JP6790987B2 - Image processing equipment, image forming equipment, image processing methods and programs - Google Patents

Description

The present invention relates to an image processing apparatus, an image forming apparatus, an image processing method and a program.

Conventionally, an image input in order to eliminate an image defect (hereinafter, may be referred to as "vertical streak") such as a streak that occurs in the same direction as the feed direction of a recording medium (for example, paper) in an image forming apparatus. A technique for correcting the density value of data is known.

For example, Patent Document 1 describes, in addition to the gradation characteristics (relationship between input gradation value and output gradation value) of each primary color when an image of primary color (basic constituent color) is printed, a plurality of basic configurations. A technique for correcting the density value of input image data by obtaining the gradation characteristics of each primary color when printing an image of multiple colors in which colors are superimposed and creating a correction table based on these is disclosed. ing.

Here, depending on the number of gradations of the image data, the gradation may not be expressed smoothly. For example, it is difficult to smoothly connect all gradations with an 8-bit gradation number. In such a case, if the gradation of the 8-bit image data is changed by the correction using the correction table, the difference in gradation becomes large due to the correction, and on the contrary, there arises a problem that vertical streaks are conspicuous. ..

In order to solve the above-mentioned problems and achieve the object, the present invention includes a plurality of halftone cells showing a set of pixels whose gradation is expressed by two or more values, and each of the above is described by the area gradation method. For each of a plurality of positions in the main scanning direction of the image data in which the gradation of the halftone cell is expressed, a correction value having a larger number of gradations than the halftone cell and indicating a value for obtaining a target output is supported. It is an image processing apparatus including a storage unit that stores the added correction information and a correction unit that corrects the image data based on the correction information.

According to the present invention, it is possible to suppress a step in gradation generated when correcting vertical streaks.

FIG. 1 is a diagram for explaining a tone jump. FIG. 2 is a diagram for explaining a conventional problem. FIG. 3 is a diagram showing an example of the hardware configuration of the MFP. FIG. 4 is a diagram for explaining input image data. FIG. 5 is a diagram showing an example of the function of the MFP. FIG. 6 is a diagram showing an example of correction information. FIG. 7 is a flowchart showing an operation example of the MFP. FIG. 8 is a diagram showing a unit of a composite halftone cell that performs area gradation processing in input image data. FIG. 9 is a flowchart showing an example of a process of determining whether or not each halftone cell included in one composite halftone cell is a correction target. FIG. 10 is a diagram showing an example of correction flag information. FIG. 11 is a diagram showing an example of correction flag information. FIG. 12 is a diagram showing an example of correction information. FIG. 13 is a diagram showing the result of multiplying the correction flag and the correction value for each halftone cell. FIG. 14 is a diagram showing an example of correspondence information. FIG. 15 is a diagram showing final correction data. FIG. 16 is a diagram showing an image of image data before and after correction. FIG. 17 is a flowchart showing an example of processing in the case of obtaining the final correction data and performing correction. FIG. 18 is a diagram showing an example of correction information.

Hereinafter, embodiments of an image processing apparatus, an image forming apparatus, an image processing method, and a program according to the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, as an example of the image forming apparatus to which the present invention is applied, a multifunction device (MFP: Multifunction Peripheral) will be described as an example, but the present invention is not limited thereto. A multifunction device is a device having a plurality of different functions such as a copy function, a scanner function, a print function, and a fax function.

Before explaining the specific contents of the embodiment, the outline of the present invention will be described. In order to create an 8-bit gradation (which can be expressed in 256 ways) in the image forming apparatus, screening is performed and image processing is performed so that a smooth gradation can be obtained. As shown in FIG. 1, an 8-bit scale is performed. It may happen that all gradations are not smoothly connected in the key. In the present specification, this portion that cannot be smoothly connected is referred to as "tone jump" (see FIG. 1).

There are few image forming devices capable of expressing gradation by the shading of one pixel itself. An example is a sublimation printer. Normally, as typified by offset printing, it is common that one pixel has only 1-bit information (binary information) indicating whether or not ink adheres. In the laser exposure electrophotographic method, there is also a method in which the exposure time of one pixel is time-divided to express a gradation of about 16 values (4 bits), but one pixel expresses an 8-bit gradation. Can't. Therefore, in an image forming apparatus such as offset printing or an electrophotographic method, an area gradation method is adopted in which the gradation of an image is expressed by the aggregated area of pixels such as halftone dots (halftone cells).

