Convolution of a matrix

I've tried to code some of the problem and it is working for a 3*3 filter

Answer 1

[Ameer Hamza]

Check conv2() to avoid for loop. Following correct the mistake in your code

clc;
clear all;
close all;
im=double(imread('cameraman.tif'));
w=[1 1 1 1 1;1 1 1 1 1;1 1 1 1 1;1 1 1 1 1;1 1 1 1 1;];
k = floor(size(w,1)/2);
[M,N]=size(im);
g = zeros(M, N);
for i=k+1:M-k
    for j=k+1:N-k
        g(i,j)=sum(im(i-k:i+k,j-k:j+k).*w, 'all');
    end
end
figure,imshow(im,[]);
figure,imshow(g,[]);

A simple version with conv2

im=im2double(imread('cameraman.tif'));
w=ones(5);
g = conv2(im, w, 'same');
figure,imshow(im,[]);
figure,imshow(g,[]);

[The Eagle]

I was working on it and I didn't want to use inbuilt functions. However I tried your code without conv2 and I got an error using sum.

Error using sum

Trailing string input must be 'double', 'native',

'default', 'omitnan' or 'includenan'.

Error in Untitled (line 11)

g(i,j)=sum(im(i-k:i+k,j-k:j+k).*w, 'all');

This was the error. Can you tell me how to resolve it? Actually I'm new to MATLAB :/

[Ameer Hamza]

I guess you are using some older version of MATLAB. Replace this line with

g(i,j)=sum(sum(im(i-k:i+k,j-k:j+k).*w));

[The Eagle]

Yes I'm using R2016a thank you for helping. :)

[Ameer Hamza]

Glad to be of help.