Data hiding for spot colors in product packaging
The present disclosure relates generally to data hiding for product packaging and other printed objects. One embodiment embeds an information signal in a spot color for product packaging. The spot color is screened, and overprinted with process color tint. The tint is modulated prior to overprinting with optimized signal tweaks. The optimization can include consideration of a detector spectral dependency (e.g., red and/or green illumination). Other embodiments and combinations are described in the subject patent document.
1. A method comprising:
obtaining color data representing a spot color ink;
accessing a table to obtain data representing a process color ink tint, the process color ink tint including at least a Cyan (C) component, a Magenta (M) component and a Yellow component (Y);
simulating an overprinting of the process ink tint with the color data;
decomposing the process ink tint into a maximum signal tweak and a minimum signal tweak, each of the maximum signal tweak and the minimum signal tweak having a Cyan (C) component, a Magenta (M) component and a Yellow component (Y);
controlling one or more processors for minimizing a color error metric of the overprinting relative to the data representing the spot color ink, and optimizing the maximum signal tweak and the minimum signal tweak according to at least a spectral dependency;
in which the optimizing includes determining color weights and a global signal strength, the color weights to be applied to the process color tint and the global signal strength for regulating a modulating process, wherein the modulating modulates the process color ink tint with the maximum signal tweak and the minimum signal tweak to represent an information signal; and
outputting the modulated process color ink tint for overprinting with the color data.
2. A system for encoding information for a printed article comprising:
memory for storing i) data representing a first color (S 1 ), ii) data representing second color data (S 2 ), and iii) data representing third color data (S 3 ), in which encoded information is provided by modulating the data representing third color data (S 3 ) with max (positive) and min (negative) tweaks;
one or more processors configured for:
determining a color error between a Si and a combination of S 2 and S 3 , 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 S 2 and S 3 , including minimizing the color error and minimizing the information modulating error; and
an output for providing the optimized combination of S 2 and S 3 for use in a design to be printed on the printed article.
3. The system of claim 2 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 (S 3 ) and the global signal strength for regulating the modulating.
4. The system of claim 3 in which the optimizing is constrained by spectral reflectance between 630 nm to 680 nm.
5. The system of claim 3 in which the optimizing is constrained by spectral reflectance between 655 nm to 670 nm.
6. The system of claim 3 in which the data representing third color data (S 3 ) comprises data representing two or more process colors, and the data representing second color data (S 2 ) represents a second color.
7. The system of claim 6 in which the second color comprises a screened-back version of the first color (S 1 ).
8. The system of claim 2 in which the max and min tweaks correspond to a 2-dimensional image digital watermark tile.
9. The system of claim 2 further comprising a display, in which said one or more processors is configured for providing a graphical user interface through which a user can select embedding options.
10. A method for generating a design for a printed article comprising:
minimizing: i) a color match error between a first color S 1 and a combination of data representing second color data (S 2 ) and data representing third color data (S 3 ), the combination including auxiliary encoded information in the data representing third color data, and ii) an information modulating error associated with modulations of the third color data (S 3 ) 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 (S 3 ) 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.
11. The method of claim 10 in which spectral component comprises a metric associated with a spectral reflectance between 630 nm to 680 nm.
12. The method of claim 10 in which the modulations correspond to a 2-dimensional image digital watermark tile.