JP4935466B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that superimposes a pattern (background pattern) representing predetermined information on a document image and outputs the document image.

  2. Description of the Related Art Conventionally, an image processing apparatus is used that converts information into a pattern according to a predetermined rule, superimposes the pattern on a document image, and outputs a document image in which the information is embedded. As the pattern, a tint block pattern, a barcode pattern, or the like is used.

  Patent Document 1 discloses an image processing apparatus that outputs a document image in which additional information such as document identification information is added to a document. The image processing apparatus disclosed in the document adds a pattern representing additional information to a manuscript in a size that cannot be visually identified by a general user, thereby improving the security by preventing falsification of the additional information. ing.

Patent Document 2 also discloses an image forming apparatus that outputs image data in which additional information is embedded. The image forming apparatus can appropriately decode the additional information from the result of printing a document in which a pattern representing the additional information is embedded by appropriately adjusting the conditions for embedding the additional information. The additional information is embedded in the document in a state where it is difficult to decode the additional information from the copy of the result. By doing so, it is possible to accurately determine whether the printed matter is a genuinely printed result or a copy of the result. This determination result helps to confirm the reliability of the information included in the printed matter.
Japanese Patent Application Laid-Open No. 06-022119 JP 2006166201 A

  However, the process of scanning a document in which a background pattern is embedded to detect the background pattern and reading the additional information indicated by the background pattern is not always performed with high accuracy. Therefore, it is desired to improve the reliability of reading additional information embedded in a document.

  Also, assuming that the amount of information that can be expressed in the tint block pattern per unit area of the document is constant, the amount of additional information that can be embedded is proportional to the area of the document. Actually, however, the area in the document from which the embedded additional information can be read out with high accuracy is limited to the light-colored area and the area where the change in color or shading is relatively poor. For this reason, the amount of additional information that can be embedded (the amount of information that can be read with high accuracy) differs for each document. Therefore, all of the additional information that the user desires to embed cannot be securely embedded in all the originals. For this reason, there are many examples in which reading fails even for particularly important additional information that is desired to be read reliably.

  In view of the above problems, the present invention distinguishes additional information embedded in a document as a background pattern, according to its importance, and in particular, an image that can improve the accuracy of reading a background pattern that indicates additional information with high importance. Providing a processing apparatus is a problem to be solved.

In one aspect, the present invention is an image processing apparatus that generates a supplementary information embedded document image by synthesizing a tint block pattern indicating additional information with an input original document image, and is included in the initial document image, An information embeddable area detection unit that detects an area in which a tint block pattern can be embedded, and an amount of embeddable additional information that is the amount of additional information that can be embedded is derived based on the area of the detected information embeddable area. An embeddable information amount calculation unit, an information embedding easy region detection unit that detects an area that is included in the original document image and is easy to embed a copy-forgery-inhibited pattern, and an easy embedding based on the area of the detected information embedding easy region An easy-to-embed information amount calculation unit that derives an easy-to-embed information amount that is the amount of additional information, an information importance level determination unit that determines the relative importance of information included in the additional information, and an original document Crest on image A background pattern composition unit for embedding turn has a central processing unit that controls the own device, a region implantable, the first probability reading success rate of the additional information relating to the background pattern embedded in the area of predetermined The above-described areas, which are easily embedded, are areas having a second or higher probability that the success in reading additional information related to the tint block pattern embedded in the area is higher than the first probability. write enable additional information amount, embedded easily additional information amount, and based on the relative importance, the information included in the additional information to determine the priority to be embedded as a background pattern, background pattern composition unit with the higher priority It embeds information as a background pattern to easily buried region preferentially, an image processing apparatus for generating an additional information embedding document image.

In one aspect of the present invention, when the amount of additional information that can be embedded is less than the amount of additional information, the background pattern composition unit preferentially embeds information having a relatively high importance level as a background pattern in the original document image. It is preferable.

In one aspect of the present invention, the central processing unit performs embedding repetition of the local pattern indicating each information included in the additional information based on the amount of additional information that can be embedded, the relative importance, and the information amount of the additional information. determining the number, the amount of buried iterations of the information, is preferably Rukoto be determined based on the relative importance of each information.

