[gdal-dev] Cropping a raster by a polygon - only nodata outside polygon wanted

[mathieu]

Hello,

I crop a 3 band raster by a polygon with the following formula :
/gdalwarp -of GTiff -cutline polygon.shp -cl polygon input.tif output.tif
/
But pixels outside my polygon are assigned the 0 value. I'd like them to
have nodata

If I put the -dstnodata 0 option :
/gdalwarp -of GTiff -cutline polygon.shp -cl polygon input.tif output.tif
-dstnodata 0/, all the pixels in each of the 3 bands that contain the 0
value will be turned to nodata, even if they are contained in my polygon.

Hence, 127 0 222 will become 127 nodata 222
or 0 127 222 will become nodata 127 222

How to put the nodata value only outside my polygon ?

Thanks a lot in advance !

Mathieu



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