[FWTools] dstnodata and cubic convolution

Wim Chalmet wim.chalmet at terraengine.com
Fri Feb 2 15:53:30 EST 2007

I am working with panchromatic satellite imagery, which has the typical
"black borders" around the image area.
When using gdalwarp to reproject the imagery, I specifiy scrnodata and
dstnodata as 0, in order to make 0 look "transparent" in my image viewer.
This works fine. I also make sure that within my image area, no black pixels
occur, for visual purposes (i.e. each pixel within the image area has a
digital number of at least 1).
The problem that I am encountering is that cubic convolution allows pixel
values - within the imagery area - to become black (digital number 0),
because of the formula of cubic convolution.
This gives me problems, because when I then make 0 look transparent, it
appears as if I have holes in my image area.
Would it make sense to not allow gdalwarp to change the pixel value from
something larger than 0 to 0, if the user specifies dstnodata as 0? Is this
currently possible with gdalwarp?
Thanks for your help!
Yours truly,
Wim Chalmet

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