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From Craig Ringer <ring...@ringerc.id.au>
Subject Duplicate fonts in PDF when Distiller processes fop PostScript
Date Wed, 11 Jan 2012 04:46:02 GMT
Hi all

I'm struggling with font embedding in fop's PostScript output - it's
embedding multiple copies of fonts, just like pdf output with
fop-pdf-image, and this is causing some big problems with our RIP.

As a workaround for the issues I've been having with fop-pdf-image where
output PDFs land up with tens or hundreds of different embedded subsets
of the same font, I've been trying to see if chucking PostScript output
from fop through Adobe Acrobat Distiller would work better. In our
current (non-fop-based) workflow Distiller seems to coalesce fonts so
the documents that're produced contain only one copy of the font despite
the input EPSs each having their own embedded subset. I was hoping it'd
do the same for PostScript from fop.

Unexpectedly, I get the same kind of font duplication when I process
fop's PostScript through distiller as I get from fop-pdf-image and the
pdf renderer. A side-by-side comparison of the PostScript from the old
system and from fop shows that the embedded EPS files are copied
verbatim in to the PostScript stream by both fop and the old system, so
it's not doing any kind of clever transformation to the EPS data its
self. Somehow, though, the old system manages to merge fonts, and fop's
PostScript output doesn't.

The old system uses similar-looking pre- and post- eps inclusion
procedures, but they're a little simpler. They don't try to compensate
for leaked stack entries like fop's seem to; they also don't mess with
`userdict', strokeadjust or overprint. There's certainly no font magic
in them. It's not that, though, as I get the same results if I replace
fop's pre- and post-eps procedures with those used in the old system.

I don't speak PostScript particularly well, and I'm beginning to really
bash my head against a wall here, so I thought I'd look for some advice.
Is merging fonts the norm with Distiller, or is it something magic that
the old system's PostScript file is doing? If it's the norm, what might
Fop's PostScript files be doing to block it? If it's not the norm, any
ideas how the old files might be doing the merging magic?

I can happily provide PostScript files from the old system to anyone
interested. The ones I'm working on are about 60MB each, but I can
produce cut-down one page ones that should be no more than 5MB
compressed. I don't know if I can legally provide excerpts of just the
PostScript procedures so I'm going to err on the side of providing a
whole file as a complete document.

If I/we can figure out what's different it'll hopefully allow font
merging in fop's PostScript output, so I'd be very happy to hear from
anyone else interested in the same problem.

I'm still working on PDF font merging in fop-pdf-image, btw, I was just
hoping this would be a faster track where I could let Distiller do the
merging for me. Merging fonts in fop-pdf-image will require me to extend
fop's core to allow image handlers etc to hook on events in the renderer
system so it's going to take patches to fop core and therefore time.

Ideas on what might be going on? Let me know if you want a copy of the
PostScript files involved.

--
Craig Ringer



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