Darafei, Are you seeing this when zoomed out with mapserver? If so I think what your seeing is actually caused by mapserver not by gdal. Try adding PROCESSING "RESAMPLE=AVERAGE" to your layers in the mapfile
Brian On Sun, 2011-10-30 at 00:00 +0300, Komяpa wrote: > Hi, > > 2011/10/29 Frank Warmerdam <[email protected]>: > > On 11-10-29 12:18 PM, Komяpa wrote: > >> > >> Still, there are some things I would like to clear / discuss. > >> > >> 1) gdaladdo final.tif 2 4 8 16 32 64 128 256 makes not beautiful > >> overviews. If I add -r average, some artifacts start appearing, like > >> the vertical stripes on the link above. Any good ways to fix that? > > > > Darafei > > > > I would be interested in reproducing this at my end and investigating. > > Could you provide something I can work with? I presume the issue > > relates to the average overview builder not understanding nodata > > masking. Are you using GDAL "trunk"? > > You can grab geotiffs from http://dev.latlon.org/tiff/baloon/ > Mapserver map file: http://dev.latlon.org/tiff/all.map > > I am using gdal 1.8.1-2~exp2 from debian experimental. > > > >> 3) JPEG compression artifacts. > >> Black field outside makes outmost blocks appear darker and be "dirty": > >> > >> http://latlon.org/maxi?zoom=18&lat=56.32465&lon=30.61984&layers=0000000000000FF0000FBT > >> This can be avoided, as far as I can see, in two ways: > >> a) easier one, on compression, if we fill NODATA region inside these > >> blocks not with black, but with bilinear average of other data inside > >> block, there will be no black blocks. > >> b) harder one, make custom jpeg decompressor that will take exact > >> value for nodata region into account and try to restore values for > >> DATA region (not sure if it's really possible). > >> > >> Same about compressing overviews. Probably nearblack can be patched to > >> fill regions not with black but with any kind of average, as > >> quick-and-dirty solution? > > > > I don't see this as the role of nearblack, but I can see it might > > be helpful to have a way of doing this to an image under the nodata > > mask as a distinct utility. Alternatively since this is mostly an > > issue with the jpeg compressor, perhaps just to do it within the > > geotiff through jpeg writing code in GDAL. > > Would be nice if geotiff jpeg writer can just fill NODATA region with > garbage that will help DATA look nicer (and compress better). > > > > Can you provide something that helps me isolate this problem to > > work on? > > > > Best regards, > > -- > > ---------------------------------------+-------------------------------------- > > I set the clouds in motion - turn up | Frank Warmerdam, > > [email protected] > > light and sound - activate the windows | http://pobox.com/warmerda > > and watch the world go round - Rush | Geospatial Software Developer > > > > > > _______________________________________________ > > talk mailing list > > [email protected] > > http://host134.hostmonster.com/mailman/listinfo/talk_openaerialmap.org > > > > > _______________________________________________ talk mailing list [email protected] http://host134.hostmonster.com/mailman/listinfo/talk_openaerialmap.org
