JP2011110825A - Image forming apparatus, printing system, and control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus, a printing system and a control program that can efficiently carry out print processing. <P>SOLUTION: The image forming apparatus carries out calibration for correcting a shift of primary colors of Y, M, C. K at predetermined timing. A control part in the image forming apparatus discriminates the color of each pixel in image data to be printed, and performs control of carrying out print processing based on the image data without performing calibration even in the performing time of calibration when all the pixels are composed of only the primary colors. The control part further discriminates printing classification based on tag information added to the data of pixels when there are the pixels of neutral colors obtained by combining two or three colors of Y, M, C, K, comverts the neutral color into the color selected out of the two or three colors in the case of text printing, and carries out print processing based on the image data without performing calibration. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that performs calibration at a predetermined timing, a printing system including the image forming apparatus, and a control program that operates on the image forming apparatus.

  Image forming apparatuses such as copiers and multi-function peripherals (MFPs) having a color printing function are widespread. In this image forming apparatus, an image is formed based on the print data, an electrostatic latent image is formed by irradiating the charged photosensitive drum with light according to the image, and the charged toner is attached and developed. The toner image is transferred to a sheet via an intermediate transfer member such as a transfer roller or a transfer belt.

  In the image forming apparatus, the image creation process parameters such as the charge amount, the development voltage, the density, and the light amount change due to changes in temperature and humidity in the apparatus and deterioration of parts such as the photosensitive drum and developer. In particular, in the case of color printing, since an intermediate color is created by superimposing primary colors, the image quality deteriorates due to the primary color shift. For this reason, every time a certain number of prints are performed, the above parameters are adjusted and a process (calibration) for correcting a primary color shift is performed.

  Regarding this calibration, for example, in Patent Document 1 below, prior to a color image forming operation, a mark of each color is formed on a photoconductor, and a plurality of scanning exposure means are obtained based on deviation information obtained from the mark. The synchronizing means for synchronizing the other horizontal synchronizing signal with the reference horizontal synchronizing signal output from the one horizontal synchronizing signal output means, and synchronizing the reference horizontal synchronizing signal and the image leading edge signal, and the reference horizontal synchronizing signal Based on the adjustment means for adjusting the scanning start of the scanning exposure means, the positional deviation adjustment for each scanning line is performed by adjusting between the horizontal synchronization signal and the image area signal, and the positional deviation adjustment for less than one line is performed. A color image forming apparatus that adjusts by changing the phase of a driving clock of a rotary polygon mirror is disclosed.

JP 2001-88347 A

  The calibration is a process necessary for preventing a primary color shift and forming a high-quality color image. However, in order to perform the calibration, the printing process must be interrupted, Since the calibration takes a predetermined time, the printing process is delayed. On the other hand, there are various print contents. For example, when it is not necessary to superimpose images of each color as in the case of printing only one color, it is not always necessary to perform calibration before printing.

  Therefore, it is important to consider the print contents in order to maintain both image quality and efficient print processing. Conventionally, however, calibration is performed when the number of printed sheets reaches a specified number regardless of the print contents. Therefore, there has been a problem that the printing process cannot be executed efficiently.

  The present invention has been made in view of the above problems, and a main object thereof is to provide an image forming apparatus, a printing system, and a control program capable of efficiently executing a printing process.

  In order to achieve the above object, the present invention provides an image forming apparatus that performs calibration for correcting a primary color shift of Y, M, C, and K at a predetermined timing. If the color of each pixel of the image data is determined and all the pixels are composed only of the primary color, the printing process based on the image data without performing the calibration even at the time of performing the calibration. The control which performs is performed.

  In the present invention, when there is an intermediate color pixel that superimposes two or three colors of Y, M, C, and K, the control unit sets the print type based on Tag information added to the data of the pixel. In the case of text printing, the intermediate color is converted to a color selected from the two or three colors, and the printing process based on the image data is executed without performing calibration. it can.

