Is there a way to extract polygon lines from a map loaded as a .tiff file on QGIS? The original map (see below) of Venice is a scan from a book and has all the lines I need (they mark historical parishes in the city), but it would take to long to manually trace them. I need each parish to be its own entity/polygon.
This image is not georeferenced, and I don't need it to be right now actually. I just find it useful to work on QGIS when dealing with maps.