y + lDestTop
         bDibDst(xDest, yDest) = bDibSrc(x, y) * _
            SourceConstantAlpha / 255 + bDibDst(xDest, yDest) * _
               (1 - SourceConstantAlpha / 255)
         bDibDst(xDest + 1, yDest) = bDibSrc(x + 1, y) * _
            SourceConstantAlpha / 255 + bDibDst(xDest + 1, yDest) * _
               (1 - SourceConstantAlpha / 255)
         bDibDst(xDest + 2, yDest) = bDibSrc(x + 2, y) * _
            SourceConstantAlpha / 255 + bDibDst(xDest + 2, yDest) * _
               (1 - SourceCons