# Random shuffle of image pixels/ Image scrambling

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marie lasz on 8 Sep 2020
Commented: marie lasz on 10 Sep 2020
hello,
I am applying arnold transform method on an image to scramble its pixels. And i am doing it successfully but the problem in this method is that first I have to binarize the image before applying this method and that is why I am getting binarized image in a result in inverse of arnold transform. So, my question is that is there any other method in which I scramble or shuffle pixels by setting a key value without binarizing the image? so that I would be able to revert the image back ?
thank you very much :-)

Sindar on 9 Sep 2020
You can use randperm to shuffle the indices randomly, then sort to get the indices for reversing it:
% load in an image included in Matlab
% get the size
imsize = size(corn_gray);
% display
imshow(corn_gray)
% create a randomly-shuffled list of linear indices 1:total pixels
idx_shuffle=randperm(numel(corn_gray));
% get the inverse (idx_shuffle(idx_unshuffle) = 1:total pixels)
[~,idx_unshuffle] = sort(idx_shuffle);
% put the indices into the same row-col shape as the image
idx_shuffle = reshape(idx_shuffle,imsize);
idx_unshuffle = reshape(idx_unshuffle,imsize);
% compute the shuffled image
corn_gray_shuffled = corn_gray(idx_shuffle);
% run an arbitrary transformation on it
corn_gray_shuffled = corn_gray_shuffled.^2;
% display the shuffled, transformed image
imshow(corn_gray_shuffled)
% unshuffle the transformed image
corn_gray_unshuffled = corn_gray_shuffled(idx_unshuffle);
% and display
imshow(corn_gray_unshuffled)

Sindar on 9 Sep 2020
rereading you question, I'm not sure if this will actually help directly. But, maybe it will give you some ideas, or help people brought here by the title
marie lasz on 10 Sep 2020
thanks for your response but I need a method which scrambles the image pixels with number of iterations and that method can also does an inverse transform to its original image.