JP2006303728A - Method and device for embedding watermark information, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To embed a watermark information so that the embedded information can be restored correctly, regardless of percentage of a character region in the document in which the watermark information is embedded or image density of a background image. <P>SOLUTION: The watermark information embedding device embeds a watermark information in a document image using electronic watermark. It comprises a pixel information detecting part 106 for detecting pixel information of the document image, a watermark density determining part 108 for determining watermark density of the watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detecting part, a watermark information generating part 112 for generating a watermark information embedded in the document image according to the watermark density determined by the watermark density determining part, and a watermark information embedding part 110 for embedding the watermark information generated by the watermark information generating part in the document image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a watermark information embedding device, a watermark information embedding method, and a computer program, and more particularly to a watermark information embedding device capable of embedding watermark information in document data having a pattern in the entire background.

  In recent years, a method has been disclosed in which electronically readable information is added to a printed matter and a communication partner is specified based on the additional information (for example, Patent Document 1). Thus, for example, when printing a printed matter, it is possible to add information for specifying a printing device or the like on which printing is performed, and to specify a printer who uses the printing device from the additional information.

  As a method for adding electronically readable information to the printed matter, a method is disclosed in which information is expressed by a fine dot pattern and watermark information is embedded in the entire background of the printed matter (for example, Patent Document 2). In Patent Document 2, even if watermark information is superimposed on a figure or characters of a printed matter, it is possible to read correct information by providing redundancy to the watermark information embedded in the document. For example, by repeatedly embedding a dot pattern representing the same information on the entire paper surface, the embedded information can be read correctly even if a part of the watermark background pattern disappears. In addition, by using a watermark pattern as one information unit, watermark information is embedded in areas where the percentage of the text area in the document is large and information cannot be read correctly even if the watermark pattern is embedded, thereby preventing loss of information. Can do.

Japanese Patent Laid-Open No. 2003-110827 JP 2003-209676 A

  However, when the ratio of the character area occupies the entire document or when the entire background of the document has a pattern, there is a problem that information cannot be read correctly even if a watermark pattern is embedded. For example, if a watermark is embedded in the entire background and there is a pattern in the entire background and the pattern is emphasized from the watermark pattern and printed, the watermark information can be embedded so that the information can be read correctly. There wasn't.

  Therefore, the present invention has been made in view of such a problem, and the object of the present invention is to embed regardless of the ratio of the character area of the document in which the watermark information is embedded or the image density of the background image. To provide a new and improved watermark information embedding device, watermark information embedding method and computer program capable of embedding watermark information so that information can be correctly restored.

  In order to solve the above-described problem, according to one aspect of the present invention, there is provided a watermark information embedding device that embeds watermark information in a document image with a digital watermark: a pixel information detection unit that detects pixel information of the document image; A watermark density determining unit that determines a watermark density of watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detecting unit; a document according to the watermark density determined by the watermark density determining unit; There is provided a watermark information embedding device, comprising: a watermark information generation unit that generates watermark information to be embedded in an image; and a watermark information embedding unit that embeds the watermark information generated by the watermark information generation unit in a document image. The

  The pixel information of the document image is information such as the image density and color of the document image. The watermark density is the point density of the watermark background pattern represented by a dot pattern. The higher the watermark density value is, the higher the density of the background pattern point is. The watermark information can be embedded means that the watermark information can be embedded so that the watermark information can be read correctly.

  According to the above configuration, the watermark density can be adjusted according to the image density or the like of the document image to be embedded with the watermark information, and the watermark information capable of reading the information can be embedded. As a result, even when information cannot be restored even if a watermark is embedded due to the influence of the background of the document, it is possible to generate a watermarked document image with enhanced watermark reading performance by emphasizing the watermark.

  The watermark density determination unit may determine the watermark density of the watermark information that can be embedded in the document image when the black pixel ratio included in the pixel information of the document image is equal to or greater than a predetermined ratio. According to such a configuration, it is possible to embed watermark information in a document having a large proportion of black pixels so that the watermark background pattern represented by the black pixels is emphasized and the watermark information can be read correctly.

  The pixel information detection unit divides the document image into a plurality of watermark embedding regions and detects pixel information for each watermark embedding region, and the watermark density determination unit detects the document image detected by the pixel information detection unit. Based on the pixel information for each watermark embedding area, the watermark density of the watermark information that can be embedded in the document image may be determined. The pixel information detection unit detects a black pixel ratio for each watermark embedding area, and the watermark density determination unit calculates the number of non-embeddable areas in which the black pixel ratio for each embedding area is a predetermined ratio or more. When the number of non-embeddable areas is equal to or greater than a predetermined number, the watermark density of watermark information that can be embedded in a document image may be determined. According to such a configuration, even when the distribution of black pixels in the document image to which the watermark information is to be embedded is biased, the watermark is determined so that the watermark information can be read correctly by determining whether or not the watermark information can be embedded. It becomes possible to embed watermark information by adjusting the density.

  The watermark density determination unit may determine the watermark color of the watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detection unit. According to this configuration, even when the document image is a color document, it is possible to select a watermark color suitable for the document and embed the watermark information so that the watermark information can be read.

  In order to solve the above problems, according to another aspect of the present invention, there is provided a watermark information embedding device that embeds watermark information in a document image with a digital watermark: a pixel information detection unit that detects pixel information of the document image; An image density determination unit that determines the image density of the document image based on the pixel information detected by the pixel information detection unit so that watermark information can be embedded; and the document has the image density determined by the image density determination unit. There is provided a watermark information embedding device comprising: an image density adjustment unit that adjusts an image density of an image; and a watermark information embedding unit that embeds watermark information in a document image adjusted by the image density adjustment unit. .

  According to the above configuration, it is possible to embed watermark information capable of reading information by adjusting the image density according to the image density of the document image into which the watermark information is embedded. As a result, it is possible to generate a watermarked document image in which the watermark reading performance is improved by suppressing the density of the background for a document whose information cannot be restored even if the watermark is embedded due to the influence of the document background or the like.

  The image density determination unit may determine the image density of the document image so that the watermark information can be embedded when the ratio of black pixels included in the pixel information of the document image is equal to or higher than a predetermined ratio. Good. According to such a configuration, it is possible to embed watermark information so that the watermark information can be correctly read out by reducing the density of the image to be the background image and emphasizing the watermark background pattern for a document with a high proportion of black pixels. .

  The pixel information detection unit divides the document image into a plurality of watermark embedding regions to detect pixel information for each watermark embedding region, and the image density determination unit detects the watermark of the document image detected by the pixel information detection unit. Based on the pixel information for each embedding area, the image density of the document image may be determined so that watermark information can be embedded. The pixel information detection unit detects a black pixel ratio for each watermark embedding area, and the image density determination unit calculates the number of non-embeddable areas in which the black pixel ratio for each embedding area is a predetermined ratio or more. When the number of non-embeddable areas is a predetermined number or more, the image density of the document image may be determined so that watermark information can be embedded. According to such a configuration, even when the distribution of black pixels in the document image to which the watermark information is to be embedded is biased, it is determined whether the watermark information can be embedded correctly and the background can be read. It is possible to embed watermark information by adjusting the density of the image.

  The pixel information detection unit detects the ratio of black pixels included in the document image, and the image density adjustment unit converts the document image in which the watermark is embedded into black and white when the ratio of black pixels is a predetermined ratio. It may be reversed. As a result, when the ratio of black pixels is equal to or greater than a predetermined value, the document image can be reversed in black and white and the watermark information can be embedded in the document image. According to such a configuration, even when watermark information cannot be embedded unless image processing is performed significantly, a watermarked document image with reduced readability and improved reading performance can be obtained by reversing the document image in black and white. Can be generated.

  In order to solve the above-described problem, according to another aspect of the present invention, there is provided a watermark information embedding device that embeds watermark information in a document image with a digital watermark: a pixel information detection unit that detects pixel information of a document image And based on the pixel information detected by the pixel information detection unit, the watermark density of the watermark information embedded in the document image and the image density of the document image in which the watermark information is embedded so that the watermark information can be embedded in the document image. A density determining unit for determining the watermark information; a watermark information generating unit for generating watermark information to be embedded in the document image in accordance with the watermark density determined by the density determining unit; and the image density determined by the density determining unit for the document image An image density adjusting unit for adjusting the image density; and embedding the watermark information generated by the watermark information generating unit in the document image adjusted by the image density adjusting unit. A watermark information embedding unit for writing; characterized in that it comprises a watermark information embedding device is provided.

  According to the above configuration, it is possible to embed watermark information capable of reading information by adjusting the watermark density and the image density in accordance with the image density or the like of the document image to be embedded with the watermark information. As a result, even if the information cannot be restored even if the watermark is embedded due to the influence of the background of the document, etc., a watermarked document image in which the reading density is improved by suppressing the background density and enhancing the watermark is generated. Can do.

