Methods and apparatus for filtering and caching data representing images

Abstract

Methods and apparatus for displaying images, e.g., text characters, on display devices which have multiple separately controllable luminance elements per pixel. Multiple alpha values are generated per pixel, e.g., one per pixel sub-component. Filtering is then performed to generate a filtered alpha value for each pixel sub-component. The filtering operation uses as its input multiple alpha values. The alpha values used for the filtering operation may come from neighboring pixels. Accordingly, in the case where character glyphs are combined to form larger images, e.g., text strings, the filtering operation performed on glyph edge pixels depends on the content of a neighboring character glyph. In one embodiment unfiltered alpha values used to represent character glyphs are stored in a glyph cache. To avoid repeated filtering of character glyphs, in another embodiment, character glyphs are padded along their vertical edges, filtered and then stored in the glyph cache.