% boundary demo.m
% (C) 2006 by Yu Hen Hu
% created: Dec. 19, 2006
% demonstrate morphological boundary extraction
% 
clear all, close all

A0=imread('myshap4.bmp');
imshow(A0); % a heart shape hand drawing
title('original image');
pause
% A0 contains mostly 1s and the drawing contains 0s, uint8
A1=1-double(A0); % invert black and white

B=ones(3); 
A2=imopen(imclose(A1,B),B); % fill 1 pixel hole and remove sticks

A3=imfill(A2,[100 100]); % fill the interior

A=double(A2) + double(A3);

imshow(A),title('after interior filling using imfill');
pause
Ab=A-double(erode(A,B));

imshow(Ab), title('extracted boundary');

clear A1 A2 A3; Ac=Ab;

vidx=[[1:20:280] 280];

Ac(vidx,:)=1; Ac(:,vidx)=1;

imshow(Ac)