How to Close an Open Contour

I have generated the skeleton of a binary shape, and now I want to connect the endpoints in a way that forms a closed contour. The goal is to identify the endpoints of the skeletonized structure and connect them in a meaningful way to reconstruct a continuous, closed boundary. I wrote the code in matlab but something is wrong.

clc;

clear;

close all;

img = imread('imag10_Seg.png');

bw = imbinarize(img);

skeletonImage = bwmorph(bw, 'skel', inf);

figure();

imshow(skeletonImage);

endpointsImage = bwmorph(skeletonImage, 'endpoints');

[labeledImage, numBlobs] = bwlabel(skeletonImage);

measurements = regionprops(labeledImage, 'PixelList');

[rows, cols] = find(endpointsImage);

endpoints = [cols, rows];

[labeledImage, numBlobs] = bwlabel(bw);

measurements = regionprops(labeledImage, 'PixelList');

for k = 1 : numBlobs

imline();

end

Answer 1

[DGM]

Without the source image, I'm just going to use a contrived source.

% a grayscale image
inpict = imread('opencontour.png');
imshow(inpict)

% binarize it somehow
bw = imbinarize(inpict); 

% use bwskel() instead to get rid of extraneous branches
% this may end up truncating the contour if you're not careful
skel = bwskel(bw,'minbranchlength',30);

% find all the endpoints
skelEP = bwmorph(skel,'endpoints');

% there should probably be some effort here
% to make sure that there are only two relevant
% endpoints left
% ....

% draw lines between the endpoints
% this only makes sense if there are only two endpoints
% bridge = bwconvhull(skelEP);

% alternatively, this just draws a polyline between the points
% it still only makes sense if there are only two endpoints
V = vertcat(regionprops(skelEP,'centroid').Centroid);
bridge = brline_forum(size(skelEP),V);

% combine the two
outpict = skel | bridge;

imshow(outpict)

There's probably a way to use watershed here, but I'm not sure if that's any more convenient/reliable.