Bi-orthogonal 7/9 Three-Level Wavelet Decomposition for Image Watermarking

After applying bi-orthogonal 7/9 three-level wavelet decomposition to the original image, watermark coefficients can be embedded into the second-level horizontal, vertical, diagonal components and the third-level diagonal subbands. This implementation typically involves using wavelet decomposition functions to separate image frequencies into multiple resolution levels, where the selected mid-frequency subbands provide optimal balance between visibility and robustness. The watermark embedding process modifies specific wavelet coefficients using additive or multiplicative rules while maintaining perceptual transparency. During inverse wavelet reconstruction, the watermarked image preserves essential visual characteristics of the original while hiding watermark information across different frequency components. This multi-subband distribution strategy significantly enhances watermark security against attacks and improves stability through frequency-domain redundancy. Key implementation considerations include proper coefficient selection thresholds, quantization step sizing, and handling boundary conditions during wavelet reconstruction.