artemp/mapnik — Issue #769: efficient rendering of multilingual maps
Author: artemp
Created: 2011-10-11 16:36:01+00:00
State: open
Labels: MetaWriters

We (Wikipedia-people) try to render Openstreetmap in a lot of languages (nearly 270): [[BR]]
[http://toolserver.org/~osm/locale/ http://toolserver.org/~osm/locale/]

The way with so many parallel mapnik styles is very inefficient and the new complete re-rendering for each language needs a lot of resources. So the idea is to make it more clever:[[BR]]
*Render a base-tile only once without all names that need a translation. Use something like Metawriter to save all names that are in different languages with there positions and save collision-areas (areas where no label should be). [[BR]]
*In the second step render only the names in the right language with the help of the metawriter data (without a new database request). Use the base-tile as background. Prevent collision with labels in the background and with other names. [[BR]]
*Store the final tile or if creation is very fast render it on each request.

The restart of mapnik needs with more than 270 styles in the moment nearly 15 minutes. So it would be better to have only one style with a language parameter. (But this point is not so important.)

After a talk with the creator of Metawriter, I know that this wish is not easy to fulfil, but perhaps somebody think that it is charming. There are a lot of use cases where multilingual maps are important (use it in schools for childrens, use Openstreetmap for orientation e.g. in asia, compare Openstreetmap with historial maps...).

Perhaps this is also a project-idea for GSoC next year, but it would be nice to get a earlier result because we still have the Openstreetmap map still in more than 5 Wikipedia language versions. [http://de.wikipedia.org/wiki/Hilfe:OpenStreetMap/en]