[GRASS-dev] TIFF output size: r.out.gdal vs gdal_translate

[Maciej Sieczka]

Glynn Clements pisze:
> Maciej Sieczka wrote:
> 
>> I've noticed that r.out.gdal creates GeoTIFFs significantly larger than
>> gdal_translate. Could this be avoided?
>>
>>
>>
>> Example, in spearfish60:
>>
>> $ r.out.gdal in=landcover.30m out=landcover.30m.tif type=Byte
>> $ ls -l landcover.30m.tif
>> -rw-r--r-- 1 shoofi shoofi 303978 sie 20 11:49 landcover.30m.tif
>>
>> $ gdal_translate landcover.30m.tif landcover.30m_gt.tif
>> $ ls -l landcover.30m_gt.tif
>> -rw-r--r-- 1 shoofi shoofi 300220 sie 20 11:49 landcover.30m_gt.tif
>>
>>
>>
>> Applying compression makes the difference more distinct:
>>
>> $ r.out.gdal in=landcover.30m out=landcover.30m.tif type=Byte 
>> createopt="COMPRESS=DEFLATE"
>> $ ls -l landcover.30m.tif
>> -rw-r--r-- 1 shoofi shoofi 51338 sie 20 11:50 landcover.30m.tif
>>
>> $ gdal_translate -co "COMPRESS=DEFLATE" landcover.30m.tif 
>> landcover.30m_gt.tif
>> $ ls -l landcover.30m_gt.tif
>> -rw-r--r-- 1 shoofi shoofi 47567 sie 20 11:51 landcover.30m_gt.tif
>>
>>
>>
>> (Probably related to [1]. Some more info in a duplicate [2].)
>>
>> [1]http://trac.osgeo.org/gdal/ticket/1688
>> [2]http://trac.osgeo.org/gdal/ticket/1689).

> I wouldn't call 3-4KiB "significantly larger", especially as this
> appears to be a fixed overhead, rather than a proportional one.

It becomes really significant when compression is involved. Please read
in my original message and in
http://trac.osgeo.org/gdal/ticket/1688#comment:4.

> Have you compared the output from gdalinfo for the images in question?

Identical.

> If the extra is caused by the GRASS colour rules being added as
> metadata, we could add a flag to suppress that. OTOH, if it requires
> making the code significantly more complex, then it isn't likely to
> happen for the sake of a few KiB.

The metadata is not the culprit for sure.

-- 
Maciej Sieczka
www.sieczka.org