JP2011045069A - Image processor and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor that performs MTF correction. <P>SOLUTION: The image processor includes a setting part, calculation part, and correction processing part. The setting part sets a correction value to be used in MTF correction of image data generated by a scanner in each of a plurality of block areas dividing an image area. The calculation part uses the correction value of the block area including a pixel of interest and the correction value of the block area adjacent to the block area including the pixel of interest, to calculate the correction value in all the pixels included in the block areas. The correction processing part uses the correction value of each pixel calculated by the calculation part to perform MTF correction of the image data. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that sets a correction value for performing MTF correction processing on image data generated by a scanner.

  The scanner generates image data corresponding to the original by irradiating the original with illumination light and receiving light reflected by the original. The image forming apparatus receives image data from the scanner and forms an image on a sheet.

  When acquiring image data using a scanner, MTF (Modulation Transfer Function) values may vary within the image plane due to the inherent characteristics of the scanner. If the MTF value varies, the resolving power of the image decreases or the contrast becomes uneven.

  The image processing apparatus according to the embodiment includes a setting unit, a calculation unit, and a correction processing unit. The setting unit sets a correction value used in the MTF correction processing of the image data generated by the scanner in each of the plurality of block areas into which the image area is divided. The calculation unit calculates a correction value for all the pixels included in each block region, using the correction value for the block region including the target pixel and the correction value for the block region adjacent to the block region including the target pixel. The correction processing unit performs MTF correction processing of the image data using the correction value of each pixel calculated by the calculation unit.

  The image processing method according to the embodiment sets a correction value used in the MTF correction processing of the image data generated by the scanner in each of a plurality of block areas into which the image area is divided, and the correction value of the block area including the target pixel And the correction values of all the pixels included in each block region using the correction value of the block region adjacent to the block region including the target pixel, and the image data using the calculated correction value of each pixel. The MTF correction process is performed.

1 is a diagram illustrating an outline of an image forming apparatus. It is a figure which shows the outline of a scanner. It is a block diagram which shows the circuit structure which performs an image process. It is a block diagram which shows the structure of a system part. It is a block diagram which shows the internal structure of a 1st process part. It is a flowchart which shows the process which calculates a MTF correction value. It is a figure which shows the chart for calculating the MTF value of the main scanning direction. It is a figure which shows the chart for calculating the MTF value of a subscanning direction. It is a figure which shows an image when the dispersion | variation has generate | occur | produced in the MTF value. It is a figure which shows the state which divided | segmented the image into the several block. It is a flowchart which shows the process which calculates the MTF average value of each block. It is a figure which shows the display content of the operation panel when changing a block size. It is the schematic when preserve | saving only the MTF correction value of a some block. It is the schematic when performing MTF correction processing with respect to each color data of RGB. It is the schematic when performing MTF correction processing with respect to each color data of RGB. It is a flowchart which shows the correction process of MTF. It is a figure which shows the display content of the operation panel when performing the correction process of MTF. It is a figure explaining the method of calculating the MTF correction value of each pixel. It is a figure which shows the correspondence of a MTF correction value and the parameter of a MTF correction process. It is a figure which shows a MTF correction value table and a parameter switching table.

  An image forming apparatus (MFP: Multi Function Peripheral) will be described with reference to FIG. FIG. 1 is a front view showing an outline of the image forming apparatus.

  The image forming apparatus 100 includes a plurality of paper feed cassettes 101, and each paper feed cassette 101 accommodates a plurality of sheets. A plurality of sheets stored in each sheet feeding cassette 101 passes through a sheet conveyance path and is supplied to the image forming unit 102. The image forming unit 102 forms a developer image on a sheet based on the image data. The image data includes, for example, image data transmitted from an external device (for example, a personal computer) to the image forming apparatus 100 and image data generated by a reading operation of the scanner 103.

  The scanner 103 generates image data by scanning images of a paper document and a book document. FIG. 1 shows a part of the scanner 103. Above the scanner 103 is an apparatus (ADF: Auto Document Feeder) 104 for automatically feeding a document to the scanner 103.

