JP4389533B2 - Image processing device - Google Patents

Description

  The present invention relates to a facsimile apparatus, a printer, a copying machine, or a complex machine (hereinafter referred to as an image processing apparatus) that performs printing output based on an image signal.

  In an electrophotographic image processing apparatus, a line pattern called a line screen is mainly used in screen processing for reproducing halftones. However, recently, in the field of light printing, an electrophotographic general-purpose color printer is often used instead of an offset printing machine, so a screen similar to the halftone of the screen used in offset printing is also used in a color printer. It is requested. In addition, various types of screens such as a line type, a dot type, a grid type, a screen line number, a dot number, and the like are desired from fine to coarse.

In response to these demands, an image processing apparatus has been developed in which a plurality of types of screens are mounted in an image processing apparatus, and one screen can be selected and printed (for example, Patent Document 1). reference).
JP 2002-218243 A

  In an image processing apparatus, output characteristics may fluctuate due to exhaustion of equipment, changes in environmental conditions, and the like, and therefore, γ correction is generally performed on an image to be printed. The γ correction uses a γ correction curve for converting the gradation of the output image into a target gradation for the input image. For example, the input image is displayed using a one-dimensional LUT (Look Up Table) indicating the γ correction curve. By converting the image, an output image converted to the target gradation can be obtained.

  For example, in a color laser printer, γ correction is performed in two stages. Many color laser printers use a pulse width modulation (hereinafter referred to as PWM) method for laser exposure control, and γ correction is performed before exposure by PWM in order to correct gradation fluctuations due to the PWM characteristics. (This γ correction before PWM is called PWM correction). In some cases, the output characteristics cannot be stably maintained only by this PWM correction. In this case, γ correction is performed by a γ correction curve created including the screen characteristics as preprocessing of the screen processing. That is, image processing is performed on the image to be printed in the order of γ correction processing according to the screen, screen processing, and PWM correction processing.

  The image processing apparatus is provided with a γ correction curve LUT corresponding to each screen (hereinafter referred to as a γ correction table). Updates have been made. This is because a better gradation can be maintained or improved by updating the γ correction table as needed according to fluctuations in output characteristics.

  However, when a plurality of types of screens are installed, a γ correction table is prepared for all of the screens. Therefore, as the number of screen types increases, it takes time to update the γ correction table. For example, if 10 types of screens are installed and the time required for updating the γ correction table for one type of screen is 30 seconds, a total of 5 minutes is required. During this time, since the image processing apparatus cannot execute other operations such as a printing operation, the user cannot use the image processing apparatus and must wait.

  Since the update of the γ correction table is also performed when the printing process is changed, such as when the output speed is changed, the update period of the γ correction table is short, and image processing is performed when the update is executed several times a day. The use time of the apparatus is limited, and the work efficiency of the user is reduced.

  Even if various screens are installed in the image processing apparatus, it is conceivable that the user always likes and uses the same screen. Frequent updating of the γ correction table for screens that are less frequently used causes unnecessary energy consumption.

  Furthermore, in the image processing apparatus described in Patent Document 1, when a γ correction table of a screen among a plurality of screens is updated, the γ correction tables of other screens are also updated based on correction data obtained at the time of the update. The method of doing is described. However, although this method can shorten the time required for the update, it is expected that the correction accuracy of the γ correction for other screens is lowered.

  An object of the present invention is to provide an image processing apparatus that efficiently updates a γ correction table.

The invention described in claim 1
An image processing unit that screen-processes the correction image using a screen for reproducing the halftone of the image;
A printer unit for forming a toner image of the correction image subjected to the screen processing;
A sensor for measuring the density value of the toner image;
A control unit that creates a γ correction curve having a reverse characteristic of the density value measured by the sensor with respect to the target gradation, creates a γ correction table by tabulating the γ correction curve, and
A storage unit that stores M types of screens used by the image processing unit and a γ correction table created for each of the M types of screens;
When updating the gamma correction table of each screen stored in the storage unit, screen processing by the image processing unit using the N types of screens selected from the M types of screens by the user, the printer unit In this case, the toner image is formed by the measurement and the measurement by the sensor is performed, and a new γ correction table is created for each of the N types of screens by the control unit and updated and stored in the storage unit .

  Here, M is an integer of 0 <M, and N is an integer of 0 <N ≦ M.

