[gdal-dev] Modify an image color table? ---SOLVED----

[Marco Stelluti]

Modify an image color table?
-- SOLVED --

Thanks a lot Frank and Luke.

This is the solution of my problem:
1) I built *.vrt file from ASCII file;
2) I used the <LUT> command like this:

----------------------------------------------------------------------------------------------------------
  <VRTRasterBand dataType="Byte" band="1">
   <ColorInterp>Red</ColorInterp>
    <ComplexSource>
      <SourceFilename relativeToVRT="1">file.asc</SourceFilename>
      <SourceBand>1</SourceBand>
     <LUT>
-9999:0,
-31:99,
-30:99,
-29:99,
-28:99,
-27:99,
-26:99,
-25:99,
-24:99,
-23:99,
-22:99,
-21:99,
-20:99,
-19:99,
-18:99,
-17:99,
-16:99,
-15:20,
-14:20,
-13:20,
-12:20,
-11:20,
-10:8,
-9:8,
-8:8,
-7:8,
-6:8,
-5:5,
-4:5,
-3:5,
-2:5,
-1:5,
0:3,
1:3,
2:3,
3:3,
4:3,
5:1,
6:1,
7:1,
8:1,
9:1,
10:1,
11:1,
12:1,
13:1,
14:1,
15:30,
16:30,
17:30,
18:30,
19:30,
20:52,
21:52,
22:52,
23:52,
24:52,
25:72,
26:72,
27:72,
28:72,
29:72,
30:94,
31:94,
32:94,
33:94,
34:94,
35:100,
36:100,
37:100,
38:100,
39:100,
40:100,
41:100,
42:100,
43:100,
44:100,
45:100,
46:100,
47:100,
48:100,
49:100,
50:100,
51:100,
52:100,
53:100,
54:100,
55:100,
56:100,
57:100,
58:100,
59:100,
60:90,
61:90,
62:90,
63:90,
64:90,
65:82
     </LUT>
    </ComplexSource>
  </VRTRasterBand>
  <VRTRasterBand dataType="Byte" band="2">
   <ColorInterp>Green</ColorInterp>
    <ComplexSource>
      <SourceFilename relativeToVRT="1">file.asc</SourceFilename>
      <SourceBand>1</SourceBand>
     <LUT>
-9999:0,
-31:99,
-30:99,
-29:99,
-28:99,
-27:99,
-26:99,
-25:99,
-24:99,
-23:99,
-22:99,
-21:99,
-20:99,
-19:99,
-18:99,
-17:99,
-16:99,
-15:8,
-14:8,
-13:8,
-12:8,
-11:8,
-10:22,
-9:22,
-8:22,
-7:22,
-6:22,
-5:33,
-4:33,
-3:33,
-2:33,
-1:33,
0:42,
1:42,
2:42,
3:42,
4:42,
5:60,
6:60,
7:60,
8:60,
9:60,
10:67,
11:67,
12:67,
13:67,
14:67,
15:87,
16:87,
17:87,
18:87,
19:87,
20:91,
21:91,
22:91,
23:91,
24:91,
25:95,
26:95,
27:95,
28:95,
29:95,
30:99,
31:99,
32:99,
33:99,
34:99,
35:90,
36:90,
37:90,
38:90,
39:90,
40:79,
41:79,
42:79,
43:79,
44:79,
45:65,
46:65,
47:65,
48:65,
49:65,
50:50,
51:50,
52:50,
53:50,
54:50,
55:20,
56:20,
57:20,
58:20,
59:20,
60:1,
61:1,
62:1,
63:1,
64:1,
65:1
     </LUT>
    </ComplexSource>
  </VRTRasterBand>
  <VRTRasterBand dataType="Byte" band="3">
   <ColorInterp>Blue</ColorInterp>
    <ComplexSource>
      <SourceFilename relativeToVRT="1">file.asc</SourceFilename>
      <SourceBand>1</SourceBand>
     <LUT>
-9999:0,
-31:99,
-30:99,
-29:99,
-28:99,
-27:99,
-26:99,
-25:99,
-24:99,
-23:99,
-22:99,
-21:99,
-20:99,
-19:99,
-18:99,
-17:99,
-16:99,
-15:69,
-14:69,
-13:69,
-12:69,
-11:69,
-10:68,
-9:68,
-8:68,
-7:68,
-6:68,
-5:65,
-4:65,
-3:65,
-2:65,
-1:65,
0:64,
1:64,
2:64,
3:64,
4:64,
5:60,
6:60,
7:60,
8:60,
9:60,
10:42,
11:42,
12:42,
13:42,
14:42,
15:1,
16:1,
17:1,
18:1,
19:1,
20:1,
21:1,
22:1,
23:1,
24:1,
25:1,
26:1,
27:1,
28:1,
29:1,
30:1,
31:1,
32:1,
33:1,
34:1,
35:1,
36:1,
37:1,
38:1,
39:1,
40:1,
41:1,
42:1,
43:1,
44:1,
45:1,
46:1,
47:1,
48:1,
49:1,
50:1,
51:1,
52:1,
53:1,
54:1,
55:1,
56:1,
57:1,
58:1,
59:1,
60:20,
61:20,
62:20,
63:20,
64:20,
65:43
     </LUT>
    </ComplexSource>
  </VRTRasterBand>
---------------------------------------------------------------------------------------------------------------------------------------------









2010/6/25 Frank Warmerdam <warmerdam at pobox.com>

> Marco Stelluti wrote:
>
>> 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?
>>
>
> Marco,
>
> Generally speaking GDAL color maps do not have an obvious application
> to negative or non-integer data.  You could use the "raster attribute
> table"
> mechanism to represent color assignments to negative values, but since so
> few applications make use of this data object it is nearly useless to do
> so.
>
> What application do you want the color table to work in?  How you handle
> the situation will depend on the output application.   If preserving the
> original pixel values isn't important you may want to reprocess/rescale
> your
> raster.
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam<http://pobox.com/%7Ewarmerdam>
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
>
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