astEllipsePars

Returns the geometric parameters of an Ellipse

Description:

This function returns the geometric parameters describing the supplied ellipse.

Synopsis

void astEllipsePars( AstEllipse this, double centre[2], double a, double b, double angle, double p1[2], double p2[2] )

Parameters:

this
Pointer to the Region.
centre
The coordinates of the Ellipse centre are returned in this arrays.
a
Returned holding the half-length of the first axis of the ellipse.
b
Returned holding the half-length of the second axis of the ellipse.
angle
If the coordinate system in which the Ellipse is defined has axes (X,Y), then " angle" is returned holding the angle from the positive direction of the Y axis to the first axis of the ellipse, in radians. Positive rotation is in the same sense as rotation from the positive direction of Y to the positive direction of X.
p1
An array in which to return the coordinates at one of the two ends of the first axis of the ellipse. A NULL pointer can be supplied if these coordinates are not needed.
p2
An array in which to return the coordinates at one of the two ends of the second axis of the ellipse. A NULL pointer can be supplied if these coordinates are not needed.

Notes: