JP2008172519A - Information embedding device, embedded information acquisition device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information embedding device and an embedded information acquisition device whose accuracy of acquiring embedded information is hardly degraded even though an embedded document is repeatedly copied. <P>SOLUTION: The information embedding device has: a gravity center deriving means for deriving a gravity center position with respect to a predetermined direction of letters in a letter string comprised of a plurality of letters lining in the predetermined direction; a distance determining means for determining a distance between the gravity center positions derived by the gravity center deriving means of adjacent letters in the letter string; and a letter string information generating means for generating letter string information indicating the letter string in which the distance between the gravity center positions with respect to the predetermined direction of the adjacent letters in the letter string is considered to be the distance determined by the distance determining means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information embedding device and an embedding information acquisition device.

  In recent years, the importance of information security has increased. Among the information security, there is a digital watermark as a technique for preventing forgery or falsification of documents. This digital watermark is generally a technique for embedding specific information in data such as a document, an image, a moving image, and sound without affecting the original data. This specific information includes, for example, the author of the data, and this technique can prevent forgery, falsification, unauthorized copying, and the like.

Examples in which such a digital watermark is applied to a document are disclosed in Patent Documents 1 and 2. In both Patent Documents 1 and 2, information is embedded using a rectangle circumscribing a character.
Japanese Patent Laid-Open No. 2004-23566 JP 2003-230001 A

  However, in the techniques disclosed in these patent documents, information is embedded using a distance derived from a side of a circumscribed rectangle of an adjacent character, and thus “fogging” that occurs when an embedded document is repeatedly copied. When noise such as “jitter” or “jitter” is added, the S / N deteriorates and the accuracy of acquiring embedded information deteriorates.

  In view of the above problems, an object of the present invention is to provide an information embedding device and an embedded information acquiring device in which the accuracy of acquiring embedded information is unlikely to deteriorate even when a document embedded with information is repeatedly copied.

  In order to achieve the above object, the invention of claim 1 is characterized in that a centroid derivation means for deriving a centroid position of a character in a character string composed of a plurality of characters arranged in a predetermined direction with respect to the predetermined direction; A distance determining unit that determines a distance between the barycentric positions derived by the barycentric deriving unit; a distance between the barycentric positions of adjacent characters in the character string with respect to the predetermined direction; and a distance determined by the distance determining unit And character string information generating means for generating character string information indicating the character string.

  Here, in the first aspect of the invention, the centroid deriving unit derives the centroid position of the character in the character string composed of a plurality of characters arranged in a predetermined direction with respect to the predetermined direction, and the distance determining unit is adjacent to the character string. The distance between the barycentric positions derived by the barycentric derivation unit of the character is determined so that predetermined information is embedded in the character string, and the character string information generating unit is configured to centroid the adjacent character in the character string with respect to the predetermined direction. Embedded character string information indicating a character string in which the distance between the positions is the distance determined by the distance determining means is generated. For example, when copying is repeated, characters normally spread or bleed out uniformly. Even in such a case, an information embedding device is provided in which the accuracy of acquiring embedded information is unlikely to deteriorate by using a center of gravity whose position does not change. Can do.

  The present invention may further include a printing unit for printing the character string based on the character string information generated by the character string information generating unit, as in the second aspect of the invention.

  According to the present invention, as in the invention of claim 3, the character is a character in which a center of gravity position of the character with respect to the predetermined direction matches a center position of the circumscribed rectangle of the character with respect to the predetermined direction. Anyway.

  In order to achieve the above object, according to a fourth aspect of the invention, predetermined information is embedded by the information embedding device according to any one of the first to third aspects, and a character string in a character string composed of a plurality of characters arranged in a predetermined direction is used. Calculated by the centroid derivation means for deriving the centroid position with respect to the predetermined direction, the distance calculation means for calculating the distance between the centroids derived by the centroid derivation means of adjacent characters in the character string, and the distance calculation means Embedded information acquisition means for specifying the predetermined information corresponding to the distance and acquiring the predetermined information according to the specified result.

  In this case, the center-of-gravity deriving means derives the center-of-gravity position of the character in the character string composed of a plurality of characters arranged in the predetermined direction while the predetermined information is embedded by the information embedding device. The distance calculation means calculates the distance between the centroids derived by the centroid derivation means of adjacent characters in the character string, and the embedded information acquisition means corresponds to the predetermined distance corresponding to the distance calculated by the distance calculation means. And the predetermined information corresponding to the identification result is acquired. For example, when copying is repeated, characters normally spread or bleed out uniformly. Even in such a case, an embedded information acquisition device is provided in which the acquisition accuracy of embedded information is unlikely to deteriorate by using the center of gravity whose position does not change. be able to.

