Transparency

[Doug Nebert]

Steve, mapserv-users:

The GD library seems to produce GIF87 and not GIF89a which is able
to be transparent. We would like to exploit this feature in order to 
make the layers served usable in the OGC Web Mapping Service. 

Two ideas:

1. Can a converter be inlined in the output generation of every 
graphic? If so, then we could adapt the request to support possibly
more than one output format. This is in the spirit of the WMS where
the format is a request argument. Although only one format needs to
be supplied, it is possible for a requestor to prefer a given format
and for a map server to supply more than one for the same content.

2. Another way would be to make PNG and assign transparency
that way, though I am reluctant to go to so new a graphics reference.

My preference would be an architecture that supports the first case.
What is your advice?

Doug.

-- 
Douglas D. Nebert
Geospatial Data Clearinghouse Coordinator 
FGDC Secretariat	Phone: +1 703 648 4151	Fax: +1 703 648-5755	
Pager Messaging: 	http://clearinghouse3.fgdc.gov/dougmsg.html