Image steganography in matlab:Retrieve hidden Image

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Jessica
Jessica am 17 Apr. 2014
Beantwortet: riyaz nadaf am 26 Jan. 2019
I am trying to retrieve the image hidden in another image. This is the code I have so far but it is not working correctly. Can anyone tell me what Im doing wrong?
I1 = imread('c:/df/img/Lena1.png');
I2=I1;
output_stream="";
data_size_s=""; %In bytes and as a string
%We read the size of the target from the stego image (first 16 bits)
k=1;
for i=1:rows(I2)
for j=1:columns(I2)
if (k<18) s=dec2bin(double(I2(i,j,1)),8); data_size_s=strcat(data_size_s,s(8)); k++; endif
if (k<18) s=dec2bin(double(I2(i,j,2)),8); data_size_s=strcat(data_size_s,s(8)); k++; endif
if (k<18) s=dec2bin(double(I2(i,j,3)),8); data_size_s=strcat(data_size_s,s(8)); k++; endif
end
end
%We pass the size of the target image from string to integer
target_rows=uint32(bin2dec(substr(data_size_s, 1,8)));
target_columns=uint32(bin2dec(substr(data_size_s,9,8)));
data_size_int=target_rows*target_columns; % Data Size in bytes as integer
%We read the output_stream from the stego image
total_data_size=(8*data_size_int)+16; % Total length of the output stream (header + target data)
k=1;
for i=1:rows(I2)
for j=1:columns(I2)
if (k<=(total_data_size)) s=dec2bin(double(I2(i,j,1)),8); output_stream=strcat(output_stream,s(8)); k++; endif
if (k<=(total_data_size)) s=dec2bin(double(I2(i,j,2)),8); output_stream=strcat(output_stream,s(8)); k++; endif
if (k<=(total_data_size)) s=dec2bin(double(I2(i,j,3)),8); output_stream=strcat(output_stream,s(8)); k++; endif
end
end
I3_rows=uint32(bin2dec(substr(output_stream,1,8)));
I3_columns=uint32(bin2dec(substr(output_stream,9,8)));
k=17;
I3=uint8(zeros(I3_rows,I3_columns,3));
% We create a empty crey-scale image with the dimensions of the target
total_data_size=(8*data_size_int)+16;
for i=1:I3_rows
for j=1:I3_columns
if (k<=total_data_size) I3(i,j,1)=uint8(bin2dec(substr(output_stream,k,8))); k=k+8; endif
if (k<=total_data_size) I3(i,j,2)=uint8(bin2dec(substr(output_stream,k,8))); k=k+8; endif
if (k<=total_data_size) I3(i,j,3)=uint8(bin2dec(substr(output_stream,k,8))); k=k+8; endif
end
end
%We show the hidden image.
imshow(I3);
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Jessica
Jessica am 17 Apr. 2014
because I am not getting the correct image as a result. This is the image I am receiving.
Walter Roberson
Walter Roberson am 17 Apr. 2014
There is nothing obviously wrong with that output. I probably would not have chosen to embed that particular image, but that's just me.

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Antworten (3)

Image Analyst
Image Analyst am 17 Apr. 2014
You need to go through the normal debugging process. We don't know your algorithm for hiding and recovering your image, and I don't really have time to learn it, as fascinating as it might be. We can fix an error message for you but we can't do complicated algorithm development.
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Walter Roberson
Walter Roberson am 18 Apr. 2014
Bearbeitet: Walter Roberson am 18 Apr. 2014
For what it's worth, I think you are probably putting the extracted information into the wrong place in the array. When you see exactly three fuzzy repeats of an image you should suspect that you have put three color planes horizontally next to each other instead of stacking them in the third dimension. Consider that if ColorMatrix is something by something by 3 then
reshape( permute(ColorMatrix, [1 3 2]), size(ColorMatrix) )
is going to have the right dimensions to look like a color matrix, but the data will be in the wrong order.
Image Analyst
Image Analyst am 18 Apr. 2014
Jessica, can you post both the original "cover" image, and the original "image to be hidden" and which you hope to recover/extract?

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Chris
Chris am 19 Apr. 2014
I think what you need to do is determine if the image is RGB or Grayscale and then enter a correct loop for processing either a RGB image or Grayscale image. I think the 17th bit in the output_stream will be the determining factor for you.
riyaz nadaf
riyaz nadaf am 26 Jan. 2019
i did this project. if you want matlab code contact
riyaznadaf034@gmail.com

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