[mapserver-users] Class level Transparency/Opacity

[Varun saraf]

Hello,

Is it possible to set a transparency rate for the CLASS level Color?
Below is my mapfile. I am using this layer on google maps in tile
mode. When I do so, the base map is getting completely overlapped by
the colored polygons. I need a level of transparency so that the base
map's roads and location are visible. In other words, I only want to
highlight the polygons that match the expression criteria. Can someone
tell me what I need to do for the same? I have already tried putting
in OPACITY field in the layer object but it only lightens the color
without making it transparent. an OPACITY of 1 renders the polygons
"white" in color.

MAP
   NAME drawBothMap
   TRANSPARENT ON
   IMAGETYPE PNG

   PROJECTION
     "init=epsg:4326"
   END

   LAYER
       NAME "USABOTH"
       STATUS DEFAULT
       METADATA
           wms_title "example_layer"
       END
       TYPE polygon
       DATA USA

       CLASSITEM "QCT"

       CLASS
         EXPRESSION '1'
         COLOR 255 0 0
       END

       CLASS
         EXPRESSION '2'
         COLOR 0 255 0
       END

       CLASS
         EXPRESSION '3'
         COLOR 0 0 255
       END
   END
END

Thanks,
Varun