JP7380270B2 - Image processing device and image processing program - Google Patents

Description

The present invention relates to an image processing device and an image processing program.

For example, Patent Document 1 describes a CIS type image reading device. When reading a double-page spread book document on the document table, this image reading device detects that if the white background reading output value in a predetermined range decreases while scanning the document surface, it determines that it is the binding margin of the document and reads it. At the same time as extending the accumulation time of A control means is provided for restoring the reading accumulation time and the moving speed of the traveling body to their original values, and also returning the MTF correction coefficient to its original weak coefficient.

Further, Patent Document 2 describes an image processing apparatus that accurately determines a specific image even when a document is floating above a document placement surface. This image processing device includes a reading section that reads a document placed on a document placement surface to obtain image data, a first processing section that performs a first process on the image data obtained by the reading section, and a first processing section that performs a first process on the image data obtained by the reading section. and a determining means for determining whether specific image data is included in the image data subjected to the first processing by the first processing unit. The image processing device also includes a second processing section that performs a second processing different from the first processing on the image data obtained by the reading section, and an image data that has been subjected to the second processing by the second processing section. The image forming apparatus includes a generating means for generating output image data based on the output image data, and an output means for outputting the output image data. Further, the first process and the second process are processes that perform edge emphasis on image data, and the first process has a higher degree of edge emphasis than the second process.

Japanese Patent Application Publication No. 11-215329 Japanese Patent Application Publication No. 2008-199683

For example, when a double-page spread including a bound portion of a book, a notebook, or the like is set on a document table, the binding portion may float off the document table. If a double-page spread is read with the binding section floating above the document table, floating fog will occur due to the binding section, and resolution in the vicinity of the binding section will decrease.

To deal with this, it is conceivable to remove the background color from the image obtained by reading, but it is difficult to suppress the decrease in resolution near the binding portion by removing the background color alone.

The present invention provides an image processing device that can suppress a decrease in resolution in the vicinity of a binding part of an image, compared to a case where only background color removal is performed on an image obtained by reading a double-page spread including a binding part. and image processing programs.

In order to achieve the above object, an image processing apparatus according to a first aspect includes a processor, the processor detects the background color of an image obtained by reading a double-page spread including a binding part, and Filter processing is performed to remove the ground color from the image and emphasize areas in the image where the density value of the ground color is smaller than a first threshold value and larger than a second threshold value.

Further, in an image processing apparatus according to a second aspect, in the image processing apparatus according to the first aspect, the filtering process is performed on the image after the background color is removed.

Further, in the image processing apparatus according to the third aspect, in the image processing apparatus according to the first aspect or the second aspect, when the processor detects an area that does not include a halftone period from the image, Then, the ground color is detected.

Further, in the image processing apparatus according to a fourth aspect, in the image processing apparatus according to the third aspect, when the processor detects only a region including a halftone dot period from the image, is not detected.

Further, in the image processing apparatus according to the fifth aspect, in the image processing apparatus according to the third aspect or the fourth aspect, the detection of the halftone dot period is performed by frequency-analyzing the image.

Further, in the image processing apparatus according to a sixth aspect, in the image processing apparatus according to any one of the first to fifth aspects, the image is placed on the double-page spread placed on the document table in a close-contact manner. It is said that this is an image read by an image sensor.

Further, in the image processing apparatus according to a seventh aspect, in the image processing apparatus according to any one of the first to sixth aspects, the filter processing is performed on a plurality of n×n (n is 3 This is done by selectively using filters (odd numbers above).

Further, in the image processing device according to an eighth aspect, in the image processing device according to the seventh aspect, the processor gradually increases the degree of emphasis by the filtering toward the center of the binding portion of the region. The plurality of n×n filters are selectively switched as shown in FIG.

Further, in the image processing apparatus according to a ninth aspect, in the image processing apparatus according to the eighth aspect, when the processor detects a change point at which the density value of the ground color changes by a predetermined value or more, A plurality of n×n filters are selectively switched.

Furthermore, in order to achieve the above object, the image processing program according to the tenth aspect detects a background color in an image obtained by reading a double-page spread including a bound portion, and removes the background color from the image. Then, the computer is caused to perform a filtering process for emphasizing a region of the image in which the density value of the ground color is smaller than a first threshold value and larger than a second threshold value.

According to the first aspect and the tenth aspect, the reduction in resolution near the binding part in the image is suppressed compared to the case where only the background color is removed from an image obtained by reading a double-page spread including the binding part. It has the effect that it can be done.

