Precision of morphological-representation estimators for translation-invariant binary filters: Increasing and nonincreasing

Abstract Mean-absolute-error-optimal, finite-observation, translations, invariant, binary-image filters have previously been characterized in terms of morphological representations: increasing filters as unions of erosions and nonincreasing filters as unions of hit-or-miss operators. Based on these characterizations, (sub)optimal filters have been designed via image-process realizations. The present paper considers the precision of filter estimation via realizations. The following problems are considered: loss of performance owing to employing erosion filters limited by basis size, precision in the estimation of erosion bases, and precision in the estimation of union-of-hit-or-miss filters. A key point: while precision deteriorates for both erosion and hit-or-miss filters as window size increases, the number of image realizations required to obtain good estimation in erosion-filter design can be much less than the number required for hit-or-miss-filter design. Thus, while in theory optimal hit-or-miss filtering is better because the unconstrained optimal hit-or-miss filter is the conditional expectation, owing to estimation error it is very possible that estimated optimal erosion filters are better than estimated optimal hit-or-miss filters.