JP3987850B2 - Image processing apparatus and image forming apparatus - Google Patents

Description

  The present invention provides an image processing apparatus that corrects image data read by an image sensor on one side of an original on which an image is formed only on one side, and a first that reads the one side of an original on which an image is formed only on one side. The present invention relates to an image forming apparatus having an image sensor and a second image sensor that reads the other side of the document simultaneously with reading the one side.

In image forming apparatuses such as facsimiles and copiers, the image data read by the image sensor is separated into various areas such as a character area, a graphic area, a halftone dot area, and a photographic area, and the attributes of the image data contained in each area It has been proposed to improve the quality of image data by performing image processing according to the above, and some have been put into practical use (for example, Patent Document 1).
JP 7-123266 A

  However, when there are a plurality of types of regions (for example, a character region and an image region) in one image data read by the image sensor, it is difficult to separate the various regions with high accuracy. If the area is misrecognized as another type of area such as a character area, appropriate image processing is not performed, and the quality of the image data deteriorates.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide an image processing apparatus and an image forming apparatus that perform separation of a character area and a non-character area with high accuracy.

  The image processing apparatus according to claim 1 is an image processing apparatus that corrects image data read by an image sensor on the one side of a document having an image formed on only one side, the read image data on the one side. First image storage means for storing a certain first image data for each pixel, and a second image data for storing a second image data for each pixel, which is a read-through image data on the other surface of the image formed on the one surface. An area that separates the first image data into a character area that is an area that includes character data and a non-character area that is an area that includes data other than characters, using two-image storage means and the second image data Separating means, and image correcting means for correcting the first image data by performing different image processing for each of the character area and the non-character area are provided.

  According to the above configuration, the first image data that is read image data on one side is stored for each pixel in the first image storage unit, and the second image storage unit stores the first image data on the other side of the image formed on the one side. Second image data which is read-out image data of the show-through of is stored for each pixel. Then, by using the second image data, the first image data is separated into a character region that includes character data and a non-character region that includes data other than characters by the region separation unit. Further, the image correction unit corrects the first image data by performing different image processing for each of the character area and the non-character area.

  Therefore, using the second image data which is the read-out image data of the show-through on the other side of the image formed on one side, the first image data is a character region including character data and data other than characters. Therefore, the character region and the non-character region are separated with high accuracy, and appropriate image processing is performed on each of the character region and the non-character region.

  The image processing apparatus according to claim 2, further comprising: a character pixel determination unit that determines whether the pixel is a character pixel based on a density difference from an adjacent pixel for each pixel, and the region separation unit includes the first pixel separation unit. The first image data is separated into a character area and a non-character area based on the determination result by the character pixel determination means for the image data and the second image data.

  According to this configuration, the character pixel determination unit determines whether each pixel is a character pixel based on the density difference between adjacent pixels. Further, the first image data is separated into the character region and the non-character region by the region separating unit based on the determination result by the character pixel determining unit for the first image data and the second image data.

  Therefore, the first image data is based on the determination result of whether or not the character pixel is determined by the character pixel determination means for the second image data that is the read image data of the show-through to the other side of the image formed on one side. Since the character area and the non-character area are separated, the character area and the non-character area are separated with higher accuracy.

  The image processing apparatus according to claim 3, wherein the region separation unit determines that the determination result by the character pixel determination unit of the first image data is a character pixel, and the determination by the character pixel determination unit of the second image data. A feature is that a pixel whose result is a character pixel is a character region.

  According to this configuration, the region separation unit causes the pixel whose determination result by the character pixel determination unit of the first image data is a character pixel and the determination result by the character pixel determination unit of the second image data is a character pixel. Since it is a character area, the character area and the non-character area are easily separated with high accuracy.

  The image forming apparatus according to claim 4, wherein a first image sensor that reads the one side of the document having an image formed on only one side thereof, and a second image that reads the other side of the document simultaneously with the reading of the one side. An image forming apparatus having a sensor, wherein the first image data and the image formed on the one surface are read by using the first image sensor and the second image sensor, respectively. Reading means for generating second image data that is read image data of show-through on the other side, first image storage means for storing the first image data for each pixel, and the second image data for each pixel Using the second image storage means to store and the second image data, the first image data is a non-text that is a character area that includes character data and a non-text area that includes data other than characters. An image forming apparatus comprising: an area separating unit that separates the first image data; and an image correcting unit that performs different image processing on the first image data for each of the character area and the non-character area. It is a device.

