Hello Even, Le mercredi 31 août 2011 14:38:53, Even Rouault a écrit : > Selon Yves Jacolin <[email protected]>: > > List, > > > > I successfully assigned my projection information but still have some > > difference in the file size. This is not so important but I wanted to > > understand > > the reason. Idea welcome :) > > Yves, > > You have a difference between the input file and the output file produced > with gdal_translate (not gdalwarp) with identical compression method and > NBITS value, right ? [..]
hum my apologies, I mixed my files from gdalwarp and gdal_translate or there is an improvement for gdal_transalte from GDAL 1.6.0 (my desktop) to GDAL 1.8.0 (on my server). > > Another question: I have 2 000 ECW files (40 Mo each), 49 ECW files (1 Go > > each) > > and 2 ECW files (2 Go each). I worked first on 2 Go ECW file, it takes > > around 1 > > day to assign the projection information in the files. > > > > Do you think this is normal? How can I improve this? > > It sounds particularly slow indeed, even if it isn't totally unexexpected, > gdal_translate being a format agnostic tool, and when doing ECW -> ECW > transformation, it will decompress and recompress the data, which is not > ideal from a speed point of view and, in the case of lossy compression > methods, from the data integrity point of view. But a day for 2 ECW files > is admitedly slow. You might hit that ticket about ECW -> ECW slowness : > http://trac.osgeo.org/gdal/ticket/3454 . It contains a possible workaround > (altough you will find it quite ironic if you keep in memory what has been > said previously in this thread about gdalwarp being slower than > gdal_translate ;-)). Another solution if you only want to correct the > projection information is to use the "ECW Header Editor". I have never > used that tool myself, but a search in your favorite engine should bring > some results. However it might not be appropriate for batch processing. Interesting, I will test with gdalwarp soon. I don't know if it could be a problem but I am using VRT format. I saw in one of your comment in GeoRezo forum that it could be faster thant a direct ECW to ECW conversion. Am I right? I also find this script http://jrepetto.free.fr/ecwhed/ which seems usefull, but I have not test it yet. "ECW Header Editor" doesn't work on Linux or in batch mode :/ Thanks, Y. -- Yves Jacolin http://yjacolin.gloobe.org _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
