Spot color substitution for digital watermarking

Patent metadata

Field	Value
Publication number	US-2016198064-A1
Application number	US-201514932645-A
Country	US
Kind code	A1
Filing date	Nov 4, 2015
Priority date	Aug 12, 2014
Publication date	Jul 7, 2016
Grant date	—

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.

First claim

What is claimed is:

1 . A digital watermark embedding method comprising:
obtaining data associated with a spot color S a , the spot color S a comprising a component of a color design; using one or more configured processors, determining a screen S s of the spot color S a ; selecting a substitute spot color candidate S b1 by: i) evaluating color distance or color error between the substitute spot color candidate S b1 and the screen S s , and ii) evaluating brightness of the substitute spot color candidate S b1 and the screen S s ; using one or more configured processors, determining a Cyan (C), Magenta (M) and Yellow (Y) process color tint that when combined with the substitute spot color candidate S b1 approximates the spot color S a ; transforming a determined CMY process color tint with a digital watermark signal to embed the digital watermark signal in the CMY process color tint, said transforming yielding a watermarked CMY process color tint; and combining the watermarked CMY process color tint and the substitute spot color candidate S b1 , said combining yielding a digital watermarked substitute spot color.

2 . The method of claim 1 in which said selecting a substitute spot color candidate S b1 further evaluates the brightness of the spot color S a .

3 . The method of claim 1 in which said determining a CMY process color tint determines by minimizing color error or color distance between i) a combination of a CMY color tint and the substitute spot color candidate S b1 , and ii) the spot color S a , in which the substitute spot color candidate S b1 and the spot color S a remain constant during the minimization.

4 . The method of claim 1 in which said selecting selects a plurality of substitute spot color candidates S bi , where i is a positive integer.

5 . The method of claim 4 further comprising: using one or more configured processors, determining a plurality of CMY process color tints that when combined respectively with their substitute spot color candidate S bi each approximates the spot color S a .

6 . The method of claim 1 further comprising substituting the digital watermarked substitute spot color for the spot color S a within the color design, said substituting yielding a transformed color design.

7 . The method of claim 6 further comprising printing the transformed color design on a physical substrate.

8 . A printed product package including the physical substrate, in which the physical substrates including the transformed color design printed by the method of claim 7 .

9 . The method of claim 1 in which the CMY tint comprise a Black (K) process color component, and said determining a CMY process color tint comprises determining a CMYK process color tint.

10 . The method of claim 1 in which said determining a screen S s of the spot color S a determines the screen S s with consideration of the screen S s being combined with a Cyan (C), Magenta (M) and Yellow (Y) process color tint

11 . A digital watermark embedding system comprising:
an input to receive color data; memory comprising data associated with a spot color S a , the spot color S a comprising a component of a color design; one or more processors configured for: generating a screen S s of the spot color S a ; means for evaluating substitute spot color candidates to select a substitute spot color candidate S b1 including: i) means for evaluating color distance or color error between the substitute spot color candidate S b1 and the screen S s , and ii) means for evaluating brightness of the substitute spot color candidate S b1 and the screen S s ; in which said one or more processors are configured for: determining a CMY process color tint that when combined with the substitute spot color candidate S b1 approximates the spot color S a ; means for embedding a digital watermark signal in the CMY process color tint, said means for embedding producing a digital watermarked CMY process color tint; and in which said one or more processors are configured for: merging the watermarked CMY process color tint and the substitute spot color candidate S b1 , the merging yielding a digital watermarked substitute spot color.

12 . The system of claim 11 in which said means for evaluating substitute spot color candidates comprises means for evaluating the brightness of the spot color S a .

13 . The system of claim 11 in which the determining a CMY process color tint determines through minimizing color error or color distance between i) a combination of a CMY color tint and the substitute spot color candidate S b1 , and ii) the spot color S a , in which the substitute spot color candidate S b1 and the spot color S a remain constant during the minimization.

14 . The system of claim 11 in which said means for evaluating substitute spot color candidates selects a plurality of substitute spot color candidates S bi , where i is a positive integer, and said one or more processors are configured for: determining a plurality of CMY process color tints that when combined respectively with their substitute spot color candidate S bi each approximates the spot color S a .

15 . The system of claim 11 in which said one or more processors are configured for substituting the digital watermarked substitute spot color for the spot color S a within the color design, said substituting yielding a transformed color design.

16 . A digital watermark embedding method 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.

17 . The method of claim 16 in which the data associated with the substitute candidate spot color comprises lab data.

18 . The method of claim 16 in which the data associated with the substitute candidate spot color comprises RGB or CMYK data.

19 . The method of claim 16 in which said determining final spot color candidates comprises determining Lab distance values or Chroma distance values relative to the first spot color for each of the plurality of substitute spot color candidates.

20 . The method of claim 16 in which said determining final spot color candidates comprises determining Lab distance values and Chroma distance values relative to the first spot color for each of the plurality of substitute spot color candidates.

Assignees

• Digimarc Corp

Inventors

• Bai Yang
• Falkenstern Kristyn R
• Reed Alastair M

Classifications

• G06T2201/0202

  whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness · CPC title

• G06T2201/0051

  Embedding of the watermark in the spatial domain · CPC title

• H04N1/32309 Primary

  in colour image data · CPC title

• G06T1/0028

  Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking · CPC title

• H04N1/54

  Conversion of colour picture signals to a plurality of signals some of which represent particular mixed colours, e.g. for textile printing · CPC title