Create a Ellipse
A Ellipse is a Region which represents a elliptical area within the supplied 2-dimensional Frame.
"
form"
is zero, this array should contain the coordinates of one
of the four points where an axis of the ellipse crosses the circumference of
the ellipse. If "
form"
is one, it should contain the lengths of semi-major
and semi-minor axes of the ellipse, given as geodesic distances within the
Frame. "
form"
is zero, this array should
containing the coordinates at some other point on the circumference of the ellipse,
distinct from "
point1"
. If "
form"
is one, the first element of this array
should hold the angle between the second axis of the Frame and the first ellipse
axis (i.e. the ellipse axis which is specified first in the "
point1"
array),
and the second element will be ignored. The angle should be given in radians,
measured positive in the same sense as rotation from the positive direction of the
second Frame axis to the positive direction of the first Frame axis. "
uncertainty"
Region so that it is centred at the boundary point being considered. The
area covered by the shifted uncertainty Region then represents the uncertainty
in the boundary position. The uncertainty is assumed to be the same for all
points.
If supplied, the uncertainty Region must be of a class for which all instances are centro-symetric (e.g. Box, Circle, Ellipse, etc.) or be a Prism containing centro-symetric component Regions. A deep copy of the supplied Region will be taken, so subsequent changes to the uncertainty Region using the supplied pointer will have no effect on the created Ellipse. Alternatively, a NULL Object pointer may be supplied, in which case a default uncertainty is used equivalent to a box 1.0E-6 of the size of the Ellipse being created.
The uncertainty Region has two uses: 1) when the astOverlap function compares two Regions for equality the uncertainty Region is used to determine the tolerance on the comparison, and 2) when a Region is mapped into a different coordinate system and subsequently simplified (using astSimplify), the uncertainties are used to determine if the transformed boundary can be accurately represented by a specific shape of Region.
"
printf"
format specifiers identified by "
%"
symbols in the
normal way. "
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). A null Object pointer (AST__NULL) will be returned if this function is invoked with the AST error status set, or if it should fail for any reason.