Well, it didn't even occur to me to compress the overviews with translate... I was expecting a bit more compressing from lerc...
About tif 32bit, what compression do you think would yield better ratios? Thanks. Rahkonen Jukka (MML) <jukka.rahko...@maanmittauslaitos.fi> escreveu no dia quinta, 18/11/2021 à(s) 12:41: > Hi, > > > > I made some tests with an 8 bit RGB image. > > First observation was that gdaladdo supports lerc_deflate (even it is not > documented), but it does not support “MAX_Z_ERROR”. This yields same sized > ovr file with or without max_z_error. > > gdaladdo -ro lerc_def2.tif --config compress_overview lerc_deflate > --config MAX_Z_ERROR 10 > > > > Another observation was that this option would really save some disk > space. I compressed the lossless ovr file with gdal_translate by using -co > max_z_error=10 and file sizes were: > > > > source tiff: 432 072 372 bytes > > lecr_deflate cog without overviews: 311 258 085 bytes > > > > lossless lerc_deflate overviews: 118 954 009 bytes > > lerc_deflare overviews with z_error=10: 52 400 583 bytes > > > > For comparison even not relevant to original question about 32 bit data > > jpeg-ycbcr overviews with default quality: 14 481 967 bytes > > > > -Jukka Rahkonen- > > > > *Lähettäjä:* gdal-dev <gdal-dev-boun...@lists.osgeo.org> *Puolesta *Duarte > Carreira > *Lähetetty:* torstai 18. marraskuuta 2021 13.45 > *Vastaanottaja:* gdal-dev@lists.osgeo.org > *Aihe:* [gdal-dev] setting MAX_Z_ERROR on overviews compressed with > LERC_DEFLATE > > > > Hi there. > > > > I am looking into compressing overviews for a DEM, with LERC_DEFLATE and > it works. But I'm trying to set the precision loss and get better > compression, since for overviews I don't really care that much. > > Ok, so the question is how to set the MAX_Z_ERROR for overviews compressed > with LERC_DEFLATE? > > > > More context: > > My reasoning is to compress losslessly the dem with deflate predictor 3, > and then compress "lossly" the overviews with lerc_deflate. > > Since this is 32bit dataset, I can't use jpeg on the overviews. > > > > Thanks in advance. > > Duarte > > >
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