Re: Ghostscript/GhostPDL 9.22 Release Candidate 1

[Knut Petersen]

> Well, it occurs to me that the *real* problem here is that the fonts in the individual PDF files are subsets. If they were not, then I believe you could safely and easily use MuPDF (specifically mutool clean) to remove the duplicate fonts. Or at least, the duplicate FontFile streams, I'm not 
> certain if the Font and FontDescriptor objects would be possible to remove as well. But that would certainly cover a good portion of the file size, the fonts are running at about 9Kb each, while the Font and FontDescriptor objects are a few tens of bytes.

The fonts in the pdfs are identical fonts constructed by ghostscript on the fly, I think 
it was Ken Sharp who explained to me some years ago that the term "subset" is 
wrong ;-)

One emmentaler font + three encodings + one character (scaled to invisibilty) of each encoding used prior to anything else  in the ps leads ghostscript to produce three different subsets ;-)) of the emmentaler font in every pdf. But the set of 3  "subsets" is identical in any pdf that is produced 
this way, and so gs  is (was) able to remove the duplicates. That's the --bigpdf trick.

I agree that mutool clean can be a good starting point. If I read the documentation 
correctly, it does "clean" (remove) unused objects, but it is unable to subset 
fonts if not all glyphs of the fonts are used?

> So the question then becomes 'why are the fonts subset ?' That's a really good question, and the answer is that I don't know. Its possible that there is a genuine pdfwrite bug here. The piece of information I'm missing is the step used to create the PDF files from the EPS files, I don't know how 
> you are doing that.

lilypond spawns ghostscript. If our --bigpdf option is used the command is e.g.:

    gs -q -dSAFER -dEPSCrop -dCompatibilityLevel=1.4 -dNOPAUSE -dBATCH -r1200 
-dSubsetFonts=false -sDEVICE=pdfwrite -dAutoRotatePages=/None 
-sOutputFile=testa.pdf -c.setpdfwrite -ftesta.eps


> My attempts to replicate the individual PDF files have been entirely 
> unsuccessful, I get files with three copies of the Emmentaler font embedded 
> instead of 1, and none of the three fonts match the ones in the PDF files Knut 
> supplied.

I used tag ghostscript-9.21 from the git repository.

> Hmm, actually, going back to the 9.21 release does produce at least similar 
> behaviour, whereas the 9.22 release does not. In 9.22 I get three fonts output 
> instead of 1. I've no idea why currently, and right at the moment I don't have 
> time to look.
>
> I'll try and remember to look at it when I am not drowning under support, but 
> it looks like there have been changes in this area unrelated to the 
> PDFDontUseObjectNum bug, and that in itself may mean that your process doesn't 
> work any more, or works less well.

Thanks for you patience!

Knut