[Geotiff] processing no data in GeoTIFF

[Frank Warmerdam]

maphew (matt wilkie) wrote:
> Hi Rainer,
> 
>>   I have to process a number of tiles and have to identify no data areas.
>> The TIFF images are 24BIT and the "no data" area is a black and a 
>> WHITE area
>> in a tile.
>>  
>>   I would like to identify all tiles (filenames), which have a cluster 
>> of at
>> least 4 pixels in one (white) or the other (black) color. 
> 
> maybe in two passes for each image? one pass assigning white and the 
> second assigning black as nodata?
> 
> another option might be to use gdalwarp but without re-projecting,  as 
> it can take multiple arguments for nodata (-srcnodata) 
> http://gdal.maptools.org/gdalwarp.html

Matt / Rainer,

Note that gdalwarp's -srcnodata can take one argument for each band.  It
cannot support multiple source nodata values for a given band.   I don't
have a "canned" solution for what Rainer wants to do, though the multi
pass approach might be sensible.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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