformation function

       Parameters:
           value Value

       Returns:
           Modified value

       See Also:
           transform()

       Implemented in QwtPowerTransform, QwtLogTransform, and QwtNullTransform.

   virtual double QwtTransform::transform (doublevalue) const [pure virtual]
       Transformation function

       Parameters:
           value Value

       Returns:
           Modified value

       See Also:
           invTransform()

       Implemented in QwtPowerTransform, QwtLogTransform, and QwtNullTransform.

Author

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