  Above the image forming apparatus 100 is an operation panel 105 for inputting various information to the image forming apparatus 100. The operation panel 105 can be composed of, for example, a button switch or a liquid crystal panel.

  The image forming unit 102 forms an electrostatic latent image corresponding to the image data on the photosensitive surface of the photoreceptor, and then supplies a developer to form a developer image. The image forming unit 102 transfers the developer image formed on the surface of the photoreceptor to a sheet. By bringing the paper into contact with the surface of the photoconductor, the developer image can be transferred onto the paper. The developer image on the photoreceptor can be transferred from the intermediate transfer belt to a sheet after being transferred to the intermediate transfer belt.

  The developer image transferred to the paper is fixed on the paper by heat treatment. The sheet on which the developer image is fixed passes through the sheet conveyance path and moves to the sheet discharge space S. In the paper discharge space S, there is a paper discharge tray 106 for stacking sheets.

  In the configuration shown in FIG. 1, a scanner 103 is provided in an image forming apparatus 100 as a digital multifunction peripheral. The present invention can also be applied to a case in which a scanner is provided in an image forming apparatus as a digital copying machine, or a product is configured with only a scanner. The present embodiment can also be applied to an image forming apparatus that forms an image by ejecting ink.

  The configuration of the scanner 103 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the scanner 103 along the sub-scanning direction.

  The document 12 is on the upper surface of the platen glass 11, and the reading surface of the document 12 faces the upper surface of the platen glass 11. The platen cover 13 rotates with respect to the main body of the scanner 103 and opens the upper surface of the platen glass 11 or closes the upper surface of the platen glass 11. When the platen cover 13 is closed, the document 12 is pressed against the platen glass 11. The platen cover 13 constitutes a part of the ADF 104.

  The illumination unit 20 irradiates the original 12 with illumination light. The illumination unit 20 extends in a direction (main scanning direction) orthogonal to the paper surface of FIG. 2, and linear illumination light extending in the longitudinal direction of the illumination unit 20 is emitted from the illumination unit 20. Linear illumination light is applied to an image area of one line extending in the main scanning direction in the document 12.

  The illumination light from the illumination unit 20 is reflected by the document 12. The reflected light from the document 12 is reflected by the folding mirrors 14 a, 14 b and 14 c and travels toward the imaging lens 15. The imaging lens 15 condenses the light from the folding mirror 14 c and forms an image on the image sensor 16. The image sensor 16 has a plurality of light receiving elements 16a arranged in a direction orthogonal to the paper surface of FIG. 2, and the plurality of light receiving elements 16a are arranged in R (Red), G (Green), and B (Blue). Correspondingly provided. The plurality of light receiving elements 16a are arranged corresponding to the linear illumination light, and receive the linear illumination light. Each light receiving element 16a outputs an electric signal corresponding to the amount of incident light by photoelectric conversion. As the image sensor 16, for example, a CCD sensor can be used.

  Reflected light from the document 12 is incident on the plurality of light receiving elements 16a, so that an image area for one line extending in the main scanning direction can be read from the document 12.

  The first carriage 31 supports the illumination unit 20 and the folding mirror 14a and can move in the sub-scanning direction. The second carriage 32 supports the folding mirrors 14b and 14c and can move in the sub-scanning direction. The first carriage 31 and the second carriage 32 move relative to each other in the sub-scanning direction to maintain a constant optical path length from the surface of the document 12 (illumination light reflecting surface) to the image formation surface of the image sensor 16. .

  By moving the first carriage 31 and the second carriage 32, the illumination light from the illumination unit 20 can be scanned in the sub-scanning direction. While moving the first carriage 31 and the second carriage 32 in the sub-scanning direction, the image area for one line extending in the main scanning direction in the document 12 is sequentially read. The entire surface of the document 12 can be read.

