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 > -- Darafei "Komяpa" Praliaskouski OSM BY Team - http://openstreetmap.by/ xmpp:[email protected] mailto:[email protected] _______________________________________________ talk mailing list [email protected] http://host134.hostmonster.com/mailman/listinfo/talk_openaerialmap.org
