Signal encoding outside of guard band region surrounding text characters, including varying encoding strength

1. An image processing method comprising the acts:

receiving a digital representation of product packaging artwork, comprised of pixels;

defining a guard band region surrounding text characters included in the artwork; and

altering the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork;

wherein said altering only alters the artwork outside of the guard band region, in which, outside of the guard band region, a strength of the encoding increases along a gradient extending away from the text characters.

2. The image processing method of claim 1 in which a first of the text characters has a first height, and an outer boundary of the guard band region is spaced from said first text character by less than said first height.

3. The image processing method of claim 2 the outer boundary of the guard band region is spaced from said first text character by less than half of said first height.

4. An image processing method comprising the acts:

receiving a digital representation of product packaging artwork, comprised of pixels;

defining a guard band region surrounding text characters included in the artwork, in which a first region encloses the guard band region, and a second region encloses the first region; and

altering the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork;

wherein said altering only alters the artwork outside of the guard band region, and wherein a strength of the encoding has a first value in the first region, and has a second, stronger, value in the second region.

5. The image processing method of claim 4 in which a third region encloses the second region, wherein a strength of the encoding has a third value in the third region that is greater than the second value.

6. The image processing method of claim 5 in which the guard band region defines a boundary including a portion that echoes a non-linear contour of a single one of the text characters.

7. An image processing method comprising the acts:

receiving a digital representation of product packaging artwork comprised of pixels, in which each of the pixels has only either a first or second value, corresponding to a dark and a background color;

defining a guard band region surrounding text characters included in said artwork; and

altering the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork, in which said altering comprises creating plural dithered blocks in the artwork, each of the blocks comprising a contiguous two-dimensional N-element region, where N>2;

wherein said altering only alters the artwork outside of the guard band region, and wherein said altering comprises toggling certain of the pixels between the first and second values, along a gradient direction in the artwork, a number of dark elements within at least some of the dithered blocks increases, yielding a greater density of darkening alteration along the gradient direction.

8. The image processing method of claim 7 in which the dithered blocks in the artwork are all of a common size.

9. The image processing method of claim 7 in which first and second dithered blocks in the artwork are of different sizes.

10. The image processing method of claim 7 that further includes printing the altered artwork using a thermal printing mechanism, onto a thermally-sensitive printing medium.

11. An apparatus comprising:

memory for storing a digital representation of product packaging artwork, comprised of pixels;

one or more multi-core processors configured for:

establishing a guard band region surrounding text characters included in the artwork; and

transforming the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork;

wherein the transforming only alters the artwork outside of the guard band region, in which, outside of the guard band, a strength of the encoding increases along a gradient extending away from the text characters.

12. The apparatus of claim 11 in which a first of the text characters has a first height, and an outer boundary of the guard band region is spaced from the first text character by less than the first height.

13. The apparatus of claim 12 in which the outer boundary of the guard band region is spaced from the first text character by less than half of the first height.

14. An apparatus comprising:

memory for storing a digital representation of product packaging artwork, comprised of pixels;

one or more multi-core processors configured for:

establishing a guard band region surrounding text characters included in the artwork, in which a first region encloses the guard band region, and a second region encloses the first region; and

transforming the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork;

wherein the transforming only alters the artwork outside of the guard band region, and wherein a strength of the encoding has a first value in the first region, and has a second, stronger, value in the second region.

15. The apparatus of claim 14 in which a third region encloses the second region, wherein a strength of the encoding has a third value in the third region that is greater than said second value.

16. The apparatus of claim 14 in which the guard band defines a boundary including a portion that echoes a non-linear contour of a single one of the text characters.

17. An apparatus comprising:

memory for storing a digital representation of product packaging artwork, comprised of pixels, in which each of the pixels has only either a first or second value, corresponding to a dark and a background color;

one or more multi-core processors configured for:

establishing a guard band region surrounding text characters included in the artwork; and

transforming the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork, in which the transforming comprises creating plural dithered blocks in the artwork, each of the plural dithered blocks comprising a contiguous two-dimensional N-element region, where N>2;

wherein the transforming only alters the artwork outside of the guard band region,

and wherein the transforming comprises toggling certain of the pixels between the first and second values, in which, along a gradient direction in the artwork, a number of dark elements within at least some of the dithered blocks increases, yielding a greater density of darkening alteration along the gradient direction.

18. The apparatus of claim 17 in which the dithered blocks in the artwork are all of a common size.

19. The apparatus of claim 17 in which first and second dithered blocks in the artwork comprise different sizes.

20. The apparatus of claim 17 in which said one or more multi-core processors are configured for controlling printing of the transformed artwork using a thermal printing mechanism, onto a thermally-sensitive printing medium.

21. The apparatus of claim 17 in which the encoded machine-readable plural-bit payload comprises digital watermarking.