Generally, the image input to the image forming apparatus is expressed in 8-bit gradation using area gradation, and the output image is also generally expressed in 8-bit gradation using area gradation. .. However, in an image forming apparatus that corrects image defects (density unevenness and streaks) by converting input image data, there is a tone jump in the gradation image that has not corrected the image defects (see FIG. 1, all the gradation images). In the case of an image in which the gradations of the above cannot be connected smoothly), the correction may cause many fine streaks due to the tone jump, and the streaks may be more noticeable than the uncorrected image.

An image in which streaks are more conspicuous than an uncorrected image is an image with a uniform halftone in the vicinity of gradation in which tone jump occurs. In an uncorrected halftone uniform image, the tone jump is not visible because the gradation of the original image does not change, but when the above correction is performed, the tone jump is performed to change the gradation of the original image. It may be generated and conspicuous as fine streaks (see Fig. 2).

The present invention aims to eliminate the tone jump that occurs when correcting vertical streaks, increase the number of gradations of the correction value for obtaining the target output, and smoothly connect the gradations of the correction positions. As a result, the occurrence of tone jump can be suppressed. Hereinafter, the specific contents of the embodiment will be described in detail with reference to the accompanying drawings.

(First Embodiment)
FIG. 3 is a diagram showing an example of the hardware configuration of the MFP 1 of the present embodiment. As shown in FIG. 3, the MFP 1 includes a CPU 10, an image input unit 20, a reading unit 30, a calibration memory 40, a storage unit 50, and an image output unit 60.

The CPU 10 comprehensively controls the operation of the entire MFP 1.

The image input unit 20 receives image data from the host device. In the following description, the image data received from the host device may be referred to as "input image data". In this example, the input image data is image data represented by 8-bit gradation. More specifically, as shown in FIG. 4, the input image data shows a set of pixels whose gradation is expressed by two or more values (in the example of FIG. 4, a set of 16 × 16 = 256 pixels). This is image data that includes a plurality of halftone cells (halftone dots) and expresses the gradation of each halftone cell (8-bit gradation in this example) by the area gradation method. In FIG. 4, the case where the gradation of each pixel is expressed by two values (expressed by one bit) is taken as an example, but the present invention is not limited to this, and for example, the gradation is expressed by multiple values (expressed by multiple bits). It may be in the form of being.

The description of FIG. 3 will be continued. The reading unit 30 is a device for optically reading an image formed on a recording medium (for example, paper) by the image output unit 60 under the control of the CPU 10, and includes, for example, a line sensor. As the configuration of the reading unit 30, various known configurations of the scanner device can be used.

The calibration memory 40 is a device that stores in advance a test image used in a calibration process for generating correction information described later.

The storage unit 50 stores the correction information obtained in the calibration process. More specifically, the storage unit 50 associates a correction value for obtaining a target output with a larger number of gradations than the halftone cell for each of a plurality of positions in the main scanning direction of the input image data. Store the correction information. Here, the main scanning direction refers to a direction orthogonal to the feeding direction (sub-scanning direction) of the recording medium (paper in this example).

The image output unit 60 is a device for forming image data such as input image data (input image data after correction described later) and a test image stored in the calibration memory 40 on a recording medium under the control of the CPU 10. Is.

More specifically, the image output unit 60 is a device for fixing a toner image corresponding to image data such as input image data and a test image stored in the calibration memory 40 on a recording medium. Each toner of CMYK is mounted on the image output unit 60, and an image forming unit including a photoconductor, a charger, a developing device and a photoconductor cleaner, an exposure device and a fixing machine are mounted on each toner. There is. The image output unit 60 irradiates a light beam from the exposure device according to the image data to form a toner image corresponding to each toner on the photoconductor, and transfers the toner image formed on the photoconductor to the intermediate transfer belt. After (primary transfer), the toner image transferred on the intermediate transfer belt is transferred to a recording medium (secondary transfer), and the toner image transferred on the recording medium is transferred to a recording medium at a temperature within a predetermined range by a fixing machine. Fix by heating and pressurizing. As a result, an image is formed on the recording medium.

Since the configuration of the image output unit 60 as described above is well known, detailed description thereof will be omitted here. As the configuration of the image output unit 60, various known printer engine configurations can be used. The recording medium is not limited to paper.

