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

[Roger André]

I just realized what I was doing wrong.  I kept the processing option in the
LAYER, and it was trumping the OUTPUTFORMAT in the MAP section.  Once I took
the DITHER="YES" out, the imagery looks great.

Still learning how this all works together, sorry for taking up your time.
--

On Fri, May 2, 2008 at 2:13 PM, Roger André <randre at gmail.com> wrote:

> I only have the app running on an internal server at the moment.  I will
> try to make a few WMS requests to generate images and will post the
> resulting output on an external box for you.  My GSD is 18", but I am
> probably going to increase that to 36" for the final product.
>
> Thanks.
> --
>
>
> On Fri, May 2, 2008 at 2:05 PM, Martin Chapman <mchapman at texelinc.com>
> wrote:
>
> >  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?
> >
> >
> >
> > Martin
> >
> >
> >
> > *From:* Roger André [mailto:randre at gmail.com]
> > *Sent:* Friday, May 02, 2008 2:54 PM
> > *To:* mchapman at texelinc.com
> > *Cc:* gdal-dev-bounces at lists.osgeo.org; gdal-dev at lists.osgeo.org
> > *Subject:* Re: [gdal-dev] What options for display of high-quality
> > ortho's via WMS?
> >
> >
> >
> > 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.
> >
> > Is it better to create large, single-image overviews, or to create many
> > tiles of varying resolution levels?
> > --
> >
> >
> >  On Thu, May 1, 2008 at 11:37 PM, <mchapman at texelinc.com> wrote:
> >
> > 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
> >
> >
> > Sent via BlackBerry by AT&T
> >
> >
> > -----Original Message-----
> > From: "Roger André" <randre at gmail.com>
> >
> > Date: Thu, 1 May 2008 21:20:04
> > To:gdal-dev at lists.osgeo.org <To%3Agdal-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
> >
> > -- _______________________________________________
> > gdal-dev mailing list
> > gdal-dev at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/gdal-dev
> >
> >
> >
>
>
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