protect the rights of their owners
- Copyright identification
- User identification or fingerprinting
- Authenticity determination
- Automated monitoring
- Copy protection
조건
- 추가된 워터마크는 눈에 보이지 않아야 함
- 어떤 경우에서던지 제거할수 없이 강력하여야 함
- 저작자의 정보를 내장
- 내장된 디지털워터마크는 복잡해야 한다.
visible watermark
Invisible Watermark
깨지기 쉬운 워터마크
강력한 워터 마크
- compression, filtering cropping, rotation, resampling, additional watermark or noise
- A typical image watermarking system
DCT-based watermarking
Mark insertion
Setp1
: 2-D DCT of the image
Setp2
: Locate its K largest coefficients,
, by magnitude
Setp3
: Create a watermark by generating a K-element pseudo-random sequence of numbers,
, taken from a Gaussian distribution.
Setp4 :
Setp5
: Inverse DCT of the result from step 4
Mark extraction
Setp1
: 2-D DCT of the image
Setp2
: Extract the K DCT coefficients
otherwise : unmarked or different watermark
Setp3
:
Setp4 : Measure the similarity
Setp5