According to the second aspect, it is possible to more effectively suppress a decrease in resolution in the vicinity of the binding portion of the image, compared to the case where the filter processing is performed on the image before the background color is removed. .

According to the third aspect, there is an effect that the background color can be detected only for images that are likely to include a raised area.

According to the fourth aspect, it is possible to prevent background color detection from being performed for images that do not include raised areas.

According to the fifth aspect, there is an effect that the halftone dot period can be detected more appropriately than when frequency analysis is not performed.

According to the sixth aspect, even when a contact image sensor is used, it is possible to suppress a decrease in resolution in the vicinity of the binding portion of the image.

According to the seventh aspect, it is possible to more effectively suppress a decrease in resolution in the vicinity of the binding portion of an image, compared to the case where only one filter is used.

According to the eighth aspect, it is possible to more effectively suppress a decrease in resolution in the vicinity of the binding portion in an image, compared to a case where the degree of emphasis by filtering is constant.

According to the ninth aspect, there is an effect that filter switching can be performed more appropriately than in the case where a change point in the ground color density value is not detected.

FIG. 1 is a block diagram illustrating an example of an electrical configuration of an image forming apparatus according to an embodiment. (A) is a perspective view showing a schematic configuration of an image reading section according to an embodiment. (B) is a side view showing a schematic configuration of the image reading section according to the embodiment. FIG. 3 is a diagram illustrating an example of an image including a raised area due to a binding portion. FIG. 1 is a block diagram illustrating an example of a functional configuration of an image processing device according to an embodiment. It is a figure showing an example of an nxn filter concerning an embodiment. FIG. 3 is a diagram illustrating enhancement processing of an n×n filter according to an embodiment. (A) is a diagram showing an image according to a comparative example. (B) is a diagram showing an image according to the embodiment. 3 is a flowchart illustrating an example of the flow of processing by an image processing program according to an embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, an example of the form for implementing this invention is demonstrated in detail.

FIG. 1 is a block diagram showing an example of the electrical configuration of an image forming apparatus 20 according to this embodiment.

As shown in FIG. 1, the image forming apparatus 20 according to the present embodiment includes an image processing apparatus 10, a display section 21, an operation section 22, an image reading section 23, an image output section 24, and a communication section 25. , is equipped with. The image processing device 10 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, an input/output interface (I/O) 14, and a storage section 15. We are prepared. The image processing apparatus 10 according to the present embodiment is configured as an image processing section included in the image forming apparatus 20.

The CPU 11, ROM 12, RAM 13, and I/O 14 are each connected via a bus. Each functional section including a storage section 15, a display section 21, an operation section 22, an image reading section 23, an image output section 24, and a communication section 25 is connected to the I/O 14. Each of these functional units can communicate with the CPU 11 via the I/O 14.

A control unit is configured by the CPU 11, ROM 12, RAM 13, and I/O 14. The control unit may be configured as a sub-control unit that controls a part of the operation of the image forming apparatus 20, or may be configured as a part of a main control unit that controls the entire operation of the image forming apparatus 20. . For example, an integrated circuit such as an LSI (Large Scale Integration) or an IC (Integrated Circuit) chipset is used for a part or all of each block of the control section. Individual circuits may be used for each of the above blocks, or a part or all of them may be integrated. Each of the blocks described above may be provided integrally, or some blocks may be provided separately. Moreover, in each of the above-mentioned blocks, a part thereof may be provided separately. The integration of the control section is not limited to LSI, but a dedicated circuit or a general-purpose processor may also be used.

As the storage unit 15, for example, an HDD (Hard Disk Drive), an SSD (Solid State Drive), a flash memory, etc. are used. The storage unit 15 stores an image processing program 15A according to the present embodiment. Note that this image processing program 15A may be stored in the ROM 12.

The image processing program 15A may be installed in the image forming apparatus 20 in advance, for example. The image processing program 15A may be realized by being stored in a nonvolatile storage medium, or distributed via a network, and installed in the image forming apparatus 20 as appropriate. Note that examples of nonvolatile storage media include CD-ROM (Compact Disc Read Only Memory), magneto-optical disk, HDD, DVD-ROM (Digital Versatile Disc Read Only Memory), flash memory, memory card, etc. Ru.

