I am trying to generate label points from my polygons. The Polygon->Centroid works great except that if the centroid happens to land in a hole it is still returned. I need to get a single point (Centroid if that point is within the polygon) a point within the polygon if the centroid happens to be outside of the polygon.
[GIS] Getting single point from polygon Centroid if within polygon or any point if not using QGIS
qgis
Related Solutions
I've only found this work-around so far:
- You need to load the polygon layer twice.
- The lower layer is styled using the Centroid Fill option.
- The upper layer uses the same style but without the Centroid Fill layer.
- Enable labeling for the upper layer. Placement should be 'horizontal' or 'free'.
- In Print Composer, delete the upper layer from the legend items list.
This is far from optimal, but I don't think this special feature is going to be implemented soon into the renderer.
If you do not care about whether the point is a centroid or not, just use Vector -> ResearchTools -> Random Points. You may define to place a single point per each polygon in a layer. Also you may create centroids for initial polygons, delete points that do not intersect any polygon, save polygons without points as a separate layer, create random points for this polygosns and in the end copy these random points to centroids layer.
Best Answer
I found a better solution, using OGR. The following will create a point that always falls on the surface of the polygon:
You can see some examples here.