  According to the present invention, in a printing system including the image forming apparatus and a print instruction apparatus that operates a printer driver, the printer driver determines whether or not to perform the conversion when intermediate colors are included in text printing. A screen to be selected by the user is displayed, and the selection result on the screen is notified to the image forming apparatus. When the control unit of the image forming apparatus is selected to perform the conversion, the intermediate color Conversion is performed.

  Also, the present invention operates with an image forming apparatus that performs calibration for correcting a primary color shift of Y, M, C, and K at a predetermined timing, or a control device that controls the image forming apparatus. If the image forming apparatus or the control apparatus determines the color of each pixel of the image data to be printed and all the pixels are composed of only the primary color, the control program Even if it is the execution time, it is made to function as a control unit that executes a printing process based on the image data without performing calibration.

  According to the image forming apparatus, the printing system, and the control program of the present invention, the printing process can be executed efficiently.

  The reason is that in the image forming apparatus, when all the pixels of the image data to be printed do not have an intermediate color (the primary colors (Y, M, C, K) are not superimposed), the calibration is performed. This is because control for executing the printing process is performed without performing calibration.

  In addition, even when there is an intermediate color, in the case of text printing, control is performed to convert to a primary color (Y, M, C, K single color or M + Y, C + Y) and execute the printing process without performing calibration. It is because it performs.

1 is a diagram illustrating a configuration of a printing system according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of a print instruction apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a flowchart figure which shows the printing procedure (whole procedure) which concerns on one Example of this invention. It is a figure which shows the data structure of each pixel of the image data which concerns on one Example of this invention. It is a flowchart figure which shows the printing procedure (procedure which determines the presence or absence of an intermediate color) which concerns on one Example of this invention. It is a flowchart figure which shows the printing procedure (procedure which determines printing classification) based on one Example of this invention. It is a flowchart figure which shows the printing procedure (procedure which converts an intermediate color into a primary color) which concerns on one Example of this invention. FIG. 6 is a diagram illustrating an example of a setting screen (property screen) displayed by a printer driver that operates in a print instruction apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a setting screen (color profile setting screen) displayed by a printer driver that operates in a print instruction apparatus according to an embodiment of the present invention.

  As shown in the background art, in the image forming apparatus, intermediate colors are created by superimposing primary colors. To form a high-quality color image while suppressing the primary color deviation, calibration is performed periodically. Needs to be done.

  In this calibration, for example, Y-, M-, C-, and K-shaped marks are formed on the passing lines of two sensors arranged on the transfer belt, and a total of 8 sensors are formed by the two sensors. Detect and output marks. Then, by counting the clocks until the rise of the output pulse of each color, the exposure position shift amount (difference) of each slave scanning exposure unit with respect to the master scanning exposure unit is calculated, and slave exposure is performed with reference to the master scanning exposure unit. The inclination of the means, the main scanning magnification, the main scanning start point, and the sub scanning start point are obtained. Thereafter, the CPU adjusts the timing and phase using the data of the tilt amount, the main scanning magnification, the main scanning start point, and the sub-scanning start point.

  As described above, in the calibration, an image for calibration (for example, a U-shaped mark) is formed on the transfer belt. Therefore, the printing process must be interrupted during the calibration. , The printing process is delayed. Therefore, with the conventional method of periodically performing calibration, it is impossible to achieve both maintenance of image quality and efficient printing processing.

  On the other hand, paying attention to the contents of printing, since there is almost monochrome printing in the case of only the primary color having no intermediate color, there is no need to perform calibration. In the case of color text printing, there is no substantial problem even if the color changes slightly, and the calibration can be omitted by converting the intermediate color to a near primary color.