For example, a liquid crystal display (LCD), an organic EL (electro luminescence) display, or the like is used for the display unit 21. The display unit 21 may integrally include a touch panel. The operation unit 22 is provided with various operation keys such as a numeric keypad and a start key. The display unit 21 and the operation unit 22 receive various instructions from the user of the image forming apparatus 20. These various instructions include, for example, an instruction to start reading a document, an instruction to start copying a document, and the like. The display unit 21 displays various information such as the results of processing executed in response to instructions received from the user and notifications regarding the processing.

The image reading unit 23 captures the originals placed on the paper feed tray of an automatic document feeder (not shown) provided at the top of the image forming apparatus 20 one by one, optically reads the imported originals, and obtains image information. get. Alternatively, the image reading unit 23 optically reads a document placed on a document table such as a platen glass to obtain image information.

The image output section 24 outputs an image based on the image information obtained by reading by the image reading section 23 onto a recording medium such as paper (hereinafter simply referred to as "paper"). Note that in this embodiment, an electrophotographic method will be exemplified and explained as a method for outputting an image.

When the image output method is an electrophotographic method, the image output section 24 includes a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, and a fixing device. The charging device applies a voltage to the photoreceptor drum to charge the surface of the photoreceptor drum. The exposure device forms an electrostatic latent image on the photoreceptor drum by exposing the photoreceptor drum charged by the charging device to light according to image information. The developing device forms a toner image on the photoreceptor drum by developing the electrostatic latent image formed on the photoreceptor drum with toner. The transfer device transfers the toner image formed on the photoreceptor drum onto paper. The fixing device fixes the toner image transferred to the paper by applying heat and pressure.

The communication unit 25 is connected to a network such as the Internet, a LAN (Local Area Network), or a WAN (Wide Area Network), and communicates with an external personal computer (PC) via the network. Communication is possible.

By the way, as described above, for example, when a double-page spread including a binding part of a book, a notebook, etc. is set on the document table, the binding part may float off the document table. If a double-page spread is read with the binding section floating above the document table, floating fog will occur due to the binding section, and resolution in the vicinity of the binding section will decrease. The mechanism by which this floating fog occurs will be specifically explained with reference to FIG. 2(A), FIG. 2(B), and FIG. 3.

FIG. 2(A) is a perspective view showing a schematic configuration of the image reading section 23 according to this embodiment. FIG. 2(B) is a side view showing a schematic configuration of the image reading section 23 according to this embodiment.

As shown in FIGS. 2A and 2B, the image reading unit 23 according to the present embodiment includes a contact image sensor (CIS) 23A and a platen glass 23B. . The contact image sensor 23A has a thin overall unit and is suitable for miniaturization, but because it has a structure that forms an image at the same magnification, the optical path length is shorter than a reading method using a CCD (Charge Coupled Device) and an imaging lens. It has the characteristics of a short focal length, a shallow depth of focus, and a large reading fluctuation when the focal position shifts.

Note that in FIGS. 2A and 2B, the direction in which the contact image sensor 23A moves is referred to as a reading direction, and the direction perpendicular to the reading direction is referred to as a line direction.

As an example, as shown in FIG. 2A, when two-page spreads of a book-shaped manuscript Bk (for example, a book, a notebook, etc.) including a binding part (for example, a spine part) are set on the platen glass 23B, As shown in FIG. 2(B), the binding portion is lifted from the platen glass 23B, and a floating portion W is generated.

FIG. 3 is a diagram illustrating an example of an image including a raised area due to a binding section.

As shown in FIG. 3, in an image G1 obtained by reading a double-page spread including a floating portion W with the contact image sensor 23A, a floating overlapping region R occurs at a position corresponding to the floating portion W, and a floating overlapping region R occurs near the binding portion. Resolution decreases.

The CPU 11 of the image processing device 10 according to the present embodiment functions as each unit shown in FIG. 4 by writing the image processing program 15A stored in the storage unit 15 into the RAM 13 and executing it. Note that the CPU 11 is an example of a processor.

FIG. 4 is a block diagram showing an example of the functional configuration of the image processing device 10 according to this embodiment.

As shown in FIG. 4, the CPU 11 of the image processing device 10 according to the present embodiment includes a halftone period detection section 11A, a ground color detection section 11B, a ground color removal section 11C, a floating fog determination section 11D, and a filter processing section 11E. functions as

The input image according to this embodiment is, for example, an image obtained by reading a double-page spread including a bound portion with the contact image sensor 23A, as shown in FIG. 3 described above. Note that the RGB (R: red, G: green, B: blue) data acquired by the contact image sensor 23A is divided into CMYK (C: cyan, M: magenta, Y: yellow, K: black) color spaces. It is converted into CMYK data that specifies the color of the pixel. The input image here is an image expressed as CMYK data.

