If the problem persists try creating virtual rasters [.vrt], can speed loading times quite significantly: go to Raster - Miscellaneous - Build Virtual Raster (catalog)
Nigel -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andrea Peri Sent: 30 July 2015 15:01 To: Radim Blazek Cc: qgis-user Subject: Re: [Qgis-user] Slow to open huge rasters Hi Radim. thx for hint. You have right. And the trouble i spartially resolved. The lock initial of qgis was due to the create raster icons. Infact removing it. The layer is added without any trouble to the canvas. I say partally resolved because nw qgis is no more lockd when add the raster t the canvas. But is will start the think (without locking now) for show the raster. And I guess it could take many times again. Yes, the raster is on local harddisk. I enable the debug. A. 2015-07-30 13:54 GMT+02:00 Radim Blazek <[email protected]>: > On Thu, Jul 30, 2015 at 11:36 AM, Andrea Peri <[email protected]> wrote: >> Hi Radim, >> thx for hint. >> >> I try to set the contrast enhancement to NO STRETCH and Limits to >> minimum / maximum , Apparently seem to have no result. The qgis is >> locked in opening of raster, but of course I should wait for some >> hours to see if some improvements is occursed. > > You can try to uncheck Options > Canvas & Legend > Layer Legend > > Create raster icons but I don't think that it could help if zoom/pan > is fast, so it seems that there are overviews (pyramids). In fact, > even with cumulative cut it should not be slow if there are overviews > because default cut calculation is using estimated histogram (250000 > pixels). > > The file is on local hard disk? > > Do you see what is happening from debug output? > > If you save a project with the raster, the next load of the project is fast? > > Radim > > >> A. >> >> >> 2015-07-30 9:52 GMT+02:00 Radim Blazek <[email protected]>: >>> On Thu, Jul 30, 2015 at 9:19 AM, Andrea Peri <[email protected]> wrote: >>>> Hi, >>>> >>>> I have a GeoTiff raster of 24Gbyte, floating point (Float64) with >>>> 11 bands and fomat geotiff. >>>> >>>> When try to open it with qgis 2.8.1 I see it take a really uge time >>>> to open it (about 10 hours). >>>> Initially I guess that was a time due to the huge dimension, but >>>> after the qgis show it. >>>> I notice that it is reallyquickly to zoom and pan. >>>> I don't understand why this difference between the open time and zoom/pan >>>> time. >>>> >>>> My first suspect was that qgis want to calculate the statistics in first >>>> open. >>>> But after a check with gdalinfo I see the statistics are available >>>> also in original tiff. >>> >>> QGIS defaults are stretch to 2/98% cut, try to set in Options > >>> Rendering > Rasters Contrast enhancement: No stretch or Limits: >>> Minimum / maximum >>> >>> Radim >>> >>> >>>> So I dont know really why it take so more time to open it. >>>> >>>> I hope to find some setting to reduce the pen time for this kind of images. >>>> >>>> Thx, >>>> >>>> A. >>>> >>>> -- >>>> ----------------- >>>> Andrea Peri >>>> . . . . . . . . . >>>> qwerty àèìòù >>>> ----------------- >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> [email protected] >>>> http://lists.osgeo.org/mailman/listinfo/qgis-user >> >> >> >> -- >> ----------------- >> Andrea Peri >> . . . . . . . . . >> qwerty àèìòù >> ----------------- -- ----------------- Andrea Peri . . . . . . . . . qwerty àèìòù ----------------- _______________________________________________ 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
