[GRASS-dev] GRASS GIS raster files: LZW compression?

[Seth Price]

Also, it's worth remembering that LZ4 is not intended for file size. It's
there because it decompresses at least an order of magnitude faster than
LZW.

On Thu, Oct 26, 2017 at 10:23 AM, Even Rouault <even.rouault at spatialys.com>
wrote:

> 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.giswork at gmail.com> wrote:
>
> > > On Wed, Oct 25, 2017 at 10:40 PM, Markus Neteler <neteler at 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
>
> _______________________________________________
> grass-dev mailing list
> grass-dev at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/grass-dev
>



-- 

*Seth Price*

Director of Putting the Pixels Where They Belong
Satellitenfernerkundungsspezialist

*Planet Labs*

Email: seth at planet.com
Phone: (608) 335-8068
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/grass-dev/attachments/20171026/29a937ca/attachment.html>