The invention according to claim 2 is the image processing apparatus according to claim 1,
The control unit for the selected N types of screens, when the condition for updating the γ correction table is satisfied, characterized by creating a new γ correction table against the corresponding N type screen .

The invention according to claim 3 is the image processing apparatus according to claim 1 or 2,
When one of the N types of screens used for printing is selected by the user during printing , the image processing unit uses a γ correction table corresponding to the selected one type of screen. In addition to performing γ correction on the print target image, screen processing is performed using the one type of screen.

The invention according to claim 4 is the image processing apparatus according to any one of claims 1 to 3,
In printing, only the N types of screens can be selected.

  According to the first aspect of the present invention, the γ correction table is not updated for all M types of screens stored in the image processing apparatus, but N types selected from the M types of screens. Since the γ correction table is updated only for the screen, the time required for the update can be shortened, and waste of materials and energy consumption for the update can be eliminated. Therefore, the γ correction table can be updated efficiently.

  According to the second aspect of the invention, the γ correction table for N types of screens is updated only when a predetermined condition is satisfied. For example, a predetermined number of sheets have been printed since the previous update, or a predetermined period has elapsed. By setting this condition, the update can be performed at an appropriate timing.

  According to the third aspect of the invention, during printing, γ correction and screen processing are performed using one type of screen selected from among N types of screens and a γ correction table corresponding to the screen. Γ correction can be performed using the γ correction table that is being updated. Therefore, the correction accuracy can be improved and excellent gradation can be maintained.

  According to the fourth aspect of the present invention, since only N types of screens can be selected during printing, it is possible to prevent selection of other screens for which the correction table is not updated at any time.

  In the present embodiment, among the M types of screens prepared in the image processing apparatus, N types of screens selected via the operation unit are set to be usable, and the selected N types of screens are supported. An example of an image processing apparatus will be described in which only the γ correction table to be updated is automatically updated so that one type of screen to be used can be selected from among N types of screens during printing.

First, the configuration will be described.
FIG. 1 shows an internal configuration of the image processing apparatus 10 in the present embodiment.
As shown in FIG. 1, the image processing apparatus 10 includes an image scanner 11, an operation unit 12, a display unit 13, and a main body unit 20. The main body unit 20 includes an image processing unit 30, a printer unit 40, a storage unit 50, The control unit 60 is configured.

Hereinafter, each component will be described.
The image scanner 11 includes a CCD (Charge Coupled Device) sensor, an A / D converter, and the like. The image scanner 11 optically scans and exposes a document placed on a document table, and outputs an analog image signal photoelectrically converted by the CCD sensor. A digital image signal is obtained by A / D conversion. An image signal of the read document image is output to the image processing unit 30.

  The operation unit 12 includes a key group such as numeric keys and various function keys, a touch panel configured integrally with the display unit 13, and the like. The operation signal corresponding to the operated key is displayed on the touch panel. An operation signal corresponding to the input operation on the operation screen is output to the control unit 60.

  The display unit 13 includes an LCD (Liquid Crystal Display) or the like, and displays various operation screens, print results, and the like.

  The image processing unit 30 converts the image signal of the original image input from the image scanner 11 into Y (yellow), M (magenta), C (cyan), and K (black), which are color materials used in the printer unit 40. Each color is color-separated, and each color-separated image signal is sequentially subjected to γ correction processing, screen processing, PWM correction processing, and various image processing, and is output to the printer unit 40 as an exposure image signal.

  Here, the γ correction processing is γ correction performed in consideration of output characteristics in the printing process and screen characteristics of the screen to be used before the screen processing, using a γ correction table corresponding to the screen to be used. The gamma correction is performed on the image signal to be printed. On the other hand, the PWM correction process is a γ correction performed considering only the characteristics of the printing process such as the PWM characteristics and the development characteristics, and a γ correction table for PWM correction (hereinafter referred to as a PWM γ correction table) common to all screens. Is used to perform gamma correction.

The flow of image processing by the image processing unit 30 will be described with reference to FIG.
As shown in FIG. 2, when an image signal (RGB signal) of a document image is first input from the image scanner 11, the image processing apparatus 10 determines the image signal of each color R, G, B for each input signal level. The density is converted to a density value that can be output. Specifically, a one-dimensional LUT (hereinafter referred to as a density conversion table) that realizes density conversion using the density conversion curve shown in FIG. 3 is read from the storage unit 50, and an image is generated using the density conversion table. Converted.

