Methods and arrangements for enhanced digital signal detection

1. A method for transforming an input array of pixel data into an output array of data, both of said arrays including a digital watermark signal, said transforming enhancing a signal-to-noise ratio of the digital watermark signal in the output array relative to the input pixel array, the method comprising the acts:

for each pixel in said input array, generating a first datum, said first datum indicating a value difference between said pixel and a neighboring pixel in a first direction, said first data thereby collectively comprising a first directional difference array;

for each pixel in said array of pixel data, generating a second datum, said secondary datum indicating a value difference between said pixel and a neighboring pixel in a second direction different than the first direction, said second data thereby collectively comprising a second directional difference array;

performing one or more transformations to a spatial frequency domain, using said first and second directional difference arrays as input data;

combining first and second results produced from said one or more transformations, to yield an output array, wherein the aforesaid acts cause the digital watermark signal in the output array to exhibit a greater signal-to-noise ratio than in the digital watermark signal in said input array.

2. The method of claim 1 that includes:

decoding a payload component from said digital watermark signal; and

sorting an item of plastic based on said decoded payload component.

3. The method of claim 1 that includes:

decoding a payload component from said digital watermark signal; and

adding an item to a shopper's checkout tally based on said decoded payload component.

4. The method of claim 1 that includes:

discerning a pose of a digitally-watermarked object within said input array of pixel data, based on the output array; and

resampling the input array of pixel data based on said discerned pose.

5. The method of claim 1 that includes:

performing a first domain transformation on the first directional difference array, yielding a first set of spatial frequency domain data;

performing a second domain transformation on the second directional difference array, yielding a second set of spatial frequency domain data; and

summing said first and second sets of spatial frequency domain data, to yield said output array.

6. The method of claim 1 that includes:

packing the first and second directional difference arrays into a larger array;

performing a domain transformation on the larger array, yielding a set of spatial frequency domain data;

segmenting the spatial frequency domain data into plural parts, along straight boundaries defined by spatial frequency coordinates; and

summing said plural parts to yield said output array.

7. A method of processing imagery comprising plural pixels, the method comprising the acts:

for each pixel in a region of adjoining pixels, generating an N-element vector indicating relationships between a value of said pixel and values of N neighboring pixels, thereby yielding plural N-element vectors, where N is an integer greater than 1;

assembling first elements of said vectors into a first 2D array;

assembling second elements of said vectors into a second 2D array;

combining the first and second 2D arrays into a composite array;

transforming said composite array into a spatial frequency domain representation; and

detecting a digital watermark reference signal from said spatial frequency domain representation.

8. The method of claim 7 that includes segmenting said spatial frequency domain representation into parts, and combining said parts to yield a combined spatial frequency domain representation, wherein said detecting is performed on said combined spatial frequency domain representation.

9. A method of processing imagery comprising plural pixels, the method comprising the acts:

for each pixel in a region of adjoining pixels, generating an N-element vector indicating relationships between a value of said pixel and values of N neighboring pixels, thereby yielding plural N-element vectors, where N is an integer greater than 1;

assembling first elements of said vectors into a first 2D array;

assembling second elements of said vectors into a second 2D array;

transforming the first 2D array into a first spatial frequency domain representation;

transforming the second 2D array into a second spatial frequency domain representation;

combining said first and second spatial frequency domain representations into a composite spatial frequency domain representation; and

detecting a digital watermark reference signal from said composite spatial frequency domain representation.

10. The method of claim 1 that includes the acts:

for each pixel in said array of pixel data, generating a third datum, said third datum indicating a value difference between said pixel and a neighboring pixel in a third direction different than the first and second directions, the third data thereby collectively comprising a third directional difference array;

performing one or more transformations to a spatial frequency domain, using said first, second and third directional difference arrays as input data;

combining first, second and third results produced from said one or more transformations, to yield an output array, wherein the aforesaid acts cause the digital watermark signal in the output array to exhibit a greater signal-to-noise ratio than in the digital watermark signal in said input array.

11. The method of claim 10 that includes the acts:

performing a first domain transformation on the first directional difference array, yielding a first set of spatial frequency domain data;

performing a second domain transformation on the second directional difference array, yielding a second set of spatial frequency domain data;

performing a third domain transformation on the third directional difference array, yielding a third set of spatial frequency domain data; and

summing said first, second and third sets of spatial frequency domain data, to yield said output array.

12. The method of claim 10 that includes packing said first, second and third directional difference arrays into the larger array.

13. The method of claim 10 that includes the acts:

for each pixel in said array of pixel data, generating a fourth datum, said fourth datum indicating a value difference between said pixel and a neighboring pixel in a fourth direction different than the first, second and third directions, the fourth data thereby collectively comprising a fourth directional difference array;

performing one or more transformations to a spatial frequency domain, using said first, second, third and fourth directional difference arrays as input data; and

combining first, second, third and fourth results produced from said one or more transformations, to yield an output array, wherein the aforesaid acts cause the digital watermark signal in the output array to exhibit a greater signal-to-noise ratio than in the digital watermark signal in said input array.

14. The method of claim 13 that includes the acts:

performing a first domain transformation on the first directional difference array, yielding a first set of spatial frequency domain data;

performing a second domain transformation on the second directional difference array, yielding a second set of spatial frequency domain data;

performing a third domain transformation on the third directional difference array, yielding a third set of spatial frequency domain data;

performing a fourth domain transformation on the fourth directional difference array, yielding a fourth set of spatial frequency domain data; and

summing said first, second, third and fourth sets of spatial frequency domain data, to yield said output array.

15. The method of claim 13 that includes packing said first, second, third and fourth directional difference arrays into the larger array.

16. A noise reducing filter method for imagery, the imagery comprising plural pixels in a region of adjoining pixels, each pixel having a value, the filter method comprising the acts:

(a) characterizing each of said pixels by a plural-element vector that indicates respective value relationships between a value of said pixel and values of each of plural neighboring pixels, thereby yielding a plural-element vector for each pixel in said region;

(b) assembling first elements of said plural-element vectors into a first 2D array;

(c) assembling second elements of said plural-element vectors into a second 2D array;

(d) performing one or more transformations to a spatial frequency domain, using said first and second arrays as input data; and

(e) combining first and second results corresponding to said one or more transformations to yield an output array;

wherein characterizing each pixel in said region in plural ways, based on value relationships with each of plural neighboring pixels, followed by said acts (b), (c), (d) and

(e), yields a spatial frequency domain representation of the imagery in which an interfering signal component is diminished.

17. The method of claim 16 wherein said imagery depicts a physical object bearing a digital watermark conveying a payload signal component and a reference signal component, and the method includes the acts:

processing said output array to obtain the payload signal component; and

sorting said object, or identifying and adding said object to a shopper's checkout tally, based on said payload signal component.

18. The method of claim 16 wherein said imagery depicts a physical object bearing a digital watermark conveying a payload signal component and a reference signal component, and the method includes the act:

discerning a pose with which said physical object is depicted in said imagery.

19. The method of claim 16 that includes:

performing a first domain transformation on the first 2D array, yielding a first set of spatial frequency domain data;

performing a second domain transformation on the second 2D array, yielding a second set of spatial frequency domain data; and

summing said first and second sets of spatial frequency domain data, to yield said output array.

20. The method of claim 16 that includes:

packing the first and second 2D arrays into a larger array;

performing a domain transformation on the larger array, yielding a set of spatial frequency domain data;

segmenting the spatial frequency domain data into plural parts, along straight boundaries defined by spatial frequency coordinates; and

summing said plural parts to yield said output array.