Digital watermark insertion system and digital watermark characteristic table creating device

• US 6,415,041 B1
• Filed: 05/27/1999
• Issued: 07/02/2002
• Est. Priority Date: 06/01/1998
• Status: Expired due to Fees

• Current Assignee: National Institute of Information and Communications Technology, NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Oami, Ryoma, Miyamoto, Yoshihiro, Ohta, Mutsumi
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): NAKHJAVAN, SHERVIN K
• Application Number:
  US09/320,961
• Time in Patent Office: 1,132 Days
• Field of Search: 382/100, 382/232, 382/309, 348/460, 713/161, 713/168, 713/169, 713/170, 713/176, 713/179, 713/180, 380/23
• 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 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0202 whereby the quality of watermarked images is measured; Measuring quality or performance of watermarking methods; Balancing between quality and robustness

Abstract

The present invention relates to a digital watermark insertion system that automatically calculates a digital watermark strength suitable to an input image and inserts a digital watermark into the image. The image categorizing section 103 classifies input images and outputs category indexes. The storage device 101 stores digital watermark characteristic tables describing the correspondences between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value by category index and selects a digital watermark characteristic table to be used according to an input category index. The digital watermark strength calculation section 100 outputs a digital watermark strength to the storage device, calculates an optimum digital watermark strength using an image-quality degradation degree and a resistant evaluation value output from the storage device 103 and constraint information input by an user. The digital watermark insertion section converts embedded data into a digital watermark and inserts the digital watermark in an input image with the strength of an input optimum digital watermark strength, thus outputting a watermarked image.

Claims

1. A digital watermark insertion system, wherein digital watermark information is inserted in an image, comprising:

means for calculating feature values of input images, classifying said input images into categories with said features values, and outputting a category index;

storage means for storing digital watermark characteristic tables according to predetermined various category indexes, each of said tables describing relationships between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value, selecting a digital watermark characteristic table according to the category index of an input image, and outputting an image-quality degradation degree corresponding to an input digital watermark strength and an attack-resistant evaluation value;

digital-watermark-strength calculation means for outputting said digital watermark strength to said storage means, and deciding and outputting an optimum digital watermark strength using digital-watermark-strength constraint information to be input based on said image-quality degradation degree and said attack-resistant evaluation value output from said storage means; and

means for converting embedded data to be input into a digital watermark, inserting said digital watermark into said input image, with said optimum digital watermark strength acting as an input parameter, and outputting it as a watermarked image.

2. The digital watermark insertion system defined in claim 1, wherein said digital-watermark-strength constraint information is a permissible critical value of an image-quality degradation degree;

and wherein said digital-watermark-strength calculation means decides an optimum digital-watermark strength within a range over which an image-quality degradation degree is less than the permissible critical value of said image-quality degradation value.

3. The digital watermark insertion system defined in claim 1, wherein said digital-watermark-strength constraint information is a critical value of a safety index to attack;

and wherein said digital-watermark-strength calculation means decides an optimum digital watermark strength within a range where an attack resistant evaluation value is more than said safety index critical value.

4. The digital watermark insertion device defined in claim 1, wherein said digital-watermark-strength constraint information is a weighting index deciding a balance between an image-quality degradation degree and a safety index;

and wherein said digital-watermark-strength calculation means decides a contribution ratio by said weighting index, said contribution ratio at which said image-quality degradation degree and said safety index contributes to decide an optimum digital watermark strength.

5. The digital watermark insertion system defined in claim 1, further comprising digital-watermark-characteristic table creation means for creating a digital watermark characteristic table describing relationships between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value and for inputting a created digital watermark characteristic table to said storage means.

6. The digital watermark insertion system defined in claim 5, wherein said characteristic table creation means, comprising:

digital watermark insertion means for converting embedded information to be input into a digital watermark, and inserting said digital watermark into an input image, with a digital watermark strength to be input, whereby a watermarked image is created;

attacked-image creation means for attacking said watermarked image with an attack strength, according to an attack parameter to be input, and then creating an attacked-image;

digital watermark detection means for detecting on trial the digital watermark of said attacked image and then outputting a detection result;

image-quality calculation means for comparing said input image with said watermarked image, calculates the degree of image-quality degradation caused by digital watermark insertion, and then outputting the calculation result as an image-quality degradation amount;

image categorizing means for calculating a feature amount of said input image, classifying said input image into a category with the resultant feature amount, and outputting an category index; and

characteristic table creation means for obtaining a detection ratio by totaling a series of detection results detected to combinations of various input images and various digital watermark strengths, by category index, digital watermark strength and attack parameter;

for obtaining an image-quality amount by calculating attack-resistant evaluation values from said detection ratio by category index and digital watermark strength any by averaging said image-quality degradation amounts by category index and digital watermark strength; and

creating a digital watermark characteristic table showing corresponding relationships between digital watermark strength, said image-quality degradation degree and said attack-resistant evaluation value by category index.

7. The digital watermark insertion system defined in claim 6, wherein said characteristic table creation means comprises:

means for totaling digital watermark detection results by attack parameter, digital watermark strength and category index and then outputting detection ratio data;

means for averaging image-quality degradation amounts by category index and digital watermark strength and then for outputting an image-quality degradation degree;

means for obtaining the relationship between attack parameter and detection ratio based on an attack parameter and said detection ratio data and then calculating an resistant evaluation value; and

means for integrating digital watermark strength, said image-quality degradation degree and said resistant evaluation value and then creating a digital watermark characteristic table.

8. The digital watermark insertion system defined in claim 7, wherein said resistant evaluation value calculation means calculates a resistant evaluation value by obtaining an inner product of a function representing the change of a detection ratio for and attack parameter and a weighting function.

9. The digital watermark insertion system defined in claim 7, wherein said resistant evaluation value calculation means obtains an attack parameter range from a function representing the change for a detection ratio to an attack parameter, said attack parameter range over which said detection ratio is more than a threshold value, and decides a resistant evaluation value based on the length of said attack parameter range.

10. A computer-readable recording medium, wherein said medium records a program realizing a digital watermark insertion system, which inserts digital watermark information into an image, on a computer, comprising:

means for calculating feature amounts of an input image to classify said input image into a category with said calculated feature amounts, and outputting an category index;

storage means for previously storing an digital watermark characteristic table describing the relationships between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value by various category indexes, for selecting said digital watermark characteristic table according to the category index of said input image, and for outputting both the image-quality degradation degree corresponding to an input digital watermark strength and an attack resistant evaluation value; and

means for outputting said digital watermark strength to said storage means, deciding an optimum digital watermark strength according to said image-quality degradation degree and said resistant evaluation value output from said storage means, based on input digital watermark strength constraint information, converting embedded data into a digital watermark, and then inserting said digital watermark in said input image, with said optimum digital watermark strength acting as an input parameter, and the outputting the resultant data as a watermarked image.

11. The computer-readable recording medium, defined in claim 10, further comprising digital-watermark-characteristic table creation means for creating a digital watermark characteristic table describing relationships between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value and for inputting a created digital watermark characteristic table to said storage means.