  The density determination unit includes a watermark density of watermark information that can be embedded in the document image and an image density of the document image in which the watermark information is embedded when the ratio of black pixels included in the pixel information of the document image is equal to or greater than a predetermined ratio. May be determined. According to such a configuration, it is possible to embed watermark information so that the watermark information can be read correctly by reducing the density of the image to be the background image and increasing the watermark density for a document with a large proportion of black pixels. .

  The pixel information detection unit divides a document image into a plurality of watermark embedding regions to detect pixel information for each watermark embedding region, and the density determination unit includes a watermark embedding region of the document image detected by the pixel information detection unit. Based on each pixel information, the watermark density of the watermark information that can be embedded in the document image and the image density of the document image in which the watermark information is embedded may be determined. The pixel information detection unit detects the black pixel ratio for each watermark embedding area, and the density determination unit calculates the number of non-embeddable areas in which the black pixel ratio for each embedding area is equal to or greater than a predetermined ratio. When the number of areas is a predetermined number or more, the watermark density of the watermark information that can be embedded in the document image and the image density of the document image in which the watermark information is embedded may be determined. According to such a configuration, even when the distribution of black pixels in the document image to which the watermark information is to be embedded is biased, the watermark is determined so that the watermark information can be read correctly by determining whether or not the watermark information can be embedded. It is possible to embed watermark information by adjusting the density and the density of the background image.

  The pixel information detection unit detects the ratio of black pixels included in the document image, and the image density adjustment unit converts the document image in which the watermark is embedded into black and white when the ratio of black pixels is a predetermined ratio. It may be reversed. As a result, when the ratio of black pixels is equal to or greater than a predetermined value, the document image can be reversed in black and white, and the watermark density corresponding to the image density of the reversed document image can be determined. According to such a configuration, even when watermark information cannot be embedded unless image processing is performed significantly, a watermarked document image with reduced readability and improved reading performance can be obtained by reversing the document image in black and white. Can be generated.

  The watermark density determination unit may determine a watermark color of watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detection unit. According to this configuration, even when the document image is a color document, it is possible to select a watermark color suitable for the document and embed the watermark information so that the watermark information can be read.

  Based on the pixel information detected by the pixel information detection unit, an image separation unit that separates the character image and the background image included in the document image, and the character image and the background image separated by the image separation unit are combined. An image composition unit, and the density determination unit determines the character density of the character image and the background density of the background image so that the watermark information can be embedded in the document image. The image density of the character image is adjusted to the character density determined by the determination unit, the image density of the background image is adjusted to the background density, and the watermark information embedding unit adds the watermark information to the character image adjusted by the image density adjustment unit. The embedding / image combining unit may combine the character image with the watermark information embedded with the background image.

  According to the above configuration, it is possible to easily read the watermark information embedded in the character image by separating the character and background of the document image, increasing the density of the character image, and decreasing the density of the background image. A watermarked document image can be generated.

  In order to solve the above problems, according to another aspect of the present invention, there is provided a watermark information embedding method for embedding watermark information in a document image with a digital watermark: a pixel information detection step for detecting pixel information of a document image Determining the watermark density of the watermark information embedded in the document image and the image density of the document image in which the watermark information is embedded so that the watermark information can be embedded in the document image based on the pixel information; And generating watermark information to be embedded in the document image and adjusting the image density of the document image to the image density; and embedding the watermark information in the document image having the adjusted image density. An embedding method is provided.

  In order to solve the above-mentioned problem, according to another aspect of the present invention, there is provided a computer program for causing a computer to function as a watermark information embedding device that embeds watermark information into a document image with a digital watermark: A pixel information detection process for detecting the pixel information of the watermark information; a watermark density of the watermark information embedded in the document image and a watermark so that the watermark information can be embedded in the document image based on the pixel information detected by the pixel information detection unit; A density determination process for determining an image density of a document image in which information is embedded; a watermark information generation process for generating watermark information to be embedded in the document image in accordance with the watermark density determined by the density determination unit; Image density adjustment processing for adjusting the image density of the document image to the determined image density; adjustment by the image density adjustment unit Computer program is provided to perform; the document image, the watermark information embedding process and to embed the watermark information generated by the watermark information generating unit.

  As described above, according to the present invention, it is possible to embed watermark information so that the embedded information can be correctly restored regardless of the ratio of the character area of the document in which the watermark information is embedded and the image density of the background image. A possible watermark information embedding device, watermark information embedding method, and computer program can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  First, watermark information using a tint block employed in the watermark information embedding device of the present invention will be described. The watermark information using a background pattern is information embedded in a paper document as digital document data as a document background. The watermark information is expressed in a fine dot pattern on the printed material and is embedded in the entire background of the printed material so as to be superimposed on the figure or characters of the printed material.

  The electronically readable digital data embedded as the background of the printed material can be read from the characteristics of the dot pattern by image processing. Even when a watermark pattern overlaps with a figure or a character and a part of the watermark information cannot be read, it is possible to read the information correctly by providing redundancy to the watermark information. Also, by treating the watermark pattern as one information unit, the watermark information is embedded to avoid areas where information cannot be read correctly even if the watermark pattern is embedded in a large proportion of the text area in the document, thereby preventing loss of information. be able to.

  Recently, in order to prevent leakage of confidential information, restrictions are set for electronic files and the like, but it is necessary to prevent information leakage for paper documents. Therefore, when printing electronic data on a paper document, the device ID of the PC (Personal Computer) or printing apparatus that performed the printing process, the user ID of the user who made the printing request, the printing date and time, etc. are used as the watermark information. By adding it to the document, it becomes possible to specify the printer of the paper document. For example, the leaked person can be identified by collecting the leaked printed document and reading the information added to the leaked document. In addition, when confidential information is leaked, it is possible to expect a deterrent effect to a person who attempts to leak information by making it known that information specifying a printer is automatically added.

  As described above, in order to prevent information leakage by embedding watermark information that identifies the printer, all documents, that is, documents that occupy the entire text area or documents that have a pattern in the entire background, etc. Also, it is necessary to embed the watermark information so that the watermark information can be read correctly.

  Since the watermark pattern is represented by black pixels, it can be read even if the watermark information is embedded in a document with a large proportion of black pixels, such as a document that occupies the entire character area or a document that has a pattern on the entire background. Becomes difficult. For example, even if watermark information is embedded in a grayscale image with shading, the information cannot be read correctly. Therefore, in the present invention, watermark information embedding is possible in which watermark information can be embedded so that the watermark information can be read correctly even when the ratio of the character area is large and the ratio of black pixels is large, such as when there is a pattern in the entire background. Providing equipment.

  Hereinafter, “embedding watermark information” means that the watermark information can be embedded so that the watermark information can be read correctly. In this embodiment, information embedded in a document as watermark information will be described as the above-mentioned printer specific information. However, the present invention is not limited to such an example, and is not limited to such information. Any information can be used as long as it can be converted into a watermark pattern as digital data.

(First embodiment)
In the first embodiment, the watermark information generation apparatus according to the present invention is added to the watermark information embedding apparatus 100a capable of improving the watermark information reading performance by adjusting the watermark density of the watermark information according to the image density of the document image. Will be described. First, the functional configuration of the watermark information generating apparatus 100a according to the first embodiment will be described with reference to FIG.

<1. Functional configuration of watermark information embedding device>
FIG. 1 is a block diagram showing a functional configuration of a watermark information embedding device 100a according to the present embodiment. As shown in FIG. 1, the watermark information embedding device 100a includes document data 102, a document data imaging unit 104, a pixel information detection unit 106, a watermark density determination unit 108, a watermark information embedding unit 110, and a watermark. The information generating unit 112, the embedded information creating unit 114, the embedded information 116, the printing unit 118, and the like are included.

  The document data 102 is electronic data printed on a paper medium, and is data created by a document creation tool or the like. The document data 102 is data that can be visually recognized when printed on a paper medium. The document data imaging unit 104 has a function of imaging the document data 102 and creating a document image. The document image created by the document data imaging unit 104 is provided to the pixel information detection unit 106 and the watermark information embedding unit 110.

  The pixel information detection unit 106 has a function of detecting pixel information of the document image provided by the document data imaging unit 104. Here, the pixel information is information such as image density and color of the document image. The pixel information detected by the pixel information detection unit 106 may be pixel information for the entire document image, or the document image is divided into a plurality of areas, and the pixel information for each divided area is detected. May be. For example, when the pixel information detected by the pixel information detection unit 106 is black pixel ratio information, the black pixel ratio relative to the entire document image may be detected, or the black pixel ratio may be detected for each divided area. May be detected. Pixel information detected by the pixel information detection unit 106 is provided to the watermark density determination unit 108.

