JP2015089070A - Information embedding device for document file - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information embedding device for a document file, which can embed large capacity data such as a character and an image in an invisible state and can extract information embedded only by browsing software that is generally spread without using a private extraction tool while deterioration of quality of an original document is suppressed.SOLUTION: An information embedding device includes: additional information arranging means 10 for arranging a raster image or additional information of a character code format in an image region where a vector image is previously arranged in a document file; display priority changing means 20 for changing display priority of the additional information so that it is arranged in a low order by lowering it compared to that of the vector image which is previously arranged; and document format converting means 30 for converting the document file whose display priority is changed by the display priority changing means 20 into an embedded document file in a prescribed format so that the additional information can be extracted and the vector image cannot be extracted when the document file after embedding is browsed.

Description

  The present invention relates to a technique for embedding information in a document file such as PDF (Portable Document Format: registered trademark).

  In recent years, PDF document files have come to be used as official documents such as contracts, and security functions can be electronically stamped or encrypted with a document to control opening, printing, editing, etc. with a password. Can be added. However, once a password is obtained and can be opened, there may be a problem that an inexhaustible copy is created, so that tracking with a digital watermark is also necessary. Although a technique for embedding a visible digital watermark in a PDF document has also been developed (see Patent Document 1), a technique for embedding an invisible digital watermark has not been developed, and an invisible digital watermark is embedded in individual images to be laid out. However, there was only means.

  As a method of adding invisible information to a PDF document, there is a method of arranging transparent text (see Patent Document 2), but the text that can be arranged is recognized by OCR processing for raster format character data arranged in the PDF. There was a problem that it was limited to the character string that was made. In addition, image data or document data can be attached to a PDF document as an attached file. However, since it is clearly indicated that it is attached on browsing software such as a PDF reader, it cannot be said that it is embedded in an invisible state.

Japanese Patent No. 4698535 Japanese Patent No. 4383157

  On the other hand, invisible digital watermark technology for images and texts, there are problems of modifying and degrading the quality of the original content, problems of embedding large amounts of data such as image data due to restrictions on the amount of embedded information, There was a problem that extraction was not possible if dedicated extraction software corresponding to the embedding method was not available.

  Therefore, the present invention can embed a large amount of data such as characters and images in an invisible state while suppressing deterioration of the quality of the original document, and only using popular browsing software without using a dedicated extraction tool. It is an object of the present invention to provide an information embedding device for a document file from which embedded information can be extracted.

  In order to solve the above-mentioned problem, in the first aspect of the present invention, an apparatus for recording invisible additional information including at least one of a raster image or a character code format character on a document file in which a vector image is arranged. The additional information arrangement means for arranging the additional information in the image area in which the vector image is arranged in advance in the document file, and the display priority of the additional information in the vector image arranged in advance. The display priority changing means for changing the display priority to be lower than the display priority, and the additional information can be extracted at the time of browsing the embedded document file, and the vector image cannot be extracted. Document format conversion means for converting a document file whose display priority has been changed by the display priority changing means to a predetermined format. Providing information embedding apparatus for document files, wherein.

  According to the first aspect of the present invention, raster image or character code format additional information is arranged in an image area in which a vector image is arranged in advance in a document file, and the display priority of the additional information is arranged in advance. The document file is changed so that it is placed below the display priority of the current vector image, and additional information can be extracted and the vector image cannot be extracted when browsing the embedded document file. Since it is converted to this format, it is possible to embed raster images and character codes in an invisible state under the vector image while suppressing degradation of the quality of the original document, and it is generally popular without using a dedicated extraction tool. The embedded raster image and character code can be extracted by viewing software.

  In the second aspect of the present invention, in the information embedding device for the document file according to the first aspect of the present invention, the additional information arrangement means includes an image in which conversion to a vector format is specified in the document file. In this case, the image is converted into a vector format to obtain the vector image.

  According to the second aspect of the present invention, when an image designated to be converted to the vector format exists in the document file, the image is converted to the vector format to obtain a vector image. At the time of browsing, it is possible to prevent an image of a raster format or the like existing in the original document file from being extracted.

  According to a third aspect of the present invention, in the information embedding device for the document file according to the first or second aspect of the present invention, the vector image is uniformly painted with the same color as the background color. And

  According to the third aspect of the present invention, since the vector image arranged in the document file is uniformly painted with the same color as the background color, additional information seems to be hidden in the background for the viewer. Only the person who knows the presence of the additional information can extract the embedded raster image or character code by the viewing software.

  According to a fourth aspect of the present invention, there is provided an apparatus for recording additional information in a character code format in an invisible state with respect to a document file in which characters are arranged, wherein the characters are arranged in advance in the document file. An additional information arrangement means for arranging the additional information in a background color of the document file in a character area including the existing character area, and lowering the display priority of the additional information from the display priority of the characters arranged in advance. Display priority changing means for changing to be arranged at a lower position, and the display priority so that the additional information can be extracted and characters arranged in advance cannot be extracted when the embedded document file is viewed. Document format conversion means for converting a document file whose display priority has been changed by the changing means into a predetermined format, and To provide a multi-address embedded devices.

