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## CDXSurface::CDXBLT_TransAlphaMask

HRESULT CDXBLT_TransAlphaMask( | CDXSurface* dest , LONG lDestX , LONG lDestY , RECT srcRect ) ;

Does a BLT using a transparent alpha mask.

NOTE: m_alphaMask is a pointer to an array of unsinged char values that represents the indiviual alpha values for the bitmap loaded into this CDXSurface. The m_alphaMask array covers the whole surface not just one tile or sprite contained on the surface but for all tiles or sprites. For example if the surface is 400x200 then m_alphaMask points to an array that is also 400x200 BYTEs. If the m_alphaMask is equal to NULL then the function will call CDXBLT_Trans() and draw a simple transparent image.