Image Watermarking Chu, Hsi-Cheng

What is Image Watermarking? A technique to to embed some secret information in the image + image watermarked image watermark

What is Image Watermarking? The embedded information can be extracted when needed Detector watermarked image watermark

Watermarking Requirements Imperceptibility Robustness

Correlation-Based Watermarking Techniques I(x,y) Iw(x,y) ± Multiply by gain factor k seed Iw(x,y)=I(x,y)± k·W(x,y) W(x,y): Pseudorandom Pattern {-1,1}

Watermark Detection RIw(x,y)W(x,y) > T → W(x,y) detected < T → No W(x,y) detected If detected, RIw(x,y)W(x,y) > 0 → bit ‘1’ or RIw(x,y)W(x,y) < 0 → bit ‘0’

Techniques for Transform Domains DFT, DCT, DWT More robust

Conclusions The process of watermarking is a tradeoff among image quality, watermark capacity, robustness Techniques for frequency domains are superior to techniques for the spatial domain