[mapserver-users] Two questions about WMS and outputformats

[Rahkonen Jukka]

Hi,

By default, without having any OUTPUTFORMAT sections in the mapfile,
Mapserver is advertising following imageformats in WMS GetCapabilities
document:

 <GetMap>
      <Format>image/gif</Format>
      <Format>image/png</Format>
      <Format>image/png; mode=24bit</Format>
      <Format>image/jpeg</Format>
      <Format>image/vnd.wap.wbmp</Format>
      <Format>image/tiff</Format>
      <Format>image/svg+xml</Format> 

Some users have been confused because WMS client builds menu items
according to that list, but at least "image/png; mode 24bit" and
"image/tiff" do not give any output. What is the reason to include these
formats in getCapabilities by default, if they do not work without
creating OUTPUTFORMATs in the mapfile first?

Second question is about JPEG outputformat. It works through GD with
these settings
 OUTPUTFORMAT
      NAME "jpeg"
      MIMETYPE "image/jpeg"
      DRIVER "GD/JPEG"
      EXTENSION "jpg"
      IMAGEMODE RGB
 END

If I change driver to "GDAL/JPEG" I get this error on ms errorlog
[Mon Mar 16 11:16:05 2009].825000 msSaveImageGDAL(): General error
message. Failed to create output JPEG file.
JPEG driver doesn't support 4 bands.  Must be 1 (grey) or 3 (RGB) bands.

What makes GDAL/JPEG driver to believe that I want 4 bands? Or is it
just best to use DG/JPEG always?

-Jukka Rahkonen-