<div dir="ltr">Even if I converted the input file into Float 32 at first, the resulted image is still totally black.</div><div class="gmail_extra"><br clear="all"><div><div dir="ltr">cleo</div></div>
<br><br><div class="gmail_quote">On Tue, Jul 29, 2014 at 11:20 PM, Vincent Schut <span dir="ltr"><<a href="mailto:schut@sarvision.nl" target="_blank">schut@sarvision.nl</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"><div class="">
On 07/29/2014 04:04 PM, Cleo Drakos wrote:<br>
<blockquote type="cite">
<div dir="ltr">Thanks for your response.
<div>I tried the followings:</div>
<div><br>
</div>
<div>
<div>gcalc =
'C:\\Users\\cleo\\Documents\\gdalpys\\gdal_calc.py'</div>
<div>##I produced second file (b)as the copy of first(a)<br>
</div>
<div>a = 'D:\\a.tif'</div>
<div>b = 'D:\\b.tif'</div>
<div>outfile = 'D:\\result.tif'</div>
<div>expr = '(A-B)/(A+B)'</div>
<div>subprocess.call([sys.executable,gcalc,'-A',a,'--A_band','1','-B',b,'--B_band','0','--outfile',outfile,\</div>
<div>
'--calc',expr,'--type','Float32','--format','ENVI'],shell=True)
</div>
<div>a,b,outfile = None, None,None</div>
</div>
<div><br>
</div>
<div>Unfortunately, resulted file is completely black.</div>
<div><br>
</div>
<div>I hope someone can help me.</div>
</div>
</blockquote>
<br></div>
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.<br>
<br>
Best,<br>
Vincent.<div class=""><br>
<br>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Tue, Jul 29, 2014 at 10:37 PM,
Etienne Tourigny <span dir="ltr"><<a href="mailto:etourigny.dev@gmail.com" target="_blank">etourigny.dev@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">I am not sure, but you can do the following
to make sure:
<div><br>
</div>
<div>cp infile infile2</div>
<div>
<span style="font-family:arial,sans-serif;font-size:13px">gdal_calc.py
-A infile --A_band 1 -B infile2 --B_band 0 --outfile
outfile --calc "(A-B)/(A+B)" </span><br>
</div>
<div><span style="font-family:arial,sans-serif;font-size:13px"><br>
</span></div>
<div><span style="font-family:arial,sans-serif;font-size:13px">Also,
perhaps the extra comma in your command might be to
blame "</span><font face="arial, sans-serif">-B
infile,"</font></div>
<div><font face="arial, sans-serif"><br>
</font></div>
<div><font face="arial, sans-serif">Etienne</font></div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">
<div>
<div>On Tue, Jul 29, 2014 at 3:46 AM,
Cleo Drakos <span dir="ltr"><<a href="mailto:cleo21drakos@gmail.com" target="_blank">cleo21drakos@gmail.com</a>></span>
wrote:<br>
</div>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div>
<div dir="ltr">Hi GDAL Developers,<br>
<br>
I have one GeoTIFF file with 2 bands. The data
type is Byte. I want to calculate
(Band2-Band1)/(Band2+Band1).<br>
<br>
But the following command provided a dark
image:<br>
<br>
gdal_calc.py -A infile --A_band 1 -B infile,
--B_band 0 --outfile outfile --calc
"(A-B)/(A+B)" <br>
<br>
Does gdal_calc.py not calculate arithmetic
with in the same file?<br>
<br>
Thanks for your time.<span><font color="#888888"><br>
<br>
cleo<br>
</font></span></div>
<br>
</div>
</div>
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