Improve legend icons resolution for GeoServer WMS

[mapfish]

Improve legend icons resolution for GeoServer WMS

[severo]

Note 1: GeoServer's default resolution is ~90dpi (25.4/0.28), and to print legend icons with the same size as corresponding map icons, the defaultScale parameter in config.yaml should be set to 0.7937 (72 dpi / ~90dpi), since scale = 1 corresponds to scaling 1px to 1pt (ie 1/72 inch).

Note 2: LEGEND_OPTIONS=dpi:${dpi} could be added by MapFish to the URL, and later ${dpi} value could be used to scale back to PDF dimensions space, the same way as it's done for the map. Three conditions:

• only works for WMS layer,
• only works if icon url corresponds to GetLegendGraphic request
• only works with GeoServer

Note 3: MapServer does not give hints on default dpi of the images created with WMS GetLegendGraphic request - see http://mapserver.org/mapfile/legend.html. Neither there is a mention to a parameter equivalent to GeoServer's LEGEND_OPTIONS=dpi:${dpi}.