Enhancing embedding of out-of-phase signals

• US 20020164052A1
• Filed: 04/02/2002
• Published: 11/07/2002
• Est. Priority Date: 04/19/2000
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Reed, Alastair M., Brundage, Trent J., Hannigan, Brett T.
• Granted Patent: US 6,912,295 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: B42D 25/00 Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof printing processes to produce identification or security features B41M3/14
• CPC Class Codes: B42D 25/333 Watermarks
• CPC Class Codes: G06F 16/955 using information identifiers, e.g. uniform resource locators [URL]
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 19/06046 Constructional details
• CPC Class Codes: G06K 19/14 the marking being sensed by radiation
• CPC Class Codes: G06K 19/18 Constructional details
• CPC Class Codes: G06K 2019/06253 for a specific application
• CPC Class Codes: G06K 7/1417 2D bar codes
• CPC Class Codes: G06K 7/1447 extracting optical codes from image or text carrying said optical code
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G06Q 20/40145 Biometric identity checks
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 1/0042 Fragile watermarking, e.g. so as to detect tampering
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06V 30/40 Document-oriented image-based pattern recognition
• CPC Class Codes: G07C 9/253 visually
• CPC Class Codes: G07D 7/0034 using watermarks
• CPC Class Codes: G07D 7/004 using digital security elements, e.g. information coded on a magnetic thread or strip
• CPC Class Codes: G07F 17/16 for devices exhibiting advertisements, announcements, pictures or the like
• CPC Class Codes: G07F 7/086 : by passive credit-cards adapted therefor, e.g. constructive particularities to avoid counterfeiting, e.g. by inclusion of a physical or chemical security-layer for security documents G07D7/00; for the reading of record-carriers in general G06K7/00; for the design of coded credit-cards G06K19/10
• CPC Class Codes: G07F 7/1008 : Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system
• CPC Class Codes: G10L 19/018 : Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G11B 20/00086 : Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00884 : involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: G11B 20/00891 : embedded in audio data
• CPC Class Codes: H04N 1/00005 : relating to image data
• CPC Class Codes: H04N 1/00037 : Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00079 : remotely
• CPC Class Codes: H04N 1/32122 : in a separate device, e.g. in a memory or on a display separate from image data
• CPC Class Codes: H04N 1/32149 : Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/32154 : Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/3216 : using Fourier transforms
• 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
• CPC Class Codes: H04N 1/32288 : Multiple embedding, e.g. cocktail embedding, or redundant embedding, e.g. repeating the additional information at a plurality of locations in the image
• CPC Class Codes: H04N 1/32293 : Repeating the additional information in a regular pattern
• CPC Class Codes: H04N 1/32309 : in colour image data
• CPC Class Codes: H04N 1/32352 : Controlling detectability or arrangements to facilitate detection or retrieval of the embedded information, e.g. using markers for decoding, detection or retrieval operations H04N1/32149 and subgroups take precedence
• CPC Class Codes: H04N 19/467 : characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 21/23892 : involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• CPC Class Codes: H04N 21/8358 : involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• CPC Class Codes: H04N 2201/3205 : of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 2201/3207 : of an address
• CPC Class Codes: H04N 2201/3225 : of data relating to an image, a page or a document
• CPC Class Codes: H04N 2201/3226 : of identification information or the like, e.g. ID code, index, title, part of an image, reduced-size image
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3271 : Printing or stamping
• CPC Class Codes: H04N 2201/3274 : Storage or retrieval of prestored additional information
• CPC Class Codes: H04N 2201/3284 : for error correction

Abstract

The present invention relates to steganographically hiding images and information. In a preferred embodiment, an image is hidden within a media signal. The media preferably includes a cyan (C) color plane, a magenta (M) color plane, a yellow (Y) color plane and a black (K) color plane. In an alternative embodiment, the media includes a spot color. The image is converted into a black color channel image and is then applied to the media'"'"'s K channel. The black channel image is inverted and the inverted image is applied to the media'"'"'s CMY (or spot) color planes. The C, M and/or Y channels can be investigated to determine whether the image'"'"'s signal level should be modified. In a related embodiment, the media signal is segmented into a plurality of blocks and the detection level of a first embedded block is determined to be sufficient before the embedding continues to a second block. In still another embodiment, visible spectrum detection of our out-of-phase digital watermark provides a clue as to whether a printing process needs calibration or is misaligned.

