On jeudi 26 octobre 2017 18:57:10 CEST Markus Neteler wrote: > On Thu, Oct 26, 2017 at 9:25 AM, Markus Metz > > <markus.metz.gisw...@gmail.com> wrote: > > On Wed, Oct 25, 2017 at 10:40 PM, Markus Neteler <nete...@osgeo.org> wrote: > >> Hi devs, > >> > >> while playing with the SRTM 30m world I see that there is a difference > >> of 66GB in size between LZ4 (larger) and DEFLATE (smaller). While this > >> is not a surprise I was wondering if LZW compression could be brought > >> back. AFAIK the license issue is gone for a while and indeed GRASS got > >> a special permit back in 1988 according to the old source code. > >> > >> Would that make sense? > > > > You could test with compress (LZW) and gzip (DEFLATE based on LZ77) if > > that > > would make sense. > > > > Implementation would be a bit of an effort: either adapt from the source > > code of compress or from GDAL's LZW compression for Tiff. > > I thought to remember that the LZW compression was in libgis some > decades ago but did not find any trace so far. > At that point I happily abandon this idea - no need to waste energy here :-)
Another option would be to consider the zstd / zstandard compression method ( https://github.com/facebook/zstd ), that has roughly the compression ratio of DEFLATE / LZ77 with a compression and decompression speed 3 or 4 times faster. This is in my todo list of things to experiment as a libtiff compression method. Zstd has been added recently as a compression method in the Linux kernel: https://www.phoronix.com/scan.php?page=news_item&px=ZSTD-Linux-Kernel-Image Even -- Spatialys - Geospatial professional services http://www.spatialys.com
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