Grid.py

imgs = np.arange(36).reshape(9, 2, 2)
print(imgs)

"""
array([[[ 0,  1],
        [ 2,  3]],

       [[ 4,  5],
        [ 6,  7]],

       [[ 8,  9],
        [10, 11]],

       [[12, 13],
        [14, 15]],

       [[16, 17],
        [18, 19]],

       [[20, 21],
        [22, 23]],

       [[24, 25],
        [26, 27]],

       [[28, 29],
        [30, 31]],

       [[32, 33],
        [34, 35]]])
"""

np.concatenate(imgs.transpose(0, 2, 1).reshape(3, -1, 2), axis=1).T
"""
array([[ 0,  1,  4,  5,  8,  9],
       [ 2,  3,  6,  7, 10, 11],
       [12, 13, 16, 17, 20, 21],
       [14, 15, 18, 19, 22, 23],
       [24, 25, 28, 29, 32, 33],
       [26, 27, 30, 31, 34, 35]])
"""