Methods and systems for embedding data in images

• US 6,307,950 B1
• Filed: 02/02/2000
• Issued: 10/23/2001
• Est. Priority Date: 07/31/1992
• Status: Expired due to Fees

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Powell, Robert D., Nitzberg, Mark J.
• Primary Examiner(s): Johns, Andrew W.
• Application Number:
  US09/496,858
• Time in Patent Office: 629 Days
• Field of Search: 382/100, 382/112, 382/232, 356/71, 902/1, 902/4, 902/6, 283/17, 283/72, 283/73, 283/113, 380/210, 380/287, 380/54, 340/5.86
• US Class Current: 382/100
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0081 whereby both original and watermarked images are required at decoder, e.g. destination-based, non-blind, non-oblivious
• CPC Class Codes: G07D 7/0047 using checkcodes, e.g. coded numbers derived from serial number and denomination
• CPC Class Codes: G07D 7/0056 involving markings of altered colours
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation
• CPC Class Codes: G07D 7/2008 using pre-processing, e.g. de-blurring, averaging, normalisation or rotation
• CPC Class Codes: G07D 7/2033 Matching unique patterns, i.e. patterns that are unique to each individual paper
• CPC Class Codes: G07F 7/08 by coded identity card or credit card or other personal identification means without personal verification means G07F7/02
• CPC Class Codes: G07F 7/12 Card verification
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32208 involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition H04N1/32219, H04N1/32224 take precedence
• CPC Class Codes: H04N 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• CPC Class Codes: H04N 1/32245 Random or pseudorandom selection of pixels
• CPC Class Codes: H04N 1/32251 in multilevel data, e.g. greyscale or continuous tone data
• CPC Class Codes: H04N 1/32288 Multiple embedding, e.g. cocktail embedding, or redundant embedding, e.g. repeating the additional information at a plurality of locations in the image
• CPC Class Codes: H04N 1/3232 Robust embedding or watermarking
• CPC Class Codes: H04N 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/3235 : Checking or certification of the authentication information, e.g. by comparison with data stored independently
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes

Abstract

A method and system for embedding signatures within visual images in both digital representation and print or film. A signature is inseparably embedded within the visible image, the signature persisting through image transforms that include resizing as well as conversion to print or film and back to digital form. Signature points are selected from among the pixels of an original image. The pixel values of the signature points and surrounding pixels are adjusted by an amount detectable by a digital scanner. The adjusted signature points form a digital signature which is stored for future identification of subject images derived from the image. In one embodiment, a signature is embedded within an image by locating relative extrema in the continuous space of pixel values and selecting the signature points from among the extrema. Preferably, the signature is redundantly embedded in the image such that any of the redundant representations can be used to identify the signature. Identification of a subject image includes ensuring that the subject image is normalized with respect to the original image or the signed image. Preferably, the normalized subject image is compared with the stored digital signature.

Claims

1. A method of embedding data in an image encoded as points, each point having a parameter value, the method comprising the steps of:

randomly selecting first and second points corresponding to relative extrema; and

altering the image by

i. increasing the parameter value of the first point and of a first patch of points surrounding the first point and

ii. decreasing the parameter value of the second point and of a second patch of points surrounding the second point, thereby embedding data in the image.

2. The method of claim 1 wherein the step of randomly selecting is performed programmatically.

3. The method of claim 1 wherein each of the first and second points corresponds to an electronically represented pixel.

4. The method of claim 1 wherein the parameter values of points in patches are changed such that the first and second points can be identified after subsequent image processing.

5. The method of claim 1 wherein the parameter values of points in patches are changed in order to reduce visual perceptibility.

6. The method of claim 1 wherein the parameter values of points in first patches are changed by a first amount and the parameter values of points in second patches are changed by a second amount.

7. The method of claim 1 wherein the parameter values of points in first patches are increased by a first amount and the parameter values of points in second patches are decreased by a second amount.

8. The method of claim 1 further comprising the step of associating each randomly selected point with a 5×

5 block surrounding the point, thereby defining several patches in the image.

9. The method of claim 8 wherein the patches are far apart.

10. The method of claim 1 wherein the set comprises at least 50 random numbers.

11. The method of claim 1 wherein the image is monochrome.

12. The method of claim 1 wherein the image is color.

13. The method of claim 1 wherein the parameter is luminance.

14. The method of claim 1 wherein the parameter is chrominance.

15. The method of claim 1 wherein the step of altering the image comprises changing the parameter value of points belonging to at least one of the first and second patches by a subgroup amount associated with a subgroup to which each point in the at least one of the first and second patches belongs.

16. The method of claim 15 wherein each subgroup amount has a magnitude that depends on position within a patch.

17. An apparatus for embedding data in an image, the apparatus comprising:

means for randomly selecting first and second points corresponding to relative extrema;

means for creating an altered image by

i. increasing the pixel parameter value of the first point and of a first patch of points surrounding the first point and

ii. decreasing the pixel parameter value of the second point and of a second patch of points surrounding the second point, thereby embedding data in the image.

18. An image created by altering a host image comprised of points, each point having a parameter value, by randomly selecting first and second points corresponding to relative extrema, and increasing the parameter value the first point and decreasing the parameter value of the second point.