OpenType Layout features allow for orthographically correct display of complex scripts such as Arabic and Indic and provide a mechanism for the user to apply advanced typographic formatting to text. They are used in the SFNT
This document contains a useful classification of OpenType Layout feature tags. It is based on the OpenType spec version 1.6, with some additional entries about removed features and Microsoft-only Math features related to the
MATH OpenType table.
This document is very technical in nature, and is primarily aimed at software developers who wish to implement user interfaces for applying OpenType Layout features in applications.
Although Fontlab Ltd. debuted the Photofont technology some 8 years ago, the typographic community did not show much interest for multi-color fonts or typography. In 2013, it changed. Actually, this started a few years ago with Apple introducing the color emoji font into iOS, and then Mac OS X 10.7. Now, all major industry players (Apple, Adobe, Mozilla, Google and Microsoft) have proposed their formats, which aim to extend the OpenType font format by the ability of including color glyph information. The proposals differ in many aspects. Below is a discussion of the proposals along with some personal comments.
This article is very technical. No completeness or correctness of the information presented below, and all views are personal.
The video tutorial by Adam Twardoch accompanies this article by providing a more practical take on color font creation issues.