  FIG. 3 shows a circuit configuration for performing image processing on the image data generated by the scanner 103. The scanner 103 outputs the generated image data to the image processing unit 40. The image processing unit 40 includes a first processing unit 41 and a second processing unit 42. The first processing unit 41 performs image processing of image data. Examples of image processing include image rotation, filtering, color conversion, halftone processing, and gamma correction. The first processing unit 41 outputs the processed data to the page memory 51. The second processing unit 42 receives data from the page memory 51 and converts the image data into a printable format. The second processing unit 42 outputs the converted data to the image forming unit 102.

  As shown in FIG. 4, the image processing unit 40 communicates with the system unit 50. The system unit 50 includes a page memory 51, a page memory controller 52, an HDD (Hard Disk Drive) 53, and a system controller 54. The page memory controller 52 stores data from the image processing unit 40 in the page memory 51 and outputs data in the page memory 51 to the image processing unit 40. The system controller 54 controls the operation of the image forming apparatus 100.

  FIG. 5 shows an internal configuration of the first processing unit 41. Image data from the scanner 103 is input to the average value calculation unit 411 or the correction processing unit 416. The average value calculation unit 411 calculates the average value of the MTF and outputs the calculation result to the bus select circuit (SEL) 412. The correction processing unit 416 performs MTF correction processing on the image data, and outputs the processed data to the bus select circuit (SEL) 412. The bus select circuit (SEL) 412 outputs the data from the average value calculation unit 411 or the correction processing unit 416 to the data processing unit 417. The data processing unit 417 performs predetermined processing on the input data.

  The correction value setting unit 413 sets an MTF correction value in a block to be described later. The MTF correction value is set in each pixel of RGB. The correction value calculation unit 414 uses the MTF correction value from the correction value setting unit 413 to calculate the MTF correction value for each pixel in the image. The table generation unit 415 converts the MTF correction value of each pixel into a parameter for MTF correction processing, and generates a table indicating the correspondence between each pixel and the parameter. The table generation unit 415 outputs the generated table to the correction processing unit 416. The correction processing unit 416 performs MTF correction processing using the table from the table generation unit 415. An example of the MTF correction process is a filter process.

  A process for correcting variation in MTF values will be described. There are a process for calculating the MTF correction value and a process for correcting the MTF value of the image data (image data of the document 12) generated by the scanner 103 based on the calculated MTF correction value.

  The process for calculating the MTF correction value will be described with reference to the flowchart shown in FIG.

  The scanner 103 performs scan processing on the correction charts M1 and M2 shown in FIGS. 7A and 7B (ACT 101). The image processing unit 40 calculates the MTF value in the image data from the scanner 103 (ACT 102).

  The correction chart M1 shown in FIG. 7A is used to calculate the MTF value in the main scanning direction, and the correction chart M2 shown in FIG. 7B is used to calculate the MTF value in the sub scanning direction. As the correction charts M1 and M2, A3 size paper corresponding to the maximum area that can be scanned by the scanner 103 can be used.

  If the correction chart M1 shown in FIG. 7A is used, for example, variation information of the MTF value due to the intrinsic characteristic of the lens of the image sensor (CCD sensor) 16 can be acquired. If the correction chart M2 shown in FIG. 7B is used, for example, variation information of MTF values resulting from the operation of the carriages 31 and 32 can be acquired. FIG. 8 shows an image I generated by the scanner 103 and having a variation in MTF values.

  The image I obtained by the scanning process is divided into a plurality of blocks N as shown in FIG. The plurality of blocks N are arranged in a matrix. One block N can be composed of, for example, 100 × 100 pixels. The average value calculation unit 411 calculates the average value (referred to as MTF average value) of the MTFs of the pixels included in each block N (ACT 103). If one block N is 100 × 100 pixels, an average value of MTFs of 10,000 pixels is calculated.

  Although the average value calculation unit 411 in the image forming apparatus 100 calculates the MTF average value, the MTF average value can be calculated using an external device different from the image forming apparatus 100. The MTF value in each block N may be used instead of the MTF average value. For example, instead of the MTF average value, the MTF value that exists most in each block N can be used.

  The average value calculation unit 411 can change the size of the block N based on the MTF average value of each block N. Processing for changing the size of the block N will be described with reference to FIG.

