Image analysis – Applications
Reexamination Certificate
1998-02-24
2001-01-16
Johns, Andrew W. (Department: 2771)
Image analysis
Applications
C380S051000, C380S054000, C380S040000, C380S041000, C382S232000
Reexamination Certificate
active
06175639
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital data encode system and a water mark data inserting method for inserting water mark data in the digital data signal having a series of field data.
2. Description of the Related Art
Recently, there has arisen the necessity of developing means for preventing illegal copying of digital data, especially digital image data, with the advance of an information processor and a communication network and the electronization of various media.
Data encryption technique has been proposed as this kind of technique for preventing illegal copying. This digital data encryption technique is, for example, to enable it to reproduce the encrypted digital image data in only a reproducing system having a proper cryptoanalysis key when digital image data is encrypted. The conventional encryption technique, however, has such a defect that if the encryption code is once broken, it cannot protect against the illegally copying thereafter.
Therefore, a technique by use of water mark data is proposed, as another technique for preventing illegal copying of digital data, free from such a defect as a digital encryption technique has. Water mark data (digital water mark) is the special information to be embedded in digital image data itself in order to prevent the illegal use and copying of the digital image data. It includes, for example, information for authenticating the copyright ownership and judging the infringement of the copyright, and the copy protected information for preventing illegal copying itself.
Such water mark data to be inserted in the digital image data includes two kinds of visible water mark data and invisible water mark data. Visible water mark data means such a special character, symbol, or other data to be inserted in the image that a person who sees the image with the water mark data combined therewith may perceive the water mark visually. This kind of visible water mark data would naturally cause the deterioration of the image quality. While, it is effective in visually appealing protection against illegal copy or illegal data fluid.
A conventional visible water mark data embedding technique is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 8-241403, “Digital Watermarking Free from Image Color Change” (hereinafter, referred to as the conventional technique 1). According to the water mark data inserting method of the conventional technique 1, when combining visible water mark data with the original image data, the water mark data is combined with the original image data in a way of changing only the brightness of the pixel corresponding to the non-transparent part of the water mark data without changing the chromaticities, of all pixels of the original data. At this time, the scaling value for changing the brightness component of a pixel is determined by the value of, for example, chromatic component, random numbers, and pixels of water mark data.
Another example of the conventional visible water mark data embedding technique is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 5-236424, “Information Embedding Method and Its Apparatus” (hereinafter, referred to as the conventional technique 2). The water mark data inserting method according to the conventional technique 2 comprises detecting means for detecting a region meeting a predetermined condition from image data, thereby to embed the water mark in every image data at the position corresponding to the region meeting the condition. The position for embedding the water mark depends on the content of the image. Therefore, it is very difficult to remove the water mark without much deteriorating the image quality.
On the other hand, invisible water mark data means such special data to be inserted in the image that a person who sees the image with the water mark data combined therewith cannot perceive the water mark visually. This kind of invisible water mark data is embedded in the original image data in consideration of causing no natural deterioration of the image quality. As is understood from this, invisible water mark data is preferable to visible water mark data under the condition that a water mark preferably exists outside of the image data to be protected.
The water mark data inserting technique by use of an invisible water mark causes little image deterioration and when embedding special information enabling the identification of a writer as water mark data, it can specify the writer by detecting the water mark data even after illegal copying is performed. By embedding the copy protected information for disapproving copying or the copy prohibited information for prohibiting copying, in the original image data, and providing a reproducing device for reproducing the image data with a special function corresponding to the information, for example, it is possible to notify a user of the reproducing device that the image data is the copy inhibited data and to operate the special function within the reproducing device (copy protection function or the like) so as to restrict copying into VTR (Video Tape Recorder) when the reproducing device detects the copy protected information or the like.
As the technique of embedding the invisible water mark data in digital image, there is, for example, a technique of embedding the special information as a water mark in the digital image at the least influenced portion to the image quality in the pixel data (for example, LSB (Least Significant Bit)). This kind of the conventional invisible water mark data embedding technique is disclosed in, for example, Japanese Patent Publication Laid-Open (Kokai) No. Heisei 6-339110, “Image Information Transfer Method, Image Information Recording Device and Image Information Reproducing Device” (hereinafter, referred to as the conventional technique 3). The water mark data inserting method according to the conventional technique 3 transmits the image signal together with the copyright information and the generation information overlapping each other, to the space other than the valid image space displayed on a screen of the image signal, and performs the generation restriction of the copy according to the copyright information and the generation information included in the received image signal at a receiver side.
The invisible water mark data embedding technique, however, is defective in that only the water mark data is easily removed from the image data with water mark data embedded therein, without deteriorating the quality of the original image data. For example, the information corresponding to the LSB of the pixel data will be lost by use of a low pass filter. Generally, the image compression processing aims to reduce the data amount on the whole by diminishing the information amount with respect to the least influenced portion to the quality in the pixel data. Therefore, the water mark data embedded in the least influenced portion to the quality in the pixel data will be lost in the image compression processing. As mentioned above, the invisible water mark embedding technique has such a defect that it may be difficult to re-detect the water mark data in some cases.
Therefore, a technique of embedding invisible water mark data in a digital image as well as diffusing the water mark data into the frequency spectrum after frequency conversion of the image data (hereinafter, referred to as the conventional technique 4) is presented (refer to Nikkei Electronics p.13 (no. 660) 4.22.1996). Since water mark data is embedded in the frequency component of the image data to be processed according to the conventional technique 4, the water mark data is robust against the image compression processing and the image processing such as filtering, and the water mark data won't be lost. Further, random numbers according to the normal distribution are used as the water mark data, thereby preventing the interference of the respective water mark data even in the case of embedding a plurality of water m
Satoh Shinobu
Wakasu Yutaka
Foley & Lardner
Johns Andrew W.
NEC Corporation
Veillard Jacques
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