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    %% Trace Boundary and Visualize Contours
% 
%%
% Read image and display it.

% Copyright 2015 The MathWorks, Inc.

BW = imread('blobs.png');
imshow(BW,[]);
%%
% Pick an object in the image and trace the boundary. To select an object,
% specify a pixel on its boundary. This example uses the coordinates of a
% pixel on the boundary of the thick white circle, obtained through visual
% inspection using |impixelinfo|. The example specifies the initial search
% direction, the connectivity, how many boundary pixels should be
% returned, and the direction in which to perform the search.
r = 163;
c = 37;
contour = bwtraceboundary(BW,[r c],'W',8,Inf,'counterclockwise');
%%
% Plot the contour on the image.
hold on;
plot(contour(:,2),contour(:,1),'g','LineWidth',2);