Server side legend generation

[sypasche]

This is the Tree.server part. A client modification will also be needed.

There should be a way to generate legend images and labels automatically on the server. The WMS standard doesn't go as far as we would like for this situation (Get Legend Graphics? only an icon for the layers).

The protocol will have to be proprietary and the server side component specific to the map engine. In a first iteration, we could use Mapserver and Python Mapscript.

I think there was previous efforts going in this direction. I remember seeing somewhere a Python service generating something like XML from a mapfile. We would need to check what is available before starting implementation.