Fragile and emerging digital watermarks

• US 8,094,869 B2
• Filed: 04/29/2004
• Issued: 01/10/2012
• Est. Priority Date: 07/02/2001
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Reed, Alastair M., Rodriguez, Tony F., Sharma, Ravi K.
• Primary Examiner(s): Desire, Gregory M
• Assistant Examiner(s): Allison, Andrae S
• Application Number:
  US10/836,094
• Publication Number:
  US 20050041835A1
• Time in Patent Office: 2,812 Days
• Field of Search: 382/100, 382135-137, 283/94, 399/366, 235/454, 235/468, 235/472, 235/491, 358/1.9, 358/1.14, 380/238, 713/176
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0042 Fragile watermarking, e.g. so as to detect tampering
• CPC Class Codes: H04N 1/00002 Diagnosis, testing or measuring; Detecting, analysing or monitoring not otherwise provided for error detection, error correction or monitoring in digital computers or digital computer components G06F11/00
• CPC Class Codes: H04N 1/00005 relating to image data
• CPC Class Codes: H04N 1/00037 Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence

Abstract

This disclosure describes methods for using embedded auxiliary signals in documents for copy detection. In one implementation we embed an auxiliary signal with a first color that is out of gamut with process color inks or with a particular range of printers. A process color approximation of the first color yields a relatively different contrast when, e.g., viewed with an interference filter. A copy is determined based on the relative presence or absence of the auxiliary signal. In another implementation, we provide a first auxiliary signal with a first color and a second auxiliary signal with a second color. A filter is matched according to the spectral response of the first color. The second color preferably includes a spectral response that is inversely related to the matched filter. The first signal is then detectable in a process color copy, but less so in the original. However, the second signal is detectable in the original, but less so in the copy. In still other implementations we compare relative contrast of a signal to determine an original from a copy.

Claims

1. A method comprising:

imaging a printed object with an emphasizer including transmission characteristics, wherein the printed object comprises a first machine readable auxiliary signal conveyed with a first color including a spectral response that is inversely related to the transmission characteristics of the emphasizer, the printed object further comprising a second machine readable auxiliary signal embedded therein, wherein the second machine readable auxiliary signal is conveyed with a second color including a spectral response that corresponds to the transmission characteristics of the emphasizer, wherein the first color comprises a first spot color and the second color comprises a second, different spot color;

based on the detection of at least one of the first machine-readable auxiliary signal or the second machine-readable auxiliary signal, determining whether the printed object is a copy or an original.

2. The method of claim 1, wherein the printed object is determined to be an original when the first machine-readable auxiliary signal is detectable at a predetermined level.

3. The method of claim 1, wherein the printed object is determined to be a copy when the second machine-readable auxiliary signal is detectable at a predetermined level.

4. The method of claim 1, wherein the printed object is determined to be an original when the first machine-readable auxiliary signal is detectable at a predetermined level, and the second machine-readable auxiliary signal is at least one of undetectable or detectable but below a predetermined threshold.

5. The method of claim 1, wherein a copy is produced through an operation that approximates each of the first spot color and the second spot color with process color inks.

6. The method of claim 5, wherein the emphasizer comprises an interference filter.

7. The method of claim 5, wherein the emphasizer comprises selective illumination.

8. The method of claim 5, wherein the emphasizer comprises a color contrast enhancer.

9. A method comprising:

emphasizing contrast of a first spot color and a second spot color relative to a white background in an image captured of a printed object, wherein the act of emphasizing renders either the first spot color or the second spot color visually imperceptible relative to the white background in the image; and

based on a detection reading of at least one of a first machine-readable auxiliary signal conveyed with a first color or a second machine-readable auxiliary signal conveyed with a second color, determining whether the image corresponds to an image of an original printed object or copy of the original printed object.

10. A method comprising:

emphasizing contrast of a first color and second color relative to a white background in an image captured of a printed object, wherein the first color comprises a first spot color and the second color comprises a second spot color; and

based on a detection reading of at least one of a first machine-readable auxiliary signal conveyed with a first color or a second machine-readable auxiliary signal conveyed with a second color, determining whether the image corresponds to an image of an original printed object or copy of the original printed object.

11. A method comprising:

emphasizing contrast of a first color and second color relative to a white background in an image captured of a printed object; and

based on a detection reading of at least one of a first machine-readable auxiliary signal conveyed with a first color or a second machine-readable auxiliary signal conveyed with a second color, determining whether the image corresponds to an image of an original printed object or a copy of the original printed object, wherein the copy is made by a process color approximation of a first spot color and a second spot color, with at least one of the first spot color and the second spot color being out of gamut with respect to the process color inks.

12. The method of claim 11, wherein the first spot color is out of gamut, and wherein the contrast of the first spot color is emphasized so that the first machine-readable auxiliary signal is less detectable in an original in comparison to the process color ink approximation of the first auxiliary signal in a copy.

13. The method of claim 12, wherein the second spot color is also out of gamut, and wherein the contrast of the second spot color is emphasized so that the second machine-readable auxiliary signal is more detectable in the original in comparison to a similarly emphasized process color ink approximation of the second auxiliary signal in a copy.

14. A method comprising:

determining whether at least one of a first machine readable auxiliary signal and a second machine readable auxiliary signal is embedded in an image, wherein the first auxiliary signal is conveyed using a first color and the second auxiliary signal is conveyed using a second color, the first and second colors being represented differently in response to a copy operation, the different representation providing a divergence or convergence of a characteristic of the colors such that the machine readable signals becomes more or less detectable, wherein the first color comprises a first spot color, and the second color comprises a second spot color; and

based on evaluating the machine-readable auxiliary signals, determining whether the printed object is a copy or an original, wherein the copy operation comprises a first approximation of the first spot color with process color inks and a second approximation of the second spot color with process color inks.

15. The method of claim 14, wherein the characteristic comprises relative contrast.

16. The method of claim 15, wherein the first approximation provides enhanced contrast convergence in comparison to the first spot color when imaged with a filter that is matched to the spectral response of the first spot color.

17. The method of claim 15, wherein the first approximation provides enhanced contrast convergence in comparison to the first spot color when image with illumination that is matched to the spectral response of the first spot color.

18. The method of claim 16, wherein the second approximation provides contrast divergence relative to the second spot color when imaged with a filter that is inversely matched to the spectral response of the second spot color.

19. The method of claim 16, wherein the second approximation provides contrast divergence relative to the second spot color when imaged with illumination that is inversely matched to the spectral response of the second spot color.