AGG and WMS

[Brent Fraser]

Christopher,

  Sorry for the terse question, here are some more
details...

I'm using the AGG/PNG output driver (see RFC-32) in
Mapserver 5.0 beta 4 to render shapefile vectors (no raster
input) to a PNG graphic file.  When I use Mapserver's CGI
interface to request a graphic map, the lines appear
anti-aliased (smooth, no jaggies) Great!  But when I use
Mapserver's WMS interface, I get the same old rendering
Mapserver always gave (lines with jaggies).

  Note there was an email
(http://lists.umn.edu/cgi-bin/wa?A2=ind0703&L=mapserver-dev&
T=0&O=D&X=639F0B08FDD720FAC9&P=6714) saying "WSM right now
only advertise gd and gdal based drivers. See bug 455".


  After some review of the images, it looks like my "DRIVER
AGG/PNG" produces a 24 bit png file via CGI, but an 8 bit
png file via WMS.  When I try to do AGG/PNG24, I get
"General error message. OUTPUTFORMAT clause references
driver AGG/PNG24, but this driver isn't configured." from
Mapserver.  I'll have to do some more digging...

Brent Fraser
GeoAnalytic Inc.
Calgary, Alberta

----- Original Message ----- 
From: "Christopher Schmidt" <crschmidt at METACARTA.COM>
To: <MAPSERVER-USERS at LISTS.UMN.EDU>
Sent: Thursday, August 23, 2007 1:03 PM
Subject: Re: [UMN_MAPSERVER-USERS] AGG and WMS


> On Thu, Aug 23, 2007 at 12:32:41PM -0600, Brent Fraser
wrote:
> > Is AGG supposed to do anti-aliased output when Mapserver
is
> > used as a WMS server?
>
> I'm not sure what 'antialiased' output means -- perhaps
you mean 'alpha
> transparency', perhaps you mean antialiasing within the
images, perhaps
> you mean something else. Can you clarify?
>
> The answer to the first is, I believe,  "no". WMS spec
only allows for
> 'transparency or no transparency', and MapServer does not
implement
> alpha transparency output in the WMS images.
>
> The answer to the second is "Sure" -- the images for
> http://boston.freemap.in/ are fetched from WMS (by
TileCache).
>
> Regards,
> -- 
> Christopher Schmidt
> MetaCarta