(Continued...) Dear GRASSers, how do you really export as GeoTiffs your raster maps to view in OpenEV, QGIS?
I think I solved my problem by removing color tables (as Markus Metz suggested), exported groups, nodata=-9999 and, very important, setting in my loop over all groups a "g.region rast=$i" each time. Without it I couldn't see anything whenever I have put an out of range nodata value. I am posting my questions I had before "solving" my problem anyway. Maybe there is still something interesting to read/ask/answer. Thank you, Nikos. --- Some info: uname -a Linux vertical 2.6.24-19-generic #1 SMP Fri Jul 11 21:01:46 UTC 2008 x86_64 GNU/Linux gdalinfo --version GDAL 1.5.2, released 2008/05/29 g.version GRASS 6.4.svn (2008) For the records: I am not interested to open my images with any other tool than TheGIMP, QGIS, OpenEV (maybe ImageMagick). A. I export the groups (red, green and blue maps for each group) with: for i in `g.mlist group`; do r.out.gdal $i type=Byte out=$i.tiff; done" I can see the exported images in QGIS, OpenEV. However, this sets 255 as "nodata" which is something that I don't want. Whenever I set a nodata value out of range [1] (for Byte that would be smaller than 0 or bigger than 255 --- right?) I can't see propely the exported tiffs in either QGIS or OpenEV. In QGIS nothing appears and in OpenEV the individual tiff's (loading with openev -h *.tiff) "flash" and dissapear to leave a black screen. Is there a way to use r.out.tiff to export groups? B. Frank Warmerdam wrote [2] "There is no standard tag in TIFF or GeoTIFF for describing nodata pixel values. The only approach you might be able to use is to somehow add an alpha channel and mark the nodata regions as alpha=0; however, I'm not sure how you would go about that." Is this related to the "nodata" problem? If yes, has anybody found a solution to it? Could the "metaopt=" option of r.out.gdal be useful here? C. I can't seem to export raster maps with gdal_translate as described in Markus' blog [3] (copy-paste from [3] gdal_translate -of Gtiff /usr/local/share/grassdata/spearfish/PERMANENT/cellhd/soils soilmap.tif) D. What about this work-around [4] that Maciek postd some time ago? [1] http://www.gdal.org/classGDALRasterBand.html [2] http://www.nabble.com/Remove-black-background-of-GeoTiff-td6400610.html [3] http://gfoss.blogspot.com/2008/06/gdal-raster-data-tips-and-tricks.html [4] http://www.mail-archive.com/[EMAIL PROTECTED]/msg01634.html _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
