Encoding invisible electronic information in a printed document

• US 20060072778A1
• Filed: 09/28/2004
• Published: 04/06/2006
• Est. Priority Date: 09/28/2004
• Status: Abandoned Application

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Harrington, Steven J.
• Application Number:
  US10/951,394
• Publication Number:
  US 20060072778A1
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32208 involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition H04N1/32219, H04N1/32224 take precedence
• CPC Class Codes: H04N 1/32309 in colour image data
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes

Abstract

Substantially invisible elements of an electronic code can be embedded in a document independent of the layout of the image being displayed to provide document related data. Generally, code elements are printed in a color that has luminance values that do not vary substantially from the luminance of the location on the document where they are placed. Thus, the embedded data will be substantially invisible to the human eye at normal reading distances, yet capable of being captured by a conventional digital scanner. In one aspect, elements of the code are printed on a black and white document, as blue dots in content locations and as yellow dots in background locations. To decode the information, the system and method identifies locations for potential code element candidates based upon the relative luminance of the pixel and the surrounding location of the image. The pattern in which all elements of the code are positioned in the image is then identified and output values are assigned to all characters that belong to the code depending upon the relative dominance of blue light reflected from the respective location in the image. Significantly, the present system and method enables information that is related to the document image to be printed and detected at all pixels in a document.

Claims

1. A data encoder, comprising:

an input channel configured to receive pixels for an input image;

a code element pattern producer configured to produce an input image independent positioning pattern for elements of an electronic code;

a code element candidate identifier that identifies pixels in locations corresponding to said positioning pattern and determines a density output value for said identified pixels in a selected input image separation;

and a code element color generator configured to provide a color value for said identified pixels based upon a density output value for said identified pixel in said selected separation.

2. A data encoder as claimed in claim 1 further comprising a code element color generator further configured to assign a content location color value to an identified pixel if said identified pixel density output value is a maximum density output value for said selected input image separation.

3. A data encoder as claimed in claim 2 further comprising a code element color generator configured to assign a background location color value to an identified if said density output value is a minimum density output value for said selected input image separation.

4. A data encoder as claimed in claim 3 wherein said code element color generator is further configured to assign to said identified pixel, a color value with a luminance that is substantially the same as a luminance of an original color value for said identified pixel.

5. A data encoder as claimed in claim 3 wherein said selected image separation represents an intensity of blue light reflected in an RGB description of a color input image.

6. A data encoder as claimed in claim 3 wherein said selected separation controls a deposit of a yellow colorant onto a color image formed by combining cyan, magenta and yellow colorants.

7. A data encoder as claimed in claim 5 wherein said content location color value represents blue and said background location color value represents yellow.

8. A data encoder as claimed in claim 3 wherein said pattern has code elements that are vertically aligned.

9. A data encoder as claimed in claim 3 wherein said pattern has code elements that are horizontally aligned.

10. A method, comprising:

receiving input pixels representing an input image that includes substantially invisible elements of an electronic code;

producing an input image independent positioning pattern for said substantially invisible code elements;

identifying a plurality of pixels in said input image that are in locations corresponding to said input image independent pattern;

determining a colorant print amount for said identified pixel in a selected separation;

and printing a substantially invisible code element at said identified pixel, with said substantially invisible code element color determined by said colorant print amount for said selected separation.

11. A method as claimed in claim 10 further comprising printing a content color substantially invisible code element at said identified pixel if said colorant print amount is a maximum colorant print amount for said selected separation.

12. A method as claimed in claim 11 further comprising printing a background color substantially invisible code element at said identified pixel if said colorant print amount is a minimum colorant print amount for said selected separation.

13. A method as claimed in claim 10 wherein a substantially invisible code element luminance is substantially the same as an original luminance of said identified pixel.

14. A method as claimed in claim 10 wherein said background color substantially invisible electronic code element is yellow and said content color substantially invisible electronic code element is blue.

15. A method as claimed in claim 10 wherein said substantially invisible code element positioning pattern provides vertically aligned substantially invisible code elements.

16. A method as claimed in claim 10 wherein said substantially invisible code element positioning pattern provides horizontally aligned substantially invisible code elements.