  The present invention may further include character string information acquisition means for acquiring the character string information from a document.

  According to the present invention, as in the invention of claim 6, the character is a character in which a center of gravity position of the character with respect to the predetermined direction matches a center position of the circumscribed rectangle of the character with respect to the predetermined direction. Anyway.

  According to the present invention, it is possible to provide an information embedding device and an embedded information acquiring device in which the accuracy of acquiring embedded information is unlikely to deteriorate.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, the information embedding device and the information acquisition device are applied to a personal computer.

  First, an information embedding device and an embedding information acquisition device will be described with reference to FIG. FIG. 1 shows a personal computer 10, a printer 32, and a scanner 34 connected via a LAN or USB. The personal computer 10 transfers character string information in which predetermined information is embedded in a character string to the printer 32. Further, the personal computer 10 acquires character string information acquired from the scanner 34 as image data of a document, and acquires embedded information from the image data.

  The printer 32 acquires character string information in which predetermined information is embedded from the personal computer 10 and performs printing based on the information. The scanner 34 reads character string information as an image from a paper document or the like, and transmits the read image as character string information to the personal computer 10 as image information.

  As shown in FIG. 1, when printing a document in which information is embedded, the personal computer 10 and the printer 32 serve as an information embedding device. Similarly, when acquiring character string information from a document, the personal computer 10 and the scanner 34 serve as an embedded information acquisition device.

  Next, the configuration of the personal computer 10 will be described with reference to FIG. The personal computer 10 includes a CPU 18, an HDD 20, a RAM 22, a network I / F unit 24, a ROM 26, a display unit 28, an operation input unit 30, and a bus 32.

  The CPU 18 governs the overall operation of the personal computer 10, and a flowchart showing processing of the personal computer 10 described later is executed by the CPU 18. The HDD 20 is a non-volatile storage device that records each database, various programs, an OS, and the like. The RAM 22 is a volatile storage device in which the OS, programs, data, and the like are expanded. The RAM 22 or the HDD 20 holds embedded information, character information, character string information, and image information read by a scanner. Therefore, these pieces of information are acquired from the RAM 22 or the HDD 20 in the flowchart described later.

  The network I / F unit 24 is for connecting to a network, and includes a NIC for connecting to a LAN and its driver, or a driver for connecting to a USB. The ROM 26 is a non-volatile storage device that stores a boot program that operates when the personal computer 10 is activated. The display unit 28 displays information related to the personal computer 10 to the operator. The operation input unit 30 is used when an operator inputs operations and information on the personal computer 10. The bus 32 is used when information is exchanged.

  The above is the configuration of the information embedding device and the embedded information acquiring device in the present embodiment. Next, an example of an embedded character string in which information is embedded will be described with reference to FIG. FIG. 3 shows an embedded character string in which three embedded information “0, 1, 0”, which is predetermined information, is embedded in a character string “Good morning”. Each character has a black dot indicating the position of the center of gravity of the character.

  In the present embodiment, when the embedded information “0” is inserted between adjacent characters, the distance between the center positions of the characters is A, and when the embedded information “1” is inserted between adjacent characters, the center of gravity of the characters. The distance between the positions is B (≠ A). The difference between the distances A and B is large when a character string is printed on a document that is highly likely to be copied repeatedly, and is small when a character string is printed on a document that is unlikely to be copied. For example, it may be determined according to the number of times of copying.

  When acquiring embedded information, if the distance between the centroid positions is A, the embedded information is “0”, and if the distance between the centroid positions is B, the embedded information is “1”. As shown in the flowchart, a threshold value is set in advance, “0” is set if the distance between the center of gravity positions is equal to or greater than the threshold value, and “1” is set if the distance is less than the threshold value. Also good.

  Since the above-described embedding information is 1 bit of “0” and “1”, the two distances A and B are used, but each embedding information can be n bits. Specifically, in the case of n bits, embedding information can be embedded and acquired by using (2 to the power of n) distances.

  Next, the gravity center position will be described. The center-of-gravity position of the character in the present embodiment uses a so-called density histogram. That is, when arranging characters horizontally, the barycentric position is indicated by a point on the X coordinate (for example, a) that is the direction in which the characters are arranged, and divided by X = a within the circumscribed rectangular area of the character The number of black dots existing in the two areas to be equalized is the same.

