[OSGeo-Discuss] Proposal: OSGeo Cartographic Library

Christopher Schmidt crschmidt at crschmidt.net
Sun Apr 13 05:58:37 PDT 2008

On Sun, Apr 13, 2008 at 11:18:48AM +0300, Ari Jolma wrote:
> I'm still very much interested in this. Cairo would provide a single API 
> 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.

I think that for the task you've described, looking into Mapnik might 
be a good idea.

> 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), 2), and 4) already exist in Mapnik. 3) seems to me like it can
either be added to Mapnik, or added via post-processing, without needing
to reimplement 1), 2) or 4).

> 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.

Mapnik has support for PostGIS and Shapefiles, but has a plugin-based
architecture for reading data, so I would not be surprised to find that
an OGR plugin for data access would be too difficult for someone
experienced in C++/C.

> 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?

I'd strongly recommend starting by looking at existing solutions. 

Christopher Schmidt
Web Developer

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