Data hiding through optimization of color error and modulation error
The present disclosure relates generally to data hiding for retail product packaging and other printed objects such as substrates. One embodiment embeds an information signal in a spot color for printing on various substrates. 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). Many other embodiments and combinations are described in the subject patent document.
1. A printed label or packaging comprising:
a first printed area, the first printed area comprising a combination of i) a first color (S1), and ii) a second color (S2), in which encoded information is provided on said printed label or packaging through modulation of data representing the second color (S2) with max (positive) and min (negative) tweaks;
in which the combination has been optimized by:
determining a color error between data representing third color data (S3) and a combination of S1 and S2,
determining an information modulating error associated with the max and min tweaks; and
minimizing the color error and minimizing the information modulating error in the combination of S1 and S2;
a second printed area including a 1-dimensional or 2-dimensional barcode; and
a third printed area including text information printed thereon.
2. The printed label or packaging of claim 1 in which the combination has been optimized by a process which included determining color weights and a global signal strength, the color weights to be applied to the data representing the second color (S2) and the global signal strength for regulating the modulation.
3. The printed label or packaging of claim 2 in which the combination has been optimized by a process constrained by spectral reflectance between 630 nm to 680 nm.
4. The printed label or packaging of claim 2 in which combination has been optimized by a process constrained by spectral reflectance between 655 nm to 670 nm.
5. The printed label or packaging of claim 2 in which the data representing the second color (S2) comprises data representing two or more process colors, and the data representing the third color data (S3) represents a third color.
6. The printed label or packaging of claim 1 in which the first color (S1) comprises a screened-back version of the third color data (S3).
7. The printed label or packaging of claim 1 in which the max and min tweaks correspond to a 2-dimensional image digital watermark tile.
8. An image processing system for generating a design for a printed label or packaging comprising:
memory storing data representing a first color (Si);
means for minimizing i) a color match error between (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 (S3), and ii) an information modulating error associated with modulations of (S3) that carry the auxiliary encoded information,
said means for minimizing being constrained by a spectral component associated with an anticipated information detector,
means for obtaining color percentage values associated with at least (S3) and a signal strength value for regulating the modulations;
means for outputting the color percentage values and signal strength value;
means for encoding a signal in the design using the color percentage values and signal strength value, said means for encoding signal encoder generating an encoded design; and
means for determining signal robustness associated with the encoded design.
9. The image processing system of claim 8 in which the spectral component comprises a metric associated with a spectral reflectance between 630 nm to 680 nm.
10. The image processing system of claim 8 in which the modulations correspond to a 2-dimensional image digital watermark tile.
11. The image processing system of claim 8 further comprising a display, and means for providing a graphical user interface for rendering on said display through which embedding options can be selected.
12. The image processing system of claim 8 in which the combination is optimized by said means for determining color weights and a global signal strength, and in which said means for encoding applies the color weights to the data representing the third color data (S3) and regulates the modulations with the global signal strength.
13. An image processing method comprising:
obtaining color data representing a spot color ink;
obtaining 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);
determining an overprinting of the process color ink tint with the color data;
decomposing the process color 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);
minimizing a color error metric of the overprinting relative to the data representing the spot color ink;
optimizing the maximum signal tweak and the minimum signal tweak according to at least a spectral dependency;
transforming the process color ink tint with the maximum signal tweak and the minimum signal tweak to represent an information signal, said transforming yielding a transformed process color ink tint; and
outputting the transformed process color ink tint for overprinting with the color data.
14. The image processing method of claim 13 in which the spectral dependency comprises a metric associated with a spectral reflectance between 630 nm to 680 nm.
15. The image processing method of claim 13 , in which said optimizing comprises determining color weights and a global signal strength, the color weights for application to the process color ink tint, and the global signal strength for application to the maximum signal tweak and the minimum signal tweak.
16. The image processing method of claim 13 in which the spectral dependency comprises a metric associated with reflectance from blue light illumination.
17. The image processing method of claim 13 further comprising outputting robustness associated with the transformed process color ink tint.
18. The image processing system of claim 8 in which the spectral component comprises a metric associated with a blue light spectral reflectance.
19. The printed label or packaging substrate of claim 1 in which the combination has been optimized by a process constrained by spectral reflectance of blue light.