How to Create Alternating Black Columns Across an Image?

I have an image X and I would like to create black columns going across the image that are 16 pixels thick with a distance of 16 pixels between each column and I have no idea how to do this. The best I could do was make one column using this line of code:

X(:,1:16,:) = 0;

Also I am not allowed to solve the problem using loops.

Answer 1

[Jose Marques]

Hello Richard! You can try this:

size_of_column = 16;
img = imread('image_exemple.jpg');
imshow(img);
mask = zeros(size(img));
for i=1:size(mask,2)
    if(mod(round(i/size_of_column),2) == 1)
        mask(:,i,:) = 1;        
    end
end
figure();
img_final(:,:,:) = uint8(double(img(:,:,:)).*mask(:,:,:));
imshow(img_final)

The result:

[Richard Zareck]

Hi Jose,

This is exactly the result I need however I am not allowed to use loops which is why I am very confused. Is there a way to do the same thing without the loop? Thank you for your help!

[Richard Zareck]

Also if it is of any help answering this will also allow me to solve my problem

https://www.mathworks.com/matlabcentral/answers/355894-replacing-values-of-a-larger-matrix-with-that-of-a-smaller-matrix

[Jose Marques]

Hello Richard. I really prefer the first code with the for loop. But the code above works:

size_column = 16;
img = imread('img.jpg');
imshow(img);

imgSiz = [size(img,1),size(img,2)];
blkSiz = [size(img,1),size_column];
numRep = imgSiz./blkSiz;
basMat = toeplitz(mod(0:numRep(1)-1,2),mod(0:numRep(2)-1,2));
mask(:,:,1) = repelem(basMat,size(img,1),size_column);
aux_matrix = zeros(size(img,1),(size(img,2)-size(mask,2)));
mask = horzcat(mask,aux_matrix);

mask(:,:,2) = mask(:,:,1);
mask(:,:,3) = mask(:,:,1);
figure();
img_final(:,:,:) = uint8(double(img(:,:,:)).*mask(:,:,:));
imshow(img_final);

[Jose Marques]

[Richard Zareck]

Thank you for your help this works as well!

[Jose Marques]

Nice work!

Answer 2

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/288038-how-to-create-a-checkerboard-image-without-using-the-inbuilt-function

[Richard Zareck]

I need my picture to look like this

[Walter Roberson]

clown(:, 1:32:end, :) = 0;
clown(:, 2:32:end, :) = 0;
clown(:, 3:32:end, :) = 0;
...
clown(:, 16:32:end, :) = 0;