  Therefore, in an embodiment of the present invention, an image forming apparatus that executes calibration at a predetermined timing determines the color of each pixel of image data generated from print data, and all the pixels are composed of only primary colors. If it is, the printing process based on the image data is executed without performing the calibration even when the calibration is performed. In addition, when an intermediate color pixel that overlaps two or more colors is included, the print type is determined based on Tag information or the like, and in the case of text printing, the process of converting the intermediate color into a close primary color is performed. Perform calibration and omit calibration. As a result, it is possible to efficiently execute print processing while preventing deterioration of image quality due to not performing calibration.

  In order to describe the above-described embodiment of the present invention in more detail, an image forming apparatus, a printing system, and a control program according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram schematically illustrating a configuration of a printing system according to the present embodiment. FIG. 2 is a block diagram illustrating the configuration of the print instruction apparatus, and FIG. 3 is a block diagram illustrating the configuration of the image forming apparatus. 4 and 6 to 8 are flowcharts showing a printing procedure in the image forming apparatus, and FIG. 5 is a diagram showing a data configuration of each pixel of the image data. 9 and 10 are diagrams illustrating an example of a setting screen displayed by a printer driver that operates in the print instruction apparatus according to the present exemplary embodiment.

  As shown in FIG. 1, the printing system of this embodiment receives a print data from a client computer device (referred to as a print instruction device 10) that transmits print data and instructs printing, and executes printing by receiving the print data. The image forming apparatus 20 includes a LAN (Local Area Network) and a WAN (Wide Area Network) defined by standards such as Ethernet (registered trademark), token ring, and FDDI (Fiber-Distributed Data Interface). They are connected by a communication network 30. Hereinafter, each device will be described in detail.

[Printing instruction device]
As shown in FIG. 2, the print instruction apparatus 10 includes a control unit 11, a display unit 12, an operation unit 13, and the like.

  The control unit 11 includes a CPU (Central Processing Unit) 11a, a ROM (Read Only Memory), a memory 11b such as a RAM (Random Access Memory), an HDD (Hard Disk Drive) 11c, a communication I / F unit 11d, and the like. Are connected via a bus. The CPU 11a controls each part. The memory 11b is a part that temporarily stores various data read from the HDD 11c and the communication I / F unit 11d, and the stored data is processed by the CPU 11a, and the HDD 11c and the communication I / F unit 11d as necessary. Forwarded to The HDD 11c stores a program for the CPU 11a to control each unit, information on processing functions of the own device, print data, and the like, read by the CPU 11a as necessary, and executed on the memory 11b. The communication I / F unit 11d establishes a connection with a device connected via the communication network 30, and executes transmission / reception of data.

  The control unit 11 functions as an application for creating a document and a printer driver for instructing printing of the document. Document data created by the application can be read by a language (PCL (PCL) readable by the image forming apparatus 20 by the printer driver. It is converted into PDL (Page Description Language) print data such as Printer Control Language (PS) or PS (Post Script), and is transmitted to the image forming apparatus 20 via the communication I / F unit 11d.

  The display unit 12 includes a liquid crystal display (LCD), an organic EL (electroluminescence) display, and the like, and displays a printer driver property screen and the like.

  The operation unit 13 includes a pointing device, a keyboard, a trackball, a trackpad, a tablet, a stylus pen, and the like. Various settings and instructions (for example, whether to convert an intermediate color to a primary color in the case of text printing) Instructions).

  FIG. 2 shows a basic configuration of the print instruction apparatus 10, and as long as a printer driver that instructs the image forming apparatus 20 to execute printing can be executed, the configuration can be changed as appropriate.

[Image forming apparatus]
As shown in FIG. 3, the image forming apparatus 20 includes a control unit 21, an ADF (Auto Document Feeder) 22, an image reading unit 23, a display unit 24, an operation unit 25, and paper feeding. A unit 26, an image forming unit 27, a post-processing unit 28, and the like.

