Re: Benefits of Cairo backend over Ghostscript for PDF

[Jean Abou Samra]

(moving to the devel list from the user list)

Le samedi 18 mars 2023 à 05:08 +0000, Werner LEMBERG a écrit :
> ```
> 
> > I can see that the size of the Cairo-generated PDF is around 3 times
> > bigger compared to the same document generated with Ghostscript?  Is
> > there is way to reduce the size of the Cairo-generated PDF?
> 
> You might try `pdfsizeopt`.
> 
>   [https://github.com/pts/pdfsizeopt](https://github.com/pts/pdfsizeopt)


Interesting. On 
[https://github.com/pts/pdfsizeopt/releases/download/docs-v1/pts_pdfsizeopt2009.psom.pdf](https://github.com/pts/pdfsizeopt/releases/download/docs-v1/pts_pdfsizeopt2009.psom.pdf),
 I read (emphasis mine):


> For glyphs coming from external sources such as the
> included PostScript and PDF graphics, the driver
> is usually not smart enough to recognize the fonts
> already embedded, and unify them with the fonts in
> the main document. Let’s suppose that the docu-
> ment contains included graphics with text captions,
> each graphics source PostScript or PDF having the
> font subsets embedded. No matter dvips, dvipdfm(x)
> or pdfTEX is the driver, it will not be smart enough
> to unify these subsets to a single font. Thus space
> would be wasted in the finally PDF file containing
> multiple subsets of the same font, possibly storing
> duplicate versions of some glyphs.
> It is possible to avoid this waste by using a
> graphics package implemented in pure TEX (such
> as TikZ) or using METAPOST (for which there is
> special support in dvips, dvipdfm(x) and pdfTEX to
> avoid font and glyph duplication). The package ps-
> frag doesn’t suffer from this problem either if the
> EPS files don’t contain any fonts embedded.
> *There is no need to pay attention to this tweak,
> because pdfsizeopt.py unifies font subsets.*

I haven't tried it and don't want to (this topic is too emotional for me right 
now), but if anyone is interested in reducing the size of doc PDFs when 
generated with the Cairo backend, this tool could be worth exploring.

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