Ralf, Your tif files seem to use color tables. You may be able to edit the color table to represent RGBA instead of RGB with A value set to 0 for nodata and 1 elsewhere. I don't know much about handling the color tables.
If you don't want to deal color tables, use the -expand option in gdal_translate. First use "-expand rgb" to create RBG tiffs. Then use gdalbuildvrt with -srcnodata and -addalpha options. Finally, convert it All.tif using gdal_translate. On Mon, Feb 8, 2010 at 5:43 PM, Ralf Wagner <[email protected]> wrote: > Unfortunately I have absolutely no idea how to deal with this transparency > problem - all my trials failed. > I am experimenting on four properly referenced GeoTiff, overlapping files > with white margins. > My (temporary) goal was to obtain ONE GeoTIFF file from these FOUR source > files - but, of course, without white margins between them. > So, first I created VRT file from my source GeoTiffs: > > gdalbuildvrt -srcnodata "255 255 255" All.vrt Ac3.tif Ac4.tif Ca1.tif > Ca2.tif > > and then GeoTiff from this VRT file: > > gdal_translate -of GTiff All.vrt All.tif > > But white stripes still existed. Also, additional step of creating separate > VRT files for each GeoTiff file and using these files as components for > "All.vrt" didn't help. Messing around with -vrtnodata, -hidenodata etc. > didn't help also. Using -addalpha option causes warning during destination > GeoTiff file generation: "Unable to export color table to GeoTIFF file" and > resulting file is broken. > > So, I am stuck... > > Do you have any idea what can I try next? > > Best regards, > Ralf Wagner > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev > -- Best regards, Chaitanya kumar CH. /tʃaɪθənjə/ /kʊmɑr/ +91-9848167848 17.241582N 80.142635E
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