QwtTransform Class Reference

A transformation between coordinate systems. More...

#include <qwt_transform.h>

Inheritance diagram for QwtTransform:

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

bounded()

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.

invTransform()

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.

transform()

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.