  This will be specifically described with reference to FIG. FIG. 4 is a diagram illustrating the barycentric position of the letter “F” and the center position described later. In the circumscribed rectangle shown in FIG. 4, the left end of the circumscribed frame is set to “0” in the X coordinate. The number of black dots in the circumscribed rectangle of the character “F” is 22. Accordingly, the number of black dots existing in the two regions divided by X = a is 11, which is 11, which is half of 22, and is 2.

  The density histogram used when deriving the centroid position can also be applied in the Y-axis direction. Therefore, the position of the center of gravity can be derived not only for a horizontally written character string but also for a vertically written character string, and thus can be applied to a vertically written document. Accordingly, it is possible to embed the embedded information in the horizontal direction of the horizontally written document and embed the embedded information in the vertical direction of the horizontally written document. Conversely, it is possible to embed the embedded information in the vertical direction of the vertically written document and embed the embedded information in the horizontal direction of the vertically written document. By embedding embedded information in two vertical and horizontal directions in this way, more embedded information can be embedded in a character string.

  In addition to the center of gravity position described above, the center position of the character may be used. The character center position uses a value obtained by dividing the number of dots in the X-axis direction of the circumscribed rectangle by two. Specifically, in the case of the character shown in FIG. 4, since the number of dots in the X-axis direction of the circumscribed rectangle is 9, X = 4.5 is the center position.

  When the center position is used, since the number of dots in the X-axis direction is simply divided by 2, the above-described calculation for deriving the center of gravity position becomes unnecessary, and the load on hardware resources such as the CPU 18 can be reduced. Become. In addition to the above-described center of gravity position or center position, a weighted average may be used.

  In the present embodiment, a font in which the position of the center of gravity is matched with the center position may be used. This will be specifically described with reference to FIG. FIG. 5 shows an example using two characters “direct” and “L”. In FIG. 5, the dotted line indicates the center position, the black circle indicates the center of gravity position, and in each of the two characters, the left character indicates a character displayed in a normal font, and the right character indicates the center position. And a font in which the center of gravity is matched.

  In a normal font, the center of gravity of each of the two characters is on the left side of the center position. For this reason, in order to obtain a font in which the center position and the center of gravity position coincide with each other, the center of gravity position is moved to the right by setting the dot indicated by the arrow as a black dot. As described above, when a font in which the centroid position matches the centroid position is used, an operation for deriving the centroid position becomes unnecessary.

  Note that “direct” and “L” shown in FIG. 5 are slightly exaggerated fonts for the sake of clarity, but normal fonts are elaborately created by the designer, so as shown in FIG. Since it is a natural font, there is no practical problem.

  Further, when the center of gravity position and the center position coincide with each other, it is possible to cope with an information embedding device and an embedding information acquisition device that can derive only one of the center of gravity position or the center position. Specifically, a document in which a character string embedded by an information embedding device capable of deriving only the center of gravity position is described, and embedding information embedded in the document is acquired by an embedding information acquisition device capable of deriving only the center position. Is possible. The reverse is of course also possible.

  Next, processing of a program executed by the CPU 18 of the personal computer 10 as the information embedding device will be described using a flowchart. In the flowchart shown below, it is expressed as “center of gravity position (center position)”, but in the description of the flowchart, it is simply expressed as “center of gravity position”.

  FIG. 7 is a flowchart showing processing for embedding information. First, the CPU 18 derives the gravity center position of the first character in step 101. The first character is, for example, “O” of “Good morning”. In the next step 102, the CPU 18 keeps the barycentric position of the character in the variable X. The variable X indicates the position on the coordinate axis in the direction in which characters are arranged on the image data. In the present embodiment, since the horizontal direction is assumed, it is a value indicating the position of the center of gravity on the X axis, which is a general horizontal coordinate axis, and a variable Y described later is a similar variable.

  In the next step 103, the CPU 18 acquires adjacent characters. The adjacent character is, for example, “ha” of “good morning”. In step 104, the CPU 18 derives the position of the center of gravity of the character, and holds the position of the center of gravity of the character in the variable Y in step 105.

  In the next step 106, the CPU 18 determines the distance D between the centroid position Y and the centroid position X of the character in order to determine the position of the character. Details of this distance determination processing will be described later.

  When acquiring the distance D, the CPU 18 generates character string information separated from the X to Y by the distance D in step 107. The character string information is, for example, data described in PostScript or raster data, and is character string information in which the center of gravity position of the character is separated by the distance acquired by the distance acquisition process.

