[gdal-dev] Modify an image color table?

[Marco Stelluti]

Hi,
I'm a new gdal user and I've a little problem.

I have to modify the color to an ASCII raster.

1_ I converted the raster using gdalbuildvrt;
2_ I modified the file *.vrt adding:
    <ColorInterp>Palette</ColorInterp>
 <ColorTable>
<Entry c1="255" c2="255" c3="255" c4="255"/>
<Entry c1="0" c2="0" c3="150" c4="255"/>
<Entry c1="0" c2="0" c3="150" c4="255"/>
.......
 </ColorTable>
3_ I know: "The entries are ordered and will be assumed to start from color
table entry 0"
4_ But I have some negative value on the ASCII raster, the range is from -31
to 65.
5_ How I can resolve this problem?

Thanks in Advance
Marco
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