Transform class
The Transform class provides its subclasses with
the ability to handle coordinate transformations.
Synopsis
Header file: ncarg/hlu/Transform.h
Class name: transformClass
Class pointer: <Not referenceable>
Fortran class function: <Not referenceable>
Superclass: View
Composite classes: <None>
Resources
Local resources
+---------------------------------------------------------------+
| Transform Resource Set |
|---------------------------------------------------------------|
| NAME TYPE ACCESS |
| CLASS DEFAULT |
|===============================================================|
| tfPlotManagerOn NhlTBoolean RCG |
| TfPlotManagerOn True |
+---------------------------------------------------------------+
Composite resources
The Transform object class has no composite class resources.
Superclass resources
For any Transform class object, you can set all
resources defined by the Transform class's
superclasses, including:
Description
Objects that belong to the Transform class are viewable
objects that support transformations between data
coordinate space and NDC space. A
Transform object may be called simply a transform.
Subclasses of the Transform class may contain the
PlotManager class as a composite
class member. A transform instantiated with a active
PlotManager is is known as a plot object.
All subclasses of Transform include as a composite
class member at least one subclass of the TransObj
class to perform the forward and reverse transformations. There are
currently three TransObj classes available to the
subclasses of Transform:
- The LogLinTransObj provides transformations to and
from a linear or logarithmic coordinate space. Either or both coordinate
axes may be logarithmic.
- The IrregularTransObj provides transformations to
and from an irregularly-gridded rectangular coordinate space.
- The MapTransObj provides transformations to and from
any of 10 different standard map projections.
The Transform subclasses may include any or all of
these available TransObj class members.
Transform defines the following support functions:
-
NhlNDCToData
-
Given arrays containing the X and Y coordinates of points in NDC space
the NhlNDCToData function returns arrays containing the
X and Y coordinates of the same points in data coordinate space.
-
NhlDataToNDC
-
Given arrays containing the X and Y coordinates of points in data
coordinate space the NhlDataToNDC function returns
arrays containing the X and Y coordinates of the same points in NDC space.
-
NhlDataPolyline
-
Given arrays containing the X and Y coordinates of points in data
coordinate space the NhlDataPolyine function outputs
an immediate-mode polyline connecting each of the points.
-
NhlNDCPolyline
-
Given arrays containing the X and Y coordinates of points in NDC space
the NhlNDCPolyine function outputs an immediate-mode
polyline connecting each of the points.
-
NhlIsTransform
-
This function just determines if a given object id identifies a
Transform class object.
The following support functions are used to add overlays
and annotations to plot objects, and also to remove them.
-
NhlAddOverlay
-
The NhlAddOverlay function adds transform as an
overlay of a base plot.
-
NhlRemoveOverlay
-
The NhlRemoveOverlay function removes an overlay
from a base plot.
-
NhlAddAnnotation
-
The NhlAddAnnotation function adds an arbitrary
user-created View object to a plot object as an
annotation, returning the id of a controlling
AnnoManager object.
-
NhlRemoveAnnotation
-
The NhlRemoveAnnotation function removes the association
between a user-created View object and the
plot object to which it belongs as an annotation.
It destroys the controlling AnnoManager object.
Status
1: The status of the immediate mode drawing
functions, DataPolyline and
NDCPolyline, is not yet resolved.
See also
Copyright
Copyright 1987,1988,1989,1991,1993,1994,1995
University Corporation for Atmospheric Research
All Rights Reserved
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$Revision: 1.21 $ $Date: 1995/07/26 23:30:43 $