[Gdal-dev] src/dstnodata not effective for indexed colour

[Matt Wilkie]

Hi GDAL,

When using gdalwarp source and destination nodata parameters on an RGB 
image one can remap the values (e.g. change nodata from 255,255,255 to 
0,0,0 or 255,0,0 or ...). This doesn't appear to work with indexed 
colour images. Is this by design, a bug, or just not implemented?


# this works, pixels which are 255 (white) in input
# will be 150 (grey) in output
gdalwarp -srcnodata "255 255 255" -dstnodata 150 rgb.tif grey-nodata.tif

# doesn't work, source values of 255 (white) remain unchanged in output
gdalwarp -srcnodata "255 255 255" -dstnodata 150 indexed.tif grey-nodata.tif


cheers,

-- 
matt wilkie
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