# [pdftex] Re: [tex-k] writet1: font subsetting question

Tom Kacvinsky tjk at ams.org
Tue Oct 16 14:40:09 CEST 2001

SENDING RESPONSE ONLY TO PDFTEX MAILING LIST.

pdftex subsets both subroutines and charstrings.  The result dhould be the same
as dvips, if one is using the dvips from TeX Live 6.0, and one is not subsetting
a multiply re-enoded font.

The subroutine numbers are not reordered.  There were some issues earlier this
year with pdftex generated PDF files and Acrobat 5.0, and when I went int the
code to fix the problem, I didn't re-order the subroutines because I didn't have
answers to some questions (for instance, what about calculated subroutine
numbers [25 5 div callsubr])

Now that the open questions I had have been answered, I could re-order the
subroutines when they are substeed, but i haven't the time (right now) to do so.
The problem is not making a new subss array with no gaps; the problem is
rebuilding the charstrings/subroutines to call the appropriate newly numbered
subroutine(s).

Speaking of gaps in the subroutines array: currently, if the subset Subrs array
has gaps (i.e., there is room for 30 subroutines, but only 6 slots are used), I
fill in the blank slots with an empty subroutine (just call return).

That is what will chnage when I get around to sdoing things the "right" way.  It
should make embedded fonts smaller.

Tom

On Tue, 16 Oct 2001, Vladimir Volovich wrote:

> Hi,
>
> i've been reported that PDF files generated with pdftex using cm-super
> fonts are bigger than the ones generated via dvips+distiller.
>
> could this be the result of preserving all Subrs entries in the
> embedded fonts?
>
> cm-super fonts have big number of Subrs entries, and if pdfTeX
> downloads the font partially into a PDF file, does it reduce unused
> Subrs entries (in addition to unused CharStrings entries)?
>
> to remove unused Subrs entries, the writet1 module must analyse all
> glyph and subrs charstrings, find out the used (possibly recursively)
> Subrs entries, then reorder the Subrs (to avoid gaps), and store the
> new glyph charstrings with changed references to subrs.
>
>
> Best,
> v.
>
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