  The watermark density determination unit 108 has a function of determining the watermark density of watermark information that can be embedded in a document image based on the pixel information detected by the pixel information detection unit 106. For example, when a watermark pattern is represented by black pixels, whether or not the embedded watermark information can be read correctly is determined by the black pixel ratio of the document image. If the percentage of black pixels is large, it may not be read correctly even if watermark information is embedded. In that case, the watermark information can be embedded so that the watermark information can be read correctly by adjusting the watermark density of the embedded watermark information. In the watermark embedded in the image document in this embodiment, a plurality of types of dot patterns are regularly arranged, and at least one type of dot pattern among them is a ground pattern representing specific information. The watermark density is the point density of the watermark background pattern represented by a dot pattern. The higher the watermark density value is, the higher the density of the background pattern point is. In the present embodiment, the watermark density that is embedded without adjusting the watermark density is the default value “2” of the watermark density.

  For example, as shown in FIG. 2, the watermarked document image 10 is a diagram in which watermark information of watermark density “2” is embedded in a document image “dragon”. Although the watermark information embedded in the area 10a of the watermarked document image 10 can be read correctly, the watermark information embedded in the area 10b has most of the watermark background pattern overlapped with a part of “dragon”. The watermark information cannot be read correctly. On the other hand, the watermarked document image 12 is a diagram in which watermark information with a watermark density of “4” is embedded. By increasing the watermark density value of the embedded watermark information, the watermark information in the area 12a of the watermarked document image 12 can be read correctly.

  As shown in FIG. 2, when the ratio of black pixels in the document image is large, when the watermark information is embedded with the default value “2” of the watermark density by increasing the watermark density value of the watermark information, Information that could not be read correctly can be read correctly. However, if the watermark density value is increased, the reading performance of the watermark information is improved, but the readability is lowered. Therefore, when the black pixel ratio included in the pixel information of the document image is equal to or less than a predetermined ratio, the watermark density determination unit 108 embeds the watermark information of the watermark density “2” and the black pixel ratio is equal to or higher than the predetermined ratio. In this case, the watermark density of watermark information that can be embedded in the document image may be adjusted.

  As shown in FIG. 3, for example, when the black pixel density 202 of the document image is less than 20%, the watermark density 204 is set to the default value “2”, and the black pixel density 202 is 20% or more and less than 25%. In this case, the watermark density 204 may be set to a density that can be embedded between 3 and 15. If the black pixel density 202 is 25% or more, it may be determined that even if the watermark density is adjusted, the watermark information cannot be embedded so that it can be read correctly. As described above, that watermark information can be embedded means that the embedded watermark information can be read correctly. It is possible to set the watermark density according to the ratio of the detected black pixel density by setting the watermark density that can read the watermark information correctly for the black pixel density of the document image in advance. It becomes.

  In addition, when the pixel information detection unit 106 detects the black pixel ratio for each divided area, the number of areas in which the black pixel ratio is equal to or greater than a predetermined ratio is calculated for each divided area. When the number is equal to or greater than the predetermined number, the watermark density corresponding to the number may be determined. This makes it possible to correctly determine whether watermark information can be embedded even when the distribution of black pixels in the document image is biased. For example, in the case of an A4 size document image, the document image is divided into approximately 2.5 cm square blocks, and the black pixel ratio of each block is detected. Then, the number of blocks in which the detected black pixel ratio is 20% or less is calculated. If the number of blocks is less than 24, it is possible to embed watermark information of watermark density “2” in the document image. If the number of blocks is 25 or more, it is necessary to adjust the watermark density and embed watermark information. It can be judged that there is. The watermark density determined by the watermark density determination unit 108 is provided to the watermark information generation unit 112.

  Returning to FIG. 1, the embedding information creation unit 114 acquires the embedding information 116 and creates data to be embedded in the document image as watermark information. As described above, when the watermark information to be embedded in the document image is the printer identification information that identifies the printer, the user ID of the printer, the device ID of the PC that requested the printing, the date and time, and the print instruction target print The device ID of the machine may be created as embedded information. The embedded information created by the embedded information creating unit 114 is provided to the watermark information generating unit 112.

  The watermark information generation unit 112 generates a watermark image using a background pattern from the embedded information provided by the embedded information generation unit 114. Further, the watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density determined by the watermark density determination unit 108.

  The watermark information embedding unit 110 embeds the watermark information generated by the watermark information generation unit 112 in the document image provided by the document data imaging unit 104, and generates a watermarked document image using a background pattern. The watermarked document image generated by the watermark information embedding unit 110 is provided to the printing unit 118. The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100a to print the watermarked document image provided by the watermark information embedding unit 110.

  The functional configuration of the watermark information embedding device 100a has been described above. Next, a watermark information embedding method in the watermark information embedding device 100a will be described with reference to FIG.

<2. Embedding watermark information>
FIG. 4 is a flowchart showing the watermark information embedding method according to the first embodiment. First, document data is imaged and a document image is created (S101). Based on the pixel information of the document image created in step S101, the watermark density of the watermark information that can be embedded in the document image is determined, and the watermark density of the watermark information is set (S102).

  The embedded information creation unit 114 acquires the user ID of the printer, the device ID of the PC used by the printer, the date, and the like, and creates embedded information (S104). A watermark image using a background pattern is generated from the embedded information created in step S103 (S104). The watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density set in step S102.

  Then, the watermark information generated in step S104 is embedded in the document image created in step S101 to generate a watermarked document image (S105). The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100a to print the watermarked document image generated in step S105 (S106).

  The watermark information embedding method according to the first embodiment has been described above. With the above configuration, even if watermark information of watermark density value “2”, which is the default value of watermark density, is embedded in a document image, the watermark density value is set even for a document in which information cannot be read and information cannot be restored. By emphasizing the watermark by raising it, it is possible to generate a watermarked document image with improved watermark reading performance. However, for a document image in which the density of the document image is high and the ratio of black pixels is equal to or greater than a predetermined value, even if the watermark density value is increased, the watermark information cannot be read and the readability is degraded.

  Therefore, the second embodiment provides a watermark information embedding device that can embed watermark information by adjusting the image density of a document image.

(Second Embodiment)
In the second embodiment, the watermark that can adjust the image density of the document image so that the watermark information can be embedded in accordance with the image density of the document image, and can improve the reading performance of the embedded watermark information. A description will be given by applying the watermark information embedding device of the present invention to the information embedding device 100b. First, the functional configuration of the watermark information embedding device 100b according to the second embodiment will be described with reference to FIG.

<3. Functional configuration of watermark information embedding device>
FIG. 5 is a block diagram showing a functional configuration of the watermark information embedding device 100b according to the present embodiment. As shown in FIG. 5, the watermark information embedding device 100b includes document data 102, a document data imaging unit 104, a pixel information detection unit 106, a watermark information embedding unit 110, a watermark information generation unit 112, an embedding. The information creating unit 114, the embedded information 116, the printing unit 118, the image density determining unit 120, the image density adjusting unit 122, and the like are included.

  The document data 102 is electronic data printed on a paper medium, and is data created by a document creation tool or the like. The document data 102 is data that can be visually recognized when printed on a paper medium. The document data imaging unit 104 has a function of imaging the document data 102 and creating a document image. The document image created by the document data imaging unit 104 is provided to the pixel information detection unit 106 and the image density adjustment unit 122.

  The pixel information detection unit 106 has a function of detecting pixel information of the document image provided by the document data imaging unit 104. Here, the pixel information is information such as image density and color of the document image. The pixel information detected by the pixel information detection unit 106 may be pixel information for the entire document image, or the document image is divided into a plurality of areas, and the pixel information for each divided area is detected. May be. For example, when the pixel information detected by the pixel information detection unit 106 is black pixel ratio information, the black pixel ratio relative to the entire document image may be detected, or the black pixel ratio may be detected for each divided area. May be detected. Pixel information detected by the pixel information detection unit 106 is provided to the image density determination unit 120.

  The image density determination unit 120 has a function of determining the image density of the document image based on the pixel information detected by the pixel information detection unit 106 so that watermark information can be embedded. For example, when a watermark pattern is represented by black pixels, whether or not the embedded watermark information can be read correctly is determined by the black pixel ratio of the document image. If the percentage of black pixels is large, it may not be read correctly even if watermark information is embedded. In that case, the watermark information can be embedded so that the watermark information can be read correctly by adjusting the image density of the embedded document image and embedding the watermark information in the adjusted document image. For example, if a character is represented as a document image and the percentage of black pixels in the character is high, the embedded watermark information is read by reducing the character density, that is, by increasing the character brightness value. Is possible.

  For example, as shown in FIG. 6, the watermarked document image 14 is a diagram in which watermark information is embedded in a document image “dragon”. The character “dragon” in the document image is a character having a normal character density and a luminance value “0”. Although the watermark information embedded in the area 14a of the watermarked document image 14 can be read correctly, the watermark information embedded in the area 14b has most of the watermark background pattern overlapped with a part of “dragon”. The watermark information cannot be read correctly. On the other hand, in the watermarked document image 16, the brightness value of the character is changed to “34”, the watermark information is embedded in the document image whose character density is reduced, and the watermark information embedded in the area 16 a of the watermarked document image 16 is changed. It becomes possible to read correctly.

