SUBPIXEL RENDERING

2/13/99

Subpixel Rendering (Clear Type): Subpixel Rendering is a technique that uses color dots in adjacent pixel groups on color displays to form new "virtual pixels" with centers displaced slightly from the normal centers. Subpixel rendering is similar to and can possibly be superior to, anti-aliasing.

For example, on an LCD display where pixels consist of three colored subpixels, a normal white pixel would be formed by illuminating the RBG subpixels of one pixel:

rbgrgbRBGrbgrbg

The only choices for a line below or above on a slanted white line are:

   rbgRBGrbgrbgrbg
         or
   rbgrgbRBGrbgrbg
         or
   rbgrbgrbgRBGrbg

This results in jagged lines and edges commonly known as "jaggies".

Subpixel rendering might create a new white dot by mixing purple and green or cyan and red:

   rbgrbGRBgrbgrbg
         or
   rbgrbgrBGRbgrbg

This improves resolution by a factor of three and results in better definition of small fonts, in better character separation, more control over bold and better italics for small fonts.

Subpixel rendering dates from the early days of personal computing and is used by Microsoft in it's "ClearType" technology.

A fuller explanation and a demonstration program are available at http://www.grc.com/ctwhat.htm. See also http://en.wikipedia.org/wiki/Subpixel_rendering.

Return To Index Copyright 1994-2002 by Donald Kenney.