Median type filters for color signals

Vector median filters with linear substructures are introduced for multispectral signals. It is shown that these filters utilize the correlation between the spectral components, which is an important property when the edge shape and location should be preserved from each signal component simultaneously. To improve the noise-reduction characteristics of vector median filters, an extension to the vector median is introduced which uses the average vector on smooth areas. The vector median approach is applied to the FIR (finite impulse response)-median hybrid filters. The resulting vector FIR-median hybrid filters are shown to have good noise attenuation and low bias error near edges. Efficient methods for implementation are introduced. It is noted that vector median filters can be applied to standard color images in TV systems and to multispectral satellite images