Re: How to cut/crop a part of a PDF file

[Ken Irving <fnkci@uaf.edu>]

On Fri, Oct 27, 2006 at 11:17:22AM -0400, Matthew Krauss wrote:
> Stefan Monnier wrote:
> > someone wrote:
> >><theory>
> >>AFAIK: PDF is not strictly speaking a vector-graphics format.  It is
> >>a subset of Postscript, which is actually a programming language for 
> >>drawing
> >>documents.  It is designed for output, not input or editing.  Therefor, it
> >>is *very* hard to convert from PDF to a structured document format.
> >></theory>
> >>    
> >
> >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?

>From http://en.wikipedia.org/wiki/Pdf,

  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
    appropriate.
  
  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, fnkci@uaf.edu