  As shown in FIG. 6, when the percentage of black pixels in the document image is large, the brightness value of the document image is increased, so that when the watermark information is embedded in the document image having the brightness value “0”, Information that could not be read can be read correctly. However, it is not necessary to change the luminance value of the document image when the ratio of the black pixels of the document image is equal to or less than a predetermined ratio. The luminance value of the document image may be changed only when the ratio of black pixels in the document image is equal to or greater than a predetermined ratio.

  As shown in FIG. 7, for example, when the black pixel density 206 of the document image is less than 25%, the image density 208 of the document image is not adjusted, and when the black pixel density 206 is 25% or more, the document image The image density 208 may be adjusted so that the luminance value of the image is “68”. Thus, when the black pixel density 206 is 25% or more, the luminance value may be changed to a predetermined value, or the luminance value may be changed according to the ratio of black pixels. Good. The brightness value of the document image corresponding to the ratio of the detected black pixel density is set in advance by setting the brightness value of the document image in which watermark information can be correctly embedded with respect to the black pixel density of the document image. Can be set.

  Further, when the black pixel ratio is detected for each divided area by the image information detection unit 160, the number of areas in which the black pixel ratio is equal to or greater than a predetermined ratio is calculated for each divided area. When the number is equal to or greater than the predetermined number, the luminance value of the document image may be adjusted.

  This makes it possible to correctly determine whether watermark information can be embedded even when the distribution of black pixels in the document image is biased. For example, in the case of an A4 size document image, the document image is divided into approximately 2.5 cm square blocks, and the black pixel ratio of each block is detected. Then, the number of blocks in which the detected black pixel ratio is 25% or less is calculated. If the number of blocks is less than 24, it is possible to embed watermark information without adjusting the brightness value of the document image. If the number of blocks is 25 or more, the brightness value of the document image is adjusted to adjust the watermark information. It can be determined that it is necessary to embed. The image density determined by the image density determination unit 120 is provided to the image density adjustment unit 122.

  Returning to FIG. 1, the embedding information creation unit 114 acquires the embedding information 116 and creates data to be embedded in the document image as watermark information. As described above, when the watermark information to be embedded in the document image is the printer identification information that identifies the printer, the user ID of the printer, the device ID of the PC that requested the printing, the date and time, and the print instruction target print The device ID of the machine may be created as embedded information. The embedded information created by the embedded information creating unit 114 is provided to the watermark information generating unit 112.

  The watermark information generation unit 112 generates a watermark image using a background pattern from the embedded information provided by the embedded information generation unit 114. The image density adjustment unit 122 adjusts the image density of the document image to the image density provided from the image density determination unit 120.

  The watermark information embedding unit 110 embeds the watermark information generated by the watermark information generation unit 112 in the document image adjusted by the image density adjustment unit 122, and generates a watermarked document image using a background pattern. The watermarked document image generated by the watermark information embedding unit 110 is provided to the printing unit 118. The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100a to print the watermarked document image provided by the watermark information embedding unit 110.

  The functional configuration of the watermark information embedding device 100b has been described above. Next, a watermark information embedding method in the watermark information embedding device 100b will be described with reference to FIG.

<4. Embedding watermark information>
FIG. 8 is a flowchart showing the watermark information embedding method according to the present embodiment. First, document data is imaged and a document image is created (S201). Based on the pixel information of the document image created in step S201, the image density of the document image in which the watermark information can be embedded is set (S202). Image processing of the document image is performed according to the image density set in step S202 (S203). In step S203, the image density of the document image is adjusted to the image density set in step S202.

  The embedded information creation unit 114 acquires the user ID of the printer, the device ID of the PC used by the printer, the date, etc., and creates embedded information (S204). A watermark image using a tint block is generated from the embedded information created in step S204 (S205).

  Then, the watermark information generated in step S205 is embedded in the document image processed in step S203 to generate a watermarked document image (S206). The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100a to print the watermarked document image generated in step S206 (S207).

  The watermark information embedding method according to the second embodiment has been described above. With the above configuration, even if the watermark information is embedded in the document image, the information cannot be read and the information cannot be restored. By increasing the brightness value of the document image and reducing the density of the document image, A watermarked document image with improved embedded watermark reading performance can be generated. However, if the density of the document image is too low, the reading performance of the watermark information is improved, but the readability may be significantly reduced.

  Therefore, the third embodiment provides a watermark information embedding device that can improve watermark reading performance and reduce deterioration in readability by adjusting the watermark density and the image density of a document image.

(Third embodiment)
In the third embodiment, the watermark information can be embedded in accordance with the image density of the document image, and the image density of the document image in which the watermark information is embedded and the watermark information embedded in the document image so as not to impair readability. The description will be made by applying the watermark information generating apparatus of the present invention to the watermark information embedding apparatus 100c capable of adjusting the watermark density. First, the functional configuration of the watermark information generating apparatus 100c according to the third embodiment will be described with reference to FIG.

<5. Functional configuration of watermark information embedding device>
FIG. 9 is a block diagram showing a functional configuration of the watermark information embedding device 100c according to the present embodiment. As shown in FIG. 9, the watermark information embedding device 100c includes document data 102, a document data imaging unit 104, a pixel information detecting unit 106, a watermark information embedding unit 110, a watermark information generating unit 112, an embedding process. The information creating unit 114, the embedded information 116, the printing unit 118, the image density adjusting unit 122, the density determining unit 124, and the like are included.

  The document data 102 is electronic data printed on a paper medium, and is data created by a document creation tool or the like. The document data 102 is data that can be visually recognized when printed on a paper medium. The document data imaging unit 104 has a function of imaging the document data 102 and creating a document image. The document image created by the document data imaging unit 104 is provided to the pixel information detection unit 106 and the image density adjustment unit 122.

  The pixel information detection unit 106 has a function of detecting pixel information of the document image provided by the document data imaging unit 104. Here, the pixel information is information such as image density and color of the document image. The pixel information detected by the pixel information detection unit 106 may be pixel information for the entire document image, or the document image is divided into a plurality of areas, and the pixel information for each divided area is detected. May be. For example, when the pixel information detected by the pixel information detection unit 106 is black pixel ratio information, the black pixel ratio relative to the entire document image may be detected, or the black pixel ratio may be detected for each divided area. May be detected. Pixel information detected by the pixel information detection unit 106 is provided to the density determination unit 124.

  The density determination unit 124, based on the pixel information detected by the pixel information detection unit 106, the watermark density of the watermark information embedded in the document image and the document in which the watermark information is embedded so that the watermark information can be embedded in the document image. A function of determining an image density of the image; For example, when a watermark pattern is represented by black pixels, whether or not the embedded watermark information can be read correctly is determined by the black pixel ratio of the document image. If the percentage of black pixels is large, it may not be read correctly even if watermark information is embedded. In that case, the watermark information can be correctly read by adjusting the watermark density of the watermark information or adjusting the image density of the document image. Further, by adjusting the watermark density and the image density, it is possible to reduce a decrease in readability.

  For example, as shown in FIG. 10, when the black pixel density 210 is less than 20%, the watermark density 212 is set to the default value “2”, the image density 214 is not adjusted, and the luminance value is “0”. Watermark information may be embedded in the document image. On the other hand, when the black pixel density 210 is 20% or more, the watermark density and the image density corresponding to the black pixel density may be determined by density determination processing described later.

  An example of a watermark density determination method in the density determination unit 124 when the black pixel density of the document image is 20% or more will be described. FIG. 11 is a flowchart showing a watermark density determination method in the density determination unit 124. Usually, the watermark density is set to the default value “2”, and the luminance value of the image density is “0” (step S250). First, it is determined whether the black pixel density of the document image is 20% or more (S252). If the black pixel density is less than 20% in step S252, the watermark density “2” and the luminance value “0” of the image density are set. That is, watermark information is generated with a normal watermark density, and the watermark information is embedded without adjusting the density of the document image.

  If it is determined in step S252 that the black pixel density of the document image is 20% or more, 2 is added to the watermark density (S254). If it is determined that the watermark density set in step S254 is less than 10 (S256), it is determined whether the watermark information can be embedded with the watermark density set in step S254 (S260). If it is determined in step S256 that the watermark density is 10 or more, 34 is added to the image density, and the watermark density is set to the default value 2. Then, it is determined whether or not watermark information can be embedded in the document image having the image density set in step S258 (S260).

  As described above, the processing for setting the watermark density and the image density is repeated, and when it is determined that the watermark information can be embedded (S260), the watermark density and the image density are set (S262).

  The density determination process will be described with reference to the matrix in FIG. In FIG. 12, the character “dragon” is represented in each matrix, and the black pixel density in the matrix is 20% or more. Normally, the watermark density is 2 and the character density is 0. In this case, the watermark information cannot be embedded so that the watermark information can be read. Therefore, 2 is added to the watermark density to determine whether the watermark information can be embedded. If it is determined that the watermark information cannot be embedded even when the watermark density is 10, 34 is added to the character density, and the watermark density is set to the default value 2. This process is repeated to determine the density that can be embedded.

