One form of digital document enhancement maps a binary image to N-bits/pixel while maintaining constant spatial sampling resolution. Pixels in character stroke interiors and in the background typically retain black or white values, while certain edge pixels map to intermediate `gray' levels, effectively lessening the jagged appearance of curved and angled strokes. This paper presents a binary-to-gray operator that employs binary erosion-based filters in an iterative stacking architecture. We describe the filter architecture, optimal design method, and demonstrate binary-to-gray enhancement using only a small number of morphological erosions.
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