Hi developers,
please assist Eric to test the new "flate" compression!
I am using it at home without problems. Certainly you
should make a backup of your data.
How to "upgrade":
- Uncompress all data in "old GRASS 5":
r.uncompress -u rastermap
- compile GRASS with flate method
cd src/libes/gis/
edit get_row.c put_row.c
comment in both files: "#define USE_LZW_COMPRESSION"
- run make install to affect the lib and all modules
- Try it: You can compress the uncompressed data then with
r.uncompress rastermap
We want to activate flate compression as default on
Dec. 17th, so a few days to report eventual errors are left.
Thanks
Markus
------ fwd -------
On Sun, Dec 10, 2000 at 10:00:56AM -0800, Eric G . Miller wrote:
On Sun, Dec 10, 2000 at 05:02:56PM +0000, Markus Neteler wrote:
> > But the whole idea is to remove all of the LZW code from GRASS. My
> > understanding is this will only affect people who have used earlier
> > versions of GRASS 5, so for users upgrading from GRASS 4, this won't be
> > an issue. I know it's a bit confusing and annoying for the user, but I
> > don't know how to simultaneously remove LZW from the GRASS codebase and
> > include it ;).
> Oh! You mean that LZW was introduced in GRASS 5? I didn't know that.
> So the GRASS 4.x didn't have LZW?I don't know exactly when it was introduced, there's no date or author
on the lzw.c file. However, CELL file use a totally different encoding
and compression scheme (RLE based). Only FP rasters use XDR encoding
and LZW compression. G3D uses an encoding similar to CELL files, with
optional RLE and LZW compression methods (I don't quite understand how
it works).> > My recommendation is that people run r.compress -u on all their FP
> > rasters before upgrading. I think it is the surest path. Exporting to
> > ASCII should not be necessary.
> I see.Yes, you can still preserve all the color and cats info...
> > > I'll keep working with flate now (currently I'm updating my satellite image
> > > radiometric/terrain correction module to GRASS 5, big job for me...).
> > > Maybe several problems interfere from time to time
> Up to now I didn't face any problems. Perhaps these stripes have been in the
> image. Currently I don't want to recompile again to LZW...Well, let me know. I wish we could get more people to try this out.
--
Eric G. Miller <egm2@jps.net>
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