  In FIG. 10, the average value calculation unit 411 specifies the maximum value and the minimum value from the MTF average values of all the blocks N (ACT 201). The average value calculation unit 411 determines whether or not the difference between the maximum value and the minimum value (absolute value) is smaller than the threshold (ACT 202). The threshold value can be set as appropriate. As the threshold value is decreased, the variation in the MTF average value can be reduced.

  When the difference between the maximum value and the minimum value is larger than the threshold value, the process of changing the size of the block N is ended. When the difference between the maximum value and the minimum value is smaller than the threshold value, the average value calculation unit 411 increases the size of the block N (ACT 203). For example, when one block N is composed of 100 × 100 pixels, the average value calculation unit 411 can expand the block N to 200 × 200 pixels.

  The magnification for expanding the size of the block N can be set as appropriate. For example, the magnification can be a positive integer. As shown in FIG. 11, the operation panel (user interface) 105 can display information for changing the size of the block N. The operation panel 105 displays four options for changing the size of the block N. The user can set the size of the block N by operating the operation panel 105. The operation panel 105 is a so-called touch panel.

  In FIG. 11, the operation panel 105 displays the image division state by the block N. When the user selects the size of the block N, the operation panel 105 displays a state in which the image is divided based on the selected block N. The user can check the display state of the operation panel 105 and check the division state of the image. In the example illustrated in FIG. 11, the size of the block N is determined from four options, but an operation unit for arbitrarily changing the size of the block N can be provided.

  The average value calculation unit 411 can change the size of the block N based on whether or not the MTF average value of each block N varies. A criterion as to whether or not the MTF average value varies can be set as appropriate. If the variation in the MTF average value is within the allowable range, the average value calculation unit 411 can increase the size of the block N. As the allowable range, for example, the standard deviation of MTF average values in all the blocks N can be used.

  If the variation in the MTF average value is out of the allowable range, the average value calculation unit 411 can reduce the size of the block N. After reducing the size of the block N, the average value calculation unit 411 can determine whether or not the variation in the MTF average value in the reduced block N is within an allowable range. If the variation in the average MTF value is within the allowable range, the size of the block N is determined to be the size after reduction. If the variation in the MTF average value is out of the allowable range, the average value calculation unit 411 can further reduce the size of the block N.

  In FIG. 10, the average value calculation unit 411 calculates the MTF average value of each block N after changing (enlarging) the size of the block N (ACT 204). The average value calculation unit 411 determines the size of the block N by repeating ACT201 to ACT203 using the calculated MTF average value.

  The first processing unit 41 outputs information about the finally determined block N and the MTF average value of each block N to the system unit 50. The page memory controller 52 temporarily stores information on the MTF average value of each block N in the page memory 51. The system controller 54 stores information on the MTF average value of each block N in the HDD 53. The page memory 51 and the HDD 53 store the MTF average value of each block N and the position information of each block N in association with each other. The position information of the block N indicates the position of the block N in the image.

  If the size of the block N is increased, the number of blocks N existing in the image can be reduced. If the number of blocks N is reduced, the number of MTF values stored in the HDD 53 or the like can be reduced, and the storage capacity of the HDD 53 or the like can be reduced. As will be described later, when calculating the MTF correction value in each block N, the time for calculating the MTF correction value can be shortened by reducing the number of blocks N.

  In FIG. 6, the system controller 54 determines the MTF target value (ACT 104). The MTF target value is a value after the MTF value is corrected by the MTF correction process, and is an MTF value corresponding to a desired resolution. The system controller 54 can determine the MTF target value by referring to the MTF average value (stored in the HDD 53) in all the blocks N. For example, as the MTF target value, a maximum value of MTF average values or a value obtained by averaging all MTF average values can be used. Further, by conducting an experiment in advance, it is possible to identify an MTF value from which a high-quality image can be easily obtained, and to set this MTF value as the MTF target value.

