[gdal-dev] Does gdal_calc.py not calculate arithmetic with in the same file?

[Cleo Drakos]

Even if I converted the input file into Float 32 at first, the resulted
image is still totally black.

cleo


On Tue, Jul 29, 2014 at 11:20 PM, Vincent Schut <schut at sarvision.nl> wrote:

>  On 07/29/2014 04:04 PM, Cleo Drakos wrote:
>
> Thanks for your response.
> I tried the followings:
>
>  gcalc = 'C:\\Users\\cleo\\Documents\\gdalpys\\gdal_calc.py'
> ##I produced second file (b)as the copy of first(a)
>  a = 'D:\\a.tif'
> b = 'D:\\b.tif'
> outfile = 'D:\\result.tif'
> expr = '(A-B)/(A+B)'
>
> subprocess.call([sys.executable,gcalc,'-A',a,'--A_band','1','-B',b,'--B_band','0','--outfile',outfile,\
>     '--calc',expr,'--type','Float32','--format','ENVI'],shell=True)
> a,b,outfile = None, None,None
>
>  Unfortunately, resulted file is completely black.
>
>  I hope someone can help me.
>
>
> I don't use gdal_calc myself, but I suppose the problem is the byte
> datatype. I would try to convert the input data to float32 first (use
> gdal_translate -ot Float32) and try again.
>
> Best,
> Vincent.
>
>
>
>
> On Tue, Jul 29, 2014 at 10:37 PM, Etienne Tourigny <
> etourigny.dev at gmail.com> wrote:
>
>> I am not sure, but you can do the following to make sure:
>>
>>  cp infile infile2
>>  gdal_calc.py -A infile --A_band 1 -B infile2 --B_band 0 --outfile
>> outfile --calc "(A-B)/(A+B)"
>>
>>  Also, perhaps the extra comma in your command might be to blame "-B
>> infile,"
>>
>>  Etienne
>>
>>
>>  On Tue, Jul 29, 2014 at 3:46 AM, Cleo Drakos <cleo21drakos at gmail.com>
>> wrote:
>>
>>>  Hi GDAL Developers,
>>>
>>> I have one GeoTIFF file with 2 bands. The data type is Byte. I want to
>>> calculate (Band2-Band1)/(Band2+Band1).
>>>
>>> But the following command provided a dark image:
>>>
>>> gdal_calc.py -A infile --A_band 1 -B infile, --B_band 0 --outfile
>>> outfile --calc "(A-B)/(A+B)"
>>>
>>> Does gdal_calc.py not calculate arithmetic with in the same file?
>>>
>>> Thanks for your time.
>>>
>>> cleo
>>>
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>>> gdal-dev mailing list
>>> gdal-dev at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>
>>
>
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