Embedding and detecting a watermark in images

• US 6,700,994 B2
• Filed: 01/19/2001
• Issued: 03/02/2004
• Est. Priority Date: 01/09/1998
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Rongen, Peter M. J., Van Overveld, Cornelis W. A. M., Maes, Maurice J. J. J-B.
• Primary Examiner(s): Patel, Jayanti K.
• Assistant Examiner(s): Choobin, Barry
• Application Number:
  US09/765,681
• Publication Number:
  US 20010002931A1
• Time in Patent Office: 1,138 Days
• Field of Search: 382/100, 382/254, 382/105, 382/215, 713/200, 713/176, 345/614, 345/21, 702/191, 348/14.12, 348/14.13, 380/218, 380/54.22, 380/22, 380/21, 380/230, 380/246, 707/104.1, D14/160, 369/13.02, 369/13.07, 369/13.14
• US Class Current: 382/100
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0063 in relation to collusion attacks, e.g. collusion attack resistant
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32219 involving changing the position of selected pixels, e.g. word shifting, or involving modulating the size of image components, e.g. of characters H04N1/32224 takes precedence
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection

Abstract

A digital image signal is watermarked by locally changing geometric features of the image. The watermark consists of a pseudo-random, dense subset of image pixels, e.g., a pattern of lines (20). A number of significant image pixels (21,22,23), i.e., pixels which give the highest response to a predetermined processing operation, is determined and then moved (24) to the vicinity (δ) of the line pattern. As a result of this “warping”, the majority of significant image pixels (21,22) is eventually located within the vicinity of the line pattern. At the receiver end, the most significant pixels of an input image are again determined. The image is a watermarked image if a statistically high percentage lies within the vicinity of the line pattern.

Claims

1. An image signal representing an image with an embedded watermark in the form of a predetermined pattern of pixels, wherein the average distance of a given number of most significant image pixels to the watermark pattern is significantly smaller than the average distance of all image pixels to the watermark pattern.

2. The image signal as claimed in claim 1, wherein the number of most significant pixels having a distance to the watermark pattern which is smaller than a predetermined threshold is a significantly high percentage of the number of most significant image pixels.

3. A record carrier having an image signal recorded thereon, said image signal representing an image with an embedded watermark in the form of a predetermined pattern of pixels, wherein the average distance of a given number of most significant image pixels to the watermark pattern is significantly smaller than the average distance of all image pixels to the watermark pattern.

4. The record carrier as claimed in claim 3, wherein the number of most significant pixels having a distance to the watermark pattern which is smaller than a predetermined threshold is a significantly high percentage of the number of most significant image pixels.

5. The record carrier as claimed in claim 3, wherein said record carrier is magnetic video tape.

6. The record carrier as claimed in claim 3, wherein said record carrier is an optical disk.

7. A method of embedding a watermark in an image and for transmitting said watermarked image, comprising the steps:

embedding a watermark in an image, including the sub-steps;

identifying a given number of most significant image pixels;

defining a watermark in the form of a pattern of pixels; and

locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern;

generating a transmission signal from said locally warped image; and

applying said transmission signal to a transmission medium.

8. The method as claimed in claim 7, wherein said transmission medium is airwaves, said generating step comprises modulating said locally warped image onto a carrier wave, and said applying step comprises transmitting said modulated carrier wave over said airwaves.

9. The method as claimed in claim 7, wherein said transmission medium is the Internet.

10. A method for displaying a watermarked image signal retrieved from a transmission medium, wherein said watermarked image signal has been generated by identifying a given number of most significant image pixels, defining a watermark in the form of a pattern of pixels, and locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern, said method comprising the steps:

retrieving a transmission signal from said transmission medium;

converting said transmission signal into an image signal;

detecting a watermark in said image signal, including the sub-steps;

identifying a given number of most significant image pixels;

determining the distances of said most significant image pixels to the watermark pattern; and

generating a detection signal indicating that said predetermined watermark is embedded in the suspect image, if the average distance of said most significant pixels to the watermark pattern is significantly smaller than the average distance of all image pixels to the watermark pattern; and

selectively displaying said image signal in dependence on said detection signal.

