Embedding Information in Grayscale Images
Marten van Dijk, F.M.J. Willems, Y Nx · 2015
Grayscale images can be represented as sequences of integer-valued symbols. If such a symbol has alphabet {0; 1; · · · ; 2B − 1} it could be represented by B binary digits. To embed information in these symbols, we are allowed to distort them. The distortion measure that we consider here is mean squared error. In this setup there is a so-called “rate-distortion function ” that tells us what the largest embedding rate is, given a certain distortion level. First we determine this rate-distortion function. Next we compare the performance of LSB modulation to this rate-distortion function. Then several embedding codes are proposed: (i) codes that only affect the LSB of a symbol, (ii) so-called ternary codes in which a symbol can be changed by at most one, and (iii) codes that process a pair of symbols each time. 1 System description