JP2008085735A - Image processing device - Google Patents

Abstract

Even if a similar image similar to the specific image exists in the input image data, the specific image is detected without being confused by the similar image, and the processing can be reliably restricted.
A specific image determination unit for detecting a specific image in image data and determining whether the image data includes a specific image based on a threshold value, and a similar image having a form similar to the specific image When the number of detected specific images exceeds the threshold, control for limiting the processing to be executed when the number of detected specific images exceeds the threshold is determined so that the similar image does not affect the determination of the specific image. Part 7.
[Selection] Figure 1

Description

  The present invention relates to an image processing apparatus that restricts processing such as copying, facsimile communication, and data transmission based on a specific image included in image data.

  In the image processing apparatus, processing for inputting image data and outputting it by copying, facsimile communication, and data communication is executed. When the specific image is included in the image data, the processing to be executed is restricted, such as prohibiting the processing. Thereby, illegal use of the input image data can be prevented.

  Usually, a document is formed so that a plurality of specific images are included in one page of image data. A specific image is detected from image data input by reading this document. At this time, in order to reliably determine that the specific image is included, the number of specific images is counted. When the number of specific images exceeds the threshold, it is determined that there is a specific image, and processing is limited.

For example, in Patent Document 1, a threshold for identifying specific images such as banknotes and securities is set for each type of image data such as copy data, facsimile data, and printer data. When it is detected that the specific image is included in the input image data, printing of the image data is prohibited.
Japanese Patent Laid-Open No. 2001-94771

  By the way, there exists an image having a form similar to the specific image in the input image data such that the specific image is similar to the background of the document. There is a possibility that the specific image is mixed with such a similar image and the specific image is not detected. For this reason, the number of detected specific images does not exceed the threshold value, and the processing is not limited where the processing should be limited.

  SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an image processing apparatus that can reliably perform processing restriction even when a similar image similar to a specific image exists in image data.

  The present invention includes a detection unit that detects a specific image in image data, a determination unit that determines whether a specific image is included in the image data based on a threshold value, and a similar image having a form similar to the specific image. And a change unit that changes the threshold when detected.

  If a similar image exists in the image data, the detection of a specific image is affected. Therefore, the changing unit changes the threshold value so as to eliminate the influence of the similar image. Along with this change, the specific image can be correctly determined without being influenced by the similar image by regarding the similar image as the specific image or ignoring the specific image that is difficult to distinguish from the similar image.

  When the specific image is an image oriented in a certain direction, the detection unit detects a similar image oriented in a different direction. That is, the changing unit changes the threshold based on the arrangement of specific images within a predetermined range.

  When a plurality of specific images are arranged in a certain direction, the detection unit detects similar images facing in different directions. When a similar image is detected, a part of the arrangement within the predetermined range is different. At this time, the changing unit changes the threshold value.

  When a specific image is detected, a control unit that restricts processing to be executed is provided, and when a similar image exists, the determination unit determines whether the detected specific image exceeds the changed threshold, and determines that it has exceeded When it is done, the control unit limits the processing to be executed. When the detected specific image does not exceed the changed threshold value, the process is executed without restriction.

  The detecting unit detects a specific image within a predetermined range, and when a similar image is detected, the changing unit lowers the threshold value. In this case, by ignoring the specific image that is difficult to distinguish from a similar image, the determination can be made based only on the specific image that can be reliably determined to be the specific image. This eliminates erroneous detection of specific images.

  The detection unit detects a specific image within a predetermined range, and when a similar image is detected, the changing unit divides the predetermined range into a plurality of regions and determines a threshold value for each region. In each region, a specific image is determined.

  The number of area divisions varies depending on the size of the predetermined range. The larger the predetermined range, the greater the number of divisions. As a result, the size of each region can be made the same, and there is no variation in the determination of specific images.

  The changing unit divides the target region including the similar image into the non-target region that does not include the threshold value, and the threshold value in the target region is larger than the threshold value determined from the ratio of the target region in the predetermined range. The threshold value is determined from the ratio of the non-target area in the predetermined range. Since a similar image exists in the target area, the similar image may be erroneously detected as a specific image. However, the threshold value is set larger than usual so that similar images may be included, so that it is possible to detect all the specific images and to make a reliable determination.

  According to the present invention, even if a similar image exists in the image data, it is possible to correctly determine the specific image without being affected by the similar image by changing the threshold value. This makes it possible to reliably execute processing restrictions on image data including a specific image.

