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

[Benoit de Cabissole]

 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?

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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