Ellipse(a) creates a
Circle with
diameter == ceil(2*a)
Ellipse(a,b) creates an
Ellipse with
horizontal axis == ceil(2*a) and vertical axis == ceil(2*b)
Ellipse(a,b,power) generates a superEllipse according to the
geometric formula (x./a).^power + (y./b).^power < 1
Ellipse(a,b,horpow,verpow) generates a generalized superEllipse according
to the geometric formula(x./a).^horpow + (y./b).^verpow < 1
For more info on superEllipses, see
http://en.wikipedia.org/wiki/SuperEllipse
Ellipse returns a (tighly-fitting) boolean matrix which is true for all
points on the surface of the
Ellipse and false elsewhere
Psychtoolbox/PsychOneliners/Ellipse.m