Method for encoding auxiliary data within a source signal

• US 6,459,803 B1
• Filed: 04/11/2001
• Issued: 10/01/2002
• 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:
  US09/829,980
• Time in Patent Office: 538 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, 283/901, 380/210, 380/287, 380/54, 340/5.8, 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 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 digital document containing an indicia applied to an original document, comprising:

a digital image defined by an array of adjacent pixels, each pixel having a pixel value selected from the group consisting of luminance and a color value, a first pixel value of a first predetermined pixel having a relation to a second pixel value of a second adjacent pixel, wherein

said first pixel and said second adjacent pixel being positioned to define said indicia image, and

said relation is a mathematical relationship used in applying said indicia image to the original image.

2. A digital document in accordance with claim 1 wherein said pixel value consists of luminance.

3. A digital document in accordance with claim 1 wherein said pixel value consists of a color value.

4. A method of detecting a location for an indicia in a digital image formed of an array of pixels having a pixel value, comprising the steps of:

determining an amount of the pixel value of respective pixels in said array of pixels, said pixel value being selected from the group consisting of luminance and a color value;

calculating a difference in average pixel value between pixels corresponding to signature points in said array of pixels; and

comparing the difference in average pixel value with a predetermined difference range to determine those pixels corresponding to signature points.

5. A method in accordance with claim 4 wherein said pixel value consists of luminance.

6. A method in accordance with claim 4 wherein said pixel value consists of a color value.

7. A method in accordance with claim 4 wherein said selected pixels are adjacent pixels.

8. A method in accordance with claim 7 wherein said pixel value consists of luminance.

9. A method in accordance with claim 7 wherein said pixel value consists of a color value.

10. The method of claim 4, further comprising the step of:

generating an output image represented by an output array of pixels, said output array including altered pixels at locations for which the comparing step yielded a difference that was within the predetermined difference range.

11. A method for identifying an indicia location in a digital image formed of an array of pixels having a pixel value, comprising the steps of:

calculating a difference of pixel values for a selected pixel and a plurality of pixels surrounding the selected pixel;

comparing the difference of pixel values with a predetermined difference range; and

categorizing the selected pixel as one of an indicia location and not an indicia location based on a result of the comparing step.