Does anyone know what this function parameter is?

[mps]

Does anyone know what the MaskImage parameter is for in the LowPass(...) function?

LowPass(LPDISPATCH SourceImage, LPDISPATCH DestImage, const VARIANT& XFilterSize, const VARIANT& YFilterSize, const VARIANT& Tolerance, const VARIANT& MaskImage)

It doesn't make a whole lot of sense because it isn't an LPDISPATCH image like the other two image parameters.

[mps]

I ended up declaring this vOptional variable that I pass in place of the MaskImage parameter...it works fine like that.

COleVariant vOptional ((long) DISP_E_PARAMNOTFOUND, VT_ERROR);