Ander, You'll have to store the coordinates yourself. Because you needed the coordinates to request the tile in the first place, you already have them -- you just need some way of associating the coordinates with the tile.
When caching I don't think you need to store the coordinates explicitly -- you would probably use the coordinates as a key and the tile's JSON contents as a value. One thing you can do if you want to cache tiles on disk is store them as individual files in directories. Conceptually, you would store the tile with coordinates z=16 x=32744 y=21792 in "/path/to/cache/16/32744/21792.js". This won't work well as you cache more and more tiles, because there will be a lot of files in these directories. mod_tile uses a hashing scheme to avoid this problem: https://github.com/openstreetmap/mod_tile/blob/a39905d1957fd37cba0aa3a4ec7302ba4865b34c/dir_utils.c#L68 Another approach is to use a hash (like SHA1) of the tile's contents as a cache key, and maintain a mapping between coordinates and hashes. This avoids storing tiles twice which have the same content. There's a brief description of this approach here: http://mapbox.com/developers/mbtiles/#using_views_to_reference_redundant_images -- Michael On 2012-08-20, at 3:09 AM, Ander Pijoan <[email protected]> wrote: > Hi! I have a big question: > > Imagine I download one of the tiles and keep it in my hard drive or in > a cache or send it to a client to open it in a program. The tiles > bounding box or X,Y,Zoom values are not in it so it won't be able to > know where to place that tile. > > I know that when asking for the tile I have those X,Y and Zoom values > so I can calculate its position but if it is not written anywhere in > the tile. I made some tests with Kothic's tiles allocated at > Osmonimski.ru and those tiles at least have their bounding box and > also their X,Y and Zoom values explicit in them. > > > > 2012/8/17, Michael Daines <[email protected]>: >> Hi everyone, >> >> An example data tile server covering the British Isles is now online: >> >> http://data-tiles.mdaines.com/ >> >> The library I have been working on is rendering tiles as a Tirex backend >> using OpenStreetMap data. The map is drawn using Kothic JS over top of image >> tiles rendered with Mapnik which show land polygons (basically the contents >> of the layer-shapefiles.xml.inc file in OSM's Mapnik stylesheet). >> >> Here is an example data tile: >> >> http://data-tiles.mdaines.com/render/16/32744/21792.js >> >> The data in the tileset is defined by this configuration file which uses a >> DSL that works sort of like CSS selectors: >> >> https://github.com/mdaines/cover/blob/master/config/render.rb >> >> >> -- Michael >> >> >> _______________________________________________ >> dev mailing list >> [email protected] >> http://lists.openstreetmap.org/listinfo/dev >> > > > -- > Ander Pijoan Lamas > Ingeniero Técnico en Informática de Gestión > Universidad de Deusto > > Contacto: > Email: [email protected] > Móvil: +34 664471228 _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
