Method and device for inserting a watermarking signal in an image

• US 6,718,045 B2
• Filed: 01/09/2001
• Issued: 04/06/2004
• Est. Priority Date: 01/11/2000
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nguyen, Eric, Donescu, Ioana
• Primary Examiner(s): Patel, Jayanti K.
• Assistant Examiner(s): Tabatabai, Abolfazl
• Application Number:
  US09/756,136
• Publication Number:
  US 20010031064A1
• Time in Patent Office: 1,183 Days
• Field of Search: 382/100, 382/232, 382/240, 380/51, 380/54, 380/201, 380/210, 380/252, 380/287, 370/522, 370/523, 370/524, 370/525, 370/526, 370/527, 370/528, 370/529, 283/72, 283/73, 283/74, 283/75, 283/76, 283/77, 283/78, 283/79, 283/80, 283/81, 283/85, 283/93, 283/113, 283/901, 283/902
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: H04N 1/3217 using wavelet transforms
• CPC Class Codes: H04N 1/32187 with selective or adaptive application of the additional information, e.g. in selected frequency coefficients
• CPC Class Codes: H04N 19/10 using adaptive coding
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/94 Vector quantisation
• CPC Class Codes: H04N 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes

Abstract

A method of inserting a watermarking signal (w) in a set (X) of coefficients (X_i) representing a digital image (I), in which at least one subset of coefficients is modified by said watermarking signal (w), comprises, for each representative coefficient (X_i) to be modified, a step of determining a neighborhood (V(X_i)) of the representative coefficient (X_i) to be modified, in the image (I); a step of selecting a neighborhood (V_sim^d) in a dictionary of neighborhoods representing coefficients representing the image (I), according to a predetermined criterion of similarity with the neighborhood (V(X_i)) of the representative coefficient (X_i) under consideration; and a step of modifying the representative coefficient (X_i) as a function of the watermarking signal (w) and a predetermined masking data item (M(V_sim^d)) representing the masking effect on a watermarking signal, of the neighborhood (V_sim^d) selected in the dictionary.

Claims

1. Method of inserting a watermarking signal (w) in a set (X) of coefficients (X_i) representing a digital image (I), in which at least one subset of coefficients is modified by said watermarking signal (w), said method comprising, for each representative coefficient (X_i) to be modified, the following steps:

determining a neighbourhood (V(X_i)) of said representative coefficient (X_i) to be modified, in the image (I);

selecting a neighbourhood (V_sim^d) in a dictionary of neighbourhoods representing coefficients representing said image (I), according to a predetermined criterion of similarity with said neighbourhood (V(X_i)) of said representative coefficient (X_i); and

modifying said representative coefficient (X_i) as a function of the watermarking signal (w) and a predetermined masking data item (M(V_sim^d)) representing the masking effect on a watermarking signal of said neighbourhood (V_sim^d) selected from the dictionary.

2. Method of inserting a watermarking signal according to claim 1, comprising the following prior steps:

creating said dictionary of neighbourhoods (V^d) representing the coefficients representing said image (I);

generating, for each neighbourhood (V^d) in said dictionary, a masking data item (M(V^d)) representing the masking effect of the neighbourhood on a watermarking signal.

3. Method of inserting a watermarking signal according to claim 2, wherein said representative coefficients (X_i) are spatio-frequency coefficients obtained by a spatio-frequency transformation (T) of said image (I).

4. Method of inserting a watermarking signal according to claim 3, wherein the step of creating said dictionary comprises the following steps:

(A)—

setting up a database of images, referred to as learning images, characteristic of a type of image to be watermarked;

(B)—

for each learning image;

(b1)—

selecting the coefficients representing the learning image under consideration, obtained by the transformation (T), belonging to at least one sub-band (SB) of the image under consideration; and

,

(b2)—

for each coefficient (X_i) representing said sub-band (SB);

determining a neighbourhood (V(X_i)) of the representative coefficient (X_i) under consideration in the learning image under consideration;

calculating an energy (E[V(X_i)]) associated with the neighbourhood (V(X_i)) of the coefficient under consideration;

storing the neighbourhood (V(X_i)) in a database, referred to as the learning vector base, if the calculated energy (E[V(X_i)]) of the neighbourhood is greater than a predetermined threshold (E0);

(C) applying a predetermined processing to the vectors of the learning vector base so as to calculate a smaller number of vectors, the said calculated vectors constituting the dictionary of neighbourhoods.

5. Method of inserting a watermarking signal according to claim 4, wherein said dictionary of neighbourhoods is obtained by vector quantisation of the learning vector base.