  According to the fourth aspect of the present invention, the additional information in the character code format is arranged in the background color of the document file in the character area including the character area where the character is arranged in advance in the document file, and the additional information is displayed. Changed the priority so that it is placed lower than the display priority of characters placed in advance, so that additional information can be extracted when embedding the document file, and characters placed in advance cannot be extracted. As described above, since the document file is converted into a predetermined format, it is possible to embed additional information in the character code format under the characters in an invisible state while suppressing deterioration of the quality of the original document. It is possible to extract the embedded character code when attempting to duplicate characters by using popular browsing software without using. By making the additional information in the character code format the background color of the document file, even when characters overlap, the additional information becomes invisible in the background when viewed.

  According to a fifth aspect of the present invention, there is provided an apparatus for recording additional information in a character code format in an invisible state with respect to a document file in which characters are arranged, wherein characters are arranged in advance in the document file. An additional information arrangement means for arranging the additional information in a background color of the document file in the character area included in the existing character area, and lowering the display priority of the additional information from the display priority of the character arranged in advance. Display priority changing means for changing the display information to be arranged at a lower level, and the display priority so that the additional information cannot be extracted and characters arranged in advance can be extracted when the embedded document file is viewed. Document format conversion means for converting a document file whose display priority has been changed by the degree change means into a predetermined format. To provide information embedding device.

  According to the fifth aspect of the present invention, the additional information in the character code format is arranged in the background color of the document file in the character area included in the character area in which characters are arranged in advance in the document file, and the additional information Changed the display priority to be lower than the display priority of pre-arranged characters, so that additional information can not be extracted when browsing a document file after embedding, and pre-arranged characters can be extracted As described above, since the document file is converted into a predetermined format, additional information in the character code format cannot be extracted under the characters while suppressing deterioration of the quality of the original document. It is possible to extract the displayed character code when attempting to duplicate characters by using popular browsing software without using. By making the additional information in the character code format the background color of the document file, even when characters overlap, the additional information becomes invisible in the background when viewed.

  According to a sixth aspect of the present invention, there is provided an apparatus for recording additional information in a raster image format in an invisible state with respect to a document file in which a raster image is arranged, wherein the additional information is previously arranged in the raster image. The additional information arrangement means for arranging the image information area and the display priority of the additional information are set lower than the display priority of the raster image arranged in advance so that the image area is at least partially overlapped. Display priority changing means for dividing the raster image into a plurality of areas, and the display priority so that the raster image divided into the plurality of areas can be extracted when browsing the embedded document file. Document format conversion means for converting the document file whose display priority has been changed by the degree change means into a predetermined format. Providing information embedding apparatus for a document file.

  According to the sixth aspect of the present invention, the additional information in the raster image format is arranged so as to at least partially overlap the image area where the raster image is arranged in advance, and the display priority of the additional information is arranged in advance. The raster image is changed to be arranged lower than the display priority of the existing raster image, and the raster image is divided into a plurality of regions, and the raster image divided into the plurality of regions can be extracted when browsing the embedded document file. As described above, since the document file is converted into a predetermined format, it is possible to embed the raster image in an invisible state under the raster image while suppressing deterioration of the quality of the original document, and use a dedicated extraction tool. First, it is difficult to extract already-arranged raster images by using popular viewing software.

  Further, in the seventh aspect of the present invention, three types of objects, vector images, raster images, and characters, can be used, and at least two or more objects of different types or the same type are overlapped with a display priority set. A document file that can be recorded and that can extract multiple objects with different display priorities corresponding to the specified position, and the display information is recorded as the object with the highest display priority and is invisible. Provided is an embedded document file in which additional information to be embedded is recorded as an object having a display priority lower than that of the display information.

  According to the seventh aspect of the present invention, three types of objects, a vector image, a raster image, and a character, can be used, and at least two or more objects of different types or the same type are overlapped with a display priority set. A document file that can be recorded and that can extract multiple objects with different display priorities corresponding to the specified position, and the display information is recorded as the object with the highest display priority and is invisible. Since the additional information to be embedded is recorded as an object having a lower display priority than the information for display, the additional information embedded in an invisible state is acquired by selecting the displayed object, and the user Can be given unexpected surprises and attention.

  According to the present invention, it is possible to embed a large amount of data such as characters and images in an invisible state while suppressing deterioration of the quality of the original document, and only using popular browsing software without using a dedicated extraction tool. The embedded information can be extracted.

