QwtTransform - Man Page
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 ) );
Definition at line 35 of file qwt_transform.h.
Member Function Documentation
double QwtTransform::bounded (double value) 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.
Definition at line 33 of file qwt_transform.cpp.
virtual double QwtTransform::invTransform (double value) 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 (double value) 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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