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dpk / et-book

A OpenType version of the typeface used in Edward Tufte’s books.
MIT License
23 stars 2 forks source link

Basic kerning #3

Closed dpk closed 3 years ago

dpk commented 8 years ago

The ETBembo source files didn’t seem to include any kerning information. http://www.sethtaylor.com/fontsive/ has a nice list of character pairs for kerning.

See below.

dpk commented 3 years ago

Over at the source repo, someone suggested that kerning information might indeed be in the font suitcase files, but that this was not extracted properly either by the original conversion, or my first or second attempts. Indeed, looking at the hexdump, there is what appears to be a kerning table in the resource fork of the .suit files. Opening the resource forks with the rsrcfork Python module reveals a FOND resource which seems to match this Adobe documentation at least in terms of the kerning table, but it looks like a fairly complicated format. Not least because kerning values are specified as fractional amounts in a non-standard binary format. Not even sure how to convert those to OpenType kerning values, which are integers.

dpk commented 3 years ago

Okay, I managed to use Fondu to extract the kerning data as AFM files. I believe the kerning unit for AFM is the same as OpenType .fea, but I’ll have to check that. Preliminary investigations show that the kerning data is quite limited in any case, though LF seems to have more than OSF.

dpk commented 3 years ago

‘The kerning amount is specified in the units of the character coordinate system.’ — AFM spec p. 36

dpk commented 3 years ago

Okay, I’ve redone the kerning in the Roman font based on the AFMs extracted by Fondu in 2ceafab, on the assumption (which looks to be correct) that the unit used for kerning values in AFM are the same as in OpenType feature files. Will look at the other fonts now.

dpk commented 3 years ago

Done in 7e48dd0