It is a hardware block diagram of the information embedding apparatus with respect to the document file which concerns on one Embodiment of this invention. It is a functional block diagram of an information embedding device for a document file according to an embodiment of the present invention. It is a flowchart which shows the process outline | summary of the information embedding apparatus with respect to the document file which concerns on one Embodiment of this invention. It is a figure which shows an example of the document file before embedding additional information. It is a figure which shows the state of the document file after arrange | positioning a raster image on a vector image. It is a figure which shows the state of the document file after arrangement | positioning of the character string with a large area | region superimposed on a character string. It is a figure which shows the state of the document file after arrangement | positioning of the character string with a small area | region superimposed on a character string. It is a figure which shows the state of the document file after arrange | positioning a raster image on a raster image. It is a figure which shows the state of the document file after a display priority change. It is a figure which shows the extraction propriety by the PDF reader at the time of an object superimposition. It is a flowchart which shows the extraction process of additional information at the time of using browsing software. It is a flowchart which shows the extraction process of additional information at the time of using edit software. It is a figure which shows the example of application which embedded the password character string in the PDF document. It is a display example of a document file before additional information is arranged. It is an example of a display of the character string and raster image which are additional information. 15 is a display example of a document file in a state where the additional information shown in FIG. 15 is arranged in the document file shown in FIG. It is a display example of a document file in a state in which the display priority of additional information is changed. The display example in FIG. 17 is obtained by removing a rectangle indicating an object area. It is a display example by the browsing software of the obtained embedded document file. It is a figure which shows the example from which the character string was extracted. It is a figure which shows the example from which the raster image was extracted. It is a figure which shows the example from which the character string was extracted from both the overlapping character strings. It is a figure which shows the example from which the raster image was extracted from the background same color area | region.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
<1. Device configuration>
FIG. 1 is a hardware configuration diagram of an information embedding device for a document file according to an embodiment of the present invention. An information embedding apparatus for a document file according to the present embodiment can be realized by a general-purpose computer. As shown in FIG. 1, a CPU (Central Processing Unit) 1 and a RAM (Random Access Memory) which is a main memory of the computer. ) 2, a large-capacity storage device 3 such as a hard disk or flash memory for storing programs and data executed by the CPU 1, a key input I / F (interface) 4 such as a keyboard and a mouse, a data storage medium, etc. A data input / output I / F (interface) 5 for data communication with the external device and a display unit 6 which is a display device such as a liquid crystal display are connected to each other via a bus.

  FIG. 2 is a functional block diagram showing the configuration of the information embedding device for the document file according to this embodiment. In FIG. 2, 10 is an additional information arrangement unit, 20 is a display priority changing unit, 30 is a document format conversion unit, 40 is a document file storage unit, 50 is an additional information storage unit, and 60 is an embedded document file storage unit.

  The additional information arrangement unit 10 arranges the designated additional information in the additional information storage unit 50 at a designated position in the document file. The additional information is text or image information that is added to the originally recorded information and embedded in the document file. In the present embodiment, as additional information, characters are in a character code format and images are in a raster (bitmap) format. The display priority changing means 20 changes the display priority of the additional information so as to be placed lower than other placement objects. The document format conversion means 30 converts the format of the document file in which the additional information is embedded, and creates an embedded document file of a predetermined format.

  The document file storage unit 40 is a storage unit that stores a document file that can be processed by a computer, and is realized by the storage device 3. The additional information storage unit 50 is a storage unit that stores additional information to be embedded in the document file, and is realized by the storage device 3. The embedded document file storage unit 60 is a storage unit that stores an embedded document file in which additional information is embedded in the original document file and the document format is converted, and is realized by the storage device 3. . Various types of embedded document files can be used. In this embodiment, the PDF format, which is a general-purpose format, is used. The additional information arrangement unit 10, the display priority change unit 20, and the document format conversion unit 30 are realized by the CPU 1 executing a program stored in the storage device 3.

  Each component shown in FIG. 2 is actually realized by mounting a program on hardware such as a computer and its peripheral devices as shown in FIG. That is, the computer executes the contents of each means according to the program. Note that in this specification, a computer means a device that has an arithmetic processing unit such as a CPU and is capable of data processing.

  The storage device 3 shown in FIG. 1 is mounted with a program for operating the CPU 1 and causing the computer to function as an information embedding device for document files. By executing this program, the CPU 1 realizes functions as the additional information arranging unit 10, the display priority changing unit 20, and the document format converting unit 30. The storage device 3 not only functions as the document file storage unit 40, the additional information storage unit 50, and the embedded document file storage unit 60, but also stores various data necessary for processing as an information embedding device for the document file. .

<2. Processing action>
Next, the processing operation of the information embedding device for the document file shown in FIGS. 1 and 2 will be described. FIG. 3 is a flowchart showing an outline of processing performed by the information embedding device for a document file according to an embodiment of the present invention. First, the additional information arrangement unit 10 performs a process of arranging additional information (step S10). Specifically, first, the information embedding apparatus for the document file reads the specified document file from the document file storage unit 40 in accordance with a user instruction via the key input I / F 4.

  FIG. 4 shows an example of a document file before embedding additional information. FIG. 4 shows an arrangement state of objects when one page in the document file is displayed on the display unit 6. In the example of FIG. 4, four objects are arranged. As four objects, character strings are arranged in the upper left and upper right, a vector image is arranged in the lower left, and a raster image is arranged in the lower right. Note that the four rectangles indicate an image area in which a vector image and a raster image are arranged, and a character area in which a character string is arranged, respectively. The image area is basically the same size as the arranged image, but the character area has a size obtained by adding a predetermined width to the outer shape of the arranged character string. The already-arranged character string, vector image, and raster image displayed in FIG. 4 are not information for embedding, but are displayed and printed, and are used to convey information to the user.

