[bug-gs] Embedded PostScript in PDF

Ray Johnston ray.johnston@artifex.com
Wed, 22 Jan 2003 08:17:56 -0800


Torsten

Torsten Erler wrote:
> I don' understand, what's the background for that???

The background is bug reports from supported customers requesting
Acrobat
Reader compatibility. In fact, Acrobat Reader doesn't render the DoPS
embedded PostScript because it can't -- it doesn't contain a PS
interpreter.

The other reason for making the default action be to ignore the
PostScript
is that some users processing PDF files may not realize that they should
use -dSAFER to avoid mischeif possible the PostScript. The execution of
the PostScript autmatically enables malcious hackers to embed a PS
virus in a PDF file that users think is just a document file.

> I've no problem to add the switch to get completely processing results, but
> I fear that was the first step for an 'unsupported feature'.

We have no plans to remove the -dDOPS capability since Ghostscript PDF
will
ALWAYS have a PostScript interpreter available (the PDF is largely
written
in PostScript.)
 
> To the compatibility with Acrobat Reader:
> 
> If I print a PDF with embedded postscript (e.g to ljet4) the printed result
> doesn't contain the "EPS-Image" (in ghostscript v8.00 without -dDOPS), but
> Acrobat Reader prints it correctly (on a postscript printer). The only thing
> what Acrobat denies is to preview this with the motive that each printer
> driver can interpret it differently (and can omit the embedded content if
> the printer isn't a postscript printer).

As I pointed out above, Acrobat Reader does not have a PostScript
interpreter,
so it just passes the PostScript through to the printer transparently.

> The mostly important reason for us to use ghostscript instead of Acrobat
> Reader in our project was the ability to preview embedded postscript in
> PDF-Files and the option to rasterize it for NON-Postscript Printers.

Neither of these features are supported by Acrobat Reader since they
require
a PostScript interpreter (which Ghostscript includes).
 
> Can anyone give me a statement, whether it's planned to stop the support for
> that in future?!

As mentioned above, I can state that the -dDOPS function will be kept in
Ghostscript. There is no incentive to remove it, and removing it might
be
detrimental to users or customers.

> If yes, we have to think about substitution of gs with Acrobat Reader (which
> is already installed on the most customer machines).

You mention "customer" machines, but the AFPL license of Ghostscript
prevents
commercial distribution without a license from us (Artifex Software).
Please
read the AFPL license and contact us (sales@artifex.com) if you have any
questions about whether ornot you need a license.

Regards,
Ray Johnston
Director of Engineering
Artifex Software Inc.
_________________________________________________________________________
> > -----Original Message-----
> > From: bug-gs-admin@ghostscript.com
> > [mailto:bug-gs-admin@ghostscript.com]On Behalf Of Ray Johnston
> > Sent: Dienstag, 21. Januar 2003 20:51
> > To: Torsten.Erler@net-linx.com
> > Cc: Bug-Gs (E-mail)
> > Subject: Re: [bug-gs] Embedded PostScript in PDF
> >
> >
> > Torsten,
> >
> > Post 7.30 we made a change to be Acrobat Reader compatible (see
> > doc/History7.htm) that says:
> >
> > Incompatible changes
> >
> >    The -dDOPS flag (to enable DoPS processing) is now disabled by
> >    default, as it is a more reasonable default. Thus, any files
> >    which depend on DoPS will now break unless this flag is set.
> > ----------
> > -
> > The doc/Use.htm now says:
> >
> > -dDOPS
> >    Enables processing of DoPS directives in PDF files. DoPS
> > has in fact
> >    been deprecated for some time. Use of this option is not
> > recommended
> >    in security-conscious applications, as it increases the scope for
> >    malicious code. -dDOPS has no effect on processing of PostScript
> >    source files. Note: in releases 7.30 and earlier,
> > processing of DoPS
> >    was always enabled.
> > -----------
> >
> > The EPS switches (-dNOEPS, -dEPSCrop, -dEPSFitPage) will only
> > affect the
> > processing of EPS input files (not PDF's).
> >
> > Regards,
> > Ray Johnston
> > Artifex Software Inc.
> > ______________________________________________________________
> > ______________
> > Torsten Erler wrote:
> > >
> > > I try to convert PDF-File into PS-File using "pswrite"
> > device and it works
> > > ok for 7.05 and earlier.
> > >
> > > In 8.00 the embedded postscript isn't there anymore.
> > > That means nothing is visible on rendering the PDF (neither
> > in gs-standalone
> > > nor in gsview) AND the produced postscript doesn’t
> > draw/print the original
> > > embedded content.
> > >
> > > Is there a switch to force/suppress this, or is this a bug?
> > > I've tried -dNOEPS but it doesn't make a difference.
> > >
> > > cu Torsten
> > >
> > > _______________________________________________
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