The system controller 54 calculates a correction value (referred to as an MTF correction value) for correcting the MTF average value of each block N based on the MTF target value (ACT 105). The MTF correction value is a value for changing the MTF average value of each block N to the MTF target value. As shown in the following formula (1), the difference between the MTF average value A _MTF and the MTF target value T _{MTF of} each block N is the MTF correction value C.

C = T _MTF -A _MTF (1)

  The system controller 54 stores the MTF correction value of each block N in the HDD 53 (ACT 106). The HDD 53 stores the MTF correction value of each block N and the position information of each block N in association with each other. The system controller 54 can store the MTF correction values of all the blocks N in the HDD 53. Further, as shown in FIG. 12, the system controller 54 can store only MTF correction values of some blocks N in the HDD 53.

The MTF correction value is stored corresponding to each color of RGB. In the same block N, when at least two MTF correction values among RGB MTF correction values (three MTF correction values) are greatly different, the MTF correction values can be corrected. As shown in FIG. 13, when the RGB MTF correction values (C _R1 , C _G1 , C _B1 ) are different from each other, the RGB data are corrected based on the MTF correction values (C _R1 , C _G1 , C _B1 ). Then, the RGB balance may be lost. In FIG. 13, the blue (B) MTF correction value C _B1 is the largest, and the green (G) MTF correction value C _G1 is the smallest. If the balance of RGB is lost, the color tone is lowered, and a preferable image may not be obtained.

  When the difference in MTF correction value between the RGB colors is larger than the threshold value, the MTF correction value can be corrected. The threshold value can be set as appropriate. For example, the threshold value is set in consideration of the RGB balance when the MTF correction process is performed without correcting the MTF correction value and the RGB balance when the MTF correction process is performed after correcting the MTF correction value. can do. Even if there is a difference in MTF correction values between the RGB colors, the MTF correction values can be used without correction if the RGB balance is not lost.

The correction of the MTF correction value can be performed as appropriate. It is sufficient that the RGB balance is not lost by the MTF correction processing. For example, when the RGB MTF correction values are different from each other, as shown in FIG. 14, the MTF correction values (C _R2 , C _G2 , and C _B2 ) of each color of RGB can be aligned with the smallest MTF correction value C _R1. . The RGB MTF correction values (three MTF correction values) can be set to any one of the MTF correction values. If the maximum MTF correction value is set, MTF correction processing may be performed excessively, which is not preferable. If the minimum MTF correction value is used, the MTF correction process can be performed while adjusting the RGB balance.

  By storing only the MTF correction values of some blocks N in the HDD 53, the storage capacity of the HDD 53 can be reduced, and the processing speed when storing the MTF correction values can be improved. When only the MTF correction values of some blocks N are stored in the HDD 53, the MTF correction processing is performed only on some blocks N. By performing the MTF correction process on only some of the blocks N, the time for the MTF correction process can be reduced.

  For example, only the MTF correction value indicating a value higher than the threshold value can be stored in the HDD 53. The threshold can be set as appropriate. The larger the MTF correction value, the higher the need to perform the MTF correction process, and the smaller the MTF correction value, the more the MTF correction process may not be performed. As the threshold value decreases, the number of MTF correction values stored in the HDD 53 increases. Based on these points, a threshold can be set.

  By repeatedly calculating the MTF correction value at an arbitrary timing, it is possible to cope with a change in the characteristics of the scanner 103 accompanying a secular change. An MTF correction value suitable for the current characteristics of the scanner 103 can be calculated.

  The MTF correction process will be described with reference to the flowchart shown in FIG. The MTF correction process is performed after the scanner 103 performs a scan process to generate image data. As shown in FIG. 16, the operation panel 105 of the image forming apparatus 100 can display selection information as to whether or not to perform MTF correction processing. The user can execute an MTF correction process by operating the operation panel 105.

  The first processing unit 41 performs MTF correction processing on the image data generated by the scanner 103. The system controller 54 sets the MTF correction value stored in the HDD 53 in the correction value setting unit 413 (ACT 301). In response to an instruction from the user, the scanner 103 starts a scanning process and generates image data corresponding to the document (ACT 302). The correction value calculation unit 414 calculates the MTF correction value in each pixel of the image read by the scanner 103 by using the MTF correction value set by the correction value setting unit 413 (ACT 303).

