Python Zickzack eine Matrix für DCT
np.concatenate([np.diagonal(a[::-1,:], i)[::(2*(i % 2)-1)] for i in range(1-a.shape[0], a.shape[0])])
Uptight Unicorn
np.concatenate([np.diagonal(a[::-1,:], i)[::(2*(i % 2)-1)] for i in range(1-a.shape[0], a.shape[0])])