  The document file shown in FIG. 4 can be created in various known formats. For example, MS-Word (registered trademark), PowerPoint (registered trademark), Illustrator (registered trademark), InDesign (registered trademark), and the like can be used.

  The arrangement of the additional information in step S10 has various forms depending on the already arranged object and the object embedded as the additional information. Here, four examples according to combinations of objects already arranged and objects embedded as additional information will be described as steps S11 to S14.

  First, a raster image is arranged on a vector image (step S11). A raster image to be embedded as additional information is acquired from an image file recorded in the additional information storage unit 50. FIG. 5 shows the state of the document file after the raster image is arranged. As shown in the lower left of FIG. 5, the raster image acquired from the additional information storage means 50 is arranged on the already arranged vector image. Specifically, when an accurate arrangement position is designated via the key input I / F 4 and an arrangement instruction is given, the additional information arrangement unit 10 designates the raster image acquired from the additional information storage unit 50 in the document file. Place it at the specified position. In the example of FIG. 5, the image area in which the raster image is arranged is smaller than the image area in which the vector image is arranged, and completely fits in the image area in which the vector image is arranged.

  Next, a character string occupying a larger area is placed on the character string (step S12). The character string embedded as additional information is additional information in the character code format. In step S12, a character string as additional information is arranged in an area including a character area where an already arranged character string is arranged. Here, it is assumed that a character string with the same background color is arranged as additional information. The character string having the same background color is a character string having the same color as the background color of the document file, and the character area in which the character string is arranged is also the same color as the background color. If a character string that is not the same color as the background color is embedded as additional information, both the already-arranged character strings are displayed in an overlapping manner, making it difficult to read.

  FIG. 6 shows the state of the document file after the arrangement of the character string as additional information. As shown in the upper left of FIG. 6, the background same color character string acquired from the additional information storage means 50 is arranged on the already arranged character string. Specifically, when an accurate arrangement position is designated via the key input I / F 4 and an arrangement instruction is given, the additional information arrangement unit 10 stores the background same color character string acquired from the additional information storage unit 50 in the document file. Place at the position specified by. In the example of FIG. 6, the character area in which the character string with the same background color is arranged is larger than the character area in which the already arranged character string is arranged, and includes the character area in which the already arranged character string is arranged. It is like that. Since the already arranged character string is completely hidden behind the background same color character string in a state where the background same color character string is arranged, the existing area of the already arranged character string is indicated by a broken line in FIG. As described above, since the character string with the same background color has the same color as the background, the rectangular shape indicated by the solid line cannot actually be recognized. The same color string will blend into the background.

  Next, a character string occupying a smaller area is placed on the character string (step S13). In step S13, a character string as additional information is arranged in a character area included in a character area in which an already arranged character string is arranged. Here, as in step S12, a background same color character string is arranged as additional information. FIG. 7 shows the state of the document file after the arrangement of the character string as additional information. As shown in the upper right of FIG. 7, the background same color character string acquired from the additional information storage means 50 is arranged on the already arranged character string. Specifically, when an accurate arrangement position is designated via the key input I / F 4 and an arrangement instruction is given, the additional information arrangement unit 10 stores the background same color character string acquired from the additional information storage unit 50 in the document file. Place at the position specified by. In the example of FIG. 7, the character area in which the character string with the same background color is arranged is smaller than the character area in which the arranged character string is arranged, and is included in the character area in which the arranged character string is arranged. It has become so. As described above, in the background same color character string, since the character area has the same color as the background, the portion in the rectangle indicating the background same color character string indicated by the solid line is actually displayed in the same color as the background. .

  Subsequently, the raster image is arranged on the raster image (step S14). As in step S <b> 11, the raster image to be embedded as additional information is acquired from the image file recorded in the additional information storage unit 50. FIG. 8 shows the state of the document file after the raster image is arranged. As shown in the lower right of FIG. 8, the raster image acquired from the additional information storage means 50 is arranged on the already arranged raster image. Specifically, when an accurate arrangement position is designated via the key input I / F 4 and an arrangement instruction is given, the additional information arrangement unit 10 designates the raster image acquired from the additional information storage unit 50 in the document file. Place it at the specified position. In the example of FIG. 8, the image area in which the raster image to be embedded as additional information is arranged is smaller than the image area in which the existing raster image is arranged, and the image area in which the existing raster image is arranged. It is supposed to be included.

  Here, four processes are shown as the process of arranging additional information (step S10), the raster image is arranged on the vector image (step S11), and the character string occupying a larger area is superimposed on the character string (step S11). In step S12), processing is performed in the order of arrangement of a character string that occupies a smaller area on the character string (step S13) and arrangement of the raster image on the raster image (step S14). These processes may be performed in any order. Moreover, it is not necessary to perform all the processes of S11 to S14, and one or more processes may be performed.

