Pixel Shuffling and inverse shuffling

Question

Renjith V Ravi 2017-2-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323409-pixel-shuffling-and-inverse-shuffling

评论： marie lasz 2020-9-17

I have tried to shuffle the image using tinkerbell map and Henon Map and obtained the output.But I cant do the inverse shuffling processes.The code is given below

clear all
clc
g=imread('cameraman.tif');
% g=double(g)/255;
subplot(231)
imshow(g)
original=g;
[m,n]=size(g);
mo=m;
num = 12;
K=10.^10;
% K=19;
%....................Shuffling.......................
 disp('........................Started Shuffling.....................')
%Tinkerbell shuffling
a=0.3;b=0.6000;c=2.0;d=0.27;
for k= 1:num
for i=1:m
    for j=1:n
      r = mod([round(abs((i^2)-(j^2)+(a*i)+(b*j))),round(abs((2*i*j)+(c*i)+(d*j)))], [m,n]);
%     r = mod([(i+j),(j+K*sin(((i+1)*n)/2*pi))],mo);
%     r = [((i-1)+(K*sin(j-1))),((j-1)+i)];
%     r = uint8(r);
      ggg(i,j)=g(r(1)+1,r(2)+1);
%       ggg(i,j)=g(r(1),r(2));
      end
  end
    g=ggg;
  end
   subplot(232)
   x=ggg;
   imshow(ggg,[]);
   title('Tinkerbell shuffled')
   %henon Shuffling
  [m,n]=size(x);
   a = 1.4;b=0.3;
  % num_iter=input('Enter the round for Arnold shuffling');
  num_iter = 5;
  %     a=1.4;
  %     b=0.3;
   for k=1:num_iter
  for i=1:m
      for j=1:m
          r = mod([round(abs(1-(a*(i^2))+j)),round(abs(b*i))],[m n]);
           xxx(i,j)=x(r(1)+1,r(2)+1);
       end
   end
    x=xxx;
   end
   subplot(233)
   imshow(xxx);
   title('henon Shuffled Image')
   save xxx x
   disp('........................Shuffling process completed succesfully.....................')
   %...................Inverse Shufling.............................
   disp('........................Started Inverse Shuffling.....................')
   %Henon Inverse Shuffling
   for k=1:num_iter
  for i=1:m
      for j=1:n
  r = mod([round(abs(1-(a*(i^2))+j)),round(abs(b*i))],[m n]);
  x1(r(1)+1,r(2)+1)=xxx(i,j);
       end
   end
    xxx=x1;
   end
   subplot(234)
   imshow(x1);
   title('henon Inverse Shuffled')
%Tinkerbell inverse shuffling
 a=0.3;b=0.6000;c=2.0;d=0.27;
for k=1:num
for i=1:m
    for j=1:n
         r = mod([round(abs((i^2)-(j^2)+(a*i)+(b*j))),round(abs((2*i*j)+(c*i)+(d*j)))], [m,n]);
          g1(r(1)+1,r(2)+1)=x1(i,j); 
       end
   end
    xxx=g1;
  end
   subplot(224)
   imshow(g1)
   title('Tinkerbell_inverse_shuffled')
    disp('........................Inverse Shuffling process completed succesfully.....................')
   psnr = psnr(g1,original)
   ssim=ssim(g1,original)

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marie lasz 2020-9-17

May I know that why you shuffled the image two times , I mean with two methods?

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Answer 1

Walter Roberson 2017-2-5

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323409-pixel-shuffling-and-inverse-shuffling#answer_253386

编辑：Walter Roberson 2017-2-5

在 MATLAB Online 中打开

Suppose your shuffled image is S. Then

temp = reshape(1:numel(S), size(S));

temp will be an array of linear indices -- temp(k) will be k.

Now apply your forward shuffling routine to temp, generating temp_mapped . Each value in temp_mapped will appear only once, and the location temp_mapped == k is the place that the shuffle maps pixel #k to. So you can undo it:

unshuffled = zeros(size(S), class(S));
unshuffled(temp_map) = S;

and you can cross-check by shuffling this and checking that you get out S.

