Claude Betrisey, James F. Blinn, Bodin Dresevic,
Bill Hill,
Greg Hitchcock, Bert Keely, Don P. Mitchell, John C. Platt, Turner Whitted, Microsoft Corporation
Proc. Society for Information Display Symposium, pp. 296-299, (2000).
This paper describes the filtering used in Microsoft
ClearType. ClearType is a software system than enhances the resolution and readability
of fonts on displays that contain a repeating pattern of addressable colored
sub-pixels. The filtering in ClearType is based on a perceptual model of human
vision. The perceptual model leads to an optimization technique for finding the
best output values. The results of the optimization can be approximated by pre-filtering
each color channel of an input image and then sampling each filtered color
image at the spatial locations of the same colored sub-pixels in the display.
We refer to this filtering followed by displaced sampling as RGB decimation.
RGB decimation eliminates the phase error caused by standard anti-aliasing. A
further approximation of the optimal filter yields RGB decimation with
displaced box filters. Fourier analysis demonstrates that both the optimization
technique and the displaced box filter suppress frequencies that contribute
most to color fringing in unfiltered displaced sampling.
gzipped PS file (164 KB)
PDF file (135 KB)