Claims

1. A method of steganographically hiding a first image in a second image, the second image comprising a plurality of color channels, wherein the hiding of the first image in the second image comprises at least hiding a first image component in a first of the plurality of color channels, and, at the same second image location, hiding the component in a second of the plurality of channels, the second channel component being inverted with respect to the first channel component, said method comprising the steps of:

analyzing an attribute of at least one of the plurality of color channels; and

based on the analysis, altering the first image component prior to embedding in the first and second color channels.

2. The method of claim 1, wherein the attribute comprises luminance.

3. The method of claim 2, wherein the at least one of the plurality of color channels comprises a yellow color channel.

4. The method of claim 2, wherein the altering comprises scaling back the signal strength of at least one of the first channel component and the second channel component when the luminance equals or exceeds a predetermined threshold.

5. The method of claim 4 wherein the scaling comprises linear scaling.

6. The method of claim 4, wherein the scaling comprises non-linear scaling.

7. The method of claim 4, wherein the plurality of color channels comprises cyan, magenta, yellow and black, and the luminance of the yellow channel is analyzed.

8. The method of claim 1, wherein the attribute comprises color saturation.

9. The method of claim 8, wherein the altering comprises scaling back the signal strength of at least one of the first channel component and the second channel component when the color saturation equals or exceeds a predetermined threshold.

10. The method of claim 9, wherein the scaling comprises linear scaling.

11. The method of claim 9, wherein the scaling comprises non-linear scaling.

12. The method of claim 9, wherein the plurality of color channels comprises cyan, magenta, yellow and black, and the color saturation of the yellow channel is analyzed.

14. The method of claim 13. wherein the predetermined threshold comprises at least one of a predetermined level, an error level, and a successful detection of the digital watermark component.

15. The method of claim 13, wherein the plurality of channels comprises cyan (C), magenta (M), and yellow (Y), and wherein the first color channel comprises the Y channel, and wherein said method further comprises hiding the component in the first block in the C and M channels, the C and M channel components each being inverted with respect to the black channel component.

16. The method of claim 15 wherein the predetermined threshold comprises at least one of a predetermined level, an error level, and a successful detection of the digital watermark component.

17. The method of claim 13, wherein the first color channel comprises a spot color.

19. The method of claim 18, wherein the first color plane comprises a black color plane, the second color plane comprises yellow, and wherein the print further comprises a cyan color plane and a magenta color plane, and at the same print location as the black color plane component and the yellow color plane component, embedding the component in the cyan and magenta planes, the cyan and magenta plane components being inverted with respect to the black plane component.

20. The method of claim 18, wherein the first color plane comprises a black color plane and the second color plane comprises a spot color.

13. A method of steganographically hiding a digital watermark in an image, the image comprising a plurality of color channels including a black channel and a first color channel, said method comprising the steps of:

segmenting the image into a plurality of blocks;

hiding a first digital watermark component in the black channel of a first of the plurality of blocks;

hiding the component in the first color channel of the first block, the first channel component being inverted with respect to the black channel component;

detecting the digital watermark component; and

based on the digital watermark detection, reembedding the first block if the detection is below a predetermined threshold, and embedding a second of the plurality of blocks if the detection is above a predetermined threshold.

18. A method of monitoring a printing process, the printing process providing a print having at least a first color plane and a second color plane, wherein a digital watermark is steganographically embedded in the print by embedding at least one digital watermark component in the first color plane and, at the same print location, embedding the component in the second plane, the second plane component being inverted with respect to the first plane component, said method comprising the steps of:

capturing a visible spectrum image of the print to provide corresponding scan data;

analyzing scan data to detect the digital watermark component; and

signaling at least a printing misalignment when the digital watermark component is detected.