By the way, once you have temp_mapped, you can use it to do all future shuffling,

S1 = unsuffled(temp_map);
S2 = S1(temp_map);
S3 = S2(temp_map);

and S3 would be unsuffled shuffled 3 times, without having to do any further computation of indices.

9 个评论
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Renjith V Ravi 2017-2-5

编辑：Renjith V Ravi 2017-2-5

在 MATLAB Online 中打开

Anyway, I went for single shuffling,instead of double for easiness.But,I couldn't get the original image after unshuffling.The code is given below

clear all
close all
clc
num=1;
G = imread('cameraman.tif');
[m,n]=size(G);
g = reshape( 1:numel(G), size(G) );
a=0.3;b=0.6000;c=2.0;d=0.27;
%Tinkerbell shuffling
for k= 1:num
for i=1:m
  for j=1:n
    r = mod([round(abs((i^2)-(j^2)+(a*i)+(b*j))),round(abs((2*i*j)+(c*i)+(d*j)))], [m,n]);
    ggg(i,j)=g(r(1)+1,r(2)+1);
    end
end
  g=ggg;
end
GGG = G(ggg);
    disp('shuffling completed')
%inverse shuffling
% unshuffled_ggg = zeros(size(G), class(G));
% unshuffled_ggg(ggg) = GGG;
a=0.3;b=0.6000;c=2.0;d=0.27;
for k=1:num
for i=1:m
    for j=1:n
         r = mod([round(abs((i^2)-(j^2)+(a*i)+(b*j))),round(abs((2*i*j)+(c*i)+(d*j)))], [m,n]);
          g1(r(1)+1,r(2)+1)=GGG(i,j); 
       end
   end
    unshuffled_ggg=g1;
  end
   unshuffled_ggg = zeros(size(G), class(G));
   unshuffled_ggg(ggg) = GGG;
imshowpair(G,unshuffled_ggg, 'montage'); %better that subplot

RAVI KUMAR 2018-3-15

Are you able to get the correct inverse shuffling?

juveria fatima 2018-3-26

在 MATLAB Online 中打开

am not getting the inverse

its showing error

Index exceeds matrix dimensions.

Error in rough (line 62)

x1(r(1)+1,r(2)+1)=xxx(i,j);

pleae help me to resolve

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Answer 2

Hyelda Kefas 2018-5-7

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323409-pixel-shuffling-and-inverse-shuffling#answer_319011

编辑：Walter Roberson 2018-5-7

在 MATLAB Online 中打开

I was able to do the INVERSE SHUFFLE for the Henon map. I don't know whether it is perfectly correct or not. Let's rub minds and get the perfect solution for you. Thanks

clear all
clc
g=imread('cameraman.tif');
g = imresize(g, [256 256]);
g=g(:,:,1);
subplot(2,2,1)
imshow(g,[])
title('Original Image')
   %HENON SHUFFLING
    [m,n]=size(g);
     a = 3;
     b = 3;
    num_iter = 1;
     for k=1:num_iter
    for i=1:m
        for j=1:n
            r = mod([round(abs(1-(a*(i^2))+j)),round(abs(b*i))],[m n]);
             x(i,j)=g(r(1)+1,r(2)+1);
         end
     end
      g=x;
     end
     subplot(2,2,2)
     imshow(x,[]);
     title('Henon Shuffled Image')
     %HENON INVERSE SHUFFLING
     [m,n]=size(x);
     a = 3;
     b = 3;
    num_iter = 1;
     for k=1:num_iter
    for i=1:m
        for j=1:n
    r1 = mod([round(abs(1-(a*(i^2))+j)),round(abs(b*i))],[m n]);
    x1(r1(1)+1,r1(2)+1)=x(i,j);
    %x(i,j)=x1(r(1)+1,r(2)+1);
         end
     end
      x=x1;
     end
     subplot(2,2,3)
     imshow(x1,[]);
     title('Henon Inverse Shuffled')   
     set(gcf,'units','normalized','outerposition',[0 0 1 1]);