JP2008026874A - Image forming apparatus and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict and inhibit a copying operation even when an original with copy restriction information added is copied by a copying machine with a copy restriction function or a copying machine without the copy restriction function. <P>SOLUTION: The copy restriction information is buried in an output object while presetting the number of copying allowable times when the document originator outputs the output object, and a background pattern is added to the output object. In copying the original, if the copying times are within the number of copying allowable times, the background pattern is removed, and the copying is allowed. When being copied by the machine without the function, information that the object is a copy-inhibited object is given with the background pattern effect. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus capable of restricting copying of a document.

  Conventionally, in an office or the like, a document printed by a printer is copied by a copying machine. However, this action can be a major security issue. For example, if a confidential document distributed at a meeting or the like is copied, there is a high possibility that it will be transferred to a third party.

  In order to prevent such a situation, as shown in FIG. 18, a warning word suggesting prohibition of copying has been added to the output. In addition, as shown in FIG. 19, a technique has been widely used in which an invisible mark is recorded on a copy object using special paper or ink, and the mark is visualized by copying it.

  However, even a document with a copy prohibition warning as shown in FIG. 18 can be copied in the end if the person who performs the copy ignores the warning and copies it. Therefore, there is a problem that it has only an effect of suppressing copying.

  Further, when special paper or ink as shown in FIG. 19 is used, it is necessary to provide a dedicated consumable such as special paper or ink, or a printing device for using them. there were.

  In recent years, as shown in FIG. 20, a background pattern or a watermark is added to a part or the entire surface of an output product in advance. When an original document with a copy-forgery-inhibited pattern or a watermark is copied, the copy is visualized as a copy. There has also been proposed an apparatus for applying a mechanism for painting the entire surface.

  In addition, there is a demand for a copy restriction method in which copying of a document is not completely prohibited but copying of a limited number of times is permitted.

  In order to solve such a problem, a copy prohibition or grandchild copy prohibition marking is added and output as image information in advance. If the copy prohibition marking is detected when the original is read, the read image is deleted. Further, when a grandchild copy prohibition marking is detected when a document is read, a proposal has been made to remove the grandchild copy prohibition marking and newly add a copy prohibition marking to a copy image (for example, a patent). Reference 1).

Patent Document 1 is an effective invention when it is desired to permit copying up to a certain generation as shown in FIG. 17 and prohibit copying thereafter.
JP 2000-184178 A (page 16, FIG. 8)

  However, the above configuration is effective if the environment such as an office used is an environment in which only a copier having the above configuration is installed. However, in a usage environment in which copiers that do not support the above-described copy restriction function are mixed, there is a problem that a security effect cannot be obtained because the function for restricting copying does not work.

  In other words, information leakage is effective in a usage environment in which only a copying machine having a copy restriction function exists, but the effect is halved in a usage environment in which copying machines having no copying restriction function coexist.

  Accordingly, the present invention provides a copy restriction in a use environment in which only a copy machine having a copy restriction function exists while maintaining a copy suppression effect in a use environment in which a copy machine having no copy restriction function and a certain copy machine are mixed. The purpose is to be able to.

  In order to solve the above-described problems, a control method for an image forming apparatus according to the present invention includes a latent image portion and a background portion, and restricts the copy-forgery-inhibited pattern and the number of copies that the latent image portion appears in the copy image when copied. A reading step for reading a document to which copy restriction information is added; a decoding step for decoding the copy restriction information given to the document image read in the reading step; and the copy-forgery-inhibited pattern from the document read in the reading step. A removing step for removing, an updating step for updating the copy restriction information decoded in the decoding step, and a copy restriction information updated in the updating step together with an image from which the background pattern has been removed from the original image in the removing step And a forming step.

  The image forming apparatus control method of the present invention includes a first setting step for setting copy restriction information for limiting the number of copies for image data to be printed, a latent image portion, and a background portion. A second setting step of setting to add to the image data a copy-forgery-inhibited pattern in which the latent image portion appears in the copied image when copied; and the copy-limitation information and the copy-forgery-inhibited pattern image data representing the copy-forgery-inhibited pattern in the image data A combining step for combining, and an image forming step for forming an image on a sheet based on the image data obtained by combining the copy restriction information and the copy-forgery-inhibited pattern image data.

