Colin Wetherbee schreef:
I would like my first step to be putting a static image on a web site.
The image would be generated by Perl and returned to the browser as a
simple image/png.
The method I have in mind follows.
Each user has a set of airports and routes with which they are
concerned. This set of airports and routes could change as frequently
as every 30 seconds. So, for each map generation request, I would
dynamically create a map file and store it as TEXT in my PostgreSQL
database, along with some unique ID. Then, I would output an <img />
tag to the browser that includes the unique ID of this
dynamically-generated map file:
Interesting approach. But you could also try:
http://www.someserver.org/cgi-bin/mapserv.exe?map=ergens.map&REQUEST=getmap&Layers=layer1,layer2,layer3&User=MyUser&Airport=1,5,23,56&airline=KLM&;......
The mapfile is able to read user variables; this means
that the value MyUser that is in the variable User can be addressed in
the mapfile with %User%
Thus making it possible to have a layer that builds it's content from a
postGIS query dynamically like:
SELECT(THE GEOM) FROM Airports where ActiveUser=%User
This way you don't need to store mapfiles in the database and let the
form-variables in your webpage feed the dynamic content of the map.
Read the topic on
http://mapserver.gis.umn.edu/docs/reference/mapfile/variable_sub
The time stamp can also be set on a layer through a variable like this.
<img src="/foo/mapImage.pl?id=1234" />
mapImage.pl sees id=1234, pulls map file 1234 out of the database,
uses the MapServer back-end to generate a map, then outputs this map
as an image/png. I think mapImage.pl ends up being pretty simple:
create a mapserver object, pipe the map file text to it, and get the
png it generates. Is that it, or am I thinking too narrowly here?
I may include a time stamp, too, so I can expire map files after some
length of inactivity.
Does this sound about right?
Thanks for your help. :)
Colin
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