[OSGeo-Discuss] Proposal: OSGeo Cartographic Library

Traian Stanev traian.stanev at autodesk.com
Sun Apr 13 08:48:51 PDT 2008

Hello Ari,

> -----Original Message-----
> From: discuss-bounces at lists.osgeo.org [mailto:discuss-
> bounces at lists.osgeo.org] On Behalf Of Ari Jolma
> Sent: Sunday, April 13, 2008 4:19 AM
> To: OSGeo Discussions
> Subject: Re: [OSGeo-Discuss] Proposal: OSGeo Cartographic Library
> Markus Neteler kirjoitti:
> > Dear OSGeo,
> >
> > I would like to launch the idea of an "OSGeo Cartographic Library" to
> > share concepts, source code and regression tests:
> >
> > http://wiki.osgeo.org/wiki/OSGeo_Cartographic_Library
> >
> I proposed a year ago to develop a geospatial graphics library based on
> Cairo
> http://www.intevation.de/pipermail/freegis-list/2007-April/003142.html
> I'm still very much interested in this. Cairo would provide a single
> to render to an image buffer, on PDF and others. It has good support
> for
> rendering text with various fonts and there are high-level language
> APIs.
> Currently Cairo can be used in Geoinformatica to render geodata,
> legends, etc. on a map. I'm already using that a bit and will use it
> much more in the future.
> What I think is needed first, and would be the core content of the
> library is 1) a mapping of style information into Cairo commands, 2)
> capability to render cartographic symbols on maps, and 3) a mechanism
> to
> allow plugins that add legends etc. on the map, 4) symbol and label
> placement algorithms. Second need would perhaps be support for various
> geovisualization methods.
> 1) is rather straight-forward, I guess, using OGC Styled Layers
> standard
> 2) I'm not sure, there seems to be free resources like
> http://pubs.usgs.gov/of/1999/of99-430/ which offer symbols in EPS -- I
> don't find support in Cairo to render EPS on surfaces
> 3) is rather straight-forward
> 4) start from simple and existing codes
> Cairo is of course just one technology and not suited for all needs in
> this domain. Furthermore, the data provider can be made separate from
> the library, but I'd like to start with and use GDAL (OGR in fact) as
> the default.

Have you looked at the MapGuide rendering engine? It uses AGG as backend (AGG is faster and looks better than Cairo), however, the underlying graphics library is isolated via an interface and can be changed -- until last release we used GD in fact. We also have KML output for MapGuide using the same rendering interface.

In addition, MapGuide also has a style engine on top of the renderer, which can layout user-defined point, line and polygon styles. It also has a font layout component that is used for labeling things like paths and also for making sure labels don't overlap, etc. See MapGuide RFC 14 for some examples (http://trac.osgeo.org/mapguide/wiki/MapGuideRfc14).

The data input for MapGuide is FDO, however, that is also done via an interface which can be implemented on top of other data sources (OGR).

The engine is designed for interactive rendering speeds.


> Anyway, I'd like to finally get going with this and start drafting an
> API. Any ideas how to proceed? Set up a svn repository somewhere?
> Regards,
> Ari
> --
> Prof. Ari Jolma
> Geoinformatiikka / Geoinformatics
> Teknillinen Korkeakoulu / Helsinki University of Technology
> tel: +358 9 451 3886 address: POBox 1200, 02015 TKK, Finland
> Email: ari.jolma at tkk.fi URL: http://www.tkk.fi/~jolma
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