the data hider pseudo-randomly selects Np encrypted pixels that will be used to carry the parameters for data hiding.here,Np is a small positive integer,for example,Np=20.the other(N-Np) encrypted pixels are pseudo randomly permuted and divided into number of groups,each of which contains L pixels.here what is the permutation needed and the code used to divide?
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I thought I understood the title of your post, but I have to admit I did not really understand your question at all. But, maybe this will help a tiny bit. It randomizes the 4,096 blocks of size 8*8 that tile your 512*512 array.
% Pretend data A = rand(512);
% Random linear index to the blocks r = randperm(4096)';
% (i,j) subscripts instead of linear index [i,j] = ind2sub([64 64],r)
% Example of grabbing the 37th randomly found block whichBlock = 37; randomBlock = A(8*(i(whichBlock)-1)+(1:8),8*(j(whichBlock)-1)+(1:8))