  According to this configuration, the reading unit uses the first image sensor and the second image sensor to apply the first image data that is read image data on one side and the image formed on the one side to the other side, respectively. Second image data, which is read-through image data of show-through, is generated, and the first image data and the second image data are stored in the first image storage unit and the second image storage unit for each pixel, respectively. Then, using the second image data, the first image data is separated into a character area that is an area that includes character data and a non-character area that is an area that includes data other than characters by the area separating means. . Further, the image correction unit corrects the first image data by performing different image processing for each of the character area and the non-character area.

  Therefore, using the second image data which is the read-out image data of the show-through on the other side of the image formed on one side, the first image data is a character region including character data and data other than characters. Therefore, the character region and the non-character region are separated with high accuracy, and appropriate image processing is performed on each of the character region and the non-character region.

  In addition, since the first image sensor reads one side of the document and the second image sensor reads the other side of the document simultaneously with the reading of the one side, image data is generated efficiently and the pixel position The first image data and the second image data that can be associated with each other with high accuracy are obtained.

  The image forming apparatus according to claim 5, further comprising: a character pixel determining unit that determines whether each pixel is a character pixel based on a density difference from an adjacent pixel, wherein the region separating unit includes the first pixel separating unit. The first image data is separated into a character area and a non-character area based on the determination result by the character pixel determination means for the image data and the second image data.

  According to this configuration, the character pixel determination unit determines whether each pixel is a character pixel based on the density difference between adjacent pixels. Further, the first image data is separated into the character region and the non-character region by the region separating unit based on the determination result by the character pixel determining unit for the first image data and the second image data.

  Therefore, the first image data is based on the determination result of whether or not the character pixel is determined by the character pixel determination means for the second image data that is the read image data of the show-through to the other side of the image formed on one side. Since the character area and the non-character area are separated, the character area and the non-character area are separated with higher accuracy.

  The image forming apparatus according to claim 6, wherein the region separation unit determines that the determination result by the character pixel determination unit of the first image data is a character pixel, and the determination result by the character pixel determination unit of the second image data. A pixel is a character region.

  According to this configuration, the region separation unit causes the pixel whose determination result by the character pixel determination unit of the first image data is a character pixel and the determination result by the character pixel determination unit of the second image data is a character pixel. Since it is a character area, the character area and the non-character area are easily separated with high accuracy.

  According to the first aspect of the present invention, the first image data includes character data using the second image data which is the read image data of the show-through to the other side of the image formed on the one side. Is separated into a character area and a non-character area, which is an area including data other than characters, so that the character area and the non-character area can be separated with high accuracy, and appropriate image processing can be performed on each. .

  According to the second and fifth aspects of the present invention, whether or not the image is a character pixel by the character pixel determination means for the second image data which is the read-out image data of the show-through on the other surface of the image formed on one surface. Since the first image data is separated into the character area and the non-character area based on the determination result, the character area and the non-character area can be separated with higher accuracy.

  According to the third and sixth aspects of the present invention, the determination result of the first image data by the character pixel determination unit is a character pixel, and the determination result of the second image data by the character pixel determination unit is a character pixel. Since the pixel is a character region, the character region and the non-character region can be separated easily and with high accuracy.

  According to the fourth aspect of the present invention, the second image data, which is the read-out image data of the show-through on the other side of the image formed on one side, is used in the region where the first image data includes character data. Since a character region and a non-character region that includes data other than characters are separated, the character region and the non-character region can be separated with high accuracy, and appropriate image processing can be performed on each.

  In addition, since the other side of the document is read simultaneously with the reading of one side, the image data can be generated efficiently and the first image data and the second image data that can associate the pixel positions with high accuracy are obtained. be able to.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a copying machine as an example of an image forming apparatus according to the present invention. The copying machine 1 is disposed above the document reading unit 5, the main unit 2, the stack tray 3 disposed on the left side of the main unit 2, the document reading unit 5 disposed on the top of the main unit 2. And a document feeding unit 6 provided. Also, on the front surface (front side of the drawing) of the copying machine 1, a start key 471 for accepting an input of a print execution instruction from a user, a numeric keypad 472 for accepting an input such as the number of copies, and various copying operation settings are input. A display 473 (touch panel) including a liquid crystal display (LCD) for displaying operation guide information and the like and various operation buttons for receiving input of various operation commands. An operation unit 47 is provided.

