I have a raster map that I generated from cropping/masking from a bigger raster map. It produced a map with only a portion of not null values. I only want to have a map that is zoomed in to the portion of not null values in order to save it into a PNG file. I only succeeded in setting the region (g.region) to the portion, but not cutting the map that only contains that portion.
you can do that with the help of MASK and r.resample (make a copy of your raster before) This video would guide you : http://www.youtube.com/watch?v=0tfcyxRvEJ8