[gdal-dev] What options for display of high-quality ortho's via WMS?

Roger André randre at gmail.com
Fri May 2 00:20:04 EDT 2008


Throwing out a general question to this list because I know that many of us
use a variety of different applications to "get the job done", but use the
GDAL tools as the common unifier (at least I like to think so).  I'm putting
together a Mapserver-driven web map that uses OpenLayers to get data via
WMS.  It's all working quite nicely, except for my aerial photo layer, which
I am not incredibly pleased with.  Despite using every tweak I could find
(convert from RGB to 8-bit with pct2rgb.py, use OUTPUTFORMAT with
GD/PNG, and use "DITHER=YES" in mapfile, I cannot get a very high quality
rendition of the photo layer in my WMS output.  It looks grainy in areas
with solid color and generally a bit "pixelly".  So I have a couple of
questions.

1.  Is some loss of image quality an unavoidable side-effect of using
Mapserver?

2. If not 1, then are there other tweaks that can be done to further improve
the quality of my output?  (Note that I intend to use Tilecache, so maybe
slow initial performance may is an acceptable trade off, I dunno.)

3. If yes to 1, then what other open source tools do a better job of
rendering photo data?  (I intend to test some of the data in GeoServer, but
I haven't done so yet.)

Thanks in advance for your feedback.

Roger
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