[Desktop_printing] Agenda proposal: Replace PostScript by PDF as job transfer format

Michael Sweet mike at easysw.com
Sat Jan 7 16:45:31 PST 2006

Robert L Krawitz wrote:
> ...
> It would probably be desirable to support higher level output for
> printers that support it, although when I ran even a low end, high
> speed HP laser printer, it had no trouble keeping up with raster
> output.

Agreed, and I think the stuff the OpenPrinting folks are doing will
yield an extensible vector printing interface.

FWIW, all of our current development and plans allow us to use any
PDF engine, including Ghostscript which already supports vector
languages like PCL 6, in addition to the existing Xpdf-based pdftops
filter (which will still get used for PostScript output...)

> Does PDF (and the xpdf engine) support high bit depths (such as 16
> bits)?  I'd like to see us move in that direction.  There's nothing

PDF supports it, and I *think* Derek's Splash engine will do arbitrary
bit depths and colorspaces (perhaps we should invite him to the summit
as well - I'll ask if he is interested...)

> wrong with 8 bits for a lot of things, but if the engine supports 16
> bits it could e. g. support color management without losing too much
> precision.  That would save each driver from having to implement color
> management itself.

Right, however IMHO most drivers will still do some level of color
management themselves, as a side-effect of the dithering/halftoning

> Would this still use PPD files, or would there be other ways of
> exposing printer capabilities to applications?

Still PPD files.  I don't see that changing anytime soon, and I think
the PPD extensions I'll be demoing/presenting at the summit should
satisfy most of your needs (if not all).

The problem with UPDF and other possible contenders right now is
that they have no vendor support, and they don't map cleanly to/from
PPD files so we can't just convert PPD files or hide the differences
in the CUPS API... :(

> ...
> Till, do you have a list of what devices are supported in legacy
> Ghostscript drivers that aren't supported in some other driver (HPLIP,
> Gutenprint, and Omni between them support a lot of printers)?  I
> suspect that Epson impact printers are a significant fraction of the
> list, and I suspect that it wouldn't be too hard to support them in
> Gutenprint if someone wants to volunteer to do that.

We already support all of the current dot-matrix printers via the
CUPS rastertoepson driver.  We're also updating the CUPS DDK's
rastertoescpx driver to support the dot matrix modes, so that we
can support "softweaved" 240x216 output on the 9-pin printers (and
maybe do some other tricks to speed up the output...)

Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Publishing Software        http://www.easysw.com

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