Something was lost in translation, I think. Wide ellipses in X aren't specified as being drawn with a circular pen. Instead, they are specified as being drawn by moving a linear pen along the ellipse while holding it perpendicular to the ellipse. This turns out to be a really bad specification; the ellipses have these funny "hooks" and it really does require a nasty high-order polynomial to describe the inner and outer hull of the wide ellipse to the exact pixelization X requires. Worse are dashed ellipses, which turn out to be intractable altogether.