Steganography

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Light 2012-5-26

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Hey guys,

I met some problems in encrypting information hidden in an image. So I have two images: one with a white font and black text, and the other could be any image (the 2 images have the same size). First, I have to replace the least significant bit of the "red" color of the image with the information contained in the "textimage". Then, extract the part in the "red" color of the resulting image which correspond to the encrypted information.

Second, I have to use an encryption key that consists of a sequence of 1, 2 and 3, corresponding to the color planes on which information will be coded, i.e. if the key is 231321, the first pixel of the image "imagedetexte.bmp" will be encoded in level 2 (ie "green"), the second pixel is encoded in the plane 3 (ie "blue"), the third in a plan, the fourth in the plane 3, the fifth in the plane 2, the sixth in plan 1.

Also, the program will incorporate a Graphic User Interface.

To sum up:

       1- The program asks if the user wants to encrypt or decrypt.
       2- Depending on the user's response, it asks the names of image files to encrypt or decrypt.
       3- Ask for the encryption key in the form of a series of 1s, 2s and 3s (in the case of encryption) or      in the form of coefficients of a polynomial (in the case of decryption).
       4- display the result (resulting image or coded key).

Thanks a lot.

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Walter Roberson 2012-5-26

You forgot to ask a MATLAB question ?

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回答（3 个）

Image Analyst 2012-5-26

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What does "one with a white font and black text" mean? Text appears in a font, so are your letters and words black, or are they white? You can' t have it both ways unless you have some letters black and some letters white or have large letters and have a pattern, like a spotted pattern on very big letters.

For #1, you might use questdlg(). For #2 you might use uigetfile() or dir(). For #3, you might use inputdlg(). For #4 you might use imshow(), or image().

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Light 2012-5-27

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i mean a picture like this one : http://i47.tinypic.com/b4jihy.jpg and the other picture could be anything

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Light 2012-5-31

Using the encryption key to decide which bit-plane to code the next bit into.

Walter Roberson 2012-5-31

Convert the key from a decimal to a vector such as [2 3 1 3 2 1]. Then to know which plane to use for the K'th bit, access TheyKey(1 + mod(K-1, length(TheKey))) . Use if/else or switch() on that value to trigger the appropriate code.

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Light 2012-5-30

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I really need your help please. Thank you.

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Image Analyst 2012-5-31

You won't be getting help from me. Like I said, I don't know your program and don't really know encryption that well either. It's never really been a need for me or my images and programs.

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