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Description:
This function returns the axis values at the points that define the supplied
Region. The particular meaning of these points will depend on the type of class supplied,
as listed below under
" Applicability:
" .
Synopsis
void astGetRegionPoints( AstRegion
∗this, int maxpoint, int
maxcoord, int ∗npoint,
double ∗points
)
Parameters:
this
Pointer to the Region.
maxpoint
If zero,
the number of points needed to define the Region is returned in "
∗npoint" ,
but no axis values are returned and all other parameters are ignored. If not zero, the
supplied value should be the length of the second dimension of the " points" array. An
error is reported if the number of points needed to define the Region exceeds this
number.
maxcoord
The length of the first dimension of the " points" array. An
error is reported if the number of axes in the supplied Region exceeds this number.
npoint
A pointer to an integer in which to return the number of points defining the
Region.
points
The address of the first element in a 2-dimensional array of shape
" [maxcoord][maxpoint]" , in which to return the coordinate values at the positions
that define the Region. These are stored such that the value of coordinate number "
coord" for point number " point" is found in element " points[coord][point]"
.
Applicability
Region
All Regions have this attribute.
The
first returned position is the Box centre, and the second is a Box corner.
The first returned position is the Circle centre, and the second is
a point on the circumference.
Returns a value of zero for
"
∗npoint
"
and leaves the supplied array contents unchanged. To find the points defining a
CmpRegion, use this method on the component Regions, which can be accessed by invoking
astDecompose on the CmpRegion.
The first returned position is the Ellipse
centre. The second is the end of one of the axes of the ellipse. The third is some
other point on the circumference of the ellipse, distinct from the second point.
The first point corresponds to the lower bounds position, and the
second point corresponds to the upper bounds position. These are reversed to
indicate an extcluded interval rather than an included interval. See the Interval
constructor for more information.
Returns a value of zero for "
∗npoint"
and leaves the supplied array contents unchanged.
The positions
returned are those that were supplied when the PointList was constructed.
The positions returned are the vertex positions that were supplied
when the Polygon was constructed.
Returns a value of zero for "
∗npoint"
and leaves the supplied array contents unchanged. To find the points defining a Prism,
use this method on the component Regions, which can be accessed by invoking
astDecompose on the CmpRegion.
Notes:
-
If the coordinate system represented by the Region has been changed since it was first
created, the returned axis values refer to the new (changed) coordinate system, rather
than the original coordinate system. Note however that if the transformation from
original to new coordinate system is non-linear, the shape within the new coordinate
system may be distorted, and so may not match that implied by the name of the Region
subclass (Circle, Box, etc).
Copyright (C) 2021 East Asian Observatory
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- AST
A Library for Handling
World
Coordinate Systems
in Astronomy - Next→
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