  In the next step 108, the CPU 18 substitutes the center-of-gravity position held in the variable Y for the variable X. In step 109, the CPU 18 determines whether or not the generation of the character string information is finished, and makes an affirmative determination. In step 110, the character string information is transferred to the printer. If a negative determination is made, the processing in step 104 is executed again.

  Next, the distance determination process will be described with reference to the flowchart of FIG. In step 201, the CPU 18 acquires embedded information. This embedded information is “0” or “1” in the present embodiment. In the next step 202, the process branches depending on the acquired embedded information. When the embedded information is “0”, the CPU 18 sets the distance D between the gravity center positions to A in step 203. On the other hand, if the embedded information is “1”, the CPU 18 sets the distance D between the gravity center positions to B in step 204. Here, the distances A and B may be different values.

  The CPU 18 returns the distance D thus determined as a return value in step 205.

  Next, processing of a program executed by the CPU 18 of the personal computer 10 as the embedded information acquisition device will be described using a flowchart. This process is a process executed on the character obtained by the character recognition process from the image information indicating the character string read by the scanner 34.

  FIG. 9 is a flowchart showing a process for acquiring embedded information. First, the CPU 18 reads the first character in step 301, derives the barycentric position of the read character in step 302, and holds the barycentric position of the character in the variable X in step 303. Here, the first character is “o” when the character string is “good morning”, for example.

  In step 304, the CPU 18 reads adjacent characters. The adjacent character is, for example, “ha” of “good morning”. In step 305, the CPU 18 derives the center of gravity position of the character, and in step 306 holds the center of gravity position of the character in the variable Y.

  In the next step 307, the CPU 18 calculates the distance between the centroid position of the character and the centroid position of the previously read character in order to obtain embedded information. Details of this distance calculation processing will be described later.

  In step 308, the CPU 18 acquires embedded information obtained by the distance calculation process. In the next step 309, the CPU 18 substitutes the variable X for the position of the center of gravity of the character read in step 304.

  In step 310, the CPU 18 determines whether or not all characters have been read. If the determination is affirmative, the CPU 18 displays the acquired embedded information and ends the process. Execute the process. The display in step 311 may be performed by converting the acquired embedded information into ASCII characters, for example, or may be recorded without being displayed, for example, as a file.

  Next, the distance calculation process will be described with reference to the flowchart of FIG. In this flowchart, A <B. In step 401, the CPU 18 calculates a distance D between the gravity center positions X and Y. Next, in step 402, the CPU 18 compares D and (A + B) / 2 in order to determine whether the distance D is closer to A or B, and D <(A + B) / 2 (D In step 404, the embedding information E is specified as “0”. On the other hand, if the CPU 18 makes a negative determination in step 402, the embedded information E is specified as “1” in step 403.

  In step 405, the CPU 18 returns the embedded information E specified in this way as a return value.

  In step 404, the embedded information acquisition accuracy may be improved by adding a branching process such as rereading the character when D = (A + B) / 2.

  Next, an embodiment in which two fonts having different centroid positions for each font are prepared in advance, unlike the embodiment described above. Specifically, as shown in FIG. 11, two fonts having different centroid positions are a font having a centroid position on the left of the center line (hereinafter, left font) and a font having a centroid position on the right of the center line ( Hereinafter, the right font) is shown. Thus, the left font and the right font are prepared in advance for each character. In the figure, the center-of-gravity position is distinguished on the left and right, but may be distinguished on the top and bottom, or on the basis of whether or not it exists at a specific position.

  When such a font is used, information can be embedded for each character instead of the distance between two adjacent characters as in the above embodiment. Specifically, for example, by setting “0” for the left font and “1” for the right font, information can be embedded for each character.

  In this way, when two fonts with different centroid positions are used, even if a document in which information is embedded is repeatedly copied, it is highly likely that the centroid position still exists on the left and right. Accuracy is unlikely to deteriorate.

  In the embodiment described above, the information embedding device having the function of printing the character string information is realized by the personal computer 30 and the printer 32. However, the information embedding device may be an image forming apparatus such as a multifunction machine having a printer function. it can. Similarly, an embedded information acquisition apparatus having a function of reading a document is realized by the personal computer 30 and the scanner 34, but may be an image forming apparatus such as a multifunction peripheral having a scanner function.

  Furthermore, an information embedding device and an embedding information acquisition device can also be realized by an image forming apparatus such as a multifunction peripheral having a printer function and a scanner function and a personal computer connected thereto.

