i don't know what is wrong with my code for finding edges

i'm new to this, i got this Question where i have to find edge for 2 images and their common edge but it keeps showing me error :/ for if and end statement

% i = imread('file:///C:/Users/Rana/Desktop/firstCV.png');
j = imread('file:///C:/Users/Rana/Desktop/secondCV.png');

if (size(i,3)==3)
    I= rgb2gray(i);
elseif I==i
end
e1 = edge(I, 'canny');

%-------------------------
if (size(j,3)==3)
    I2 = rgb2gray(j);
elseif I2==j
end
e2 = edge(I2, 'canny');

edge = e1+e2;
imshow(edg);
secretcode = e1+e2-1;
imshow(secretcode);

[Rik]

The first problem I notice is that you wrote else if, instead of elseif.

[per isakson]

I replaced else if by elseif when formatting the code

[per isakson]

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Answer 1

[Image Analyst]

You can't have this:

elseif I==i

like the error message says. And you also switched to the badly-named j from the even worse-named i but then still checked for i. Plus you're using "edge", which is the name of a built-in function, as your variable name. Plus several more problems. I made it more robust by checking that the image sizes match. Try it like this:

grayImage1 = imread('eight.tif');  % Whatever.
subplot(2, 3, 1);
imshow(grayImage1, []);
axis on;
title('Gray Image 1', 'FontSize', 15);

grayImage2 = imread('coins.png');  % Whatever.
subplot(2, 3, 2);
imshow(grayImage2, []);
axis on;
title('Gray Image 2', 'FontSize', 15);

if ndims(grayImage1) == 3
  grayImage1 = rgb2gray(grayImage1);
end
edgeImage1 = edge(grayImage1, 'canny');
subplot(2, 3, 4);
imshow(edgeImage1, []);
title('Edge Image 1', 'FontSize', 15);

%-------------------------
if ndims(grayImage2) == 3
  grayImage2 = rgb2gray(grayImage2);
end
edgeImage2 = edge(grayImage2, 'canny');
subplot(2, 3, 5);
imshow(edgeImage2, []);
title('Edge Image 2', 'FontSize', 15);

% Make sure images are the same size before we try to add them.
if ~isequal(size(edgeImage1), size(edgeImage2))
  errorMessage = 'Images are not the same size';
  uiwait(errordlg(errorMessage));
  return;
end

edgeImage = edgeImage1 + edgeImage2;
subplot(2, 3, 3);
imshow(edgeImage, []);
title('Sum of Edge Images', 'FontSize', 15);

secretcode = edgeImage1+edgeImage2-1;
subplot(2, 3, 6);
imshow(secretcode, []);
title('Secret Code', 'FontSize', 15);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.04, 1, 0.96]);