Covert digital identifying indicia for digital image
First Claim
Patent Images
1. A method of affixing a covert digital identifying indicia to a digital image, comprising the steps of:
- providing, to a processor, an input image defined by an array of pixel units each pixel unit having a control quality selected from the group consisting of luminance and saturation;
providing to said processor an identifying indicia template defining an identifying indicia image and formed of a plurality of bits which have a spatial correspondence with pixels in said array of pixel units;
altering, in said array of pixel units defining said input image, the control quality of pixel units which have said spatial correspondence, to a pre-selected difference level, said pre-selected difference level being in a range selected to render the alter ed pixel units minimally detectable to the human eye when they are displayed;
generating, from said processor, an array of pixels defining an output image, said array of pixels in said output image being comprised of said input image with said altered pixel units, so as to embed in said output image covert detectable identifying indicia which represent said identifying indicia image.
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Abstract
A method and system for affixing covert identifying indicia to a digital image document, by altering pixel luminance and/or saturation in the image in selected areas of the image to a selected differential in luminance and/or saturation. The differential in luminance and/or saturation is selected to be in a range which is minimally detectable by the human eye. The identifying indicia may be detected by checking the digital document for patterns of differential luminance and/or saturation in the selected range of the differential.
109 Citations
36 Claims
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1. A method of affixing a covert digital identifying indicia to a digital image, comprising the steps of:
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providing, to a processor, an input image defined by an array of pixel units each pixel unit having a control quality selected from the group consisting of luminance and saturation; providing to said processor an identifying indicia template defining an identifying indicia image and formed of a plurality of bits which have a spatial correspondence with pixels in said array of pixel units; altering, in said array of pixel units defining said input image, the control quality of pixel units which have said spatial correspondence, to a pre-selected difference level, said pre-selected difference level being in a range selected to render the alter ed pixel units minimally detectable to the human eye when they are displayed; generating, from said processor, an array of pixels defining an output image, said array of pixels in said output image being comprised of said input image with said altered pixel units, so as to embed in said output image covert detectable identifying indicia which represent said identifying indicia image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A digital document containing covert identifying indicia, comprising a digital image defined by an array of adjacent pixel units, each pixel unit having a control quality selected from the group consisting of luminance and saturation;
- predetermined pixel units within said array having a pre-selected difference in control quality, said pre-selected difference in control quality being in a range selected to be minimally detectable to the human eye when said digital document is displayed, said pixel units having said pre-selected difference in control quality being positioned to define, in the aggregate within said array of pixel units, an embedded covert identifying indicia image.
- View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. A method of detecting covert identifying indicia in a digital image formed of an array of pixel units having a control quality, comprising the steps of:
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determining the amount of the control quality of respective pixel units in said array of pixel units, said control quality being selected from the group consisting of luminance and saturation; calculating a difference in the control quality between selected pixel units in said array of pixel units; comparing the calculated differences with a predetermined control quality difference range to determine those pixel units representative of said covert identifying indicia when said calculated differences are within said predetermined control quality difference range; generating an output image represented by an output array of pixel units, said output array including pixel units for which the comparing step yielded a difference in control quality that was within the predetermined control quality difference range, said pixel units in said output array being capable of producing a contrast area against a background area, said contrast area being positioned at spatial locations corresponding to locations for said covert identifying indicia in the digital image. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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30. A method of detecting covert identifying indicia in a digital image formed of an input array of pixel units having a control quality, comprising the steps of:
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determining the amount of the control quality of adjacent pixel units in said digital image, said control quality of respective pixel units in said input array of pixel units being selected from the group consisting of luminance and saturation; calculating and storing the differences in said amount of said control quality between adjacent pixel units in said input array of pixel units of said digital image; determining a range for the most common calculated differences in said control quality generating an output image represented by an output array of pixel units for display, wherein pixel units from the input array of pixel units, for which the calculated control quality difference falls within the range, have a changed control quality to be capable of producing, when displayed, a contrast area with respect to a background display of pixel units whose control quality is outside the range, so as to reveal the covert identifying indicia embedded within the pixel units of said digital image. - View Dependent Claims (31, 32)
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33. A system for placing a covert identifying indicia within a digital image, comprising:
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a digital input image, having a plurality of adjacent pixel units, each having a luminance, stored in a digital storage device; an identifying indicia template having an identifying indicia image formed of a plurality of bits stored in a digital storage device, said bits having a luminance; a digital processor programmed to combine said input image and said identifying indicia template so that the luminance of the pixel units and said bits is adjusted to generate an output image containing covert identifying indicia formed of a plurality of adjacent pixel units, each having a luminance, with certain of said adjacent pixel units having a pre-selected difference in luminance, said pre-selected difference in luminance being in a range selected to be minimally detectable to the human eye, said adjacent pixel units having said pre-selected difference in luminance being positioned to define said identifying indicia image; and a digital storage device for storing said output image containing covert identifying indicia.
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34. A method of affixing a covert digital identifying indicia to a digital image, comprising the steps of:
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providing an input image, having a plurality of adjacent pixel units, each having a hue, saturation, and luminance, to a processor; providing to said processor an identifying indicia template input having a spatial correspondence with said input image and having an identifying indicia image in the form of a plurality of bits at predetermined spatial locations relative to said input image; combining, in said processor, the pixel units of said input image with the bits of said identifying indicia template input to generate an output image containing covert identifying indicia by altering said saturation of adjacent pixel units in said input image, at positions selected to correspond to said identifying indicia image, to a selected difference in saturation, said selected difference in saturation being in a range selected to be minimally detectable to the human eye.
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35. A method of affixing a covert digital identifying indicia to a digital image, comprising the steps of:
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providing an input image, having a plurality of adjacent pixel units, each having a luminance, to a processor; providing to said processor an identifying indicia template input having a spatial correspondence with said input image and having an identifying indicia image in the form of a plurality of bits at predetermined spatial locations relative to said input image; combining, in said processor, the pixel units of said input image with the bits of said identifying indicia template input to generate an output image containing covert identifying indicia by altering said luminance of adjacent pixel units in said input image, at positions selected to correspond to said identifying indicia image, to a pre-selected difference in luminance, said pre-selected difference in luminance being in a range selected to be minimally detectable to the human eye. - View Dependent Claims (36)
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Specification