Ghostscript documentation or reference

Levi Pearson levipearson at gmail.com
Thu Feb 13 09:09:27 MST 2014


On Thu, Feb 13, 2014 at 8:46 AM, John Shaver <bobjohnbob at gmail.com> wrote:
> I've tried searching for this on the interwebs, but the google has failed
> me.  I was able to find really good references and documentation on
> postscript, but not the extra commands introduced by ghostscript.
>
> Is anyone aware of any good ghostscript references?
>
> Specifically, I have not been able to find any kind of
> documentation/reference material on runpdfbegin and dopdfpages.

Maybe some others have more insight into this than me, but it's my
understanding that PDF contains a modified subset of PostScript for
graphical descriptions.  It lobotomizes it as a programming language
in order to ease implementation requirements and constrain how it
works.  But it also adds some new commands, which ghostscript has to
understand in order to read them.  Those commands you mentioned are
almost certainly defined by the PDF specification, which is freely
downloadable from Adobe.

I don't think ghostscript implements any custom, ghostscript-only
postscript APIs.  Both postscript and pdf are standardized, and I
believe they're fairly strict about standard-conformance, e.g. there's
text in their documentation about how to strip off common but
technically-illegal junk stored ahead of the real pdf header, which
they could easily handle for you, but they've chosen to be technically
conformant rather than liberal in acceptance.

        --Levi


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