OSMTileProxy

OSMTileProxy

OSMTileProxy is a caching proxy for map tiles from Openstreetmap or another map tiles provider.

It exposes endpoint /tiles/{provider}/{level:int}/{x:int}/{y:int} returning an image for given tile coordinates. First it loads a tile from the provider, stores it to the disk cache, and then uses this image until it expires.

Configuration

Configuration section Tiles in the appsettings.json contains everything required for proxying and caching.

    "Tiles": {
        "Cache": "/var/www/tiles",
        "Providers": [
            {
                "Id": "osm",
                "Url": "https://tile.openstreetmap.org/{0}/{1}/{2}.png",
                "UserAgent": "Your-user-agent",
                "ContentType": "image/png",
                "UseWebp": false,
                "MinZoom": 1,
                "MaxZoom": 19
            }
        ]
    }

Below is the explanation of the section parameters.

Cache - folder where tiles are cached, in development configration appsettings.Development.json it is c:temptiles, make sure c:temp exists or specify another location.
Providers - array of provider parameters.
Providers:[i]:Id - arbitrary identifier of the provider, used in the endpoint, for example /osm/2/1/1.
Providers:[i]:Url - providers endpoint pattern, where {0} is level (map zoom), {1} - x-coordinate of a tile, {2} - y-coordinate of a tile.
Providers:[i]:UserAgent - is mandatory for Openstreetmap service, specify your unique User-Agent.
Providers:[i]:ContentType - value of Content-Type header in response, when UseWebp (see below) is true this header is always set to image/webp.
Providers:[i]:UseWebp - optional parameter (default value is false). When true, OSMTileProxy converts tile images to webp format.
Providers:[i]:MinZoom - optional parameter (default value is 1). Specifies minimum zoom level for tiles provider, used for validation.
Providers:[i]:MaxZoom - optional parameter (default value is 19). Specifies maximum zoom level for tiles provider, used for validation.

Deployment notes

If deployed as docker container, bind cache directory to your container, for example

docker run -p 8080:8080 --name osmtileproxy -v /var/www/tiles:/var/www/tiles -d osmtileproxy:latest