  The image signal whose density has been converted for each of the colors R, G, and B is converted into an image signal of each color of Y, M, C, and K, and color separation is performed. The method is realized by circuitizing a primary or secondary matrix operation and a simple linear operation for outputting a black-generated image, or by a circuit combining a three-dimensional LUT and an interpolation operation. Various methods have been developed, and any method may be applied.

  When the image signals are separated into Y, M, C, and K image signals, γ correction is performed as shown in FIG. First, a γ correction table prepared for each of the colors Y, M, C, and K corresponding to the screen used for printing is read from the storage unit 50, and the output density with respect to the input density value of the image is read by this γ correction table. The image is converted so that the value is linear. That is, the input image is subjected to γ correction, and the gradation in the output image after γ correction realizes the target gradation.

  When the γ correction is completed, screen processing is performed. For the screen processing, for example, a technique described in Japanese Patent Laid-Open No. 2002-1558875 can be applied. That is, as a screen, multi-value output is performed using a one-dimensional LUT (hereinafter referred to as a screen table) arranged in a matrix in the dither method.

Next, PWM correction is performed on the image signals of the respective colors that have undergone the screen processing, as shown in FIG. During PWM correction, the PWM γ correction table stored in the storage unit 50 is read, and image conversion is performed using the PWM γ correction table so that the output density value with respect to the input density value of the image is linear. That is, the input image is PWM-corrected, and the gradation in the output image after PWM correction realizes the target gradation.
In this way, the image signals of the respective colors subjected to various image processes are output to the printer unit 40 as image signals for exposure.

  The printer unit 40 performs tandem printing, and includes exposure units 31Y, 31M, 31C, and 31K, developing devices 32Y, 32M, 32C, and 32K, and photosensitive drums that are provided for the respective colors Y, M, C, and K. 33Y, 33M, 33C, 33K, a transfer belt 34, a cleaning unit 35, a transfer roller 36, and a fixing unit 37. Note that a route R in the figure indicates a conveyance path of the printing paper P.

A printing process by the printer unit 40 will be described.
When an image signal for exposure of each color is input from the image processing unit 30 to the printer unit 40, first, an image signal for Y exposure is input to the exposure unit 31Y, and exposure development of the Y color image is performed. In the exposure unit 31Y, exposure is performed based on the input Y image signal for exposure, and a latent image is formed on the photosensitive drum 33Y. Next, development is performed by the developing device 32Y, and a toner image is formed on the photosensitive drum 33Y. The toner image formed on the photosensitive drum 33Y is transferred onto the transfer belt 34 (this is referred to as primary transfer).

  In this way, when the exposure development of the Y color image is completed, the exposure image development signal is input to the exposure unit 31M and the exposure development is performed for each color Y, M, C, K. Are sequentially transferred onto the transfer belt 34, and a color image in which the toner images of the respective colors are combined is formed on the transfer belt 34.

  On the other hand, the printing paper P is fed from a paper feeding unit (not shown) and conveyed to the transfer roller 36. In the transfer roller 36, the color image formed on the transfer belt 34 is collectively transferred onto one surface of the printing paper P (this is referred to as secondary transfer). The printing paper P to which the color image has been transferred is conveyed to the fixing unit 37, subjected to fixing processing, and discharged to a discharge tray (not shown) outside the apparatus. After printing, the residual toner on the transfer belt 34 is removed by the cleaning unit 35.

The printer unit 40 is provided with a photo sensor F for measuring the density of the toner image formed on the transfer belt 34.
The photosensor F includes a phototransistor and an LED (Light Emitting Diode) inside, and as shown in FIG. 6, the LED emits light during measurement, and the amount of reflected light is measured by the phototransistor.

  The photosensor F measures the amount of reflected light of the toner image of the correction image formed on the transfer belt 34 in the γ correction table update process described later. FIG. 7 shows an example of a correction image formed on the transfer belt 34. As shown in FIG. 7, the correction image is a step wedge image composed of a plurality of gradations, that is, patch-like density steps whose density changes stepwise. This correction image is prepared for each color Y, M, C, K, and the amount of reflected light is measured sequentially for each color correction image.