  An image processing apparatus of this embodiment is shown in FIG. The image processing apparatus is a multifunction machine that executes a copy mode, a print mode, a scanner mode, and a facsimile mode. The image processing apparatus 2 reads an original and inputs image data into a cabinet 1 and processes the image data. The image forming unit 3 for printing, the storage unit 4 for storing the image data, the communication unit 5 for communicating with the external device, the operation panel 6 for input operation, and the processing unit are controlled, and the image according to the mode And a control unit 7 that executes data processing. The processing unit performs processing to output input image data, and includes the image forming unit 3, the storage unit 4, and the communication unit 5.

  As shown in FIG. 2, the image reading unit 2 is disposed above the cabinet 1 and includes a scanner unit 10 and an automatic document feeder 11. The automatic document feeder 11 is provided above the scanner unit 10 and automatically conveys a document in order to read image data of the document.

  A document table 12 made of platen glass is provided on the upper surface of the cabinet 1, and a document cover 13 that covers the document table 12 is provided. The automatic document feeder 11 is integrally mounted on the document cover 13. The document cover 13 can be freely opened and closed. When the document cover 13 is in a closed state, the document is conveyed by the automatic document conveyance unit 11. When the document cover 13 is open, the document can be placed on the document table 12. Opening / closing of the document cover 13 is detected by a cover opening / closing sensor. A document size detection sensor for detecting the size of the document placed on the document table 12 is also provided.

  When a document is set on the document set tray 15 of the automatic document feeder 11, the document detection sensor 16 detects that the document has been set. Then, on the operation panel 6, copy conditions such as the size of the sheet to be printed and the scaling ratio are input. Thereafter, reading of the image of the document is started by an input operation of the start key.

  In the automatic document feeder 11, each document on the document set tray 15 is pulled out one by one by the pickup roller 17. The document passes through between the separating plate 18 and the transport roller 19 and is sent to the document table 12. The document is transported in the sub-scanning direction on the document table 12 and discharged to the document discharge tray 20. The document discharge tray 20 is provided with a document discharge sensor to detect the presence or absence of a document on the document discharge tray 20.

  The scanner unit 10 includes a first reading unit 21 and a second reading unit 22. A reading area is formed on one side of the document table 12 and passes through the reading area when the document is conveyed on the document table 12. Below the reading area, the first scanning unit 23 of the first reading unit 21 is positioned, and the surface (lower side) of the document is read.

  When the document is transported to the document table 12 by the automatic document transport unit 11, the first scanning unit 23 is moved to the reading position and positioned, and the second scanning unit 24 is also positioned at a predetermined position. The surface of the document is irradiated from below the document table 12 by the exposure lamp of the first scanning unit 23. Reflected light from the document is guided to the imaging lens 25 by the respective reflection mirrors of the first and second scanning units 23 and 24. The reflected light of the document is condensed on the CCD 26 by the imaging lens 25. An image on the surface of the document is formed on the CCD 26. As a result, the image on the surface of the conveyed document is read.

  Further, the second reading unit 22 reads the back surface (upper side surface) of the document. The second reading unit 22 is disposed above the document table 12 and has an LED that irradiates the back side of the document, an exposure lamp array having a fluorescent lamp, a self-focal lens array that collects reflected light of the document for each pixel, and a cell. A contact image sensor (CIS) that photoelectrically converts reflected light from a document received through a fock lens array and outputs an analog image signal is provided. As a result, the image on the back side of the conveyed document is read.

  When a document is placed on the document table 12, the first reading unit 21 reads an image on the surface of the document. The first and second scanning units 23 and 24 move in the sub-scanning direction while maintaining a predetermined speed relationship with each other. The document on the document table 12 is exposed by the first scanning unit 23, and reflected light from the document is guided to the imaging lens 25 by the first and second scanning units 23 and 24. An image of the original is formed on the CCD 26 by the imaging lens 25.

  When the image on one or both sides of the document is read in this way, the image data on one or both sides of the document is input to the control unit 7. The control unit 7 includes an image data processing unit, and the image data processing unit performs various types of image processing on the image data. This image data is output to the image forming unit 3.

  The image forming unit 3 prints a color image or a monochrome image on the sheet based on the input image data. The image forming unit 3 includes a laser scanning unit 30, four image stations 31, an intermediate transfer belt unit 32, a fixing device 33, and a conveying device 34.

