Information coding and decoding in spectral differences
First Claim
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1. A method of encoding a machine-readable data signal in an image, the method comprising, with a programmed processor:
- generating an information signal comprising message symbols;
mapping message symbol elements of the information signal to insertion locations within a host image signal; and
at the insertion locations, inserting the information signal by computing values for controlling application of a spot color ink and a combination of process color inks, the values for controlling application of process color inks forming a spectral difference signal between process color ink applied at a first pixel location and spot color ink applied at a second pixel location to encode a message symbol element in relative spectral difference between the process color ink at the first pixel location and spot color ink at the second pixel location, the computing encoding a relative spectral difference at the first and second pixel locations that conveys the message symbol element within the host image, the spectral difference signal representing a distinguishable spectra between a spot color and a combination of process colors that appear similar in the human visual system;
wherein the relative spectral differences at the insertion locations comprise differences between spectral distributions of spot and process color inks at corresponding pairs or sets of locations.
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Abstract
Information is encoded in an image signal by exploiting spectral differences between colors that appear the same when rendered. These spectral differences are detected using image sensing that discerns the spectral differences. Spectral difference detection methods include using sensor-synchronized spectrally-structured-light imaging, 3D sensors, imaging spectrophotometers, and higher resolution Bayer pattern capture relative to resolution of patches used to convey a spectral difference signal.
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Citations
20 Claims
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1. A method of encoding a machine-readable data signal in an image, the method comprising, with a programmed processor:
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generating an information signal comprising message symbols; mapping message symbol elements of the information signal to insertion locations within a host image signal; and at the insertion locations, inserting the information signal by computing values for controlling application of a spot color ink and a combination of process color inks, the values for controlling application of process color inks forming a spectral difference signal between process color ink applied at a first pixel location and spot color ink applied at a second pixel location to encode a message symbol element in relative spectral difference between the process color ink at the first pixel location and spot color ink at the second pixel location, the computing encoding a relative spectral difference at the first and second pixel locations that conveys the message symbol element within the host image, the spectral difference signal representing a distinguishable spectra between a spot color and a combination of process colors that appear similar in the human visual system; wherein the relative spectral differences at the insertion locations comprise differences between spectral distributions of spot and process color inks at corresponding pairs or sets of locations. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A non-transitory computer readable medium, on which is stored instructions, which configure a processor to perform a method of encoding a machine-readable data signal in an image, the method comprising:
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generating an information signal comprising message symbols; mapping message symbol elements of the information signal to insertion locations within a host image signal; and at the insertion locations, inserting the information signal by computing values for controlling application of a spot color ink and a combination of process color inks, the values for controlling application of process color inks forming a spectral difference signal between process color ink applied at a first pixel location and spot color ink applied at a second pixel location to encode a message symbol element in relative spectral difference between the process color ink at the first pixel location and spot color ink at the second pixel location, the computing encoding a relative spectral difference at the first and second pixel locations that conveys the message symbol element within the host image, the spectral difference signal representing a distinguishable spectra between a spot color and a combination of process colors that appear similar in the human visual system; wherein the relative spectral differences at the insertion locations comprise differences between spectral distributions of spot and process color inks at corresponding pairs or sets of locations. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of decoding an information signal from an image comprising:
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obtaining spectra of an image signal at locations within the image signal; detecting a spectral difference at the locations by determining, at the locations, a relative difference between a spectral distribution of a combination of process inks and a spot color ink;
the process color inks forming a spectral difference signal between process color ink applied at a first pixel location and spot color ink applied at a second pixel location that encodes a message symbol element in relative spectral difference between the process color ink at the first pixel location and spot color ink at the second pixel location, the detecting comprising determining a relative spectral difference at the first and second pixel locations to extract the message symbol element from the host image, the spectral difference signal representing a distinguishable spectra between a spot color and a combination of process colors that appear similar in the human visual system;
wherein the relative spectral differences at the locations comprise differences between spectral distributions of spot and process color inks at corresponding pairs or sets of locations; anddecoding an information signal from the spectral difference by extracting message symbols from the message symbol elements extracted from relative differences between spectral distributions of the process and spot color inks, and error correction decoding a message from the message symbols. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification