MACHINE READABLE DOCUMENTS AND READING METHODS
First Claim
Patent Images
1. A method of independently encoding an image with two information channels, comprising:
- generating an image which encodes a primary information channel, the image comprising image portions, wherein the image portions are generated as an image portion with brightness above a first threshold, or as an image portion with brightness below a second threshold, the brightness levels encoding the primary information channel; and
modifying the image to encode a secondary information channel, wherein the image modification is applied to at least some of the image portions and comprises applying one of two image output values to the image portion, wherein the brightness of a modified image portion is not changed such as to cross the first or second thresholds, wherein the image output values are used to encode the secondary information channel.
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Abstract
A method of independently encoding an image with two information channels comprises generating an image which encodes a primary information channel based on brightness levels. The image is modified to encode a secondary information channel. This image modification comprises applying one of two image output values to the image portion, wherein the brightness of a modified image portion is not changed such as to change the primary information channel encoding.
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Citations
19 Claims
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1. A method of independently encoding an image with two information channels, comprising:
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generating an image which encodes a primary information channel, the image comprising image portions, wherein the image portions are generated as an image portion with brightness above a first threshold, or as an image portion with brightness below a second threshold, the brightness levels encoding the primary information channel; and modifying the image to encode a secondary information channel, wherein the image modification is applied to at least some of the image portions and comprises applying one of two image output values to the image portion, wherein the brightness of a modified image portion is not changed such as to cross the first or second thresholds, wherein the image output values are used to encode the secondary information channel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A machine readable document comprising an image which encodes a primary information channel, the image comprising:
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image portions, wherein the image portions comprise a first set of image portions with brightness above a first threshold, and a second set of image portions with brightness below a second threshold, the brightness levels encoding the primary information channel; and wherein at least some of the image portions encode a secondary information channel, and each comprise one of two image output values, wherein the two image output values are such that the brightness of an image portion when modified to one of the two image output values is not changed such as to cross the first or second thresholds.
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19. Apparatus for decoding an image which comprises:
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image portions, wherein the image portions comprise a first set of image portions with brightness above a first threshold, and a second set of image portions with brightness below a second threshold, the brightness levels encoding the primary information channel; and wherein at least some of the image portions encode a secondary information channel, and each comprise one of two image output values, wherein the two image output values are such that the brightness of an image portion when modified to one of the two image output values is not changed such as to cross the first or second thresholds, wherein the apparatus comprises means for decoding the primary information channel based on the brightness levels of the image portions, and means for decoding the secondary information channel by analysing the output values.
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Specification