FreeType & Patents

The TrueType Bytecode Patents Have Expired!

Since May 2010, all patents related to bytecode hinting have expired worldwide. It it thus no longer necessary to disable the bytecode interpreter, and starting with FreeType version 2.4, it is enabled by default.

The affected patents were

The ClearType Color Filtering Patents Have Expired!

Since August 2019, all patents related to ClearType color filtering have expired worldwide.

The affected patents were

Essentially, these patents covered several different things, which can be grossly sub-divided into

  • the process of displaying images where data is ‘mapped’ to individual (e.g., LCD) sub-pixels, instead of whole pixels,
  • the process of displaying said images after filtering them for various purposes, e.g., reducing color fringes, and
  • the process of dealing with metrics and spacing rounding in a sub-pixel world.

It is possible that Microsoft acquired other patents related to the field in the previous years.

Please note that above claims do not cover the enhanced interpretation of TrueType bytecode instructions as discussed in Greg Hitchcock's whitepaper.

Last update: 17-Aug-2020