  The document reading unit 5 is a so-called scanner unit for reading an image of a document to obtain image data, and includes a contact glass 51 (platen glass) made of a transparent member such as glass on which the document is placed, a document reading slit. 52, a mirror unit 57 formed by integrating an exposure lamp 53, which is a light source for irradiating light on a document, and a mirror 54 to a mirror 56 that reflects light reflected from the document; A CCD image sensor 59 (corresponding to the first image sensor) composed of an image pickup device (CCD; Charge Coupled Device) that photoelectrically converts a light image formed by focusing the reflected light by the lens group 58 and obtaining image data. It has.

  The mirror unit 57 is configured to be reciprocally movable along the contact glass 51 with a predetermined interval by a drive unit (not shown). The mirror unit 57 emits light by the exposure lamp 53 in accordance with a control signal from the control unit 10 described later. While irradiating, one side (herein referred to as the front surface) of the document placed on the contact glass 51 is scanned, and a scanned image of the document is formed on the CCD image sensor 59 via the lens group 58. Further, the mirror unit 57 is moved to a position facing the document reading slit 52 when reading the document fed by the document feeding unit 6, and transports the document by the document feeding unit 6 through the document reading slit 52. The document image is read in synchronization with the operation, and the read image data (first image data) is output to the control unit 10.

  The document feeding unit 6 includes a document placing unit 61 for placing a document, a document discharging unit 62 for discharging a document after image reading, and a document placed on the document placing unit 61. A sheet feed roller 63, a registration roller 64, a sheet discharge roller 65, and the like are provided for sequentially feeding the sheets one by one to transport them to a position facing the document reading slit 52 and discharging them to the document discharge section 62. Further, the document feeding unit 6 has a contact image sensor (CIS) 67 (corresponding to a second image sensor) at a position facing the upper surface of the document reading unit 5 below the document feeding unit 6. It has.

  The contact-type image sensor 67 reads an image on the other side (here, referred to as the back side) of the document conveyed on the contact glass 51 and outputs the read image data (second image data) to the control unit 10. It is. Similarly to the CCD image sensor 59, the contact image sensor 67 includes a light source (not shown), an image pickup device such as a CCD, and an optical system. However, unlike the CCD image sensor 59, the contact image sensor 67 is used in a state where the position is fixed without being scanned.

  The CCD image sensor 59 and the contact image sensor 67 enable simultaneous reading of both sides of the image of the document conveyed by the document feeding unit 6. When an image is formed only on one side (here, the front side) of the document, the image data (first image data) on the front side is read by the CCD image sensor 59 and the front side is read by the contact type image sensor 67. The image data (second image data) of the show-through to the other side (back side) of the image formed in the above is read.

  The main body 2 includes a plurality of paper feed cassettes 461 that store recording papers of different sizes, a paper feed roller 462 that feeds the recording papers one by one from the paper feed cassette 461 and transports them to the recording unit 40, and a paper feed cassette And a recording unit 40 that forms an image on the recording paper conveyed from 461.

  The recording unit 40 outputs a laser beam based on image data read by the CCD image sensor 59 and the contact image sensor 67 to expose the photosensitive drum 43, and a toner image on the photosensitive drum 43. An image forming unit 44 for forming the toner image, a transfer unit 41 for transferring the toner image on the photosensitive drum 43 to the recording paper, and a fixing unit for heating the recording paper to which the toner image is transferred and fixing the toner image on the recording paper. 45 and a paper transport device 46 that transports the recording paper by a transport roller or the like provided in the paper transport path in the recording unit 40 and discharges the recording paper to the stack tray 3 or the discharge tray 48.

  FIG. 2 is a block diagram showing an example of the functional configuration of the copying machine 1 shown in FIG. The copying machine 1 includes a document reading unit 5, a document feeding unit 6, a recording unit 40, an operation unit 47, an image memory 7, an image processing unit 8 (corresponding to a part of image correction means), an HDD (Hard Disk). (Drive) 9 and a control unit 10.

