JP5919763B2 - Printing control apparatus and printing apparatus - Google Patents

Description

  The present invention relates to image processing for printing, and more particularly to image processing when a sheet is conveyed in a deformed state during printing.

  Printing in which ink dots are formed on a recording medium (for example, paper) is known. In such printing, the recording medium may float from the platen toward the recording head due to the formation of ink dots. For example, the recording medium may be rounded and float from the platen toward the recording head. In order to obtain a high-quality printing result, a technique for suppressing such floating of the recording medium has been proposed. For example, Patent Document 1 proposes a technique for preventing a recording medium from floating in the direction of a recording head by forming the recording medium into a wavy shape.

JP 11-138923 A JP 2004-106978 A JP 2007-59972 A JP 07-285251 A JP 2001-261188 A JP 2004-122609 A JP 2003-040507 A

  By the way, when the recording medium (also referred to as a sheet) is conveyed while being deformed in a wave shape, the distance between the print head and the sheet may vary depending on the position on the sheet. As a result, the printed image may be uneven due to the wavy deformation of the sheet.

  A main advantage of the present invention is to provide a technique capable of suppressing unevenness of a printed image due to a wavy deformation of a sheet.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples.

Application Example 1 In a state where the sheet is deformed in a wave shape along the first direction, a sheet conveying unit that conveys the sheet in a second direction intersecting the first direction, and a plurality of droplets that eject droplets A print head having nozzles, a head moving unit that moves the print head in parallel with the first direction, and driving the print head during the movement of the print head toward the sheet that has been deformed into a wave shape. A print control device that causes a print execution unit including a print head drive unit that discharges droplets to execute printing, and performs correction processing to generate corrected image data from input image data. A correction data generation unit that executes the correction data supply unit that supplies the corrected image data to the print execution unit, and the process of generating the corrected image data includes: When the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed at the time of printing, it is printed on a plurality of first type areas on the sheet. The spatial frequency spectrum is different between the plurality of first type printed partial images and the plurality of second type printed partial images printed in the plurality of second type regions on the sheet. A process of generating the corrected image data by executing the correction process using the input image data, wherein the plurality of first type regions and the plurality of second type regions are in the second direction. The print control device, wherein the first type region and the second type region are alternately arranged along the first direction.

  According to this configuration, if the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing, a plurality of first types on the sheet are provided. The spectrum of the spatial frequency is between the plurality of first type printed partial images printed in the region and the plurality of second type printed partial images printed in the plurality of second type regions on the sheet. In a different manner, correction processing using input image data is executed to generate corrected image data. For this reason, the graininess unevenness of the printed image due to the wavy deformation of the sheet can be reduced, and as a result, the graininess unevenness can be suppressed.

  The present invention can be realized in various forms, for example, a print control method and a print control device, a print method and a print device, a computer program for realizing the functions of these methods or devices, It can be realized in the form of a recording medium (for example, a non-temporary recording medium) on which a computer program is recorded.

1 is a block diagram of a printing apparatus 600 as an embodiment of the present invention. 2 is an explanatory diagram of a printing apparatus 600. FIG. It is explanatory drawing which shows the landing position of droplet D1, D2. It is the schematic which shows the example of a graininess nonuniformity. It is a flowchart of a printing process. It is the schematic of a halftone process. It is a flowchart of a halftone process. It is explanatory drawing of the correction process using random number value RND. An example of determining the dot formation state is shown. It is the schematic which shows the example of a change of the granularity in a printing process. It is the schematic of the halftone process in 2nd Example. It is a flowchart of the halftone process in 2nd Example. It is explanatory drawing of the halftone process in 2nd Example. An example of determining the dot formation state when the total number of dot formation states is 2 is shown. It is explanatory drawing which shows another Example of a reference | standard gap.

A. First embodiment:
Next, embodiments of the present invention will be described based on examples. FIG. 1 is a block diagram of a printing apparatus 600 as an embodiment of the present invention. The printing apparatus 600 includes a control apparatus 100 and a print execution unit 200.

  The control device 100 is a computer that controls the operation of the printing device 600. The control device 100 communicates with a CPU 110, a volatile memory 120 such as a DRAM, a nonvolatile memory 130 such as an EEPROM, an operation unit 170 such as a touch panel, a display unit 180 such as a liquid crystal display, and an external device. And a communication unit 190 which is an interface of the above. The communication unit 190 may be, for example, a so-called USB interface or an interface compliant with IEEE802.3.

  The nonvolatile memory 130 stores a program 132, correction data 134a, and a matrix 136. The CPU 110 implements various functions including the function of the printer driver M100 by executing the program 132. The printer driver M100 causes the print execution unit 200 to execute printing using image data to be printed (also referred to as “target image data”). The target image data is, for example, image data supplied to the printing apparatus 600 from an external device (for example, a computer or a USB flash memory).

