PSNR value is very high around 300. Am I doing it correct?

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Jayashree Walimbe 2019-7-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/472931-psnr-value-is-very-high-around-300-am-i-doing-it-correct

评论： Punitha Viswanathan 2022-4-5

I have following code which gives me PSNR 300 which seems unrealisic. If I use DWT first level, it shows correct PSNR around 40-50dB, But 2-level DWT gives PSNR 300. Is the code incorrect.

Thank you.

------------------------------------------------------------------------------------

clear all;

close all;

clc;

format long

addpath(genpath(cd))

%% AES ENCRYPTION

ssi;

plaintext=['S' 'i' 'n' 'h' 'g' 'a' 'd' ' ' 'C' 'o' 'l' 'l' 'e' 'g' 'e' ' '];

fprintf('PLAIN TEXT :%s\n', plaintext);

plain=reshape(plaintext,4,4);

plain = abs (plain);

key = ['1' '2' '3' '4' '5' '6' '7' '8' '9' '1' '2' '3' '4' '5' '6' '7'];

key=abs(key);

w = key_expansion (key, s_box, rcon);

ciphertext = cipher (plain, w, s_box, poly_mat,ind_matleft);

ciphertext = reshape(ciphertext,1,16);

fprintf('CIPHER TEXT :%s\n',ciphertext);

pause(.2)

save ciphertext ciphertext

%% DWT DECOMPOSITION

I=imread('chest_xray.jpg');

% I=im2bw(I);

figure,imshow(I);title('COVER IMAGE');pause(.5)

% RESIZE

I=imresize(I,[512,512]);

[m,n,z]=size(I);

% m:Rows, n:Coloumns, Z:Channel

if z==3%i.e.R,G,B [it is color image]

I=rgb2gray(I);

figure,imshow(I);title('GRAY IMAGE');pause(.5)

end

% DWT DECOMPOSITION

Wname='db01';% Wavlete family --Daubechis Wavlet

% Decompose Image

[CA,CH,CV,CD]=dwt2(I,Wname);

%%https://in.mathworks.com/matlabcentral/answers/384533-how-to-calculate-discrete-wavelet-transform-on-an-image-with-levels-2-4-and-6-using-dwt2-function-in

[cDA,cDH,cDV,cDD] = dwt2(CD,Wname);

CD=cDD;

load ciphertext

CD=im2bw(CD);

CD=mat2gray(CD);

CD(1:16,1)=ciphertext;

CD=repmat(CD,2,2);

% CA:Approximate Coeff;

% DETAIL COEFF

% CH:Horizontal coeff

% CV:Vertical Coeff

% CD Diagonal Coeff