[gdal-dev] Re: Problem with nodata values

[Frank Warmerdam]

Hermann Peifer wrote:
> Frank Warmerdam wrote:
>>
>> I believe you want to pass the warp option INIT_DEST=-9999 to set all 
>> pixels that do not come from the source file to -9999.
>>
>> This is done with the -wo flag to gdalwarp.
>>
>> eg.
>>
>> gdalwarp -wo INIT_DEST=-9999 ...
>>
> 
> Frank,
> is the above warp option different to dstnodata -9999  ?

Hermann,

It appears they are distinct items.  The INIT_DEST essentially sets
the output file completely to the indicated value when it is created
while the dstnodata switch determines whether the warper considers an
existing pixel to be set in the output file yet or not when attempting
to do alpha blending and such.

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