Image processor and image processing method

• US 6,959,385 B2
• Filed: 04/04/2001
• Issued: 10/25/2005
• Est. Priority Date: 04/07/2000
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ishida, Yoshihiro, Murakami, Tomochika, Iwamura, Keiichi
• Primary Examiner(s): Zand, Kambiz
• Application Number:
  US09/824,746
• Publication Number:
  US 20020002679A1
• Time in Patent Office: 1,665 Days
• Field of Search: 713/176, 380/379, 380/46, 380/216, 380/259, 380/263, 382/279, 382/280, 382/285, 382/289, 382/293, 382/296
• US Class Current: 713/176
• CPC Class Codes: G06F 21/16 Program or content traceability, e.g. by watermarking
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: G06V 10/431 Frequency domain transformation; Autocorrelation
• CPC Class Codes: H04N 1/32149 Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/3216 using Fourier transforms
• 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 2201/327 which are undetectable to the naked eye, e.g. embedded codes

Abstract

To provide a device capable of determining uniquely the direction of rotation applied to an image and extracting digital watermark information correctly even in the case where a registration signal having a symmetric axis is embedded. A device for enabling digital watermark information to be extracted from image data having the digital watermark information embedded therein in such a manner that it can hardly be perceived by human eyes, in which processing for extracting rotation information and position information from the image data is performed plural times for rotation angles different from one another. For extracted position and rotation information, confidence coefficients indicating accuracy thereof are calculated. The position and rotation angle at which the digital watermark information is embedded are determined based on the confidence coefficients.

Claims

1. An image processor comprising:

means for embedding in image data a digital watermark comprising an irrotationally symmetric pattern arrangement and position and rotation information;

rotation information searching means for performing processing for extracting said rotation information from the image data with said digital watermark information embedded therein, for a plurality of rotation angles different from one another;

position information searching means for performing processing for extracting said position information from said image data, for a plurality of start-of-extraction positions different from one another;

calculating means for calculating confidence coefficients indicating the accuracy with which said position and rotation information is extracted, for each information searched by said rotation information searching means and position information searching means and extracted as position and rotation information; and

determining means for determining the position and rotation angle at which said digital watermark information is embedded in said image data, based on the confidence coefficient calculated by said calculating means.

2. The image processor according to claim 1,

wherein said irrotationally symmetric pattern arrangement is a two-dimensional matrix comprising m×

n elements.

3. The image processor according to claim 1,

wherein said irrotationally symmetric pattern arrangement is a pattern arrangement for which the positive or negative symbols of corresponding elements are not wholly the same if the patten arrangement is rotated at an arbitrary angle, except for angles of 360 degrees multiplied by an integer number.

4. An image processor capable of extracting digital watermark information from image data in which said digital watermark information including position and rotation information is embedded, comprising:

rotation information searching means for performing processing for extracting said rotation information from the image data with said digital watermark information embedded therein, for a plurality of rotation angles different from one another;

position information searching means for performing processing for extracting said position information from said image data, for a plurality of start-of-extraction positions different from one another;

calculating means for calculating confidence coefficients indicating the accuracy with which said position and rotation information is extracted, for each information searched by said rotation information searching means and position information searching means and extracted as position and rotation information; and

determining means for determining the position and rotation angle at which said digital watermark information is embedded in said image data, based on the confidence coefficient calculated by said calculating means.

5. The image processor according to claim 4,

wherein said digital watermark information includes said position information and rotation information and usage information, and

wherein said usage information includes the ID of a device or the user ID.

6. The image processor according to claim 4,

wherein said digital watermark information includes said position information and rotation information and usage information, and

wherein said usage information includes information for controlling a device.

7. The image processor according to claim 4,

wherein said calculating means calculates confidence coefficients by performing computation of said image data with a matrix comprising m×

n coefficients.

8. The image processor according to claim 7,

wherein said matrix computation processing is convolution computation.

9. The image processor according to claim 4, further comprising:

extracting means for extracting the digital watermark information embedded in said image data, based on its position in said image data on the basis of the result of determination by said determining means.

