[Gdal-dev] Kakadu float rasters and 16bits lossless

[Julien Demaria]

Frank,

sorry I've just seen in the source this comment (and thought the 
documentation was outdated...) :

  * Revision 1.20  2004/01/15 21:21:04  warmerda
  * added lossless compression of 16bit values
  *

but haven't verified that... (a little test with diff seams fails...)

Other question :
I searched on gdal web sites for a CVSWeb ; is it disabled ? (I've found 
only http://www.remotesensing.org/cgi-bin/cvsweb.cgi/osrs/gdal/ on 
http://gdal.maptools.org/download.html but it doesn't works...)

Regards,

Julien


At 11:12 16/07/2004 -0400, Frank Warmerdam wrote:
>Julien Demaria wrote:
>>Hi,
>>The Kakadu driver can create float rasters and compress 16bits rasters 
>>lossless, so this line in the driver sources should be updated :
>>         poDriver->SetMetadataItem( GDAL_DMD_CREATIONDATATYPES,
>>                                    "Byte Int16 UInt16" );
>>and also the driver documentation 
>>(http://gdal.maptools.org/frmt_jp2kak.html) :
>>"... When reading images this driver will represent the bands as being 
>>Byte (8bit unsigned), 16 bit signed or 16 bit unsigned.
>>...
>>NOTE: QUALITY=100 will not be lossless for 16bit images."
>
>Julien,
>
>Have you verified broadly that 16bit signed and unsigned images can be
>compressed losslessly?  I can't remember why I put this comment in the
>document, but I am hesitant to remove it without being able to remember.
>
>Also, the floating point support depends on the data being prescaled between
>0.0 and 1.0 which is then internally implicitly treated as integers as I
>understand it.  So I don't think there is really proper support for floating
>point data, though I didn't realize when I first implemented the code.
>
>Best regards,
>--
>---------------------------------------+--------------------------------------
>I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
>light and sound - activate the windows | http://pobox.com/~warmerdam
>and watch the world go round - Rush    | Geospatial Programmer for Rent