  The control unit 21 controls each component, and includes a CPU 21a, a memory 21b such as a ROM and a RAM, an HDD 21c, a communication I / F unit 21d, and the like, which are connected via a bus. The CPU 21a controls each part. The memory 21b is a part that temporarily stores various data read from the HDD 21c, the image reading unit 23, and the communication I / F unit 21d. The stored data is subjected to image processing by the CPU 21a, and the HDD 21c or image is stored as necessary. Transferred to the forming unit 27. The HDD 21c is a program for the CPU 21a to control each unit, information on the processing function of its own device, conditions for determining the calibration execution time (for example, a threshold value for the number of prints), a table for associating the tag bit value with the print type, etc. Is read out as needed by the CPU 21a and executed on the memory 21b. The communication I / F unit 21d establishes a connection with a device connected via the communication network 30, and executes data transmission / reception.

  The control unit 21 rasterizes each page of the print data received from the print instruction apparatus 10 to generate image data for each page, performs screening, and then converts the data into printable data by the image forming unit 27. Also, the calibration execution time is determined based on the number of printed sheets.

  Further, the control unit 21 determines that each pixel of the image data for each page is only a primary color (that is, a single color of Y, M, C, and K) or an intermediate color (that is, Y, M, C, and K). If all the pixels are composed of only the primary color, it is based on the image data without performing calibration even when the calibration is performed. Control to execute the printing process. When the pixel is an intermediate color, the print type (text printing, graphic printing, or photo printing) is determined based on Tag information or the like. In the case of text printing, the intermediate color is a primary color close to the color or ( Y + M) or (Y + C), and control is performed so that calibration is not performed. This control may be executed as hardware or may be executed as software (control program).

  The ADF 22 is a part that automatically conveys one or a plurality of document sheets to the image reading unit 23.

  The image reading unit 23 is a part that optically reads image data from a document sheet on a document table, a light source that scans the document, a CCD (Charge Coupled Devices) that converts light reflected by the document into an electrical signal, and the like. Image sensor and an A / D converter for A / D converting electrical signals.

  The display unit 24 includes a liquid crystal display device, an organic EL display device, and the like, and displays a screen and the like for operating the image forming apparatus 20. The operation unit 25 includes buttons, switches, and the like, and performs various settings and instructions (for example, an instruction on whether to convert an intermediate color to a primary color in the case of text printing). The display unit 24 and the operation unit 25 may be separate devices, or may be an integrated device provided with a pressure-sensitive operation unit (touch panel) 25 in which transparent electrodes are arranged in a lattice shape on the display unit 24. In the case of a touch panel, the XY coordinates of a force point pressed with a finger or a touch pen are detected by a voltage value, and the detected position signal is output to the control unit 21 as an operation signal.

  The paper feed unit 26 includes a paper tray for storing various sizes of paper. Further, a part for sending the stored paper to the image forming unit 27 is included.

  The image forming unit 27 includes constituent elements necessary for image formation using an image forming process such as an electrophotographic method or an electrostatic recording method, and image data read from the image reading unit 23 or a communication I / F unit 21d. On the basis of the image data generated from the print data received via, an image is formed on the designated paper and sent to the post-processing unit 28. Specifically, an electrostatic latent image is formed on a uniformly charged photosensitive drum by irradiating light according to image data, and charged toner is attached to the electrostatic latent image to form a toner image. The toner image is visualized, and the toner image is transferred to a sheet via an intermediate transfer member such as a primary transfer roller and a secondary transfer belt, and then the toner image is heated and pressed to be fixed on the sheet.

  The post-processing unit 28 performs processing such as stapling and punching on the sheet conveyed from the image forming unit 27 according to an instruction from the control unit 21 and outputs the result.

  3 is an example of the image forming apparatus 20, and the configuration thereof can be changed as appropriate. For example, when the print process is executed based on the print data transmitted from the print instruction apparatus 10, the ADF 22 and the image reading unit 23 may be omitted, and when the post-process is not necessary, the post-processing unit 28 is omitted. May be.