  According to the present invention, information indicating the permitted number of times of copying is previously added to the output material by the document creator, and a function having a copy inhibiting effect such as a background pattern is also added, so that the output material is added when copying the output material. It is possible to restrict copying by determining whether copying is possible according to the permitted number of times of copying. Furthermore, even when a copy machine of another manufacturer or an old-style copy machine that does not have this function is used, copy prohibition can be realized by a copy-forgery-inhibited pattern or watermark having a copy suppression effect. Therefore, it is possible to provide flexible copy protection not only in a limited use environment but also in a variety of use environments, thereby preventing the spread of confidential information.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of the image forming apparatus according to the first embodiment. In the first embodiment, the image forming apparatus will be described as a digital multi-function peripheral having a plurality of functions such as a copying machine, a printer, and a FAX.

  A scanner unit 111 reads an image of a document, and a printer unit 112 forms an image on recording paper. Reference numeral 113 denotes a document table on which a document is placed, and 109 denotes an optical system for reading the document. The optical system 109 includes a document irradiation lamp, a short focus lens array, and a CCD (CIS) sensor as a reading element. By scanning the document G while irradiating the document G with the document irradiation lamp, The document surface reflected light is imaged by the short focus lens array and is incident on the CCD sensor.

  The CCD sensor includes a CCD light receiving unit (not shown), a transfer unit (not shown), and an output unit (not shown). The optical signal is converted into a charge signal in the CCD light receiving unit, and sequentially transferred to the output unit in synchronization with the clock pulse in the transfer unit. The output unit converts the charge signal into a voltage signal, and amplifies and lowers the impedance for output. The obtained analog signal is subjected to known image processing, converted into a digital signal, and sent to the printer unit 112.

  When a start key (not shown) of the operation unit is pressed, the photosensitive drum 104 is charged by the charger 108 so as to have a predetermined potential. In the laser exposure unit 110 of the printer unit 112, the solid-state laser element emits light based on the digital signal, and the light scans on the photosensitive drum 104 by a rotating polygon mirror that rotates at high speed. As a result, an electrostatic latent image corresponding to the original image is formed on the photosensitive drum 104. Next, the electrostatic latent image is developed by the developing unit 103 to form a toner image on the photosensitive drum 104. The developing device 103 contains a so-called two-component developer having toner particles and carrier particles. In this way, the toner image formed on the photosensitive drum 104 is transferred onto the transfer material 106 by the transfer device 105. Thereafter, the transfer material is separated from the photosensitive drum 104, conveyed to the fixing device 107, thermally fixed, and discharged.

  FIG. 2 is a block diagram showing a schematic configuration of the image forming apparatus.

  201 is a control unit that controls the entire image forming apparatus, 202 is an operation unit that performs various settings and displays, and 203 is an interface unit that communicates with devices connected to a network. A printer driver 211 performs processing for printing on a PC connected to the network. Reference numeral 204 denotes a decryption unit that decrypts cryptographic markings added to a document, which will be described later. Reference numeral 205 denotes an image memory that stores an image received by the interface unit 203 and an image read by the scanner unit 111. A filter unit 206 performs various types of image processing on the image data, and performs a background pattern removal process described later. A copy-forgery-inhibited pattern generation unit 207 generates a copy-forgery-inhibited pattern image to be added to a print image, and 208 is a copy-forgery-inhibited pattern synthesis unit that combines the generated copy-forgery-inhibited pattern with a print target image. Reference numeral 209 denotes an encryption unit that encrypts later-described copy restriction information into an encryption marking such as a barcode. Reference numeral 210 denotes an encryption composition unit that combines the encryption marking with an image to be printed.

  Next, a method for adding a general background pattern to an image formed on a transfer material will be described.

  Document data created on the PC is stored in the image memory 205 via the printer driver 211. When the user designates to add a background pattern, the printer driver 211 transmits the background pattern addition information to the background pattern generation unit 207. Next, the background pattern composition unit 208 adds the generated background pattern image to the image read from the image memory 205, and then transmits the image data to the printer unit 112.

  Next, a flow when copying a document image will be described.

  The document image read by the scanner unit 111 is stored in the image memory 205, subjected to known image processing such as edge enhancement and masking by the filter unit 206, and then transferred to the printer unit 112.