  It is assumed that the density value of each density step of the correction image is a known value and the density value is stored in the storage unit 50. When creating the γ correction table, the amount of reflected image of the correction image actually formed on the transfer belt 34 is measured with respect to the input density value of each density step that is known in advance, thereby correcting the correction image. Get the output density value. A γ correction table can be created from the relationship between the output density value and the input density value.

  The storage unit 50 is composed of a magnetic or optical recording medium, a semiconductor memory, or the like. In addition to the basic operation program and the print program that can be executed by the control unit 60, the screen setting processing program and the γ correction table update according to the present invention. Various programs such as a processing program and data processed by each program are stored.

  Further, the storage unit 50 stores screen tables of M types of screens prepared in advance in the image processing apparatus 10 and stores a γ correction table corresponding to each screen in an updatable manner. Also, correction images for each color Y, M, C, and K necessary for updating the γ correction table are stored. Further, various LUTs such as a density conversion table and a PWM γ correction table used in the image processing unit 30 are stored.

  The storage unit 50 also includes a screen setting table 51. The screen setting table 51 is a table for storing setting information of N types of screens selected as screens usable at the time of printing from among the M types of screens. As shown in FIG. For each screen number to be used, the type of screen (for example, “resolution priority line screen”, etc.) and a use flag (for example, “ON”) indicating whether or not N types of usable screens are set. Indicates that the screen has been set to be used, and “OFF” indicates that the screen has been set not to be used.), Γ correction information (for example, a γ correction table for each color corresponding to the screen) Name “LUT1Y to 1K”, etc.) and update information of the γ correction table (for example, information of last update date “200 × year Δmonth Δday... Each item information of ", etc.) is stored.

  The control unit 60 includes a CPU (Central Processing Unit) and the like, and controls printing operations performed by the respective units of the image processing apparatus 10 according to a printing program stored in the storage unit 50. In addition, the control unit 60 executes a screen setting process and a γ correction table update process, which will be described later, in accordance with a screen setting process program and a γ correction table update process program stored in the storage unit 50.

  In the screen setting process, when N types of screens set to be usable at the time of printing among the M types of screens prepared in advance by the image processing apparatus 10 are selected via the operation unit 12, Then, the use flag of the N types of screens is set to ON. When selecting one type of screen to be used for printing during printing, only N types of screens whose use flag is set to ON can be selected.

  In the γ correction table update processing, when N screens selected as usable screens in the screen setting processing satisfy a predetermined condition for updating the γ correction table, γ correction tables corresponding to the N types of screens are displayed. Newly created and updated and stored in the storage unit 50. The predetermined condition is, for example, a case in which a predetermined period has elapsed since the previous update, a predetermined condition such as a predetermined number of sheets being printed, or the like is satisfied.

Next, the operation in the present embodiment will be described.
FIG. 9 is a flowchart for explaining a screen setting process executed by the image processing apparatus 10.
In the screen setting process shown in FIG. 9, first, a basic operation screen (not shown) is displayed on the display unit 13 (step S1). When an environment setting item is selected on this basic screen operation screen, various environment settings are made. A setting mode screen (see FIG. 10A) that can be displayed is displayed on the display unit 13 (step S2).

  In the setting mode screen shown in FIG. 10A, among the M types of screens prepared in advance in the image processing apparatus 10 (M is an integer and 0 <M), it can be selected at the time of printing. Items a1 and a2 for selecting N types of screens to be displayed are displayed. In FIG. 10 (a), a total of four types (M = 4) of screens in which two patterns of resolution priority and gradation priority are prepared for the line screen and the dot screen are prepared in the image processing apparatus 10 in advance. An example in which N types are selected from these four types will be shown. Further, a cursor key a3 for selecting an item, a setting change key a4 for inputting a setting change instruction, and an end key a5 for ending the setting are displayed at the bottom of the screen.

  When changing the screen setting, the operator operates the cursor key a3 with the operation unit 12 to select the item a1 on the line screen and the item a2 on the dot screen, and presses the setting change key a4. The screen settings of the items selected each time the setting change key a4 is pressed are “resolution priority ON, gradation priority ON”, “resolution priority ON, gradation priority OFF”, “resolution priority OFF, gradation priority ON”. , “Resolution priority OFF, gradation priority OFF”, and when the setting change key a4 is pressed four times, the original setting is restored. The operator switches to the setting to be changed with the setting change key a4, and presses the end key a5 if the setting is acceptable.

