How can I unscramble a scrambled image?
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Hi! I'm just a beginner. I scrambled an image using the following source.
if true
---------- scramble an 512*512 image as 8 by 8 blocks---------------------
I = imread('lena_org.bmp');
row = size(I, 1) / 64;
col = size(I, 2) / 64;
I_scramble = mat2cell(I, ones(1, row) * 64, ones(1, col) * 64, size(I, 3));
I_scramble = cell2mat(reshape(I_scramble(randperm(row * col)), row, col));
imshow(I_scramble);
---------------------------------------------------------------------------
end
Anyone knows how to unscramble the image as it was? I spent a lot of time solving the problem, but I am going around in circles. Thanks a lot for your help in advance!
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采纳的回答
harjeet singh
2015-12-19
编辑:Image Analyst
2022-6-10
I = imread('Lena512.bmp');
row = size(I, 1) / 64;
col = size(I, 2) / 64;
I_scramble = mat2cell(I, ones(1, row) * 64, ones(1, col) * 64, size(I, 3));
a=randperm(row * col);
I_scramble = cell2mat(reshape(I_scramble(a), row, col));
figure(1)
imshow(I_scramble);
drawnow
b=1:length(a);
com=[a' b'];
com=sortrows(com,1);
I_scramble = mat2cell(I_scramble, ones(1, row) * 64, ones(1, col) * 64, size(I, 3));
I_scramble = cell2mat(reshape(I_scramble(com(:,2)), row, col));
figure(2)
imshow(I_scramble);
drawnow
3 个评论
Image Analyst
2022-6-10
@BHAGYASHREE HEGDE the 64 is so that you get exactly 8 blocks vertically and horizontally.
numBlocks = 512/64
更多回答(1 个)
Image Analyst
2015-12-19
See my attached demo that scrambles an image element by element. You could adapt it to scramble a cell array element by element also.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/172376/image.jpeg)
4 个评论
Image Analyst
2018-11-25
See code altered to work on a gray scale image.
% Demo to use randperm() to scramble the pixel locations in a gray scale image, then undo the scrambling to obtain the original image again.
clc;
clearvars;
close all;
workspace;
fontSize = 16;
% Read in a gray scale demo image.
folder = fileparts(which('cameraman.tif')); % Determine where demo folder is (works with all versions).
baseFileName = 'cameraman.tif';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
% Didn't find it there. Check the search path for it.
fullFileName = baseFileName; % No path this time.
if ~exist(fullFileName, 'file')
% Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist.', fullFileName);
uiwait(warndlg(errorMessage));
return;
end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image. numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
grayImage = rgb2gray(grayImage); % Convert to gray level.
end
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage);
title('Original Gray Scale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
% Get the order to scramble them in
scrambleOrder = randperm(rows*columns);
% Scramble according to the scrambling order.
grayImage = grayImage(scrambleOrder);
% Reshape into a 2D image
scrambledImage = reshape(grayImage, [rows, columns]);
% Display the scrambled gray scale image.
subplot(2, 2, 2);
imshow(scrambledImage);
title('Scrambled Gray Scale Image', 'FontSize', fontSize);
% Recover the image, knowing the sort order
recoverOrder = zeros([rows*columns], 2);
recoverOrder(:, 1) = 1 : (rows*columns);
recoverOrder(:, 2) = scrambleOrder;
% Sort this to find out where each scrambled location needs to be sent to.
newOrder = sortrows(recoverOrder, 2);
% Extract just column 1, which is the order we need.
newOrder = newOrder(:,1);
% Unscramble according to the recoverOrder order.
grayImage = grayImage(newOrder);
% Reshape into a 2D image
scrambledImage = reshape(grayImage, [rows, columns]);
% Display the original gray scale image.
subplot(2, 2, 3);
imshow(scrambledImage);
title('Unscrambled Gray Scale Image', 'FontSize', fontSize);
![0000 Screenshot.png](https://www.mathworks.com/matlabcentral/answers/uploaded_files/196707/0000%20Screenshot.png)
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