  The image memory 7 is a first image data storage unit 71 (first image data storage unit 71) that stores image data of a document read by the CCD image sensor 59 of the document reading unit 5 and the contact image sensor 67 of the document feeding unit 6 for each pixel. Pixel corresponding to a first image data storage unit), a second image data storage unit 72 (corresponding to a second image data storage unit), and corrected image data obtained by performing predetermined image processing on the first image data. And a corrected image data storage unit 73 that stores the data every time.

  The image processing unit 8 is used for correcting the edge enhancement processing unit 81 and the binarization processing unit 82 used for correcting image data composed of characters, and image data other than characters (for example, halftone dot data, photo data). The smoothing processing unit 83 and the dither processing unit 84 are provided.

  The HDD 9 is a storage device that stores image data read by the CCD image sensor 59 or the contact image sensor 67 and an output format set in the image data. Note that image data and the like stored in the HDD 9 are not only used in the copying machine 1 but also output to a personal computer or the like via a network I / F unit (not shown) as necessary.

  The control unit 10 is a ROM (Read Only Memory) that stores a control program of the copier 1, a RAM (Random Access Memory) that temporarily stores data, a CPU (Central Processing) that reads and executes the control program from the ROM. Unit) (that is, a computer), and control of the entire apparatus according to instruction information received by the operation unit 47 or the like, or detection signals from sensors provided in various places of the apparatus. The process which performs is performed. The control unit 10 includes a reading instruction unit 101, an edge determination unit 102 (corresponding to a character pixel determination unit), a region separation unit 103 (corresponding to a region separation unit), and an image correction unit 104 (corresponding to a part of the image correction unit). And an image formation instructing unit 105.

  The reading instructing unit 101 causes the CCD image sensor 59 to read the surface of the document, generates first image image data, and stores the generated first image data in the first image data storage unit 71. At the same time, the contact-type image sensor 67 reads the back side of the document to generate second image image data, and the generated second image data is stored in the second image data storage unit 72. . However, here, it is assumed that an image such as a character and a photograph is formed on only one side of the document. That is, the second image image data is image data of show-through on the back surface of the image formed on the front surface.

  For each of the first image data and the second image data, the edge determination unit 102 obtains a density difference from a peripheral pixel (eight neighboring pixels described later) for each pixel, and compares the density difference with a preset threshold value. When at least one peripheral pixel is equal to or greater than the threshold, it is determined that the character pixel (also referred to as an edge).

  FIG. 3 is a diagram illustrating an example of a method for determining whether or not a character pixel. (A) is a general view and (b) is an enlarged view. As shown in (a), the first image data and the second image data are each composed of pixels arranged in a grid, and the pixels Pi, j are i-th row and j-th column (i = 1 to M, j = 1 to N; M = 1024, N = 2048). When the pixel Pi, j is selected as the target pixel, as shown in (b), the peripheral pixels are eight pixels around the pixel Pi, j. Then, a density difference ΔDk (k = 1 to 8) with respect to the target pixel Pi, j is calculated for each of the eight peripheral pixels. Then, it is determined that the pixel is a character pixel when at least one of the eight density differences ΔDk is equal to or greater than a threshold value.

  Returning again to FIG. 2, the functional configuration of the copying machine 1 will be described. The region separation unit 103 separates the first image data into a character region and a non-character region based on the determination result by the edge determination unit 102 for the first image data and the second image data. Specifically, the region separation unit 103 determines pixels whose determination result by the region separation unit 103 of the first image data is a character pixel and whose determination result by the region separation unit 103 of the second image data is a character pixel. A character area is used, and an area other than the character area is a non-character area.

  The image correction unit 104 uses the image processing unit 8 to perform edge enhancement processing and binarization processing on the character region of the first image data, and on the non-character region of the first image data. Smoothing processing and dither processing are performed, and the corrected image data subjected to each processing is stored in the corrected image data storage unit 73.

  The image formation instructing unit 105 reads the corrected image data from the corrected image data storage unit 73 and forms an image corresponding to the corrected image data on the recording paper using the recording unit 40.

  FIG. 4 is a flowchart showing an example of the operation of the copying machine 1. First, the reading instruction unit 101 reads the surface of the document using the CCD image sensor 59 to generate first image data, which is stored in the first image data storage unit 71 (step S101). Further, the reading instruction unit 101 reads the back side of the document using the contact image sensor 67 to generate second image data, which is stored in the second image data storage unit 72 (step S103). Then, the edge determination unit 102 determines whether each pixel of the first image data is a character pixel (step S105). Then, the area separation unit 103 separates the first image data into the character area CA and the non-character area NCA based on whether or not each pixel of the first image data is a character pixel (step S107).

