[gdal-dev] python-gdal ComputStatistics return just two values

[Ivan Lucena]

D'accord.

Even Rouault wrote:
> Le Friday 27 March 2009 20:05:11 Lucena, Ivan, vous avez écrit :
>> Even,
>>
>> I see. You are right. With the absence of ComputeRasterStatistics() I got
>> confused and I made the wrong
>>
>> assumption. BTW, why there is no wrapper for ComputeRasterStatistics()? That 
> would work then:
>>>>> bd1.SetStatistics(bd2.ComputeRasterStatistics())
> 
> Because you don't use the latest and greatest GDAL ;-)
> 
> Extract from swig/include/Band.i from SVN head:
> 
>   /* Interface method added for GDAL 1.7.0 */
> %apply (double *OUTPUT){double *min, double *max, double *mean, double 
> *stddev};
> %apply (IF_ERROR_RETURN_NONE) { (CPLErr) }; 
>   CPLErr ComputeStatistics( bool approx_ok, double *min = NULL, double *max = 
> NULL, double *mean = NULL, double *stddev = NULL,                          
> GDALProgressFunc callback = NULL, void* callback_data=NULL){
>     return GDALComputeRasterStatistics( self, approx_ok, min, max, mean, 
> stddev, callback, callback_data );
>   }
> %clear (CPLErr);
> 
> 
>> Not a big deal. The work around is easy.
>>
>> Thank you very much,
>>
>> Ivan
>>
>>>  -------Original Message-------
>>>  From: Even Rouault <even.rouault at mines-paris.org>
>>>  Subject: Re: [gdal-dev] python-gdal ComputStatistics return just two
>>> values Sent: Mar 27 '09 18:45
>>>
>>>  Hi Ivan,
>>>
>>>  I don't think there's a bug.
>>>
>>>  The C API for ComputeBandStats is :
>>>
>>>  CPLErr CPL_DLL CPL_STDCALL
>>>  GDALComputeBandStats( GDALRasterBandH hBand, int nSampleStep,
>>>                               double *pdfMean, double *pdfStdDev,
>>>                               GDALProgressFunc pfnProgress,
>>>                               void *pProgressData );
>>>
>>>  So, the python API is consistant with it.
>>>
>>>  So it is expected that "bd1.SetStatistics(bd2.ComputeBandStats())" will
>>> fail as it is provided with 2 values instead of the expected 4.
>>>
>>>  Best regards,
>>>  Even
>>>
>>>  Le Friday 27 March 2009 19:02:14 Lucena, Ivan, vous avez écrit :
>>>  > Hi there,
>>>  >
>>>  > I believe that ComputeBandStats() should return 4 values min, max,
>>>  > mean and stddev) [1] but the Python API is returning just mean and
>>>  > stddev.
>>>  >
>>>  > python:
>>>  > >>> bd.ComputeBandStats()
>>>  >
>>>  > (9.0071713001936118, 11.350094331448236)
>>>  >
>>>  > >>> bd.ComputeRasterMinMax()
>>>  >
>>>  > (-1.7899999618530273, 31.149999618530273)
>>>  >
>>>  > gdalinfo:
>>>  >
>>>  > Band 1 Block=360x1 Type=Float32, ColorInterp=Gray
>>>  >   Min=-1.790 Max=31.150
>>>  >   Minimum=-1.790, Maximum=31.150, Mean=9.007, StdDev=11.350
>>>  >   Unit Type: unspecified
>>>  >   Metadata:
>>>  >     STATISTICS_MINIMUM=-1.789999961853
>>>  >     STATISTICS_MAXIMUM=31.14999961853
>>>  >     STATISTICS_MEAN=9.0071713001936
>>>  >     STATISTICS_STDDEV=11.350094331448
>>>  >
>>>  > Is that a bug?
>>>  >
>>>  > See what happens in that case:
>>>  > >>> bd1.SetStatistics(bd2.ComputeBandStats())
>>>  >
>>>  > Traceback (most recent call last):
>>>  >   File "<interactive input>", line 1, in <module>
>>>  >   File "E:\Python25\Lib\site-packages\osgeo\gdal.py", line 729, in
>>>  > SetStatistics return _gdal.Band_SetStatistics(*args)
>>>  > TypeError: Band_SetStatistics() takes exactly 5 arguments (2 given)
>>>  >
>>>  > My best regards,
>>>  >
>>>  > Ivan
>>>  >
>>>  > [1] http://www.gdal.org/gdal_8h.html#a93b6b6ea6e71017ce25524e1a9ef1e3
>>>  >
>>>  > _______________________________________________
>>>  > gdal-dev mailing list
>>>  > gdal-dev at lists.osgeo.org
>>>  > http://lists.osgeo.org/mailman/listinfo/gdal-dev
> 
> 
> 
>