17. A digital printing system, comprising:

an image processor configured to generate binary printer signals that represent an input image, said input image having a plurality of substantially invisible elements of an electronic code positioned therein independent of an input image content layout;

a print channel configured to receive said binary printer signals from said image processor as a plurality of separations;

and an output generator configured to generate a hardcopy reproduction of said substantially invisible code element containing input image.

18. A digital printing system as claimed in claim 17 further comprising:

a code element pattern producer configured to produce a positioning pattern for said substantially invisible code elements;

a code element candidate identifier that identifies a pixel corresponding to said positioning pattern and provides a colorant amount for said identified pixel in a selected separation; and

a content location code element generator configured to deposit a content location substantially invisible code element at said identified pixel if said indicated colorant amount is a maximum colorant amount for said selected separation.

19. A digital printing system as claimed in claim 18 further comprising a background location code element generator configured to deposit a background location substantially invisible code element at said identified pixel if said indicated colorant amount is a minimum colorant amount for said selected separation.

20. A digital printing system as claimed in claim 17 wherein said selected separation represents an intensity of blue light reflected in an RGB description of a color input image.

21. A data decoder, comprising:

an image sensor configured to capture an input image that includes a plurality of substantially invisible elements of an electronic code as pixels that represent an intensity of light reflected said input image;

a code element locator configured to identify a plurality of pixels that have a color value that is substantially different from said average color value for a surrounding neighborhood and a luminance value that is substantially the same as an average luminance value for a surrounding neighborhood;

a code element pattern detector configured to detect a layout pattern for said electronic code based upon a spatial relationship of said code element locator identified pixels; and

an electronic code generator configured to identify input image pixels corresponding to said electronic code pattern and assign output values to said identified electronic code pattern corresponding pixels based upon a dominance of a selected color of light reflected from said input image.

22. A data encoder as claimed in claim 21 wherein said substantially invisible code elements are positioned in said input image independent of a layout of an input image content.

23. A data decoder as claimed in claim 21 wherein said electronic code generator is configured to said assign output values to said electronic code pattern corresponding pixels depending upon a dominance of blue light reflected from said input image.

24. A data decoder as claimed in claim 21 wherein said input images is captured by a conventional digital scanner.

25. A data decoder as claimed in claim 21 wherein said input images is captured by a digital scanner that detects red, green and blue components of visible light, has an 8 bit depth and is capable of generating 256 levels of color for each of said red, green and blue light components.

26. A data decoder as claimed in claim 21 wherein said electronic code value generator is further configured to assign an output value of 1 to each pixel where:

|B−

(R+G)/2|−

|R−

G|>

T,

wherein T is a threshold value, B is a value that represents the intensity of blue light reflected from said input image, R is a value that represents an average intensity of red light reflected from a surrounding neighborhood and G is a value that represents an average intensity of green light reflected from a surrounding neighborhood.

27. A data decoder as claimed in claim 26 wherein said selected light component represents an intensity of blue light reflected in an RGB description of a color input image.

28. A data decoder as claimed in claim 26 wherein said electronic code generator is further configured to assign output values to a portion of said electronic code based upon an intensity of yellow light reflected from said image at pixels that correspond to said electronic code pattern.

29. A method, comprising:

capturing an input image that includes a plurality of substantially invisible elements of an electronic code, at least one of which is positioned in a content of said input image;

and processing a plurality of said substantially invisible code elements to provide information related to said input image.

30. A method as claimed in claim 29 further comprising:

identifying electronic code element candidate pixels with color values that are substantially different from the average color of a surrounding neighborhood and luminance values that are substantially the same as an average luminance of a surrounding neighborhood;

detecting a layout pattern for said electronic code based upon a spatial arrangement of said identified code element candidate pixels;

identifying input image pixels corresponding to said electronic code pattern; and

assigning output values to said identified electronic code pattern corresponding pixels based upon a dominance of light reflected from said input image having primarily a selected color.

31. A method as claimed in claim 30 wherein said primarily reflected light color is blue.

32. A method as claimed in claim 30 wherein said primarily reflected light color is yellow.

33. A method as claimed in claim 30 further comprising processing said electronic code to provide device readable output.

34. A method as claimed in claim 30 further comprising processing said electronic code to provide information related to said input image.

35. A method as claimed in claim 30 further comprising processing said electronic code to provide viewable data.