  Next, the edge determination unit 102 determines whether each pixel of the second image data is a character pixel (step S109). Then, for each pixel determined to be in the character area CA in step S107 by the area separation unit 103, it is determined whether the determination result in step S109 is also a character pixel (edge) for the second image data. (Step S111). If it is determined that the pixel is not a character pixel (NO in step S111), the region separation unit 103 changes the pixel from the character region CA to the non-character region NCA (step S113).

  When it is determined in step S107 that all the pixels determined to be in the character area CA are character pixels (YES in step S111), or when the process in step S113 is completed, the image correction unit 104 performs processing. The first image data is subjected to image processing to generate corrected image data, which is stored in the corrected image data storage unit 73 (step S115). Next, an image corresponding to the corrected image data is formed on the recording paper by the image formation instruction unit 105 (step S117), and the process is terminated.

  FIG. 5 is a detailed flowchart showing an example of the image correction process performed in step S115 of the flowchart shown in FIG. The following processing is all performed by the image correction unit 104. First, it is determined whether or not the data is in the character area CA (step S201). If it is determined that the data is in the character area CA (YES in step S201), edge enhancement processing is performed using the edge enhancement processing unit 81 (step S203). Then, binarization processing is performed using the binarization processing unit 82 (step S205), and the process is returned.

  If it is determined in step S201 that the data is not in the character area CA (data in the non-character area NCA) (NO in step S201), smoothing processing is performed using the smoothing processing unit 83. (Step S207). Then, a dither process is performed using the dither processing unit 84 (step S209), and the process is returned.

  FIG. 6 is a diagram illustrating an example of the first image data and the second image data. (A) is the 1st image P1 which shows 1st image data, (b) is the 2nd image P2 which shows 2nd image data. As shown to (a), the 1st image P1 has character area A1 in which the character was formed in the left side of a figure, and photograph area A2 in which the photograph was formed. As shown in (b), the second image P2 is an image in which the first image P1 is shown through, and the character area A3 in which the character area A1 is shown in on the right side of the figure and the photograph area A2 in show-through. And a photo area A4.

  Here, the pixels included in the photographic area A2 of the first image P1 include pixels that are determined to be character pixels when the density difference ΔDk is equal to or greater than the threshold value, but are included in the photographic area A4 of the second image P2. For all the pixels, the density difference ΔDk is less than the threshold value, and no pixel is determined to be a character pixel. Therefore, it is determined with high accuracy that the photo area A2 is a non-character area using whether or not each pixel of the second image P2 is a character pixel.

  In this way, by using the second image data which is the read-out image data of the show-through on the back surface of the image formed on the front surface, the first image data is a character area including character data and a character area other than characters. Since it is separated into a non-character area that is an area including data, the character area and the non-character area can be separated with high accuracy, and appropriate image processing is performed on each.

  Further, the front surface of the document is read by the CCD image sensor 59, and the back surface of the document is read simultaneously with the reading of the front surface by the contact image sensor 67, so that image data is efficiently generated and the pixel position is supported. First image data and second image data that can be attached with high accuracy are obtained.

  Further, the first image data is a character region based on a determination result of whether or not the second image data, which is read image data of show-through on the back surface of the image formed on the front surface, is a character pixel. Therefore, the character area and the non-character area are separated with higher accuracy.

  In addition, by the region separation unit 103, pixels in which the determination result of the first image data by the edge determination unit 102 is a character pixel and the determination result of the second image data by the edge determination unit 102 is a character pixel are character regions. Therefore, the character area and the non-character area are easily separated with high accuracy.

  In addition, this invention can take the following aspects.

  (A) In the present embodiment, the case where the image forming apparatus is the copying machine 1 has been described. However, another type of image forming apparatus (for example, a facsimile) may be used. For example, when the image forming apparatus is a facsimile, it is possible to determine with high accuracy whether or not it is a character area of an original. Therefore, the effect of applying text character data by applying OCR (Optical Character Recognition) to the character area. Is increased.

  (B) In this embodiment, the case where the copying machine 1 includes two image sensors has been described. However, the first image data and the second image data may be formed separately by including one image sensor. . In this case, the image processing of the present invention can be performed using a copying machine including one image sensor.

