JP2015003413A - Printing method, printing control device, program and printing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing method, a printing control device, a program and a printing system in which a printed matter of a desired color can be obtained and image failure, such as a blocking phenomenon etc. due to the piling of printed matters can be prevented in preparing double-sided printed matters.SOLUTION: A first ink quantity distribution is determined from first image data on a first surface of a sheet body and a second ink quantity distribution is determined from second image data on a second surface (S118). In an area of a position relationship where double-sided printed matters are superimposed on each other when the printed matters are piled up, the total ink quantity on both sides showing the summation of the ink quantity of the first surface and the ink quantity of the second surface is determined from the first ink quantity distribution and the second ink quantity distribution (S120), and it is judged whether or not the summation exceeds a specified value. In a case that there is a specific area in which the summation exceeds the specified value, color conversion conditions are changed to the conditions in which the total ink quantity on both sides in the specific area remains within the specified value and an output color is reserved (S126). Color conversion processing on the image data is implemented with the changed color conversion conditions, to implement printing.

Description

  The present invention relates to a printing method, a printing control apparatus, a program, and a printing system, and in particular, when creating a double-sided printed material in which an image is formed on both sides of a sheet-like printing medium (hereinafter referred to as a sheet body). The present invention relates to an image data processing technique for adjusting ink usage.

  When creating double-sided printed matter using a printing device, if image data that uses a large amount of ink is printed, the ink will not be completely fixed on the paper, so that the ink will be transferred to the transport roller during paper transport inside the printing device. Further, there is a problem that the ink is transferred to other printing paper via a roller to contaminate the printed matter (see Patent Document 1).

  In order to prevent such a problem, in Patent Document 1, in order to prevent the printed material from being soiled due to the paper feed roller being soiled, the ink on the front surface and the back surface of the printed material is specified for a specific region corresponding to the pressure contact region of the roller. There have been proposed a printing control method for obtaining the amount and switching the printing order of the front surface and the back surface according to the ink amount on each surface, and a method for limiting the ink ejection amount in the specific area.

JP 2003-320727 A

  In addition to the problem of smearing of printed matter via rollers in the paper transport system due to the use of a large amount of ink, as a problem of double-sided printing, the two-sided printed matter after discharging is stacked between papers that are in contact with each other. There is a problem that the ink is transferred and the printed matter is soiled. In order to avoid ink transfer between the front and back surfaces in such paper stacking (printed material stacking), the printed material is dried at a high temperature after image formation on the paper, and the ink is transferred in the state of paper stacking on the paper discharge side. There are measures to prevent it.

  However, even when this measure is adopted, the paper discharged from the printing device is in a high temperature state, so when a large number of sheets are stacked, it is represented by heat and pressure due to the weight of the paper. A phenomenon called “blocking” occurs in which the ink in the region of a large amount of ink on the back side melts and adheres, and the ink film surface peels off when the paper is pulled out one by one.

  The technique of Patent Document 1 cannot solve the problem of the blocking phenomenon. Further, in the method of limiting the ink discharge amount proposed in Patent Document 1, since the ink discharge amount in a specific danger area is simply dropped, the color of the print image is changed, and a print of a desired color is performed. There is a problem that cannot be obtained.

  The present invention has been made in view of such circumstances, and in creating a double-sided printed material, it is possible to obtain a printed material of a desired color, and to prevent image defects caused by stacking of printed materials such as blocking phenomenon. An object of the present invention is to provide a printing method, a printing control apparatus, a program, and a printing system.

  In order to achieve the above object, a printing method according to the present invention is a printing method in which images are formed on both front and back sides of a sheet body by a printing apparatus to create a double-sided printed material. A step of obtaining a first ink amount distribution indicating a distribution of the ink amount on the first surface from the first image data to be printed on the first surface, which is a surface, and a first side of the sheet body opposite to the first surface on the front and back sides. A step of obtaining a second ink amount distribution indicating a distribution of the ink amount on the second surface from the second image data to be printed on the two surfaces, and the first surface and the first surface that are in contact with each other when a plurality of double-sided printed materials are overlaid. Obtaining a double-sided total ink amount indicating the sum of the ink amount on the first surface and the ink amount on the second surface from the first ink amount distribution and the second ink amount distribution for the overlapping positional relationship between the two surfaces; Total ink volume on both sides exceeds the specified value If there is a specific area where the total amount of ink on both sides exceeds the specified value, the total amount of ink on both sides of the specific area falls within the specified value, and the output color is A step of setting a color conversion condition to be stored; a step of performing color conversion processing on image data of at least one of the first surface and the second surface using the set color conversion condition; and Forming an image on a sheet body by a printing apparatus using the obtained image data.

  According to the present invention, distribution of ink usage amounts (first ink amount distribution, second ink amount distribution) on the front surface and the back surface from image data (first image data, second image data) to be printed. ) And the total ink amount on both sides is obtained in a positional relationship area where the front and back sides overlap. If the total amount of ink on both sides exceeds the specified value, change the color conversion conditions so that the sum of the ink amounts in the specified specific area is within the specified value, and the output color is saved. . By performing the color conversion process of the image data using the changed color conversion condition, the total ink amount on both sides is suppressed within the specified value, and the print color is corrected to the stored image data. By performing image formation with the printing apparatus using the image data obtained in this way, the total amount of ink on both sides can be suppressed within a specified value without changing the color of the printed matter, and an image such as blocking can be obtained. The occurrence of defects can be avoided.

  “Saving the output color” includes that the change in color tone in the printed image is within an acceptable range that can be substantially ignored. In order to adjust the ink usage so that the total amount of ink on the first and second sides is within a specified value by correcting the image data so that the color does not change as much as possible, for example, cyan (C) , A GCR (Gray-Component Replacement) processing method for replacing a gray color reproduced by a combination of magenta (M) and yellow (Y) with black (K) can be applied.

  Other aspects of the invention will become apparent from the description of the present specification and the drawings.

  According to the present invention, in producing a double-sided printed material, it is possible to obtain a printed material having a desired color, and it is possible to prevent image defects due to the stacking of printed materials such as blocking phenomenon. For this reason, it is possible to create a good double-sided printed matter with no printing defects.

1 is a block diagram illustrating a configuration example of a printing system according to an embodiment of the present invention. Flow chart showing the flow of processing when calculating the ink amount distribution from image data Explanatory drawing which shows an example of image reduction processing Main block diagram relating to color conversion processing in a computer terminal (PC) Conceptual diagram showing an example of image conversion processing in the gradation conversion unit Explanatory drawing of the correction process in a nonuniformity correction process part The figure which shows an example of the halftone dot ratio implement | achieved by halftone processing Explanatory diagram schematically showing the procedure for creating ink amount distribution data from reduced image data Schematic diagram for explaining the overlapping positional relationship between the front and back surfaces Conceptual diagram of the data structure of printing condition information stored in the printing condition database A flowchart showing a flow of optimization processing of the total ink amount on both sides according to the present embodiment. The figure which shows the example of the user interface (UI) operation screen for selecting a print job The figure which shows the example of UI operation screen for performing the condition setting regarding the change of an ink amount The figure which shows the example of UI operation screen which displays the confirmation result of an ink amount The flowchart which showed the flow of the whole process at the time of producing a double-sided printed matter with the printing system of this embodiment. Flow chart showing the contents of the double-sided total ink amount optimization process Flow chart showing the contents of the double-sided total ink amount optimization process Flow chart showing the flow of print processing A flowchart showing an example of a procedure for generating a non-uniformity correction LUT Diagram showing an example of a test chart for concentration measurement Overall configuration diagram of inkjet recording apparatus 22A is a plan perspective view showing a structural example of the head, and FIG. 22B is an enlarged view of a part thereof. Plane perspective view showing another structural example of the head Sectional drawing which follows the AA line in Fig.22 (a)

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Configuration example of printing system>
FIG. 1 is a block diagram illustrating a configuration example of a printing system according to an embodiment of the present invention. The printing system 10 includes a single-pass inkjet printer 12 (hereinafter referred to as “printer 12”) as a printing apparatus, and a computer terminal 14 (hereinafter referred to as “PC 14”) as a print control apparatus that controls the printer 12. .), A monitor 16 as a display unit, and an input device 18 as an operation unit.

  The PC 14 is connected to the printer 12 by wire or wireless. The PC 14 has a function of managing image data, a function of processing image data, and a function of managing and providing parameters for image processing. That is, the PC 14 functions as a printer control unit, and also functions as an image data management unit, an image data processing unit, an image processing parameter management unit, and an image processing parameter providing unit.

  A monitor 16 and an input device 18 are connected to the PC 14. The monitor 16 and the input device 18 function as a user interface (UI). The input device 18 may employ various means such as a keyboard, a mouse, a touch panel, and a trackball, and may be an appropriate combination thereof. In this example, a combination of a touch panel, a keyboard, and a mouse is used as the input device 18. In addition, the form by which the monitor 16 and the input device 18 are comprised integrally like the structure which has arrange | positioned the touch panel on the screen of the monitor 16 is also possible. Further, it may be a monitor-integrated PC having a configuration in which a monitor is incorporated in the computer main body.

  The operator can input various information using the input device 18 while viewing the content displayed on the screen of the monitor 16, and can operate the printer 12. Further, it is possible to grasp (confirm) the state of the system through the monitor 16.

  The PC 14 represents an image input interface unit 22 (corresponding to an “image input unit”) for capturing the image data 20, and a database 24 (hereinafter referred to as an image data DB 24) as image data storage means for storing the captured image data. And). The image input interface unit 22 that functions as an input unit for the image data 20 may employ a wired or wireless communication interface unit, or a media interface unit that reads and writes an external storage medium (removable disk) such as a memory card. You may employ | adopt and these combinations may be sufficient.

  In FIG. 1, only one image data 20 is illustrated, but when a double-sided printed material is created by forming images on both the front and back surfaces of a sheet (not shown) as a printing medium, Image data to be printed on the front side and image data to be printed on the back side are input. When the front side of the sheet body is “first side” and the back side is “second side”, the image data on the front side corresponds to “first image data” and the image data on the back side is “second”. It corresponds to “image data”. The first image data and the second image data may be different image data, or may be the same (common) image data when the same image is printed on both sides. Moreover, since the front and back definitions of the sheet body are arbitrary, it is possible to associate the “first surface” with the back surface and the “second surface” with the front surface.

  Image data 20 input using printer management software (program) incorporated in the PC 14 is stored in the image data DB 24. In the printer management software, when the image data 20 is input, print condition settings for printing are performed, and the image data and print condition information are managed as a set as a print job.

  The PC 14 includes a printing condition instruction unit 26 that selects image data used for printing and sets various parameters, and a printing condition database 28 that stores printing condition information (hereinafter referred to as a printing condition DB 28). . In this specification, “DB” represents a database, and “LUT” represents a lookup table.

  The PC 14 stores a color conversion LUT-DB 30 that stores a LUT that describes signal conversion relationships used for color conversion, and a tone conversion LUT that stores a tone conversion LUT that describes signal conversion relationships for tone conversion. -DB32, unevenness correction LUT-DB34 storing unevenness correction LUT describing the signal conversion relationship for unevenness correction, halftone dot ratio table data (hereinafter referred to as "halftone table"), and tot. A halftone DB 36 (corresponding to a “halfton data storage unit”) that stores ink droplet amount data for each size is provided.

  The operator applies printing conditions (for example, paper type, size, number of sheets, color / monochrome, color correction parameter, density correction parameter) to the print image data registered in the image data DB 24 through the monitor 16 and the input device 18. Etc.) can be specified.

  The printing conditions include selection information for specifying tables and parameters to be referred to from the respective databases (32 to 36) of the gradation conversion LUT-DB32, the unevenness correction LUT-DB34, and the halftone DB36. For each image data to be printed, appropriate data or the like is selected from each database (32 to 36) according to the specified conditions such as the paper type and size, and the printing condition data including these information is the image data. Assigned.

  Furthermore, the PC 14 includes an image processing unit 40 for optimizing the ink amounts on both sides when performing duplex printing. The image processing unit 40 includes an image reduction processing unit 42, a color conversion unit 44, a color conversion LUT generation system 46, a gradation conversion unit 48, an ink amount calculation unit 50, and a double-side total ink amount analysis unit 52. The gradation conversion unit 48 includes a density conversion processing unit 48A and an unevenness correction processing unit 48B. Details of the image processing function in the PC 14 will be described later. Note that each part (elements 22 to 52) in the PC 14 shown in FIG. 1 is configured by hardware or software of the PC 14, or a combination thereof.

  The printer 12 includes an image process board 60 that performs signal processing for converting image data received from the image data DB 24 of the PC 14 into a marking signal, and a marking unit 68 that performs image formation according to the marking signal generated by the image process board 60. Is provided. The printer 12 of this example forms an image using four color inks of cyan (C), magenta (M), yellow (Y), and black (K). Further, the printer 12 includes a conveyance unit 69A that conveys a sheet body (not shown) as a print medium, and a paper discharge unit 69B that discharges printed matter after image formation.

