def split_board(img):
    """
    Given a board image, returns an array of 64 smaller images.
    """
    arr = []
    sq_len = int(img.shape[0] / 8)
    for i in range(8):
        for j in range(8):
            arr.append(img[i * sq_len : (i + 1) * sq_len, j * sq_len : (j + 1) * sq_len])
    return arr