Paolo, This works for me as expected with the following input raster (and using your palette):
$ cat wrk/in.asc ncols 2 nrows 2 xllcorner 440720.000000000000 yllcorner 3750120.000000000000 cellsize 60.000000000000 NODATA_value 0 107 123 0 100 $ gdaldem color-relief -alpha wrk/in.asc wrk/palette.txt wrk/out.tif $ gdal_translate wrk/out.tif /vsistdout/ -of aaigrid -b 4 ncols 2 nrows 2 xllcorner 440720.000000000000 yllcorner 3750120.000000000000 cellsize 60.000000000000 255 255 0 255 Perhaps there's an issue with the nodata value of your raster ? Even > Hi all, > sorry if this is not the right list. Please redirect me elsewhere in case. > I cannot give a transparency to NULL when creating a coloured raster: > > gdaldem color-relief -alpha temp_clip.tif byr.txt temp_col.tif -of GTiff > > where byr.txt is: > > 0% 5 113 176 255 > 25% 146 197 222 255 > 50% 247 247 247 255 > 75% 244 165 130 255 > 100% 202 0 32 255 > nv 255 255 255 0 > > I tried several other combinations, but I cannot hava a transparency of > NULLs. > Where am I wrong? > All the best. -- Spatialys - Geospatial professional services http://www.spatialys.com
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