i want a randomly scramble of a divided image into 4 blocks

please if i have image 256X256 and i divided it into 4 blocks, how can i scramble the blocks randomly or change the orders of the 4 blocks ,then i stitch them together again after this permutation or this changing inorder to change the parameters of the image and got a cihper one??

should i convert it to vector and then permuted or i can permuted it in blocks case?? please i want the code

Answer 1

[Matt J]

Using mat2tiles (which you must Download),

Image=imresize(imread('saturn.png'), [256,256]);

im=mat2tiles(Image,[128,128,inf]);

newImage=cell2mat(  im(randperm(256/128), randperm(256/128)) );

subplot(1,2,1),imshow(Image);
subplot(1,2,2), imshow(newImage)

Answer 2

[Jan]

img  = uint8(((0:255) + (0:255).') / 2);  % Test image
s    = size(img);

% Split image to blocks:
img4 = reshape(img, s(1) / 2, 2, s(2) / 2, 2);
img4 = permute(img4, [1, 3, 2, 4]);
img4 = reshape(img4, s(1)/2, s(2)/2, 4);

% Mix:
img4 = img4(:, :, randperm(4));

% Get matrix again:
img4 = reshape(img4, s(1)/2, s(2)/2, 2, 2);
img4 = permute(img4, [1, 3, 2, 4]);
result = reshape(img4, s);
imagesc(result)

Or:

img  = uint8(((0:255) + (0:255).') / 2);  % Test image
s    = size(img);
C    = mat2cell(img, [s(1)/2, s(1)/2], [s(2)/2, s(2)/2]);
C(:) = C(randperm(4));
result = cell2mat(C);
imagesc(result)