Quadratic digital filters for image processing
Giovanni Ramponi, Giovanni L. Sicuranza · IEEE Transactions on Acoustics Speech and Signal Processing · 1988
A class of nonlinear two-dimensional filters is presented. A matrix description is developed for such operators, and some symmetry conditions are imposed which simplify and render more effective the filter structure. A strategy for the design of filters capable of enhancing images having reduced contrast and degraded by noise is proposed.>