  In the matrix shown in FIG. 12, watermark information that can read information cannot be embedded in the range 22, and watermark information that can read information can be embedded in the range 23. Therefore, when the watermark density is 6 and the character density is 68, watermark information can be embedded. The density determination unit 124 determines the watermark density as 6 and the text density 68, provides the determined watermark density to the watermark density generation unit 112, and provides the text density value to the image density adjustment unit 122.

  As shown in FIG. 12, in the range 23, it is possible to embed watermark information that can read the information. However, in order to minimize the deterioration of the readability, the watermark density 6 and the character density 68 are set. It is necessary to set the density value. As described above, the density determination process can determine the watermark density and the image density that can read the information and can reduce the readability.

  Returning to FIG. 9, the embedded information creation unit 114 acquires the embedded information 116 and creates data to be embedded in the document image as watermark information. As described above, when the watermark information to be embedded in the document image is the printer identification information that identifies the printer, the user ID of the printer, the device ID of the PC that requested the printing, the date and time, and the print instruction target print The device ID of the machine may be created as embedded information. The embedded information created by the embedded information creating unit 114 is provided to the watermark information generating unit 112.

  The watermark information generation unit 112 generates a watermark image using a background pattern from the embedded information provided by the embedded information generation unit 114. In addition, the watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density determined by the watermark density determination unit. The image density adjustment unit 122 adjusts the image density of the document image to the image density provided from the image density determination unit 120.

  The watermark information embedding unit 110 embeds the watermark information generated by the watermark information generation unit 112 in the document image adjusted by the image density adjustment unit 122, and generates a watermarked document image using a background pattern. The watermarked document image generated by the watermark information embedding unit 110 is provided to the printing unit 118. The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100a to print the watermarked document image provided by the watermark information embedding unit 110.

  The functional configuration of the watermark information embedding device 100c has been described above. Next, a watermark information embedding method in the watermark information embedding device 100c will be described with reference to FIG.

<6. Embedding watermark information>
FIG. 13 is a flowchart showing the watermark information embedding method according to the present embodiment. First, document data is imaged and a document image is created (S301). Based on the pixel information of the document image created in step S301, the image density and watermark density of the document image in which the watermark information can be embedded are determined (S302). The image density determined in step S302 is set (S303), and the document image is processed according to the image density (S304). In step S304, the image density of the document image is adjusted to the image density set in step S303.

  The embedded information creation unit 114 acquires the user ID of the printer, the device ID of the PC used by the printer, the date, and the like, and creates embedded information (S306). A watermark image using a background pattern is generated from the embedded information created in step S306 (S307). The watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density set in step S302.

  Then, the watermark information generated in step S307 is embedded in the document image processed in step S304 to generate a watermarked document image (S307). The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100c to print the watermarked document image generated in step S308 (S309). Note that after the density is determined in step S302, the image processing of the document image is performed and the watermark information is generated. However, the image processing of the document image and the generation of the watermark information may be performed simultaneously. The watermark information embedding method according to the third embodiment has been described above. With the above configuration, depending on the ratio of the black pixel density of the document image, even for documents that cannot embed watermark information, the watermark is enhanced by increasing the watermark density value and increasing the brightness value of the document image. Thus, the watermark reading performance can be improved. Also, by setting both the watermark density and the image density of the document image, it is possible to embed watermark information and generate a watermarked document image with reduced readability.

(Fourth embodiment)
In the fourth embodiment, the watermark information embedding device according to the present invention is applied to a watermark information embedding device 100d that can invert a document image in black and white and embed watermark information in accordance with the proportion of black pixels in the document image. To do. First, the functional configuration of the watermark information embedding device 100d according to the fourth embodiment will be described with reference to FIG.

<7. Functional configuration of watermark information embedding device>
FIG. 14 is a block diagram showing a functional configuration of the watermark information embedding device 100d according to the present embodiment. As shown in FIG. 14, the watermark information embedding device 100b includes document data 102, a document data imaging unit 104, a pixel information detection unit 106, a watermark information embedding unit 110, a watermark information generating unit 112, and an embedding. The information creating unit 114, the embedded information 116, the printing unit 118, the image density determining unit 120, the image density adjusting unit 122, and the like are included.

  The watermark information embedding device 100d according to the present embodiment has substantially the same functional configuration as that of the watermark information embedding device 100b according to the second embodiment, and therefore, differences from the second embodiment will be mainly described.

  The image density determination unit 120 instructs the image density adjustment unit 122 to invert the document image in black and white when the ratio of black pixels detected by the image information detection unit 106 is a predetermined ratio. It has a function. Further, as in the second embodiment, the black pixel ratio may be detected and the image density may be determined for a document image that is reversed in black and white.

  For example, as shown in FIG. 25, it is impossible to embed watermark information in a document image 25 having a large proportion of black pixels. Further, as described in the second embodiment, it is possible to embed watermark information by reducing the image density of the document image 25, that is, by increasing the luminance value of the image. It is necessary to increase the brightness value. Therefore, in the case of the document image 25 having a large proportion of black pixels shown in FIG. 15, it is possible to reduce a decrease in readability of the watermarked document image by performing the black and white inversion process.

  As shown in FIG. 16, the image density determination unit 120 according to the present embodiment embeds watermark information without image processing when the black pixel density 216 is less than 20%. If the black pixel density is 20% to 80%, the watermark information cannot be embedded, and an error is generated without performing the watermark information embedding process. Further, when the black pixel density 216 is 80% or more, black and white inversion is performed, and the image density is determined according to the black pixel density after the black and white inversion. The image density adjusting unit 122 performs black and white reversal of the document image when instructed by the image density determining unit 120 to perform black and white reversal.

  The functional configuration of the watermark information embedding device according to the present embodiment has been described above. In the present embodiment, the case where only the image density is determined by the image density determination unit 120 has been described. However, the present invention is not limited to such an example, and as in the first and third embodiments, the document is inverted in black and white by adjusting the watermark density. It may be embedded in an image. Next, the watermark information embedding method according to the present embodiment will be described with reference to FIG.

<8. Embedding watermark information>
FIG. 17 is a flowchart showing the watermark information embedding method according to the present embodiment. First, document data is imaged to create a document image (S401). Based on the pixel information of the document image created in step S401, it is determined whether or not it is necessary to invert the document image (S402). If it is determined in step S402 that black and white reversal is necessary, the black and white reversal of the document image is performed (S403). Thereafter, similarly to the third embodiment, the black pixel density of the document image that has been reversed in black and white in step S403 can be detected, and the watermark density and the image density corresponding to the black pixel density can be set.

  The watermark information embedding method according to the fourth embodiment has been described above. With the above configuration, it is possible to embed watermark information even in a document image with a black pixel density of 80% or more without impairing readability.

(Fifth embodiment)
In the fifth embodiment, depending on the ratio of the black pixels of the document image, the watermark density adjustment, the document image density adjustment, the watermark density adjustment and the document image density adjustment are performed together, The watermark information embedding device of the present invention is applied to a watermark information embedding device 100e that can embed watermark information by an adjustment method suitable for a document image. First, the functional configuration of the watermark information embedding device 100e according to the fifth embodiment will be described with reference to FIG.

<9. Functional configuration of watermark information embedding device>
FIG. 18 is a block diagram showing a functional configuration of the watermark information embedding device 100e according to the present embodiment. As shown in FIG. 18, the watermark information embedding device 100e includes document data 102, a document data imaging unit 104, a pixel information detection unit 106, a watermark information embedding unit 110, a watermark information generating unit 112, and an embedding. The information generation unit 114, the embedded information 116, the printing unit 118, the image density adjustment unit 122, the density determination unit 124, the density adjustment method selection unit 130, and the like are included.

  Document data 102, document data imaging unit 104, pixel information detection unit 106, watermark information embedding unit 110, watermark information generation unit 112, and embedded information creation unit provided in watermark information embedding device 100e according to the present embodiment. 114, the embedding information 116, the printing unit 118, the image density adjusting unit 122, and the density determining unit 124 have substantially the same functional configuration as the watermark information embedding device 100c according to the third embodiment. The part different from the form will be mainly described. As a configuration different from the third embodiment, a density adjustment method selection unit 130 is provided. The image density adjusting unit 122 also has a function of reversing the image in black and white, like the image density adjusting unit 122 provided in the watermark information embedding device 100d of the fourth embodiment.

  Based on the pixel information detected by the pixel information detection unit 106, the density adjustment method selection unit 130 performs watermark density adjustment, image density adjustment of the document image, watermark density adjustment and document image density. It is determined whether the adjustment is performed together, and a processing method suitable for the document image is selected. For example, the density adjustment method may be selected according to the ratio of black pixels in the document image. For example, as shown in FIG. 19, when the black pixel density 220 is less than 20%, it is not necessary to adjust the density. Therefore, the density adjustment method 224 is determined to be “none”, and the image density of the document image is determined. The watermark information is embedded without changing the default watermark density. When the black pixel density 220 is 20% or more and less than 25%, the density adjustment method 224 for adjusting the watermark density is selected. When the black pixel density 220 is 25% or more and less than 75%, the watermark density and the image density are selected. The density adjustment method 224 for adjusting both of the above and the like is selected. When the black pixel density 220 is 75% or more and less than 80%, the document image is reversed in black and white and the density adjustment method 224 for adjusting the watermark density is selected, and when the black pixel density 220 is 80% or more. Selects the density adjustment method 224 so that only the black and white inversion of the document image is performed.

