[gdal-dev] Faster gdalinfo from COG

[Even Rouault]

On mercredi 8 janvier 2020 12:27:56 CET Vincent Sarago wrote:
> Hi Jukka,
> The time you are seeing is related to your configuration and not
> specifically to the file itself.
> 
> If you set `GDAL_DISABLE_READDIR_ON_OPEN=EMPTY_DIR` in your env, you’ll see
> that gdalinfo will be much faster.

The file is also not entirely cloud optimized

$ GDAL_DISABLE_READDIR_ON_OPEN=EMPTY_DIR python swig/python/samples/
validate_cloud_optimized_geotiff.py  /vsicurl/http://latuviitta.kapsi.fi/data/
jarvi_dem/saimaa_dem.tif 
/vsicurl/http://latuviitta.kapsi.fi/data/jarvi_dem/saimaa_dem.tif is NOT a 
valid cloud optimized GeoTIFF.
The following errors were found:
 - The offset of the main IFD should be 192. It is 223880848 instead
 - The offset of the IFD for overview of index 0 is 586, whereas it should be 
greater than the one of the main image, which is at byte 223880848

How did you generate it ? What surprises me is that it contains the 'ghost' 
area typical of GDAL master COG driver, so the fact that the IFD header is not 
at the beginning of the file is unexpected.
Would you have edited the file (like adding statistics) after using 
gdal_translate -of COG ?

After reprocessing it with
gdal_translate saimaa_dem.tif out.tif -of COG -co COMPRESS=DEFLATE
I get a 'conformant' COG file

Even

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