Shape: Ellipse

The ellipse is generated, as most shapes are, on a square canvas to the maximum of either horizontal or vertical measurement up to the composite canvas size.

Ellipses are drawn as circles and then squeezed into shape.
For DVD, which has no "square" pixels in any of its resolution and aspect ratio combinations, "circles" actually are rendered as ellipses.
Compare the generated shape with the composited shape and you can see the horizontal squeezing.

Generating shapes in this manner allows us to change the line thickness proportionally over the entire shape, resulting in the same shape on the inside and outside edges (compare to GDI generated shapes with thick lines).