Digital watermarking method robust against local and global geometric distortions and projective transforms

• US 20050018871A1
• Filed: 10/02/2002
• Published: 01/27/2005
• Est. Priority Date: 10/04/2001
• Status: Active Grant

• Current Assignee: Universite de Geneve
• Original Assignee: Universite de Geneve
• Inventors: Pun, Thierry, Voloshynovskiy, Slava, Deguillaume, Frederic
• Granted Patent: US 7,664,288 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0042 Fragile watermarking, e.g. so as to detect tampering
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 1/0071 using multiple or alternating watermarks
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• CPC Class Codes: G06T 2201/0601 whereby calibration information is embedded in the watermark, e.g. a grid, a scale, a list of transformations
• CPC Class Codes: H04N 1/32149 Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/32352 Controlling detectability or arrangements to facilitate detection or retrieval of the embedded information, e.g. using markers for decoding, detection or retrieval operations H04N1/32149 and subgroups take precedence
• CPC Class Codes: H04N 2201/3236 Details of authentication information generation
• CPC Class Codes: H04N 2201/3281 Encryption; Ciphering
• CPC Class Codes: H04N 2201/3284 for error correction

Abstract

A method of digital watermarking which can resist against local geometrical distortions such as random bending attack, global geometrical distortions as well as projective transforms, but does not necessary require the recovering of global affine transform or even the repetition of the same watermark pattern. Further, the watermark can resist common global affine transformations such as rotation, scaling, and changes of aspect ratio, cropping as well as other types of operations such as filtering, lossy compression, printing/scanning or detection of watermark in front of video, web or photo camera or any imaging device.

Claims

1. A method for generating watermarked data Y based on given original data X, wherein a watermark W associated with the watermarked data Y, comprises a multi-bit informative watermark message and a reference watermark associated with a key, the method comprising the steps of:

(a) encoding the multi-bit message, and

(b) generating the watermark W as a function of the key, the encoded message, and the reference watermark,

whereby the reference watermark acts as a reference to assist in the estimation and recovering from local and global alterations of the image.

2. The method of claim 1, wherein the method further whereby the generated watermarked data Y is visually indistinguishable from the original data X.

3. The method as claimed in claim 1, wherein the multi-bit message and the reference watermark with the associated key are encoded using error correcting codes.

4. The method as claimed in claim 1, wherein the method further estimates channel state.

5. The method as claimed in claim 1, wherein the method further verifies reliability of the decoding.

6. The method as claimed in claim 1, wherein the method further synchronizes decoding of the error correction codes.

7. The method as claimed in claim 1, wherein the encoded reference watermark includes additional bits for checking reliability of associated watermark decoding.

8. The method as claimed in claim 1, wherein the function uses perceptual masking while adding the watermark W to the original data X in the coordinate of a transform domain.

9. The method as claimed in claim 1, wherein the watermark is repeated and locally pre-distorted in every block before combining it with the original data X thereby obtaining generated watermarked data Y that is visually indistinguishable from the original data X.

10. The method as claimed in claim 1, wherein the encoded informative and reference watermarks comprises a regular or irregular structure within the block.

11. The method as claimed in claim 1, wherein the informative and reference watermarks are used locally for the recovering from local non-linear geometrical alterations based on local autocorrelation function or local windowed magnitude spectrum of a predicted watermark.

12. The method as claimed in claim 1, wherein the informative and reference watermarks are locally symmetrical with respect to a key-dependent center of symmetry, achieving smaller perceptual impact, basic invariance with respect to 90 degrees rotations and flippings, and cropping and translation resynchronization based on the zero-phase condition of the Fourier transform.

13. The method as claimed in claim 1, wherein the reference watermark is used to recover from local non-linear geometrical alterations using template matching within a single local microblock of the unflipped watermark.

14. The method as claimed in claim 1 wherein the decoded reference watermark is used for estimation of watermark reliability within a block to be added or to be adaptively weighted for combination with the resulting block for enhancement of watermark-to-noise ratio in decoder of error correction codes and to exclude unreliable blocks or to reduce the impact of outliers on the decoding process.

15. The method as claimed in claim 1, wherein the original data X is video data, image data or digital cinema data.

16. The method as claimed in claim 1 applied to video data, wherein a plurality of watermarked video frames is generated.

17. The method as claimed in claim 1, wherein the function operates in spatial domain, Discrete Cosine Transform (DCT) domain, Discrete Fourier Transform (DFT) domain, or Wavelet domain, or another suitable transform domain, or some combination thereof.

18. A computer-readable medium encoded with a method for generating watermarked data Y based on given original data X, wherein a watermark W associated with the watermarked data Y, comprises a multi-bit informative watermark message and a reference watermark associated with a key, the method comprising the steps of:

(c) encoding the multi-bit message, and

(d) generating the watermark W as a function of the key, the encoded message, and the reference watermark,

whereby the reference watermark acts as a reference to assist in the estimation and recovering from local and global alterations of the image.