The halftone dot cycle detection unit 11A according to this embodiment detects the halftone dot cycle with respect to the input image. The halftone dot period is the period of halftone dots appearing in a line direction perpendicular to the reading direction of the contact image sensor 23A. An area that does not include a halftone dot period in the line direction is likely to be a raised area, and an area that includes a halftone dot period in the line direction is likely to be a pattern area. Note that the picture area is an area that includes at least one of an image area and a character area. For detecting the dot period, known techniques described in, for example, Japanese Patent Laid-Open Nos. 2002-10067 and 2007-172067 are used. Specifically, the halftone dot period is detected by performing frequency analysis of the image using Fourier transform or the like.

When an area that does not include a halftone period is detected from the input image, the halftone period detection unit 11A determines that the input image includes a raised area, and sends the detection result of the halftone period along with the input image to the subsequent stage. It is output to the ground color detection section 11B. On the other hand, the halftone dot period detection unit 11A detects that the input image includes a picture area and is overlaid if a region that does not include a halftone dot period is not detected from the input image, that is, only a region that includes a halftone dot period is detected. It is determined that the input image does not include the area, and the input image is output without performing subsequent background color detection. Note that the halftone dot period detection section 11A is not necessarily necessary, and a configuration may be adopted in which the halftone dot period detection section 11A is omitted.

The background color detection unit 11B according to the present embodiment detects the background color of the input image when the halftone dot cycle detection unit 11A detects an area that does not include a halftone cycle. Note that as a method for detecting the ground color, a known technique described in, for example, Japanese Patent Laid-Open No. 2004-221915 may be used. The background color here refers to the color of the background portion of the document. The ground color detection section 11B outputs a ground color density value (for example, 0 to 255) as a detection result of the ground color to each of the subsequent ground color removal section 11C and floating fog determination section 11D.

The background color removal unit 11C according to this embodiment removes the background color detected by the background color detection unit 11B from the input image. Specifically, the ground color density value obtained from the ground color detection unit 11B is input, and the ground color is removed using a lookup table (LUT) for ground color removal prepared in advance. The background color removal unit 11C outputs the image after removing the background color from the input image to the floating fog determination unit 11D in the subsequent stage.

The floating overlay determination unit 11D according to the present embodiment determines, in the input image, an area where the background color density value is smaller than the first threshold value and larger than the second threshold value as an overlapping area due to the binding portion. Note that the first threshold value and the second threshold value used for determining the floating fog region are set based on, for example, a density value indicating that floating fog has occurred, which is measured in advance. When the ground color density value is x, for example, 5 (second threshold) < x < 50 (first threshold), more preferably 10 (second threshold) < x < 35 (first threshold). be. However, the density value of white is 0 and the density value of black is 255. When determining that a raised area is included, the raised overlay determination unit 11D outputs the determination result of the raised overlay area together with the image after removing the background color to the subsequent filter processing unit 11E. On the other hand, if the floating fog determination unit 11D determines that the floating fog area is not included, the image after removing the background color is output without being subjected to filter processing.

The filter processing unit 11E according to the present embodiment performs filter processing to emphasize the floating area on the floating area based on the floating area determination result by the floating area determining unit 11D. Specifically, as an example, an n pixel×n pixel (n is an odd number of 3 or more) filter shown in FIG. 5 is used. Note that n pixels×n pixels of the filter correspond to n pixels×n pixels of the input image. Hereinafter, a filter of n pixels×n pixels (n is an odd number of 3 or more) will be simply referred to as an n×n filter.

FIG. 5 is a diagram showing an example of an n×n filter according to this embodiment.

The n×n filter shown in FIG. 5 is an example of a filter when n=3, and the coefficient of the center pixel is “+2”. A filter having a "+" value in the coefficient of the central pixel is, for example, a filter that emphasizes black. The coefficient of the center pixel may be any value as long as it is a "+" value, and the larger the coefficient of the center pixel, the greater the degree of emphasis. However, the sum of the coefficients of multiple pixels (8 pixels in the example of FIG. 5) arranged around the center pixel (-2 in the example of FIG. 5) and the coefficient of the center pixel (+2 in the example of FIG. 5) The coefficients of each pixel are determined so that the sum becomes 0 (zero).

