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Date: Tue, 06 Feb 2007 17:28:33 +0100
From: Vincent Hennebert <vincent.hennebert@anyware-tech.com>
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To: general@xmlgraphics.apache.org
Subject: Re: [VOTE] New component: DSC parser/processor
References: <20070203190402.FC9C.DEV@jeremias-maerki.ch>
In-Reply-To: <20070203190402.FC9C.DEV@jeremias-maerki.ch>
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+1

This looks like a nice piece of code, well written and, even more
importantly, well commented ;-)

I've noticed a few glitches while skimming through the patch (prepend
paths with org.apache.xmlgraphics.ps):
- DSCConstants.java, l28: "inidicating"
- PSGenerator.java, l88: "hardcoded to level 2" instead of 3 now
- dsc.DefaultDSCHandler.java, l30: which "is simply passed"? "which
simply passes"? I guess the latter is the correct one.

Vincent


Jeremias Maerki a �crit :
> Hi there
> 
> I've just finished the initial version of a DSC parser which I'd like to
> put into XML Graphics Commons. What the heck is a DSC parser? :-) Here's
> the text of the (somewhat minimal) documentation I wrote for the thing:
> 
> ------------------------
> 
> DSC parser/processor
> 
> Many PostScript files use special comments to structure a document. This
> allows manipulation of PostScript files without interpreting them. These
> special comments are defined in the Document Structuring Conventions.
> http://partners.adobe.com/public/developer/en/ps/5001.DSC_Spec.pdf
> The code in Commons is designed to work with DSC 3.0. For details on how
> DSC is used, please take a look at the DSC specification.
> 
> The DSC support in Commons was primarily developed to implement resource
> optimization features in Apache FOP's PostScript output support.
> Resources like images which are used repeatedly in a document should not
> be written to the PostScript file each time it is used. Instead it is
> written once at the beginning of the file as a PostScript form. The form
> is then called whenever the image needs painting.
> 
> But the DSC parser could potentially be used for other purposes. The
> most obvious is extracting a subset of pages from a DSC-compliant file.
> Assume you want to print only page 45 to 57 of a particular document.
> There's an example that demonstrates exactly this. Check out the
> "examples" directory in the distribution. Other potential use cases for
> the DSC parser are:
> 
>     * Patching PostScript files, for example, adding OMR marks for automatic packaging
>     * Imposition (2-up, n-up, rotation, etc.)
>     * EPS graphic extraction
>     * Inspecting the page count
>     * etc. etc.
> 
> The DSC parser (DSCParser) was designed as a pull parser, i.e. you fetch
> new events from the parser inspecting them and acting on them as they
> are found. If you prefer to work with a push parser, you can pass the
> DSCParser a DSCHandler implementation and the parser will send you all
> the events.
> 
> The best example to understand how to use the DSC parser is the
> PageExtractor class that implements the page extraction functionality
> mentioned above. 
> 
> ------------------------
> 
> I hope that explains what I've built. I'd like to ask if anyone has any
> reservations about my adding the DSC parser to XML Graphics Commons.
> After all, it's a rather large and completely new thing and therefore I
> thought it necessary to ask before committing. It's probably a lot less
> interesting for Batik, but it is for FOP. Since it is designed to be
> used separately from FOP I thought it was best to put it in Commons.
> I've also already built the resource optimization functionality for FOP
> that uses the DSC parser. I can commit those changes (Commons and FOP)
> as soon as we know that nobody objects.
> 
> I've made a patch containing the DSC parser available (including full
> javadocs, an example and minimal documentation for the website), so you
> can see what exactly we're talking about:
> http://people.apache.org/~jeremias/xmlgraphics-commons-dsc-new.diff.txt
> 
> 
> +1 from me for adding the DSC parser (obviously).
> 
> Jeremias Maerki
> 
> 
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