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Image Watermarking

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.

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Image Watermarking

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  1. Image Watermarking Chu, Hsi-Cheng

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

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

  4. Watermarking Requirements • Imperceptibility • Robustness

  5. Correlation-Based Watermarking Techniques Iw(x,y) I(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}

  6. 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’

  7. Techniques for Transform Domains • DFT, DCT, DWT • More robust

  8. 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

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