assigned nodata values incorrect

[sprice]

Assigned 'nodata' values don't seem to be correctly read by gdalinfo. In the code below, I set the nodata value as '0 0 20', but then it is read back as '20 20 20', as near as I can tell. Note that I can't tell if this is a problem with gdalwarp or gdalinfo, because one might be setting the value wrong, the other might be reading it back wrong. If requested I can attach my files.

$ gdalinfo z1440.tif 
Driver: GTiff/GeoTIFF
Files: z1440.tif
Size is 1440, 1440
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.2572235630016,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (-180.000000000000000,90.000000000000000)
Pixel Size = (0.250000000000000,-0.125000000000000)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (-180.0000000,  90.0000000) (180d 0'0.00"W, 90d 0'0.00"N)
Lower Left  (-180.0000000, -90.0000000) (180d 0'0.00"W, 90d 0'0.00"S)
Upper Right ( 180.0000000,  90.0000000) (180d 0'0.00"E, 90d 0'0.00"N)
Lower Right ( 180.0000000, -90.0000000) (180d 0'0.00"E, 90d 0'0.00"S)
Center      (   0.0000000,   0.0000000) (  0d 0'0.01"E,  0d 0'0.01"N)
Band 1 Block=1440x1 Type=Byte, ColorInterp=Red
Band 2 Block=1440x1 Type=Byte, ColorInterp=Green
Band 3 Block=1440x1 Type=Byte, ColorInterp=Blue
$ gdalwarp -q -dstnodata '0 0 20' z1440.tif z1440.cs.tif
$ gdalinfo z1440.cs.tif 
Driver: GTiff/GeoTIFF
Files: z1440.cs.tif
Size is 1821, 911
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.2572235630016,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (-180.000000000000000,90.000000000000000)
Pixel Size = (0.197642353760524,-0.197642353760524)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (-180.0000000,  90.0000000) (180d 0'0.00"W, 90d 0'0.00"N)
Lower Left  (-180.0000000, -90.0521843) (180d 0'0.00"W, 90d 3'7.86"S)
Upper Right ( 179.9067262,  90.0000000) (179d54'24.21"E, 90d 0'0.00"N)
Lower Right ( 179.9067262, -90.0521843) (179d54'24.21"E, 90d 3'7.86"S)
Center      (  -0.0466369,  -0.0260921) (  0d 2'47.89"W,  0d 1'33.93"S)
Band 1 Block=1821x1 Type=Byte, ColorInterp=Red
  NoData Value=20
Band 2 Block=1821x1 Type=Byte, ColorInterp=Green
  NoData Value=20
Band 3 Block=1821x1 Type=Byte, ColorInterp=Blue
  NoData Value=20

[Even Rouault]

This problem was already reported as bug #2083 and is indeed specific to the GTiff driver