  The density determination unit 124 uses the density adjustment method selected by the density adjustment method selection unit 130, and similarly to the third embodiment, the watermark density and / or the image density based on the pixel information detected by the pixel information detection unit 106. To decide. For example, when the watermark density adjustment method is selected by the density adjustment method selection unit 130, the density determination unit 124 determines the watermark density and provides the watermark density to the watermark information generation unit 112. Further, when the watermark density adjustment method and the image density adjustment method are selected by the density adjustment method selection unit 130, the watermark density and the image density are determined, and the watermark density is provided to the watermark information generation unit 112. The density is provided to the image density adjustment unit 122. When the density adjustment method selection unit 130 selects black and white inversion and watermark density adjustment method, the image density adjustment unit 122 is instructed to invert the image in black and white, determines the watermark density, and uses the watermark density as the watermark. This is provided to the information generation unit 112.

  In this way, by setting a density adjustment method according to the black pixel density in advance, it is possible to prevent a wasteful process of performing density adjustment that makes it impossible to embed watermark information. In addition, it is possible to perform density adjustment processing so that watermark information can be embedded in a document image, and it is possible to minimize deterioration in readability.

  The functional configuration of the watermark information embedding device 100e has been described above. Next, a watermark information embedding method in the watermark information embedding device 100e will be described with reference to FIG.

<10. Embedding watermark information>
FIG. 20 is a flowchart showing a watermark information embedding method according to the present embodiment. First, document data is imaged and a document image is created (S501). A density adjustment method is selected based on the pixel information of the document image created in step S501 (S502). As described above, the density adjustment method selected in step S502 can embed watermark information from watermark density adjustment, image density adjustment, watermark density adjustment, image density adjustment, and the like, and reduces readability degradation. A density adjustment method is selected. After the density adjustment method is selected in step S502, it is determined whether or not the image density needs to be adjusted (S503). If it is determined in step S503 that the image density needs to be adjusted, the image density is set (S504), and image processing of the document image is performed according to the image density (S505). In step S505, the image density of the document image is adjusted to the image density set in step S304. If black / white reversal is selected for the document image in step S502, the black / white reversal of the document image is performed in step S505.

  Next, it is determined whether or not the watermark density needs to be adjusted (S506). If it is determined in step S506 that the watermark density needs to be adjusted, the watermark density is set (S507).

  The embedded information creation unit 114 acquires the user ID of the printer, the device ID of the PC used by the printer, the date, and the like, and creates embedded information (S508). A watermark image using a background pattern is generated from the embedded information created in step S508 (S509). The watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density set in step S507.

  Then, the watermark information generated in step S509 is embedded in the document image processed in step S505 to generate a watermarked document image (S510). The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100e to print the watermarked document image generated in step S510 (S511). The watermark information embedding method according to the fifth embodiment has been described above.

  In the fifth embodiment, a density adjustment method most suitable for a document image in which watermark information is embedded is selected. However, in the watermark information embedding device according to the fifth embodiment, there is a possibility that a watermarked document image that does not meet the wishes of the user performing the printing process is generated and printed. Therefore, in the sixth embodiment, a watermark information embedding device that allows a user to select a density adjustment method will be described.

(Sixth embodiment)
In the sixth embodiment, a density adjustment method is selected by the user, and the watermark density embedding device 100f that determines the watermark density and / or the image density based on the pixel information of the document image using the selected density adjustment method is used in the present embodiment. An explanation will be given by applying the watermark information embedding device of the invention. First, the functional configuration of the watermark information embedding device 100f according to the sixth embodiment will be described with reference to FIG.

<11. Functional configuration of watermark information embedding device>
FIG. 21 is a block diagram showing a functional configuration of the watermark information embedding device 100f according to the present embodiment. As shown in FIG. 21, the watermark information embedding device 100f includes document data 102, a document data imaging unit 104, a pixel information detecting unit 106, a watermark information embedding unit 110, a watermark information generating unit 112, and an embedding. The information generation unit 114, the embedded information 116, the printing unit 118, the image density adjustment unit 122, the density determination unit 124, the density adjustment method selection unit 130, the input unit 132, and the like are included.

  Document data 102, document data imaging unit 104, pixel information detection unit 106, watermark information embedding unit 110, watermark information generation unit 112, and embedded information creation unit provided in the watermark information embedding device 100f according to the present embodiment. 114, the embedding information 116, the printing unit 118, the image density adjusting unit 122, the density determining unit 124, and the density adjusting method selecting unit 130 have substantially the same functions as those of the watermark information embedding device 100e according to the fifth embodiment. Since it is a structure, a different part from 5th Embodiment is mainly demonstrated. As an arrangement different from that of the fifth embodiment, an input unit 132 is provided.

  The input unit 132 is an interface having a function of accepting user input. The user can select and input a density adjustment method by operating the input unit 132. For example, when it is not desired to change the image density of the document image, a density adjustment method for adjusting the watermark density by the watermark density adjustment is selected. In addition, when it is desired to embed watermark information without reversing the document image in black and white, a method for adjusting only the watermark density and the image density of the document image may be selected. The density adjustment method selected by the user via the input unit 132 is provided to the density adjustment method selection unit 130.

  The density adjustment method selection unit 130 selects a required density adjustment method according to the pixel information of the document image from the density adjustment methods selected by the user. For example, when a watermark density adjustment method and an image density adjustment method are selected by the user, a watermarked document image that can embed watermark information and reduce readability reduction by simply adjusting the watermark density is created. If it is possible, select only the watermark information adjustment method. The density determination unit 124 has substantially the same function as that of the fifth embodiment, and thus description thereof is omitted.

  Also, the watermark information embedding method according to the present embodiment is expressed in substantially the same manner as in the fifth embodiment except that the density adjustment method is set by the user, and thus description thereof is omitted. In this way, by selecting the density adjustment method by the user, the appearance tendency of the printed watermarked document image can be brought close to what the user desires.

(Seventh embodiment)
In the seventh embodiment, when the document in which the watermark information is embedded is a color document, the watermark information embedding device 100g according to the present invention can be embedded in the watermark information embedding device 100g capable of selecting and embedding an optimal watermark color for the color document. A description will be given by applying the apparatus.

  FIG. 22 is a block diagram showing a functional configuration of the watermark information embedding device 100g according to the present embodiment. As shown in FIG. 22, the watermark information embedding device 100g includes document data 102, a document data imaging unit 104, a pixel information detection unit 106, a watermark information embedding unit 110, a watermark information generating unit 112, an embedding process. The information generation unit 114, the embedded information 116, the printing unit 118, the image density adjustment unit 122, the density determination unit 124, the watermark color selection unit 134, and the like are included.

  Document data 102, document data imaging unit 104, pixel information detection unit 106, watermark information embedding unit 110, watermark information generation unit 112, and embedded information creation unit provided in the watermark information embedding device 100g according to the present embodiment. 114, the embedding information 116, the printing unit 118, the image density adjusting unit 122, and the density determining unit 124 have substantially the same functional configuration as the watermark information embedding device 100c according to the third embodiment. The part different from the form will be mainly described.

  The pixel information detection unit 106 according to the present embodiment can detect not only black pixel density but also color pixel distribution, density, and color information. The watermark color selection unit 134 selects the watermark color selected by the user. The watermark color selected by the watermark color selection unit 134 may be selected from the three primary colors cyan, magenta, and yellow, or a color image (warm and cold) may be selected. .

  The density determination unit 124 determines the density of the watermark color selected by the watermark color selection unit 134 based on the pixel information of the color image detected by the pixel information detection unit 106. For example, when cyan is selected by the watermark color selection unit 134, it is determined whether or not the embedded information can be read when a cyan color watermark is embedded in the document image. Then, the cyan density at which watermark information can be read is determined. In addition, when the ratio of cyan color pixels is large in the document image, even if a cyan watermark is embedded, the embedded information cannot be read. Therefore, the watermark color may be set to black.

  Further, the density determination unit 124 may set a color that is a complementary color of the color pixels frequently used in the color image as a watermark color. For example, when the ratio of cyan color pixels is large in the document image, magenta or red watermark color which is a complementary color of cyan may be set. By setting a complementary color of a color frequently used in a document image as a watermark color, it is possible to set a watermark color embedded in a color document to a watermark color from which watermark information can be read.

  The watermark information generation unit 112 acquires the watermark color and watermark density information determined by the density determination unit 124, and adjusts the watermark color and watermark density of the generated watermark image. Thus, it is possible to select a watermark color suitable for a color document, and it is possible to embed a watermark using a background pattern having a watermark color desired by the user so that information can be read. The functional configuration of the watermark information embedding device 100g according to the present embodiment has been described above. Next, a watermark information embedding method in the watermark information embedding device 100g will be described with reference to FIG.