Another Ichitai like of the present invention, the inputted original document image, the background pattern indicating the additional information is synthesized, an image processing method in an image processing apparatus capable of generating the additional information embedding document image A possible area detection step for detecting an area that can be embedded in a tint block pattern, and an amount of additional information that can be embedded based on the area of the information embeddable area detected in the possible area detection step. A step of deriving a certain amount of embeddable additional information, an easy region detection step for detecting a region that is included in the original document image and is easy to embed a copy-forgery-inhibited pattern, and an information embedding easy region detected in the easy region detection step The step of deriving the amount of easily embeddable additional information based on the area and the relative weight between the information included in the additional information is derived. The order of determining the degree of priority, and the priority for determining the priority in which each piece of information included in the additional information is embedded as a tint block pattern based on the amount of additional information that can be embedded, the amount of additional information that can be easily embedded, and the relative importance A step of determining, and preferentially embedding the high priority information determined in the order determination step as a tint block pattern in a region where the original document image is easily embedded, and generating an additional information embedded document image, The embeddable area is an area in which the success of reading additional information related to the background pattern embedded in the area is a predetermined first probability or more, and the easily embedded area is related to the background pattern embedded in the area. This is an image processing method in which the additional information read success probability is an area of a second probability or higher that is higher than the first probability . Further, another aspect of the present invention can be executed by a computer of an image processing apparatus capable of synthesizing a tint block pattern indicating additional information with an input original document image and generating an additional information embedded document image. An image processing program, based on a possible area detection step for detecting an area that can be embedded in a copy-forgery-inhibited pattern pattern in a computer image, and an area of an information embedding area detected in the possible area detection step. In the step of deriving the amount of additional information that can be embedded and the amount of additional information that can be embedded, an easy region detecting step that detects an area that is included in the original document image and that is easy to embed a tint block pattern, and an easy region detecting step The easy-to-embedding additional information amount, which is the amount of additional information that can be easily embedded, is derived based on the detected area of the easy-to-embed information area. The additional information based on the step of determining the relative importance of the information included in the additional information, the amount of additional information that can be embedded, the amount of easily embedded additional information, and the relative importance. A priority determining step for determining the priority in which each included information is embedded as a tint block pattern, and information having a high priority determined in the rank determining step is preferentially embedded as a tint block pattern in an easily embedding area of the original document image, Generating an additional information embedded original image, and the area that can be embedded is an area in which a read success probability of additional information relating to a tint block pattern embedded in the area is a predetermined first probability or more, The easily embedded area has a second probability that the success in reading additional information related to the tint block pattern embedded in the area is higher than the first probability. It is a more regions, an image processing program.

  The image processing apparatus according to the present invention discriminates the importance of additional information embedded in a document image as a background pattern, and improves the reading accuracy of the background pattern indicating the additional information with high importance. The image processing apparatus according to the present invention can embed a tint block pattern indicating additional information that requires particularly high reading accuracy in a document having various document images while maintaining high reading accuracy.

  An image processing apparatus according to the present invention is an image processing apparatus capable of embedding additional information as a tint block pattern in a document. In the image processing apparatus according to the present invention, the importance of the additional information to be embedded is distinguished, and the tint block pattern embedding process is executed based on the importance.

  As described above, the amount of information that can be read with high accuracy generally varies from document to document, and the amount of information may be extremely small. However, according to the image processing apparatus of the present invention, embedding of a tint block pattern indicating additional information having high importance is performed with priority over other additional information, and the number of times of embedding is set to other additional information. More than the number of embedding repetitions of the tint block pattern. By doing so, the reading accuracy of the additional information with high importance is improved.

  The image processing apparatus according to the present invention is, for example, a multifunction machine having a copy function.

  The additional information according to the present invention is, for example, security information automatically generated by the image processing apparatus. In this case, the security information is embedded in the document as a background pattern. Further, the additional information may be arbitrary information arbitrarily added by the user.

  The original according to the present invention may be a paper original optically read by the image processing apparatus or image data input electronically.

  Hereinafter, in this specification, a document before a copy-forgery-inhibited pattern indicating additional information is embedded is referred to as an “initial document”. An image included in the original document is referred to as an “original document image”. The original after the copy-forgery-inhibited pattern is embedded is referred to as an “embedded original”, and the image of the embedded original is referred to as an “embedded original image”.

  The “additional information embeddable area” in the original document image refers to an area in which the additional information reading success probability is equal to or higher than a predetermined first probability when a copy-forgery-inhibited pattern is embedded in the area. The “additional information embedding area” in the original document image refers to an area having a predetermined second probability higher than the first probability, when the copy-forgery-inhibited pattern pattern is embedded in the area. . Therefore, the additional information embeddable area is a predetermined area equal to or less than the entire area of the original document, and is an area determined based on the original document image state. The additional information embedment easy area includes a case where the additional information embeddable area completely coincides with the additional information embeddable area, and is an area included in the additional information embeddable area, which is initially determined in the state of the original image. .

