[Desktop_printing] Agenda proposal: Replace PostScript by PDF asjob transfer format

Hin-Tak Leung hintak_leung at yahoo.co.uk
Tue Jan 10 02:26:02 PST 2006

--- Till Kamppeter <till.kamppeter at gmx.net> wrote:
> > Reordering pages, scaling, n-up are much easier with PDF than with
> postscript,
> > I think;
> Anyone cam confirm?

Well, I can tell you I know of one package (pdfpage/pdfLaTeX) which I use
a lot for n-up, scaling, reordering purposes :-). It is part of teTeX 3 
- so most probably is on Mandriva 2005/2006 - and it has some xpdf code 
in it. (like Mike Sweet says, xpdf's code can be converted to a 
library sort of scenario quite quickly). 

> > that's just because Adobe had learned from postscript and made pdf
> > having metadata for describing the overall structure, and
> > pdf's are also randomly seekable/navigable based on the metadata.
> > (the xref table at the end and what not).
> Every PDF has such metadata?

Yes. If you "strings" a pdf file, towards the end there is something like this:

0 28
0000000000 65535 f
0000008256 00000 n

Those numbers in the middle between xref and trailer are byte offset from
the beginning of file to the numbered objects in a pdf (and startxref points to
the start of the xref table), so you can navigate
directly to an object [which can be a page or other structures] 
just after reading the last part of a pdf. This is also how a "poorman's
incremental update" of pdf works - one appends a new/changed page to 
the end and write a new xref table referencing all the old structures plus
new ones. This way one can "delete" pages while the pdf file grows in size.
(at least this is how my vague memory of how pdf works, having only 
read the spec once...)


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