<12. Embedding watermark information>
FIG. 23 is a flowchart showing a watermark information embedding method according to the present embodiment. First, document data is imaged and a document image is created (S601). Next, the watermark color selected by the user is acquired (S602). Based on the pixel information of the document image created in step S601, it is determined whether the watermark color acquired in step S602 needs to be adjusted (S603). If it is determined in step S603 that the watermark color needs to be adjusted, the watermark color is adjusted (S604). If it is determined in step S603 that the watermark density needs to be adjusted, the watermark density is also adjusted in step S604.

  The embedded information creation unit 114 acquires the user ID of the printer, the device ID of the PC used by the printer, the date, and the like, and creates embedded information (S605). A watermark image using a background pattern is generated from the embedded information created in step S605 (S606). The watermark information generation unit 112 adjusts the watermark color and watermark density of the watermark image according to the watermark color and watermark density set in step S604.

  Then, the watermark information generated in step S606 is embedded in the document image created in step S601 to generate a watermarked document image (S607). The printing unit 118 instructs the printing machine connected to the watermark information embedding device 100g to print the watermarked document image generated in step S607 (S608). The watermark information embedding method according to the fifth embodiment has been described above.

  The watermark information employed in the first to seventh embodiments is information that is expressed in a fine dot pattern for a printed material and is embedded so as to be superimposed on a printed image or character on the entire background of the printed material. The watermark information employed in the present invention is not limited to such an example. For example, it may be watermark information in which information is embedded in the outline of a figure or character. When embedding information in the outline of a figure or character, it is necessary to appropriately extract the outline of the figure or character in order to read the information correctly. Therefore, in the eighth embodiment, there is provided a watermark information embedding device capable of embedding watermark information in the character outline of a document image having a complex pattern or the like in the background of the character image.

(Eighth embodiment)
In the eighth embodiment, the watermark information according to the present invention is added to the watermark information embedding device 100h that can embed watermark information so that the watermark information can be read by adjusting the respective densities of characters and background included in the document. An explanation will be given by applying an embedding device. First, the functional configuration of the watermark information embedding device 100h according to the eighth embodiment will be described with reference to FIG.

<13. Functional configuration of watermark information embedding device>
FIG. 24 is a block diagram showing a functional configuration of the watermark information embedding device 100h according to the present embodiment. As shown in FIG. 24, the watermark information embedding device 100h includes a document data 102, a document data imaging unit 104, a watermark information embedding unit 110, a watermark information generating unit 112, an embedded information creating unit 114, an embedding It includes information 116, a printing unit 118, an image density adjustment unit 122, a density determination unit 124, an image separation unit 140, and the like.

  Document data 102, document data imaging unit 104, watermark information embedding unit 110, watermark information generating unit 112, embedded information creating unit 114, embedded information 116, and the like included in watermark information embedding device 100 h according to the present embodiment. The printing unit 118, the image density adjustment unit 122, and the density determination unit 124 have substantially the same functional configuration as that of the watermark information embedding device 100c according to the third embodiment, and therefore mainly different from the third embodiment. explain. As a configuration different from that of the third embodiment, an image separation unit 140 is provided.

  The image separation unit 140 has a function of separating a character and a background by converting a shaded image into a white and black binary image. The image separation unit 140 designates a certain density of the document image as a reference density, and converts pixels having a higher density than the reference to black and pixels having a lower density than the reference to white. The density used as a reference for processing is referred to as a threshold, and this threshold can be calculated from the brightness value histogram by measuring the brightness value histogram of the document image. The luminance value histogram is a graph showing the luminance value of the document image and the frequency of appearance of the luminance value. Examples of the threshold calculation method include a discriminant analysis method and a mode method. However, the threshold value calculation method is not limited to this example, and the threshold value may be calculated by other methods.

  The image separation unit 140 calculates a threshold value for separating the character and the background of the document image, and separates the background and the character. As shown in FIG. 26, for example, when the document image is an image including a character and a background like the image 26, the document image is separated into a character image 27 and a background image. The character image 27 is an image having a density of 0 (white) except for pixels in the character portion. The background image 28 is an image in which the density of character pixels is 0, or an image that is an average value of background pixel values in the vicinity of the character. The image separation unit 140 detects pixel information of each of the separated character image and background image and provides the pixel information to the density determination unit 124.

  The density determining unit 124 determines the density of the character image and the density of the document image that can correctly read the embedded information when the watermark information is embedded in the outline portion of the character image. For example, when embedding watermark information in the outline portion of a character image and reading the information, the character portion and the background portion are separated by a method such as binarization and the watermark information embedded in the character image is read. Can do. When embedding watermark information, it is necessary to separate the brightness distribution of the characters and the background in advance so as not to impair the sense of discomfort when reading the watermark information so that the character image and the background image are correctly separated. is there. Therefore, the density determination unit 124 determines the respective densities so as to increase the density of the character and decrease the density of the background so that the character and the background are correctly separated according to the luminance distribution of the character image and the background image. To do. For example, as shown in FIG. 27, the density of the character image 29 is determined so that the character density of the character image 29 in which the watermark information is embedded is increased like the character image 30.

  Further, the density of the background image 31 is determined so that the background density of the background image 31 is lowered like the background image 32. The character density and the background density may be set so that the average value of the character density value and the average value of the background density value are separated by a certain distance or more. Similarly to the method described in the third embodiment, it is determined whether or not the watermark information can be embedded in the document image. If the watermark information cannot be embedded, the density of the character image is maximized and the watermark information can be read correctly. You may make it reduce the density | concentration of a background image until it becomes the density | concentration which can be performed.

  The watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density determined by the density determination unit 124. The image density adjusting unit 122 adjusts the density of the character image to the character density determined by the density determining unit 124. Further, the density of the background image is adjusted to the background density determined by the density determination unit 124.

  The watermark information embedding unit 110 embeds watermark information in the character image, and synthesizes the character image in which the watermark information is embedded and the background image. The image composition can be performed by replacing the portion of the character image with a density value of 0 (white) with the same background image pixel. As shown in FIG. 28, the watermarked document image 35 is generated by synthesizing the character image 33 embedded with the watermark and the background image 34.

  As described above, when information is embedded in the outline of a character, the embedded information must be read so that the character and the background can be easily separated. According to the above configuration, it is possible to embed watermark information in the outline portion of the character image by separating the character and background of the document image, increasing the density of the character image, and decreasing the density of the background image. Further, the background density existing near the character may be particularly reduced to facilitate embedding the watermark information in the outline portion of the character.

  The functional configuration of the watermark information embedding device 100h has been described above. Next, a watermark information embedding method in the watermark information embedding device 100h will be described with reference to FIG.

<14. Embedding watermark information>
FIG. 25 is a flowchart showing a watermark information embedding method according to the eighth embodiment. First, document data is imaged and a document image is created (S701). Based on the pixel information of the document image created in step S701, the character and the background are separated (S702). In step S702, the density of the separated character image, the density of the background image, the watermark density, and the like are determined. The embedded information creation unit 114 acquires the user ID of the printer, the device ID of the PC used by the printer, the date, and the like, and creates embedded information (S703).

  A watermark image using a background pattern is generated from the embedded information created in step S703 (S704). In step S704, the created embedding information may be embedded in the character image. The watermark information generation unit 112 adjusts the watermark density of the watermark image according to the watermark density set in step S702. Next, the density of the character image is corrected to the character density set in step S702, and the density of the background image is corrected to the set background density.

  Then, the watermarked character image corrected in step S705 and the background image are synthesized (S706). In the watermarked character image created in step S704, some pixels in the background portion (white) of the character image may be the same color as the character, or some pixels in the character color portion may be white. However, even when some of the pixels in the character color portion are white, the pixel value of the portion corresponding to the character is generated in the background image generation character in step S702 when the surrounding background is generated with the average value of the measure. In step S706, by combining the watermarked character image and the background image, the portion where the character pixel is changed to white is replaced with the background pixel, and the document image can be made to look natural.

  An instruction is given to print the watermarked document image synthesized in step S706 on a printing machine connected to the watermark information embedding device 100h (S707).

  The watermark information embedding method according to the eighth embodiment has been described above. With the above configuration, it is possible to embed watermark information in the outline portion of the character image by separating the character and background of the document image, increasing the density of the character image, and decreasing the density of the background image.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Understood.

  The present invention can be applied to a watermark information embedding device, a watermark information embedding method, and a computer program, and particularly applicable to a watermark information embedding device capable of embedding watermark information in document data having a pattern on the entire background. .

