See the Processing function ellipse():
        https://processing.org/reference/ellipse_.html

def ellipse(self, x, y, width, height, color):
        """
        See the Processing function ellipse():
        https://processing.org/reference/ellipse_.html
        """
        self.context.set_source_rgb(*color)
        self.context.save()
        self.context.translate(self.tx(x + (width / 2.0)), self.ty(y + (height / 2.0)))
        self.context.scale(self.tx(width / 2.0), self.ty(height / 2.0))
        self.context.arc(0.0, 0.0, 1.0, 0.0, 2 * math.pi)
        self.context.fill()
        self.context.restore()