Emergable watermark superimposing method, emergable watermark superimposing apparatus, and emergable watermark superimposing system

1. An emergable watermark superimposing method for an emergable watermark superimposing system which forms at least one of a stego still image in which a superimposition image is superimposed on a cover still image and a stego moving image containing the stego still image, comprising:

when the stego still image is reduction-processed, acquiring a position of a pixel which influences a pixel value of the stego still image after being reduction-processed, the pixel being among pixels of the stego still image prior to the stego still image being reduction-processed, the position being acquired by using a maximum integer function and inputting a reduction ratio and an integer constant to produce a maximum integer;

changing the pixel value of a pixel corresponding to the acquired position of the pixel influencing the pixel value, the pixel whose pixel value is changed being among pixels of the superimposition image, which is superimposed on the cover still image in accordance with a predetermined parameter such that the superimposition image becomes clear after being reduction-processed;

acquiring an adding/subtracting image with employment of the pixel value after the pixel value is changed; and

superimposing the adding/subtracting image on the cover still image to form the stego still image.

2. The emergable watermark superimposing method as claimed in claim 1 , further comprising:

preparing a changing strength of each of pixel positions of pixels which influence the pixel value, the changing strength corresponding to the predetermined parameter; wherein:

changing the pixel value comprises performing a calculation of a pixel value of a superimposition image and a changing strength associated with the pixel value.

3. The emergable watermark superimposing method as claimed in claim 1 , further comprising:

unclarifying a pixel value of a pixel other than the pixel which is influential such that the superimposition image becomes unclear before being reduction-processed; wherein:

acquiring the adding/subtracting image comprises acquiring the adding/subtracting image by employing the pixel after the pixel value is changed and the pixel after the unclarifying is carried out.

4. The emergable watermark superimposing method as claimed in claim 3 , wherein:

unclarifying of the pixel value comprises calculating either 0 or a random number and the pixel value of the superimposition image for pixels other than the pixel influencing the pixel value.

5. The emergable watermark superimposing method as claimed in claim 1 , wherein:

changing the pixel value comprises selecting pixel values of pixels which comprise a subject of a three-order convolution interpolation among the pixels of the superimposition image, such that a difference between pixel values of adjacent pixels of the stego still image after being reduction-processed becomes larger than a difference between the pixel values of the pixels which comprise the subject of the three-order convolution interpolation, in accordance with the predetermined parameter.

6. The emergable watermark superimposing method as claimed in claim 5 , wherein:

unclarifying the pixel value comprises selecting the pixel values of the superimposition image such that the difference between the pixel values of the pixels adjacent to each other does not become larger than a difference of original pixel values as a result of reduction based upon the three-order convolution interpolation.

7. An emergable watermark superimposing system which forms at least one of a stego still image in which a superimposition image is superimposed on a cover still image and a stego moving image containing the stego still image, comprising:

an emergable watermark superimposing server apparatus configured to:

receive the cover still image, a predetermined parameter, and the superimposition image as an input,

then, when the stego still image is reduction-processed, acquire a position of a pixel which influences a pixel value of the stego still image after being reduction-processed, the pixel being among pixels of the stego still image prior to the stego still image being reduction-processed, the position being acquired by using a maximum integer function and inputting a reduction ratio and an integer constant to produce a maximum integer,

after acquiring the position, change the pixel value of a pixel corresponding to the acquired position of the pixel influencing the pixel value, the pixel whose pixel value is changed being among pixels of the superimposition image which is superimposed on the cover still image in accordance with a predetermined parameter such that the superimposition image becomes clear after being reduction-processed,

then acquire an adding/subtracting image with employment of the pixel value after the pixel value is changed, and

superimpose the adding/subtracting image on the cover still image to form the at least one of a stego still image and the stego moving image including the stego still image, such that the at least one of the stego still image and the stego moving image is available to a plurality of client apparatuses.

8. An emergable watermark superimposing system which forms at least one of a stego still image in which a superimposition image is superimposed on a cover still image and a stego moving image containing the stego still image, comprising:

an emergable watermark superimposing server apparatus configured to provide a cover still image, a parameter, and a superimposition image to an emergable watermark superimposing client apparatus, the emergable watermark superimposing client apparatus being configured to:

when the stego still image is reduction-processed, acquire a position of a pixel which influences a pixel value of the stego still image after being reduction-processed, the pixel being among pixels of the stego still image prior to the stego still image being reduction-processed, the position being acquired by using a maximum integer function and inputting a reduction ratio and an integer constant to produce a maximum integer,

after acquiring the position, change the pixel value of a pixel corresponding to the acquired position of the pixel influencing the pixel value, the pixel whose pixel value is changed being among pixels of the superimposition image which is superimposed on the cover still image in accordance with a predetermined parameter such that the superimposition image becomes clear after being reduction-processed,

then acquire an adding/subtracting image with employment of the pixel value after the pixel value is changed, and

superimpose the adding/subtracting image on the cover still image to form the at least one of a stego still image and the stego moving image including the stego still image.

9. An emergable watermark superimposing system which forms at least one of a stego still image in which a superimposition image is superimposed on a cover still image and a stego moving image containing the stego still image, comprising:

an emergable watermark superimposing server apparatus; and

an emergable watermark superimposing client apparatus, the emergable watermark superimposing server apparatus being configured to provide a cover still image and a predetermined parameter to the emergable watermark superimposing client apparatus, wherein:

the parameter contains a character string which is employed as a superimposition image,

the emergable watermark superimposing client apparatus is configured to:

form the superimposition image from the character string provided from the emergable watermark superimposing server apparatus,

when the stego still image is reduction-processed, acquire a position of a pixel which influences a pixel value of the stego still image after being reduction-processed, the pixel being among pixels of the stego still image prior to the stego still image being reduction-processed, the position being acquired by using a maximum integer function and inputting a reduction ratio and an integer constant to produce a maximum integer,

after acquiring the position, change the pixel value of a pixel corresponding to the acquired position of the pixel influencing the pixel value, the pixel whose pixel value is changed being among pixels of the superimposition image which is superimposed on the cover still image in accordance with a predetermined parameter such that the superimposition image becomes clear after being reduction-processed,

then acquire an adding/subtracting image with employment of the pixel value after the pixel value is changed, and

superimpose the adding/subtracting image on the cover still image to form the at least one of the stego still image and the stego moving image including the stego still image.

10. An emergable watermark superimposing system which forms at least one of a stego still image in which a superimposition image is superimposed on a cover still image and a stego moving image containing the stego still image, comprising:

an emergable watermark superimposing server apparatus; and

an emergable watermark superimposing client apparatus, the emergable watermark superimposing server apparatus being configured to provide a cover still image and a predetermined parameter to the emergable watermark superimposing client apparatus, and

wherein the emergable watermark superimposing client apparatus includes a storage apparatus for storing a superimposition image therein, and is configured to:

when the stego still image is reduction-processed, acquire a position of a pixel which influences a pixel value of the stego still image after being reduction-processed, the pixel being among pixels of the stego still image prior to the stego still image being reduction-processed, the position being acquired by using a maximum integer function and inputting a reduction ratio and an integer constant to produce a maximum integer,

after acquiring the position, change the pixel value of a pixel corresponding to the acquired position of the pixel influencing the pixel value, the pixel whose pixel value is changed being among pixels of the superimposition image which is superimposed on the cover still image in accordance with a predetermined parameter such that the superimposition image becomes clear after being reduction-processed,

then acquire an adding/subtracting image with employment of the pixel value after the pixel value is changed, and

superimpose the adding/subtracting image on the cover still image to form the at least one of the stego still image and the stego moving image including the stego still image.