Two-dimensional root structures and convergence properties of the separable median filter
T. Nodes, Neal C. Gallagher · IEEE Transactions on Acoustics Speech and Signal Processing · 1983
The root (signals invariant to filtering) structures of the two-dimensional separable median filter are derived and presented. In addition, it is proved that with rare exception, after repetitive passes of the separable median filter any two-dimensional signal will be reduced to a signal containing only root structures.