Method and apparatus for discerning image distortion by reference to encoded marker signals

• US 6,580,808 B2
• Filed: 02/27/2001
• Issued: 06/17/2003
• Est. Priority Date: 09/25/1995
• Status: Expired due to Fees

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Rhoads, Geoffrey B.
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US09/795,339
• Publication Number:
  US 20010016051A1
• Time in Patent Office: 840 Days
• Field of Search: 382/100, 382/112, 358/3.28, 358/448, 358/450, 380/54, 380/287, 380/231-234, 283/72, 283/73, 283/93, 283/94, 283/113, 283/901, 348/475, 235/494, 340/5.53, 340/5.6, 340/5.65, 340/5.8, 340/5.81, 340/5.83, 340/5.86, 356/71, 902/1, 902/4, 902/6, 713/176, 386/94, 705/1, 705/44
• 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 25/309 Photographs
• 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 7/1439 including a method step for retrieval of the optical code
• CPC Class Codes: G06K 7/1447 extracting optical codes from image or text carrying said optical code
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0053 Embedding of the watermark in the coding stream, possibly without decoding; Embedding of the watermark in the compressed 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: 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 1/32144 : embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• 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 1/32251 : 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 1/32352 : 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 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

Abstract

To permit scaling or rotation of an image to be discerned—even if the original image is not available—certain marker signals are steganographically encoded in the image. In one particular implementation, encoding is effected by adding an overlay signal to the image. The overlay signal—when represented in the spatial frequency domain—includes a pattern of spots. If the image is scaled or rotated, this pattern changes in known ways. By examining the change in this pattern, the distortion (i.e., scale/rotation) of the image can be inferred. This technology finds particular application in conjunction with watermarking systems, permitting recovery of watermark data from images that have been scaled or rotated subsequent to watermarking.

Claims

1. A method of processing an image that has been subject to at least one of scaling or rotation from an initial state, the method comprising:

discerning a known pattern of frequency components from a steganographic watermark in said image; and

by reference to a size or rotation of said pattern from an expected configuration, determining scaling or rotation of said image from an original state.

2. A method of steganographically decoding an encoded image to extract plural bits of auxiliary data secretly conveyed therein, characterized in that the auxiliary data can be recovered from the encoded image without reference to an unencoded image, and can be recovered even after rotation and scaling of the encoded image, the method including finding a pattern in a transform domain that corresponds to a characteristic pattern, and discerning a transformation of said found pattern from said characteristic pattern.

3. The method of claim 2 in which said transform domain is the spatial frequency domain.

4. The method of claim 2 in which the method includes use of the Fourier-Mellin transform.

5. The method of claim 2 in which said patterns comprise patterns of energy peaks in the transform domain.

6. The method of claim 2 that further includes, from said transformation, determining rotation and scaling of the encoded image.