System and methods for encoding information for printed articles

• US 9,667,829 B2
• Filed: 11/04/2015
• Issued: 05/30/2017
• Est. Priority Date: 08/12/2014
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Reed, Alastair M., Bai, Yang, Falkenstern, Kristyn R.
• Primary Examiner(s): Ansari, Tahmina
• Application Number:
  US14/932,645
• Publication Number:
  US 20160198064A1
• Time in Patent Office: 573 Days
• Field of Search: None
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• 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 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness
• 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 1/32251 in multilevel data, e.g. greyscale or continuous tone data
• CPC Class Codes: H04N 1/32267 combined with processing of the image
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 1/54 Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6008 with primary colour signals, e.g. RGB or CMY(K)
• CPC Class Codes: H04N 1/6013 by simulating several colour corrected versions of the same image simultaneously on the same picture reproducer
• CPC Class Codes: H04N 1/622 with simulation on a subsidiary picture reproducer
• CPC Class Codes: H04N 1/628 Memory colours, e.g. skin or sky

Abstract

The present disclosure relates generally to digital watermarking for spot colors. In one implementation a substitute spot color+CMY tint is selected to replace an original spot color. The CMY tint can be transformed to carry a digital watermark signal. Of course, other features, combinations and technology are described herein.

Claims

1. A method for generating a color design for a printed article comprising:

obtaining data associated with a first spot color S_a, the first spot color S_a comprising a component of a color design;

determining a plurality of substitute spot color candidates S_b1-S_bi, where i is an integer, by evaluating—

for each substitute spot color candidate—

color distance metrics between data associated with the substitute candidate spot color and the data associated with the first spot color S_a;

determining a Cyan (C), Magenta (M) and Yellow (Y) tint for each of the plurality of substitute spot color candidates S_b1-S_bi;

using one or more electronic processors, simulating an overprint of each of the plurality of substitute spot color candidates S_b1-S_bi with its respective CMY tint, and for each of the overprinted substitute spot color candidates, generating an Lab or Chroma distance metric relative to the first spot color S_a;

based on generated distance metrics, determining final spot color candidates;

for at least one of the final spot color candidates, and using one or more electronic processors, transforming its respective CMY tint with a digital watermark signal; and

substituting the at least one of the final spot color candidates plus its transformed CMY tint for the first spot color S_a in the color design.

2. The method of claim 1 in which the data associated with the substitute candidate spot color comprises Lab data.

3. The method of claim 1 in which the data associated with the substitute candidate spot color comprises RGB or CMYK data.

4. The method of claim 1 in which said determining final spot color candidates comprises determining Lab distance values relative to the first spot color S_a for each of the plurality of substitute spot color candidates S_b1-S_bi.

5. The method of claim 1 in which said determining final spot color candidates comprises determining Chroma distance values relative to the first spot color S_a for each of the plurality of substitute spot color candidates S_b1-S_bi.

6. A system for encoding information for a printed article comprising:

memory for storing i) data representing a first color (S1), ii) data representing second color data (S2), and iii) data representing third color data (S3), in which encoded information is provided by modulating the data representing third color data (S3) with max (positive) and min (negative) tweaks;

one or more processors configured for;

determining a color error between S1 and a combination of S2 and S3, the combination including the max and min tweaks;

determining an information modulating error associated with the max and min tweaks; and

optimizing the combination of S2 and S3, including minimizing the color error and minimizing the information modulating error; and

an output for providing the optimized combination of S2 and S3 for use in a design to be printed on the printed article.

7. The system of claim 6 in which the optimizing includes determining color weights and a global signal strength, the color weights to be applied to the data representing third color data (S3) and the global signal strength for regulating the modulating.

8. The system of claim 7 in which the optimizing is constrained by spectral reflectance between 630 nm to 680 nm.

9. The system of claim 7 in which the optimizing is constrained by spectral reflectance between 655 nm to 670 nm.

10. The system of claim 7 in which the data representing third color data (S3) comprises data representing two (2) or more process colors, and the data representing second color data (S2) represents a second color.

11. The system of claim 10 in which the second color comprises a screened-back version of the first color.

12. The system of claim 6 in which the max and min tweaks correspond to a 2-dimensional image digital watermark tile.

13. The system of claim 6 further comprising a display, in which said one or more processors are configured for providing a graphical user interface through which a user can select embedding options.

14. A system for transforming color data to include an information signal embedded therein, comprising:

memory storing spot color data, and system constraint information, the system constraint information including at least one spectral dependency; and

one or more processors configured as an optimizer bounded by the system constraint information, the optimizer generates C (Cyan), M (Magenta), Y (Yellow) process color data to be combined with a screen of the spot color data to yield a minimized color error approximation of the spot color data, the optimizer generates tweak values in terms of at least Δ

C, Δ

M, Δ

Y for modulating the C, M, Y process color data to carry the information signal, the tweak values optimized based on an error metric; and

one or more processors configured as an embedder that transforms the C, M, Y process color data with the tweak values.

15. A method for generating a design for a printed article comprising:

minimizing;

i) a color match error between a first color (S1) and a combination of data representing second color data (S2) and data representing third color data (S3), the combination including auxiliary encoded information in the data representing third color data, and ii) an information modulating error associated with modulations of the data representing third color data (S3) that carry the auxiliary encoded information,

said minimizing being constrained by a spectral component associated with an anticipated information detector,

in which said minimizing yields color percentage values associated with at least the data representing third color data (S3) and a signal strength value for regulating the modulations; and

outputting the color percentage values and signal strength value for use in a design to be printed on the printed article.

16. The method of claim 15 in which spectral component comprises a metric associated with a spectral reflectance between 630 nm to 680 nm.

17. The method of claim 15 in which the modulations correspond to a 2-dimensional image digital watermark tile.