POLYGON layers not transparent with imagetype JPEG

[Bart van den Eijnden]

Hi,

JPEG does not support transparency. Try png or gif.

Best regards,
Bart

> Hello!
>
> Until recently, we were using Mapserver 3.6.6 to run our web applications.
> Now we installed a new web server with all new software, including
> Mapserver 4.2.5:
>
> MapServer version 4.2.5 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP
> SUPPORTS=PROJ SUPPORTS=FREETYPE SUPPORTS=WMS_SERVER INPUT=EPPL7 INPUT=OGR
> INPUT=GDAL INPUT=SHAPEFILE
>
> We noticed an interesting problem with our applications: when we use some
> layer of type POLYGON which is filled with some kind of SYMBOL, this layer
> is not transparent. Here's an example snippet of a .map file (I omitted
> most of the layers for brevity):
>
> ------------------------------ CUT ------------------------------
> NAME tartu
> SIZE 420 420
> STATUS OFF
> IMAGECOLOR 255 255 255
> IMAGETYPE JPEG
> EXTENT 6000 3000 15000 12000
> UNITS METERS
> SHAPEPATH "/home/httpd/html/www.tartu.ee/mapserv/data"
> SYMBOLSET "/home/httpd/html/www.tartu.ee/mapserv/symbols/symbol.sym"
> FONTSET "/home/httpd/html/www.tartu.ee/mapserv/symbols/fonts.list"
>
> LAYER
>   NAME krundipiirid
>   TYPE POLYGON
>   STATUS off
>   DATA tartu_region
>   CLASSITEM 'aadress'
>   CLASS
>     NAME 'Krundid'
>     EXPRESSION /./
>     SYMBOL cross
>     SIZE 4
>     OUTLINECOLOR 151 170 119
>     COLOR 235 255 211
>   END
>   HEADER "krundipiirid_header.html"
>   FOOTER "krundipiirid_footer.html"
>   TEMPLATE "krundipiirid.html"
> END
>
> LAYER
>   NAME T2000
>   GROUP pilt
>   STATUS OFF
>   TILEINDEX t2000
>   TYPE RASTER
>   MAXSCALE 1500
>   MINSCALE 100
>   OFFSITE 255 255 255
> END
> ------------------------------ CUT ------------------------------
>
> Symbol cross is defined like this in the SYMBOLSET:
>
> ------------------------------ CUT ------------------------------
> SYMBOL
>   NAME "cross"
>   TYPE vector
>   POINTS
>     2 0
>     2 4
>     -99 -99
>     0 2
>     4 2
>   END
> END
> ------------------------------ CUT ------------------------------
>
> Now, if we display both layers 'krundipiirid' and 'T2000' simultaneously,
> the objects in 'krundipiirid' layer completely cover the raster layer,
> whereas on our old server the raster could be seen through the objects in
> 'krundipiirid'.
>
> After a lot of hair-pulling, I noticed that this only happens if I specify
> IMAGETYPE JPEG. When specifying IMAGETYPE PNG (or not specifying IMAGETYPE
> at all), the layers behave as on our old server.
>
> In some cases, I could work around the problem by adding TRANSPARENCY to
> the polygon layer, but in some cases even this didn't help.
>
> I also tried briefly with Mapserver 4.4.0, but the behaviour seemed to be
> the same there. Since our .map files had other problems with 4.4.0, I went
> back to 4.2.5 for now.
>
> I am actually not an web/application developer but merely a server
> administrator, so I apologize in advance if I'm missing something
> blatantly
> obvious. I've been forced to deal with this since the developers are
> currently unreachable. A fun week this has been.
>
> --
> Toomas Aas
>