  FIG. 1 is a block diagram showing an outline of the configuration of an image processing apparatus (multifunction machine) 1 according to the present invention. The multifunction machine 1 includes a central processing unit 2 that controls the multifunction machine 1, and the central processing unit 2 executes a program stored in a storage device (not shown) to control the operation of the multifunction machine 1.

  The central processing unit 2 is connected to the first scanner image processing circuit 3, the second scanner image processing circuit 4, the security background pattern detection circuit 5, the controller circuit 6, the printer image processing circuit 7, and the input / output unit 8. Each circuit can be controlled.

  The first scanner image processing circuit 3 inputs RGB image data, performs correction processing such as shading correction, inter-line correction, and chromatic aberration correction on the RGB image data, and the corrected RGB image data is converted into the second scanner image processing circuit. 4 and the security background pattern detection circuit 5. The RGB image data may be document image data optically read by the multifunction device 1. Also, it may be original image data input electronically.

  The second scanner image processing circuit 4 receives the RGB image data, converts the resolution of the image data, removes the background color included in the image data, converts it to YMCK image data, and converts the edge portion of the character included in the document. Correction, error diffusion processing such as gradation expression included in the document, and the like are performed, and YMCK image data is output to the controller circuit 6.

  The security copy-forgery-inhibited pattern detection circuit 5 receives RGB image data and detects a copy-forgery-inhibited pattern pattern included in the image data. The security copy-forgery-inhibited pattern detection circuit 5 converts the resolution of the image data, performs predetermined preprocessing, detects a specific pattern (detects a copy-forgery-inhibited pattern), decodes the copy-forgery-inhibited pattern, and acquires additional information.

  The controller circuit 6 inputs YMCK image data, compresses / decompresses the image data, and outputs the YMCK image data to the printer image processing circuit 7.

  The printer image processing circuit 7 inputs YMCK image data, performs predetermined image correction on the image data as necessary, outputs the image data to a printer unit of the multifunction device 1 (not shown), and prints the image data. Execute. The printer image processing circuit 7 includes an image composition unit 71, and the image composition unit 71 synthesizes a tint block pattern with respect to YMCK image data. That is, the image composition unit 71 inputs YMCK image data (original document image data), and outputs YMCK image data (embedded document image data) in which a tint block pattern is embedded.

  The input / output unit 8 is a so-called user interface. The input / output unit 8 includes an output unit (display unit) 81 that presents information to the operator, and an input unit 83 that allows the operator to input information to the multifunction device 1. A specific form of the input / output unit 8 may be a known configuration.

  FIG. 2 is a block diagram showing details of the image composition unit 71.

  The image composition unit 71 receives original document image data and outputs embedded document image data.

  The original document image data input to the image composition unit 71 is sent to the information embedding area detection unit 721a, the information embedding easy area detection unit 723a, and the background pattern composition unit 725.

  The information embeddable area detection unit 721a receives the original document image data and analyzes the original document image data. The information embeddable area detection unit 721a detects an area that is initially included in the original image and has an additional information read success probability equal to or higher than a predetermined first probability when a copy-forgery-inhibited pattern is embedded in the area. Information on the detected area is sent to the embeddable information amount calculation unit 721b. The embeddable information amount calculation unit 721b derives an information amount (embeddable information amount) that can be embedded as a tint block pattern based on the received information. The embeddable information amount is sent to the central processing unit 2. Here, the embeddable information amount is proportional to the area of the detected information embeddable region. However, a predetermined relationship other than the proportional relationship may be assumed. The embeddable information amount may be derived from the area of the information embeddable region.

  The information embedding easy area detection unit 723a receives the original document image data and analyzes the original document image data. The information embedding easy area detection unit 723a is an area initially included in the original image, and the additional information reading success probability when the copy-forgery-inhibited pattern is embedded in the area is equal to or higher than a predetermined second probability higher than the first probability. Detect the area. Information on the detected area is sent to the easy-to-embed information amount calculation unit 723b. The easy embedding information amount calculation unit 723b derives an easily embeddable information amount (easy embedding information amount) as a tint block pattern based on the received information. The amount of easy embedding information is also sent to the central processing unit 2. Here, the amount of easy embedding information is assumed to be proportional to the area of the detected information easy embedding region. However, a predetermined relationship other than the proportional relationship may be assumed. It is only necessary that the easy embedding information amount can be derived from the area of the easy information embedding region.

