Ciao Tim,
please, find my aswer inline below....
Regards,
Simone Giannecchini
Ing. Simone Giannecchini
@simogeo
Founder/Director
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
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http://www.geo-solutions.it
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On Wed, Nov 28, 2012 at 4:08 PM, Tim Hayton <tim.hayton@anonymised.com> wrote:
I’ve just started using GeoServer/GeoWebCache to serve map imagery to web
clients which use the TMS service. My source images are in either GeoTIFF
or MrSid format, and are satellite imagery for adjacent areas which slightly
overlap. I have successfully set these up in GeoServer as data sources and
layers, and then made a Layer Group which combines each individual image
layer into a single group so I can easily get tiles for anywhere in the
coverage area via a single TMS request.
I would suggest to use the ImageMosaic plugin.
I am assuming the images have:
- same CRS
- same data type
- same number of bands
- similar resolution
With the ImageMosaic plugin you do not need to use the layer group and
your GetCapabilities will be much smaller.
ImageMosaic handle the transparent color both on put images as well as
on the output image. Check the layer configuration.
Last but not least it does handle MrSID as well as GeoTiff files.
My problem is related to nodata areas, which are black in the individual
images, at the borders of each image file where there is an overlap with the
next image. For the GeoTIFF layers, I can easily set the
InputTransparentColor in the GeoServer Layers -> Coverage Parameters screen,
and this works great with the combined layer group correctly serving the
actual data rather than the black pixels for tiles where two images overlap.
However, for my MrSid images, there is no InputTransparentColor option in
the Layers screen, and when I get border tiles with TMS requests I am often
getting the black pixels in preference to the actual data where tiles
overlap.
See suggestion above about using ImageMosaic. That said you are right
there is no support
for input transparent color on GDAL Formats. Could file a jira
enhancement report for this?
It would be dead easy to add it and I believe we should do it right away.
So my question is basically is there any way to set the
InputTransparentColor for layers based on MrSid data sources, or is there
something peculiar to this format that prevent this option from being set?
I also see the same problem if I get a tile layer preview from the web
interface, but interestingly if I ask for a layer preview (rather than a
tile layer preview) the I do not see the problem, and the image layers blend
correctly at the borders. I wonder then if the problem might be related to
the way GeoWebCache requests the images from GeoServer in a way that causes
the nodata to take preference somehow?
System details:
GeoServer 2.2.2 from windows installer
GDAL extensions
Windows XP
Oracle Java 1.7.0_09
Thanks in advance for any help!
Tim
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