[Qgis-user] Slow to open huge rasters

Thu Jul 30 07:14:25 PDT 2015

Hi Nicolas,

Following the hint of Radim I discovered that the troubles are two not ne.

Infact when i add the raster tothe qgis I see the qgis completelly locked .
The unique action possiblewas to kill it.

With helpof Radim I discovered that that lock was due to the option
Create a raster icon. An option that is enabled by default and that
want to create always a raster icon when I open this reaster.

After removed that option.
The qgis was no more locked.

Now start the second trouble.
Infact the qgis still need many time to read all the image.

Now, without the raster icon tolock the qgis, I can try somethink.
So I see that if I zoom to a detail and only after this I ligh-on the
raster , it is visible.
But again I have new problems infact now I need to open the properties
to change the bands levels for RGB.
And when try to open the properties wgis newly go lock.

Perrhaps the qgis in the properties windows of a raster try again to
calculate a raster icon ?

A.

2015-07-30 15:50 GMT+02:00 Nicolas Cadieux <nicolas.cadieux at archeotec.ca>:
> Hi,
>
> I have been opening rasters that are much bigger than that lately with no
> trouble at all. It does take some time but not hours. I have bigger file
> (80-300GB) but with one band only. I do use a SSD to help out but works with
> a usb3 drive also.
>
> The obvious is to check for to see if there is a problem with the hardware
> (memory, CPU, drive) and to make sure you are not opening the file from a
> file server (a virtual drive) but from a local hard drive (not a USB key) or
> a failing HD.
>
> Try zooming on the zone using a small polygons as a reference, before
> opening the raster.  Try disabling the "screen render" before opening the
> raster (right lower corner or Option\Rendering\Rendering behavior.
>
> An other potential problem is the way the tiff was created.  If, for example
> the file was created with gdal-Grid (interpolation), then by default, the
> file was created with an origin from the bottom-left and not upper-left.
>
> Try resaving the file in QGIS.  Try using the QGIS usual method of saving
> rasters and also try using gdal-warp with no parameters
> (raster/projections/warp) (that with change the file origin) then reopen the
> file.
>
> Nicolas Cadieux M.Sc.
> Les Entreprises Archéotec inc.
> 8548, rue Saint-Denis Montréal H2P 2H2
> Téléphone: 514.381.5112  Fax: 514.381.4995
> www.archeotec.ca
>
> On Jul 30, 2015 7:49 AM, "Radim Blazek-2 [via OSGeo.org] " <[hidden email]>
> wrote:
>
> On Thu, Jul 30, 2015 at 11:36 AM, Andrea Peri <<a
> href="/user/SendEmail.jtp?type=node&node=5217747&i=0">[hidden
> email]> 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 <<a
>> href="/user/SendEmail.jtp?type=node&node=5217747&i=1">[hidden
>> email]>:
>>> On Thu, Jul 30, 2015 at 9:19 AM, Andrea Peri <<a
>>> href="/user/SendEmail.jtp?type=node&node=5217747&i=2">[hidden
>>> email]> 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
>>>> -----------------
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>>
>>
>>
>> --
>> -----------------
>> Andrea Peri
>> . . . . . . . . .
>> qwerty àèìòù
>> -----------------
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-- 
-----------------
Andrea Peri
. . . . . . . . .
qwerty àèìòù
-----------------