FW: [OSGeo-Discuss] Proposal: OSGeo Cartographic Library
bruno at 1t3xt.com
Sun Apr 13 04:10:54 PDT 2008
this mail was forwarded to me, and I immediately subscribed to
the mailing list to set something straight.
Rushforth, Peter wrote:
> In the XML world, the answer to graphics rendering is SVG + XSL-FO,
> generated by XSLT scripts according to styling rules. XSL-FO
> is then rendered via a formatting objects processor, like Apache FOP.
OK, but... you do know that this is only true for small datasets.
For large datasets FOP is a bad choice performance wise.
For instance: if you have to convert an XML to a PDF and you
expect the end result to be 50 pages, Apache FOP might be a
good choice. If you expect 10,000+ pages, then it's a bad choice.
A document with 10,000+ pages is not as unusual as most PDF newbies
think. I've just created a PDF with 28,500 pages; each page is
a letter to one of the 28,500 students of Ghent University.
I've heard from banks that create PDFs with 100,000+ pages.
In this case, I use iText (obviously: I'm the developer of iText):
iText is used by Google, NASA, DoD,... It's purpose is to create
all kinds of PDF files as fast as possible.
> I'm of the opinion that a pipeline like:
> GML +/- (any XML data) + SLD/FE + WMS graphics => XSLT => SVG+XSL-FO ->
> pdf, (?geopdf anyone?)
XSLT? XSL-FO? What a performance killer!
> would make for a killer map scripting environment. Plus, it has the
> added benefit of being based on standards or de facto standards
> across the board, with open source solutions available in each
>> Use Cases:
>> I. Interactive Browsing (e.g. web mapping) 1. Good-looking
>> web maps (more control of grid/graticule
FOP doesn't support all PDF features.
For instance: I've made a map in PDF that shows a raster image
when you first open it. Then when you zoom in, the PDF automatically
switches to vector data.
FOP doesn't support OCG! iText does!
OCG = Optional Content Groups: meaning you can turn on and
off layers in a PDF file. For instance: you could add street
names to a map in English en French and define the OCG so that
only one language at a time is shown.
>> II. Ad-hoc Authoring (one-time GIS style layout using GUI)
>> 1. Good-looking printed (ps,pdf,etc) maps automatically
>> providing grid/grat, scalebar, legend, north arrow, SRS description
>> - provide an API to exiting GIS apps?
FOP isn't fast enough to create detailed PDFs on the fly.
>> III. Automated Mapping (script driven)
>> 1. Map Series (single page, identical layout) 2. Map Atlas
>> (mostly map with some text, multi-page) 3. Map-centric
>> documents (mostly text with some map,
>> 4. Route Alignment Sheets (rotated (non 90 deg) to fit
With iText you have direct access to all PDF operators and
operands. you can draw every shape you want.
Please download chapter 1 of my book:
There's an example of a map of a (fictive) city.
I hope you'll find it very interesting!
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