when i apply crop attack on watermarked image it give me this error( Error in ==> extraction at 18 green = X(:,:,2);) while i embedd a watermark in blue channel how can i solve this problem? how can i apply crop attack?

when i apply crop attack on watermarked image it give me this error( Error in ==> extraction at 18 green = X(:,:,2);) while i embedd a watermark in blue channel how can i solve this problem? how can i apply crop attack?

[B.k Sumedha]

Post the code what u have tried so far.

[shameen khan]

i am sending you our code in message

[B.k Sumedha]

Just cant u post the code here? So that it will be available for others too.

[shameen khan]

ok

[shameen khan]

extraction code

close all
clear all
load var;
tic
%Extraction Process
              X=imread('watermarkrgb.png');
               %  X=imrotate(X,90);
                  %X = imnoise(X,'salt & pepper',0.02);
                  % X = imnoise(X,'poisson');
               %    X = imnoise(X,'speckle',0.04);
               % X = imnoise(X,'gaussian',0,0.025);
     X=crop(X);
                  %  figure
                  %   imshow(X);

red = X(:,:,1);
green = X(:,:,2);
blue = X(:,:,3);
% figure
% imshow(red);
% figure
% imshow(green);
% figure
% imshow(blue);

%  X=crop(X);
%    X=imread('shrp2.png');
%   X=imread('blur2.png');

     %   X = medfilt2(X);
     %  X = medfilt2(X, [7 7]) ;
                 % X=imresize(X,[256,256]);

          blue=im2double(blue);

     [ca1,ch1,cv1,cd1] = dwt2(blue,'haar');
     [ca2,ch2,cv2,cd2] = dwt2(ca1,'haar');

[AW1,AW2,AW3,AW4 ] = Dividev2(ca2);
[u1,sW11,v1]=svd(AW1);
 [u2,sW22,v2]=svd(AW2);
 [u3,sW33,v3]=svd(AW3);
 [u4,sW44,v4]=svd(AW4);
 SW1=SU1*sW11*SV1';
 SW2=SU2*sW22*SV2';
 SW3=SU3*sW33*SV3';
 SW4=SU4*sW44*SV4';

   for i=1:x 
    for j=1:y
       P1(i,j)= (SW1(i,j) - St1(i,j) )/ 0.3 ;
    end 
   end
   for i=1:x 
    for j=1:y
       P2(i,j)= (SW2(i,j) - st2(i,j) )/ 0.3 ;
    end 
   end
   for i=1:x 
    for j=1:y
       P3(i,j)= (SW3(i,j) - st3(i,j) )/ 0.3 ;
    end 
   end
   for i=1:x 
    for j=1:y
       P4(i,j)= (SW4(i,j) - st4(i,j) )/ 0.3 ;
    end 
   end
  %  figure
  % imshow(P1);title('p1')
  % figure
  % imshow(P2);title('p2')
  % figure
  % imshow(P3);title('p3')
  % figure
  % imshow(P4);title('p4')
  P=Combine(P1,P3,P2,P4); % call combine function
  % figure
  % imshow(P)
  P=repermutV2(P); % rearrange the image.
  figure
  imshow(P);title('Extracted watermark');

%          E = uint8(255*W);   
        F = uint8(255*P);   

          t=toc

function for crop....
function [ crp ] = crop( A )
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
for i=1:430

      for j=1:430

          crp(i,j)=A(i,j); 

      end 

end

[shameen khan]

ARE YOU UNDERSTAND MY CODE?

[Jan]

No, I do not understand the code. Please insert it in the body of the question, not as a comment, and care for a proper formatting. Currently it cannot be read reliably.

[shameen khan]

ok

[Walter Roberson]

Duplicates http://uk.mathworks.com/matlabcentral/answers/219937-when-i-apply-crop-attack-on-watermarked-image-it-give-me-this-error-error-in-extraction-at-18-g