[gdal-dev] The documentation should be corrected, I think.

[Even Rouault]

Le mercredi 30 juillet 2014 05:54:48, Cleo Drakos a écrit :
> Dear all:
> 
> The problem I was facing has been solved. I detected that the problem was
> with the band number '0'. Solution is: the band number starts from '1'.
> 
> But, the gdal documentation says that the default band number is '0'.
> http://www.gdal.org/gdal_calc.html
> 
> The documentation should be corrected, I think.

Fixed. Thanks

> 
> The default band number is '1'.
> 
> Thanks.
> 
> cleo
> 
> 
> On Wed, Jul 30, 2014 at 11:15 AM, Jeremy Palmer <JPalmer at linz.govt.nz>
> 
> wrote:
> >  Hi Cleo,
> > 
> > Just been dealing with this type of issue.
> > 
> > 
> > 
> > It’s likely that the byte datatype is overflowing.
> > 
> > 
> > 
> > Try something like:
> > 
> > 
> > 
> > --calc "(A.astype(int)-B.astype(int))/(A.astype(int)+B.astype(int))"
> > 
> > 
> > 
> > Actually you might only need to cast one of the bands from byte to int,
> > so the syntax could be:
> > 
> > 
> > 
> > --calc "(A.astype(int)-B A.astype(int)+B)"
> > 
> > 
> > 
> > Cheers
> > Jeremy
> > 
> > 
> > 
> > *From:* gdal-dev-bounces at lists.osgeo.org [mailto:
> > gdal-dev-bounces at lists.osgeo.org] *On Behalf Of *Cleo Drakos
> > *Sent:* Wednesday, 30 July 2014 2:06 p.m.
> > *To:* Vincent Schut
> > *Cc:* gdal-dev
> > *Subject:* Re: [gdal-dev] Does gdal_calc.py not calculate arithmetic with
> > in the same file?
> > 
> > 
> > 
> > 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_b
> > and','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 at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/gdal-dev
> > 
> > 
> > 
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> > 
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> > 
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> > 
> > 
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