FIG. 5 is a diagram showing an example of the functions of the MFP 1 of the present embodiment. As shown in FIG. 5, the MFP 1 includes a creation unit 101, an input image data reception unit 102, a correction unit 103, and an output control unit 104. For convenience of explanation, FIG. 5 mainly illustrates the functions related to the present embodiment, but the functions of the MFP 1 are not limited to these.

The creation unit 101 creates the above-mentioned correction information. In the embodiment, the creation unit 101 performs calibration processing to correct the number of gradations at each of a plurality of positions in the main scanning direction of the image data as compared with the halftone cell and to obtain a target output. Create correction information associated with values. For example, the creation unit 101 can create correction information based on the reading brightness of a test pattern obtained by forming a test image prepared in advance on a recording medium. More specifically, the acquisition of the correction value is performed offline because it is not necessary to acquire the correction value during printing. The image output unit 60 of the MFP 1 (digital printing machine) outputs a chart having a uniform density in the direction perpendicular to the paper feed direction. Multiple process colors and gradations of each color are incorporated in the chart and output without correction. At this time, on the output chart, the density unevenness generated from the MFP 1 is output on the chart. The output chart is read by a scanner, and unevenness and streaks in the paper feed direction of MFP1 are read for each color and each gradation. The correction value can be calculated so as to cancel the read unevenness and streak data.

Here, the number of gradations of the correction value is larger than the number of gradations (8 bits) of the image data, and in this example, it is 9 bits. That is, the correction value can express 512 gradations. However, it is not limited to this. Here, the 9-bit correction value corresponding to the 8-bit "1" correction value (indicating that the gradation value of the image data is increased by "1") is also "1", and the 9-bit correction value is also set. Is premised on the fact that it can be set to 512 values from -127 values to 128 values in 0.5 increments.

For example, as shown in FIG. 6A, the correction information is in a look-up table (LUT) format in which a 9-bit correction value is associated with each halftone cell (halftone dot) that divides the input image data into a plurality of parts. It may be information. In this example, the density (resolution) of the pixels included in the halftone cell is 300 dpi, but the density is not limited to this. The correction information created by the creation unit 101 is stored in, for example, a storage unit 50 or the like.

The input image data receiving unit 102 receives the input image data from the host device. The correction unit 103 corrects the image data based on the above-mentioned correction information. In this example, the correction unit 103 corrects the input image data received by the input image data reception unit 102 based on the correction information created by the creation unit 101.

In the above-mentioned correction information, when the correction value is associated with any position in the main scanning direction, the correction unit 103 is arranged in the sub-scanning direction orthogonal to the main scanning direction at that position. The value of the pixel included in the set of the number of halftone cells corresponding to the number of gradations of the value is corrected according to the correction value. For example, in FIG. 6A, a correction value of −0.5 value is associated with each halftone cell (halftone dot) located in the third column counting from the left. In this example, since the area of one halftone cell is an area capable of expressing 8-bit gradation, an area equivalent to two halftone cells is required to express 9-bit gradation. That is, in this example, the number of halftones corresponding to the number of gradations of the correction value is "2", and two halftone cells adjacent to each other in the sub-scanning direction form one set (below). , This set of halftone cells may be referred to as a composite halftone cell).

Then, the correction unit 103 makes the 8-bit correction value of each of the plurality of halftone cells constituting the set different so that the correction value of 9 bits can be obtained for the entire set (composite halftone cell). As described above, when the 9-bit correction value is -0.5 value, two halftone cells (two halftone cells adjacent to each other in the sub-scanning direction) constituting one set (composite halftone cell). By setting one of the correction values to 0 value and the other correction value to -1 value, a correction value of −0.5 value is realized for the entire set. In this way, as shown in FIG. 6B, by making the correction values of the halftone cells to be corrected adjacent to each other in the sub-scanning direction different from each other, it is possible to prevent the same correction portion from being continuous in the vertical direction. It is possible to suppress the occurrence of tone jump.

The output control unit 104 shown in FIG. 5 controls to output the input image data after being corrected by the correction unit 103. More specifically, the output control unit 104 controls the image output unit 60 so as to form a toner image corresponding to the corrected input image data on the recording medium.

The functions of the MFP 1 described above (creating unit 101, input image data receiving unit 102, correction unit 103, output control unit 104, etc.) are realized by the CPU 10 executing a program stored in the storage unit 50 or the like. However, it is not limited to this. For example, at least a part of the functions (creating unit 101, input image data receiving unit 102, correction unit 103, output control unit 104, etc.) of the MFP 1 is realized by a dedicated hardware circuit (semiconductor integrated circuit, etc.). It may be.

