Digital watermark embedding and detection
AssigneeFujitsu Limited
InventorsKensuke Kuraki, Taizo Anan
Life of this patent
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Abstract
Provided is a digital watermarking technology for embedding digital watermark information in text data thereby to generate a digitally watermarked image. The technology includes a digital watermarking program, a digital watermarking device and a digital watermarking method, in which digital watermark information can be embedded in document in such a way as not to be easily detected visually and be stably detected even after being printed out, copied or scanned by detecting the features of a character as data to be digitally watermarked, such as the direction and thickness of a line composing the character as the features thereof and embedding the digital watermark information in the character on the basis of the detected features.
Claims20
A non-transitory computer-readable medium storing a digital watermarking program for enabling a computer to embed digital watermark information in text data to generate a digitally watermarked image, the program causing the computer to execute a method comprising:
- detecting local line thickness at each pixel on lines composing a character from embedding target data with respect to each of a predetermined set of the directions;
- determining character line thickness for said character with respect to each of said predetermined set of the directions from said local line thickness as features of said character;
- and
- embedding digital watermark information in said character by using a ratio of character line thicknesses for said character in at least two of said predetermined set of directions.
A non-transitory computer-readable medium storing a digital watermark extraction program for enabling a computer to detect the digital watermark information from a digitally watermarked image in which digital watermark information is embedded, the program causing the computer to execute a method comprising:
- inputting the digitally watermarked image;
- detecting a text area composed of characters from a digitally watermarked image inputted by said inputting;
- extracting a character from the text area detected by said detecting;
- analyzing said character to obtain directions of lines composing said character and character line thickness of said character with respect to each of said directions;
- and
- extracting digital watermark information embedded in the character by calculating a ratio of the character line thicknesses of said character with respect to at least two of said directions.
A digital watermarking device for embedding digital watermark information in text data to generate a digitally watermarked image, comprising:
- a feature detection unit for detecting local line thickness at each pixel on lines composing a character from embedding target data with respect to each of a predetermined set of the directions and for determining character line thickness for said character with respect to each of said predetermined set of the directions from said local line thickness as features of said character;
- and
- an information embedding unit for embedding digital watermark information in said character by using a ratio of character line thicknesses for said character in at least two of said predetermined set of directions.
A digital watermark detection device for detecting the digital watermark information from a digitally watermarked image in which digital watermark information is embedded, comprising:
- an image input unit for inputting the digitally watermarked image;
- a text area detection unit for detecting a text area composed of characters from a digitally watermarked image inputted by the image inputting unit;
- a character extraction unit for extracting a character from the text area detected by the text area detection unit;
- a structure analysis unit for analyzing said character to obtain directions of lines composing said character and character line thickness of said character with respect to each of said directions;
- and
- an information extraction unit for extracting digital watermark information embedded in the character by calculating a ratio of the character line thicknesses of said character with respect to at least two of said directions.
A digital watermarking method implemented in a digital watermarking device for embedding digital watermark information in text data to generate a digitally watermarked image, comprising:
- detecting local line thickness at each pixel on lines composing a character from embedding target data with respect to each of a predetermined set of the directions;
- determining character line thickness for said character with respect to each of said predetermined set of the directions from said local line thickness as features of said character;
- and
- embedding digital watermark information in said character by using a ratio of character line thicknesses for said character in at least two of said predetermined set of directions.
A digital watermark extraction method implemented in a digital watermarking device for embedding digital watermark information in text data to generate a digitally watermarked image, comprising:
- inputting the digitally watermarked image;
- detecting a text area composed of characters from a digitally watermarked image inputted by the inputting;
- extracting a character from the text area detected by the detecting;
- analyzing said character to obtain directions of lines composing said character and character line thickness of said character with respect to each of said directions;
- and
- extracting digital watermark information embedded in the character by calculating a ratio of the character line thicknesses of said character with respect to at least two of said directions.
Dependencies are inferred from the claim text.