test.py

a = np.arange(20).reshape(4,5)
#array([[ 0,  1,  2,  3,  4],
#       [ 5,  6,  7,  8,  9],
#       [10, 11, 12, 13, 14],
#       [15, 16, 17, 18, 19]])
b = np.repeat(a,2).reshape(*a.shape,2)
#array([[[ 0,  0],
#        [ 1,  1],
#        [ 2,  2],
#        [ 3,  3],
#        [ 4,  4]],
#
#       [[ 5,  5],
#        [ 6,  6],
#        [ 7,  7],
#        [ 8,  8],
#        [ 9,  9]],
#
#       [[10, 10],
#        [11, 11],
#        [12, 12],
#        [13, 13],
#        [14, 14]],
#
#       [[15, 15],
#        [16, 16],
#        [17, 17],
#        [18, 18],
#        [19, 19]]])
b[:,:,0] = 1 - b[:,:,1]
array([[[  1,   0],
        [  0,   1],
        [ -1,   2],
        [ -2,   3],
        [ -3,   4]],

       [[ -4,   5],
        [ -5,   6],
        [ -6,   7],
        [ -7,   8],
        [ -8,   9]],

       [[ -9,  10],
        [-10,  11],
        [-11,  12],
        [-12,  13],
        [-13,  14]],

       [[-14,  15],
        [-15,  16],
        [-16,  17],
        [-17,  18],
        [-18,  19]]])