Editing Subpixel rendering (section)

== History ==

The origin of subpixel rendering as used today remains controversial. [[Apple Inc.]], [[IBM]], and [[Microsoft]] patented various implementations with certain technical differences owing to the different purposes their technologies were intended for.<ref>John Markoff, "[https://www.nytimes.com/library/tech/98/12/biztech/articles/07microsoft-flat.html Microsoft's Cleartype Sets Off Debate on Originality] {{Webarchive|url=https://web.archive.org/web/20170421095144/http://www.nytimes.com/library/tech/98/12/biztech/articles/07microsoft-flat.html |date=2017-04-21 }}", ''New York Times'', December 7, 1998</ref>

Microsoft had several [[Software patent|patents]] in the United States on subpixel rendering technology for text rendering on RGB Stripe layouts. The patents 6,219,025, 6,239,783, 6,307,566, 6,225,973, 6,243,070, 6,393,145, 6,421,054, 6,282,327, 6,624,828 were filed between October 7, 1998, and October 7, 1999, and expired on July 30, 2019.<ref name="cleartype_expl" /> Analysis of the patent by FreeType<ref name="patents" /> indicates that the idea of subpixel rendering is not covered by the patent, but by the actual filter used as a last step to balance the color. Microsoft's patent describes the smallest filter possible that distributes each subpixel value to an equal amount of R,G, and B pixels. Any other filter will either be blurrier or will introduce color artifacts.

Apple was able to use it in [[MacOS|Mac OS X]] due to a patent [[cross-licensing]] agreement.<ref>{{cite web|url=http://lists.gnu.org/archive/html/freetype/2006-09/msg00064.html|date=September 24, 2006|access-date=April 9, 2009|title=LCD Rendering Patches|archive-url=https://web.archive.org/web/20110603232951/http://lists.gnu.org/archive/html/freetype/2006-09/msg00064.html|archive-date=2011-06-03|url-status=live}}</ref>