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

[mchapman at texelinc.com]

Maybe try generating an overview
(.ovr) file for the image. Perhaps the resampling will be better. Also see if you can specify in mapserver the resampling method to cubic convolution or something other than nearest neighbor.

Martin

 
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-----Original Message-----
From: "Roger André" <randre at gmail.com>

Date: Thu, 1 May 2008 21:20:04 
To:gdal-dev at lists.osgeo.org
Subject: [gdal-dev] What options for display of high-quality ortho's via WMS?


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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