Shader to crop an Active Object/Picture with Angle and Amount

[Sphax]

Hi,

I'm currently trying to get a shader which can crop an Active Picture (or an Active Object) in a customizable Angle and customizable Amount.

The result would be, for example:
1- Rotate a square by 45° (counter-clockwise) and then use the crop shader to crop the bottom angle. The shader would crop the real picture from the bottom-left corner of the square, and if the amount is 0.5, the result would be perfect triangle)
2- Do not rotate a square (0°) and then use the crop shader. The result would be a cropped square from the right side and if the amount is 0.5, the result would be a semi-square alias rectangle.

Anyone would be good enough (and kind enough) to create this HLSL Shader?

I can make a little Paypal donation to thank the first who answer with a working Shader (nothing big but better than nothing).

Thanks
-Sphax

[Sphax]

No one good at HLSL Shaders?

[nikobanget]

there's no answer...