Hi Dario, > I have a layer of polygons, these polygons are cut by two parallel lines. > Sometimes just one line crosses the polygon, dividing it into two. > need to create new polygons, formed by the polygon area that is contained > between the lines, and the areas that are outside the inner lines, and the > second case to create new polygons formed by the two areas divided by the > line. > Is there any plugin or geoprocess in quantum gis what running this? > I can only do the reverse process, which is the polygon cut the lines that > intersect with it, but I can not do otherwise with the lines dividing the > polygon. I don't know of any plugin that will do this, but it can certainly be done using the Python scripting interface in QGIS. The attached Python script *should* do what you want for most basic applications. A usage example is given at the top of the script, but basically you just save the script somewhere where the QGIS Python console can find it (best bet is your ~/.qgis/python folder where all your plugins are installed, if you don't know where this is, the Python plugin installer should indicate this on the main dialog). Then simply type (into the QGIS Python console):
>>> canvas = qgis.utils.iface.mapCanvas() >>> layer_a = canvas.layer(0) # polygon layer >>> layer_b = canvas.layer(1) # line layer >>> from split_polygons import split_polygons >>> split_polygons(layer_a, layer_b, "/home/username/Desktop/output.shp") This assume that your polygon layer in the top layer in the layer list (and is visible), and the line layer in the second from the top (and is also visible). The 3rd argument to split_polygons is the output path for the resultant shapefile, and can be any valid path string, so on Windows it might be something like: C:\workingfolder\output.shp Let me know if you need any further help with the script. It's really just a quick stab at this. I tested it using very basic polygons and lines that I hand digitised for testing purposes. Eventually I'll try to make it into a plugin, but until then it should at least get you going. Regards, Carson -- Carson J. Q. Farmer ISSP Doctoral Fellow National Centre for Geocomputation National University of Ireland, Maynooth, http://www.carsonfarmer.com/
split_polygons.py
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