[gdal-dev] slow raster (large GDALRasterAttributeTable?)

[Bart van den Eijnden (OSGIS)]

Hi Frank,

I can (I'll send it to you off-list on Thursday), but the problem 
appears to be different. I overlooked the fact that the classification 
is being done in Mapserver (about 30 classes), but even with 
scalebuckets set I can't get it to speed up.

Best regards,
Bart

Frank Warmerdam wrote:
> bartvde at osgis.nl wrote:
>> Hi list,
>>
>> I've got a tiff file of 28 Mb and it is really slow, so I am assuming 
>> the
>> classification gets applied on the fly or something like that.
>>
>> If I do a gdalinfo I get a huge list of STATISTICS_HISTOBINVALUES
>>
>>   Metadata:
>>     STATISTICS_MINIMUM=-5838
>>     STATISTICS_MAXIMUM=4225
>>     STATISTICS_MEAN=-1010.4585191036
>>     STATISTICS_MEDIAN=-212
>>     STATISTICS_MODE=1
>>     STATISTICS_STDDEV=1833.0113850333
>>     LAYER_TYPE=athematic
>>     
>> STATISTICS_HISTOBINVALUES=1|1|1|1|1|1|1|1|1|1|1|2|1|2|1|1|1|2|1|1|1|1....... 
>>
>>
>> Also, the GDALRasterAttributeTable has 9150 rows. Don't know if this is
>> related.
>>
>> Any ideas on how to speed this up? I tried to write it out to a new
>> GeoTiff or MrSID file, but somehow all this info is preserved, and the
>> slowness continues.
>
> Bart,
>
> Could you provide the dataset?  I'd be interested in reviewing the
> performance of the raster attribute table logic with an eye towards
> optimizing it.
>
> Best regards,


-- 
Bart van den Eijnden
OSGIS, Open Source GIS
bartvde at osgis.nl
http://www.osgis.nl