  Next, the display priority of the arranged additional information is changed (step S20). Specifically, first, the user instructs display priority change in a state where all the additional information is arranged as shown in FIG. Then, the display priority changing means 20 changes the display priority of the arranged additional information so as to be placed lower than the objects of the already arranged character string, vector image, and raster image. Accordingly, the character string, vector image, and raster image objects that have already been placed have a higher display priority and are placed higher. FIG. 9 shows the state of the document file after changing the display priority. In FIG. 9, a portion surrounded by a broken line indicates a portion hidden by another object. As can be seen from a comparison with FIG. 8, in FIG. 9, the additional information is changed to a state where the display priority is low, and is hidden by other objects.

  As shown in FIG. 9, in the portion where the lower right raster images are overlapped with each other, the already-arranged raster image that has been changed so as to increase the display priority is divided into six regions of 3 × 2 in the horizontal direction. . This is performed by the display priority changing means 20 in step S20. Specifically, when the raster images overlap each other and the display priority is changed, the display priority changing unit 20 divides the raster image to be changed to a higher display priority into a predetermined number of set areas. To do. Then, the divided raster images are set to the same display priority. In this way, when raster images overlap each other, the already-arranged raster images are divided and displayed. However, since the division boundary line cannot be visually recognized, it is impossible to recognize the divided state. The number of areas to be divided can be set in advance.

  In the lower left of FIG. 9, the vector image and the raster image overlap, but the PDF reader cannot select and extract the vector image. For this reason, in this embodiment, a raster image having a high display priority can be converted into a vector image. Specifically, when the additional information arrangement unit 10 reads a document file from the document file storage unit 40 and there is a raster image designated to be converted into a vector format, the additional information arrangement unit 10 displays the raster image as Convert to a vector image. Various known methods can be used as a method for converting a raster image into a vector image. In the present embodiment, the additional information arrangement unit 10 converts the original raster image into a rough pixel representation, and further converts each converted pixel into square vector data painted with the color of the pixel. As the square vector data, an EPS (Encapsulated Post Script) format can be used. As a result, the original raster image is converted into an EPS image which is a kind of vector image. Among the document files read from the document file storage unit 40, the designated raster image is converted into a vector image in this way, and is set to an already arranged vector image as shown in the lower left of FIG. Can do. In this way, by converting a raster image that is not desired to be extracted into a vector image, it is possible to prevent the image from being extracted when the document file is viewed.

  If the display priority has been changed, the document format conversion means 30 then converts the document format (step S30). Specifically, the document file is converted into a different document file format (for example, a popular PDF document so that the additional information can be selected and extracted in the existing image area and character area when viewing the converted document file. ) To obtain an embedded document file. This is realized by using an algorithm similar to that of known PDF document format conversion software. Specifically, the document file after changing the display priority is recorded in various formats such as MS-Word (registered trademark), PowerPoint (registered trademark), Illustrator (registered trademark), InDesign (registered trademark). Each character string data, raster image data (BMP format, etc.), and vector image data in the character code format (Shift-JIS, etc.) to be converted into an international standard PostScript (registered trademark) format. Note that the Illustrator (registered trademark) document is originally written in the PostScript format, so this conversion is unnecessary. This conversion to PostScript format is performed uniformly for character string data and image data that are hidden in the lower layer and are not displayed, or for character string data and image data with the same background color. Information is also inherited. In this conversion process, the character code constituting the character string data is often converted to an Adobe code other than Shift-JIS, and the bitmap constituting the raster image data is often compressed in JPEG format. In addition, for the convenience of inserting layout control data, character string data and raster image data are often divided as appropriate. Next, character string data converted to PostScript format, raster image data, vector image data, font data referenced by the character string data, color conversion table referenced by the raster image data, etc. are added, and each of them is losslessly compressed in ZIP format. Are combined into a single file to obtain an international standard PDF document file. These series of processing can be realized by using editing software such as Adobe Acrobat (registered trademark). The embedded document file is stored in the embedded document file storage means 60.

<3. Extraction process>
Next, extraction of additional information from the obtained embedded document file will be described. Extraction of additional information from the embedded document file is performed by starting browsing software or editing software on a computer having a hardware configuration as shown in FIG. However, the computer is not limited to the one shown in FIG. 1, and a portable terminal such as a tablet computer can be used as long as the PDF file can be browsed and an object can be extracted from the PDF file.

  First, a case where additional information is extracted using browsing software will be described. FIG. 10 is a diagram showing whether or not extraction is possible with a PDF reader that is browsing software when an object is superimposed. When characters overlap, if the upper character area is smaller than the lower character area, only the lower characters of the larger area can be extracted as shown in FIG. Also, when characters overlap each other, if the upper character area is larger than the lower character area, only the upper characters in the larger area can be extracted as shown in FIG. 10A corresponds to the overlapping state of the same color character string in the background, which is additional information in the upper left of FIG. 9, and the already arranged character string, and FIG. 10B shows the already arranged character string in the upper right of FIG. And the background color of the same color as additional information.

  As shown in FIG. 10C, when the vector image and the raster image overlap, the lower raster image can always be extracted. In the example of FIG. 10C, the vector image is higher and the raster image is lower, but conversely, even if the raster image is higher and the vector image is lower, the raster image can always be extracted. FIG. 10C corresponds to the overlapping state of the previously arranged vector image in the lower left of FIG. 9 and the raster image as additional information.