FIG. 7 is a flowchart showing an operation example of the MFP 1 of the present embodiment. As shown in FIG. 7, first, the input image data receiving unit 102 receives the input image data from the host device (step S1). Next, the correction unit 103 corrects the input image data received in step S1 based on the above-mentioned correction information (step S2). Next, the output control unit 104 controls to output the input image data corrected in step S2 (step S3).

As described above, in the present embodiment, the gradations of the correction positions can be smoothly connected by increasing the number of gradations of the correction value for obtaining the target output. Therefore, according to the present embodiment, it is possible to suppress a gradation step (tone jump) that occurs when correcting vertical streaks.

For example, when the number of vertical streaks when the 8-bit input image data is an A3 size full-scale halftone image is compared between the conventional example and the present embodiment, the number of vertical streaks in the conventional example is 12. On the other hand, the number of vertical stripes in this embodiment was 0.

(Second Embodiment)
In the second embodiment, an example of a method of specifying the correction target and a method of calculating the correction value will be described in more detail. The description of the parts common to the first embodiment described above will be omitted as appropriate.

In the input image data shown in FIG. 8, the frame surrounded by the thick line represents the unit of the composite halftone cell that performs the area gradation processing (in this example, one composite halftone cell is composed of four halftone cells. Will be). Here, for each of the composite halftone cells, it is determined whether or not each halftone cell constituting the composite halftone cell is a correction target, and the density of adjacent columns and rows is determined for each halftone cell. If they are equal, it is determined that the correction target is applied.

FIG. 9 is a flowchart showing an example of a process of determining whether or not each halftone cell included in the composite halftone cell is a correction target. As shown in FIG. 9, in the correction unit 103, the density value of the halftone cell to be determined is four halftones constituting one composite halftone cell (composite halftone cell including the halftone cell to be determined). It is determined whether or not the density values of the halftone cells to be determined and the halftone cells adjacent in the column direction of the cells match (step S11). If the result of step S11 is negative (step S11: No), the correction unit 103 determines that the halftone cell to be determined is not the correction target, and sets the correction flag to "0" (step S12).

When the result of step S11 is affirmative (step S11: Yes), the correction unit 103 indicates that the density value of the halftone cell to be determined is adjacent to the halftone cell to be determined in the row direction among the four halftone cells. It is determined whether or not it matches the density value of the halftone cell (step S13). If the result of step S13 is negative (step S13: No), the process proceeds to step S12 described above. On the other hand, when the result of step S13 is affirmative (step S13: Yes), the correction unit 103 determines that the halftone cell to be determined is the correction target, and sets the correction flag to "1" (step S14). ..

A determination example for the composite halftone cell 200 in the upper right of FIG. 8 is shown. Of the four halftone cells constituting the composite halftone cell 200, the halftone cell in the first row and the first column is referred to as the "No. 1 halftone cell", and the halftone cell in the first row and the second column is referred to as the "No. 1 halftone cell". The halftone cell in the second row and the first column is referred to as the "No. 3 halftone cell", and the halftone cell in the second row and the second column is referred to as the "No. 4 halftone cell". Halftone cell ". In this example, the density value of "No. 3 halftone cell" indicates "gray", and the density value of the other halftone cells indicates "white".

The density value of the "No. 1 halftone cell" is the same as the density value of the "No. 2 halftone cell" adjacent in the row direction (concentration value indicating white), but the "No. 1 halftone cell" is adjacent in the column direction. The density value of "No. 3 halftone cell" is gray, and the density value is different. Therefore, the "No. 1 halftone cell" is not subject to correction. The density value of the "No. 2 halftone cell" is the same as the density value of the "No. 1 halftone cell" adjacent in the row direction (concentration value indicating white), and the density value of the "No. 1 halftone cell" is adjacent in the column direction. It is the same as the density value of ".4 halftone cell". Therefore, "No. 2 halftone cell" is a correction target. The concentration value of the "No. 3 halftone cell" is different from the concentration value of the "No. 4 halftone cell" adjacent in the row direction, and the concentration value of the "No. 1 halftone cell" adjacent in the column direction. Also different from the value. Therefore, "No. 3 halftone cell" is not subject to correction. The density value of the "No. 4 halftone cell" is the same as the density value of the "No. 2 halftone cell" adjacent in the column direction, but the density value of the "No. 3 halftone cell" adjacent in the row direction. The density value of "" indicates gray, and the density value is different. Therefore, "No. 4 halftone cell" is not subject to correction. The above judgment was performed on all halftone cells, and the correction target was represented by "1" (correction flag set to "1"), and the non-correction target was represented by "0" (correction flag set to "0"). FIG. 10. Information in which the correction flag is set for each halftone cell as shown in FIG. 10 may be referred to as “correction flag information”.

