[gdal-dev] gdaladdo, overviews and NODATA
armin.burger at gmx.net
Tue Feb 21 15:36:19 EST 2012
I have a question regarding the gdaladdo tool and NODATA pixels:
When using resampling like "average" it seems that along the border of
DATA and NODATA pixels there happens an averaging also of some of the
original NODATA pixels (looks like 1-2 pixel width). This way in the
overviews they get values higher than 0 (0 is defined as NODATA). Using
this type of data in mapserver leads to small black borders when the
overviews are taken since the tag
OFFSITE 0 0 0
does not work anymore for the small border of now only "nearly-black"
I tried to set the metadata NODATA of the images to 0 for each band but
it had no effect. Only when I use resampling "nearest" then every NODATA
pixel of the overviews retains the full black 0 0 0.
Is there a way to force to exclude NODATA pixels during the "average"
resampling so that they retain their NODATA values?
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