How to coded this filter in Matlab

clc

clear all

img=double(imread('cameraman.tif'));

imshow(uint8(img))

[m n]=size(img);

w = ones(3)

for i=0:m-3

for j=0:n-3

sum=0;

for k=1:3

for l=1:3

sum = sum + img(i+k,j+l)*w(k,l);

end

end

img1(i+1,j+1) = sum/9;

end

end

img2 = uint8(img1);

figure

imshow(img2)

%imwrite(img2,‘output.png','png');

I coded for 1/9*(ones(1) but i can't write for 1/16*[1,2,1;2,4,2;1,2,1] in Matlab. I don't know how to do this. I need same coded for 1/16*[1,2,1;2,4,2;1,2,1]. and if we take i and j = 0, how should the code be? Would you help me please?

Answer 1

[Ameer Hamza]

Write the code like this

clc
clear all
img=double(imread('cameraman.tif'));
imshow(uint8(img))
[m n]=size(img);
w = 1/9*ones(3); % <---- ones(3) is divided by 9
for i=0:m-3
    for j=0:n-3
        sum=0;
        for k=1:3
            for l=1:3
                sum = sum + img(i+k,j+l)*w(k,l);
            end
        end
        img1(i+1,j+1) = sum; % <---- division by 9 is removed.
    end
end
img2 = uint8(img1);
figure
imshow(img2)

Then you can simply replace 'w' with

w = 1/16*[1,2,1;2,4,2;1,2,1];

and it will display correct image.

[Rooter Boy]

Sir, are you sure? Isn't it necessary to change the for loops?

I think your answer is full false.

[Ameer Hamza]

What is wrong in this? For w = ones(3), it is equivalent to your code.

[Rooter Boy]

Sir, if we take i and j = 1, how should the code be? Would you help me please?

[Ameer Hamza]

What do you mean by i=1 and j=1. In your current code, i and j also take value of 1.

[Rooter Boy]

We coded using i=0, j=0

for i=0:m-3

for j=0:n-3

if we take i and j = 1, how should the code be?

[Ameer Hamza]

You can just use

for i=1:m-3
    for j=1:n-3

[Rooter Boy]

Sir, could you help me when you are available?

https://www.mathworks.com/matlabcentral/answers/652808-nwc-and-lcm-code-block-in-matlab