Yeqing Zhang

Document restoration and enhancement using optimal iterative and paired morphological filters

Restoration and enhancement of digital documents typically involves use of binary filters. Various methods have been developed to facilitate automatic design of optimal binary filters in the context of morphological image processing. Among these are iterative increasing filters for designing optimal increasing filters in stages, and paired- representation filters, in which a nonincreasing filter is represented as a union of anti-extensive and extensive increasing filters. The present paper applies these filters in three different modalities for digital document enhancement. Iterative design is illustrated in the context of document restoration for dilated, background-noise images; iterative, paired design is illustrate in for restoration of edge-degraded characters; and paired design is used for integer resolution conversion.