Next, a method of determining the final correction value from the correction flag information and the correction information will be described. FIG. 11 is a diagram showing an example of correction flag information, and the correction flag information in this example is information indicating a correction flag for each halftone cell. FIG. 12 is a diagram showing an example of correction information, and the correction information in this example is information showing a correction value (in this example, a remainder after 8-bit correction) for each halftone cell. In this example, the correction unit 103 obtains the product of the correction flag and the correction value indicated by the correction information for each halftone cell. FIG. 13 is a diagram showing the result of multiplying the correction flag and the correction value for each halftone cell by using the correction flag information shown in FIG. 11 and the correction information shown in FIG.

In this example, the composite halftone cell is configured by using the values of odd rows and odd columns (first row and first column of the four halftone cells constituting the composite halftone cell) for each composite halftone cell. The four halftone cells to be used and the four correction values corresponding to one-to-one are determined. Here, as shown in FIG. 14, four halftone cells constituting a composite halftone cell including the halftone cell for each candidate value indicating a correction value candidate that can be taken by the odd-numbered row and odd-numbered column halftone cell. With reference to the corresponding information associated with each final correction value of, for each composite halftone cell, the correction value in the first row and first column of the composite halftone cell (multiplication of the correction flag and the correction value). The final correction value associated with the result) (the final correction value of each of the four halftone cells constituting the composite halftone cell) is obtained. In this way, the final correction value of each halftone cell can be determined. In this embodiment, the candidate values of the odd-numbered rows and odd-numbered columns of halftone cells are used to determine the final correction value, but the present invention is not limited to this, and for example, the candidate values of halftone cells at other positions are used. Is also used as a key to determine the final correction value of each of the four halftone cells constituting the composite halftone cell including the halftone cell. In short, the corresponding information includes the candidate value of the halftone cell corresponding to any position of the composite halftone cell and each of the plurality of (four in this example) halftone cells constituting the composite halftone cell. The information may be as long as it is associated with the final correction value. FIG. 15 is a diagram showing final correction data showing the final correction value of each halftone cell in the above example. This final correction data will be added to the original image (input image data). FIG. 16A is an image of the input image data before correction, and FIG. 16B is an image after correction.

FIG. 17 is a flowchart showing an example of processing in the case of obtaining the final correction data and performing correction. As shown in FIG. 17, the correction unit 103 obtains the product of the correction value and the correction flag for each halftone cell (step S20). Next, the correction unit 103 obtains the final correction data using the above-mentioned correspondence information (step S21). The specific contents are as described above. Next, the correction unit 103 adds the final correction data to the input image data (step S22).

(Third Embodiment)
Next, a third embodiment will be described. In the present embodiment, when the correction value is associated with any position in the main scanning direction, the correction unit 103 increases the resolution in the sub-scanning direction at that position. Then, the correction unit 103 is included in a set of a number of halftone cells arranged in the sub-scanning direction of the position and corresponding to the number of gradations of the correction value, as in the first embodiment described above. The pixel value is corrected according to the correction value.

In the first embodiment described above, in order to create a 9-bit correction value, two halftone cells (halftone dots) adjacent to each other in the sub-scanning direction are used to increase the number of area gradations, but the second embodiment. Like the form, it is necessary to use four halftone cells in order to make a correction value of, for example, 10 bits. When the resolution of the pixel is 300 dpi, the size of the four halftone cells corresponds to 0.34 mm.

For example, in the case of high-resolution image data such as 1200 dpi, there is no particular problem even when four halftone cells are used as one composite halftone cell. However, for example, in the case of 300 dpi image data, when the observer observes the image from a position 300 mm away, the sensitivity to the density fluctuation of the cycle near 1 mm / cycle is high, and the cycle of about 0.3 mm / cycle is easily perceived. It becomes a cycle. Therefore, if the resolution of the image is 300 dpi and the number of gradations is increased by using four halftone cells, the cycle may become perceptible.

