WCCoordinateHandler.h

Classes

WCCoordinateHandler -- Base class defining a set of transformations for WorldCanvas coordinates. (full description)

class WCCoordinateHandler

Interface

Public Members

WCCoordinateHandler()

virtual Bool linToWorld(Vector<Double> & world, const Vector<Double> & lin) = 0

virtual Bool linToWorld(Matrix<Double> & world, Vector<Bool> & failures, const Matrix<Double> & lin)

virtual Bool worldToLin(Vector<Double> & lin, const Vector<Double> & world) = 0

virtual Bool worldToLin(Matrix<Double> & lin, Vector<Bool> & failures, const Matrix<Double> & world)

virtual uInt nWorldAxes() const = 0

virtual Vector<String> worldAxisNames() = 0

virtual Vector<String> worldAxisUnits() = 0

virtual ~WCCoordinateHandler()

Description

Prerequisite

• Understanding of non-linear World Coordinate Systems

Etymology

Synopsis

This class defines an interface between the WorldCanvas, which uses coordinate transformations for various reasons, and the derived class that implements these coordinate transformations.

The designer of the derived class must write the Vector<Double> versions of linToWorld and worldToLin as described in detail below. It is also recommended that the Matrix<Double> versions of linToWorld and worldToLin be written to maximize efficiency.

Motivation

• Needed to plug in a user-programmable coordinate transformation functions into the world canvas in a convenient way.
• Wanted to bundle these transformations into a class to follow OO methods.

  Example

  DefaultWCCoordinateHandler

  Member Description

  WCCoordinateHandler()

  Default Constructor Required

  virtual Bool linToWorld(Vector<Double> & world, const Vector<Double> & lin) = 0

  transform the lin point (2-dimensional) into a world coordinate (N-dimensional), returning False if the coordinate could not be transformed. Derived classes should override.

  virtual Bool linToWorld(Matrix<Double> & world, Vector<Bool> & failures, const Matrix<Double> & lin)

  Batch transformation where each row of lin is a coordinate that is transformed into each row of world. On input, if the i'th position in the failures vector is true, the i'th transformation is not attempted. If the j'th transformation fails, the j'th position in the failures vector will be set. The return value is True only when the failures vector has no position set to True; This function is implemented in this base class by making repeated calls to the Vector version of linToWorld.

  virtual Bool worldToLin(Vector<Double> & lin, const Vector<Double> & world) = 0

  transform the world point (N-dimensional) into a lin coordinate (2-dimensional), returning False if the coordinate could not be transformed. Derived classes should override.

  virtual Bool worldToLin(Matrix<Double> & lin, Vector<Bool> & failures, const Matrix<Double> & world)

  Batch transformation where each row of world is a coordinate that is transformed into each row of lin. On input, if the i'th position in the failures vector is true, the i'th transformation is not attempted. If the j'th transformation fails, the j'th position in the failures vector will be set. The return value is True only when the failures vector has no position set to True; This function is implemented in this base class by making repeated calls to the Vector version of worldToLin.

  virtual uInt nWorldAxes() const = 0

  Return the number of axes in the world coordinates

  virtual Vector<String> worldAxisNames() = 0
  virtual Vector<String> worldAxisUnits() = 0

  Routines that give the axes names and the unit.

  virtual ~WCCoordinateHandler()

  Destructor