Well, generating overviews of the 8-bit data produced pretty awful looking results. gdaladdo did warn me, so I can't blame it. ;) Also changing the resampling to bilinear did not improve the matter.<br><br>Is it better to create large, single-image overviews, or to create many tiles of varying resolution levels?<br>
--<br><br><br><br><div class="gmail_quote">On Thu, May 1, 2008 at 11:37 PM, <<a href="mailto:mchapman@texelinc.com">mchapman@texelinc.com</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Maybe try generating an overview<br>
(.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.<br>
<br>
Martin<br>
<br>
<br>
Sent via BlackBerry by AT&T<br>
<div><div></div><div class="Wj3C7c"><br>
-----Original Message-----<br>
From: "Roger André" <<a href="mailto:randre@gmail.com">randre@gmail.com</a>><br>
<br>
Date: Thu, 1 May 2008 21:20:04<br>
<a href="mailto:To%3Agdal-dev@lists.osgeo.org">To:gdal-dev@lists.osgeo.org</a><br>
Subject: [gdal-dev] What options for display of high-quality ortho's via WMS?<br>
<br>
<br>
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.<br>
<br>
1. Is some loss of image quality an unavoidable side-effect of using Mapserver?<br>
<br>
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.)<br>
<br>
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.)<br>
<br>
Thanks in advance for your feedback.<br>
<br>
Roger<br>
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