Edge Linking and Boundary Detection, Hough Transform with example in DIP & implementation in MATLAB

Video lecture series on Digital Image Processing, Lecture: 50,
Edge Linking and Boundary Detection, Hough Transform and its implementation in MATLAB
What is edge linking?
Which are different edge linking approaches?
What is Hough transform?
Explain Hough transform with example.
Explain steps in Hough transform.


Link to download ppts/lecture notes:
https://drive.google.com/drive/folder...

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MATLAB codes used in the video are given below:

% MATLAB code for Hough Transform
close all;
clear all;
clc;
I = imread('circuit.tif');
subplot(2,2,1);imshow(I);title('Original Image')
rotI = imrotate(I,33,'crop');% rotate and crop image for better understanding
BW = edge(rotI,'canny'); % edge finding using Canny detector
[H,theta,rho] = hough(BW); % Computing the Hough transform
% Display the transform
subplot(2,2,2);
imshow(H,[],'XData',theta,'YData',rho,...
'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
title('The Hough Transform')
% Find the peaks in the Hough transform matrix, H
P = houghpeaks(H,5,'threshold',ceil(0.3*max(H(:))));
% Plot the peaks
subplot(2,2,3);
imshow(H,[],'XData',theta,'YData',rho,...
'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
x = theta(P(:,2));
y = rho(P(:,1));
plot(x,y,'s','color','white');
title('The peaks in Transform')
% Find lines in the image
lines = houghlines(BW,theta,rho,P,'FillGap',5,'MinLength',7);
% Create a plot that superimposes the lines on the original image
subplot(2,2,4); imshow(rotI), hold on
max_len = 0;
for k = 1:length(lines)
xy = [lines(k).point1; lines(k).point2];
plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');

% Plot beginnings and ends of lines
plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');

% Determine the endpoints of the longest line segment
len = norm(lines(k).point1 - lines(k).point2);
if ( len (greater than) max_len)
max_len = len;
xy_long = xy;
end
end

% highlight the longest line segment
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','cyan');
title('Image with highlighted lines')