MapServer seems to always use GDAL driver with cascaded WMS (instead of AGG)

[elzouavo]

Hi,

I have some troubles using AGG with cascaded WMS.

I have my first mapfile that exposes WMS layers (MapServer is used as a WMS server and a WMS client): refs.map

I have a second mapfile that contains a Postgis layer (this mapfile uses only MapServer as WMS server): roads.map

I'm using MapServer 5.6.0 beta 3 on Debian (to avoid WFS requests issues with the folowing versions). But I have the same problem with 5.6.3. I advertise raster formats with "GetMap formats" to use AGG driver. I can get nice PNG with AGG when I request directly my second mapfile roads.map (using mapserver only as WMS server). But if I request my first mapfile refs.map (that then requests my second mapfile using MapServer as WMS client), I get PNG with bad aliasing (AGG does not seem to be used!).

I looked at the mapserv.log (for the WMS/GetMap that requests the cascaded WMS) and I saw : "msDrawGDAL(): red,green,blue,alpha bands = 1,2,3,4"

Does "msDrawGDAL" meen that DGAL driver is used instead of AGG driver ?

Thanks for your reply. Laurent NB : Sorry for my poor English...

An extract of my first mapfile (refs.map):

MAP
...
   OUTPUTFORMAT
     NAME "PNG"
     DRIVER "AGG/PNG"
     MIMETYPE "image/png"
     IMAGEMODE RGBA
     TRANSPARENT ON
   END
   ...
   WEB
     ...
     METADATA
        ...
        "wms_getmap_formatlist" "image/png,image/jpg,image/jpeg"
     END
   END
   LAYER
     NAME "my_layer"
     ...
     CONNECTIONTYPE WMS
     "http://my_domain/cgi-bin/mapserv?map=/my_path/roads.map";
     METADATA
       WMS_NAME "my_roads"
       "wms_server_version"  "1.1.1"
       "wms_format" "image/png"
       ...
     END
   END
   ...
END

An extract of my second mapfile (roads.map) :

MAP
...
   OUTPUTFORMAT
     NAME "PNG"
     DRIVER "AGG/PNG"
     MIMETYPE "image/png"
     IMAGEMODE RGBA
     TRANSPARENT ON
   END
   ...
   WEB
     ...
     METADATA
        ...
        "wms_getmap_formatlist" "image/png"
     END
   END
   LAYER
     NAME "my_roads"
     ...
     CONNECTIONTYPE    postgis
   ...
   END
...
END

I'm not sure that this behavior should be different with mapserver 6.0...

NB: I've already post this message on Tue, 27 Apr 2010 in the mailing list, but no reply... ;-(

[elzouavo]

PNG with direct WMS access and an other with cascading access