[Gdal-dev] ArcGrid to IMG conversion: huge file

[Frank Warmerdam]

Petteri Packalen wrote:
> Hi,
> 
> More clarification about this IMAGINE nodata issue. IMAGINE prefers the 
> term BACKGROUND. It isn't strictly "notada" as we understand the 
> concept. Often zero is used as background value but it cannot be defined 
> in IMG-file (at least I haven't found such a functionality in 10+ 
> years). Many dialogs has an option "Ignore Zero in Stats" which serves a 
> kind of surrogate to nodata functionality. Some import dialogs allows 
> user to select whether "nodata" is converted to zero or e.g. minimum 
> value of the current datatype.

Petteri,

That helps explain why I haven't run into it before.  Here I thought I
was just being stupid.

Peng Gao kindly sent me an example .img file which my .img dumper
shows as having this node:

     Eimg_NonInitializedValue(Eimg_NonInitializedValue) @ 1334574 + 21 @ 1334702
     + valueBD = 1x1 basedata of type 3

The 1x1 basedata is presumably the nodata value (0).

I will add support for this for nodata but I haven't noticed this before,
so I would suspect it is either relatively new, or perhaps still not
extensively used in Imagine.

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    | President OSGF, http://osgeo.org