  As described above, in the present embodiment, centroid deriving means (step 101) for deriving the centroid position of a character in a character string composed of a plurality of characters arranged in a predetermined direction with respect to the predetermined direction, and an adjacent character string in the character string. Distance determining means (step 106) for determining the distance between the centroid positions derived by the centroid derivation means for the character, and the distance determining means for determining the distance between the centroid positions of the adjacent characters in the character string with respect to the predetermined direction. And character string information generating means (step 107) for generating character string information indicating the character string determined as the distance determined in (1).

  For example, when copying is repeated, characters normally spread or bleed out uniformly. Even in such a case, an information embedding device is provided in which the accuracy of acquiring embedded information is unlikely to deteriorate by using a center of gravity whose position does not change. Can do.

  In the present embodiment, as described above, the printer may further include a printing unit (printer 32) that prints the character string based on the character string information generated by the character string information generating unit.

  In the present embodiment, as described above, the character is a character (see FIG. 5) in which the center of gravity of the character in the predetermined direction matches the center position of the circumscribed rectangle of the character in the predetermined direction. Anyway.

  Further, in the present embodiment, predetermined information is embedded by the information embedding device, and the center-of-gravity deriving means for deriving the center-of-gravity position of the character in the predetermined direction in the character string composed of a plurality of characters arranged in the predetermined direction (step 302) Distance calculating means (step 307) for calculating the distance between the centroids derived by the centroid derivation means for adjacent characters in the character string; and the predetermined information corresponding to the distance calculated by the distance calculating means And embedded information acquisition means (step 308) for acquiring the predetermined information according to the specified result.

  For example, when copying is repeated, characters normally spread or bleed out uniformly. Even in such a case, an embedded information acquisition device is provided in which the acquisition accuracy of embedded information is unlikely to deteriorate by using the center of gravity whose position does not change. be able to.

  In the present embodiment, as described above, the character string information acquisition unit (scanner 34) that acquires the character string information from the document may be further included.

  In the present embodiment, as described above, the character is a character (see FIG. 5) in which the center of gravity of the character in the predetermined direction matches the center position of the circumscribed rectangle of the character in the predetermined direction. There may be.

It is a figure which shows the structure of an information embedding apparatus and an embedding information acquisition apparatus. It is a figure which shows the structure of a personal computer. It is a figure which shows the document which embedded the embedded information in the character. It is a figure which shows the gravity center position and center position of character "F". It is a figure which shows the font which made the gravity center position correspond to a center position. It is a figure which shows the example of a font. It is a flowchart which shows the process which embeds information. It is a flowchart which shows a distance determination process. It is a flowchart which shows the process which acquires embedding information. It is a flowchart which shows a distance calculation process. It is a figure which shows the font from which a gravity center position differs.

Explanation of symbols

10 PC 18 CPU
20 HDD
22 RAM
32 Printer 34 Scanner

Claims (6)

Centroid derivation means for deriving the centroid position of the character in the predetermined direction in a character string composed of a plurality of characters arranged in a predetermined direction;
Distance determining means for determining a distance between centroid positions derived by the centroid derivation means of adjacent characters in the character string;
Character string information generating means for generating character string information indicating a character string with the distance between the centroid positions of adjacent characters in the character string in the predetermined direction as the distance determined by the distance determining means;
An information embedding device.   The information embedding apparatus according to claim 1, further comprising a printing unit that prints the character string based on the character string information generated by the character string information generation unit.   The information embedding apparatus according to claim 1, wherein the character is a character in which a center of gravity position of the character with respect to the predetermined direction matches a center position of the circumscribed rectangle of the character with respect to the predetermined direction. Center of gravity deriving means for deriving the center of gravity of the character in the predetermined direction in a character string composed of a plurality of characters arranged in a predetermined direction while the predetermined information is embedded by the information embedding device according to claim 1;
Distance calculating means for calculating a distance between centroids derived by the centroid derivation means of adjacent characters in the character string;
Embedded information acquisition means for specifying the predetermined information corresponding to the distance calculated by the distance calculation means, and acquiring the predetermined information according to the specification result;
Embedded information acquisition apparatus.   The embedded information acquisition apparatus according to claim 4, further comprising character string information acquisition means for acquiring the character string information from a document.   The embedded information acquisition apparatus according to claim 4, wherein the character is a character in which a center of gravity position of the character with respect to the predetermined direction matches a center position of the circumscribed rectangle of the character with respect to the predetermined direction.

Images