Mapnik Stylesheet with URLs to assets?

Question

Example:

<PointSymbolizer transform="scale(0.5)" file="Traffic_Congestion_ORANGE_InMap.png" ignore-placement="true"/>

Here the file value seams only to be a local path (on the local filesystem)

Is there a way to specify the png via URL? A S3 URL for example?

Answer 1

I don't believe it is possible to use a URL there.

I don't know much about C++, but have a quick look at Mapnik's source code here:

In map_parser::parse_point_symbolizer (line 950 in load_map.cpp) the symbolizer file name is checked with ensure_exists(filename) (line 1661). That function calls mapnik::util::exists.

mapnik::util::exists then calls boost::filesystem::exists (lines 41ff in fs.cpp).

The Boost Filesystem documentation doesn't mention URLs or HTTP calls anywhere, it is used only for files and paths on the local file system.

I haven't looked at other parts of the code much, but at least in the part where the file path is checked, an URL would cause an error.