Therefore, in the present embodiment, the resolution in the sub-scanning direction is doubled to 600 dpi, the size of the four halftone cells is reduced to 0.17 mm, and the area gradation is created in a cycle of 0.17 mm / cycle. As a result, it is possible to suppress the difference in gradation that occurs when correcting vertical streaks while lowering the sensitivity to density fluctuations.

FIG. 18A is a diagram showing an example of correction information before increasing the resolution. Further, FIG. 18B is a diagram showing an example of correction information after increasing the resolution. The correction value "0.25" in the sixth column from the left in FIG. 18 (A) corresponds to the sixth unit column from the left in FIG. 18 (B), and here, (upper left, upper right, lower left, lower right). ), Expressed as (1,0,0,0).

Similarly for the other correction values, the correction value "-0.75" before increasing the resolution is set to (-1, -1, -1, 0) by using the four pixels constituting one unit. Represent. Further, the correction value "-0.5" before increasing the resolution is expressed as (-1, -1, 0, 0) using four pixels. Further, the correction value "-0.25" before increasing the resolution is expressed as (-1,0,0,0) using four pixels. Further, the correction value "0.5" before increasing the resolution is expressed as (1,1,0,0) using four pixels. Further, the correction value "0.75" before increasing the resolution is expressed as (1,1,1,0) using four pixels. As described above, the gradation equivalent to 10 bits can be corrected by the 8-bit gradation by combining the pixel areas.

For example, when the number of vertical streaks when the 8-bit input image data is an A3 size full-scale halftone image is compared between the conventional example and the present embodiment, the number of vertical streaks in the conventional example is 12. On the other hand, the number of vertical stripes in this embodiment was 0.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments as they are, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

Further, the program executed by the MFP1 (CPU10) of each of the above-described embodiments is a file in an installable format or an executable format, and is a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versaille Disk). ), USB (Universal Serial Bus), etc., may be configured to be recorded and provided on a computer-readable recording medium, or may be configured to be provided or distributed via a network such as the Internet. In addition, various programs may be configured to be provided by incorporating them into a ROM or the like in advance.

1 MFP
10 CPU
20 Image input unit 30 Reading unit 40 Calibration memory 50 Storage unit 60 Image output unit 101 Creation unit 102 Input image data reception unit 103 Correction unit 104 Output control unit

Japanese Patent No. 4661376

Claims (6)

A plurality of image data in the main scanning direction, which includes a plurality of halftone cells indicating a set of pixels whose gradation is expressed by two or more values, and in which the gradation of each halftone cell is expressed by the area gradation method. A storage unit that stores correction information associated with a correction value that has a larger number of gradations than the halftone cell and indicates a value for obtaining a target output for each position of.
A correction unit that corrects the image data based on the correction information is provided.
Image processing device. When the correction value is associated with any position in the main scanning direction, the correction unit is arranged in the sub-scanning direction orthogonal to the main scanning direction at the position of the correction value. The values of the pixels included in the set of the halftone cells in the number corresponding to the number of gradations are corrected according to the correction value.
The image processing apparatus according to claim 1. When the correction value is associated with any position in the main scanning direction, the correction unit increases the resolution in the sub-scanning direction at that position.
The image processing apparatus according to claim 2. A plurality of image data in the main scanning direction, which includes a plurality of halftone cells indicating a set of pixels whose gradation is expressed by two or more values, and in which the gradation of each halftone cell is expressed by the area gradation method. A storage unit that stores correction information associated with a correction value that has a larger number of gradations than the halftone cell and indicates a value for obtaining a target output for each position of.
A correction unit that corrects the image data based on the correction information is provided.
Image forming device. A plurality of image data in the main scanning direction, which includes a plurality of halftone cells indicating a set of pixels whose gradation is expressed by two or more values, and in which the gradation of each halftone cell is expressed by the area gradation method. Each position includes a correction step of correcting the image data based on correction information associated with a correction value having a larger number of gradations than the halftone cell and indicating a value for obtaining a target output. ,
Image processing method. On the computer
A plurality of image data in the main scanning direction, which includes a plurality of halftone cells indicating a set of pixels whose gradation is expressed by two or more values, and in which the gradation of each halftone cell is expressed by the area gradation method. A correction step for correcting the image data is executed based on the correction information associated with the correction value indicating the value for obtaining the target output and having a larger number of gradations than the halftone cell for each position of. Program to let you.