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

[Tim Sutton]

Hi


On Sun, Oct 31, 2010 at 10:54 AM, Benoit de Cabissole
<benoit at exigesa.com> wrote:
>  Hi Tim,
>
> Many thanks for fixing the problems [14381, 14387 & 14425]!
>
> But there is now another one popping up:
>
> When the data values in an one-band raster are real numbers and are
> negative/positive or are greater than 255 (?) the histogram curve does
> not display. The x- and y-axis correctly show the range of values but no
> curve is displayed. Furthermore, if data values are positive and
> negative, the histogram curve stops at 0: no curve over the negative values.
>
>
> It also looks like the number of bins is too small when the data range
> is small. I've got a raster with "real number" values between 0 and 5.
> The number of bins on that raster is only 6. This is far too coarse to
> be of any use.
>
> Do I open a ticket for those problems?


Do you have a small sample dataset I can use to replicate the issue?

Regards

Tim

>
> Cheers,
> Benoit
>
>
>
>
> On 18/10/2010 09:29, Benoit de Cabissole wrote:
>>  Hi Tim,
>>
>> Just after upgrading to release 14390 the histogram function works like
>> a charm when I open *for the first time* the raster properties window.
>> Thank you!
>>
>> But, if I close the raster property window while in the histogram tab
>> and try to re-open it, QGIS crashes!
>> In fact I cannot open any raster properties window after that without
>> having QGIS crash...
>> I've edited the 'row' value in the RasterLayerProperties in the registry
>> to set it to 1 (from 6) and I can again use QGIS normally.
>> So it seems that the raster properties window bombs out QGIS if it opens
>> in the histogram tab (row=6).
>>
>> Can you reproduce this behaviour in Linux/Mac/Other win?
>>
>> I'm on WindowsXP in OSGeo4W.
>>
>> One comment: the stats are computed each time the histogram tab is
>> opened. For large raster it takes a long time to compute the histogram.
>> Would it be best to save the histogram somewhere and reuse it?
>>
>> Cheers,
>> Benoit
>>
>>
>>
>> On 17/10/2010 09:23, Tim Sutton wrote:
>>> Hi
>>>
>>> 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?
>>>>
>>> This should be fixed now as of r14387.
>>>
>>> Regards
>>>
>>> Tim
>>>
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>>
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Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
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