[gdal-dev] GDAL Byte Swapping?

[Even Rouault]

Le jeudi 14 juin 2012 21:26:09, Trist, Brenda R. a écrit :
> I am new to GDAL.  I recently downloaded GDAL have successfully built
> 
> and linked to the source.  The program I am writing reads in a
> 
> GeoTiff DEM (32bit format) and writes the dem data portion out to a
> 
> ntif file (using NITRO NITF routines from sourceforge).
> 
> I then ran the command od -c on the tif file I am reading and on the
> 
> ntif I just created to compare the DEM data area.  I noticed that
> 
> while the data is there that the bytes appear to have been swapped.
> 
> I am assuming that I don't want it to do that.  I was wondering if
> 
> anyone has encountered this same thing and if there is something that
> 
> I should be doing differently?  I researched the bug list and all
> 
> mentions of byteswapping pretty much have been closed due to being
> 
> fixed.  So I am assuming that I must be doing something wrong at my end.

On little endian (Intel like) architectures, TIFF files with multi-byte data 
types are (generally) written in little endian ordering (if the first 2 bytes 
of the TIFF files are "II", then it's little endian. If it's "MM", then it's 
big endian). Whereas in NITF, it is always big endian. So what you are seeing 
is likely expected.

You could compare that the 2 files contain the same data values (taking into 
account the byte swapping if needed) by checking the checksum value reported 
"gdalinfo -checksum thefile" 

Any reason not to use the GDAL NITF driver by the way ?