Digital Watermarking: DCT and DWT-Based Embedding and Extraction Techniques

In the field of digital copyright protection, Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) are prevalent techniques for watermark embedding and extraction. DCT operates as a frequency-domain approach, typically implemented by converting image blocks into frequency coefficients using dct2() function in MATLAB or similar libraries. The watermark is embedded by modifying mid-frequency coefficients to balance visibility and robustness. DWT serves as a time-domain method that decomposes images into multiple frequency sub-bands (LL, LH, HL, HH) through wavelet decomposition functions like wavedec2(). Watermarks are strategically embedded in selected sub-bands, often the LH and HL bands, to withstand various attacks. These techniques can be effectively applied to digital copyright protection systems to safeguard digital media against piracy and unauthorized use. Furthermore, digital copyright protection can be enhanced by incorporating encryption techniques for secure watermark generation and robust detection algorithms that utilize correlation-based matching or machine learning approaches for reliable watermark extraction under noisy conditions.