FIG. 6 is a diagram for explaining the emphasis processing of the n×n filter according to the present embodiment.

As shown in FIG. 6, by applying the n×n filter of FIG. 5 to the raised area, for example, black parts such as characters are emphasized. Note that when the n×n filter is applied to areas other than the raised area, characters and the like may be overemphasized. For this reason, it is desirable not to apply it to areas other than the floating area.

Next, an image that has undergone background color removal and filter processing according to this embodiment will be described with reference to FIGS. 7(A) and 7(B).

FIG. 7(A) is a diagram showing an image G1 according to a comparative example. FIG. 7(B) is a diagram showing an image G2 according to this embodiment.

In the image G1 shown in FIG. 7A, as described above, floating fog occurs due to the binding portion (spine portion) being lifted, and it can be seen that the resolution near the binding portion is reduced. Note that in the image G1, an area that does not include the halftone dot period is detected. Therefore, it is determined that the image G1 includes a raised area, and background color removal and filter processing are performed.

Image G2 shown in FIG. 7B is an image after background color removal has been performed and filter processing has been performed on the raised area. According to this image G2, it can be seen that the decrease in resolution near the binding portion is suppressed. That is, background color removal is performed on the entire image G1, and filter processing is further performed on the raised area of the image G1 using, for example, the n×n filter shown in FIG. 5 described above. . In this filter processing, black is emphasized, so characters, etc. in the raised area are emphasized, and the resolution is improved.

Here, the above filter processing may be performed by selectively using a plurality of n×n filters having different degrees of emphasis. The degree of emphasis of the n×n filter can be varied by setting the coefficient of the center pixel of the n×n filter to a different value.

Moreover, the distance between the two-page spread and the platen glass 23B becomes longer toward the center of the binding section in the floating area. For this reason, it is thought that the density of characters, etc. in the floating overlapping area becomes lower toward the center of the binding portion of the floating overlapping area. In this case, the filter processing unit 11E may selectively switch the plurality of n×n filters so that the degree of emphasis by filter processing becomes stronger in stages toward the center of the binding section in the floating area. good. For example, it is preferable to switch the n×n filter so that the coefficient of the central pixel of the n×n filter increases stepwise toward the center of the bound portion of the floating area.

Further, the timing for selectively switching the plurality of n×n filters may be, for example, when a change point at which the background color density value changes by more than a predetermined value is detected. As an example, this predetermined value is set to an appropriate value in the range of 1 to 10. Specifically, the filter processing unit 11E acquires the ground color density value in the raised area for each predetermined area in the line direction, and determines whether the difference in the ground color density value between the areas changes by more than a predetermined value. detect the change point.

Note that the functions of each part of the image processing device 10 (halftone period detection unit 11A, background color detection unit 11B, background color removal unit 11C, floating fog determination unit 11D, and filter processing unit 11E) are limited to software. Instead, it may be realized by dedicated hardware such as an ASIC (Application Specific Integrated Circuit).

Furthermore, in this embodiment, a reading method using the contact type image sensor 23A in which floating fog occurs noticeably has been exemplified and explained, but in this embodiment, floating fog occurs in a reading method using a CCD and an imaging lens. The same applies to floating head.

Next, with reference to FIG. 8, the operation of the image processing apparatus 10 according to this embodiment will be described.

FIG. 8 is a flowchart showing an example of the flow of processing by the image processing program 15A according to the present embodiment.

In step 100 of FIG. 8, the CPU 11 receives input of an image expressed as CMYK data, for example. Note that this input image is, for example, an image obtained by reading a double-page spread including a bound portion with the contact image sensor 23A, as shown in FIG. 3 described above.

In step 101, the CPU 11 determines whether or not a halftone dot period has been detected for the input image received in step 100. Specifically, it is determined whether or not an area that does not include a halftone dot period is detected in the line direction. If it is determined that an area that does not include a halftone dot period has been detected (in the case of a negative judgment), the process moves to step 102, and an area that does not include a halftone dot period is not detected, that is, only an area that includes a halftone dot period is detected. If it is determined that (in the case of an affirmative determination), the process moves to step 106.

In step 102, the CPU 11 detects the background color of the input image. At this time, the CPU 11 obtains a background color density value (for example, 0 or more and 255 or less) as a detection result of the background color.