  In FIG. 1, the printing system includes the print instruction apparatus 10 and the image forming apparatus 20. However, a control apparatus such as a RIP (Raster Image Processor) controller that converts print data into image data is connected to the communication network 30. In that case, the processing performed by the control unit 21 of the image forming apparatus 20 may be executed by the control apparatus. Further, when the printing process is performed based on the image data read by the image reading unit 23 of the image forming apparatus 20, the print instruction apparatus 10 can be omitted.

  Hereinafter, the operation of the image forming apparatus 20 in the printing system having the above configuration will be described with reference to the flowcharts of FIGS. 4 and 6 to 8. 4 shows the overall operation, and FIGS. 6 to 8 show the individual operations of FIG.

  As shown in FIG. 4, the image forming apparatus 20 receives print data in which color information of each pixel is described in RGB from the print instruction apparatus 10 (S100). When image data read by the image reading unit 23 of the image forming apparatus 20 is used, the image reading unit 23 may read the original and acquire the image data.

  Next, the control unit 21 performs color conversion for converting received or acquired data into image data suitable for printing (S110). For example, color information (RGB) that depends on the print instruction apparatus 10 is converted into color information (Lab) that does not depend on the apparatus using an ICC (International Color Consortium) profile, and then color information (Lab that depends on the image forming apparatus 20 (Lab). CMYK). Each pixel of the image data thus converted includes, for example, 2-bit Tag information (data for determining whether the print type is text printing, graphic printing, or photo printing), as shown in FIG. It consists of 8-bit CMYK data. Note that the color conversion method is not limited to the above. For example, color information depending on the input device may be directly converted into color information depending on the output device. Further, the data structure of the pixel is not limited to that shown in FIG. 5, and it is sufficient that the information specifying the print type and the information of each color are included.

  Next, the control unit 21 sequentially extracts one pixel from the image data (S120), and determines whether the pixel is composed of only primary colors (Y, M, C, K) (S130). This step will be described in detail with reference to FIG.

  First, it is determined whether the Y data is 0 (S131). If the Y data is not 0, it is determined whether the M, C, and K data are 0 (S135). If all the data is 0, it is determined that the color is the primary color because it is only Y. (S138). On the other hand, if any of the data is not 0, it is determined as an intermediate color (S139).

  If the Y data is 0, it is determined whether the M data is 0 (S132). If the M data is not 0, it is determined whether the C and K data are 0 (S136). If all the data is 0, since it is only M, it is determined to be the primary color (S138). ). On the other hand, if any of the data is not 0, it is determined as an intermediate color (S139).

  If the M data is 0, it is determined whether the C data is 0 (S133). If the C data is not 0, it is determined whether the K data is 0 (S137), and if the K data is 0, since it is only C, it is determined to be the primary color (S138). On the other hand, if the K data is not 0, it is determined as an intermediate color (S139).

  If the C data is 0, it is determined whether the K data is 0 (S134). If the K data is 0, there is no color, so it is determined as the primary color (S138). On the other hand, when the data of K is not 0, since it is only K, it is determined as the primary color (S138).

  Returning to FIG. 4, when the pixel data is not only the primary color (that is, in the case of an intermediate color), the control unit 21 checks whether it can be converted to a near primary color, for example, text printing. (S140). This step will be described in detail with reference to FIG. Note that the value of the tag bit and the print type are “00” associated with text printing, “01” associated with graphic printing, and “10” or “11” associated with photo printing. It is described and stored in advance in the memory 21b or the HDD 21c.

  First, it is determined whether the two bits of Tag are “00” (S141). If it is “00”, it is determined that the text printing is performed (S143). If it is not “00”, it is determined whether the two bits of Tag are “01” (S142). If it is “01”, it is determined that the graphic printing is being performed (S144), and “10” or “11”. In this case, it is determined that the print is a photo print (S145).

  Returning to FIG. 4 again, if the result of determination in S140 is text printing, the control unit 21 converts the intermediate color to the primary color (S150). This step will be described in detail with reference to FIG. In this state, the primary colors overlap with two or three colors.

