Arrangements for enhancing digital watermark decoding
Imagery captured by a point-of-sale scanner (e.g., in a supermarket) for purposes of barcode decoding, is contrast-enhanced preparatory to use for watermark decoding—despite the fact that such operation may sometimes result in contrast between certain pixels being diminished. A great variety of other features and arrangements are also detailed.
1. An apparatus comprising:
a camera; and
processing circuitry, the processing circuitry being adapted to extract digital watermark data from imagery captured by the camera, the processing circuitry being more particularly configured to perform acts including:
receiving imagery including first and second pixels having different values, both of said values being less than a maximum possible pixel value and greater than zero;
contrast-enhancing the imagery, including changing values of both the first and second pixels; and
applying a digital watermark decoding process to the contrast-enhanced imagery, to extract identification data for an item depicted in the received imagery;
wherein said contrast-enhancing comprises changing both said first and second pixels to a shared value, wherein a difference in value between the first and second pixels is lost.
2. The apparatus of claim 1 in which the maximum possible pixel value is characterized by a bit depth at which the pixels are represented, wherein the processing circuitry is configured to change values of both the first and second pixels to equal said maximum possible pixel value.
3. The apparatus of claim 1 in which the processing circuitry is configured to change values of both the first and second pixels to equal zero.
4. The apparatus of claim 1 in which the processing circuitry is configured to down-sample the imagery as part of, or after, said contrast-enhancing act, yielding a set of imagery that is smaller than the received imagery, wherein said contrast-enhancing act aids in preserving differences in pixel values that would otherwise be lost by said down-sampling.
5. The apparatus of claim 1 in which at least 50 percent of the pixels in said received imagery have values in a lowest possible quartile.
6. The apparatus of claim 1 in which at least 75 percent of the pixels in said received imagery have values in a lowest possible quartile.
7. The apparatus of claim 1 in which at least 97 percent of the pixels in said received imagery have values in a lowest possible quartile.
8. The apparatus of claim 4 in which said down-sampling includes summing pixel values in the received imagery for plural neighborhoods of N pixels, yielding plural summed values, and dividing each of said summed values by a value K, where K<N, wherein a result of each such division operation is assigned as a value to a corresponding pixel in said set of down-sampled imagery.
9. The apparatus of claim 8 in which the maximum possible pixel value is characterized by a bit depth at which the pixels are represented, wherein at least one of said divisions yields a value that is greater than said maximum possible pixel value, and a pixel in said set of down-sampled imagery corresponding to said division operation is instead assigned said maximum possible pixel value.
10. The apparatus of claim 8 in which the processing circuitry is additional configured to apply a barcode reading process to a version of the captured imagery to which said down-sampling act—including said division by K, has not been applied.
11. The apparatus of claim 1 in which the processing circuitry is additionally configured to apply a first contrast enhancement process to a first excerpt of the imagery, and apply a second, different, contrast enhancement process to a second, different excerpt of the imagery.
12. The apparatus of claim 11 in which the first excerpt consists of a first set of pixels—at least 50% of which have values below a first threshold.
13. The apparatus of claim 12 in which the second excerpt consists of a second set of pixels—at least 50% of which have values above a second, different threshold.
14. The apparatus of claim 1 in which said camera exhibits compression of pixel values in the lowest quartile and/or in the highest quartile of pixel values, making small variations that characterize watermark signal encoding in said quartile(s) become still smaller.
15. The apparatus of claim 1 in which the processing circuitry comprises a programmable processor configured in accordance with stored software instructions.
16. An apparatus comprising:
a camera; and
processing circuitry, the processing circuitry being adapted to extract digital watermark data from imagery captured by the camera, the processing circuitry being more particularly configured to perform acts including:
receiving imagery including a first number of pixels;
down-sampling imagery in the received imagery, to yield a second set of imagery having a second number of pixels less than said first number, the down-sampling including processing each of plural neighborhoods of N pixels, where N>1, to derive a value for a corresponding single pixel in the second set of imagery; and
watermark processing the down-sampled second set of imagery to extract identification data for an item depicted in the received imagery;
wherein said down-sampling includes, for each of said plural neighborhoods of N pixels, summing values of the N pixels, and dividing the sum by a value K, where K<N.
17. The apparatus of claim 16 wherein:
the pixels in the second set of imagery have a maximum possible binary value;
a first of said divisions yields a first value that is greater than said maximum possible binary value; and
the processing circuitry is configured to assign the maximum possible binary value to said first pixel, instead of said first value.
18. The apparatus of claim 17 wherein:
a second of said divisions yields a second value that is greater than said maximum possible value, said second value being different than said first value; and
the processing circuitry is configured to assign the maximum possible binary value to said second pixel, instead of said second value;
wherein said first and second divisions yield different values, but the first and second pixels are instead assigned a common value.
19. The apparatus of claim 16 in which the processing circuitry is further configured to apply said down-sampling act—including said division by K, when using the imagery for digital watermark detection, but not applying said down-sampling act—including said division by K, when using the imagery for barcode detection.
20. The apparatus of claim 16 wherein the pixels in the second set of pixels span a greater range of values than pixels in the received imagery.
21. The apparatus of claim 16 in which said camera exhibits compression of pixel values in the lowest quartile and/or in the highest quartile of pixel values, making small variations that characterize watermark signal encoding in said quartile(s) become still smaller.
22. The apparatus of claim 16 in which said camera exhibits compression of pixel values in the lowest quartile and/or in the highest quartile of pixel values, making small variations that characterize watermark signal encoding in said quartile(s) become still smaller.
23. The apparatus of claim 16 in which the processing circuitry comprises a programmable processor configured in accordance with stored software instructions.
24. An apparatus for processing camera-captured imagery, said imagery comprising plural pixels including first and second pixels having different values, both of said values being less than a maximum possible pixel value and greater than zero, the apparatus including:
first means for contrast-enhancing the imagery; and
a digital watermark decoder for processing contrast-enhanced imagery produced by said first means, to extract identification data for an item depicted in said imagery;
wherein said first mean changes both said first and second pixels to a shared value, wherein a difference in value between the first and second pixels is lost.