  (C) In the present embodiment, the case where the region separation unit 103 separates the first image data into the character region and the non-character region has been described. However, the non-character region is further divided into a plurality of regions (halftone region, photographic region). Etc.).

  (D) In the present embodiment, the case where the image correction unit 104 performs the edge enhancement process and the binarization process on the character region has been described. However, the image correction unit 104 performs at least one of the edge enhancement process and the binarization process. However, it may be a form in which other processing is performed.

  (E) In the present embodiment, the case where the image correction unit 104 performs the smoothing process and the dither process on the non-character area has been described. However, at least one of the smoothing process and the dither process may be performed. Further, another form may be applied.

  (F) In the present embodiment, the case where the edge determination unit 102 determines whether or not the character pixel is a character pixel using the density difference ΔDk between the peripheral pixel of interest and the eight pixels has been described. It is also possible to determine whether or not the pixel is a character pixel by using the difference in density.

1 is a cross-sectional view of a copying machine as an example of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating an example of a functional configuration of the copier illustrated in FIG. 1. It is a figure explaining an example of the determination method of whether it is a character pixel. 6 is a flowchart illustrating an example of operation of the copying machine. 5 is a detailed flowchart illustrating an example of an image correction process performed in step S115 of the flowchart illustrated in FIG. 4. It is a figure which shows an example of 1st image data and 2nd image data.

Explanation of symbols

1 Copying machine (image forming device)
5 Document reader 59 CCD image sensor (first image sensor)
6 Document Feeding Section 67 Contact Image Sensor (Second Image Sensor)
7 Image memory 71 First image storage unit (first image storage means)
72 Second image storage unit (second image storage means)
8 Image processing unit (part of image correction means)
40 recording section 47 operation section (operation means)
DESCRIPTION OF SYMBOLS 10 Control part 101 Reading instruction | indication part 102 Edge determination part (character pixel determination means)
103 Region separation unit (region separation means)
104 Image correction unit (part of image correction means)
105 Image formation instruction unit

Claims (6)

An image processing apparatus for correcting image data read by an image sensor on one side of an original on which an image is formed only on one side,
First image storage means for storing first image data, which is read image data of the one side, for each pixel;
Second image storage means for storing, for each pixel, second image data which is read image data of show-through to the other side of the image formed on the one side;
Using the second image data, an area separating means for separating the first image data into a character area that is an area including character data and a non-character area that is an area including data other than characters;
An image processing apparatus, comprising: an image correcting unit that corrects the first image data by performing different image processing for each of the character region and the non-character region. Character pixel determination means for determining whether a pixel is a character pixel based on the density difference between adjacent pixels for each pixel,
The region separation unit separates the first image data into a character region and a non-character region based on a determination result by the character pixel determination unit for the first image data and the second image data. The image processing apparatus according to 1.   The region separation means defines a pixel in which a determination result by the character pixel determination unit of the first image data is a character pixel and a determination result by the character pixel determination unit of the second image data is a character pixel as a character region. The image processing apparatus according to claim 2, wherein: An image forming apparatus comprising: a first image sensor that reads one side of a document on which an image is formed only on one side; and a second image sensor that reads the other side of the document simultaneously with reading the one side,
Using the first image sensor and the second image sensor, respectively, the first image data which is the read image data of the one surface and the read image data of the show-through to the other surface of the image formed on the one surface. Reading means for generating certain second image data;
First image storage means for storing the first image data for each pixel;
Second image storage means for storing the second image data for each pixel;
Using the second image data, an area separating means for separating the first image data into a character area that is an area including character data and a non-character area that is an area including data other than characters;
An image forming apparatus, comprising: an image correcting unit configured to correct the first image data by performing different image processing for each of the character region and the non-character region. Character pixel determination means for determining whether a pixel is a character pixel based on the density difference between adjacent pixels for each pixel,
The region separation unit separates the first image data into a character region and a non-character region based on a determination result by the character pixel determination unit for the first image data and the second image data. 5. The image forming apparatus according to 4.   The region separation means defines a pixel in which a determination result by the character pixel determination unit of the first image data is a character pixel and a determination result by the character pixel determination unit of the second image data is a character pixel as a character region. The image forming apparatus according to claim 5, wherein:

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