In step 103, the CPU 11 removes the ground color from the input image. Specifically, the ground color density value obtained in step 102 is input, and the ground color is removed using a lookup table (LUT) for removing the ground color prepared in advance.

In step 104, the CPU 11 determines whether or not there is a raised area in the input image, which is represented as an area where the background color density value is smaller than the first threshold value and larger than the second threshold value. If it is determined that a floating area exists in the input image (in the case of a positive determination), the process proceeds to step 105, and if it is determined that a floating area does not exist in the input image (in the case of a negative determination), the process proceeds to step 106. . Note that, as described above, the first threshold value and the second threshold value used for determining the floating fog area are set based on the measured values obtained by measuring the density value indicating that floating fog has occurred in advance. .

In step 105, the CPU 11 performs filter processing on the raised area determined in step 104 to emphasize the raised area. Specifically, as an example, the n×n filter shown in FIG. 5 described above is used.

In step 106, the CPU 11 outputs the image and ends the series of processing by the image processing program 15A.

As described above, according to the present embodiment, the background color is removed from an image obtained by reading a double-page spread including a bound portion, and emphasis filter processing is performed on the raised overlapping area. This suppresses a decrease in resolution in the vicinity of the binding portion of the image.

Note that in each of the above embodiments, the processor refers to a processor in a broad sense, and includes a general-purpose processor (e.g., CPU: Central Processing Unit, etc.) and a dedicated processor (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

Further, the operation of the processor in each of the above embodiments may be performed not only by one processor, but also by a plurality of processors located at physically separate locations. Further, the order of each operation of the processor is not limited to the order described in each of the above embodiments, and may be changed as appropriate.

The image processing apparatus according to the embodiment has been described above as an example. The embodiment may be in the form of a program for causing a computer to execute the functions of each unit included in the image processing apparatus. Embodiments may be in the form of a computer readable storage medium storing this program.

In addition, the configuration of the image processing apparatus described in the above embodiment is merely an example, and may be changed according to the situation without departing from the spirit of the invention.

Furthermore, the process flow of the program described in the above embodiment is only an example, and unnecessary steps may be deleted, new steps may be added, or the processing order may be changed without departing from the main purpose. good.

Further, in the above embodiment, a case has been described in which the processing according to the embodiment is realized by a software configuration using a computer by executing a program, but the present invention is not limited to this. The embodiments may be realized by, for example, a hardware configuration or a combination of a hardware configuration and a software configuration.

10 Image processing device 11 CPU
11A Halftone period detection section 11B Ground color detection section 11C Ground color removal section 11D Floating fog determination section 11E Filter processing section 12 ROM
13 RAM
14 I/O
15 Storage unit 15A Image processing program 20 Image forming device 21 Display unit 22 Operation unit 23 Image reading unit 23A Contact image sensor 23B Platen glass 24 Image output unit 25 Communication unit

Claims (10)

Equipped with a processor,
The processor includes:
Detects the background color of the image obtained by reading a double-page spread including the binding,
removing the background color from the image;
An image processing device that performs filter processing to emphasize an area of the image in which the density value of the ground color is smaller than a first threshold value and larger than a second threshold value. The image processing device according to claim 1, wherein the filter processing is performed on the image after the background color is removed. The image processing device according to claim 1 or 2, wherein the processor detects the background color of the image when an area that does not include a halftone dot period is detected from the image. The image processing device according to claim 3, wherein the processor does not detect the background color of the image when only a region including a halftone dot period is detected from the image. The image processing device according to claim 3 or 4, wherein the halftone dot period is detected by frequency-analyzing the image. The image processing apparatus according to any one of claims 1 to 5, wherein the image is an image obtained by reading the double-page spread placed on a document table with a contact image sensor. The image processing device according to any one of claims 1 to 6, wherein the filter processing is performed selectively using a plurality of n×n (n is an odd number of 3 or more) filters with different emphasis degrees. . The processor selectively switches the plurality of n×n filters so that the degree of emphasis by the filter processing increases stepwise toward the center of the binding portion of the area. Image processing device. The image processing device according to claim 8, wherein the processor selectively switches the plurality of n×n filters when detecting a change point where the density value of the ground color changes by more than a predetermined value. Detects the background color of the image obtained by reading a double-page spread including the binding,
removing the background color from the image;
performing filter processing to emphasize an area in the image where the density value of the ground color is smaller than a first threshold value and larger than a second threshold value;
An image processing program that is executed by a computer.