  The image process board 60 includes a color conversion unit 62, a gradation conversion unit 64, and a halftone processing unit 66. The gradation conversion unit 64 includes a density conversion processing unit 64A and an unevenness correction processing unit 64B. The image process board 60 performs color conversion processing, gradation conversion processing (density conversion processing and unevenness correction processing), and halftone processing (also referred to as quantization processing) on input image data, and outputs a marking signal. Generate. The image data input to the image process board 60 is converted into a marking signal through processing by each processing unit (62, 64A, 64B, 66), and is recorded (image formation) on a sheet body (not shown) by the marking unit 68. The The printed matter after the image formation is stacked on the paper discharge unit 69B.

  The color conversion unit 62 performs processing for converting the signal value (device value) of the image data so that it is printed with the color defined in the image data, using the color conversion LUT specified by the printing condition instruction unit 26. . Here, a table describing the relationship of chromaticity values (color values defined in a device-independent color space, using CIE-L * a * b * values in this example) to CMYK values of image data ( Color conversion LUT that determines the conversion relationship of CMYK → CMYK so that the chromaticity values of the two tables of the table (printer profile) describing the relationship between the target profile), the device value (CMYK) of the printer 12 and the chromaticity value match. Is used. In this specification, coordinate values defined in the L * a * b * color space may be expressed as Lab values. The L * a * b * color space that is a device-independent color space corresponds to a “first color space”, and the CMYK color space that is a device-dependent color space corresponds to a “second color space”.

  Each table used in the color conversion unit 62 is stored in the color conversion LUT-DB 30, and an appropriate table is used according to printing conditions such as paper type (sheet body type), color reproduction condition, and total ink amount upper limit value. Selected and used.

  The density conversion processing unit 64A performs a process of determining density gradation characteristics such as what color density is drawn on the entire printing surface when an image is formed by the marking unit 68. The density conversion processing unit 64A converts the image data so that the color development characteristics defined by the printer 12 are obtained. For example, the density conversion processing unit 64A converts the input CMYK signal (pre-density conversion CMYK signal) into a density-converted CMYK signal in accordance with the tone conversion LUT specified by the printing condition instruction unit 26. Alternatively, the input CMYK signal (CMYK signal before density conversion) may be converted into a C signal after density conversion, an M signal after density conversion, a Y signal after density conversion, and a K signal after density conversion.

  For the signal conversion by the density conversion processing unit 64A, the conversion relationship is determined with reference to the gradation conversion LUT stored in the gradation conversion LUT-DB 32 in the PC. The gradation conversion LUT-DB 32 stores a plurality of LUTs optimized for each type of paper (sheet body) to be printed, and refers to an appropriate LUT according to the paper to be used. Such a gradation conversion LUT is prepared for each ink color. In the case of this example, a gradation conversion LUT is provided for each color of CMYK.

  When an instruction to execute printing of a print job is input through the input device 18 or based on a program, a gradation conversion LUT that matches the printing conditions associated with the image data to be printed is obtained from the gradation conversion LUT-DB 32. It is automatically selected and set in the density conversion processing unit 64A of the printer 12. Further, by inputting an instruction to select, change, or modify the LUT from the input device 18, it can be set to a desired LUT.

  The unevenness correction processing unit 64B has a density defined by the density conversion processing unit 64A when the ink is ejected by an input signal having a certain gradation value from each nozzle of the inkjet head constituting the marking unit 68. This is a processing unit that corrects the output density (ink discharge amount) of each nozzle so as to obtain a substantially uniform density on the entire upper surface. Ink jet heads vary in ejection characteristics from nozzle to nozzle, and the amount of ejected droplets is not necessarily uniform. In order to correct the output density unevenness due to such a variation in ejection performance for each nozzle, the unevenness correction processing unit 64B performs signal conversion. That is, the unevenness correction processing unit 64B causes the ink discharge amounts of the plurality of ink discharge nozzles in the inkjet head constituting the marking unit 68 to be within a predetermined allowable range within the head and between the heads, and color unevenness occurs within the image plane. The image signal is converted so as to correct the discharge amount of each nozzle so as to disappear.

  For example, the unevenness correction processing unit 64B converts the input CMYK signal into a CMYK signal after unevenness correction processing. Alternatively, the density-converted C signal, the density-converted M signal, the density-converted Y signal, and the density-converted K signal are classified according to color by the unevenness correction C signal, the unevenness correction M signal, and the unevenness correction process. After that, it is converted into Y signal and K signal after unevenness correction processing. In the conversion process by the unevenness correction processing unit 64B, the conversion relationship is determined by referring to the unevenness correction LUT stored in the unevenness correction LUT-DB 34 in the PC 14 in accordance with the designation from the printing condition instruction unit 26. The unevenness correction LUT-DB 34 stores a plurality of types of unevenness correction LUTs optimized for each type of paper (sheet body) to be printed, and refers to an appropriate LUT according to the paper to be used.

  The halftone processing unit 66 selects two or more binary or ink diameters (droplet sizes) for ejecting or not ejecting an image signal of multiple gradations (for example, 8-bit 256 gradations per color) for each pixel. If possible, it is converted into a multi-value signal indicating which droplet type is ejected. In general, a process (quantization process) for converting multi-tone image data having M values (M is an integer of 3 or more) into N value data (N is an integer of 2 or more and less than M) is performed. Various quantization methods such as a dither method, an error diffusion method, and a density pattern method can be applied to the halftone process.

  It is assumed that the marking unit 68 of this example can sort three types of droplet sizes, large droplets, medium droplets, and small droplets. In this case, the halftone processing unit 66 uses the multi-gradation data (for example, 256 gradations) after the unevenness correction processing to “discharge large droplet ink”, “discharge medium droplet ink”, and “small droplet ink”. It is converted into a four-value signal of “discharge” and “not discharge”. The signal conversion in the halftone processing unit 66 determines the conversion relationship with reference to a table (halftone table) stored in the halftone DB 36 in the PC 14.

  The halftone table is a table for determining two-dimensional dot drawing conditions for drawing dots of large, medium, and small sizes per unit area, and an N × N two-dimensional threshold matrix. And a threshold parameter that determines which of the large, medium, and small ink droplet amounts is used. The halftone DB 36 stores a plurality of types of halftone tables, and one of the tables is selected during printing.

  The multi-value signal (four-level marking signal in this example) generated by the halftone processing unit 66 is sent to the marking unit 68 and the ejection energy generating element (for example, piezoelectric element or heating element) of the corresponding nozzle. Used for drive control. That is, ink ejection control of each nozzle in the marking unit 68 is performed according to the four-value signal. Large dots are recorded on the sheet body by the large droplet ink, medium dots are recorded on the sheet body by the medium droplet ink, and small dots are recorded on the sheet body by the small droplet ink. In this way, multi-gradation is reproduced by area gradation based on the arrangement of ink dots formed on a sheet body as a printing medium.

  The marking unit 68 includes an ink jet head as a liquid discharge head. In this embodiment, it is assumed that four color inks of C, M, Y, and K are used, and a case where an ink jet head is provided for each color as means for ejecting each color ink will be described. However, the combination of the ink color and the number of colors is not limited to this embodiment.

  The printing system 10 of this example is a system that records an image by a single pass method. That is, an image having a predetermined recording resolution (for example, 1200 dpi) is formed in the image forming area of the sheet body by performing the operation of moving the recording medium relative to the ink jet head of each color only once (with one sub-scan). Can be recorded. A plurality of ink ejection nozzles are arranged on the ink ejection surface (nozzle surface) of each head over a length corresponding to the maximum width of the image forming area of the paper. A high recording resolution can be realized by a configuration in which a large number of nozzles are two-dimensionally arranged on the ink ejection surface.

  In the case of an inkjet head having a two-dimensional nozzle array, each nozzle in the two-dimensional nozzle array is orthogonal to the medium transport direction (corresponding to “sub-scanning direction” and “y direction”) (“main scanning direction”, “x The projection nozzle row that is projected (orthogonally projected) so as to line up along the direction) is a row of nozzles that are arranged at approximately equal intervals at a nozzle density that achieves recording resolution in the main scanning direction (medium width direction). It can be considered equivalent to a sequence. The “substantially equidistant” means that the droplet ejection points that can be recorded by the ink jet printing system are substantially equidistant. For example, the concept of “equally spaced” also includes cases where the intervals are slightly different in consideration of manufacturing errors and movement of droplets on the medium due to landing interference. Considering projection nozzle rows (also referred to as “substantial nozzle rows”), nozzle positions (nozzle numbers) can be associated with the order of projection nozzles arranged along the main scanning direction. In the following description, “nozzle position” refers to the position of the nozzle in this substantial nozzle row.

<Overview of printing operation>
When an image is printed by the printer 12, a print job for the target image is selected from the printer management software of the PC 14, and a print execution instruction is given. In response to the print execution instruction, the print condition instructing unit 26 transmits the parameter file corresponding to the print condition set in the print job to the color conversion unit 62 and the gradation conversion unit of the image process board 60 in the printer 12. 64, the image data of the target image is input to the image process board 60.

  The image process board 60 processes each block of the color conversion unit 62, the gradation conversion unit 64, and the halftone processing unit 66 on the input image data. The marking signal generated by the image process board 60 is sent to the marking unit 68, and the marking unit 68 is driven according to the marking signal to form an image on the paper.

  The printer 12 may be either a double-sided printing machine or a single-sided printing machine. For example, a front surface recording marking unit that records an image on the front surface of a sheet and a back surface recording marking unit that records an image on the back surface of the sheet are provided on both sides of the sheet simultaneously. Alternatively, it is possible to employ a double-sided printer that automatically and sequentially forms images on each side. Moreover, not only a double-sided printer but also a single-sided printer may be used to perform printing on each side to obtain a double-sided printed material. When a single-sided printer is used, a double-sided printed product can be obtained by returning the paper printed on one side to the paper feed unit and printing on the other side.

  Further, the present invention is not limited to a mode in which single-sided or double-sided image formation is completed by one image forming operation, and a mode in which single-sided or double-sided printing is overwritten may be used. The printer 12 only needs to be able to create a double-sided printed product that has been printed on both sides as a result, and various forms can be employed.

<Outline of image processing function in PC 14>
Next, an image processing function that realizes optimization of ink usage on both sides when creating a double-sided printed material will be described. The PC 14 is equipped with an image processing function that appropriately adjusts the total ink amount on both sides so as not to cause image defects due to stacking on the paper discharge side when a double-sided printed material is created. Before executing printing, the image processing unit 40 in the PC 14 calculates in advance the amount of ink used for printing the image data (ink usage) from the image data to be printed, and the paper is printed on the paper discharge side. The total ink amount on both sides is determined for each unit region (predetermined unit area) in a positional relationship where the front and back sides of the two sides are overlapped. In this example, the total ink amount on both sides is calculated in units of one pixel of the reduced image data generated by the image reduction processing unit 42. Then, by comparing the calculated total ink amount on both sides with the specified value indicating the upper limit of the allowable amount of the total ink amount on both sides, it is determined whether or not the specified value is exceeded. It is determined whether or not there is an area that exceeds the specified value. The specified value can be experimentally determined as a threshold value of the ink amount that is likely to cause blocking depending on the type of paper, the printing mode, and the like. The specified value is changed according to the paper type to be used.

  As a result of evaluating (predicting) the ink amount from the image data on both sides, if the total ink amount on both sides in a positional relationship where the front and back sides overlap each other exceeds the specified value, make sure that the total ink amount on both sides falls within the specified value, and The color conversion LUT as the color conversion condition is changed so as to save the output color. Specifically, the upper limit value of the total ink amount at the time of color conversion is changed to a new printer profile that reduces the ink amount, and the color conversion LUT is corrected.

  FIG. 2 is a flowchart showing the flow of processing when calculating the ink amount distribution from the image data. First, image data is input to the PC 14 (step S11). The input image data is registered in the image data DB 24. Thereafter, reduced image data is generated from the image data (step S12). Since the input image data registered in the image data DB 24 has a relatively large amount of data, if the input image data is directly processed in the ink amount evaluation calculation, the calculation load becomes excessive. Therefore, in the present embodiment, the image data is reduced to a data size that can be easily calculated from the viewpoint of efficient calculation. That is, a reduced image (sometimes referred to as “thumbnail”) having a predetermined resolution is generated from the input image data by the image reduction processing unit 42. The resolution of the reduced image is not particularly limited, but as an example, the resolution (several tens of dpi, for example, about 25 dpi) corresponding to a size of about 1 mm (millimeter) on one side of one pixel in the reduced image is provided. Converted to an image.

  Thereafter, color conversion processing is performed on the reduced image data by the color conversion unit 44 (step S13). The color conversion LUT applied to the color conversion unit 44 is set according to the LUT selection information described in the print condition information of the print job.

