Combining Digital Watermarking and Fingerprinting Techniques to Identify Copyrights for Color Images

Algorithm 3

Watermark retrieval.

Input:   A suspect color image S (𝑁×𝑁).

Output:   A fingerprint (watermarked) image FP′ (𝑁/4×𝑁/4).

Apply DWT to the R and B channels of 𝑆 and obtain the embedding blocks 𝐼₁--𝐼₄

For each coefficient 𝑐 of the 𝐼₁--𝐼₄ blocks

    Obtain w according to (9)

End For

Assemble every watermark bit w to restore the fingerprint image FP′