I am trying to cut this raster in order to drop the outside of the walls white area and the area with the dots. I made one step using as mask the green polygon but i couldn't remove the inside of the walls area with the dots. Any idea?
It works this way:
Create a clip polygon for the outer border
Create a clip poygon for the inner border
Create a multipolygon with the second layer as a hole using
Vector -> Geoprocessing -> Difference
Clip the Raster to that multipolygon using
Raster -> Extraction -> Clipper