Method and computer program product for hiding information in an indexed color image

• US 6,697,498 B2
• Filed: 02/02/2001
• Issued: 02/24/2004
• Est. Priority Date: 02/02/2001
• Status: Expired due to Fees

• Current Assignee: ASA Systems, Inc.
• Original Assignee: ASA Systems, Inc.
• Inventors: Eason, Richard, Niimi, Michiharu, Kawaguchi, Eiji
• Primary Examiner(s): Johnson, Timothy M.
• Assistant Examiner(s): AZARIAN, SEYED H
• Application Number:
  US09/776,172
• Publication Number:
  US 20020031241A1
• Time in Patent Office: 1,117 Days
• Field of Search: 382/100, 382/240, 382/232, 382/233, 382/245, 382/246, 382/248, 382/250, 382/162, 382/163, 382/166, 382/167, 375/240.01, 375/240.11, 375/240.03, 375/240.23, 358/1.9, 358/2.99, 358/3.09, 348/463, 348/603, 348/642
• 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

Abstract

A method and computer program product for embedding information within an indexed color image such that the existence of the data is not recognizable by the human eye. The method includes the steps of altering color image data, such that it will not cause a large color change in the representing image, and hiding information using an information hiding method. The altering step is accomplished via a color set changing method. The color set changing method involves first decomposing the image in to a set of color component images, embedding data in the color component or components, which the human visual system is most sensitive to, then merging representative colors until the number of representative colors is less than or equal to the target number of colors and reformatting the resulting image into indexed color image format.

Claims

1. A method for hiding information in an indexed color image comprising a palette having a target number colors, said method comprising the steps of:

decomposing said indexed color image into at least three images corresponding to three color components of said indexed color image, said images comprising a first color component image, a second color component image and a third color component image;

embedding said information into said first color component image, wherein said embedding step would result in a palette having a total number of colors if said first color component image, said second color component image and said third color component image were recomposed into said indexed color image;

comparing said total number of colors with said target number of colors to determine whether said total number of colors is greater than said target set of colors;

reducing said total number of colors such that said total number of colors is less than the sum of the target number of colors plus one; and

recomposing said first color component image, said second color component image and said third color component image into an indexed color image;

wherein said reducing step is performed only when said total number of colors is greater than said target number of colors, and wherein said reducing step comprises the steps of detecting at least two colors having a same first color component, and merging said at least two colors into one representative color.

2. The method as claimed in claim 1, wherein said decomposing step comprises decomposing said image into a brightness component image, a second component image, and a third component image.

3. The method as claimed in claim 2 wherein said embedding step comprises embedding said information into said brightness component image.

4. The method as claimed in claim 3 wherein said recomposing step comprises the steps of recomposing said brightness component image, said second component image, and said third component image into an indexed color image such that said brightness component image is exactly recoverable during an extraction process.

5. The method as claimed in claim 4 wherein said recomposing step comprises the steps of recomposing said brightness component image, said second component image, and said third component image into an indexed color image having red, green, and blue components such that said brightness component image is exactly recoverable during an extraction process.

6. The method as claimed in claim 5 wherein said recomposing step comprises the steps of recomposing said brightness component image, said second component image, and said third component image into an indexed color image having red, green, and blue components such that a last three bits of said brightness component image are stored in a last three bits of each of said red, green and blue component images.

7. The method as claimed in claim 1, wherein said decomposing step comprises decomposing said image into a red component image, a green component image, and a blue component image.

8. The method as claimed in claim 7 wherein said embedding step comprises embedding said information into said green component image.

9. The method as claimed in claim 1 wherein said reducing step further comprises the steps of determining at least one two colors to be merged and determining a resulting color based upon an average of said colors to be merged.

10. The method as claimed in claim 1 wherein said reducing step further comprises that steps of determining at least one two colors to be merged, and determining a resulting color based upon a number of instances of each color to be merged.

11. A computer program product for controlling a computer for embedding information within an indexed color image comprising a palette having a target number colors, said computer program product comprising:

a recording medium readable by the computer;

means recorded on said recording medium for decomposing said indexed color image into at least three images corresponding to three color components of said colors of said indexed color image, said images comprising a first color component image, a second color component image and a third color component image;

means recorded on said recording medium for embedding said information into said first color component image such that said embedding would result in a palette having a total number of colors, if said first color component image, said second color component image and said third color component image were recomposed into said indexed color image;

means recorded on said recording medium for comparing said total number of colors with said target number of colors to determine whether said total number of colors exceeds said target set of colors;

means recorded on said recording medium for reducing said total number of colors such that said total number of colors is less than the sum of the target number of colors plus one; and

means recorded on said recording medium for recomposing said first color component image, said second color component image and said third color component image into an indexed color image;

wherein said reducing means reduces said total number of colors only when said total number of colors is greater than said target number of colors, and wherein said reducing means comprises the means for detecting at least two colors having a same first color component, and means for merging said at least two colors into one representative color.

12. The computer program product as claimed in claim 11, wherein said means for decomposing comprises a means for decomposing said image into a brightness component image, a second component image, and a third component image.

13. The computer program product as claimed in claim 12, wherein said means for embedding comprises a means for embedding said information into said brightness component image.

14. The computer program product as claimed in claim 13, wherein said means for recomposing comprises a means for decomposing said brightness component image, said second component image, and said third component image into an indexed color image such that said brightness component image is exactly recoverable during an extraction process.

15. The computer program product as claimed in claim 14, wherein said means for recomposing comprises a means for decomposing said brightness component image, said second component image, and said third component image into an indexed color image having red, green, and blue components such that said brightness component image is exactly recoverable during an extraction process.

16. The computer program product as claimed in claim 15, wherein said means for recomposing comprises a means for recomposing said brightness component image, said second component image, and said third component image into an indexed color image having red, green, and blue components such that a last three bits of said brightness component image are stored in a last three bits of each of said red, green and blue component images.

17. The computer program product as claimed in claim 11, wherein said means for decomposing comprises means for decomposing said image into a red component image, a green component image, and a blue component image.

18. The computer program product as claimed in claim 17, wherein said means for embedding comprises means for embedding said information into said green component image.

19. The computer program product as claimed in claim 11, wherein said means for reducing further comprises a means for determining at least one two colors to be merged and means for determining a resulting color based upon an average of said colors to be merged.

20. The computer program product as claimed in claim 11, wherein said means for reducing further comprises means for determining at least one two colors to be merged, and means for determining a resulting color based upon a number of instances of each color to be merged.