Re: How to cut/crop a part of a PDF file
On Fri, Oct 27, 2006 at 11:17:22AM -0400, Matthew Krauss wrote:
> Stefan Monnier wrote:
> > someone wrote:
> >>AFAIK: PDF is not strictly speaking a vector-graphics format. It is
> >>a subset of Postscript, which is actually a programming language for
> >>documents. It is designed for output, not input or editing. Therefor, it
> >>is *very* hard to convert from PDF to a structured document format.
> >Actually, PDF is not a programming language, contrary to Postscript.
> >So it's much easier to deal with (and more difficult to introduce viruses
> >into it, among other things).
> Really? Can you explain more about this? I thought PDF was a subset of
> Postscript with some kind of compression and/or encryption applied. Was
> I mislead? If so, what is it really? Is there no relationship between
> the two?
PDF is primarily the combination of three technologies:
* a sub-set of the PostScript page description programming language,
for generating the layout and graphics,
* a font-embedding/replacement system to allow fonts to travel with
the documents, and
* a structured storage system to bundle these elements and any
associated content into a single file, with data compression where
PostScript is a computer language -- more precisely, a page description
language -- that is run in an interpreter to generate an image. This
process requires a fair amount of resources.
PDF is a file format instead of a programming language and for that
reason it doesn't need to be interpreted. For instance, flow control
commands like if and loop are removed, while graphics commands such
as lineto remain.
I don't know if there's anything in the wikipedia article to address
the subject question.
Ken Irving, email@example.com