  When N types of screens (N is an integer and N ≦ M) are selected by the operator via the operation unit 12 among the M types of screens on the setting mode screen (step S3). In the screen setting table 51 of the storage unit 50, the use flag corresponding to the selected N types of screens is set to ON.

  For example, in the setting mode screen shown in FIG. 10A, “resolution priority ON, gradation priority OFF” is selected in the item a1 of the line screen, and “resolution priority OFF, gradation priority ON” is selected in the item a2 of the dot screen. "Is selected, N = 2 types of screens are selected from the M = 4 types of screens.

  Next, it is determined whether or not the end key a5 is pressed and the setting end is instructed (step S4). When the setting end is not instructed (step S4; N), the process returns to the process of step S3 and the screen selection is continued. On the other hand, when an instruction to end the setting is given (step S4; Y), it is determined whether or not the update state of the γ correction table corresponding to the selected N types of screens satisfies a predetermined condition for performing the next update. (Step S5). The predetermined condition is, for example, a condition that a predetermined number of sheets have been printed since the γ correction table was last updated, a predetermined period has elapsed, or environmental conditions (temperature difference, humidity difference, etc.) have changed significantly. .

  When the update state of the γ correction table satisfies the predetermined condition (step S5; Y), the γ correction table corresponding to the N types of screens selected by the control unit 11 is updated (step S). After the update is completed, the basic operation screen is displayed again on the display unit 13 (step S7), and this process ends. On the other hand, if the updated state of the γ correction table does not satisfy the predetermined condition (step S5; N), the process proceeds to step S7 without updating the γ correction table, the basic operation screen is displayed again, and this processing is performed. Exit.

  After setting the screen, when setting one type of screen used for printing at the time of printing, a screen selection screen as shown in FIG. 10B is displayed, and only the N types of screens selected in the screen setting processing are displayed. Is displayed as selectable. For example, when “resolution priority ON, gradation priority OFF” is set on the line screen and “resolution priority OFF, gradation priority ON” is set on the dot screen in the screen setting process, as shown in FIG. On the screen selection screen, a resolution-priority line screen and a tone-priority dot screen are displayed in a selectable manner. The other screens are shaded and disabled.

Next, the γ correction table update process will be described with reference to FIG.
This γ correction table update process is a process of updating the γ correction table corresponding to each screen in accordance with the change in the output characteristics of the image processing apparatus 10. In the following description, a case where update is performed for the Y color will be described as an example, but the same processing is performed for each of the colors Y, M, C, and K.

  In the γ correction table update process shown in FIG. 11, first, a Y correction image is read from the storage unit 50 (step S <b> 101) and output to the image processing unit 30. Further, the screen table of the screen whose use flag is set to ON in the screen setting table 51 is read from the storage unit 50 and output to the image processing unit 30.

  The image processing unit 30 performs screen processing on the correction image using the input screen table (step S102). Next, the PWM γ correction table is read from the storage unit 50, and PWM correction processing is performed on the correction image screen-processed using the PWM γ correction table. The image signal of the Y correction image that has been subjected to the PWM correction processing is output to the printer unit 40 as an exposure image signal.

  In the printer unit 40, laser light is emitted from the exposure unit 31Y based on the image signal of the Y correction image input from the image processing unit 30, and an electrostatic latent image of the correction image is formed on the photosensitive drum 33Y. . Next, toner is attached to the photosensitive drum 33Y by the developing device 32Y, and a toner image is formed on the photosensitive drum 33Y (step S103). Next, when the toner image is transferred onto the transfer belt 34, the photosensor F emits light to the toner image of the correction image transferred onto the transfer belt 34 in accordance with an instruction from the control unit 11. The amount of reflected light is measured. The measurement result is output to the control unit 11. (Step S104).

  In the control unit 11, the reflected light amount value measured by the photosensor F is log-converted and converted into a density value. Then, with the density value of each patch of the correction image as the input density value and the density value obtained by the measurement as the output density value, the output density value with respect to the input density value of the correction image is plotted as shown in FIG. A measurement curve is calculated. Then, a curve having a reverse characteristic of the measurement curve with respect to the straight line indicating the target gradation is created as the γ correction curve (step S105). Next, a γ correction table (one-dimensional LUT) in which the generated γ correction curve is tabulated is created, and this γ correction table is updated and stored in the storage unit 50 (step S106).

