Many questions... Thank you in advance, Nikos :-) Importing RGB tiff's (size: 2500, 2500 --- with INTERLEAVE=PIXEL) in GRASS' database splits them, as expected, in red, green and blue raster maps. After MASKing out unwanted areas, how should one export the maps to end-up with tiff files similar (or improved) to the original ones?
1. Using r.composite and exporting with r.out.gdal gives "white" as nodata. Whenever I set "nodata=0" I don't get a viewable photo 2. r.out.tiff does not provide a "nodata" option. What's the necessity of r.out.tiff if r.out.gdal can do the same with more options? 3. GeoTiff metadata are lost always (?) while exporting with r.out.gdal. 4. The createopt="INTERLEAVE=PIXEL" is not respected by r.out.gdal (?) e.g. r.out.gdal in=koblenz_2618_5566.red_i type=Byte out=/home/nik/grassdb/rlp_fgaps/data/orthophotos/koblenz/test/koblenz_2618_5566.red_i2 createopt="INTERLEAVE=PIXEL,TFW=YES" gdalinfo koblenz_2618_5566.red_i2 [...] INTERLEAVE=BAND [...] 5. What is the correct way to import an rgb photo, process, export back in GeoTiff? 6. Is it better to export the red, green and blue GRASS raster maps one-by-one and merge them with gdal_translate (or gdal_merge.py)? 7. Exporting a group (the ones that automatically are created for each imported photo and contain the red, green and blue components respectively), gives "INTERLEAVE=PIXEL" but "Block=2500x3". Is it correct to force createopt="BLOCKYSIZE=1" which gives "Block=2500x1"? 8. I read in Markus' blog [1] how to "write out a GRASS raster map to GeoTIFF -- this format includes the coordinates within the file's metadata" using gdal_translate. Doesn't r.out.gdal do that and if not why? There is also that tiles provide "Fast image display...". From my small experience, I can't really judge if TILES accelerate image display. Sometimes I have the impression that they are slower that STRIPPED tiffs. 8. There are several compression methods? Does compression affect significantly reading/displaying an image? 9. Should one prefer another file format? [1] http://gfoss.blogspot.com/2008/06/gdal-raster-data-tips-and-tricks.html _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
