how can we extract an invisible watermark from an watermarked image?

I'm currently doing a project in watermarking the encrypted shares of an RGB colour image to enhance the visual cryptography scheme. And i had inserted the invisible watermarks into it. Can u give me any idea how to extract those watermarks from the watermarked share?

Answer 1

[Image Analyst]

You'd have to know how they did it, or guess and get lucky. Invisible watermarks are inserted because they don't want you to know they are there. They often employ techniques that make it difficult to extract them or degrade them without exact knowledge of what was done to create them.

[Rajasekaran]

For the below code, i need the extraction procedure. Can you help me sir??

clear all; close all; clc; image1=imread('Google.jpg'); [ori_row,ori_col]=size(image1); host_length=ori_row*ori_col;

i=1; j=1; k=1;

wmimage=imread('android1.jpg'); [wm_row,wm_col] = size(wmimage); imshow(wmimage); title('Watermark image');

wm=dec2bin(wmimage); wm_length=wm_row*wm_col*8;

host=dec2bin(image1);

counter=0;

while i < host_length

        counter=counter+1;

        if counter > wm_length
            break;
        end

        host(i,8)=wm(j,k);
        k=k+1;

        if k>8
            k=1;
            j=j+1;
        end

        i=i+1;
end

    key1=wm_row;
    key2=wm_col;

im1=bin2dec(host); im1=reshape(im1,ori_row,ori_col); image1(1:ori_row,1:ori_col)=im1(1:ori_row,1:ori_col);

imwrite(image1,'wm.bmp'); imshow(image1);