Editing OpenType (section)

==Description==
<gallery style="float:right;">
File:Circle and quadratic bezier.svg|TrueType outlines use quadratic [[Bézier curve]]s.
File:Circle and cubic bezier.svg|CFF outlines use cubic Bézier curves.
</gallery>
OpenType uses the general [[sfnt]] structure of a TrueType font, but it adds several smartfont options that enhance the font's typographic and language support capabilities.

The [[glyph]] [[outline font|outline data]] in an OpenType font may be in one of two formats: either TrueType format outlines in a 'glyf' table, or [[Compact Font Format]] (CFF) outlines in a 'CFF&nbsp;' table. (The table name 'CFF&nbsp;' is four characters long, ending in a space character.) CFF outline data is based on the [[PostScript]] language Type 2 font format. However, the OpenType specification (pre-1.8) does not support the use of PostScript outlines in a TrueType Collection font file. After version 1.8, both formats are supported in the renamed "OpenType Collection".

For many purposes, such as layout, it does not matter what the outline data format is, but for some purposes, such as [[rasterisation]], it is significant.  The OpenType standard does not specify the outline data format: rather, it accommodates any of several existing standards.  Sometimes terms like "OpenType (PostScript flavor)" (= "Type 1 OpenType", "OpenType CFF") or "OpenType (TrueType flavor)" are used to indicate which outline format a particular OpenType font file contains.

OpenType has several distinctive characteristics:
* Accommodates the [[Unicode]] [[character encoding]] (as well as others), so that it can support any writing script (or multiple scripts at once).
* Accommodates up to 65,536 glyphs.
* Advanced typographic "layout" features which prescribe positioning and replacement of rendered glyphs.  Replacement features include [[Typographic ligature|ligature]]s; positioning features include [[kerning]], mark placement, and [[Baseline (typography)|baseline]] specification.
* Cross-platform font files, which can be used without modification on Mac OS, Microsoft Windows and Unix/Linux systems.
* If no additional glyphs or extensive typographic features are added, OpenType CFF fonts can be considerably smaller than their Type 1 counterparts.