10. An image processing method comprising:

an embedding step of embedding in image data digital watermark information comprising an irrotationally symmetric pattern arrangement, and including position and rotation information;

a rotation information searching step for performing processing for extracting the rotation information from the image data with the digital watermark information embedded therein, for a plurality of rotation angles different from one another;

a position information searching step for performing processing for extracting the position information from the image data, for a plurality of start-of-extraction positions different from one another;

a calculating step for calculating confidence coefficients indicating the accuracy with which the position and rotation information is extracted, for each information searched by said rotation information searching step and said position information searching step and extracted as position and rotation information; and

a determining step for determining the position and rotation angle at which the digital watermark information is embedded in the image data, based on the confidence coefficient calculated by said calculating step.

11. An image processing method of extracting digital watermark information from image data in which the digital watermark information including position and rotation information is embedded, comprising:

a rotation information searching step of performing processing for extracting the rotation information from the image data with the digital watermark information embedded therein, for a plurality of rotation angles different from one another;

a position information searching step of performing processing for extracting the position information from the image data, for a plurality of start-of-extraction positions different from one another;

a calculating step of calculating confidence coefficients indicating the accuracy with which the position and rotation information is extracted, for each information searched in said rotation information searching step and position information searching step and extracted as position and rotation information; and

a determining step of determining the position and rotation angle at which the digital watermark information is embedded in the image data, based on the confidence coefficient calculated in said calculating step.

12. A computer program product embodying a program comprising:

program codes for implementing an image processing method of embedding in image data, digital watermark information comprising an irrotationally symmetric pattern arrangement and position and rotation information;

program codes for a rotation information searching step for performing processing for extracting the rotation information from the image data with the digital watermark information embedded therein, for a plurality of rotation angles different from one another;

program codes for a position information searching step for performing processing for extracting the position information from the image data, for a plurality of start-of-extraction positions different from one another;

program codes for a calculating step for calculating confidence coefficients indicating the accuracy with which the position and rotation information is extracted, for each information searched by the rotation information searching step and position information searching step and extracted as position and rotation information; and

program codes for a determining step for determining the position and rotation angle at which the digital watermark information is embedded in the image data, based on the confidence coefficient calculated by said calculating step.

13. A computer program product embodying a program for implementing an image processing method of extracting digital watermark information from image data in which said digital watermark information including position and rotation information is embedded,

the program comprising:

program codes for a rotation information searching step of performing processing for extracting the rotation information from the image data with the digital watermark information embedded therein, for a plurality of rotation angles different from one another;

program codes for a position information searching step of performing processing for extracting the position information from the image data, for a plurality of start-of-extraction positions different from one another;

program codes for a calculating step of calculating confidence coefficients indicating the accuracy with which the position and rotation information is extracted, for each information searched in the rotation information searching step and position information searching step and extracted as position and rotation information; and

program codes for a determining step of determining the position and rotation angle at which the digital watermark information is embedded in the image data, based on the confidence coefficient calculated in the calculating step.

14. A computer data signal embodied in a propagating wave comprising:

code signals for use in implementing an image processing method of embedding in image data, digital watermark information comprising an irrotationally symmetric pattern arrangement and position and rotation information;

code signals for use in a rotation information searching step for performing processing for extracting the rotation information from the image data with the digital watermark information embedded therein, for a plurality of rotation angles different from one another;

code signals for use in a position information searching step for performing processing for extracting the position information from the image data, for a plurality of start-of-extraction positions different from one another;

code signals for use in a calculating step for calculating confidence coefficients indicating the accuracy with which the position and rotation information is extracted, for each information searched by the rotation information searching step and the position information searching step and extracted as position and rotation information; and

code signals for use in a determining step for determining the position and rotation angle at which the digital watermark information is embedded in the image data, based on the confidence coefficient calculated by the calculating step.

15. A computer data signal embodied in a propagating wave and used for implementing an image processing method of extracting digital watermark information from image data in which the digital watermark information including position and rotation information is embedded comprising:

code signals for use in a rotation information searching step of performing processing for extracting the rotation information from the image data with the digital watermark information embedded therein, for a plurality of rotation angles different from one another;

code signals for use in a position information searching step of performing processing for extracting the position information from the image data, for a plurality of start-of-extraction positions different from one another;

code signals for use in a calculating step of calculating confidence coefficients indicating the accuracy with which the position and rotation information is extracted, for each information searched in the rotation information searching step and the position information searching step and extracted as position and rotation information; and

code signals for use in a determining step of determining the position and rotation angle at which the digital watermark information is embedded in the image data, based on the confidence coefficient calculated in the calculating step.