[gdal-dev] NITF 16bit pixel scaling using NBITS/ABPP

[Even Rouault]

Le mercredi 15 décembre 2010 12:52:06, Smart, Gary a écrit :
> We are reading NITF images which occupy the lower 12bits of a 16bit
> datatype.  These images clearly have ABPP=12 and NBPP=16 set in the
> header.  However, when I use GetMetadataItem("NBITS"), the string
> returned is always 'null'.  I have also tried GetMetadataItem("ABPP") -
> which also returns 'null'.
> 

You can guess the NBPP from the datatype of the band. If it's Int16 or UInt16, 
then NBPP = 16

The ABPP can be read through the "NITF_ABPP" metadata item (as seen in the 
output of gdalinfo on such a file)

> 
> 
> Does anyone know how to access this information in the NITF header.  Are
> there any recorded problems regarding this?
> 
> I am using GDAL version 1.7.1 on SLES10 linux.
> 
> 
> 
> Gary