I was wondering if it were at all possible to manipulate/massage rasters (eg Geotiff) using Qgis plugins or Grass?? By manipulate, I mean manually smooth off interpolation artefacts, blended surface disagreement, etc. Like a photoshop 'touch up tool' if you will. I've had a crack at trying with GIMP, but I lose all my geotiff info. If anyone hasn't already developed it, they should.
Update: GIMP Works for 8bit Geotiff files, however, all data below 0m and above 255m are lost. Need to find a software package that deals with float64 Geotiffs.