roberts梯度算子 G lg(x, y) g G(x,y)=(8+g)2 ,-(-8)88手Roberts梯度算子         =                 = v u r g g v g u g G g(x, y) 2 1 2 2 ( , ) ( ) r u v G x y = g + g ( ) 2 1 2 , , 1 2 , , 1, ( ) i j = i j − i+ j + i j − i j+ G g g g g -1 1 -1 1