[GRASS5] 5.7: make GRASS_INT_ZLIB default?
neteler at itc.it
Mon Nov 22 12:54:51 EST 2004
On Fri, Nov 19, 2004 at 06:02:25PM +0000, Glynn Clements wrote:
> Markus Neteler wrote:
> > proposal for 5.7-CVS: make zlib compression instead of RLE the
> > default setting, probably modifying:
> > grass57/lib/gis > grep GRASS_INT_ZLIB *
> > opencell.c: COMPRESSION_TYPE = getenv("GRASS_INT_ZLIB") ? 2 : 1;
> > Are there objections?
> The most obvious problem is that raster maps will be unreadable on
> versions of GRASS which pre-date the addition of zlib support.
> Also, I don't know whether that feature has received any significant
Here some numbers:
- compression at 50% of the standard GRASS CELL file compression
57MB color channel -> 28 MB with ZLIB
233MB panchromatic channel -> 127 MB with ZLIB
This is quite an advantage when dealing with lots of remote sensing
- display time (over NFS network in both cases):
beforehand: g.region rast=channel
time d.rast color_channel_standard_compression
time d.rast color_channel_zlib_compression
time d.rast pan_channel_standard_compression
time d.rast pan_channel_zlib_compression
Interestingly there is less difference the larger the map.
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