  The gradation conversion unit 48 performs image conversion processing on the reduced image data after color conversion (step S14). This image conversion processing includes density conversion and unevenness correction processing. The gradation conversion LUT applied to the density conversion processing unit 48A and the unevenness correction thumbnail LUT applied to the unevenness correction processing unit 48B are set according to the LUT selection information described in the print condition information of the print job.

  Ink amount distribution data is generated from the reduced image data obtained by the image conversion processing in step S14 with reference to the halftone dot ratio table and the appropriate ink amount data (step S15). For each of the first image data on the front surface and the second image data on the back surface, the first ink amount distribution data on the front surface and the second image data on the back surface are obtained by performing the processes of steps S11 to S15. Ink amount distribution data can be obtained. From the ink amount distribution data on both sides, the total amount of ink on both sides can be obtained by the positional relationship where the front surface and the back surface overlap.

<Detailed Configuration of Image Processing Unit 40 in PC 14>
Hereinafter, the configuration of the image processing unit 40 in the PC 14 will be described in detail.

<< Image reduction processing section >>
The image reduction processing unit 42 performs processing for reducing the size of the input image data. Here, the resolution per pixel of the reduced image data is defined inside the processing unit, and the reduction process is performed so as to obtain the resolution. There are several processing methods such as a thinning-out processing method, and various processing methods can be applied. However, it is preferable to consider the following as a more accurate method.

  (1) The range corresponding to the area per pixel of the reduced image is averaged on the input image data, and the data is assigned as one pixel of the reduced image.

  (2) As another method for obtaining accuracy, a pixel value in a range corresponding to the area per pixel of the reduced image is added to the input image data, and converted from the data addition value to a signal value of the reduced image. Assign to one pixel. In this case, a table that defines the correspondence for assigning the reduced image signal value j to the data addition value s is prepared in advance, and the data addition value s is converted into the reduced image signal value j according to this table. And assign it to the pixel. When such a method is employed, the information of the signal value of the input image data before the reduction process is saved on average, so that the ink amount can be calculated with high accuracy.

  (3) The reduced image data preferably uses a signal depth of 16 bits or more in order to maintain the necessary ink amount resolution when converted into ink amount distribution data.

  (4) When the input image data includes characters and images defined as components (image components) in the file, the image data is reduced for each image component, and the position coordinate information of the image components in the image data And set.

  As shown in FIG. 1, the image data 20 registered in the image data DB 24 as a printing target is first converted into reduced image data by the image reduction processing unit 42 in order to calculate the distribution of ink usage. . There are no particular limitations on conditions such as the format, the number of pixels, and the resolution of the image data (input original image data) registered in the image data DB 24.

  For example, the input original image data can be page description language data having a document image size “B2” (JIS standard paper size: 728 × 515 mm). Further, the input image data may be, for example, 8-bit (24-bit color) image data for each color of RGB, or 8-bit data for each color that is color-converted into ink colors (for example, 4 colors of CMYK). In order to adjust the format of the image registered in the image data DB 24, preprocessing such as pixel number conversion processing and color coordinate conversion processing may be performed in the PC. In this case, the PC 14 includes a pixel number conversion processing unit, a color coordinate conversion processing unit, and the like.

  FIG. 3 is an explanatory diagram showing an example of image reduction processing. The left side of FIG. 3 shows the original input image data before the image reduction process, and the right side of FIG. 3 shows the reduced image data after the image reduction process. In FIG. 3, for the convenience of illustration, the number of pixels is reduced. In the input image data shown on the left side of FIG. 3, one cell (reference numeral 71) of a grid indicated by a dotted line represents one pixel of the input image data. Further, in the reduced image data shown on the right side of FIG. 3, one cell (reference numeral 72) of the lattice indicated by the dotted line represents one pixel of the reduced image data.

  In FIG. 3, a certain pixel area in the input image data (an example of a range of 4 × 4 = 16 pixels surrounded by a bold line 73) is one pixel of the reduced image data (a range surrounded by a thick line 74 in FIG. 3). ). One pixel of the reduced image data shown in FIG. 3 corresponds to a square region (amm × amm rectangular range) in which one side is a millimeter (mm) on the printing paper (where a is an arbitrary positive number). The signal value of the input image data is averaged with respect to the pixel area of the original input image data belonging to the range of the one pixel, and the average value is converted into the value of one pixel (pixel value) of the reduced image. ). That is, the average value of 16 pixels surrounded by the bold line 73 in FIG. 3 is assigned as the signal value of 1 pixel surrounded by the bold line 74 in the reduced image data. A similar averaging process is performed on the entire input image data, and reduced image data is generated. In this way, since an average value in a certain range in the original input image enters one pixel of the reduced image, the ink amount information is saved. Therefore, a highly accurate calculation result can be obtained in the ink amount evaluation calculation. In FIG. 3, for the sake of illustration, the reduction ratio is illustrated as 1/16. However, the actual reduction ratio is even smaller, and for example, the data amount is greatly reduced from about 1200 dpi to 25 dpi.

  Further, as another method for improving the accuracy, a pixel value in a range corresponding to the area per pixel of the reduced image is added to the input image data, and 1 through a table that converts the data addition value into a signal value of the reduced image. A method of assigning to pixels is also desirable.

  As another method, there is a method in which a representative value is determined from a signal value in a predetermined pixel area of the original input image data, and this representative value is applied to the signal value of one pixel of the reduced image data. In determining the representative value, a median (median) or mode value can be used in addition to the average value. In addition, an appropriate representative value may be determined from the histogram, a representative value may be determined from a range excluding the maximum value and the minimum value, or the average of the upper few% of the signal value distribution. You may combine suitably the device on statistical calculation, such as making a value into a representative value.

  The depth (number of gradations) of the input image data signal before the reduction process is, for example, 8 bits (256 gradations) for each color. The image reduction processing unit 42 performs a process of reducing the number of pixels of the image data, and converts the signal depth of each pixel to 16 bits. Thus, the reduced image data generated by the image reduction processing unit 42 is sent to the color conversion unit 44.

<< Color conversion part >>
FIG. 4 is a principal block diagram relating to color conversion processing in the PC 14. The color conversion unit 44 performs color matching processing and signal processing for setting the total amount of CMYK ink to an upper limit value or less for the reduced image data 80 generated by the image reduction processing unit 42. Here, the “upper limit value of the total amount of ink” is the upper limit value of the total sum of CMYK ink usage per unit area on one side (total amount of ink). For example, an upper limit value of the total amount of CMYK ink is set for each of the front surface and the back surface in units of one pixel of the reduced image data 80 according to the paper type and print mode. When the upper surface total ink amount upper limit value is T ₁ and the rear surface ink total amount upper limit value is T ₂ , T ₁ and T ₂ may be the same value or different values. Appropriate upper limit values (T ₁ , T ₂ ) are set in consideration of the paper type, use of the printed matter, printing cost, and the like. Incidentally, when the specified value that indicates the upper limit of two-sided total amount of ink used in the double-sided total ink amount analyzing unit 52 and _{T 3, T 3} is _{T 1} and smaller than the sum of _{T 2 (T 3 <T 1} + T ₂ ).

  In the color conversion process in the color conversion unit 44, the color conversion LUT to be used is set from the color conversion LUT-DB 30 according to the printing conditions. The color conversion LUT applied to the color conversion unit 44 is generated by combining two profiles of a target profile and a printer profile under the control of the printing condition instruction unit 26. In the target profile of this example, the print color target value is described by at least the relationship of the Lab space Lab value to the CMYK value of the CMYK color space (CMYK → Lab relationship). In the printer profile of this example, the printer color is described as a relationship of CMYK values to Lab values in Lab space (Lab → CMYK relationship).

  As shown in FIG. 4, the color conversion LUT generation system 46 includes a printer profile generation unit 82 that generates a printer profile and a color conversion LUT generation unit 84. When there is an instruction to set / change the total ink amount, the printer profile generation unit 82 recreates the printer profile according to the specified upper limit value of the total ink amount. In this re-creation of the printer profile, the relationship of the CMYK value to the Lab value changes. When the ink amount is reduced, the CMY signal is reduced, and a K value is obtained so that Lab is stored under that condition. Even if the amount of ink is reduced by this process, the color of the printed matter can be preserved.

  The color conversion LUT generation unit 84 combines the two profiles of the target profile and the printer profile to generate a color conversion LUT.

  In the color conversion process in the color conversion unit 44, it is possible to specify which color conversion LUT is used for each image component in the image file to be printed. For this reason, the color conversion LUT can be changed only for image parts whose ink amount is desired to be reduced. The reduced image data 86 subjected to color conversion by the color conversion unit 44 is sent to the gradation conversion unit 48 (see FIG. 1).

<< Tone conversion part >>
As shown in FIG. 1, the gradation conversion unit 48 includes a first half density conversion processing unit 48A and a second half unevenness correction processing unit 48B. The density conversion processing unit 48A in the first half performs processing for converting signal values using the same LUT (gradation conversion LUT) on the entire surface of the image data. The density conversion processing here includes a method using a one-dimensional (1D) -LUT that determines a conversion relationship of each CMYK signal and a method using a multi-dimensional LUT that determines a conversion relationship corresponding to a combination of CMYK signals. The method may be adopted.

  The latter half unevenness correction processing unit 48B selects from the unevenness correction thumbnail LUT an LUT corresponding to the x coordinate of the reduced image data (the paper width direction orthogonal to the paper transport direction is the x-axis direction). Signal processing is performed using the LUT related to the selection.

  The unevenness correction thumbnail LUT is an LUT obtained by editing the LUT corresponding to the width in the x direction per pixel of the reduced image into one LUT from the unevenness correction LUT described in units of pixels corresponding to the recording resolution of the printer 12. .

  As one method for realizing generation of the unevenness correction thumbnail LUT, an LUT corresponding to one pixel of the reduced image can be created by averaging the LUT corresponding to the width per pixel of the reduced image from the unevenness correction LUT. This method is an example. As another method, for example, the LUT having the largest value in the range of the unevenness correction LUT corresponding to the width per pixel of the reduced image is changed to the LUT corresponding to one pixel of the reduced image. You may employ | adopt methods, such as. The method of creating the unevenness correction thumbnail LUT varies depending on the LUT information desired to be used by the double-side total ink amount analysis unit 52 in the subsequent stage.

  The unevenness correction thumbnail LUT executes unevenness correction adjustment processing on the print, generates the unevenness correction thumbnail LUT immediately after the unevenness correction LUT is generated, and sets data in an area that can be processed by the gradation conversion unit 48. To do.

  FIG. 5 is a conceptual diagram showing an example of image conversion processing in the gradation conversion unit 48. The reduced image data for each color of CMYK is subjected to gradation conversion using the gradation conversion LUT for each color, and then subjected to unevenness correction processing using the uneven correction thumbnail LUT for each color. FIG. 5 illustrates a one-dimensional LUT for each color as the gradation conversion LUT.

  Each color unevenness correction thumbnail LUT includes a plurality of tables in the nozzle row direction. The nozzle row direction here is a direction in which a plurality of nozzles of the ink jet head are substantially aligned so as to achieve a predetermined recording resolution. As shown in FIG. 6, coordinate axes (x axis, y axis) are introduced in the horizontal direction (x direction) and the vertical direction (y direction) of the reduced image data, and the position of each pixel on the xy plane is (x, y). ), For example, it is assumed that the nozzles of the inkjet head are arranged along the x direction. In this case, there is a plurality of tables in which one LUT is associated with each pixel corresponding to each pixel position in the x direction of the reduced image data.

  That is, the unevenness correction thumbnail LUT is applied as a function of the pixel position (x coordinate) of the reduced image data, and the same set of LUTs is applied in units of the nozzle row direction (here, the x direction is illustrated). If the x coordinates of the pixels of the reduced image data are the same, the same LUT is applied to pixels having different y coordinates. FIG. 6 illustrates that the same unevenness correction thumbnail LUT is applied to a pixel row having the same x coordinate as the pixels surrounded by a thick line (pixels arranged in the y direction). In this way, the conversion process using the gradation conversion LUT and the unevenness correction thumbnail LUT is performed, and reduced image data after conversion is obtained (see FIG. 5). The reduced image data converted by the gradation conversion unit 48 is sent to the ink amount calculation unit 50 (see FIG. 1).

<< Ink amount calculation unit >>
The ink amount calculation unit 50 uses the halftone dot ratio table (halftone table) and the ink droplet amount data to generate ink amount distribution data indicating the distribution of the ink usage amount of the reduced image data. As one specific method of processing in the ink amount calculation unit 50, a ratio for each ink dot size when halftone processing is performed is obtained from the signal value of the reduced image data with reference to the halftone table, and the ratio is obtained as the ratio. After accumulating the ink droplet amount, the ink droplet amount of each dot size is added to determine the ink amount corresponding to each color. Further, the ink amount of each color is added to obtain the ink amount per pixel of the reduced image data. Coordinates representing the respective pixel positions are assigned to the ink amount data for each pixel of the reduced image data to form “ink amount distribution data” representing the ink amount distribution.

