WPF中的EllipseGeometry里面的单位是什么？

Question

                                <GeometryGroup>
                                    <EllipseGeometry Center="20,20" RadiusX="30" RadiusY="30"></EllipseGeometry>
                                    <EllipseGeometry Center="10,10" RadiusX="5" RadiusY="5"></EllipseGeometry>
                                    <EllipseGeometry Center="10,10" RadiusX="1" RadiusY="1"></EllipseGeometry>
                                </GeometryGroup>
这里面的单位是什么？

Answer 1

http://msdn.microsoft.com/zh-cn/library/system.windows.media.ellipsegeometry(VS.95).aspx

Answer 2

<GeometryDrawing.Geometry>
    <GeometryGroup>
        <EllipseGeometry Center="20,20" RadiusX="30" RadiusY="30"></EllipseGeometry>
        <EllipseGeometry Center="10,10" RadiusX="5" RadiusY="5"></EllipseGeometry>
        <EllipseGeometry Center="10,10" RadiusX="1" RadiusY="1"></EllipseGeometry>
    </GeometryGroup>
</GeometryDrawing.Geometry>
怎么这里不以像素，怎么改后不是按照像素方式

Answer 3

就是书上讲DrawingBrush时，感觉这些gemetry元素在一起是不是要相互影响？