Image marking with pixel modification

• US 6,628,801 B2
• Filed: 10/12/1999
• Issued: 09/30/2003
• 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:
  US09/417,153
• Publication Number:
  US 20020037090A1
• Time in Patent Office: 1,449 Days
• Field of Search: 382/100, 382/112, 382/232, 340/825.34, 340/5.86, 356/71, 902/1, 902/4, 902/6, 283/17, 283/72, 283/73, 283/113, 283/901, 380/210, 380/287, 380/54
• 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 placing a watermark on a digital image, comprising the steps of:

providing a digital original image;

providing a digital watermark image; and

,

producing a watermarked image by superimposing the watermark image on the original image without changing the chromaticities of pixels of the original image as watermarked.

2. The method of claim 1 wherein the step of producing comprises the step of:

for a selected number of points, modifying the corresponding pixel of the original image by changing the brightness but not the color.

3. The method of claim 1 wherein the step of producing comprises the step of:

for a selected number of relative extrema, modifying the corresponding pixel of the original image by changing the brightness but not the color.

4. A method of applying an imperceptible digital watermark to an original image comprising the step of applying the watermark to the original image as a percentage correction on pixel sample values of the original image in a linear color space such that the chromaticities of the pixels are not changed.

5. A system for placing a watermark on a digital image, comprising:

a storage device having a digital original image and a digital watermark stored therein; and

,

means for producing a watermarked image by superimposing the watermark on the original image without changing the chromaticities of the original image as watermarked.

6. The system of claim 5 wherein the means for producing comprises:

means for modifying each selected pixel of the original image corresponding to a selected point, by changing the brightness but not the color.

7. The system of claim 5 wherein the means for producing comprises:

means for modifying each selected pixel of the original image corresponding to a relative extrema, by changing the brightness but not the color.

8. A system for applying an imperceptible digital watermark to an original digital image, comprising:

means for identifying a subset of pixels of the original image that will be modified as a result of applying the watermark;

a programmed processor operable to determine a modification corresponding to a percentage adjustment based on the values of the color components for each of the pixels in the subset,

means for multiplying each of the color components of each of the pixels in the subset by its percentage adjustment, and

means for storing a resulting watermarked image.

9. A method for applying an imperceptible digital watermark to an original digital image, comprising the steps of:

identifying a subset of pixels of the original image to be modified;

for each pixel in said subset of pixels, determining a percentage value based on the values of the color components of said pixel; and

,

multiplying each component of said pixel by said percentage value, and,

storing a resulting watermarked image.

10. A method for applying an imperceptible digital watermark to an original digital image, comprising the steps of:

identifying a subset of pixels of the original image to be modified;

for each pixel in said subset of pixels, determining a percentage value based on the values of the color components of said pixel; and

,

modifying each component of said pixel by said percentage value, and, storing a resulting watermarked image.