>Psychtoolbox>PsychOneliners

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