  That is, in calculating the ink amount, the reduced image data is not actually subjected to halftone processing, but the ratio data for each ink dot size at the time of gradation reproduction by the printer 12 is associated with the signal value of the reduced image data. A halftone dot ratio table (halftone data) is prepared (see FIG. 7), and the ratio of each ink dot size within a predetermined area is grasped from this halftone dot ratio table.

  FIG. 7 shows an example of the halftone dot ratio table. There can be various halftone dot ratio tables depending on the type of halftone (quantization) processing. One or more tables are prepared according to the type of halftone processing used in the printer 12, and an appropriate table is set according to the printing conditions. By using the halftone dot ratio table, an average recording ratio for each dot size per unit area is specified for a signal value j having reduced image data.

  The ink dot size ratio is multiplied by the ink droplet amount per dot of each dot size to obtain CMYK signal-by-signal ink amount distribution data. Further, the ink amount data of each color is added for each pixel to obtain the ink amount per pixel of the reduced image. Coordinates are assigned to the ink amount data to form ink amount distribution data.

  FIG. 8 schematically shows a procedure for creating ink amount distribution data for each signal from the reduced image data for each color of CMYK and adding them to create ink amount distribution data. The ink amount distribution data generated by the ink amount calculation unit 50 preferably uses a signal depth of 16 bits or more in order to maintain the ink amount resolution necessary for the double-side total ink amount analysis unit 52 at the subsequent stage.

  Front surface ink amount distribution data (corresponding to “first ink amount distribution data”) is generated from the reduced image data of the front surface. Back side ink amount distribution data (corresponding to “second ink amount distribution data”) is generated from the back side reduced image data. The first ink amount distribution data on the front surface and the second ink amount distribution data on the back surface generated by the ink amount calculation unit 50 are sent to the double-side total ink amount analysis unit 52 (see FIG. 1).

<< Double-sided total ink amount analysis part >>
Based on the first ink amount distribution data on the front surface and the second ink amount distribution data on the back surface, the double-sided total ink amount analysis unit 52 moves up and down each other when a plurality of double-sided printed products are stacked on the paper discharge side. For each unit area in the positional relationship where the front and back surfaces of the paper that will be in contact with each other overlap, calculate the total ink amount on both sides indicating the sum of the ink amounts on both the front and back surfaces .

  FIG. 9 is a schematic diagram showing the overlapping positional relationship between the front and back when the total ink amount on both sides is obtained from the first ink amount distribution data on the front surface and the second ink amount distribution data on the back surface. When a plurality of double-sided printed materials 90 are stacked on the paper discharge unit 69B of the printer 12 or a mounting table on which printed materials are placed after paper discharge, the printing surfaces come into contact with each other between the printed materials that are stacked one above the other. . As shown in FIG. 9, in a state where the double-sided printed products 90 are stacked, the front surface 91 </ b> A of the lower printed material 91 and the back surface 92 </ b> B of the upper printed material 92 overlapping this are in contact with each other. The image area 93A on the surface 91A and the image area 94B on the back surface 92B are in a positional relationship where they face each other and overlap each other.

  The positional relationship between the image areas 93A and 94B that face each other and come into contact with each other is considered to be a direct positional relationship when replaced with a single sheet. That is, when these two printed materials 91 and 92 are stacked at the same position in a plan view (without being shifted in the plane), or when the positional deviation between the sheets due to the stacking is within a practically negligible range. The image positions on the front and back that overlap each other are the same positions when viewed from one side of the same sheet (same sheet body). In the present embodiment, the total ink amount on both sides is calculated based on the positional relationship between the front and back surfaces that overlap in this way.

  The double-sided total ink amount analysis unit 52 calculates the sum of the ink amounts of the position coordinates that are in a positional relationship overlapping with each other in face-to-face contact from the first ink amount distribution data on the front surface and the second ink amount distribution data on the back surface. The calculation which calculates | requires per pixel of distribution data is performed.

  In the case of this example, the “total ink amount on both sides” is obtained by calculating the sum of the ink amounts on the front and back surfaces in pixel units of the ink amount distribution data. Since the double-sided total ink amount is obtained for each pixel position coordinate of the reduced image data, double-sided total ink amount distribution data indicating the distribution of the double-sided total ink amount is obtained.

  The double-sided total ink amount analysis unit 52 obtains the double-sided total ink amount for each pixel of the reduced image data, and then determines whether or not the double-sided total ink amount exceeds the specified value. Then, the double-sided total ink amount analysis unit 52 notifies the printing condition instruction unit 26 of information corresponding to the determination result. The specified value is determined according to the paper type, and can be changed to an appropriate specified value according to the paper type to be used.

  That is, if the total ink amount on both sides exceeds the specified value, the amount of ink over which pixel is obtained is determined, print condition change instruction information is created, the pixel position information and the ink over amount Is transferred to the printing condition instruction unit 26. In addition, when the ink amount distribution data is configured in units of image parts, an image part that exceeds the total ink amount on both sides is specified, and information for specifying the image part is added to the print condition change instruction information for printing. Transfer to the condition instruction unit 26.

  On the other hand, if the total ink amount on both sides does not exceed the specified value (if the total ink amount on both sides is within the specified value), make sure that the ink amount is appropriate (no change in the ink amount is necessary). The print condition instruction unit 26 is notified.

  That is, the double-sided total ink amount analysis unit 52 performs a function of calculating the double-sided total ink amount, a function of comparing the obtained double-sided total ink amount with a specified value, and if the comparison results in exceeding the specified value. A function for creating print condition change instruction information including over-quantity information, and a function for transferring the created print condition change instruction information to the print condition instruction unit.

  The printing condition instruction unit 26 receives the printing condition change instruction information from the double-side total ink amount analysis unit 52 and performs control to display information for prompting the change of the printing condition on the monitor 16.

  In addition, the printing condition instruction unit 26 receives information indicating that the ink usage is appropriate from the double-side total ink amount analysis unit 52 and displays information indicating that the ink usage has not been changed on the monitor 16. To control.

<< Print condition instruction section >>
The print condition instructing unit 26 shown in FIG. 1 selects image data to be used for printing, a color conversion LUT used by the color conversion units 44 and 62, a gradation conversion LUT used by the gradation conversion units 48 and 64, When a print job is selected for ink droplet amount data and halftone data used by the unevenness correction LUT and ink amount calculation unit 50, various LUTs and data designated by the print job are set in the corresponding processing unit. Do things.

  Various LUTs and data information set by the printing condition instructing unit 26 are stored in the printing condition DB 28.

  FIG. 10 is a conceptual diagram of a data structure stored in the printing condition DB 28. As illustrated, the print condition DB 28 includes, for each print job, an output image data name, various parameter information (target profile name, printer profile name, ink setting amount condition) necessary for selecting a color conversion LUT, and an unevenness correction LUT name. Ink droplet amount data name, halftone data name, etc. are stored in association with each other.

  When the printing condition instruction unit 26 receives the printing condition change instruction information from the double-sided total ink amount analysis unit 52, the printing condition instruction unit 26 updates (changes) the ink setting amount condition among various parameter information necessary for the color conversion LUT selection. In addition, when the ink amount distribution data is image data configured in units of image parts, if the “printing condition change instruction information” includes image part information that exceeds the ink amount, the image parts Only for the printer profile information is changed.

  When the user selects a print job and gives an instruction to execute printing, the print condition instructing unit 26 selects various parameters (target profile name, target profile name, and the like necessary for color conversion LUT selection associated with the print job registered in the print condition DB 28. Printer profile name, ink setting amount condition), unevenness correction LUT, and halftone data are set in the corresponding processing unit (see FIG. 3).

  When the user inputs an instruction for confirming the ink amount of the print image through the user interface, various parameters (target profile name, printer profile name, ink setting amount condition) necessary for the above color conversion LUT selection, unevenness correction LUT In addition to the halftone data, appropriate ink amount data and ink amount information are set in the corresponding processing unit (see FIG. 3).

<< Color conversion LUT generation system >>
As shown in FIG. 3, the color conversion LUT generation system 46 includes a printer profile generation unit 82 and a color conversion LUT generation unit 84. The printer profile generation unit 82 includes a printer profile designated by the printing condition instruction unit 26, and ink amount information (ink amount corresponding to the C signal, ink amount corresponding to the M signal, ink amount corresponding to the Y signal, The ink amount corresponding to the K signal and the ink total amount upper limit value) are input. In the printer profile, Lab value information corresponding to CMYK signal values (hereinafter referred to as “CMYK → Lab information”), CMYK information corresponding to Lab values (hereinafter referred to as “Lab → CMYK information”), and ink The total amount upper limit value is described.

  When the total ink amount upper limit value described in the printer profile matches the total ink amount upper limit value input to the printer profile generation unit 82, the printer profile is passed to the color conversion LUT generation unit 84.

  On the other hand, when the total ink amount upper limit value described in the printer profile does not match the total ink amount upper limit value input to the printer profile generation unit 82, the printer profile generation unit 82 determines the total ink amount based on the CMYK → Lab information. Lab → CMYK information is generated from the inverse operation so as to be within the upper limit, and a new printer profile is generated. The newly generated printer profile is registered in the color conversion LUT-DB 30 and transferred to the color conversion LUT generation unit 84.

  The color conversion LUT generation unit 84 receives the target profile specified by the printing condition instruction unit 26 and the printer profile passed from the printer profile generation unit 82, and receives CMYK → Lab information of the target profile and Lab → CMYK of the printer profile. From the information, CMYK → CMYK information is generated and used as a color conversion LUT. This color conversion LUT is passed to the color conversion unit 44. A combination of the printing condition instruction unit 26 and the color conversion LUT generation system 46 corresponds to a “color conversion condition changing unit”.

<Procedure for optimizing the total ink amount on both sides>
FIG. 11 is a flowchart showing the flow of the optimization process for the total ink amount on both sides according to this embodiment. 12 to 14 are diagrams showing examples of user interface (UI) operation screens displayed on the monitor 16.

  The function of optimizing the ink amount on both sides according to this embodiment is processed in the following flow.

  [Procedure 1] First, the user selects a print job and designates a paper type to be printed, a total ink amount setting value, and an ink amount changing condition (step S112 in FIG. 11).

  FIG. 12 shows an example of a UI operation screen for selecting a print job. The selection screen illustrated in FIG. 12 includes a selection candidate display field 102 that displays a list of selectable print job names, an ink amount confirmation button 104, a print button 106, and a return button 108. The name of the print job selected in the selection candidate display field 102 is highlighted (for example, highlighted).

  The ink amount confirmation button 104 is a graphical user interface (GUI) button that gives a command for executing a process of confirming the ink amount at the time of printing. The print button 106 is a GUI button for instructing execution of printing of the selected print job. The return button 108 is a GUI button for instructing to return to the operation screen before entering the selection screen of FIG.

  When a print job is selected from the selection candidate display field 102 and the ink amount confirmation button 104 is pressed, a transition is made to the condition setting screen (FIG. 13). The expression “pressing” the GUI button includes an operation of inputting a command corresponding to the button, such as clicking or touching.

  FIG. 13 shows an example of a condition setting screen. The condition setting screen includes a paper type setting field 112 for specifying the paper type, an ink total setting value field 114 for specifying the total ink amount setting value, and an ink amount changing condition field 116 for specifying the ink amount changing condition. , A confirmation start button 118 and a return button 108 are included.

  In the paper type setting column 112, a paper type (sheet body type) to be used such as coated paper or uncoated paper is selected. When the paper type is specified in the print condition of the print job, information on the paper type specified in the print job is automatically input as an initial candidate in the paper type setting field 112.

  The “total ink amount setting value” includes a plurality of options, and the setting condition is switched depending on the total amount of ink that can be used for printing paper types. This total ink amount setting value is, for example, printing image data in which the total amount of ink on the front and back is printed, checking the allowable total ink amount from the blocking state for each total ink amount of the print, and setting the setting conditions in several steps in advance. Decide it. Since the allowable amount of ink varies depending on the paper type, for example, the total ink amount is set in five stages. A configuration in which such five-step ink amount setting conditions are prepared experimentally in advance and can be selected by the user is preferable.

  The “ink amount changing condition” is used to specify under what conditions the total ink amount is to be reduced when the total ink amount on both sides of the front and back surfaces exceeds the specified value. Options for changing the amount of ink include, for example, “reduce the amount of ink used on the back side image (reduce the amount of ink on the back side only)”, “reduce the amount of ink used on the front side image (change the amount of ink on the front side only) Reduction) "," reduce ink usage on both sides "and so on.