  First, it is determined whether the primary colors overlap with each other (S151). In the case of No (that is, in the case of overlapping with three colors), it is determined whether the overlap is (Y + M + K) or (Y + C + K) or (M + C + K) (S152). In any case, since K is dominant, only K data (data with bits of colors other than K set to 0) is output (S153). On the other hand, when none of them corresponds (that is, when K is not included), the data of the respective colors are compared and the dominant color data is output (S154). For example, Y, M, and C data may be compared as dominant colors, and data of a color having the largest bit value (data in which bits other than that color are set to 0) may be output. Is an inconspicuous color, so to reproduce a color closer to the original intermediate color, the data of M and C are compared, and the data of the color with the larger bit value + Y data is output. Also good.

  If Yes in S151 (overlapping with two colors), it is determined whether the overlap is (Y + M) or (Y + C) (S155). If either of these is true, Y is a color that is inconspicuous visually, so the data of two colors is output as it is (S159). Note that only M or C data may be output. On the other hand, if neither of them corresponds (that is, if K is included), it is determined whether the overlap is (Y + K), (M + K), or (C + K) (S156). In any case, since K is dominant, only K data is output (S157). On the other hand, if it does not correspond to any of these, it is (M + C), so the data of the dominant color, for example, the data of the color with the larger bit value is output by comparing the data of M and C ( S158).

  In this embodiment, in the case of text printing, the intermediate color is converted into a close primary color or (Y + M) or (Y + C), but it may be preferable to faithfully reproduce the original color. In consideration of such a case, the user can select whether or not to convert the intermediate color to the primary color when the print instruction apparatus 10 instructs printing. For example, when the “color management” tab is selected on the printer driver property screen 40 as shown in FIG. 9, a color profile setting screen 41 as shown in FIG. 10 is displayed. In this case, a means (a radio button in a broken line in the figure) for selecting whether or not to convert the intermediate color to the primary color is provided, and the selection result is embedded in the print data and transmitted to the image forming apparatus 20. Then, the image forming apparatus 20 may execute S150 (processing for converting to the primary color) based on the selection result.

  Similarly, on the screen displayed on the panel of the image forming apparatus 20, there is provided means for selecting whether or not to convert the intermediate color to the primary color in the case of text printing. Based on the result, S150 (processing for converting to a primary color) may be executed.

  Returning to FIG. 4 again, if the data is not only the primary color (No in S130) and is not text printing (No in S140), the control unit 21 sets a flag indicating that calibration is to be performed. (S160), the process proceeds to S180. On the other hand, when the data is only the primary color (Yes in S130) and when the intermediate color is converted into the primary color (S150), the control unit 21 determines whether there is a next pixel (S170), If there is a next pixel, the process returns to S120 and the same processing is repeated.

  After determining the colors of all the pixels (or after leaving the routine by setting a flag), the control unit 21 executes screen processing (S180).

  Next, the control unit 21 determines whether or not it is a calibration execution time based on whether or not the number of printed sheets exceeds a threshold value (S190). If it is the calibration execution time, is the above flag set? Is determined (S200). If it is not time to perform calibration (No in S190) or the flag is not set (No in S200), the printing process is executed without performing calibration (S210). On the other hand, if it is time to perform calibration (Yes in S190) and the flag is set (Yes in S200), it is graphic printing or photo printing, and there are pixels of intermediate colors. Print processing is executed (S220).

  As described above, when each pixel of the image data generated from the print data is composed only of the primary color, the image forming apparatus 20 performs control not to perform the calibration even when the calibration is performed. Therefore, the printing process can be executed efficiently. Further, even in the case of including the intermediate color, in the case of text printing, since it is not necessary to calibrate by converting to a near primary color, it is possible to efficiently execute the printing process by omitting the calibration. it can.

