title: Steganography using the DCT
body: <p>Broadly speaking there are 4 steps involved in embedding a message using DCT:</p>
  
  <ol>
  <li>Divide the image into 8x8 blocks</li>
  <li>Transform each block using DCT mathematical operations</li>
  <li>Quantitize each DCT block (lossy compression)</li>
  <li>Embed the message bits from the quantitized coefficients (avoid 0, 1, -1, and the AC)</li>
  </ol>
  
  <p>Thats ok, but I am not sure how to extract the data back out. Are you suppose to go through steps 1-3 to quantitize each block in order to extract the LSB of each coefficient?</p>
  
  <p>If that's the case, would you not be losing (possible the embedded data) data because it is a lossy technique? </p>
  
  <p>Also when I tried to quantitize each block, I am left with the same coefficients from the previous image (as in the LSB change had no effect) ??</p>
  
  <p>Could someone enlighten me on this problem?</p>
  
  <p>Thanks</p>