Sounds also interesting for historical OSM, where we could use a time or a time span as parameter.
Greetings Tim alias Kolossos Am 14.10.2013 18:40, schrieb Kai Krueger: > Hello everyone, > > I would like to mention that I have committed a new feature to mod_tile > / renderd and would appreciate any feedback or comments. > > Mod_tile and renderd are now prepared for the possibility to > parameterize the mapnik style-sheet on the fly on a (meta)tile by > (metatile) basis. > > For this purpose, the URL schema for tileservers was extended. It now > takes the form: > > https://my.tile.server/style/parameters/z/x/y.ext > > parameters is an arbitrary string that gets passed on to renderd and can > be used to parameterize the style-sheet for that rendering request. > > The first use for this functionality is to make it easy to offer > multi-lingual maps. I.e. to be able to specify (parameterize) the > language in which the names should appear on the map. E.g. one can > specify that English names (name:en) should be used instead of the plain > name tag. > > This is heavily based upon Jochen Topf's work on the multi-lingual > project for wikimedia [1,2], that has shown the feasibility of this > concept. By integrating it into mod_tile / renderd and making it trivial > to enable, it will hopefully see wider adoption and prove useful to a > bigger audience. > > You can specify an ordering of name tags to be used when trying to > render any labels. E.g. de,en,_ will use name:de if available, otherwise > try name:en and finally use name if neither name:de or name:en is > available. Technically, renderd will take the stylesheet it loads and > replace name in the sql queries with coalesce(tags->'name:de', > tags->'name:en', tags->'name') as name. > > > Everything should be backwards compatible and one can activate this > feature on a style-by-style basis. If not activated, the old URL schema > continues to be used. > > So e.g. a server can support https://my.tile.server/osm/0/0/0.png and > https://my.tile.server/osm-multilingua/de,en,_/0/0/0.png. > > > To make this possible, the protocol between mod_tile and renderd was > extended to include the parameterization string (as well as pass through > mime information for future purposes, e.g. to be able to render both png > and jpg). However, again, everything (both mod_tile and renderd) should > be backwards compatible. I.e. renderd can receive rendering requests > with the previous version of the protocol, in case you only want to > update renderd and still have an older version of mod_tile (or indeed > another server software or utility for issuing render requests). > Likewise, mod_tile can still send the requests in the previous protocol, > and indeed will do so by default unless the parameterization feature is > explicitly activated for the given style. This should ensure > compatibility with tirex, that has not yet been updated to the change in > protocol. > > Although its first use is for the multi-lingual maps, hopefully this > feature can be used for other purposes as well. You still need to write > code to interpret the parameterization string and apply the > transformation to the mapnik stylesheet object, but given that is all > encapsulated in a separate file, this will hopefully be relatively easy > if one needs it. > > Kai > > > > > > [1] > http://blog.jochentopf.com/2012-06-21-wikipedia-multilingual-maps-project.html > [2] > http://blog.jochentopf.com/2012-12-19-status-of-the-multilingual-maps-project.html > _______________________________________________ dev mailing list [email protected] https://lists.openstreetmap.org/listinfo/dev
