[Qgis-user] qgis-gdal: color-table problem to transform rasterimge

[Jan Tappenbeck]

hi !

i have to transform rasterimages from gauss-krueger to etrs by using 
gsb-files.

one of the image is:

Driver: GTiff/GeoTIFF
Files: C:/Users/tappenbeck/Desktop/Haan_Transformation/BP_001.tif
        C:/Users/tappenbeck/Desktop/Haan_Transformation/BP_001.tfw
Size is 1862, 2990
Coordinate System is `'
Origin = (2570979.517376476900000,5673843.182623745900000)
Pixel Size = (0.085247046186886,-0.085247491638684)
Metadata:
   TIFFTAG_SOFTWARE=IrfanView
   TIFFTAG_XRESOLUTION=200
   TIFFTAG_YRESOLUTION=200
   TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
Image Structure Metadata:
   COMPRESSION=PACKBITS
   INTERLEAVE=BAND
Corner Coordinates:
Upper Left  ( 2570979.517, 5673843.183)
Lower Left  ( 2570979.517, 5673588.293)
Upper Right ( 2571138.247, 5673843.183)
Lower Right ( 2571138.247, 5673588.293)
Center      ( 2571058.882, 5673715.738)
Band 1 Block=1862x4 Type=Byte, ColorInterp=Palette
   Color Table (RGB with 256 entries)
     0: 0,0,0,255
     1: 255,255,255,255
     2: 251,243,215,255
     3: 251,238,211,255
     4: 251,238,206,255
....
   254: 227,230,230,255
   255: 255,255,255,255

i want to use a gdal-statement by sven geggenus [1] for transformation. 
i open the gdal-function gdal > transformation (projection) and i copy 
the modify source in the command area at the buttom of the dialog:


gdalwarp -r cubicspline -multi -of HFA -s_srs "+init=epsg:31466 
+nadgrids=C:/Users/Tappenbeck/Desktop/Haan_Transformation/Mettmann_Beta2007.gsb 
+wktext" -t_srs EPSG:25832 -of GTiff 
C:/Users/tappenbeck/Desktop/Haan_Transformation/BP_001.tif 
C:/Users/tappenbeck/Desktop/Haan_Transformation/BP_001_trans.tif

after apply the command i get following message:

Output dataset 
C:/Users/tappenbeck/Desktop/Haan_Transformation/BP_001_trans.tif exists,
but some commandline options were provided indicating a new dataset
should be created. Please delete existing dataset and run again.

can anyone help me to do the transformation ?

ADDITITION:
it is only possible to modify the gdad-command for single use - file by 
file.

is it possible to use usermodifiy-command for folder-transformations ?

please help.

reagards Jan :-)




[1] 
http://www.fossgis.de/konferenz/2010/attachments/71_osm-datenaufbereitung-fossgis-2010.pdf 
- Page 8