  The information embedding area and the information embedding easy area are determined based on the read success probability determined depending on the characteristics of the original document image in the area. For example, if the area is a white background color, the background pattern embedded in the area is read with extremely high accuracy. Therefore, the read success probability value for the area is extremely high. Such a region can be said to be a region that can be easily embedded. Conversely, if the area is a solid solid image, it is extremely difficult to read out the tint block pattern embedded therein. Therefore, the read success probability value for that region is set to an extremely low value. Such a region can be said to be a region that cannot be embedded. An area in which halftone dots are arranged and an area in which characters are densely described can be embedded, but cannot be said to be an area with a high read success probability. In general, an area that contains a lot of light-colored parts and does not contain a steep color (or light and shade) change has a high read success probability value, and conversely, contains a lot of dark-colored parts and steep colors. In a region including a change in (or shading), the read success probability value is low.

  The central processing unit 2 instructs the tint block pattern generation unit 727 to generate a tint block pattern based on the embeddable information amount, the easy embedding information amount, and the determination result of the information importance level determination unit 21 described later. The generated tint block pattern is embedded in the original document image data by the tint block synthesizing unit 725 under the instruction of the central processing unit 2, and embedded document image data is generated and output.

  FIG. 3 shows an example of a background pattern 91 generated by the background pattern generation unit 727. Thus, the background pattern 91 is a pattern indicating predetermined information in accordance with the density of the minute dots and the arrangement relationship thereof. In the copy-forgery-inhibited pattern 91, the amount of information per area is constant at a predetermined number of bits. The tint block pattern 91 can include the following additional information.

  First, security information is automatically generated by the multifunction device 1. This security information can include information on security management related to copying of the document, such as additional information indicating the copy-forgery-inhibited pattern pattern included in the original document image read by the security copy-forgery-inhibited circuit 5 and user information of the operator. is there.

  The second is arbitrary information indicating arbitrary information input to the multifunction machine 1 by the operator. This arbitrary information can include information that the operator inputs to supplement the security information and information that the operator inputs to improve the convenience of use by the operator.

  FIG. 4 is a schematic diagram showing the configuration of the input / output unit 8 for inputting arbitrary information. The input / output unit 8 includes an output unit (display unit) 81 and an input unit 83. The output unit 81 is, for example, a liquid crystal display. The input unit 83 includes hard keys and soft keys that the display unit 81 has. The output unit 81 is displayed to prompt the operator to input arbitrary information, and the operator can input arbitrary information to the multifunction device 1 using hard keys and soft keys.

  Both the security information and the arbitrary information are embedded in the original document image data as a tint block pattern. At this time, the central processing unit 2 determines the configuration of the tint block pattern based on the number of bits of security information and the number of bits of arbitrary information, the amount of embeddable information and the amount of easily embeddable information, and the information importance.

  The information importance level determination unit 21 of the central processing unit 2 determines the relative importance levels of the security information and the arbitrary information according to a predetermined rule. For example, the information importance level determination unit 21 determines that the security information has a high relative importance level in comparison with arbitrary information. When the amount of easy embedding information and / or the amount of embeddable information is insufficient compared to the number of bits of security information and arbitrary information, the central processing unit 2 sends the background pattern pattern generation unit 727 and the background pattern synthesis unit 725 to Then, an instruction is sent so that the security information is preferentially embedded in the easy embedding area. In addition, an instruction is sent so that the number of times of embedding the background pattern indicating security information is larger than that of arbitrary information. In addition, the central processing unit 2 sends an instruction so that the arbitrary information is embedded in an area excluding the area where the background pattern indicating security information is embedded.

  Note that when security information includes a plurality of pieces of information, there may be a difference in relative importance between the pieces of information. In that case, information with particularly high relative importance is given priority and more embedding is performed. It is embedded in the embeddable region and the embeddable region by the number of repetitions. In addition, relative information may be determined by the operator for arbitrary information input by the operator, and in this case as well, arbitrary information with high relative importance is given priority as with security information. Then, it is embedded in the embeddable region and the embeddable region by more embedment repetitions.

  FIG. 5 is a flowchart of processing related to embedding a tint block pattern of the multifunction device 1.

  In step S101, the information embeddable area detection unit 721a detects an information embeddable area in the original document image data.