  When the raster image and the raster image overlap, if the image area of the upper raster image is greater than or equal to the image area of the lower raster image, as shown in FIG. Only images can be extracted. However, this is the case where the image areas of the two raster images are congruent or similar and arranged at the same position, and the image area of the lower raster image is smaller than the image area of the upper raster image. However, when the lower raster image is arranged at a position protruding from the upper raster image, the lower raster image can also be extracted by designating the protruding portion. FIG. 10D corresponds to the overlapping state of the already arranged raster image in the lower right of FIG. 9 and the raster image as additional information.

  FIG. 11 is a flowchart showing the extraction process of additional information when browsing software is used. First, the browsing software is activated (step S51). As browsing software, Adobe Reader (registered trademark) or the like can be used.

  Next, the upper or lower character string is selected on the screen (step S52). This is realized by designating via the key input I / F 4 according to the function of the browsing software. Of the upper and lower character strings, the one having the larger character area is selected. For example, as shown in the upper left of FIG. 9, when the character area that is the lower additional information is larger than the upper arranged character area, the upper arranged character string cannot be selected and is the lower additional information. A character string can be selected. Further, as shown in the upper right of FIG. 9, when the character area of the character string that is the lower additional information is smaller than the character area of the upper arranged character string, the character string that is the lower additional information cannot be selected. , A higher-order character string can be selected. When the character areas of the upper and lower character strings have the same size, both the upper and lower character strings can be selected at the same time.

  When the upper or lower character string is selected, it is transferred to a text editor such as “Notepad” by copy and paste (step S53). Thereby, the extracted character string is recorded in the text editor. When both upper and lower character strings are selected at the same time, both character strings are extracted and recorded. When both upper and lower character strings are selected simultaneously, the extraction and recording formats differ depending on the algorithm used by the document format conversion means 30. For example, when the document format conversion means 30 converts to a PDF text format using an algorithm similar to Adobe Acrobat Distiller (registered trademark), both character strings are appropriately divided into phrases and mixed. Specifically, the character string is divided at a position where the layout rule is changed (punctuation mark / space, mutual change between half-width and full-width). For example, after the upper 10 character strings, the lower 10 character strings, the upper 10 character strings,. . . It is copied and pasted alternately and mixed. When the document format conversion means 30 converts to the PDF text format using the same algorithm as Adobe Acrobat PDF Maker (registered trademark), the upper and lower character strings are correctly distinguished from each other. And extracted.

  If it is desired to extract a raster image, an upper or lower raster image is selected on the screen after the viewing software is activated (step S54). This is realized by designating via the key input I / F 4 according to the function of the browsing software. When selecting a lower raster image, the lower raster image is not overlapped with the upper raster image, and is selected by designating a displayed portion. Thereby, the computer recognizes the lower raster image. When the raster images overlap each other, the upper raster image can always be selected and extracted. For this reason, if a raster image that is not desired to be extracted is divided as shown in FIG. 9, it can be selected and extracted only in units of regions, so that easy duplication can be prevented. In the example of FIG. 9, in order to extract the upper raster image, six selection operations are required. When the upper or lower raster image is selected, it is transferred to an image editor such as “Paint Tool” by copy and paste (step S55). Thereby, the extracted raster image is recorded in the image editor.

  Next, a case where additional information is extracted using editing software will be described. FIG. 12 is a flowchart showing extraction processing of additional information when editing software is used. First, the editing software is activated (step S61). As the editing software, the above-mentioned Adobe Acrobat or the like can be used.

  Next, a character extraction function is executed (step S62). This is realized by designating via the key input I / F 4 according to the function of the editing software. Thereby, the character string which is additional information is extracted with the already arranged character string. In step S62, unlike step S52 in FIG. 11, all character strings are extracted regardless of the overlapping state. Therefore, in the example of FIG. 9, both the background same color character string as the additional information in the upper left of FIG. 9 and the already arranged character string are extracted, and the background same color as the already arranged character string in the upper right of FIG. Both strings are extracted.

  If there is additional information in the raster image format, the image extraction function is executed after the editing software is started (step S63). This is realized by designating via the key input I / F 4 according to the function of the editing software. Thereby, the raster image which is additional information is extracted with the already arranged image. In step S63, unlike in step S54 in FIG. 11, all raster images are extracted regardless of the overlapping state. Therefore, in the example of FIG. 9, the raster image that is the additional information at the lower left of FIG. 9 is extracted, and both the already-arranged raster image at the lower right of FIG. 9 and the raster image that is the additional information are extracted.

  In the information embedding device of this embodiment, additional information is embedded in an invisible state. Therefore, when the embedded document file is displayed, the additional information is not displayed, and the duplicator uses it without being aware that the additional information is embedded in the document file. However, when the processing shown in FIGS. 11 and 12 is performed and characters and images are duplicated and pasted, embedded characters and images are extracted instead of characters and images intended by the duplicator. . For this reason, it is possible to alert the person who easily copied the document file. Furthermore, when browsing software is used as shown in FIG. 11, characters and images displayed at the top cannot be extracted. In this case, it is not only possible to call attention, but part of the original content cannot be copied.