  When reducing the amount of ink used on both sides, the ratio of the amount of ink reduction on the front and back sides can be set as appropriate. Alternatively, it is possible to reduce the amount of ink on both sides at a predetermined constant ratio. The ink amount may be reduced at the same ratio on both the front and back sides, or the ink amount may be reduced at a different ratio between the front and back sides.

  When conditions in the respective fields of the paper type setting column 112, the total ink amount setting value column 114, and the ink amount changing condition column 116 are selected and the confirmation start button 118 is pressed, the process proceeds to the double-side total ink amount confirmation and optimization processing.

  [Procedure 2] When the confirmation start button 118 is pressed, the image data of the front surface and the back surface relating to the print job is extracted from the image data DB 24, and reduced image data is created by the image reduction processing unit 42 (FIG. 11). Step S114). In this processing, when the image data is composed of image parts, the image data is reduced for each image part and the position information of the image parts is also saved.

  [Procedure 3] The reduced image data on the front and back sides obtained in the procedure 2 are input to the color conversion unit 44 to obtain reduced image data having signal values in which color matching and the total ink use amount are suppressed to a certain level or less (FIG. 11). Step S116). When the image data is composed of image parts, color conversion processing is performed for each image part (object). In the example of FIG. 11, it is assumed that the image data is composed of image parts, and a step of performing color conversion for each object is described.

  [Procedure 4] Each of the reduced image data after the front and back color conversion obtained in the procedure 3 is input to the gradation converting unit 48 to obtain reduced image data subjected to gradation conversion (density conversion and unevenness correction) processing. When the image data is composed of image parts, gradation conversion (density conversion and unevenness correction) is performed for each image part.

  [Procedure 5] The reduced image data on the front and back obtained in the procedure 4 is input to the ink amount calculation unit 50, and ink amount distribution data indicating the distribution of the ink amounts on the front and back sides is generated (step S118 in FIG. Corresponding to “step for obtaining first ink amount distribution” and “step for obtaining second ink amount distribution”).

  [Procedure 6] The front and back ink amount distribution data obtained in step 5 are input to the double-sided total ink amount analyzing unit 52, and the inks at the respective positions used in the front and back images at the overlapping positions when the printed materials are stacked. The sum of the amounts is obtained in units of pixels, and it is confirmed whether or not the total ink amount (double-side total ink amount) exceeds the specified value (corresponding to step S120 in FIG. 11, “determination step”). By comparing the total ink amount on both sides with the specified value for all pixel positions, the pixel position where the ink amount exceeds the specified value can be specified, and how much the ink amount is over. I can grasp it. When the image data is composed of image parts, an object in a region where the ink amount is over is specified.

  [Procedure 7] Based on the processing in Procedure 6, it is determined whether there is an area where the total ink amount on both sides exceeds the specified value (step S122 in FIG. 11), and the total ink amount on both sides exceeds the specified value. If so (when Yes is determined in step S122), the over amount (referred to as "over ink amount") is transferred to the print condition instruction unit 26 as "print condition change instruction information" (step S124). When the image data is composed of image parts, information on which image parts (objects) are over is also transferred.

  [Procedure 8] Upon receiving the “print condition change instruction information”, the print condition instruction unit 26 updates (corrects) the “ink setting amount condition” in various parameter information necessary for selecting the color conversion LUT in the print condition DB 28. . Based on the over ink amount information included in the print condition change instruction information, the amount of ink used for each of the front surface and the back surface is determined, and the setting condition of the color conversion LUT, that is, the ink is determined. The ink set amount condition including the total amount upper limit value is changed (step S126 in FIG. 11). If the image data is composed of image parts, the setting condition of the color conversion LUT is changed for only the image part (object) of the target image. The printer profile is changed according to the changed ink setting amount condition (see FIG. 3).

  [Procedure 9] After the ink setting amount condition which is the setting condition of the color conversion LUT is corrected in the procedure 8, the new color conversion LUT is applied and the process returns to the process of the procedure 3 (step S116 in FIG. 11). That is, the function for optimizing the ink amount on both sides is a setting change based on “printing condition change instruction information” in step 8 ((step S126 in FIG. 11), and the total ink amount on both sides after the change is within a specified value. In order to confirm whether or not it is within the range, the processing after the above-described procedure 3 (step S116) is performed again.

  When this process is performed, the following processes (a) and (b) are performed in order to update the color conversion LUT set in the color conversion unit 44.

  (A) A printer profile is re-created based on the updated ink setting amount condition.

  (B) A color conversion LUT is generated from the recreated printer profile and target profile.

  Thereafter, the reduced image data generated in the above procedure 2 (step S114) is input to the color conversion unit 44, and the processing from procedure 3 (step S116) to procedure 6 (step S120) is performed thereafter.

  Then, again, similarly to the procedure 6, it is verified whether or not the total ink amount on both sides of each pixel exceeds the specified value, and the process proceeds to step S124 or step S128 depending on the result of the verification.

  [Procedure 10] Based on the processing in Procedure 6 (Step S120), it is determined whether there is an area where the total ink amount on both sides exceeds the specified value (Step S122 in FIG. 11), and the total ink amount on both sides is specified. If there is no region that exceeds the value (when No is determined in step S122), the result is displayed on the UI operation screen (corresponding to step S128 in FIG. 11, “notifying step”).

  The result displayed on the UI operation screen in step S128 is displayed under the following conditions.

  (1) If there is no need to change the total amount of ink on both sides (if there is no area where the total amount of ink on both sides exceeds the specified value with the initial color conversion LUT setting), the amount of ink is changed It is displayed that it did not.

  (2) When a change is made to reduce the total ink amount, the changed result is displayed. The information displayed at this time includes (a) display of the position of the image where the ink amount (color conversion condition) is changed (for example, the image is displayed, and the color is applied to the changed image area such as the whole or a specific image component). And (b) information on the change amount of the total ink amount.

  FIG. 14 is a diagram showing a screen example of the result display in step S128 of FIG. The result display screen illustrated in FIG. 14 shows an example in which the ink amount is reduced at a certain ratio for both the front and back images. On the result display screen, a first image display area 122 for displaying the image content of the front surface and a second image display area 124 for displaying the image content of the back surface are arranged side by side. Different images are displayed so that specific image regions (changed image regions) 126 and 128 where the ink amount is reduced are grasped for each of the image and the back image.

  Also, ink change amount information 132 indicating the ink change amount of the image area 126 is displayed near the first image display area 122, and the ink change amount of the image area 128 is displayed near the second image display area 124. Ink change amount information 134 is displayed. There may be a plurality of image areas in which the ink amount is changed in one image.

  In addition, on this result display screen, a selection field 136 in which the ink amount setting can be changed, a setting button 142, and a return button 144 are displayed.

  The user looks at the result display screen and outputs the printed matter with the changed result, or cancels the change and outputs the original condition, or further changes (specifies) the ink amount correction amount and outputs it. Can be handled.

  When printing with the content of the ink change amount setting displayed on the result display screen, the item “according to setting” is selected in the selection field 136 and the setting button 142 is pressed. When the setting button 142 is pressed in FIG. 14, the setting contents are determined, and the screen shifts to the print job selection screen shown in FIG. In the result display screen of FIG. 14, when canceling the setting for changing the total ink amount on both sides, the return button 144 in FIG. 14 is pressed to cancel the setting change process. The UI operation screen in FIG. 14 corresponds to a screen display that asks the user whether the setting can be changed.

  Further, in the case where the correction amount of the ink amount is changed to another value from the ink change amount presented on the result display screen of FIG. 14, the selection column 136 is selected to switch the total ink amount setting value. And press the setting button 142. Then, the printer profile is re-corrected according to the designated total ink amount setting value, and is changed to a color conversion LUT that satisfies the designated total ink amount setting value.

  The color conversion conditions including the total ink amount setting value set in this way are stored in association with the print job and stored in the print condition DB 28. Therefore, the next time the same print job is output, it can be output as it is using past condition information without performing the ink amount optimization processing on both sides.

<Description of Printing Method According to this Embodiment>
FIG. 15 is a flowchart showing an overall processing flow when a double-sided printed material is created by the printing system 10 of the present embodiment.

  As shown in FIG. 15, first, the first image data on the front surface and the second image data on the back surface are input to the PC 14 (step S210), and these image data are registered in the image data DB 24 (step S212). ). At that time, print condition setting information is input to generate print job information associated with the image data to be printed, and the print job is registered in the print condition DB 28 (step S214).

  Next, it is determined whether or not to check the ink amount on both sides and adjust the optimization for the print job (step S216). As described with reference to FIG. 12, the target print job is selected from the print job list display, the ink amount confirmation button 104 is pressed, and the necessary settings are made on the setting operation screen of FIG. When the start button 118 is pressed, a Yes determination is made in step S216 in FIG. 15, and the process proceeds to “both-side total ink amount optimization processing” in step S218.

  On the other hand, if the confirmation start button is not pressed and the determination in step S216 is No, the process proceeds to step S300 to determine whether or not execution of printing has been commanded.

  If the print button 106 described with reference to FIG. 12 is not pressed, No is determined in step S300 in FIG. 15, and the process returns to step S216 to wait for an instruction input from the user. When the print button 106 described with reference to FIG. 12 is pressed, a Yes determination is made in step S300 in FIG. 15, and the process proceeds to “print processing” in step S302.

<< Total ink optimization on both sides >>
16 and 17 are flowcharts showing the contents of the double-sided total ink amount optimization processing (step S218 in FIG. 15).

  As shown in FIG. 16, when the double-sided total ink amount optimization process is started, first, the image data of the front surface and the back surface are read from the image data DB 24 (step S222).

  Then, reduced image data is generated for each of the first image data and the second image data (steps S224 and S244). Each reduced image data is subjected to color conversion processing (steps S226 and S246) and gradation conversion processing (steps 228 and S248), and the first ink amount distribution data on the front surface and the second data on the back surface. Ink amount distribution data is created (steps S230 and S250).

  Step S230 corresponds to the “step for obtaining the first ink amount distribution”, and step S250 corresponds to the “step for obtaining the second ink amount distribution”.

  Based on the first ink amount distribution data and the second ink amount distribution data obtained in this way, the total ink amount on both sides is obtained in the pixel unit (area unit for one pixel of the reduced image data) where the front and back overlap. Then, distribution data of the total ink amount on both sides is created (step S270).

  Next, the process proceeds to step S272 in FIG. 17, and the value of the double-sided total ink amount and the specified value are compared for each pixel of the double-sided total ink amount distribution data (step S272), and the double-sided total ink amount exceeds the specified value. It is determined whether or not a specific image area exists (step S274). Steps S272 and S274 correspond to a “determination step”.

  If there is an area where the total ink amount on both sides exceeds the specified value (Yes in step S274), print condition change instruction information is created (step S276). The print condition change instruction information includes position information of an area exceeding the specified value (ink amount over area) and ink over amount information. Next, in accordance with the print condition change instruction information, the color conversion condition (color conversion LUT) is changed so that the total ink amount on both sides of the ink amount over area falls within the specified value and the color is preserved. (Steps S278 to S280, corresponding to “step of setting color conversion conditions”).

  In other words, a new ink setting amount condition (upper limit value of the total ink amount) that keeps the ink amount within the specified value is determined from the over ink amount information, and the total ink amount does not exceed the upper limit value based on the ink setting amount condition In step S278, a printer profile for color conversion is recreated. Then, a new color conversion LUT is generated from the re-created printer profile and target profile (step S280).

  If there is an area where the total amount of ink on both sides exceeds the specified value at any part of the image, an image malfunction may occur in that specific area. If only a region exceeding the specified value is found, it is preferable to reduce the ink amount (change the color conversion condition).

  As modes for reducing the total ink amount on both sides exceeding the specified value, the color conversion condition is changed so as to reduce the ink amount only on the front surface, and the color conversion condition so that the ink amount is reduced only on the back surface. Any mode of changing the color conversion condition so as to reduce the ink amount on both the front surface and the back surface is also possible.

  The color conversion condition can be changed for a pixel region in which the total amount of ink on both sides exceeds a specified value. In addition, the color conversion condition can be changed in units of image parts including a pixel area in which the total ink amount on both sides exceeds a specified value. Regarding the designation of the image plane for reducing the ink amount and the designation of the range of the image area for changing the color conversion condition, a configuration that can be appropriately selected by the user or a configuration that is automatically selected by a program may be adopted. For example, when the reduction ratio of the ink amount on the front surface and the back surface is determined in advance and the condition “reduction of ink amount on both surfaces” is selected, according to the predetermined ratio, The ink reduction amount on the front surface and the ink reduction amount on the back surface are determined, and the upper ink total amount upper limit value and the back surface ink total upper limit value are determined.

