Substitution of LSB of RGB component by other bits

I have extracted audio bits in a variable. These needs to be substituted in RGB components at various pixel positions. I have the pixel positions and 8 bit value of each RGB at that position. Want to know how last 2 LSB of, say, RED component can be replaced by first 2 bits of audio data.

Kindly share if a link is already available for same.

[sangeeta]

Let value of R component at position(x1,y1) is [10010000].

Audio data is [11010101......]

2 LSB of R = [00]

These needs to be replaced by first two bits of audio data[11]

So finally value of R at (x1,y1) becomes [10010011].

Is there any substitution/replace method available in Matlab? Kindly reply soon.

[Vinsa]

i am doing steganography on line based cubism images..how this adaptive LSB substitution for smooth areas and two component lsb substitution for edge areas can be done? kindly give me reply.

Answer 1

[Walter Roberson]

bitset()

[sangeeta]

Thanks Walter.

Kindly look into this:

r is red component value, say, 11000010

bits is bits to be replaced, last three.

firstAudio contain the three bits of audio data, say,001

 if true
    bits = 1:3;
     a = dec2bin(bitset(bin2dec(r),bits,firstAudio)); 
  end

I get:

    a = 11000010

        11000000

        11000110

I want the replacement in the same byte, instead of 3 outputs, that is 'a' should be 11000001

[Walter Roberson]

Use 3 bitset() calls.

Or if you are already using dec2bin storage for both r and firstAudio, then with no loops,

a = r;
a(end-2:end) = firstAudio(end-2:end);