ENCODING MESSAGE DATA IN A COVER CONTONE IMAGE VIA HALFTONE DOT ORIENTATION
First Claim
1. A method for embedding data in an image via halftone dot orientation, the method comprising:
- receiving a cover contone image having an intensity value associated with each pixel location of said image, a data message is to be embedded in said received image, said message comprising a plurality of data values, each single data value taking only one unique state from a set of possible values;
defining a uniform periodic tiling for said image, each of said uniform tiles having identical dimensions and encompassing an array of pixel intensity values;
for each unique state, defining an array of threshold values, each array of threshold values having a one-to-one correspondence with each array of pixel intensity values, and wherein each of said threshold values in said threshold array is defined for a given screen frequency and a given dot shape;
for each single data value of said message, identifying a unique uniform periodic tile wherein a single data value is to be embedded;
for each identified unique periodic tile wherein a current single data value is to be embedded, comparing each intensity value in said current periodic tile with a corresponding value of said threshold array defined for the unique state of said current single data value, said comparison producing a binary output value for each pixel location in said current tile, all of said comparisons collectively producing a binary mask for said current tile; and
rendering said image, each unique periodic tile wherein a single data value is to be embedded is rendered according to said binary mask produced for that tile.
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Abstract
What is disclosed is a novel system and method for encoding/decoding data in a cover contone image via halftone dot orientation modulation. Arrays of halftone threshold values are used to determine a desired orientation, e.g. 0/90°±45° for a given single data value of the original message to be embedded. Message data is embedded as a function of halftone dot orientation. Detection modeling of the print-scan process enables the determination of dot orientation from the image scan via statistically motivated image moments. A probabilistic model of the print-scan channel conditions received moments on input orientation. Density values of the received moments are used to determine dot orientation for each halftone cell. The embedded data is retrieved based on the determined orientations. The present method is applicable to areas of data embedding, document security, and the like.
32 Citations
20 Claims
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1. A method for embedding data in an image via halftone dot orientation, the method comprising:
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receiving a cover contone image having an intensity value associated with each pixel location of said image, a data message is to be embedded in said received image, said message comprising a plurality of data values, each single data value taking only one unique state from a set of possible values; defining a uniform periodic tiling for said image, each of said uniform tiles having identical dimensions and encompassing an array of pixel intensity values; for each unique state, defining an array of threshold values, each array of threshold values having a one-to-one correspondence with each array of pixel intensity values, and wherein each of said threshold values in said threshold array is defined for a given screen frequency and a given dot shape; for each single data value of said message, identifying a unique uniform periodic tile wherein a single data value is to be embedded; for each identified unique periodic tile wherein a current single data value is to be embedded, comparing each intensity value in said current periodic tile with a corresponding value of said threshold array defined for the unique state of said current single data value, said comparison producing a binary output value for each pixel location in said current tile, all of said comparisons collectively producing a binary mask for said current tile; and rendering said image, each unique periodic tile wherein a single data value is to be embedded is rendered according to said binary mask produced for that tile. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for embedding data in an image via halftone dot orientation, the system comprising:
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a storage medium capable of storing data; and a processor in communication with said storage medium, said processor capable of executing a machine readable instruction for performing the method of; receiving a cover contone image having an intensity value associated with each pixel location of said image, a data message is to be embedded in said received image, said message comprising a plurality of data values, each single data value taking only one unique state from a set of possible values; for each unique state, defining an array of threshold values, each array of threshold values having a one-to-one correspondence with each array of pixel intensity values, and wherein each of said threshold values in said threshold array is defined for a given screen frequency and a given dot shape; for each single data value of said message, identifying a unique uniform periodic tile wherein a single data value is to be embedded; for each identified unique periodic tile wherein a current single data value is to be embedded, comparing each intensity value in said current periodic tile with a corresponding value of said threshold array defined for the unique state of said current single data value, said comparison producing a binary output value for each pixel location in said current tile, all of said comparisons collectively producing a binary mask for said current tile; and rendering said image, each unique periodic tile wherein a single data value is to be embedded is rendered according to said binary mask produced for that tile. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A computer program product for embedding data in an image via halftone dot orientation, the computer program product comprising:
a computer-usable data carrier storing instructions that, when executed on a computer, cause the computer to perform a method comprising; receiving a cover contone image having an intensity value associated with each pixel location of said image, a data message is to be embedded in said received image, said message comprising a plurality of data values, each single data value taking only one unique state from a set of possible values; defining a uniform periodic tiling for said image, each of said uniform tiles having identical dimensions and encompassing an array of pixel intensity values; for each unique state, defining an array of threshold values, each array of threshold values having a one-to-one correspondence with each array of pixel intensity values, and wherein each of said threshold values in said threshold array is defined for a given screen frequency and a given dot shape; for each single data value of said message, identifying a unique uniform periodic tile wherein a single data value is to be embedded; for each identified unique periodic tile wherein a current single data value is to be embedded, comparing each intensity value in said current periodic tile with a corresponding value of said threshold array defined for the unique state of said current single data value, said comparison producing a binary output value for each pixel location in said current tile, all of said comparisons collectively producing a binary mask for said current tile; and rendering said image, each unique periodic tile wherein a single data value is to be embedded is rendered according to said binary mask produced for that tile. - View Dependent Claims (16, 17, 18, 19, 20)
Specification