[gdal-dev] gdalwarp -dstnodata

Benoît Andrieu bea at ixsea.com
Fri May 28 09:04:00 EDT 2010

Hi Sven,

It's not the role of gdalwarp to tell the color to be rendered with no 
data values.
In your example, gdalwarp tells the renderer to display the pixels with 
values equal to 255 with a color specified by the renderer.
It only adds in the tif files a tag that set the white color as transparent.

For example, with Mapserver as a renderer, you will set in the mapfile 
the background color as white (IMAGECOLOR 255 255 255).

What software are you using to view your files ?
What is the color in the source file that you want as transparent / white ?



Le 28/05/2010 11:05, Sven Schroeter a écrit :
> Hi,
> I use the gdalwarp utility to transform geotifs:
> gdalwarp -co compress=lzw -s_srs "+proj=tmerc +lat_0=0 +lon_0=6 
> +k=1.000000
> +x_0=2500000+y_0=0 +ellps=bessel +units=m
> +towgs84=590.1181,99.6226,340.1890,1.185095,-1.334952,-2.904521,16.51559" 
> -t_srs
> "+proj=utm +ellps=GRS80 +datum=WGS84 +zone=32" -dstnodata 255
> bbp07231053_2559-wla_0053-1a.tif out/bbp07231053_2559-wla_0053-1a.tif
> I want to convert the new "nodata-areas" to be displayed in white (255 
> 255
> 255)
> if I try -dstnodata 255  or -dstnodata "255 255 255" in every picture 
> the no
> data areas have other colors but not white. What can I do?
> Thanks
> Sven
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