  The structure of the tint block will be described with reference to FIG. The copy-forgery-inhibited pattern used here uses a collection of background portions (small dots) and latent image portions (large dots) formed by pixel arrays of different sizes, using the limits of image reproduction capability of the image forming apparatus. It is formed. In general, the background portion is a portion where pixels disappear due to the limit of reproduction capability of the scanner portion or printer portion after copying, and the latent image portion is a portion where pixels are reproduced without disappearing after copying. That is, when the copy-forgery-inhibited pattern is copied, a predetermined pattern (latent image portion) is emphasized on the copied image. As this pattern, an image representing a copy prohibition warning phrase or a phrase representing a copy is often used.

  The pixel arrangement of the background portion and latent image portion of the background pattern as described above is determined according to the image reproduction capability of the scanner portion or printer portion.

  In the present embodiment, the background pattern is different from the image processing pattern for halftone expression (such as dithering) of the image before the background pattern is added. That is, the background portion and the latent image portion are formed with a pattern dedicated to the background pattern.

  Next, the tint block print will be described. FIG. 4 is a flowchart at the time of copy-forgery-inhibited pattern printing.

  A document created by a PC or the like is converted into print data via the printer driver 211 and stored in the image memory 205.

  Here, FIG. 5 shows an example of a printer driver screen for setting various output conditions from the PC when the user issues a print instruction. When the output material is a confidential document, the user can set on the printer driver the number n of copying restrictions, that is, the number of times that copying is permitted for the output material. Further, the user can make a setting for adding a background pattern to the output. In the present embodiment, when copy restrictions are set, a setting for automatically adding a background pattern is made. In the example of FIG. 5, the number of times that copying is permitted is two.

  When the printer driver is set as described above (step S1001), the printer driver 211 transmits the copy restriction presence / absence set by the user and the number of times information to the encryption unit 209, while the copy-forgery-inhibited pattern additional information is sent to the copy-forgery-inhibited pattern. The data is transmitted to the generation unit 207.

  Here, details of the encryption unit 209 will be described. The encryption unit 209 encrypts and marks (encryption marking) the presence / absence of copy restriction and the allowable number of copies set from the printer driver (step S1002). The encryption marking here may be a one-dimensional barcode widely used for general purposes, or a two-dimensional barcode that has become popular in recent years. In addition, the information to be encrypted is not limited to the presence or absence of copying restrictions and the permitted number of copies, but also information such as creator information such as the name and affiliation of the creator of the output product, the machine number of the printer to be output, and the output date and time (print date and time) It can also be included. As described above, it is considered that the more information to be encrypted is, the better the protection function against secret leakage.

  6 and 7 show the cryptographic marking used in this embodiment. In FIG. 6, a one-dimensional bar code is used. This bar code includes information of the output date and time and the permitted number of times of copying (in this case, twice). Further, in FIG. 7, a two-dimensional bar code is used. This bar code includes information on the presence / absence of copying restrictions and the number of permitted copying times, creator information, output date and time, and output machine number. Here, the information includes that the permitted number of times of copying is two, and output is performed by a monochrome printer (BW) on the north side (N) of the office 2F. As can be seen, it is possible to include a lot of information in addition to the permitted number of times of copying depending on the type of encryption marking.

  The encryption marking including the information regarding the copy restriction encrypted by the encryption unit 209 is combined with the image data read from the image memory 205 by the encryption combining unit 210 (step S1003). It is desirable to add the encryption markings to, for example, the top, bottom, left and right margin areas of the output paper (recording medium). Furthermore, if a plurality of encryption markings are periodically arranged, the detection accuracy of the encryption markings can be increased. In addition, in order to prevent deterioration of the quality of the original image due to the addition of the encryption marking, it is necessary to consider the setting of a place or color that is difficult to detect to the human eye as much as possible. For example, if the output is to be performed by a full-color printer, it is desirable to form the encryption marking with a color material having the highest brightness such as yellow toner. Further, transparent toner or transparent ink may be used. Furthermore, a cryptographic marking may be added to the image using a digital watermark. By doing so, it is possible to prevent the image quality from being deteriorated and to reduce the possibility that a malicious operator notices the presence of the encryption marking.

  Next, the background pattern generated by the background pattern generation unit 207 is added to the image output from the cipher composition unit 210 by the background pattern composition unit 208 (step S1004). Thereafter, the image with the copy-forgery-inhibited pattern added is transmitted to the printer unit 112 (image forming unit) and recorded on the sheet (step S1005).