It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 1st Embodiment of this invention. It is explanatory drawing explaining the watermark information embedded in the document image in the embodiment. It is explanatory drawing explaining the black pixel density and watermark density in the embodiment. It is a flowchart which shows the watermark information embedding method in the embodiment. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 2nd Embodiment of this invention. It is explanatory drawing explaining the watermark information embedded in the document image in the embodiment. It is explanatory drawing explaining the black pixel density and image density in the embodiment. It is a flowchart which shows the watermark information embedding method in the embodiment. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 3rd Embodiment of this invention. It is explanatory drawing explaining the black pixel density in the same embodiment, a watermark density, and an image density. It is a flowchart which shows the watermark density determination method in the embodiment. It is explanatory drawing explaining the watermark density determination processing in the embodiment. It is a flowchart which shows the watermark information embedding method in the embodiment. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 4th Embodiment of this invention. It is explanatory drawing explaining the document image with many ratios of the black pixel in the embodiment. It is explanatory drawing explaining the black pixel density and image adjustment method in the embodiment. It is a flowchart which shows the watermark information embedding method in the embodiment. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 5th Embodiment of this invention. It is explanatory drawing explaining the black pixel density and density adjustment method in the embodiment. It is a flowchart which shows the watermark information embedding method in the embodiment. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 6th Embodiment of this invention. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 7th Embodiment of this invention. It is a flowchart which shows the watermark information embedding method in the embodiment. It is a block diagram which shows the function structure of the watermark information embedding apparatus concerning the 8th Embodiment of this invention. It is a flowchart which shows the watermark information embedding method in the embodiment. It is explanatory drawing explaining the separation method of the document image in the embodiment. It is explanatory drawing explaining the density adjustment method of the character image and background image in the embodiment. It is explanatory drawing explaining the synthesis | combination of the character image and background image in the embodiment.

Explanation of symbols

100a-h Watermark information embedding device 106 Image information detection unit 108 Watermark density determination unit 112 Watermark information generation unit 120 Image density determination unit 122 Image density adjustment unit 124 Density determination unit 140 Image separation unit

Claims (19)

A watermark information embedding device that embeds watermark information into a document image by digital watermarking:
A pixel information detection unit for detecting pixel information of the document image;
A watermark density determination unit that determines a watermark density of watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detection unit;
A watermark information generation unit that generates watermark information to be embedded in the document image according to the watermark density determined by the watermark density determination unit;
A watermark information embedding unit that embeds watermark information generated by the watermark information generating unit in a document image;
A watermark information embedding device comprising:   The watermark density determining unit determines a watermark density of watermark information that can be embedded in the document image when a black pixel ratio included in the pixel information of the document image is equal to or greater than a predetermined ratio; The watermark information embedding device according to claim 1. The pixel information detection unit divides the document image into a plurality of watermark embedding areas, detects pixel information for each watermark embedding area,
The watermark density determination unit determines a watermark density of watermark information that can be embedded in the document image based on pixel information for each watermark embedding area of the document image detected by the pixel information detection unit. The watermark information embedding device according to claim 1. The pixel information detection unit detects a black pixel ratio for each watermark embedding area,
The watermark density determination unit calculates the number of non-embeddable areas in which the ratio of black pixels for each embedding area is equal to or greater than a predetermined ratio, and when the number of non-embeddable areas is equal to or greater than the predetermined number, The watermark information embedding apparatus according to claim 3, wherein the watermark density of watermark information that can be embedded in the watermark information is determined.   The watermark according to claim 1, wherein the watermark density determination unit determines a watermark color of watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detection unit. Information embedding device. A watermark information embedding device that embeds watermark information into a document image by digital watermarking:
A pixel information detection unit for detecting pixel information of the document image;
An image density determination unit that determines an image density of the document image based on the pixel information detected by the pixel information detection unit so that the watermark information can be embedded;
An image density adjusting unit for adjusting the image density of the document image to the image density determined by the image density determining unit;
A watermark information embedding unit that embeds watermark information in the document image adjusted by the image density adjusting unit;
A watermark information embedding device comprising:   The image density determination unit determines the image density of the document image so that the watermark information can be embedded when the black pixel ratio included in the pixel information of the document image is equal to or higher than a predetermined ratio. The watermark information embedding device according to claim 6. The pixel information detection unit divides the document image into a plurality of watermark embedding areas, detects pixel information for each watermark embedding area,
The image density determination unit determines an image density of the document image so that the watermark information can be embedded based on pixel information for each watermark embedding area of the document image detected by the pixel information detection unit. The watermark information embedding device according to claim 6, wherein: The pixel information detection unit detects a black pixel ratio for each watermark embedding area,
The image density determination unit calculates the number of non-embeddable areas in which the ratio of black pixels for each embedding area is equal to or greater than a predetermined ratio, and when the number of non-embeddable areas is equal to or greater than the predetermined number, the watermark information The watermark information embedding apparatus according to claim 8, wherein the image density of the document image is determined so as to be embedded. (Embodiment 4: Black and white inversion)
The pixel information detection unit detects a ratio of black pixels included in the document image;
The watermark information embedding apparatus according to claim 6, wherein the image density adjustment unit reverses the document image in which the watermark is embedded when the ratio of the black pixels is a predetermined ratio. A watermark information embedding device that embeds watermark information into a document image by digital watermarking:
A pixel information detection unit for detecting pixel information of the document image;
Based on the pixel information detected by the pixel information detector, the watermark density of the watermark information embedded in the document image and the document image in which the watermark information is embedded so that the watermark information can be embedded in the document image. A density determination unit for determining image density;
A watermark information generation unit that generates watermark information to be embedded in the document image according to the watermark density determined by the density determination unit;
An image density adjusting unit for adjusting the image density of the document image to the image density determined by the density determining unit;
A watermark information embedding unit that embeds the watermark information generated by the watermark information generating unit in the document image adjusted by the image density adjusting unit;
A watermark information embedding device comprising:   The density determination unit is configured to include a watermark density of watermark information that can be embedded in the document image and a document in which the watermark information is embedded when a black pixel ratio included in the pixel information of the document image is equal to or greater than a predetermined ratio. 12. The watermark information embedding device according to claim 11, wherein the image density of the image is determined. The pixel information detection unit divides the document image into a plurality of watermark embedding areas, detects pixel information for each watermark embedding area,
The density determination unit embeds the watermark density of the watermark information that can be embedded in the document image and the watermark information based on the pixel information for each watermark embedding area of the document image detected by the pixel information detection unit. 12. The watermark information embedding apparatus according to claim 11, wherein an image density of the document image is determined. The pixel information detection unit detects a black pixel ratio for each watermark embedding area,
The density determination unit calculates the number of non-embeddable areas in which the ratio of black pixels for each embedding area is equal to or greater than a predetermined ratio, and when the number of non-embeddable areas is equal to or greater than the predetermined number, 12. The watermark information embedding apparatus according to claim 11, wherein a watermark density of watermark information that can be embedded and an image density of the document image in which the watermark information is embedded are determined. The pixel information detection unit detects a ratio of black pixels included in the document image;
12. The watermark information embedding apparatus according to claim 11, wherein the image density adjusting unit reverses the document image in which the watermark is embedded in black and white when the ratio of the black pixels is a predetermined ratio.   The watermark according to claim 11, wherein the watermark density determination unit determines a watermark color of watermark information that can be embedded in the document image based on the pixel information detected by the pixel information detection unit. Information embedding device. An image separation unit that separates a character image and a background image included in the document image based on pixel information detected by the pixel information detection unit;
An image synthesis unit that synthesizes the character image and the background image separated by the image separation unit;
Further including
The density determining unit determines a character density of the character image and a background density of the background image so that watermark information can be embedded in the document image;
The image density adjustment unit adjusts the image density of the character image to the character density determined by the density determination unit, adjusts the image density of the background image to the background density,
The watermark information embedding unit embeds watermark information in the character image adjusted by the image density adjusting unit,
The information processing apparatus according to claim 11, wherein the image composition unit synthesizes the character image in which the watermark information is embedded and the background image. A watermark information embedding method for embedding watermark information in a document image with a digital watermark:
A pixel information detecting step for detecting pixel information of the document image;
Determining, based on the pixel information, a watermark density of the watermark information embedded in the document image and an image density of the document image in which the watermark information is embedded so that the watermark information can be embedded in the document image; ;
Generating watermark information to be embedded in the document image according to the watermark density, and adjusting the image density of the document image to the image density;
Embedding the watermark information in the document image having the adjusted image density;
A watermark information embedding method comprising: A computer program that causes a computer to function as a watermark information embedding device that embeds watermark information into a document image with a digital watermark:
Pixel information detection processing for detecting pixel information of the document image;
Based on the pixel information detected by the pixel information detector, the watermark density of the watermark information embedded in the document image and the document image in which the watermark information is embedded so that the watermark information can be embedded in the document image. Density determination processing for determining image density;
A watermark information generation process for generating watermark information to be embedded in the document image according to the watermark density determined by the density determination unit;
Image density adjustment processing for adjusting the image density of the document image to the image density determined by the density determination unit;
A watermark information embedding process for embedding the watermark information generated by the watermark information generation unit in the document image adjusted by the image density adjustment unit;
A computer program characterized by executing

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