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astZoomMap
Create a ZoomMap
Description:
This function creates a new
ZoomMap and optionally initialises its attributes.
A ZoomMap is a Mapping which "
zooms"
a set of points about the origin by
multiplying all coordinate values by the same scale factor (the inverse
transformation is performed by dividing by this scale factor).
Synopsis
AstZoomMap
astZoomMap( int ncoord, double
zoom, const char options,
... )
Parameters:
ncoord
The number of coordinate values for each point to be
transformed (i.e. the number of dimensions of the space in which the points will
reside). The same number is applicable to both input and output points.
zoom
Initial scale factor by which coordinate values should be multiplied (by the forward
transformation) or divided (by the inverse transformation). This factor may
subsequently be changed via the ZoomMap
’
s
Zoom attribute. It may be positive or
negative, but should not be zero.
options
Pointer to a null-terminated string
containing an optional comma-separated list of attribute assignments to be used for
initialising the new ZoomMap. The syntax used is identical to that for the
astSet
function and may include
"
printf
"
format specifiers identified by
"
%
"
symbols in the
normal way.
...
If the "
options"
string contains "
%"
format specifiers,
then an optional list of additional arguments may follow it in order to supply
values to be substituted for these specifiers. The rules for supplying these are
identical to those for the astSet function (and for the C "
printf"
function).
Returned Value
astZoomMap()
A pointer to the new ZoomMap.
Notes:
Status Handling
The protected interface to this function includes an
extra parameter at the end of the parameter list descirbed above. This
parameter is a pointer to the integer inherited status variable: "
int
status"
.
Copyright (C) 2021 East Asian Observatory
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A Library for Handling
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