Re: TTC fonts

On Wednesday, April 30, 2003, at 02:27  AM, Raymond Mercier wrote:

> At least this seems to settle in the negative the question as to 
> whether they all have the same unicode blocks.
> On my disk the TTC's have two fonts, except for msgothic.ttc which has 
> three.
> I just wondered if Microsoft or anyone else had followed firm 
> guidlines, or just did it in a more whimsical way. It is hard to see 
> the real point of a TTC.

TTC fonts and their rationales are discussed at some length on 
Microsoft's typography Web site 
(<http://www.microsoft.com/typography/>, specifically 
<http://www.microsoft.com/typography/otspec/otff.htm>).

Theoretically, a TTC font can contain an indefinitely large number of 
fonts, since the numFonts field is 32 bits.  In practice, more than 
three or four is unlikely.  As explained in the spec, the purpose is to 
allow large fonts to overlap their data; if you have two Japanese 
fonts, say, one with proportional Roman and one with monospaced, but 
identical kanji.  Then the huge 'glyf' table can be shared by the two 
with the smaller tables (such as 'cmap' and 'name') used to distinguish 
them.  The result is a single file which contains two fonts but is 
considerably smaller than the two individual fonts would be as two 
files.

One could also use TTC files to store multiple related fonts even 
without overlap.  If I had a roman, bold, italic, and bold-italic, I 
could put all four into a single TTC file and have them therefore ship 
as a single file, rather than four individual files.

==========
John H. Jenkins
jenkins@xxxxxxxxx
jhjenkins@xxxxxxx
http://www.tejat.net/