  A method for calculating the MTF correction value of each pixel will be described with reference to FIG. FIG. 17 shows an image (read image of the scanner 103) I divided by a plurality of blocks, and shows a part of the image I in an enlarged manner.

  Each point a to d illustrated in FIG. 17 is a center point of each of the blocks A1 to D1. FIG. 17 is a diagram illustrating a method for calculating the MTF correction value of the pixel (target pixel) e included in the block A1. Blocks A2 to D2 are blocks obtained by dividing a rectangular area formed by the points a to d on the basis of the point e. The rectangular area formed by the points a to d is divided by a horizontal line (corresponding to the main scanning direction) passing through the point e and a vertical line (corresponding to the sub scanning direction) passing through the point e. Block A2 corresponds to block A1 and has the same point a. Each of the blocks B2 to D2 corresponds to each of the blocks B1 to D1, and has the same points b to d.

  The correction value calculation unit 414 calculates the MTF correction value of the pixel e based on the following formula (2).

C _MTF (e) indicates the MTF correction value of the pixel e. A2, B2, C2, and D2 indicate the areas of the respective blocks A2 to D2. C _{A1 to} C _D1 indicate MTF correction values of the respective blocks _A1 to _{D1, and} are information set by the correction value setting unit 413. X is the horizontal length of the rectangular area formed by the points a to d, and Y is the vertical length of the rectangular area. The horizontal direction corresponds to the main scanning direction of the scanner 103, and the vertical direction corresponds to the sub-scanning direction of the scanner 103.

  For the pixel located in the rectangular area formed by the points a to d, the MTF correction value is calculated based on Expression (2). For a pixel that is out of the rectangular area formed by the points a to d, a rectangular area including the pixel (corresponding to a rectangular area formed by the points a to d) is specified, and based on Expression (2) An MTF correction value is calculated.

  In Expression (2), since the MTF correction value of the pixel e is calculated based on the ratio of the areas of the blocks A2 to D2, the MTF correction value changes abruptly at the boundary between adjacent blocks. Can be reduced. In addition, an abrupt change in image quality can be suppressed in the image after performing the MTF correction process. Since the MTF correction value of each pixel can be calculated using the MTF correction value of each of the blocks A1 to D1, it is not necessary to store the MTF correction value of each pixel, and the storage capacity of the HDD 53 can be reduced.

  The table generation unit 415 generates a parameter switching table based on the MTF correction value of each pixel (ACT 304 in FIG. 15). As shown in FIG. 18, the table generation unit 415 divides the MTF correction value of each pixel into a plurality of sections, and sets parameters P1 to P9 corresponding to each section. The parameter is a parameter used in the MTF correction process. The table shown in FIG. 18 is set in advance and can be stored in the HDD 53 or the like.

  For example, if the MTF correction value of the pixel is “7”, the parameter P3 is set, and if the MTF correction value is “−7”, the parameter P7 is set. If the MTF correction value is a positive value, the MTF value is increased in the MTF correction process, and if the MTF correction value is a negative value, the MTF value is decreased in the MTF correction process.

  Since the MTF correction value uses a value obtained by subtracting the MTF average value of each block N from the MTF target value as shown in the above formula (1), if the MTF correction value is a positive value, the MTF value is If the MTF correction value is a negative value, the MTF value is decreased. When obtaining the MTF correction value by subtracting the MTF target value from the MTF average value of each block N, if the MTF correction value is a positive value, the MTF value is decreased and the MTF correction value is a negative value. For example, the MTF value is increased.

  19A is a table showing the MTF correction value of each pixel, and FIG. 19B is a parameter switching table. The table generation unit 415 converts the table of MTF correction values into a parameter switching table using the table shown in FIG. The numbers shown in FIG. 19B correspond to the numbers of parameters P1 to P9.

