graph.route_through_array, a route is "outside"

Hello, A contour is extracted from a greyscale image ("walls") where the background is set to 255. Several points near the contour are used to compute a path with graph.route_through_array: mincost = graph.route_through_array(walls ,p1,p2,fully_connected=True) One found path is not completely inside the array. When fully_connected=False is used all the paths are inside the chromosomes (i.e. they do not cross regions where grey level=255). How to get a minimal cost route "inside" a particle (<>255)? Thank you Jean-Patrick <https://lh6.googleusercontent.com/-YBi4a6avWfw/UJvgFAyisjI/AAAAAAAAA98/A5ADk...>