  Each image station 31 forms a color image corresponding to each color of black, cyan, magenta, and yellow. Each image station 31 includes a photosensitive drum 35, a developing device 36, a charging device 37, a cleaning device 38, and a charge eliminating device (not shown).

  The photosensitive drum 35 is rotationally driven in one direction, the cleaning device 38 cleans the residual toner on the surface of the photosensitive drum 35, and the neutralization device neutralizes the surface of the photosensitive drum 35. The charging device 37 uniformly charges the surface of the photosensitive drum 35.

  The laser scanning unit 30 modulates laser light based on image data input from an image reading unit or the like, and repeatedly scans the surface of the photosensitive drum 35 in the main scanning direction with this laser light, thereby generating an electrostatic latent image. It is formed on the surface of the photosensitive drum 35. The developing device 36 supplies toner to the surface of the photosensitive drum 35 to develop the electrostatic latent image, and forms a toner image on the surface of the photosensitive drum 35.

  The intermediate transfer belt unit 32 includes an intermediate transfer belt 40, an intermediate transfer roller 41, a transfer belt cleaning device 42, and a tension mechanism 43. The intermediate transfer belt 41 is disposed above each photosensitive drum 35, is wound around the driving roller 44 and the driven roller 45, and rotates in the direction of arrow B.

  The intermediate transfer roller 41 is disposed to face the photosensitive drum 35 with the intermediate transfer belt 40 interposed therebetween, and a transfer bias voltage is applied thereto. The toner image on the surface of the photosensitive drum 35 is transferred to the intermediate transfer belt 40 by applying a voltage having a polarity opposite to that of the toner by the intermediate transfer roller 41. The toner images of the respective colors are laminated on the intermediate transfer belt 40, and a combined multi-color toner image is formed.

  The transfer roller 41 is disposed in pressure contact with the intermediate transfer belt 40, and a voltage having a polarity opposite to that of the toner is applied. The toner image on the intermediate transfer belt 40 is transferred onto the sheet conveyed between the transfer roller 46 and the intermediate transfer belt 40 by the transfer roller 46. The toner remaining on the intermediate transfer belt 40 is removed by the transfer belt cleaning device 42.

  The toner image transferred to the sheet is heated and pressurized by the fixing device 33 and fixed on the sheet, and an image is formed on the sheet. The sheet on which the image is printed in this manner is discharged to a discharge tray 50 provided at the top of the cabinet 1.

  The transport device 34 transports the sheet from the sheet cassette 51 or the manual feed tray 52 along the transport path 53. The conveyance path 53 passes between the intermediate transfer belt 40 and the transfer roller 46, passes through the fixing device 33, and reaches the discharge tray 50.

  The transport device 34 includes a pickup roller 54, a transport roller 55, a registration roller 56, and a discharge roller 57. The sheets in the sheet cassette 51 or the manual feed tray 52 are sent one by one to the transport path 53, transported through the transport path 53, and discharged to the discharge tray 50. An image is printed on the sheet during conveyance of the sheet. In addition, a switchback conveyance path 58 is provided for duplex printing. The sheet after fixing passes through the switchback conveyance path 58 by the conveyance roller 55 and is conveyed between the intermediate transfer belt 40 and the transfer roller 46. The sheet printed on both sides passes through the fixing device 33 and is discharged to the discharge tray 50.

  The operation panel 6 is provided in the scanner unit 10 and includes an operation unit 60 and a display unit 61. The operation unit 60 includes various operation keys. The display unit 61 includes a liquid crystal display and is a touch panel. Touch keys are formed in the operation screen displayed on the display unit 61, and these also function as operation keys.

  The communication unit 5 includes a communication interface, and the communication interface is connected to a network such as a LAN or a WAN. A plurality of external devices are connected to the network. The external device is another image processing device, an information processing device such as a personal computer, or a server. The network is connected to the Internet from a router through a communication line such as a telephone line or an optical fiber. The communication unit 5 can communicate with an external device through a network using a predetermined communication protocol. The image processing apparatuses can also communicate with each other. Communication within the network may be wired or wireless. An image processing system is formed by these image processing devices and external devices.

