Called by the filter to determine whether to remove the opacity of a layer by premultiplying it against the palette colors.
HRESULT retVal = object.IsAlphaPremultRequired(pfPremultAlpha);
Address of a BOOL variable that receives TRUE if a premultiply operation is required, or FALSE otherwise.
If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.
A premultiply operation, where color components are adjusted by their corresponding alpha components, is required if the image palette contains alpha information and the palette is being converted to BFID_RGBA_32 format.