  In addition, this invention is not limited to the said Example, The structure and control can be changed suitably, unless it deviates from the meaning of this invention. For example, in the above embodiment, the intermediate color is converted to the primary color or (Y + M) or (Y + C) in the case of text printing. However, in the case of graphic printing, the intermediate color is changed to the primary color or (Y + M) or (Y + C). It is good also as a structure to convert. Even in the case of graphic printing or photo printing, if the graphic or photo is not composed of complex colors (for example, composed of several intermediate colors) or the area of the graphic or photo is small In some cases (for example, when the proportion of the area occupied by graphics or photographs is equal to or less than a threshold value), the intermediate color may be converted into a primary color, (Y + M), or (Y + C).

  The present invention can be used for an image forming apparatus that performs calibration at a predetermined timing, a printing system including the image forming apparatus, and a control program that operates on the image forming apparatus.

DESCRIPTION OF SYMBOLS 10 Print instruction | indication apparatus 11 Control part 11a CPU
11b Memory 11c HDD
11d Communication I / F unit 12 Display unit 13 Operation unit 20 Image forming apparatus 21 Control unit 21a CPU
21b Memory 21c HDD
21d Communication I / F part 22 ADF
DESCRIPTION OF SYMBOLS 23 Image reading part 24 Display part 25 Operation part 26 Paper feed part 27 Image formation part 28 Post-processing part 30 Communication network 40 Property screen 41 Color profile setting screen

Claims (10)

In an image forming apparatus that performs calibration at a predetermined timing to correct a deviation in primary colors of Y, M, C, and K.
The control unit discriminates the color of each pixel of the image data to be printed, and if all the pixels are composed only of the primary color, the calibration is not performed even when the calibration is performed. An image forming apparatus that performs control to execute a printing process based on the image data.   When there is an intermediate color pixel that superimposes two or three colors of Y, M, C, and K, the control unit determines a print type based on Tag information added to the data of the pixel, and prints text. In this case, the intermediate color is converted into a color selected from the two colors or the three colors, and a printing process based on the image data is executed without performing calibration. The image forming apparatus described.   The control unit converts the intermediate color into one color of M or C or two colors of M or C and Y when the three colors are a combination of Y, M, and C. Item 3. The image forming apparatus according to Item 2.   3. The image forming apparatus according to claim 2, wherein when the two or three colors include K, the control unit converts the intermediate color into one color of K. 4. The image forming apparatus displays a screen that allows a user to select whether or not to perform the conversion when intermediate colors are included in text printing,
5. The image forming apparatus according to claim 2, wherein the control unit performs the conversion of the intermediate color when the selection to perform the conversion is performed on the screen. 6. A printing system comprising: the image forming apparatus according to claim 2; and a print instruction apparatus that operates a printer driver.
The printer driver displays a screen that allows a user to select whether to perform the conversion when intermediate colors are included in text printing, and notifies the image forming apparatus of a selection result on the screen;
The printing system according to claim 1, wherein the control unit of the image forming apparatus performs the conversion of the intermediate color when the conversion is performed. A control program that operates on an image forming apparatus that performs calibration for correcting a primary color shift of Y, M, C, and K at a predetermined timing, or a control device that controls the image forming apparatus. ,
The image forming apparatus or the control device;
When the color of each pixel of the image data to be printed is determined and all the pixels are composed of only the primary color, the image data is not calibrated even when the calibration is performed. A control program that functions as a control unit that executes a printing process based on the control program.   When there is an intermediate color pixel that superimposes two or three colors of Y, M, C, and K, the control unit determines a print type based on Tag information added to the data of the pixel, and prints text. In this case, the intermediate color is converted into a color selected from the two or three colors, and a printing process based on the image data is executed without performing calibration. The control program described.   The control unit converts the intermediate color into one color of M or C or two colors of M or C and Y when the three colors are a combination of Y, M, and C. Item 9. The control program according to Item 8.   9. The control program according to claim 8, wherein when the two or three colors include K, the control unit converts the intermediate color into one color of K.

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