For external WMS requests, read and use the width parameter value from the local GetCapabilities XML when crafting a GetLegendGraphic request

Currently GetLegendGraphic requests in OLIVER do not include a width parameter. 
 However, when making requests to external WMS servers which are backed by 
ArcGIS Server the legend is often cut off.  For example:

http://csc.noaa.gov/ArcGISPUB/services/MultipurposeMarineCadastre/MultipurposeMa
rineCadastre/MapServer/WMSServer?TRANSPARENT=TRUE&FOO=Shipping%20Fairways%2C%20L
anes%2C%20and%20Zones&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetLegendGraphic&EXCEPTI
ONS=application%2Fvnd.ogc.se_xml&LAYER=83&SCALE=2183916.2728723255&FORMAT=image%
2Fgif

results in the attached image external_ags_wms_legend_no_width_specified.gif

Since the GetCapabilities .xml of each external WMS is stored locally on the 
maps server we can edit the file and specify an appropriate width for each 
legend. For example in 
http://maps.massgis.state.ma.us/map_ol/noaa_mmc_public_wms_getcaps_20121212.xml 
we have specified 

LegendURL width="350" 

for the layer Shipping Fairways, Lanes, and Zones.

We suggest that OLIVER detect this and use the value to append &width=value to 
the GetLegendGraphic URL.  But only for ArcGIS Server backed WMS.

See the fixed example 
http://csc.noaa.gov/ArcGISPUB/services/MultipurposeMarineCadastre/MultipurposeMa
rineCadastre/MapServer/WMSServer?TRANSPARENT=TRUE&FOO=Shipping%20Fairways%2C%20L
anes%2C%20and%20Zones&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetLegendGraphic&EXCEPTI
ONS=application%2Fvnd.ogc.se_xml&LAYER=83&SCALE=2183916.2728723255&FORMAT=image%
2Fgif&width=350

and the result attached as external_ags_wms_legend_width_specified.gif

The reason why it's important to only add width to ArcGIS Server-backed WMS is 
that adding width to a GeoServer backed WMS will stretch the swatches 
unacceptably.  Compare the following 2 URLs.

no width with GeoServer:

http://giswebservices.massgis.state.ma.us/geoserver/wms?TRANSPARENT=TRUE&STYLE=G
ISDATA.LANDUSE_POLY%3A%3A21_Classes_1971_Solid&FOO=Land%20Use%201971%2021%20Clas
ses&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetLegendGraphic&EXCEPTIONS=application%2F
vnd.ogc.se_xml&LAYER=massgis%3AGISDATA.LANDUSE_POLY&SCALE=17061.845881815043&FOR
MAT=image%2Fgif

attached as geoserver_wms_legend_no_width_specified.gif

width with GeoServer:

http://giswebservices.massgis.state.ma.us/geoserver/wms?TRANSPARENT=TRUE&STYLE=G
ISDATA.LANDUSE_POLY%3A%3A21_Classes_1971_Solid&FOO=Land%20Use%201971%2021%20Clas
ses&VERSION=1.1.1&SERVICE=WMS&REQUEST=GetLegendGraphic&EXCEPTIONS=application%2F
vnd.ogc.se_xml&LAYER=massgis%3AGISDATA.LANDUSE_POLY&SCALE=17061.845881815043&FOR
MAT=image%2Fgif&width=100

attached as geoserver_wms_legend_width_specified.gif

In order to determine if the WMS is ArcGIS Server-backed I suggest we add the 
keyword "ArcGIS Server" to our local GetCapabilities XML file for that external 
WMS service.  See 
http://maps.massgis.state.ma.us/map_ol/noaa_mmc_public_wms_getcaps_20121212.xml

Original issue reported on code.google.com by Aleda.Fr...@state.ma.us on 17 Dec 2012 at 3:41

Attachments:

nakijun / morisoliver

For external WMS requests, read and use the width parameter value from the local GetCapabilities XML when crafting a GetLegendGraphic request #184