  The communication unit 5 includes a modem device. A telephone line is connected to the modem device. The image processing apparatus can perform facsimile communication. The image processing apparatus can also perform data communication by Internet facsimile through a network. Furthermore, the communication unit 5 includes a communication terminal and a communication card for wireless communication. A storage medium such as a USB memory or an IC card is connected to the communication terminal, and the communication unit 5 transmits / receives data to / from the storage medium. In addition, data is transmitted and received by wireless communication with a communication terminal such as a mobile phone or PDA through a communication card.

  The storage unit 4 includes a hard disk device. The storage unit 4 stores image data input from the image reading unit 2 or image data input from the communication unit 5. The input image data is temporarily stored in an image memory such as a DRAM, subjected to image processing and encryption processing, and then transferred from the image memory to the storage unit 4. Further, when image data is read from the storage unit 4, the image data is subjected to image processing and decoding processing and stored in an image memory. Thereafter, the image data is output to the outside by printing, data transmission, and facsimile communication according to the processing to be executed.

  The storage unit 4 includes a management table 62, and information necessary for operating the image processing apparatus such as control information, setting information, and user authentication information of the image processing apparatus is stored in the management table 62. When these pieces of information are created and changed, the information in the management table 62 is updated. The management table 62 may be provided in a non-volatile memory different from the storage unit 4.

  The control unit 7 includes a microcomputer having a CPU, a ROM, and a RAM. The CPU reads a control program stored in the ROM into the RAM and executes the control program. Each unit operates according to the control program. When image data is input, one of the print mode, copy mode, scanner mode, and facsimile mode is selected based on the processing conditions included in the input information from the operation unit 60 and the header information of the image data input from the external device. Mode is executed. In addition, the control program includes a browser and mail software, and the control unit 7 performs data communication with an external device or transmits / receives e-mails using a communication protocol such as TCP / IP protocol.

  The control unit 7 temporarily stores the input image data in the storage unit 4 when performing each mode. Further, the control unit 7 executes a filing mode in which the input image data is stored in the storage unit 4 and managed. The stored image data is re-output according to the instructed process.

  The output image data is erased from the storage unit 4 according to an instruction from the control unit 7. At the time of this erasure, the image data is invalidated so that it cannot be restored by overwriting the image data with random data. In this way, invalidation of image data is prevented by performing invalidation processing and further encryption processing.

  Here, in order to prevent the confidential document from being illegally copied or transmitted by facsimile, a specific image is added to the document. The specific image represents restriction information for restricting processing to be executed such as copy prohibition, deterioration of print image quality, data transmission or facsimile communication prohibition, and filing prohibition.

  The control unit 7 generates image data obtained by combining the specific images, and performs processing such as printing, data transmission, and filing of the combined image data. Image information for the specific image is stored in the management table 62 in advance. The image information includes the form of the specific image, image forming conditions, position, and the like. The control unit 7 reads out the image information, generates a specific image based on the image information, and combines it with the input image data.

  When the image data is printed, a document including a specific image as shown in FIG. 3 is created. The specific image has a pattern in which a plurality of images are linearly arranged in a certain direction. Specific images of the same form are arranged in a certain direction and regularly arranged at predetermined positions. A single page of the document includes a plurality of specific images. Further, image data including the specific image is transmitted through the communication unit 5. When the image processing apparatus receives the image data and prints the image data, a document including the specific image is created.

  It is difficult for humans to visually recognize a specific image of a document. However, the specific image can be read by the image reading unit 2. Therefore, a specific image determination unit 63 is provided that detects whether or not the specific image is included in the input image data and determines whether or not the specific image exceeds a threshold value. The image data is not limited to those input from the image reading unit 2 but is input from an external device, a storage medium, or a communication terminal through the communication unit 5.

  The specific image determination unit 63 is controlled in operation by the control unit 7 and detects a specific image by performing pattern matching between the input image data and image data corresponding to the specific image. Image data corresponding to the specific image is registered in advance and stored in the management table 62. Then, the specific image determination unit 63 counts the number of detected specific images, and determines whether or not the number of detected specific images exceeds a threshold value. When the image data is in page units, the number of specific images is calculated for each page. Alternatively, the number of specific images in a predetermined area area is calculated.

  A threshold value determination unit 64 for determining the threshold value is provided. The threshold determination unit 64 stores the threshold set by the authorized user like the administrator in the management table 62. Authorized users are authenticated by inputting authentication information such as biometric information such as passwords and fingerprints. The authenticated user can set a threshold value through the operation unit 60.

