TrueType Typography
OpenType is Microsoft and Adobe's collaborative attempt to "end the font wars", unifying the competing formats of TrueType and Type 1 (including multiple masters). Users will no longer need to concern themselves over the flavour of their fonts - or so the theory goes. In practice, it's likely that good TrueType-OpenTypes will be preferred on screen, while Type 1-OpenTypes will work better on old PostScript devices. OpenType uses the same advanced glyph substitution and layout features introduced in TrueType Open - ligatures will finally have support at the system level. OpenType fonts will also have a "digital signature", which aims to prevent casual modification to the font.

OpenType includes two kinds of font compression, depending whether there's TrueType or Type 1 data inside. For TrueType, it uses Agfa's lossless font compression technology, MicroType Express (be warned that the claimed 90% "compression" is largely due to a font subsetting capability). On the Type 1 side, Adobe's new "Compressed Font Format" averages a claimed 45% reduction without subsetting.

File Structure
OpenType, an evolution of TrueType Open, has a file structure just like TrueType: a series of tables indexed by a table directory. Most tables are formatted identically, no matter whether the actual glyph descriptions are in the TrueType or Type 1 "flavour". If it's Type 1, there is a 'typ1' table instead of the 'glyf' table that TrueType uses.

Comparison with Apple's GX typography
OpenType has many features corresponding to Apple's GX technology, although GX has more features and is in some important ways more efficient. Apple is not involved with OpenType at the moment, although there are plans to write utilities to convert OpenType layout tables into GX. GX's high priest Dave Opstad has written a comparison, including sections on "Where OpenType does better" and "Where GX does better": GX vs. OpenType layout.

OpenType Jamboree, October 1997

See Microsoft's page for all the details of this event, which ran from 27 to 29 October 1997.

Other sites...

TYPE*chimérique | TrueType Typography | TYPE*links