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

[Cleo Drakos]

Hello Jeremy

Thanks for your response.

I am still getting the completely black image.

The input image I am working with is here:

http://commondatastorage.googleapis.com/earthenginepartners-hansen/GFC2013/Hansen_GFC2013_last_00N_000E.tif




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_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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