Methods, apparatus and data structures for overscaling or oversampling character feature information in a system for rendering text on horizontally striped displays

Abstract

The resolution of text rendered on a display device having sub-pixel elements, such as an RGB LCD for example, and in particular, on a display device having horizontal striping is enhanced by (i) overscaling (or oversampling) character outline information in the vertical (or Y) direction, and (ii) filtering displaced information from the overscaled (or oversampled) character outline information. Metrics associated with character outline information may be appropriately adjusted. The vertical (or Y) position of the baseline of adjacent characters may be constrained by forcing the first pixel above the baseline to be composed of a full number N of scan conversion source samples, where N corresponds to an overscaling (or oversampling) factor. Groups of scan conversion source samples may be converted into packed pixel index values. Color values may be selectively filtered when the differences in the intensity of adjacent sub-pixel elements would otherwise be irritating to view. Finally, the gamma of the pixel values may be corrected so that the gamma of the display device is considered and so that intensity values of sub-pixel elements fall within a range of intensities in which gamma correction is more useful.