Sets the amount of blur to be applied to the alpha channel of the image.
HRESULT SetStandardDeviation( IDCompositionAnimation *animation );
An animation that represents how the amount of blur to be applied to the alpha channel of the image changes over time.
You can compute the blur radius of the kernel by multiplying the standard deviation by 3.
The units of both the standard deviation and blur radius are DIPs.
This parameter must not be NULL.
If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.