  The correction processing unit 416 performs filter processing as MTF correction processing (ACT 305). The correction processing unit 416 performs filter processing on the image (scanned image) generated by the scanner 103 using a parameter switching table. Since the parameter switching table sets filter processing parameters for each pixel, the correction processing unit 416 performs filter processing on each pixel of the scan image using the corresponding parameter. The data processing unit 417 performs image processing on the image data subjected to the filter processing (ACT 306).

  The processing described with reference to FIGS. 6, 10, and 15 can be realized by causing the CPU to execute a program stored in the HDD 53. The storage location of the program is not limited to the HDD, but, for example, RAM (Random Access Memory), ROM (Read Only Memory), DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), VRAM (Video RAM), flash A memory can be used.

  The case where the program for executing the processing of the present embodiment is recorded in advance in a storage area provided in the image forming apparatus 100 is illustrated, but the program may be downloaded from the network to the image forming apparatus 100, A program stored in a computer-readable recording medium may be installed in the image forming apparatus 100. The recording medium may be any recording medium that can store a program and can be read by a computer. As a recording medium, for example, an internal storage device such as a ROM and a RAM, a portable storage medium such as a CD-ROM, a flexible disk, a DVD disk, a magneto-optical disk, and an IC card, and a computer program are stored. There are databases, other computers and their databases, transmission media on lines, and the like. The function obtained by installing or downloading in advance may be realized in cooperation with an OS (operating system) or the like inside the apparatus. It is also possible to cause at least a part of the processing realized by causing the CPU or MPU to execute the program to be executed in a circuit by the ASIC.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications, various improvements, alternatives and modifications belonging to the equivalent scope of the claims are all within the scope of the present invention.

100: Image forming apparatus, 102: Image forming unit, 103: Scanner,
105: Operation panel, 106: Paper discharge tray, 11: Platen glass, 12: Document,
13: Platen cover, 14a to 14c: Folding mirror, 15: Imaging lens,
16: Image sensor, 16a: Light receiving element, 20: Lighting unit,
31, 32: carriage, 40: image processing unit, 41: first processing unit, 42: second processing unit,
411: Average value calculation unit, 412: Bus select circuit (SEL), 413: Correction value setting unit,
414: correction value calculation unit, 415: table generation unit, 416: correction processing unit,
50: System unit, 51: Page memory, 52: Page memory controller,
53: HDD, 54: System controller,

Claims (10)

A setting unit for setting a correction value used in the MTF correction processing of the image data generated by the scanner in each of a plurality of block regions that divide the image region;
Using the correction value of the block region including the target pixel and the correction value of the block region adjacent to the block region including the target pixel, the correction value in all pixels included in each block region A calculation unit for calculating
A correction processing unit that performs the MTF correction processing of the image data using the correction value of each pixel calculated by the calculation unit;
An image processing apparatus comprising: The calculation unit calculates the correction value of each pixel based on the following formula (I):
The image processing apparatus according to claim 1.   The said setting part sets the difference of the MTF value of each said block area | region obtained from the said image data, and a target value as said correction value of each said block area | region, The Claim 1 or 2 characterized by the above-mentioned. Image processing device.   The image processing apparatus according to claim 3, wherein the MTF value of each block area is an average value of MTFs of all pixels included in each block area.   The image processing apparatus according to claim 1, wherein the correction processing unit performs a filter process as the MTF correction process. In each of the plurality of block areas that divide the image area, a correction value used in the MTF correction processing of the image data generated by the scanner is set.
Using the correction value of the block region including the target pixel and the correction value of the block region adjacent to the block region including the target pixel, the correction value in all pixels included in each block region To calculate
The MTF correction processing of the image data is performed using the calculated correction value of each pixel.
An image processing method. Based on the following formula (II), the correction value of each pixel is calculated.
The image processing method according to claim 6.   8. The image processing method according to claim 6, wherein a difference between an MTF value of each block area obtained from the image data and a target value is set as the correction value of each block area.   The image processing method according to claim 8, wherein the MTF value of each block region is an average value of MTFs of all pixels included in each block region. The image processing method according to claim 6, wherein a filter process as the MTF correction process is performed.