  Further, the embedded additional information can be applied to various uses, not to call attention. FIG. 13 is a diagram illustrating one application example. In the application example of FIG. 13, first, as shown in FIG. 13A, a document file in PDF format or the like is sent as an e-mail as a password notice. In this password notice, the actual password is embedded in the form of a character string below the character string area described as “Password Notice”. The character area of the password character string is larger than the character area described as “Password Notice”. This is because, as shown in FIG. 10A, the lower character string cannot be extracted unless the character area of the lower character string is larger than the character area of the upper character string.

  The user who has started the viewing software on the computer and browsed the password notice as shown in FIG. 13A selects the character area described as “password notice” with the cursor and performs a copy operation. . Then, the computer stores the password character string recorded in the lower order in a storage area called a clipboard as shown in FIG.

  Next, the user activates application software that should use the password stored in the clipboard, and displays an authentication dialog screen as shown in FIG. Then, after specifying the password input field on the authentication dialog screen, the user performs a paste operation. Then, the computer inputs the password stored in the clipboard into the password input field. If the application software has an automatic extraction function, the computer can automatically extract the password from the clipboard without the user performing a paste operation. By using the application example shown in FIG. 13, the password can be informed to the user by e-mail in a PDF document in an invisible state, and can be passed to the application software authentication system in an invisible state to the user. . Even if you look into the screen, the password is not visible, and there is no key operation log, so it is difficult for a third party to steal the password.

<4. Display example>
Next, specific display examples will be described with reference to FIGS. FIG. 14 is a display example of a document file (indicated as “original document file” in FIG. 14) before the additional information is arranged. In FIG. 14, the character strings in [] are used for explanation, and are not arranged in the actual document file. A character string “characters and images are hidden underneath” is arranged in the [background same color character / image] portion in the upper left of FIG. In the [Upper Extractable / Character / Image] portion in the upper right of FIG. 14, a character string “characters are hidden below this” is arranged, and the upper part of the raster image is overlapped with “ Is hidden "is placed. In the lower left [lower extractable / character / image] portion of FIG. 14, a character string “characters are hidden below this” is arranged and superimposed on the upper portion of the raster image Is hidden "is placed. In the lower right part of FIG. 14, a character string “characters are hidden underneath” is arranged in the “both extractable / character / image” portion, and “ Another character is hidden "is placed.

  FIG. 15 is a display example of a character string / raster image as additional information. In the example of FIG. 15, character strings and images are arranged in the upper left, upper right, lower left, and upper right portions corresponding to the objects arranged in the document file of FIG. A character string “Illegal copying strictly prohibited” is arranged at the top of the drawing. All the images shown in FIG. 15 are raster images.

  FIG. 16 is a display example of a document file in a state where the additional information shown in FIG. 15 is arranged in the document file shown in FIG. In the state of FIG. 16, the processing of step S <b> 10 is performed and only the additional information is arranged. Therefore, only the upper raster image is displayed. For portions where character strings overlap, both upper and lower character strings are displayed.

  FIG. 17 is a display example of a document file in a state where the display priority of the additional information is changed. That is, this is a state in which the process of step S20 in FIG. 3 has been performed. As shown in FIG. 17, all additional information is not displayed. The rectangle shown in FIG. 17 indicates the area of the original object and additional object, and is not actually displayed. FIG. 18 is obtained by removing the rectangle indicating the object area. The appearance is the same as the document file before embedding shown in FIG.

  The embedded document file is obtained by performing the document format conversion in step S30 of FIG. 3 on the document file shown in FIG. FIG. 19 shows a display example of the obtained embedded document file by browsing software (Adobe Reader). The appearance is the same as the document file in which the information shown in FIG. 14 is not embedded.

  In the document file shown in FIG. 19, it is assumed that the duplicator selects the character string “characters are hidden under this” displayed in the lower left by dragging using the mouse. Then, the text editor “Notepad” is designated by the copy and paste operation. Then, as shown in FIG. 20, only the character string “Illegal Copy Strictly Prohibited, XX Company” embedded under the character string “The character is hidden under this” is copied. This is because the character area of the lower character string “Illegal Copy Strictly Not Allowed” is larger than the character area of the upper character string “the character is hidden below this”. As a character string to be duplicated, it is preferable to use a sentence that warns that duplication is illegal, as shown in FIG.

  In the document file shown in FIG. 19, it is assumed that the duplicator selects the image displayed at the lower left by clicking with the mouse. Then, an image editor “paint tool” is designated by a copy and paste operation. Then, as shown in FIG. 21, only the raster image embedded in the lower layer is duplicated. This is because the upper image is a vector image and the lower image is a raster image.

  In the document file shown in FIG. 19, it is assumed that the duplicator selects the character string “characters are hidden under this” displayed at the lower right by dragging using the mouse. Then, the text editor “Notepad” is designated by the copy and paste operation. Then, as shown in FIG. 22, both the character string “The character is hidden under this” arranged at the upper part and the character string “Copying strictly prohibited. Duplicated. This is because the area of the lower character string “copying prohibited” is the same size as the character area of the upper character string “characters are hidden below this”.