  In step S103, the embeddable information amount calculation unit 721b derives an information amount (embeddable information amount) that can be embedded as a tint block pattern in the information embeddable region.

  In step S105, the information embedding easy area detection unit 723a detects the information embedding easy area in the original document image data.

  In step S107, the easy embedding information amount calculation unit 723b derives an information amount (easy embedding information amount) that can be embedded as a tint block pattern in the information embedding easy region.

  In step S <b> 109, the central processing unit 2 determines whether or not the operator has input arbitrary information using the input unit 83. If the input arbitrary information exists (YES in step S109), the process proceeds to step S111. If the input arbitrary information does not exist (NO in step S109), the process proceeds to step S115.

  In step S111, the central processing unit 2 determines (extracts) information (embedding information) (security information and arbitrary information) to be embedded as a tint block pattern in the original document.

  In step S113, the information importance level determination unit 21 of the central processing unit 2 determines the relative importance level between the information items of the information group (security information and information group consisting of arbitrary information) included in the embedded information. (judge.

  In step S115, the central processing unit 2 compares the embedding information with the amount of embeddable information, and can embed all the information groups included in the embedding information as a background pattern in the original document? It is determined whether or not. If it is determined that it is possible (YES in step S115), the process proceeds to step S117. If it is determined that it is impossible (NO in step S115), the process proceeds to step S121.

  In step S117, the central processing unit 2 determines the number of repetitive embeddings for each of the information groups included in the embedding information according to the relative importance of each.

  In step S119, the central processing unit 2 determines an embedding position in the document according to the relative importance of each information group included in the embedding information. At this time, the information may be determined so as to be embedded in the easy embedding region based on information having relatively high importance.

  On the other hand, in step S121, the central processing unit 2 warns the operator through the output unit 81 that all information may not be embedded.

  In step S123, the central processing unit 2 determines the embedding order (priority embedding order) based on the relative importance of each information group included in the embedding information.

  In step S125, the central processing unit 2 instructs the background pattern generation unit 727 to generate a background pattern. Upon receiving the instruction, the background pattern generation unit 727 generates a background pattern based on the instruction from the central processing unit 2.

  In step S127, the central processing unit 2 instructs the background pattern composition unit 725 to embed (synthesize) the background pattern in the original document image. Upon receiving the instruction, the background pattern composition unit 725 embeds the background pattern generated by the background pattern pattern generation unit 727 in a predetermined area based on an instruction from the central processing unit 2 and outputs embedded document image data.

  In the image processing apparatus according to the present invention, an area in which a tint block pattern in the original document can be embedded and an easy area are detected, compared with the amount of information to be embedded, and embedded. By determining the importance level of information, a tint block pattern indicating information having a relatively high importance level is preferentially embedded in an area with high read accuracy with a larger number of iterations. By doing so, the present invention has an effect of increasing the detection accuracy of a tint block pattern indicating highly important information.

  As will be described again, the embeddable area is an area in the document where the embedded tint block pattern can be detected (read out), and the detection success probability is equal to or higher than a predetermined first probability value. Refers to an area. The region that is easily embedded refers to a region that has a detection success probability of the embedded tint block pattern that is equal to or higher than a predetermined second probability value that is higher than a predetermined first probability value.

  An image processing apparatus according to the present invention is an image processing apparatus that can embed security information as a tint block pattern in an image of an original document, and is useful in the field of image processing apparatuses such as multifunction peripherals.

1 is a block diagram of a multifunction machine according to an embodiment of the present invention. The block diagram of the image composition part by the embodiment concerning the present invention Example of tint block pattern Configuration example of input / output unit 8 for inputting arbitrary information Flowchart of processing of a multifunction machine according to an embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... MFP 2 ... Central processing unit 3 ... 1st scanner image processing circuit 4 ... 2nd scanner image processing circuit 5 ... Security copy-forgery-inhibited pattern detection circuit 6 ... Controller circuit 7 ...・ Printer image processing circuit 8... Input / output unit 21... Information importance degree determination unit 71... Image composition unit 81.
83... Input unit 721a... Information embeddable area detection unit 721b... Embeddable information amount calculation unit 723a... Information embedding easy region detection unit 723b. 725 ... Background pattern composition unit 727 ... Background pattern generation unit

Claims (5)