6. Method of inserting a watermarking signal according to any one of claims 3 to 5, wherein the step of generating, for each neighbourhood (V^d) of said dictionary, a masking data item (M(V^d)) representing the masking effect of the neighbourhood on a watermarking signal, comprises the following steps, for each neighbourhood (V^d) of said dictionary:

applying the inverse of said transform (T<sup>−

1</sup>) to said neighbourhood (V^d) so as to obtain the corresponding image (I_d);

modifying all the coefficients (V_i^d) of said neighbourhood (V^d) in successive stages, applying a modification value (M) varying according to an incrementation pitch (p) at each stage, and at each modification stage;

applying the inverse transform (T<sup>−

1</sup>) to said modified neighbourhood (V*^d) so as to obtain the corresponding modified image (I′

_d);

effecting a perceptual measurement (MP(I_d, I*_d)) intended to evaluate a visual difference between the two images;

comparing the result of the perceptual measurement with a predetermined threshold (JND);

storing said modification value (M) when the result of the perceptual measurement reaches the predetermined threshold (JND), the modification value (M) stored constituting the masking data item (M(V^d)) associated with the neighbourhood (V^d) of the dictionary.

7. Method of inserting a watermarking signal according to claim 6, wherein the modification of each of the coefficients (V_i^d) of said neighbourhood (V^d) is carried out according to the following formula:

8. Method of inserting a watermarking signal according to claim 7, wherein the modification of all the coefficients (V_i^d) of said neighbourhood (V^d) in successive stages is carried out according to the following formula:

9. Method of inserting a watermarking signal according to any one of claims 1-5 wherein the step of modifying said representative coefficient (X_i) as a function of the watermarking signal (w) and a predetermined masking data item (M(V_sim^d)) representing the masking effect, is effected by modulation in accordance with the following formula:

10. Method of inserting a watermarking signal according to claim 9, wherein said modulation amplitudes A_i are used in the choice of a subset of representative coefficients to be modulated.

11. Method of inserting a watermarking signal according to claim 2, wherein said masking data item (M(V^d)) generated for each neighbourhood (V^d) of said dictionary is calculated using a mathematical model.

12. Method of inserting a watermarking signal according to any one of claims 3 to 5, in which said transformation (T) is a discrete wavelet transformation (DWT), wherein a neighbourhood of any representative coefficient X_i of said image is determined as being the oriented tree of wavelet coefficients which is in the neighbourhood of said representative coefficient X_i, the root of said tree consisting of the coefficient, referred to as the parent coefficient, which corresponds to the highest decomposition level in the tree.

13. Method of inserting a watermarking signal according to any one of claims 1-5, wherein the watermarking signal (w) is a predetermined pseudo-random sequence with a null mean.

16. Computer, comprising means adapted to implement a method of inserting a watermarking signal according to any one of claims 1-5, 14, or 15.

18. Digital signal processing apparatus, comprising means adapted to implement an insertion method according to any one of claims 1-5, 14, or 15.

20. Digital printer, comprising means adapted to implement an insertion method according to any one of claims 1-5, 14, or 15.

22. Digital photographic apparatus, comprising means adapted to implement an insertion method according to any one of claims 1-5, 14, or 15.

24. Digital camera, comprising means adapted to implement an insertion method according to any one of claims 1-5, 14, or 15.

26. Scanner, comprising means adapted to implement an insertion method according to any one of claims 1-5, 14, or 15.

14. Device for inserting a watermarking signal (w) in a set (X) of coefficients (X_i) representing a digital image (I), in which at least one subset of coefficients is modified by said watermarking signal (w), said device comprising, for each representative coefficient (X_i) to be modified:

means of determining a neighbourhood (V(X_i)) of said representative coefficient (X_i) to be modified, in the image (I);

means of selecting a neighbourhood (V_sim^d) in a dictionary of neighbourhoods representing coefficients representing said image (I), according to a predetermined criterion of similarity with said neighbourhood (V(X_i)) of the representative coefficient (X_i); and

means of modifying said representative coefficient (X_i) as a function of the watermarking signal (w) and a predetermined masking data item (M(V_sim^d)) representing the masking effect on a watermarking signal, of said neighbourhood (V_sim^d) selected from the dictionary.

15. Device for inserting a watermarking signal according to claim 14, comprising:

means of creating said dictionary of neighbourhoods (V^d) representing the coefficients representing said image (I);

means of generating, for each neighbourhood (V^d) of said dictionary, a masking data item (M(V^d)) representing the effect of masking the neighbourhood on a watermarking signal.

17. Computer, comprising a device for inserting a watermarking signal according to any one of claims 14 to 15.

19. Digital image processing apparatus, comprising an insertion device according to any one of claims 14 to 15.

21. Digital printer, comprising an insertion device according to any one of claims 14 to 15.

23. Digital photographic apparatus, comprising an insertion device according to any one of claims 14 to 15.

25. Digital camera, comprising an insertion device according to any one of claims 14 to 15.

27. Scanner, comprising an insertion device according to any one of claims 14 to 15.