[Qgis-user] Slow to open huge rasters

[Andrea Peri]

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 <radim.blazek at gmail.com>:
> On Thu, Jul 30, 2015 at 11:36 AM, Andrea Peri <aperi2007 at gmail.com> 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 <radim.blazek at gmail.com>:
>>> On Thu, Jul 30, 2015 at 9:19 AM, Andrea Peri <aperi2007 at gmail.com> 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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>>>> Qgis-user mailing list
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>>
>>
>>
>> --
>> -----------------
>> Andrea Peri
>> . . . . . . . . .
>> qwerty àèìòù
>> -----------------



-- 
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Andrea Peri
. . . . . . . . .
qwerty àèìòù
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