  In step S280, after a new color conversion LUT is generated, this new color conversion LUT is applied to perform the processing of steps S226 and / or S246 in FIG. When the mode of reducing only the ink amount on the front surface is selected, a new color conversion LUT is used for the process of step S226, and the processes of steps S226 to S230 are performed. When the mode of reducing only the ink amount on the back surface is selected, a new color conversion LUT is used for the processing in step S246, and the processing in steps S246 to S250 is performed. When the mode for reducing the ink amount on both sides is selected, the corresponding new color conversion LUT is used for each processing in steps S226 and S246, and the processing in steps S226 to S230 and step S246 are performed. -The process of step S250 is performed.

  In this way, the color conversion condition is corrected, and distribution data of the total ink amount on both sides is recreated in step S270.

  If it is determined in step S274 that there is no specific area where the total ink amount on both sides exceeds the specified value (No in step S274), the result is displayed on the screen of the monitor 16 (step S282). Next, it is determined whether or not to change the ink amount setting (step S284). As described with reference to FIG. 14, when the user presses the setting button 142 and gives an instruction to change the ink amount setting, a Yes determination is made in step S284 in FIG. Are updated (corresponding to “step S286,“ step of setting color conversion conditions ”). After step S286, the process returns to the main flow of FIG. 15 (step S216).

  On the other hand, when the user gives an instruction to reject the setting change in step S284 in FIG. 17, the print condition of the print job is not corrected, and the process returns to the main flow in FIG. 15 (step S216).

  FIG. 18 is a flowchart showing the flow of the printing process (step S302 in FIG. 15). As described with reference to FIG. 12, when the print button 106 is pressed, the printing process of FIG. 18 starts. When the printing process is started, various parameters of the printing conditions associated with the print job are set on the printer 12 side (step S310). That is, necessary parameters are set in the color conversion unit 62, gradation conversion unit 64 (density conversion processing unit 64A, unevenness correction processing unit 64B), and halftone processing unit 66 of the image process board 60 of the printer 12, respectively.

  Further, the image data to be printed is transferred from the image data DB 24 to the printer 12 (step S312). Note that the order of the processes in step S310 and step S312 can be switched, and parallel processing may be performed.

  Next, color conversion processing (step S314) is performed on the transferred image data. When the process of optimizing the total ink amount on both sides described with reference to FIGS. 16 and 17 is performed and the color conversion condition (color conversion LUT) is corrected according to the process, the corrected color conversion LUT is converted into a color. Therefore, the total amount of ink on both sides is converted into an image signal stored within a specified value.

  After the color conversion process (step S314), a gradation conversion process (step S316) and a halftone process (step S318) are performed, and a marking signal is generated (step S320). Image formation by the marking unit 68 is performed in accordance with the marking signal thus generated (step S322, corresponding to “image forming process”).

  For each of the front surface and the back surface, the processes in steps S310 to S322 are performed, and a double-sided printed material having images formed on both sides is obtained.

  The printed matter after the image formation is sent to the paper discharge unit 69B and stacked on the paper discharge unit 69B (step S324). It is determined whether or not the number of printed materials designated by the print job has been created (step S326). If the designated number of prints has not been completed, the process returns to step S322 to continue the image forming process. When printing of the designated number of pages is completed, the printing process is terminated.

  According to the present embodiment, it is possible to obtain a printed material having a desired color specified by a print job, and it is possible to avoid the occurrence of image defects due to stacking of printed materials such as blocking phenomenon.

<Description of Generation Method of Unevenness Correction LUT>
Here, a method for generating the unevenness correction LUT will be described. The unevenness correction LUT applied to the unevenness correction processing unit 64B (see FIG. 1) is generated by the following procedure.

  FIG. 19 is a flowchart showing an example of the procedure for generating the unevenness correction LUT. The calculation timing for creating the unevenness correction LUT is arbitrary and is not particularly limited. For example, a mode in which a correction value is calculated by outputting a test chart before executing a print job, and a correction value is calculated by outputting the test chart at a timing of once every time a predetermined number of prints are performed. A mode in which a correction value is calculated by outputting a test chart before printing at the timing of switching the mode, paper type, and paper size, and a correction value is calculated by outputting a test chart to the margin of the recording medium for each image output. There may be a mode in which the correction value is calculated or a mode in which the above correction value is calculated when an instruction from the user is given. The data of the unevenness correction LUT is updated at an appropriate timing.

  When the unevenness correction LUT generation process shown in FIG. 19 is started, first, a test chart used for measurement of the recording density distribution is output (step S410).

  FIG. 20 is a diagram illustrating an example of a test chart (also referred to as a test pattern) recorded on a recording sheet as a print medium. The density distribution measurement test chart 200 shown in FIG. 20 includes a plurality of types (eight types here) of belt-like patterns 200A to 200H having different gradation values. Each of the strip-shaped patterns 200A to 100H has a rectangular shape that is long along the medium width direction (x direction) orthogonal to the medium transport direction (y direction). The medium width direction is a substantial nozzle row direction by the line head of the marking portion 68 (FIG. 1), and each of the belt-like patterns 200A to 200H has a substantially uniform density in a range corresponding to the length of the nozzle row. It is formed. The “substantially uniform density” means that the gradation command value (setting value) is constant during pattern recording. By measuring the density distribution of a pattern drawn based on a command of a constant gradation value, it is possible to grasp the variation in ejection characteristics of each nozzle corresponding to the gradation value.

  In this example, patterns 200 </ b> A to 200 </ b> H with different densities are formed in order of decreasing ink density from the upstream side to the downstream side in the medium conveyance direction (from bottom to top in FIG. 20). However, the order of pattern arrangement and the number of band-like patterns (number of steps for changing density) are not particularly limited. The set gradation value for recording each strip pattern can be set as appropriate, and the number of strip patterns can be designed as appropriate. Such a test chart 200 is formed for each color by each CMYK head. Further, the present invention is not limited to a mode in which all patterns 200A to 200H are recorded on one sheet 202, and these band-shaped patterns may be divided and recorded on a plurality of sheets.

  The test chart 200 thus formed on the paper 202 is read by an offline scanner or a reading device such as an image reading sensor (inline sensor) installed in the paper conveyance path of the printing system 10. Read data (electronic image data) is acquired. From this read data, an optical density (OD) value at each position in the image is obtained, and output density data indicating an output recording density (ink density) for each nozzle corresponding to each position is obtained (FIG. 19 step S412). Based on the output density data thus obtained and the value of the input gradation value, a characteristic curve indicating the ejection characteristics (recording density characteristics) for each nozzle is acquired.

  The characteristic curve Gt of each nozzle is compared with an appropriate characteristic curve Ga serving as a reference (target density), and a correction value for an input signal value (pixel value) is determined for each nozzle according to the comparison result, and input for each nozzle. An unevenness correction LUT that defines the relationship of the output signal to the signal is obtained. In this way, a correction value table for the ejection control of each nozzle (that is, the unevenness correction LUT for each nozzle) is generated (step S414 in FIG. 19).

  Discharge correction LUTs are obtained for all nozzles, and the discharge correction LUTs for all the nozzles are stored in the unevenness correction LUT-DB 42 (see FIG. 1) (step S416 in FIG. 19). By comparing the nozzle characteristic curve Gt with the appropriate characteristic curve Ga, it is also possible to determine whether the nozzle is a non-ejection nozzle or an uncorrectable level ejection abnormal nozzle. It is also possible to form a test pattern including a so-called 1-on-n-off type line pattern and grasp the non-ejection nozzle, ejection amount abnormality, landing position error, etc. from the read result.

  A non-ejection nozzle or an ejection abnormal nozzle that cannot be corrected may be treated as a defective nozzle that cannot be used for recording, and not ejected during image recording. For defective nozzles that perform such non-ejection processing, the ejection correction LUT of the corresponding nozzle does not have to be stored in the unevenness correction LUTDB 42.

<Unevenness correction thumbnail LUT>
The unevenness correction LUT is a table data group of the LUT for each nozzle and has a large data capacity. For example, in the case of a system that uses a single-pass long line head (single-pass page wide head) that can record the entire drawing range in the long-side direction with a single paper feed on Kikuhan (636mm x 469mm) paper In the case of a system having a recording resolution of 1200 dpi, the inkjet heads for each color corresponding to the four colors of CMYK have about 30,000 nozzles per head. Since this is the number of ink colors (four colors in this example), the total number of nozzles is about 120,000.

  When the amount of ink discharged from each nozzle of the four-color head group is controlled by the LUT, an input 12-bit output 12-bit LUT corresponding to the total number of nozzles is handled. The data size of such unevenness correction LUT is very large, and if the unevenness correction LUT is directly accessed by the image conversion unit 34, the calculation efficiency is low (calculation time is required).

  In the present embodiment, the LUT data (unevenness correction thumbnail LUT) necessary for the calculation of the reduced image data is separately created from the unevenness correction LUT, thereby improving the calculation efficiency of the evaluation calculation.

  When the unevenness correction LUT to be set in the printer 12 is generated, the unevenness correction thumbnail LUT can be generated together.

  Note that a program for realizing the processing contents of the PC 14 described in the present embodiment is recorded on a CD-ROM, a magnetic disk, or other computer-readable medium (information storage medium), and the program is transmitted to a third party through the information storage medium. Can be provided. Instead of providing the program by storing the program in such a tangible storage medium, the program signal can be provided as a download service using a communication network such as the Internet. Alternatively, a function realized by the program can be provided as an ASP (Application Service Provider) service.

  In addition, a mode in which a part or all of the program for realizing the processing contents by the PC 12 described in the present embodiment is incorporated in a host control device such as a host computer, or an operation program for a central processing unit (CPU) on the printer 12 side. It is also possible to apply.

<Configuration example of inkjet printer>
Next, a configuration example of an ink jet recording apparatus that is an example of the printer 12 described in FIG. 1 will be described.

  FIG. 21 is a diagram illustrating a configuration example of the ink jet recording apparatus 310. The inkjet recording apparatus 310 includes a plurality of colors from inkjet heads 372M, 372K, 372C, and 372Y on a recording medium 324 (corresponding to a “sheet body”, which may be hereinafter referred to as “paper”) held on a drawing drum 370. Is a direct-drawing type ink jet recording apparatus that forms a desired color image by droplets of ink, and a treatment liquid (in this case, an aggregating treatment liquid) is applied onto the recording medium 324 before the ink droplets are deposited. 2 is a drop-on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method in which an ink liquid is reacted to form an image on a recording medium 324 is applied.

  As shown in the figure, the ink jet recording apparatus 310 mainly includes a paper feed unit 312, a treatment liquid application unit 314, a drawing unit 316, a drying unit 318, a fixing unit 320, and a paper discharge unit 322. The inkjet heads 372M, 372K, 372C, and 372Y of the drawing unit 316 correspond to the “marking unit 68” described in FIG. 1, and the paper discharge unit 322 in FIG. 21 corresponds to the paper discharge unit 69B in FIG.

(Paper Feeder)
A recording medium 324 that is a sheet is stacked on the paper feed unit 312. The recording media 324 are fed one by one from the paper feed tray 350 of the paper feed unit 312 to the processing liquid application unit 314. Although a sheet (cut paper) is used as the recording medium 324, a configuration in which continuous paper (roll paper) is cut into a necessary size and fed is also possible.

(Processing liquid application part)
The processing liquid application unit 314 is a mechanism that applies the processing liquid to the recording surface of the recording medium 324. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 316. When the treatment liquid comes into contact with the ink, the ink becomes a color material. And the solvent are promoted.

  The treatment liquid application unit 314 includes a paper feed drum 352, a treatment liquid drum 354, and a treatment liquid application device 356. The processing liquid drum 354 includes a claw-shaped holding means (gripper) 355 on the outer peripheral surface thereof, and the recording medium 324 is sandwiched between the claw of the holding means 355 and the peripheral surface of the processing liquid drum 354, thereby The tip can be held. A suction hole may be provided on the outer peripheral surface of the treatment liquid drum 354, and a suction unit that performs suction from the suction hole may be connected.

  The treatment liquid coating apparatus 356 can apply various methods such as a spray method and an ink jet method in addition to a roller coating method.

  The recording medium 324 to which the processing liquid is applied is transferred from the processing liquid drum 354 to the drawing drum 370 of the drawing unit 316 via the intermediate transport unit 326.

(Drawing part)
The drawing unit 316 includes a drawing drum 370, a sheet pressing roller 374, and ink jet heads 372M, 372K, 372C, 372Y. The drawing drum 370 includes claw-shaped holding means (grippers) 371 on the outer peripheral surface thereof, like the processing liquid drum 354.

  Inkjet heads 372M, 372K, 372C, and 372Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 324. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each inkjet head 372M, 372K, 372C, 372Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 324 (the rotation direction of the drawing drum 370).

  The recording medium 324 is transported at a constant speed by the drawing drum 370, and the operation of relatively moving the recording medium 324 and each of the inkjet heads 372M, 372K, 372C, 372Y in this transport direction is performed only once (that is, 1). An image can be recorded in the image forming area of the recording medium 324 in a single sub-scan).

