Order statistic last output reference filters

Median filtering can be viewed as operation that selects a sample from each window close to the last output. This observation results in a new edge preserving smoother called the last output reference (LOR) filter. The LOR filter is similar in function to the median or recursive median filters, but has additional advantages particularly in suppressing impulses. It has been shown that repeated applications of LOR filtering produces a sequence that is invariant to subsequent passes through the same filter. Also, it has been proven that any sequence can be converted to a locally monotone sequence by using a combination of "forward" and"backward" LOR filters. When the LOR filter is applied to an actual noisy image, it is shown to perform well.