  The control unit 7 restricts the processing to be executed when the specific image is included in the input image data exceeding the threshold value. That is, the control unit 7 instructs copy prohibition in the copy mode, and instructs transmission prohibition in the facsimile mode or the scanner mode. In the filing mode, the storage unit 4 is instructed to prohibit image data from being saved. Note that, even if a specific image is detected, the control unit 7 does not limit the processing when the number does not exceed the threshold value.

  By the way, there is a similar image similar to a specific image, such as a background of a document or a ground pattern. As shown in FIG. 4, the similar image has a pattern in which a plurality of images are linearly arranged in an arbitrary direction. That is, the specific image has a certain angle, while the similar image is oriented in an arbitrary direction at an angle different from that of the specific image.

  Such a similar image may be erroneously recognized as a specific image. For example, when a document is read and image data is input, the tilted document is read. When the similar image as described above exists, the image is directed in a certain direction similar to the specific image, and the similar image is detected as the specific image.

  If there are similar images, the arrangement of the specific images changes. Therefore, the threshold value determination unit 64 changes the threshold value according to a change in the arrangement of specific images within a predetermined range. That is, the specific image determination unit 63 detects a similar image in the input image data. When a similar image is detected, the threshold value determination unit 64 changes the threshold value so that the presence of the similar image does not affect the determination of the specific image for executing the process restriction.

  Based on the detection of the specific image, the operation when the process is executed will be described with reference to FIG. Here, the document is read and image data is input. First, the user sets a document on the image reading unit 2 and operates the operation keys on the operation panel 6. The original is read and image data is input (S1). The specific image determination unit 63 detects a specific image from the image data input from the image reading unit 2 (S2). If the specific image is not detected, the instructed processing such as printing and data transmission is executed (S8).

  When the specific image is detected, the specific image determination unit 63 confirms whether a similar image is included. That is, the angle of the detected specific image is checked (S5). When only a specific image having a certain angle is detected, there is no similar image. At this time, the specific image determination unit 63 counts the detected specific images (S6), and determines whether or not the number of specific images exceeds the threshold (S7).

  When the threshold value is not exceeded, instructed processing such as printing and data transmission is executed (S8). When the threshold value is exceeded, the processing is restricted (S11). For example, copying is prohibited in accordance with the instructed processing. Although copying is performed according to the restriction information indicated by the specific image, there is a case where processing for reducing the image quality is performed.

  When a similar image having a different angle is detected, the threshold value determination unit 64 lowers the threshold value (S9). Here, the threshold reduction number is a predetermined fixed number. Since the image data is processed in units of pages, when the threshold value is determined according to the page size, the decrease number is determined according to the page size, and the decrease number may be increased as the page size is larger.

  Then, the specific image determination unit 63 counts the specific images and determines whether or not the number of specific images exceeds the changed threshold value (S10). When the number of specific images exceeds this threshold, processing is limited (S11). If not, the instructed process is executed (S8).

  As described above, when a similar image exists in the image data, it is difficult to distinguish the specific image from the similar image. At this time, without counting the specific images that are difficult to discriminate, only the specific images that can be reliably discriminated are counted to determine whether the threshold value is exceeded. Since confusing similar images are not counted, only specific images can be detected accurately. Although the number of specific images to be counted is reduced, the changed threshold value is lowered. Therefore, the specific image can be correctly determined, and the processing can be surely limited.

  In the above embodiment, the threshold value of the entire page is lowered. However, as another embodiment, when a similar image is detected, the predetermined range is divided into a plurality of regions, and the threshold value for each region is determined. That is, as shown in FIG. 6, the specific image determination unit 63 divides one page into a plurality of regions. The entire page is divided equally and the area of each region is equal. Note that the number of area divisions varies depending on the page size. As the page size increases, the number of divisions increases. However, the size of each area is the same regardless of the page size. Therefore, the size of the specific image and the size of each region are always the same, and there is no variation in detection accuracy, so that the specific image can be reliably detected.

  Then, the specific image determination unit 63 discriminates between a region including a similar image and a region not including the similar image, a region including the similar image as a target region A, and a region not including the similar image as a non-target region B. Divide into two. The threshold value determination unit 64 determines a threshold value in the target area A and a threshold value in the non-target area B.

