how to get the (x,y) coordinate values of points touching bounding box

I have a binary object

How can i get the (x,y) co-ordinate value of the points touching the bounding box.

Answer 1

[KSSV]

I = imread('16.png') ;
[m,n] = size(I) ;
[y,x] = find(I) ;
% GEt mean 

mx = mean(x) ; my = mean(y) ;

% Line 1
L1 = [repmat(mx,m,1) (1:m)'] ;
L2 = [(1:n)' repmat(my,n,1) ] ;

P = [L1(1,1) L1(1,2) ; L1(end,1) L1(end,2) ;L2(1,1) L2(1,2) ; L2(end,1) L2(end,2)   ] ;
idx = knnsearch([x y],P) ;

imshow(I) ;

hold on

plot(x(idx),y(idx),'*r')

Answer 2

[Stalin Samuel]

Let us assume that, you have the image(from bounding box) in variable "Elysi". Then you can get the co-ordinate values using below code

[x1 y1]=find( Elysi(1,:)==1)
[x2 y2]=find( Elysi(:,end)==1)
[x3 y3]=find( Elysi(end,:)==1)
[x4 y4]=find( Elysi(:,1)==1)