[gdal-dev] Modify original ColorTable in VRT & TIFF files

[Hotmail]

Hi Lars,
Thanks a lot for the tip with sed, it works fine.

> sed -i '/<Metadata domain="IMAGE_STRUCTURE">/,/<\/Metadata>/d; /<Entry c1="0" c2="0" c3="0" c4="255" \/>/,/<Entry c1="255" c2="255" c3="255" c4="255" \/>/d; /<ColorTable>/r COLORTABLE.txt' $F_VRT

> Le 23 avr. 2021 à 11:31, lars.schylberg at blixtmail.se a écrit :
> 
> Hi again,
> 
> Some other tricks.  To extract the color table from a PNG I often use pngcheck.
> 
> pngcheck -p /data/tests/500K_large_pct.png \
> | sed '1,2d' \
> | awk 'NR < 257' \
> | sed 's/[=].*$//' \
> | sed 's/[(:)]//g' \
> | sed 's/,/ /g' \
> | sed 's/...//' > color.txt
> 
> 
> You could add an extra print command if you want to write it in other format:
> | awk -F, '{printf "%d,%d,%d,255\n", $1, $2, $3}'
> 
> To assemble a vrt and a tif I have used gdalbuildvrt command with the argument "-separate".
> You get a new vrt that You then convert with gdal_translate.
> 
> Have fun / Lars Schylberg
> 
> 
> 22 april 2021 kl. 22:50, lars.schylberg at blixtmail.se skrev:
> 
>> Hi, 
>> 
>> I had to deal a lot with palette tiff images a couple of years ago.
>> 
>> What I did was that edited the vrt files with sed inline editing:
>> 
>> Some examples:
>> 
>> Insert a text file after the row that is: /VRTRasterBand dataType="Byte" band="1" The inserted file
>> here is orig_colortable_vrt.txt:
>> 
>> sed -i -e '/VRTRasterBand dataType="Byte" band="1"/r orig_colortable_vrt.txt' image_6.vrt
>> 
>> Remove a certain line that contains "NoDataValue"
>> 
>> sed -i -e '/NoDataValue/d' image_6.vrt
>> 
>> There a also a sed commands to delete certain rows. Just read many sed examples.
>> 
>> Have fun / Lars Schylberg
>> 
>> 22 april 2021 kl. 20:25, "Hotmail" <rlelamer at hotmail.fr> skrev:
>> 
>>> Hi all,
>>> 
>>> I'm looking to modify the original ColorTable, when georeferencing, PNG => gdal_translate +
>>> gdalwarp => TIFF.
>>> 
>>>> gdal_translate -of VRT -a_srs EPSG:4326 file_png file_vrt -a_ullr xxxx
>>>> gdalwarp -s_srs EPSG:4326 -t_srs EPSG:3857 file_vrt file_tiff
>>> 
>>> If I open the VRT file and do the edit manually, the output TIFF file is correct.
>>> The problem is that I have 524288 files ... so I would like to do the modification automatically,
>>> via gdal_translate.
>>> But I don't quite understand using the parameters of the command ...
>>> 
>>> • Original VRT & TIFF files
>>> 
>>> # VRT
>>> <VRTRasterBand dataType="Byte" band="1">
>>> <ColorInterp>Palette</ColorInterp>
>>> <ColorTable>
>>> <Entry c1="0" c2="0" c3="255" c4="255" />
>>> <Entry c1="255" c2="255" c3="255" c4="255" />
>>> <Entry c1="0" c2="0" c3="0" c4="255" />
>>> [...]
>>> <Entry c1="0" c2="0" c3="0" c4="255" />
>>> </ColorTable>
>>> </VRTRasterBand>
>>> 
>>> # TIFF
>>> Band 1 Block=63153x1 Type=Byte, ColorInterp=Palette
>>> Color Table (RGB with 256 entries)
>>> 0: 0,0,0,255
>>> 1: 255,255,255,255
>>> 2: 0,0,0,255
>>> [...]
>>> 255: 0,0,0,255
>>> 
>>> I want this :
>>> • Modified VRT and TIFF files
>>> 
>>> # VRT
>>> <VRTRasterBand dataType="Byte" band="1">
>>> <ColorInterp>Palette</ColorInterp>
>>> <ColorTable>
>>> <Entry c1="0" c2="0" c3="255" c4="255" />
>>> <Entry c1="0" c2="255" c3="0" c4="255" />
>>> <Entry c1="255" c2="0" c3="0" c4="255" />
>>> [...]
>>> <Entry c1="255" c2="0" c3="0" c4="255" />
>>> </ColorTable>
>>> </VRTRasterBand>
>>> 
>>> # TIFF
>>> Band 1 Block=63153x1 Type=Byte, ColorInterp=Palette
>>> Color Table (RGB with 256 entries)
>>> 0: 0,0,255,255
>>> 1: 0,255,0,255
>>> 2: 255,0,0,255
>>> [...]
>>> 255: 255,0,0,255
>>> 
>>> Whatever I find, redirects me to gdaldem (which I can't use). In gdal_translate, it seems to me
>>> that the parameter -colorinterp_X might be suitable
>>> but I can't find any concrete examples (or I have not looked in the right place).
>>> 
>>> I want to impose the following parameters:
>>> Band 1
>>> Type = Byte
>>> ColorInterp = Palette
>>> Color Table (RGB with 256 entries)
>>> 
>>> In ColorTable:
>>> Entry 0 = 0,0,255,255
>>> Entry 1 = 0,255,0,255
>>> Entries 2 to 255 = 255,0,0,255
>>> _______________________________________________
>>> gdal-dev mailing list
>>> gdal-dev at lists.osgeo.org
>>> https://lists.osgeo.org/mailman/listinfo/gdal-dev
>> 
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