  Specifically, as shown in FIG. 7, when a similar image is detected (S5), the specific image determination unit 63 subdivides one page that is a predetermined range into a plurality of regions as shown in FIG. (S9) The region including the similar image is specified and the target region A is determined (S10). Within one page, areas other than the target area A are non-target areas B. The threshold value determination unit 64 calculates the area ratio of the target area A in one page. Then, the threshold is determined by adding α to the threshold corresponding to the area ratio (S11). Next, a threshold value is determined according to the area ratio of the asymmetric region B (S12).

  That is, the threshold value in the target area A is larger than the threshold value determined from the ratio of the target area A in the predetermined range, and the threshold value in the non-target area B is the threshold value determined from the ratio of the non-target area B in the predetermined range. It is said. Specifically, if the area of one page is S, the area of the target region A is Sa, the area of the non-target region B is Sb, and the threshold is N, the threshold of the target region A is Sa / S × N + α, non-target The threshold value of the region B is Sb / S × N. Here, α is a predetermined number. Note that α may be a number determined according to the area ratio of the target region A.

  The specific image determination unit 63 counts the specific image in the target area A and counts the specific image in the non-target area B. In at least one of the target area A and the non-target area B, the process is restricted when the number of specific images exceeds the changed threshold (S13). In any region, when the threshold value is not exceeded, the instructed process is executed (S8).

  As described above, when a similar image exists in the image data, the region where the similar image exists is specified, and the image including the similar image that is difficult to distinguish from the specific image is counted to determine whether the threshold value is exceeded. . Although the number of specific images to be counted increases, the specific images can be detected without leaking. As a result, the processing can be surely limited.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. When one page is divided into a plurality of areas, instead of dividing the area into target areas and non-target areas, a threshold may be determined according to the presence or absence of similar images for each area, and a specific image in each area may be counted. .

  The specific image is not limited to a form directed in a certain direction, but may be a form having an irregular pattern, a character image such as “copy prohibited” or “confidential”, or a form combining characters and patterns. When the specific image is a character image, it is unlikely that a similar image exists, but a malicious user may craft the specific image and make it look like a similar image. In such a case, it is useful to determine the specific image by changing the threshold value.

Control block diagram of image processing apparatus of the present invention The figure which shows the schematic whole structure of an image processing apparatus Figure showing a document with specific images arranged and enlarged specific images Figure showing a document with similar images Flowchart for determining a specific image in image data where a similar image exists The figure which shows the state where the page is divided into the plural areas Flowchart for determining a specific image in image data where a similar image exists

Explanation of symbols

2 image reading unit 3 image forming unit 4 storage unit 5 communication unit 6 operation panel 7 control unit 63 specific image determination unit 64 threshold value determination unit A target region B non-target region

Claims (9)

When a detection unit that detects a specific image in the image data, a determination unit that determines whether or not the specific image is included in the image data based on a threshold value, and a similar image that is similar to the specific image are detected An image processing apparatus comprising: a changing unit that changes a threshold value. The image processing apparatus according to claim 1, wherein the specific image is an image directed in a certain direction, and the detection unit detects a similar image directed in a different direction. A detection unit that detects a specific image in the image data, a determination unit that determines whether or not the specific image is included in the image data, and a threshold value that is changed based on the arrangement of the specific image within a predetermined range An image processing apparatus comprising: a changing unit that A plurality of specific images are arranged in a certain direction, the detection unit detects a similar image directed in a different direction, and when the similar image is detected, the changing unit changes the threshold value. The image processing apparatus according to claim 3. When a specific image is detected, the controller includes a control unit that restricts processing to be executed, and the determination unit determines whether the detected specific image exceeds a threshold after the change. 5. The image processing apparatus according to claim 1, wherein the processing is limited. The image processing apparatus according to claim 1, wherein the detection unit detects a specific image within a predetermined range, and when the similar image is detected, the change unit decreases the threshold value. The detection unit detects a specific image within a predetermined range, and when a similar image is detected, the changing unit divides the predetermined range into a plurality of regions and determines a threshold value for each region. The image processing apparatus according to 2 or 4. The image processing apparatus according to claim 7, wherein the number of divisions of the region differs according to the size of the predetermined range. The changing unit divides the target region including the similar image into the non-target region that does not include the threshold value, and the threshold value in the target region is larger than the threshold value determined from the ratio of the target region in the predetermined range. The image processing apparatus according to claim 7, wherein the threshold value is determined based on a ratio of the non-target region in a predetermined range.

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