Am 19.09.2017 um 02:27 schrieb Perry Hutchison:
There is a tool for using this method of removing duplicate fonts.
https://www.ctan.org/pkg/extractpdfmark
https://packages.debian.org/stretch/extractpdfmark
http://packages.ubuntu.com/zesty/extractpdfmark
As I see it, the availability of a separate tool to do the same thing
is a reason to _not_ provide a duplicate capability in Ghostscript.
Those who want that processing (despite the risks that Ken mentioned)
can use extractpdfmark.
Masamichi described extractpdfmark in a misleading way. pdfmark is a helper program that generates a postscript file from a pdf document. Both, the pdf document and the ps generated by pdfmark, are then processed by ghostscript to generate a final pdf. extractpdfmark is only used if the source pdf
containes links / hyperrefs that would otherwise be broken during the final pass of ghostscript.
A typical way to write a musicological document, a collection of songs, a
lilypond manual etc is described below:
1. Write your music.
2. Use "lilypond --bigpdf" to generate pdfs. Internally lilypond generates
postscript files and then runs ghostscript to generate pdfs.
3. Write the pdf(la)tex/lua(la)tex/xe(la)tex document that uses the pdfs
generated in step 2
4. Use pdf(la)tex/lua(la)tex/xe(la)tex to generate a pdf.
5. If necessary, use extractpdfmark to extract pdfmarks from the pdf generated
in step 4 (extractpdfmark generates a postscript file)
6. Use ghostscript to generate the final pdf from the pdf generated in step 4
and the postscript file generated in step 5.
This sounds a bit complicated, but the reduction of file size is significant. In 2014
this was discussed here on the ghostscript bugzilla.
<https://bugs.ghostscript.com/show_bug.cgi?id=695728>
Without the use of lilyponds "--bigpdf" option our notation manual had a size
of 26 MB after step 4.
With the introduction of the "--bigpdf" option and steps 5 and 6 the file size
after step 4 increased to 116 MB, but the size of the pdf generated in step 6 was only
5.9 MB. That means we were able to eliminate more than 20MB of duplicated fonts.
Another example is gotlandstoner, a collection of folk tunes from Sweden. If
you remove the PDFDontUseFontObjectNum option book 3 has a file size of
13.706.324 bytes. If a ghostscript with the PDFDontUseFontObjectNum option
enabled is used that boils down to 2.447.232 bytes.
In an earlier message in this thread Ken Sharp wrote: "Risking incorrect output for the minimal benefit of a slightly smaller file seems unwise to me." Yes, the default should be not to enable PDFDontUseFontObjectNum. But as I pointed out above: The benefit of the PDFDontUseFontObjectNum is not only
a "slightly smaller file", the benefit is a very significant reduction of file size often exceeding 80%.
I understand why the default behavior of ghostscript changed. But could anyone
who advocates to remove the PDFDontUseFontObjectNum be so kind to give a clear
explanation why keeping it would be a bad idea?
Knut
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