  In the document file shown in FIG. 19, the duplicator selects the character area in which the character string “characters and images are hidden below” is displayed by clicking with the mouse on the upper left. And Then, an image editor “paint tool” is designated by a copy and paste operation. Then, as shown in FIG. 23, only the raster image embedded in the lower order is duplicated. This is because the upper image is a vector image having the same color as the background color, and the lower image is a raster image.

<5. Modified example>
The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above-described embodiment, characters and raster images are embedded only for display or acquisition. However, it is also possible to embed characters and raster images so as to realize various functions by combination.

  For example, by embedding a raster image representing a two-dimensional barcode below the vector image and passing it directly to the two-dimensional barcode recognition function of the image processing software via the clipboard, detailed information about the document file is not disclosed. Can be acquired.

  As an application to rich content, embed text strings for explanation under images and explanatory diagrams (both raster images and vector images), or embed text strings translated into foreign languages under Japanese text strings. It is possible to apply to barrier-free and foreigner support, such as passing to the voice synthesis software via the clipboard and giving explanations in various languages by voice. In addition, by embedding MIDI data in character code format under the image representing the music score (either raster image or vector image), it is possible to provide a function to check the melody of the music score with the ear by passing it to the MIDI sequencer. it can.

  In the above embodiment, the information embedding device for the document file arranges the raster image on the vector image (step S11 in FIG. 3), and arranges the character string occupying a larger area on the character string (step S12 in FIG. 3). ), Arrangement of character strings that occupy a smaller area over the character strings (step S13 in FIG. 3), and arrangement of raster images over the raster image (step S14 in FIG. 3). However, you may implement | achieve as an apparatus provided with one or more of these structures.

1 ... CPU (Central Processing Unit)
2 ... RAM (Random Access Memory)
3 ... Storage device 4 ... Key input I / F
5. Data input / output I / F
6 ... Display unit 10 ... Additional information arrangement means 20 ... Display priority changing means 30 ... Document format conversion means 40 ... Document file storage means 50 ... Additional information storage means 60 ...・ Embedded document file storage means

Claims (7)

An apparatus for recording additional information including at least one of a raster image or character code format characters in an invisible state on a document file in which a vector image is arranged,
Additional information arrangement means for arranging the additional information in an image area in which a vector image is arranged in advance in the document file;
Display priority changing means for changing the display priority of the additional information to be lower than the display priority of the vector image arranged in advance, and to place the display information lower.
The document file whose display priority is changed by the display priority changing unit is converted into a predetermined format so that the additional information can be extracted and the vector image cannot be extracted when browsing the embedded document file. Document format conversion means to
An information embedding device for a document file, comprising:   The said additional information arrangement | positioning means converts the said image into a vector format, and obtains the said vector image, when the image in which conversion to the vector format was designated exists in the said document file. Item 14. An information embedding device for a document file according to Item 1.   3. The information embedding apparatus for a document file according to claim 1, wherein the vector image is uniformly filled with the same color as a background color. An apparatus for recording additional information in a character code format in an invisible state on a document file in which characters are arranged,
Additional information arrangement means for arranging the additional information in a background color of the document file in a character area including a character area in which characters are arranged in advance in the document file;
Display priority changing means for changing the display priority of the additional information to be lower than the display priority of the characters arranged in advance, and to place the display information lower.
When browsing the document file after embedding, the additional information can be extracted, and the document file whose display priority has been changed by the display priority changing unit is set to a predetermined value so that characters placed in advance cannot be extracted. Document format conversion means for converting to a format;
An information embedding device for a document file, comprising: An apparatus for recording additional information in a character code format in an invisible state on a document file in which characters are arranged,
Additional information arrangement means for arranging the additional information in a background color of the document file in a character area included in a character area in which characters are arranged in advance in the document file;
Display priority changing means for changing the display priority of the additional information to be lower than the display priority of the characters arranged in advance, and to place the display information lower.
When browsing the document file after embedding, the additional information cannot be extracted, and the document file whose display priority has been changed by the display priority changing means is set so that the pre-arranged characters can be extracted. Document format conversion means for converting to a format;
An information embedding device for a document file, comprising: A device that records additional information in a raster image format in an invisible state on a document file in which a raster image is arranged,
Additional information arrangement means for arranging the additional information so that at least part of the additional information overlaps an image area in which a raster image is arranged in advance;
A display priority changing unit that divides the raster image into a plurality of regions, and changes the display priority of the additional information to be lower than the display priority of the raster image that is arranged in advance.
A document for converting a document file whose display priority has been changed by the display priority changing unit into a predetermined format so that a raster image divided into the plurality of areas can be extracted when the embedded document file is viewed Format conversion means,
An information embedding device for a document file, comprising: Three types of objects can be used: vector images, raster images, and characters, and at least two or more different or similar objects can be recorded with the display priority set, and can be recorded at the specified position. A document file that can extract a plurality of corresponding objects with different display priorities,
An embedded document in which display information is recorded as an object having the highest display priority, and additional information embedded in an invisible state is recorded as an object having a display priority lower than that of the display information. File.