CGI Mapserver: raw URL zooming manipulation

[Matthew Pettis]

Hi,

I am trying to just do raw CGI calls to do some zooming (trying to see what
the necessary raw CGI controls are to do certain functions, don't want to
use templates to do zooming just yet until i understand this), but can't
seem to do it.  I try to pass a zoom parameter in, but I always get the map
image of the extent set in my .map file.  Can someone help me with the right
incantation I need to pass in the address bar?

here's what I have tried to no avail:

relevant mapfile settings (what i think is relevant):
---------------------------------------------------------------------------
    ################
    # Map attributes
    ################
  IMAGETYPE   PNG
  EXTENT      189775.375 4810000 761662.375 5472414.5
  SIZE        660 495
---------------------------------------------------------------------------


=========================
url (no zoom) that works:
------------------------------------
http://localhost/cgi-bin/mapserv.exe?map=C:/ms4w/Apache/htdocs/tst/race.map&layer=county&mode=map
result:
---------
the right map of full extent is displayed in my browser

...

url:
----
http://localhost/cgi-bin/mapserv.exe?zoom=2&img.x=330&img.y=247.5&mapext=&189775.375+4810000+761662.375+5472414.5&map=C:/ms4w/Apache/htdocs/tst/race.map&layer=county&mode=map

result:
---------
msDrawMap(): Image handling error. Unable to initialize image.
msCalculateScale(): General error message. Invalid image extent, minx=-
1.000000, miny=-1.000000, maxx=-1.000000, maxy=-1.000000.
msCalculateScale(): General error message. Invalid image extent, minx=-
1.000000, miny=-1.000000, maxx=-1.000000, maxy=-1.000000.

=========================


-- 
It is from the wellspring of our despair and the places that we are broken
that we come to repair the world.
-- Murray Waas
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