An image processing apparatus that synthesizes a copy-forgery-inhibited pattern pattern indicating additional information with an input original document image and generates an additional information embedded document image,
An information embeddable area detection unit that detects an area that is included in the original document image and in which the tint block pattern can be embedded;
An embeddable information amount calculation unit for deriving an embeddable additional information amount that is an amount of additional information that can be embedded based on the detected area of the information embeddable region;
An information embedding easy area detection unit that detects an area that is included in the original document image and is easy to embed the tint block pattern;
An easily embeddable information amount calculation unit for deriving an easily embeddable additional information amount which is an amount of easily embeddable additional information based on the detected area of the information easily embedded region;
An information importance determination unit for determining the relative importance between the information included in the additional information;
A tint block composition unit for embedding the tint block pattern in the original document image;
A central processing unit for controlling the own device ,
The embeddable area is an area in which the success rate of reading additional information related to the tint block pattern embedded in the area is equal to or higher than a predetermined first probability,
The easily embeddable region is a region having a second or higher probability that the success rate of reading additional information related to the tint block pattern embedded in the region is higher than the first probability,
The central processing unit determines a priority in which each piece of information included in the additional information is embedded as a tint block pattern based on the embeddable additional information amount , the embeddable additional information amount, and the relative importance. and, the background pattern composition unit embeds the higher the priority the information as background pattern preferentially to the buried readily area, the image processing apparatus for generating the additional information embedding document image. When the amount of embeddable additional information is less than the amount of information of the additional information,
The image processing apparatus according to claim 1, wherein the copy-forgery-inhibited pattern combining unit preferentially embeds the information having a high relative importance in the original document image as a copy-forgery-inhibited pattern. The central processing unit calculates the number of repetitions of embedding the local pattern indicating each information included in the additional information based on the amount of additional information that can be embedded, the relative importance, and the information amount of the additional information. determined, the image processing apparatus according the the amount of the embedded iterations of each information, to claim 1 that determine on the basis of the relative importance of each information. An image processing method in an image processing apparatus capable of synthesizing a copy-forgery-inhibited pattern pattern indicating additional information with an input original document image and generating an additional information embedded document image,
A possible region detection step for detecting a region included in the original document image and capable of embedding the tint block pattern;
Deriving an embeddable additional information amount that is an amount of additional information that can be embedded based on the area of the information embeddable region detected in the possible region detection step;
An easy area detection step for detecting an area included in the original document image and easily embedded with the tint block pattern;
Deriving an easy embedding additional information amount that is an amount of additional information that is easy to embed based on the area of the information embedding easy region detected in the easy region detecting step;
Determining the relative importance of information included in the additional information; and
An order determination step for determining a priority in which each piece of information included in the additional information is embedded as a tint block pattern based on the amount of additional information that can be embedded, the amount of additional information that can be easily embedded, and the relative importance; ,
Preferentially embedding the information having a high priority determined in the order determination step as a tint block pattern in the easy embedding area of the original document image, and generating the additional information embedded document image. ,
The embeddable area is an area in which the success rate of reading additional information related to the tint block pattern embedded in the area is equal to or higher than a predetermined first probability,
The image processing method, wherein the easily embeddable region is a region having a second or higher probability of successfully reading additional information related to a tint block pattern embedded in the region being higher than the first probability. An image processing program that can be executed by a computer of an image processing apparatus capable of synthesizing a tint block pattern indicating additional information with an input original document image and generating an additional information embedded document image.
A possible region detection step for detecting a region included in the original document image and capable of embedding the tint block pattern;
Deriving an embeddable additional information amount that is an amount of additional information that can be embedded based on the area of the information embeddable region detected in the possible region detection step;
An easy area detection step for detecting an area included in the original document image and easily embedded with the tint block pattern;
Deriving an easy embedding additional information amount that is an amount of additional information that is easy to embed based on the area of the information embedding easy region detected in the easy region detecting step;
Determining the relative importance of information included in the additional information; and
An order determination step for determining a priority in which each piece of information included in the additional information is embedded as a tint block pattern based on the amount of additional information that can be embedded, the amount of additional information that can be easily embedded, and the relative importance; ,
Performing the step of preferentially embedding the high-priority information determined in the order determination step as a tint block pattern in the easy embedding area of the original document image and generating the additional information embedded document image. ,
The embeddable area is an area in which the success rate of reading additional information related to the tint block pattern embedded in the area is equal to or higher than a predetermined first probability,
The image processing program, wherein the easily embedded region is a region having a second or higher probability that the success in reading additional information related to the tint block pattern embedded in the region is higher than the first probability.

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