  Note that the processing executed by the printer driver described above is configured by a program executable by a computer. This program is installed in the computer from various storage media such as a CD-ROM. Alternatively, it is downloaded via the Internet and then installed on the computer.

  Further, the above-described encryption marking and background pattern may be added not only to a document created by a PC but also to a document read by the scanner unit 111. In this case, before reading the document, a mode for adding copy restriction information is set from the operation unit, and the same setting as the setting on the printer driver screen described above is performed.

  Next, a flow of copying a document with copy restriction information created with the above configuration will be described.

  A document image read by the scanner unit 111 serving as an image reading unit is stored in the image memory 205 and transferred to the decryption unit 204. The decryption unit 204 detects whether there is an encrypted marking in the read document image, and if the encryption marking is detected, reads the copy restriction information included in the encryption marking and outputs it to the control unit 201 To do. Next, the control unit 201 changes the digital filter used in the filter unit 206 according to the read information on the permitted number of copies, and updates the permitted number of copies. After that, the image data is digitally filtered by the filter unit 206 and then combined with the encryption marking by the cipher synthesizing unit 210. The background pattern is added by the background pattern synthesizing unit 208 and transmitted to the printer unit 112. Then, the image with the encryption marking and the background pattern added is recorded on the paper.

  Next, details of the copy operation will be described with reference to the flowchart of FIG. The processing of this flowchart is executed by the control unit 201 in FIG.

  When a user copies a document on which an encryption marking obtained by encrypting information on the permitted number of copies is printed, the control unit 201 causes the scanner unit 111 to read the document to be copied in step S1401. In step S1402, the control unit 201 determines whether or not cryptographic marking is detected. When the encryption marking is not detected, copying is performed as a normal document. If the encryption marking is detected, the control unit 201 causes the decryption unit 204 to decrypt the encryption marking printed on the document in step S1403, and obtains the allowable copy number n included in the decrypted information. In step S <b> 1404, the control unit 201 determines whether the allowable number of copying n is greater than zero. If n> 0, it is determined that the copying operation to be performed is within the limit of the allowable number of copying set for the document, and in step S1405, the filter unit 206 is set to perform processing for removing the background pattern. .

  Here, the digital filter will be described. A digital filter generally has a function of smoothing or sharpening an image by removing or extracting a specific frequency component from the image signal. In the normal tint block function, a filter that eliminates the background portion by applying a digital filter that increases the difference between the amplification factors of the background portion and the latent image portion of the tint block pattern, leaving only the latent image portion. It has a configuration. In the present embodiment, as described above, a background pattern dedicated pattern having a predetermined coefficient is used for the background portion and the latent image portion of the background pattern image printed on the document. Using this feature, when the allowable number of times of copying is n> 0, the digital filter is configured to set the frequency and amplification factor for smoothing both the background portion and the latent image portion. Thus, the tint block pattern in which the difference between the background portion and the latent image portion disappears becomes inconspicuous by performing processing such as density value adjustment and background removal that are image adjustment functions in the subsequent stage. That is, the background pattern is erased. Therefore, when copying is permitted, the copy-forgery-inhibited pattern is not emphasized.

  Thereafter, in step S1406, the control unit 201 subtracts 1 from the allowable copy number n, and causes the encryption unit 209 to re-encrypt the data of the allowable copy number subtracted in step S1407. In step S1408, the control unit 201 causes the encryption composition unit 204 to perform composition of the encryption marking and the image from which the background pattern has been removed. In step S 1409, the control unit 201 causes the background pattern composition unit 208 to combine the background pattern newly generated by the background pattern generation unit 207 and the image output from the cipher composition unit 210. The combined image is transmitted to the printer unit 112.

  If the allowable copy number read from the encryption marking in step S1404 is n = 0, the control unit 201 determines that copying is not permitted any more, and prohibits copying in step S1411. (Do not copy) and warn the operator that copying is prohibited. FIG. 9 shows the warning screen.

  If the permitted number of times of copying is n = 0, copying may be executed instead of prohibiting copying. That is, if No in step S1404, the process proceeds to step S1409. In this case, a copy-forgery-inhibited pattern will appear in the copied image, indicating that the copy-prohibited document has been copied.