  The above processing is performed for each color Y, M, C, and K, and a γ correction curve for each color corresponding to the screen used for printing is created. Then, when γ correction tables are created for all the colors Y, M, C, and K and updated and stored in the storage unit 50, the present process is terminated.

  As described above, according to the present embodiment, when N types of screens are selected from the M types of screens prepared in advance, the γ correction table is set for the N types of screens. If the conditions for updating are satisfied, a new γ correction table is created and updated only for the selected N types of screens, so that the time required for updating can be shortened. Also, by selecting the frequently used screen as the N types of screens, the γ correction table is updated only for the frequently used screens, so that waste of materials and energy consumption for updating can be saved. it can. Therefore, the γ correction table can be updated efficiently.

  In addition, by setting a condition for updating the γ correction table, the update can be performed at an appropriate timing.

  Further, when selecting a screen to be used for printing at the time of printing, only N types of screens set as usable screens are displayed to be selectable. Therefore, it is possible to prevent a screen having a low correction accuracy from being selected because the γ correction curve has not been updated.

  The description content in the present embodiment is a preferred example of the image processing apparatus 10 to which the present invention is applied, and is not limited to this.

  For example, in the above description, when N types of screens are selected, the γ correction table is updated only when a predetermined condition for updating the γ correction table is satisfied. Instead, the γ correction table corresponding to the N types of screens selected when the N types of screens are selected may be updated.

  In addition, the detailed configuration and detailed operation of the image processing apparatus 10 in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is a figure which shows the internal structure of the image processing apparatus 10 in this Embodiment. 4 is a diagram illustrating a flow of image processing by an image processing unit 30. FIG. It is a figure which shows a density | concentration conversion table. It is a figure which shows the image density characteristic at the time of the gamma correction process using a gamma correction table. It is a figure which shows the image density characteristic at the time of the PWM correction process using a PWM (gamma) correction table. It is a figure which shows the mode of the measurement of the reflected light amount by the photosensor. It is a figure which shows an example of the image for a correction | amendment. It is a figure which shows the data structural example of the screen setting table 51. FIG. 4 is a flowchart for explaining a screen setting process executed by the image processing apparatus 10. 5 is a flowchart for explaining a γ correction table update process executed by the image processing apparatus 10. (A) It is a figure which shows an example of a setting mode screen. (B) It is a figure which shows an example of a screen selection screen. It is a figure which shows the gamma correction curve calculated from a measurement curve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image processing apparatus 11 Image scanner 12 Operation part 13 Display part 20 Main part 30 Printer part 31Y, 31M, 31C, 31K Exposure unit 32Y, 32M, 32C, 32K Developer 33Y, 33M, 33C, 33K Photosensitive drum 34 Transfer belt 35 Cleaning unit 36 Transfer roller 37 Fixing unit 40 Image processing unit 50 Storage unit 51 Screen setting table 60 Control unit

Claims (4)

An image processing unit that screen-processes the correction image using a screen for reproducing the halftone of the image;
A printer unit for forming a toner image of the correction image subjected to the screen processing;
A sensor for measuring the density value of the toner image;
A control unit that creates a γ correction curve having a reverse characteristic of the density value measured by the sensor with respect to the target gradation, creates a γ correction table by tabulating the γ correction curve, and
A storage unit that stores M types of screens used by the image processing unit and a γ correction table created for each of the M types of screens;
When updating the gamma correction table of each screen stored in the storage unit, screen processing by the image processing unit using the N types of screens selected from the M types of screens by the user, the printer unit An image processing apparatus that forms a toner image by the sensor and performs measurement by the sensor, creates a new γ correction table for each of the N types of screens by the control unit, and updates and stores it in the storage unit. The control unit for the selected N types of screens, when the condition for updating the γ correction table is satisfied, characterized by creating a new γ correction table against the corresponding N type screen The image processing apparatus according to claim 1. When one of the N types of screens used for printing is selected by the user during printing , the image processing unit uses a γ correction table corresponding to the selected one type of screen. performs γ correction of the print target image, the image processing apparatus according to claim 1 or 2, characterized by applying screen processing using the one screen.   The image processing apparatus according to claim 1, wherein only the N types of screens can be selected during printing.

Images