[GRASS-dev] Re: gdalwarp -co COMPRESS issues

Maciej Sieczka tutey at o2.pl
Fri Mar 14 17:49:31 EDT 2008

Frank Warmerdam pisze:
> Maciej Sieczka wrote:

>> It is very important for all gdalwarp users. 

> I disagree with the above statement.  I think it is a small
> segment of people who create compressed files with gdalwarp, and
> there is a fairly straightforward workaround (warp then compress).

Since gdalwarp supports compressing tiffs, who would guess he has to do 
something extra? gdalwarp makes an impression of being able to warp and 
compress in one step. Not many users will expect that gdalwarp writes a 
compressed TIFF bigger than not compressed, and that he has to fix this 
with gdal_translate afterwards.

Moreover, I wonder if the guts of the issue that gdalwarp handles 
compression wrong, might also affect GDAL-dependent software. Eg. 
r.out.gdal in GRASS - I took the sample [1], imported into GRASS and 
re-exported with:

r.in.gdal in=M-33-21-A-b-4.tif out=M-33-21-A-b-4 -o
g.region rast=M-33-21-A-b-4.red -a
r.out.gdal in=M-33-21-A-b-4 out=M-33-21-A-b-4_gr_lzw.tif 
-createopt="COMPRESS=LZW" type=Byte

which created an LZW-compressed TIFF 2.33 times bigger than the 
original, also LZW-compressed. Could this r.out.gdal issue be related to 
gdalwarp issue?


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