  Next, a description will be given of a case where a document with encryption marking added is copied by a copy machine that does not have the above-described copy restriction function, for example, a copy machine with a different manufacturer or an old type copy machine. Since such a copying machine does not have a configuration for detecting the encryption marking, even if the copy allowable number included in the encryption marking is n> 0, the copy is performed with a normal function. Therefore, the latent image portion of the copy-forgery-inhibited pattern pattern added to the original is visualized, and it is known that the copy is a copy of the copy-prohibited original, and the operator is warned that the copy is restricted. it can.

  As shown above, when a document created on a PC or the like is output in advance, the copy restriction and the number of times that copying is allowed are set, the information is added to the output, and the copy suppression effect such as copy-forgery-inhibited pattern and watermark is also provided. A copy is made. When copying the copy, it is possible to restrict the copy by determining whether or not the copy is permitted according to the added allowable copy number. Even when a copier that does not have a copy restriction function is used, copy suppression can be realized by a copy-forgery-inhibited pattern or watermark having a copy suppression effect. Thus, it is possible to provide flexible copy protection not only in a limited use environment but also in a variety of use environments, thereby preventing the spread of confidential information.

(Second Embodiment)
In the first embodiment described above, the copy limit and the allowable number of times of copying set at the time of outputting the created document cannot be changed thereafter even by the document creator. Therefore, it is difficult to easily cope with a case where it becomes necessary to distribute a copy to a larger number of people later or when the original is lost.

  Therefore, in the second embodiment, when it is recognized that the user is a document creator or an authorized user, it is possible to change the set copy limit and the permitted number of copies when copying the document. And

  Details of the configuration will be described below.

  As in the first embodiment, the document creator can set copy restrictions, the allowable number of copies, and a password with a printer driver of the PC when outputting the document.

  FIG. 10 shows an example of the printer driver screen of this embodiment. The user (administrator) can set copy restrictions, the number of permitted copies, the addition of a background pattern, and a password. In the present embodiment, not only the permitted number of times of copying but also password information is included, and therefore, it is desirable that the encryption marking has a large amount of information such as a two-dimensional barcode. Other configurations at the time of document output are the same as those in the first embodiment.

  Next, FIG. 11 shows a flowchart at the time of document copy in the present embodiment. The processing of this flowchart is executed by the control unit 201 in FIG.

  In this embodiment, the processing content of steps S1601 to S1603 is the same as that of steps S1401 to 1403 in FIG. 8 of the first embodiment.

  In step S1603, the encryption marking printed on the document is detected. The control unit 201 causes the decryption unit 204 to decrypt the detected cryptographic marking, obtains information on the permitted number of copies n included therein and the password set at the time of creation, and the memory ( RAM).

  In step S1604, the control unit 201 determines whether to change the copy restriction and the allowable number of copies. When the change is made, the processes of steps S1612 to S1614 are performed.

  Specifically, as shown in FIG. 12, information on the copy restriction of the original and the remaining number of permitted copies is displayed on the operation unit 202. When the “Next” key is pressed, as shown in FIG. 13, it is displayed that the copy restriction and the allowable number of copies can be changed. However, only an operator (administrator) having change authority can make changes. When the user wishes to change the password, when the “Next” key is pressed, a screen for requesting a password is displayed as shown in FIG. By inputting the password from the operation unit and pressing the OK key (step S1612), the control unit 201 determines whether or not the input password is correct (step S1613). If the input password is correct, the control unit 201 causes the operation unit 202 to display a screen for changing the copy restriction and the allowable number of copies as shown in FIG. When the changed value is input from the operation unit and the OK key is pressed, the setting is changed (step S1614), and the changed setting is displayed as shown in FIG.

  Steps after step S1605 are the same as those after step 1404 in FIG. 8 of the first embodiment.

  If the allowable number of copying is n = 0 in step S1605, the process may proceed to step S1611 as in the first embodiment.

  In the description of this embodiment, the creator sets a password when creating a document, and the copy restriction can be changed by inputting the password when copying a document. However, the key for permitting the change of the copy restriction information is limited to the password. Not that. For example, it may be the document creator's user ID or affiliation code. When a plurality of users are authorized to change, it is desirable to use a key that is common to a plurality of users, such as an affiliation code.

  As described above, according to the configuration of the present embodiment, a copy restriction change key such as a password is included in the encryption marking in advance when a document is created, so that an authorized user changes the copy restriction at the time of copying. It becomes possible. Therefore, it is possible to provide more flexible copy protection in various usage environments, and it is possible to prevent the spread of confidential information.

