Hi Etienne, On Aug 23, 2012, at 5:57 PM, Etienne Tourigny <[email protected]> wrote: > On the other hand, wouldn't a simple "gdalinfo -stats file.vrt" > achieve the same as the linked python script, but easier to run? the python script calculates approximated stats, so it works like gdalinfo -approx_stats file.vrt
The problem was the -approx_stats option is not present in the documentation (either help online or using --help), then I wrote that few-lines script to achieve the task. Only now I'm looking at the gdalinfo.c code on the repo I know it's there since Jan 2007 (r10658)... BTW a ticket is needed to update the doc. On Thu, Aug 23, 2012 at 7:39 PM, Etienne Tourigny <[email protected]> wrote: > it would be nice if someone (ideally the author) could test > the same with nightly master (1.9). +1, but I hope you're talking about the wiki page author :) I cannot do any test because I have no VRT files so big. Micha, could you try with QGis master and report here, please? Regards. > > Etienne > > On Thu, Aug 23, 2012 at 2:27 PM, Radim Blazek <[email protected]> wrote: >> On Thu, Aug 23, 2012 at 5:57 PM, Etienne Tourigny >> <[email protected]> wrote: >>> On Thu, Aug 23, 2012 at 11:00 AM, Even Rouault >>> <[email protected]> wrote: >>>>> It would be nice to have this bultin to gdalbuildvrt (as an optin of >>>>> course) - could the authors make a patch? >>>> >>>> For a *byte* data type, which must be the common case, why wouldn't QGIS >>>> just >>>> use min=0 and max=255 when statistics are not computed ? >>> >>> good question. >>> >>> Unless I am mistaken, min/max are set to 0/255 by default, unless >>> QgsRasterDataProvider::bandStatistics() or >>> QgsRasterLayer::bandStatistics() is called - which is probably what >>> happens. >> >> Default contrast enhancement in current master (may be changed in >> Options > Rendering > Rasters): >> Single band gray: Stretch to min / max >> Multiband color (byte/band): No stretch >> Multiband color (>byte/band): Stretch to min / max >> Limits (min/max): Cumulative count cut. >> >> The min/max are calculated using 250000 pixels sample, which should be >> fast. It would be useful to test the VRT without stats collected with >> current master. >> >> It would be possible to add another default contrast enhancement for >> Single band gray byte, but I believe that if the whole raster can be >> rendered in reasonable time, the min/max calculation must be also fast >> and contrast enhancement may be important even with byte data. >> >> Radim >> >>> I don't understand what is the problem, does the VRT load slowly >>> initially, or is getting statistics rather slow? >>> >>> On the other hand, wouldn't a simple "gdalinfo -stats file.vrt" >>> achieve the same as the linked python script, but easier to run? >>> >>> Etienne >>> >>>> >>>>> >>>>> Regards, >>>>> Etienne >>>>> >>>>> On Thu, Aug 23, 2012 at 7:34 AM, Micha Silver <[email protected]> wrote: >>>>> > On 23/08/2012 11:33, Giovanni Manghi wrote: >>>>> >> >>>>> >> http://trac.osgeo.org/gdal/wiki/CatalogueForQIS >>>>> > >>>>> > >>>>> > Magic! Many thanks, and also to Andrea Peri for posting the python code. >>>>> > In windows I had to run it as: " python computestats.py -approx >>>>> > <filename.vrt> " >>>>> >> >>>>> >> it would be very nice to have this added as tool directly in QGIS... >>>>> >> >>>>> >> cheers >>>>> >> >>>>> >> >>>>> >> -- Giovanni -- >>>>> >> >>>>> >> >>>>> >> On Thu, 2012-08-23 at 11:27 +0300, Micha Silver wrote: >>>>> >>> >>>>> >>> Hello all: >>>>> >>> >>>>> >>> I have a batch of over 100 raster tiles in ecw format. Each is 50 - >>>>> >>> 100 MB in size. When I choose 20 or so files to load they appear >>>>> >>> (render) very quickly - in a matter of a few seconds or less. If I >>>>> >>> create a vrt of that same batch of tiles, it takes a long time to >>>>> >>> first render - upwards of 15 - 30 seconds. Once the vrt is loaded >>>>> >>> response is excellent (zooming, etc). But that initial delay is a bit >>>>> >>> annoying. Anything I can do to improve it? (QGIS 1.8, Win 7 64 bit) >>>>> >>> >>>>> >>> Many thanks, >>>>> >>> Micha >>>>> >>> >>>>> >>> -- >>>>> >>> Micha Silver >>>>> >>> 052-3665918 >>>>> >>> _______________________________________________ >>>>> >>> Qgis-user mailing list >>>>> >>> [email protected] >>>>> >>> http://lists.osgeo.org/mailman/listinfo/qgis-user >>>>> >> >>>>> >> >>>>> >> >>>>> >> This mail was received via Mail-SeCure System. >>>>> >> >>>>> >> >>>>> > >>>>> > >>>>> > -- >>>>> > Micha Silver >>>>> > 052-3665918 >>>>> > >>>>> > _______________________________________________ >>>>> > Qgis-user mailing list >>>>> > [email protected] >>>>> > http://lists.osgeo.org/mailman/listinfo/qgis-user >>>>> _______________________________________________ >>>>> Qgis-user mailing list >>>>> [email protected] >>>>> http://lists.osgeo.org/mailman/listinfo/qgis-user >>>>> >>>> >>>> >>> _______________________________________________ >>> Qgis-user mailing list >>> [email protected] >>> http://lists.osgeo.org/mailman/listinfo/qgis-user > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user -- Giuseppe Sucameli - Faunalia _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
