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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Can you let me download the image you are having issues with?
You want to have a pyramid of files that are varying levels. Ideally they
should be a factor of 2, i.e… 2, 4, 8, 16, 32 , 64, 128, 256, 512, 1024, 2048,
4096, … . What is the gsd of your base image?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas;
color:#1F497D'>Martin<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Roger André
[mailto:randre@gmail.com] <br>
<b>Sent:</b> Friday, May 02, 2008 2:54 PM<br>
<b>To:</b> mchapman@texelinc.com<br>
<b>Cc:</b> gdal-dev-bounces@lists.osgeo.org; gdal-dev@lists.osgeo.org<br>
<b>Subject:</b> Re: [gdal-dev] What options for display of high-quality ortho's
via WMS?<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>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>
<o:p></o:p></p>
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<p class=MsoNormal>On Thu, May 1, 2008 at 11:37 PM, <<a
href="mailto:mchapman@texelinc.com">mchapman@texelinc.com</a>> wrote:<o:p></o:p></p>
<p class=MsoNormal>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<o:p></o:p></p>
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<p class=MsoNormal><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<o:p></o:p></p>
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<p class=MsoNormal>-- _______________________________________________<br>
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