1 is a configuration cross-sectional view of an image forming apparatus to which the present invention can be applied. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus. Schematic which shows the structure of a background pattern. 10 is a flowchart of print processing for adding copy restriction information. The figure which shows a printer driver screen. The figure which shows the example of encryption marking. The figure which shows the example of encryption marking. 10 is a flowchart showing processing when copying a document with copy restriction information. The figure which shows the example of the operation part screen at the time of copy prohibition. The figure which shows a printer driver screen. 9 is a flowchart showing processing at the time of copying in the second embodiment. The figure which shows the operation part screen at the time of copy restriction. The figure which shows the operation part screen at the time of copy restriction. The figure which shows the operation part screen at the time of copy restriction. The figure which shows the operation part screen at the time of copy restriction. The figure which shows the operation part screen at the time of copy restriction. The figure which shows the concept of a copy restriction. The figure which shows the conventional copy suppression original document. The figure which shows the copy state of the conventional copy suppression original. The figure which shows the copy state of the conventional copy suppression original.

Explanation of symbols

DESCRIPTION OF SYMBOLS 111 Scanner part 112 Printer part 204 Decryption part 206 Filter part 207 Background pattern production | generation part 208 Ground pattern synthesis part 209 Encryption part 210 Encryption composition part

Claims (9)

An image forming apparatus control method comprising:
A reading step that includes a latent image portion and a background portion, and reads a document in which copy restriction information for limiting the number of times of copying and a copy-forgery-inhibited pattern on which the latent image portion appears in the copy image;
A decoding step of decoding the copy restriction information given to the document image read in the reading step;
A removal step of removing the tint block from the document read in the reading step;
An update step for updating the copy restriction information decrypted in the decryption step;
Forming the copy restriction information updated in the update step on a sheet together with the image in which the copy-forgery-inhibited pattern is removed from the document image in the removal step;
A control method for an image forming apparatus, comprising: A tint block generation step for generating tint block image data representing the tint block;
The combining step includes combining the copy restriction information updated in the updating step and the copy-forgery-inhibited pattern image data generated in the copy-forgery-inhibited pattern generation step into an image in which the copy-forgery-inhibited pattern is removed from the document image in the removing step. Item 8. A method for controlling an image forming apparatus according to Item 1.   2. The method of controlling an image forming apparatus according to claim 1, wherein in the updating step, a copy allowable number included in the copy restriction information is subtracted.   2. The method of controlling an image forming apparatus according to claim 1, wherein when the copy restriction information is not given to the document read in the reading step, the background pattern is not removed by the removing step.   2. The control method for an image forming apparatus according to claim 1, further comprising a permission step of permitting an operator to manually set an update value of the copy restriction information in the update step.   An encryption step for encrypting the copy restriction information after the update in the update step, wherein the forming step combines the encrypted copy restriction information with the image from which the copy-forgery-inhibited pattern has been removed in the removal step; The method of controlling an image forming apparatus according to claim 1. A reading device that includes a latent image portion and a background portion, and reads a document in which copy restriction information for limiting the number of times of copying and a copy-forgery-inhibited pattern on which the latent image portion appears when copied.
A decoding unit for decoding the copy restriction information attached to the document image read by the reading device;
A removing unit that removes the background pattern from the document read by the reading device;
An update unit for updating the copy restriction information decoded by the decoding unit;
A combining unit that forms the copy restriction information updated by the updating unit on a sheet together with an image in which a background pattern has been removed from the original image by the removing unit;
An image forming apparatus comprising: An image forming apparatus control method comprising:
A first setting step for setting copy restriction information for restricting the number of copies for image data to be printed;
A second setting step including setting a latent image portion and a background portion to add to the image data a copy-forgery-inhibited pattern in which the latent image portion appears in the copied image when copied;
A synthesis step of synthesizing the copy restriction information and the copy-forgery-inhibited pattern image data representing the copy-forgery-inhibited pattern with the image data;
An image forming step of forming an image on a sheet based on image data obtained by combining the copy restriction information and the copy-forgery-inhibited pattern image data;
A control method for an image forming apparatus, comprising:   9. The image forming method according to claim 8, further comprising: an encryption step for encrypting the copy restriction information set in the first setting step, wherein the combined step combines the encrypted copy restriction information with the image data. Control method of the device.

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