[NTG-pdftex] Re: Optimizing the generated pdf
oberdiek at uni-freiburg.de
Fri Nov 18 23:16:31 CET 2005
On Thu, Nov 17, 2005 at 06:46:58PM +0100, Hartmut Henkel wrote:
> On Thu, 17 Nov 2005, Hans Hagen wrote:
> > Martin wrote:
> > > On 2005-11-17 10:46:51 +0100, Martin Schrder wrote:
> > >
> > > > Btw: Is there a tool that compresses a pdf by replacing identical
> > > > objects with references?
> > >
> > > pdfTeX could do this by itself: Store the md5 of the shortest n
> > > objects (e.g. n = 1024) smaller then x bytes (e.g. x = 1024, longer
> > > objects will typically be unique) and replace new identical objects
> > > with references to the already existing ones.
> i won't want to rely on md5 alone (shit happens). Finally one needs a
> literal comparison.
> And when the object is gone, it's nasty to seek
> around in the PDF file.
The position and length of the objects could be stored in memory.
> > > This would e.g. condense all the obj <</S /GoTo /D [n 0 R /Fit]>>
> > > endobj in the pdfTeX manual. :-)
> if it's enough to scan the last say 100 non-stream objects: this can be
> done, at least it would catch these next to each other similar objects.
The matches of "similar" objects can be increased by normalization:
* Removal of unnecessary spaces.
* Ordering of dictionary keys.
* Normalization of strings and names.
Disadvantage: parsing of pdf objects would be necessary.
> Maybe MD5 would be overkill, just a hash + comparison would be ok.
Heiko <oberdiek at uni-freiburg.de>
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