Position/scale Xamarin.Forms.Shapes PathGeometry as clipping path - xamarin

I'm playing with the new Shapes feature in Xamarin.Forms. I'm trying to clip an image:
<Image.Clip>
<PathGeometry
Figures="M0,0V517.87c0,25.53,107.53,46.22,240.16,46.22s240.17-20.69,240.17-46.22V0Z" />
</Image.Clip>
But the geometry as is, is too big; so I need to scale / move the geometry. Would it be possible?
Thanks

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I have a MeshBasicMaterial which has a planegeomatry.the material is around the plane like an outline and will be green initially.i have a clock in the app.i need to reduce the length of the outline every seconds to alert user their time is running out.so the outline will flow from top of the plane clockwise fading and disappear when the time runs out.hope you get the idea.now can anyone help me how to achieve this.
One way to solve this: create a ring geometry and animate its property thetaLength using animejs or tweenjs.
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First I am explaining the above image. Image is marking with 1, 2 and 3.
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2 - This is the rectangle shape.
3 - This is the circle shape (draw with destination-in global composite operation).
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For details -
1) http://threejs.org/docs/#Reference/Constants/Materials
2) http://threejs.org/examples/#webgl_materials_blending
3) http://threejs.org/examples/#webgl_materials_blending_custom
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If you show as part of the code, it would be good to give more precision. But anything, just comment here!

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