  Here, the inkjet recording apparatus 310 using four colors of CMYK is illustrated, but the combination of the ink color and the number of colors is not limited to this embodiment, and light ink, dark ink, special ink is used as necessary. Color ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The recording medium 324 on which an image is formed by the drawing unit 316 is transferred from the drawing drum 370 to the drying drum 376 of the drying unit 318 via the intermediate conveyance unit 328.

(Drying part)
The drying unit 318 is a mechanism for drying moisture contained in the solvent separated by the color material aggregation action, and includes a drying drum 376 and a solvent drying device 378. Similar to the treatment liquid drum 354, the drying drum 376 includes a claw-shaped holding means (gripper) 377 on its outer peripheral surface. The solvent drying device 378 includes a plurality of halogen heaters 380 and a hot air jet nozzle 382. The recording medium 324 that has been dried by the drying unit 318 is transferred from the drying drum 376 to the fixing drum 384 of the fixing unit 320 via the intermediate conveyance unit 330.

(Fixing part)
The fixing unit 320 includes a fixing drum 384, a halogen heater 386, a fixing roller 388, and an in-line sensor 390 (corresponding to “reading device”). The fixing drum 384 includes claw-shaped holding means (grippers) 385 on the outer peripheral surface thereof, like the processing liquid drum 354.

  The in-line sensor 390 is a means for reading an image (including a density measurement test chart and a non-ejection detection test pattern) formed on the recording medium 324 and detecting image density, image defect, and the like. Yes, a CCD line sensor or the like is applied.

(Output section)
The paper discharge unit 322 includes a discharge tray 392, and a transfer drum 394, a conveyance belt 396, and a stretching roller 398 are provided between the discharge tray 392 and the fixing drum 384 of the fixing unit 320 so as to be in contact therewith. Is provided. The recording medium 324 is sent to the transport belt 396 by the transfer drum 394 and discharged to the discharge tray 392. Although the details of the paper transport mechanism by the transport belt 396 are not shown, the recording medium 324 after printing is held at the front end of the paper by a gripper (not shown) gripped between the endless transport belts 396, and the transport belt 396. Is carried above the discharge tray 392.

  Since the inkjet recording apparatus 310 is a single-sided printing printer, a double-sided printed matter can be finally obtained by printing one side at a time.

  Although not shown in FIG. 21, the ink jet recording apparatus 310 of the present example includes an ink storage / loading unit for supplying ink to the respective ink jet heads 372M, 372K, 372C, and 372Y, processing liquid, in addition to the above configuration. A means for supplying a treatment liquid to the applying unit 314 and a head maintenance unit for cleaning each ink jet head 372M, 372K, 372C, 372Y (wiping, purging, nozzle suction, etc. of the nozzle surface) Are provided with a position detection sensor for detecting the position of the recording medium 324 and a temperature sensor for detecting the temperature of each part of the apparatus.

<Inkjet head structure>
Next, the structure of the inkjet head will be described. Since the inkjet heads 372M, 372K, 372C, and 372Y have the same structure, hereinafter, the head is represented by reference numeral 450 as a representative thereof.

  FIG. 22A is a plan perspective view showing a structural example of the head 450, and FIG. 22B is an enlarged view of a part thereof. FIG. 23 is a perspective plan view showing another example of the structure of the head 450, and FIG. 24 is a three-dimensional configuration of one-channel droplet discharge elements (ink chamber units corresponding to one nozzle 451) serving as a recording element unit. It is sectional drawing (sectional drawing in alignment with the AA in FIG. 22) which shows this.

  As shown in FIG. 22A, the head 450 of this example includes a plurality of ink chamber units (droplet discharge elements) including nozzles 451 that are ink discharge ports, pressure chambers 452 corresponding to the respective nozzles 451, and the like. 453 has a structure in which 453 is arranged two-dimensionally in a matrix, so that a substantial nozzle interval (projection) is projected (orthogonal projection) so as to be aligned along the head longitudinal direction (direction orthogonal to the paper feed direction). Nozzle pitch) is increased.

  A nozzle row having a length corresponding to the entire width Wm of the drawing area of the recording medium 324 is configured in a direction (arrow M direction; main scanning direction) substantially orthogonal to the feeding direction (arrow S direction; sub-scanning direction) of the recording medium 324. The form to do is not limited to this example. For example, instead of the configuration of FIG. 22 (a), as shown in FIG. 23 (a), short head modules 450A in which a plurality of nozzles 451 are two-dimensionally arranged are arranged in a staggered manner and connected. There are a mode in which a line head having a nozzle row having a length corresponding to the entire width of the recording medium 324 and a mode in which the head modules 450B are connected in a row as shown in FIG.

  The pressure chamber 452 provided corresponding to each nozzle 451 has a substantially square planar shape (see FIGS. 22A and 22B), and the nozzle 451 is provided at one of the diagonal corners. An outlet for supplying ink (supply port) 454 is provided on the other side. Note that the shape of the pressure chamber 452 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, an ellipse, and the like.

  As shown in FIG. 24, the head 450 has a structure in which a nozzle plate 451A in which nozzles 451 are formed and a flow path plate 452P in which flow paths such as a pressure chamber 452 and a common flow path 455 are formed are laminated and joined. .

  The flow path plate 452P constitutes a side wall portion of the pressure chamber 452 and a flow path forming a supply port 454 as a throttle portion (most narrowed portion) of an individual supply path that guides ink from the common flow channel 455 to the pressure chamber 452. It is a forming member. Note that, for convenience of explanation, the flow path plate 452P has a structure in which one or a plurality of substrates are stacked, although it is illustrated schematically in FIG.

  The nozzle plate 451A and the flow path plate 452P can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  The common flow channel 455 communicates with an ink tank (not shown) as an ink supply source, and the ink supplied from the ink tank is supplied to each pressure chamber 452 via the common flow channel 455.

  A piezoelectric actuator 458 provided with individual electrodes 457 is joined to a diaphragm 456 constituting a part of the pressure chamber 452 (the top surface in FIG. 24). The diaphragm 456 of this example functions as a common electrode 459 corresponding to the lower electrode of the piezoelectric actuator 458. It is also possible to form the diaphragm with a non-conductive material such as silicon or resin. In this case, a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member.

  By applying a driving voltage to the individual electrode 457, the piezoelectric actuator 458 is deformed and the volume of the pressure chamber 452 is changed, and ink is ejected from the nozzle 451 due to the pressure change accompanying this.

  As shown in FIG. 22B, the ink chamber units 453 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of this example is realized. In this matrix arrangement, when the interval between adjacent nozzles in the sub-scanning direction is Ls, in the main scanning direction, each nozzle 451 is substantially equivalent to a linear arrangement with a constant pitch P = Ls / tan θ. It can be handled.

  The arrangement form of the nozzles 451 is not limited to the illustrated example, and various nozzle arrangement structures can be applied. For example, a linear array of lines, a V-shaped nozzle array, a zigzag-shaped nozzle array (such as a W-shape) having a V-shaped array as a repeating unit, and the like are also possible.

<Means for moving the head and paper relative to each other>
In the above-described embodiment, the configuration in which the recording medium is transported to the stopped head is exemplified. However, in the implementation of the present invention, a configuration in which the head is moved with respect to the stopped recording medium (the drawing medium) is also possible. is there.

<Discharge method>
The means for generating discharge pressure (discharge energy) for discharging droplets from each nozzle in the inkjet head is not limited to a piezo actuator (piezoelectric element). In addition to piezoelectric elements, various pressure generating elements (such as heaters (heating elements) in electrostatic actuators, thermal methods (methods that eject ink using the pressure of film boiling by heating of the heaters), and various other actuators) A discharge energy generating element) can be applied. Corresponding energy generating elements are provided in the flow path structure according to the ejection method of the head.

<About recording media>
The “recording medium” includes media called by various terms such as a printing medium, a recording medium, an image forming medium, an image receiving medium, and an ejection medium. In the practice of the present invention, the material, shape, etc. of the recording medium are not particularly limited, and a print on which a resin sheet such as continuous paper, cut paper, seal paper, OHP sheet, film, cloth, nonwoven fabric, wiring pattern, or the like is formed. Various sheet bodies can be used regardless of the substrate, rubber sheet, and other materials and shapes.

<Modification 1>
In the above embodiment, a printing apparatus (inkjet recording apparatus) that uses CMYK four-color inks has been exemplified, and the GCR process has been described as a process for reducing the total amount of ink. However, the present invention is not limited to CMYK four colors. Colors of ink can be used. By using inks of special colors (green, red, blue) corresponding to the secondary colors of CMY, it is possible to reduce the amount of ink by replacing the combination of two colors with one special color.

  Even when four or more colors of ink are used, the total amount of ink on both sides of all these color components is calculated and compared with a specified value (threshold) to determine whether there is an area that exceeds the specified value. can do.

<Modification 2>
In the above-described embodiment, the total ink amount on both sides is obtained for each pixel of the reduced image data. However, the unit area for evaluating the ink amount can be set to an appropriate size. Since the blocking phenomenon occurs in a certain area range, the size of the unit region can be determined from the viewpoint of the area where the blocking phenomenon can occur.

<Device application example>
In the above-described embodiment, application to an inkjet recording apparatus for color printing has been described as an example. However, the scope of application of the present invention is not limited to this example. The present invention can be applied to various printing apparatuses that form a color image using a plurality of ink colors including four colors of CMYK.

  The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the field within the technical idea of the present invention.

<Various aspects of the disclosed invention>
As will be understood from the description of the embodiment described in detail above, the present specification and drawings include disclosure of various technical ideas including the invention described below.

  (First Aspect): A printing method for forming a double-sided printed material by forming images on both front and back sides of a sheet body by a printing apparatus, and a printing target on the first side that is one side of the front and back sides of the sheet body Obtaining the first ink amount distribution indicating the ink amount distribution on the first surface from the first image data, and the second image to be printed on the second surface opposite to the first surface of the sheet body A step of obtaining a second ink amount distribution indicating the distribution of the ink amount on the second surface from the data, and a region of the overlapping positional relationship between the first surface and the second surface that are in contact with each other when a plurality of double-sided printed materials are overlaid, A step of obtaining a double-sided total ink amount indicating the sum of the ink amount on the first side and the ink amount on the second side from the first ink amount distribution and the second ink amount distribution, and the double-sided total ink amount exceeding a specified value; Process to determine whether or not Setting a color conversion condition for keeping the total ink amount on both sides of the specific area within the specified value and storing the output color when there is a specific area where the ink amount exceeds the specified value; A step of performing color conversion processing on image data of at least one of the first surface and the second surface using the set color conversion conditions, and a sheet by a printing apparatus using the image data obtained by the color conversion processing Forming an image on the body.

  According to this aspect, the front and back ink amounts in the positional relationship in which the double-sided printed materials are overlaid can be adjusted to an appropriate amount, so that image defects such as blocking can be prevented. In addition, when the ink amount is adjusted, the color conversion condition is determined so as to preserve the output color, so that a printed matter having a desired color can be obtained.

  (Second Aspect): In the printing method according to the first aspect, a color conversion condition capable of keeping the total ink amount on both sides within a specified value can be determined in advance before a print execution instruction.

  (Third Aspect): In the printing method according to the first aspect or the second aspect, the color conversion condition for keeping the total ink amount on both sides within a specified value for a specific region is either the first side or the second side It can be set as the structure applied only to one side.

  Moreover, it can be set as the structure which can designate one surface which reduces an ink amount by a user's selection.

  (Fourth aspect): In the printing method according to the first aspect or the second aspect, the ink amount on the first surface is reduced under a color conversion condition that keeps the total ink amount on both sides within a specified value for a specific region. A configuration including a first color conversion condition and a second color conversion condition for reducing the amount of ink on the second surface can be adopted.

  In reducing the total amount of ink on both sides, it is possible to perform a process for reducing the amount of ink on both the first side and the second side.

  (Fifth aspect): In the printing method according to the fourth aspect, in order to keep the total ink amount on both sides of a specific image area within a specified value, the ink amounts on both the first surface and the second surface are constant. It can be set as the structure reduced by a ratio.

  The fixed ratio may be one that reduces the ink amount at the same ratio on the first surface and the second surface, or may be one that reduces the ink amount at a different ratio. A mode in which the ratio is varied according to the type of the sheet body to be used, the use of the printed matter, and the like is possible.

  (Sixth aspect): In the printing method according to any one of the first to fifth aspects, there is a specific region of the first surface and the second surface where the total ink amount on both sides exceeds a specified value. If there is a specific area where the total ink amount on both sides exceeds a specified value, the first side and the second side are specified. The color conversion condition applied to the image data of the designated surface can be changed.

  According to the user's selection or according to the type of the sheet body, the use of the printed matter, etc., it is possible to automatically specify the surface on which the ink amount is reduced.

  (Seventh aspect): In the printing method according to any one of the first aspect to the sixth aspect, when a specific image region in which the total ink amount on both sides exceeds a specified value exists as a result of the determination. It can be configured to include a step of notifying the user that a specific area exists.

