[Qgis-user] Cumulative count cut on rasters

[Andrea Peri]

Hi Radim, thx for explain.
Your explanation of extimated strategy could explain why the extimated
is more precise rather than the actual strategy.
I guess are the null values to produce a wrong "actual" results.

Can you say me in which file I can found the code for the extimate and
actual strategy
to verify my hypotesis.?

Thx.



2015-08-12 11:22 GMT+02:00 Radim Blazek <radim.blazek at gmail.com>:
> On Tue, Aug 11, 2015 at 3:09 PM, Andrea Peri <aperi2007 at gmail.com> wrote:
>> Hi,
>> trying the rendering of a raster floating point using the cumulative count cut.
>> I see it is quite good if I set the values 2.0,100.0% (not 98%) and
>> use the accuracy at value "estimate".
>> Instead always with the same values for cumulative count cut, but
>> using the accuracy "actual".
>> The result is really poor. The image became totally black with only
>> few isles of grey.
>>
>> This is a surprise for me because the accuracy "actual" take a long
>> time and the name seem to say more precision.
>>
>> I like to know what is the strategy used for actual: estimate and the
>> strategy for accuracy: actual.
>
> Actual takes all pixels, estimate takes 250000 pixels (whole data
> extent with resolution giving approximately 250000 pixels). Some
> providers may use different approach to get estimated values, e.g.
> GDAL provider may use approximated values returned by GDAL, IIRC.
>
> Radim
>
>
>>
>> Many thx.
>>
>> --
>> -----------------
>> Andrea Peri
>> . . . . . . . . .
>> qwerty àèìòù
>> -----------------
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user



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