find the polygon enclosing the given coordinates and find the coordinates of polygon (python opencv)

Question

Example image used in program

I am trying to find the coordinates of a polygon in an image (just like flood fill algorithm we are given a coordinate and we need to search the surrounding pixels for the boundary, if boundary is found we need to append its coordinate to the list if not we need to keep searching other pixels.)and if all the pixels are traversed the program should stop returning the list of pixels. usually color of boundary is black and image is a gray scale image of maps of building.

Answer 1

It seems that flood-fill will be good enough to completely fill a room, despite the extra annotations. After filling, extract the outer outline. Now you can detect the straight portions of the outline by checking the angle formed by three successive points. I would keep a spacing between them to avoid local inaccuracies.

You will find a sequence of line segments, possibly interrupted at corners. Optionally use line fitting to maximize accuracy, and recompute the corners by intersecting the segments. Also consider joining aligned segments that are interrupted by short excursions.

If the rooms are not well closed, flood filling can leak and you are a little stuck. Consider filling with a larger brush, though this can cause other problems.