Encoding information within text printed on a page using differing gray or color levels

• US 6,771,820 B1
• Filed: 08/12/1999
• Issued: 08/03/2004
• Est. Priority Date: 08/12/1999
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Oakeson, Kenneth L.
• Primary Examiner(s): Do, Anh Hong
• Application Number:
  US09/373,458
• Time in Patent Office: 1,818 Days
• Field of Search: 382/232, 382/249, 382/233, 382/167, 382/240, 380/54, 380/28, 345/555, 156/277, 715/529, 358/450, 358/518, 358/560, 358/406, 358/527
• US Class Current: 382/232
• 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 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• CPC Class Codes: H04N 1/32251 in multilevel data, e.g. greyscale or continuous tone data

Abstract

A document processing system for imperceptibly encoding information in displayed images or text. Printed text or other images are modified using gray levels to encode information within existing text or images. The text is modified using digital processing to provide text or images in which adjacent portions of individual text characters, for example, have slightly different gray levels in accordance with an encoding scheme to encode addition information within the existing text. The modifications to the text is so slight that it is imperceptible to the human eye, yet is easily detectable by a machine such as a scanner.

Claims

1. A method of encoding information on a page of printed text, the method comprising the steps of:

providing a first set of data representing one or more characters in a page of text to be printed;

identifying allowable encoding locations within the one or more characters on the page of text;

generating a second set of data representing information to be encoded at one or more of the allowable encoding locations; and

modifying the first set of data with the second set of data so that the one or more characters on the page of text, when printed, are altered to include the encoded information, the alterations made to the one or more characters being imperceptible to the human eye.

2. The method of claim 1, wherein the modifications to the one or more characters on the page of text are imperceptible to the human eye.

3. A method of encoding information within text displayed on a page utilizing one or more intensity levels to modify the text, the method comprising the steps of:

identifying allowable encoding locations within one or more characters on a page of text;

generating a first set of data representing intensity level values corresponding to the one or more characters at the encoding locations;

generating a second set of data representing information to be encoded at the encoding locations;

combining the first and second sets of data to generate a third set of data representing modified intensity level values corresponding to the one or more characters at the encoding locations.

4. The method of claim 3 further including the step of utilizing the third set of data to display or print the text.

5. The method of claim 3 wherein the step of identifying allowable encoding locations comprises the steps of:

overlaying the page with a grid referenced to a predefined point on the page;

identifying allowable encoding locations according to a predefined criteria; and

mapping the allowable encoding locations to the grid.

6. The method of claim 5 wherein the grid comprises a uniform grid.

7. The method of claim 5 wherein the grid comprises a non-uniform grid.

8. The method of claim 5 wherein each of the allowable encoding locations corresponds to one or more single pixel locations that is formed within at least one of the one or more characters.

9. The method of claim 5 wherein each of the allowable encoding locations corresponds to a plurality of pixels associated according to a predefined rule.

10. The method of claim 5 wherein the intensity level values comprise digital values, each digital value representing a gray level corresponding to an associated intensity level.

11. The method of claim 3, wherein the modified intensity level values of the one or more characters on the page of text are imperceptible to the human eye as compared to unmodified characters on the page of text.

12. Apparatus for encoding information within text printed on a page utilizing one or more intensity levels to modify the printed text, the apparatus comprising:

first input means for providing digital data representative of original images to be modified;

processor means coupled to the first input means for identifying allowable encoding locations within the original images and for converting the digital data to a first set of data representing intensity values corresponding to the original images at the allowable encoding locations;

second input means coupled to the processor means for providing a second set of data representing selected information to be encoded within the original images, the processor means combining the first and second sets of data to generate a third set of data representative of the original images with at least a portion of the images modified to include the selected information encoded therein, when the modified images are printed, the modification to the original images being imperceptible to the human eye.

13. Apparatus as in claim 12 further comprising printer means coupled to the processor means and being controlled by the third set of data to print the modified images on a print medium, the difference between the modified images and the original images being imperceptible to the human eye.

14. Apparatus as in claim 12 further comprising electronic transmitting means coupled to the processor means for transmitting the third set of data to a remote location.

15. Apparatus as in claim 14 wherein the electronic transmitting means comprises a facsimile machine.

16. Apparatus as in claim 12 wherein the first input means comprises a scanner for reading a printed document and providing digital data representative of original images printed on the printed document.

17. Apparatus as in claim 12 further including memory means coupled to the first and second input means, and the processor means for storing digital data representative of the original images and of the selected information to be encoded.

18. Apparatus as in claim 12 wherein the processor is operating under computer program control.

19. Apparatus as in claim 12 wherein the second input means comprises a personal computer coupled to the processor means and the first input means, the personal computer including a keyboard enabling a user to provide the selected information for encoding.

20. Apparatus as in claim 12 wherein the original images comprise text characters.

21. Apparatus as in claim 12 wherein the intensity level values comprise digital values, each digital value representing a gray level corresponding to an associated intensity level.

22. The apparatus of claim 12, wherein modifications to the intensity values of the one or more characters on the page of test are imperceptible to the human eye as compared to unmodified characters on the page of text.

23. An article of manufacture comprising a program storage medium having computer readable program code means embodied therein for adapting a computer to encode selected information within images printed on a page, the computer readable program code means in the article of manufacture including:

computer readable program code means for enabling a computer to identify allowable encoding locations on a page;

computer readable program code means for enabling a computer to generate a first set of data representing intensity level values corresponding to one or more characters of text located at the encoding locations;

computer readable program code means for enabling a computer to generate a second set of data representing selected information to be encoded within the images; and

computer readable program code means for enabling a computer to combine the first and second sets of data to generate a third set of data representing modified intensity level values corresponding to the one or more characters of text at the encoding locations so that the one or more characters are modified to include the selected information encoded therein, wherein when the modified characters are printed, the modifications to the printed characters are imperceptible to the human eye.

24. The article of manufacture as in claim 23 wherein the intensity level values comprise digital values, each digital value representing a gray level corresponding to an associated intensity level.

25. A method, comprising;

providing information to be encoded in a page of text containing one or more characters;

modifying at least one character in the text to encode information so that when the page of text is printed, the modified character includes the encoded information;

overlaying the at least one character with a grid referenced to a predefined point on the page;

identifying allowable encoding locations according to a predefined criteria; and

mapping the allowable encoding, locations to the grid.

26. The method of claim 25, wherein the modification to the at least one modified character is imperceptible to the human eye as compared to unmodified characters on the page of text.

27. The method of claim 25, further comprising printing the page of text.

28. The method of claim 25, further comprising displaying the page of text.

29. The method of claim 25, wherein the modifying comprises varying intensity level values of certain pixels within the modified character.