[Qgis-developer] Problems with Histogram tab in Raster properties

[Benoit EXIGE]

Hi Tim,

Many thanks for looking at that.

Regarding the NaN I will have to check because I think one of the  
raster I've used (geotiff) had its NaN set to 0 and the histogram was  
showing a spike at 0. But it could also be due to the Z-axis not  
showing real values!

Cheers,
Benoit




On 16 Oct 2010, at 0:31, Tim Sutton <lists at linfiniti.com> wrote:

> Hi Benoit
>
> On Thu, Oct 14, 2010 at 9:51 AM, Benoit de Cabissole <benoit at exigesa.com 
> > wrote:
>>  Hi,
>>
>> A) In release 14370 the histogram tab of the raster properties window
>> has a problem:
>> The histogram is not displayed the second time the 'histogram tab' is
>> clicked.
>> E.g.:
>> 1 - open the raster properties window
>> 2 - click on the histogram tab
>> 3 - histogram is computed and displayed
>> 4 - click on any other tab
>> 5 - click on the histogram tab again
>> 6 - blank screen!!
>>
>> On WinXP - OSGeo4W dev installation
>> Can someone replicate the problem?
>
> Ok I could replicate that. Will fix.
>
>>
>>
>>
>> B) And keeping with the histogram, three comments/suggestions:
>> - Could the NaN be excluded from the histogram?
>
> According to the fine folks on #gdal (EvenR): "the pixels whose value
> is nodata are excluded from the stats" - note that this is only the
> nodata value considered by gdal - which isnt aware of any additional
> nodata values you may have specified in the transparency tab.
>
>> - Could the X-axis numbers reflect the actual colour values instead  
>> of a
>> fixed 0-300 range?
>
> Yes I am going to do this.
>
>>   Note that the X-axis of the histogram is spread on colours values,
>> thus the displayed X-axis numbers are meaningless
>
> Right above should fix that.
>
>> - Could it be possible to add a zoom function on the histogram?
>>
>
> I believe so - I will have a play and see how easy that will be.
>
> Thanks for the feedback!
>
> Regards
>
> Tim
>
>
>
>>
>> Best regards,
>> Benoit
>>
>>
>>
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>>
>
>
>
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> Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
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