  According to this aspect, the user can determine whether or not the ink amount needs to be changed.

  (Eighth Aspect): In the printing method according to any one of the first aspect to the seventh aspect, it is preferable that the specified value can be changed according to the type of the sheet body.

  (Ninth aspect): A printing control apparatus that controls a printing apparatus that creates a double-sided printed material in which images are formed on both front and back sides of a sheet body. The first ink amount distribution indicating the ink amount distribution on the first surface is obtained from the first image data to be printed on one surface, and the second surface on the opposite side to the first surface of the sheet body is to be printed. An ink amount calculation unit for obtaining a second ink amount distribution indicating a distribution of the ink amount on the second surface from the second image data, and a first surface and a second surface that contact each other when a plurality of double-sided printed materials are overlaid. In the overlapping positional relationship area, the total ink amount on both sides indicating the sum of the ink amount on the first surface and the ink amount on the second surface is obtained from the first ink amount distribution and the second ink amount distribution. Determine whether the specified value is exceeded If there is a specific area where the total ink amount analysis unit and the total ink amount on both sides exceed the specified value, the total ink amount on both sides of the specific area is within the specified value, and the output color is And a color conversion condition changing unit that sets a color conversion condition to be stored.

  Further, the ninth aspect of the print control apparatus can be configured to appropriately combine features similar to those described in the second to eighth aspects. In this case, for items specified as “processes”, “means” and processing units (functional units) corresponding to the processes are combined.

  (Tenth aspect): In the printing control apparatus according to the ninth aspect, the image input unit that takes in the first image data and the second image data to be printed, and the input image data acquired through the image input unit An image reduction processing unit that generates reduced image data having a lower resolution than the input image data, a color conversion unit that performs color conversion processing on the reduced image data, and reduced image data that has undergone color conversion processing by the color conversion unit A gradation conversion unit that performs gradation conversion processing on the first image data obtained through the gradation conversion processing by the gradation conversion unit. While obtaining one ink amount distribution, the second ink amount distribution can be obtained from reduced image data of the second image data obtained through the gradation conversion processing by the gradation converting unit.

  When the image is printed on the printing device after gradation conversion processing and correction processing are performed on the image data, the ink amount is calculated from the image data subjected to gradation conversion processing and correction processing when calculating the ink amount. It is desirable to do.

  (Eleventh aspect): In the printing control apparatus according to the tenth aspect or the eleventh aspect, per unit area in the dot arrangement of the halftone image obtained by performing the halftone process on the signal value of the image data and the image data of the signal value A halftone dot ratio table in which a correspondence relationship with a dot ratio for each dot size is described, and a halftone data storage unit that stores ink droplet amount data for each dot size. For each of the first image data and the second image data, the distribution of the ink amount of each color used in the printing apparatus is calculated based on the halftone dot ratio table and the ink droplet amount information for each dot size, and all the colors It is possible to obtain a distribution of the total ink amount obtained by summing the ink amounts.

  The ink amount can be obtained from the halftone dot ratio table and the ink droplet amount information without actually performing halftone processing on the image data.

  (Twelfth aspect): In the print control apparatus according to any one of the ninth to eleventh aspects, when a specific region in which the total ink amount on both sides exceeds the specified value exists as a result of the determination. In addition, the display unit can be configured to notify the user that a specific area exists.

  (Thirteenth aspect): In the printing control apparatus according to the twelfth aspect, if the result of determination is that there is a specific region where the total ink amount on both sides exceeds the specified value, the display unit displays the ink amount. A configuration may be adopted in which a user interface operation screen asking whether or not to set the color conversion conditions to be reduced is displayed.

  According to this aspect, with respect to the adoption of the color conversion process for correcting the total ink amount on both sides, it is possible to adopt a configuration in which actual printing is performed after obtaining confirmation from the user of approval / rejection.

  (14th aspect): In the printing control apparatus according to the twelfth aspect or the thirteenth aspect, the content of the print image after the color conversion condition change is displayed when the color conversion condition that keeps the total ink amount on both sides within the specified value is displayed It can be configured to be displayed on the display screen of the unit.

  (Fifteenth aspect): In the print control apparatus according to any one of the ninth to fourteenth aspects, a specific area in which the total ink amount on both sides exceeds a specified value among the first surface and the second surface is It can be configured to include an operation unit that allows the user to specify at least one surface that reduces the amount of ink in the case where it exists.

  (Sixteenth aspect): In the printing control apparatus according to any one of the ninth to fifteenth aspects, a print condition instruction unit that instructs a printing condition and a target value of a color of printing by the printing apparatus are at least device-dependent A target profile described by the correspondence relationship between the device-independent second color space values corresponding to the first color space value and the CMYK color at which the color output by the printing apparatus corresponds to at least the second color space value. A color conversion lookup table storage unit that stores a printer profile described as information, a printer profile generation unit that generates a printer profile that contains an ink amount within an upper limit value of the total ink amount specified by the printing condition instruction unit, The target profile specified from the print condition instruction section, the printer profile generated by the printer profile generation section, And a color conversion look-up table generation unit for generating a color conversion look-up table.

  (Seventeenth aspect): A program for causing a computer to realize the function of the print control apparatus according to any one of the ninth to sixteenth aspects can be provided.

  (Eighteenth aspect): A printing system comprising the print control apparatus according to any one of the ninth to sixteenth aspects and a printing apparatus controlled by the print control apparatus can be provided.

  DESCRIPTION OF SYMBOLS 10 ... Printing system, 12 ... Printer, 14 ... Computer terminal (PC), 16 ... Monitor, 18 ... Input device, 20 ... Image data, 22 ... Image input interface part, 24 ... Image data DB, 26 ... Printing condition instruction | indication part , 28 ... print condition DB, 30 ... color conversion LUT-DB, 40 ... image processing unit, 42 ... image reduction processing unit, 44 ... color conversion unit, 46 ... color conversion LUT generation system, 48 ... tone conversion unit, 48A ... density conversion section, 48B ... unevenness correction processing section, 50 ... ink amount calculation section, 52 ... double-sided total ink amount analysis section, 60 ... image process board, 62 ... color conversion section, 64 ... gradation conversion section, 66 ... half Tone processing unit, 68 ... marking unit, 69B ... paper discharge unit, 82 ... printer profile generation unit, 84 ... color conversion LUT generation unit, 310 ... inkjet recording apparatus, 324 ... recording medium , 372M, 372K, 372C, 372Y ... inkjet head, 451 ... nozzle

Claims (18)

A printing method for forming a double-sided printed material by forming images on both sides of a sheet body with a printing device,
Obtaining a first ink amount distribution indicating an ink amount distribution on the first surface from the first image data to be printed on the first surface which is one of the front and back surfaces of the sheet body;
Obtaining a second ink amount distribution indicating the ink amount distribution on the second surface from the second image data to be printed on the second surface opposite to the first surface of the front and back of the sheet body;
A double-sided image showing the sum of the ink amount on the first surface and the ink amount on the second surface for the overlapping region of the first surface and the second surface that are in contact with each other when a plurality of the double-sided printed materials are stacked. Obtaining a total ink amount from the first ink amount distribution and the second ink amount distribution;
Determining whether the total ink amount on both sides exceeds a specified value;
When there is a specific area where the total amount of ink on both sides exceeds the specified value, the color conversion condition for keeping the total amount of ink on both sides of the specified area within the specified value and storing the output color A process of setting
Performing a color conversion process on image data of at least one of the first surface and the second surface using the set color conversion conditions;
Forming an image on the sheet by the printing apparatus using the image data obtained by the color conversion process;
Including printing method.   The printing method according to claim 1, wherein a color conversion condition capable of keeping the total ink amount on both sides within the specified value is determined in advance before a print execution instruction.   The color conversion condition for keeping the total ink amount on both sides of the specific region within the specified value is applied to only one of the first surface and the second surface. Printing method.   The color conversion condition for keeping the total ink amount on both sides of the specific area within the specified value includes the first color conversion condition for reducing the ink amount on the first surface and the ink amount on the second surface. The printing method according to claim 1, further comprising: a second color conversion condition.   5. The printing method according to claim 4, wherein the amount of ink on both sides of the first surface and the second surface is reduced at a constant ratio in order to keep the total amount of ink on both sides of the specific region within the specified value. A step of designating at least one surface of the first surface and the second surface for reducing the ink amount when there is a specific area where the total ink amount on both surfaces exceeds the specified value;
When there is a specific area where the total amount of ink on both sides exceeds the specified value, a color conversion condition applied to the image data of the designated side of the first side and the second side is The printing method according to claim 1, wherein the printing method is changed.   7. The method according to claim 1, further comprising: notifying a user that the specific area exists when the specific area where the total ink amount on both sides exceeds the specified value exists as a result of the determination. The printing method according to any one of the above.   The printing method according to claim 1, wherein the specified value can be changed according to a type of the sheet body. A printing control device that controls a printing device that creates a double-sided printed material in which images are formed on both sides of a sheet body,
A first ink amount distribution indicating an ink amount distribution on the first surface is obtained from first image data to be printed on the first surface which is one surface of the front and back surfaces of the sheet body, and the front and back surfaces of the sheet body are An ink amount calculation unit for obtaining a second ink amount distribution indicating an ink amount distribution on the second surface from the second image data to be printed on the second surface opposite to the first surface;
A double-sided total indicating the sum of the ink amount on the first surface and the ink amount on the second surface in a region where the first surface and the second surface contact each other when a plurality of sheets of the double-sided printed material are stacked. A double-sided total ink amount analysis unit that determines an ink amount from the first ink amount distribution and the second ink amount distribution and determines whether the double-sided total ink amount exceeds a specified value;
When there is a specific area where the total amount of ink on both sides exceeds the specified value, a color conversion condition for storing the output color within the specified value while keeping the total amount of ink on both sides of the specific area within the specified value A color conversion condition change part for setting
A printing control apparatus comprising: An image input unit for capturing the first image data and the second image data to be printed;
An image reduction processing unit that generates reduced image data having a lower resolution than the input image data from the input image data acquired through the image input unit;
A color conversion unit that performs color conversion processing on the reduced image data;
A gradation conversion unit that performs gradation conversion processing on the reduced image data that has undergone color conversion processing by the color conversion unit, and
The ink amount calculation unit obtains the first ink amount distribution from the reduced image data of the first image data obtained through the gradation conversion processing by the gradation conversion unit, while the gradation amount by the gradation conversion unit. The print control apparatus according to claim 9, wherein the second ink amount distribution is obtained from reduced image data of the second image data obtained through a tone conversion process. Halftone dot ratio that describes the correspondence between the image data signal value and the dot ratio by dot size per unit area in the dot arrangement of a halftone image obtained by halftone processing the image data of the signal value A halftone data storage unit for storing ink drop amount data for each table and dot size is provided.
The ink amount calculation unit uses the first image data and the second image data in the printing apparatus based on the halftone dot ratio table and information on the ink droplet amount for each dot size. The printing control apparatus according to claim 9 or 10, wherein the distribution of the ink amount of each color is calculated, and the distribution of the total ink amount obtained by summing up the ink amounts of all colors is obtained.   12. The display device according to claim 9, further comprising: a display unit that notifies the user that the specific area exists when the specific area where the total ink amount on both sides exceeds the specified value exists as a result of the determination. The print control apparatus according to any one of the above.   As a result of the determination, when there is a specific area where the total ink amount on both sides exceeds the specified value, the display unit asks whether or not the color conversion condition for reducing the ink amount can be set. The print control apparatus according to claim 12, wherein an interface operation screen is displayed.   The print control according to claim 12 or 13, wherein the content of the print image after the color conversion condition is changed when the color conversion condition for keeping the total ink amount on both sides within the specified value is adopted is displayed on the display screen of the display unit. apparatus.   The user may designate at least one surface of the first surface and the second surface to reduce the ink amount when there is a specific area where the total ink amount on both surfaces exceeds the specified value. The print control apparatus according to claim 9, further comprising an operation unit that can perform the operation. A printing condition instruction section for instructing printing conditions;
A target profile described by a correspondence relationship between values of a device-independent second color space corresponding to a value of at least a device-dependent first color space, and a target color value for printing by the printing device; and output by the printing device A color conversion lookup table storage unit in which a printer profile described as CMYK information corresponding to at least the value of the second color space is stored;
A printer profile generation unit that generates a printer profile that stores the ink amount within the upper limit value of the total ink amount specified from the print condition instruction unit;
A color conversion lookup table generation unit that generates a color conversion lookup table based on the target profile specified from the printing condition instruction unit and the printer profile generated by the printer profile generation unit;
The printing control apparatus according to any one of claims 9 to 15.   The program for making a computer implement | achieve the function of the printing control apparatus of any one of Claim 9 to 16. A print control apparatus according to any one of claims 9 to 16,
The printing apparatus controlled by the printing control apparatus;
A printing system comprising:

Images