[Gdal-dev] GDAL vs ArcGIS raster calculator

[joosthoek]

Hi Frank,

Thanks for your reply, I'll try it out using python. Yeay, nodata worked
using gdal_translate -nodata 0. One other question, is it also possible to
use not python but .NET?

Cheers,

Jelmer


Frank Warmerdam-2 wrote:
> 
> Jelmer,
> 
> The calculation appears to be correcting for 16 bit signed integer data
> that was incorrectly treated as unsigned.  It also marks post-adjusted
> values of -32768 as nodata.
> 
> You should be able to do something similar with a numpy python script like
> the following (which works with FWTools):
> 
> #!/usr/bin/env python
> 
> import gdal
> import gdalnumeric
> 
> x = gdalnumeric.LoadFile('utm.tif')
> 
> x_adjusted = gdalnumeric.choose( \
>      gdalnumeric.greater( x, 32767 ),  (x, x-65536) )
> 
> x_adjusted = x_adjusted.astype(gdalnumeric.Int16)
> 
> prototype_ds = gdal.Open( 'utm.tif' )
> gdalnumeric.SaveArray( x_adjusted, 'utm2.tif', prototype = prototype_ds )
> 
> 
> Note, this script does not set the nodata value.  That could be done as
> an additional step with gdal_translate, or is left as an exercise for the
> reader. :-)
> 

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