11. An apparatus for embedding a watermark in an image and for transmitting and receiving said watermarked image, comprising:

an arrangement for embedding a watermark in an image comprising;

means for identifying a given number of most significant image pixels;

means for defining a watermark in the form of a pattern of pixels; and

means for locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern;

means for generating a transmission signal from said locally warped image; and

means for applying said transmission signal to a transmission medium.

12. The apparatus as claimed in claim 11, wherein said transmission medium is airwaves, said generating means comprises means for modulating said locally warped image onto a carrier wave, and said applying means comprises means for transmitting said modulated carrier wave over said airwaves.

13. The apparatus as claimed in claim 11, wherein said transmission medium is the Internet.

14. An apparatus for displaying a watermarked image signal retrieved from a transmission medium, wherein said watermarked image signal has been generated by identifying a given number of most significant image pixels, defining a watermark in the form of a pattern of pixels, and locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern, said apparatus comprising:

means for retrieving a transmission signal from said transmission medium;

means for converting said transmission signal into an image signal;

means for detecting a watermark in said image signal, said detecting means comprising;

means for identifying a given number of most significant image pixels;

means for determining the distances of said most significant image pixels to the watermark pattern; and

means for generating a detection signal indicating that said predetermined watermark is embedded in the suspect image, if the average distance of said most significant pixels to the watermark pattern is significantly smaller than the average distance of all image pixels to the watermark pattern; and

means for selectively displaying said image signal in dependence on said detection signal.

15. A method of embedding a watermark in an image and for recording said watermarked image on a record carrier, comprising the steps:

embedding a watermark in an image, including the sub-steps;

identifying a given number of most significant image pixels;

defining a watermark in the form of a pattern of pixels; and

locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern;

generating a recording signal from said locally warped image; and

recording said recording signal on a record carrier.

16. The method as claimed in claim 15, wherein said record carrier is a magnetic tape.

17. The method as claimed in claim 15, wherein said record carrier is an optical disk.

18. A method for playing back and displaying a watermarked image signal recorded on a record carrier, wherein said watermarked image signal has been generated by identifying a given number of most significant image pixels, defining a watermark in the form of a pattern of pixels, and locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern, said method comprising the steps:

playing back a recording signal from said record carrier;

converting said recording signal into an image signal;

detecting a watermark in said image signal, including the sub-steps;

identifying a given number of most significant image pixels;

determining the distances of said most significant image pixels to the watermark pattern; and

generating a detection signal indicating that said predetermined watermark is embedded in the suspect image, if the average distance of said most significant pixels to the watermark pattern is significantly smaller than the average distance of all image pixels to the watermark pattern; and

selectively displaying said image signal in dependence on said detection signal.

19. An apparatus for embedding a watermark in an image and for recording said watermarked image on a record carrier, comprising:

means for embedding a watermark in an image comprising;

means for identifying a given number of most significant image pixels;

means for defining a watermark in the form of a pattern of pixels; and

means for locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern;

means for generating a recording signal from said locally warped image; and

means for recording said recording signal on a record carrier.

20. An apparatus for playing back and displaying a watermarked image signal recorded on a record carrier, wherein said watermarked image signal has been generated by identifying a given number of most significant image pixels, defining a watermark in the form of a pattern of pixels, and locally warping the image so as to move a significant percentage of the most significant image pixels to the vicinity of the watermark pattern, said apparatus:

means for playing back a recording signal from said record carrier;

means for converting said recording signal into an image signal;

means for detecting a watermark in said image signal comprising;

means for identifying a given number of most significant image pixels;

means for determining the distances of said most significant image pixels to the watermark pattern; and

means for generating a detection signal indicating that said predetermined watermark is embedded in the suspect image, if the average distance of said most significant pixels to the watermark pattern is significantly smaller than the average distance of all image pixels to the watermark pattern; and

means for selectively displaying said image signal in dependence on said detection signal.