  In this embodiment, the printer driver M100 includes a corrected data generation unit M104 and a corrected data supply unit M106. The corrected data generation unit M104 generates corrected print data (also referred to as “corrected image data”) from the target image data by executing correction processing using the correction data 134a. The corrected data supply unit M106 supplies the corrected image data to the print execution unit 200. The print execution unit 200 executes printing according to the received corrected image data.

  The print execution unit 200 forms dots on the sheet by ejecting ink droplets toward the sheet (print medium). The printed image is represented by a dot pattern. The print execution unit 200 includes a control circuit 210, a print head 250, a head moving unit 240, and a sheet conveying unit 260. A plurality of nozzles for ejecting ink droplets are provided on the bottom surface of the print head 250 (not shown). In this embodiment, the print head 250 can eject four types of inks of cyan, magenta, yellow, and black. The sheet conveyance unit 260 conveys the sheet in a predetermined conveyance direction. The head moving unit 240 moves the print head 250 in a direction orthogonal to the transport direction. Printing of the image proceeds by repeating the operation of ejecting ink droplets toward the sheet while the print head 250 moves to a position facing the sheet and the operation of the sheet conveying unit 260 conveying the sheet. To do. The control circuit 210 includes a movement control unit 212 that controls the head moving unit 240, a head drive unit 214 that controls the print head 250, and a conveyance control unit 216 that controls the sheet conveyance unit 260. The control circuit 210 controls the head moving unit 240, the print head 250, and the sheet conveying unit 260 in accordance with the corrected image data (print data) from the control device 100.

  FIG. 2A shows a perspective view of the printing apparatus 600. In the figure, three directions Dx, Dy, and Dz are shown. The two directions Dx and Dy are horizontal directions, respectively, and the Dz direction is a vertically upward direction. The Dy direction is a direction orthogonal to the Dx direction. The Dy direction is parallel to the moving direction of the print head 250 (hereinafter, the Dy direction is also referred to as “first direction Dy”). The Dx direction is the same as the conveyance direction of the sheet 300 (hereinafter, the Dx direction is also referred to as “conveyance direction Dx” or “second direction Dx”). Hereinafter, the Dx direction is also referred to as “+ Dx direction”, and the opposite direction of the Dx direction is also referred to as “−Dx direction”. The same applies to the + Dy direction, the -Dy direction, the + Dz direction, and the -Dz direction.

  The sheet conveyance unit 260 includes a conveyance motor 263, a first roller 261, a second roller 262, a sheet base 265, and a pressing unit 269. The sheet base 265 supports the sheet 300 from the lower surface approximately horizontally. The two rollers 261 and 262 are arranged at positions facing the upper surface of the sheet base 265. The first roller 261 faces the −Dx direction side portion of the sheet table 265, and the second roller 262 faces the + Dx direction side portion of the sheet table 265. Each of the rollers 261 and 262 is a roller parallel to the Dy direction, and is rotationally driven by the transport motor 263. The sheet 300 is sandwiched between the rollers 261 and 262 and the sheet base 265 and is conveyed in the conveying direction Dx by the rotating rollers 261 and 262.

  In this embodiment, when the printing apparatus 600 performs printing on a rectangular sheet of a specific size (for example, A4 size paper), the short side of the rectangular sheet is parallel to the transport direction Dx, and the long side is the first. The sheet is arranged so as to be parallel to the direction Dy. As a result, the size of the printing apparatus 600 in the conveyance direction Dx can be reduced as compared with the case where the long side of the sheet is parallel to the conveyance direction Dx.

  The head moving unit 240 includes a moving motor 242 and a support shaft 244. The support shaft 244 is disposed between the first roller 261 and the second roller 262 and extends in parallel with the first direction Dy. The support shaft 244 supports the print head 250 slidably along the support shaft 244. The moving motor 242 is connected to the print head 250 by a belt (not shown). The moving motor 242 moves the print head 250 in parallel with the first direction Dy. In the present embodiment, the head driving unit 214 (FIG. 1) moves while the print head 250 moves in the first direction Dy and when the print head 250 moves in the direction opposite to the first direction Dy (−Dy direction). In each of the inside and the outside, the print head 250 is driven to eject droplets (bidirectional printing).

  FIG. 2B is an enlarged perspective view of the head moving unit 240 and the sheet conveying unit 260. In the drawing, a cross section perpendicular to the conveying direction Dx of the sheet base 265 (a cross section at a position between the two rollers 261 and 262) is also shown. As illustrated, the seat base 265 includes a plurality of low support portions 265a and a plurality of high support portions 265b. The high support portion 265b supports the sheet 300 at a higher position than the low support portion 265a. The low support portions 265a and the high support portions 265b are alternately arranged along the first direction Dy. 2C illustrates a cross-sectional view of the high support portion 265b, and FIG. 2D illustrates a cross-sectional view of the low support portion 265a. 2C and 2D each show a cross section parallel to the transport direction Dx and the vertical upward direction Dz.

  As shown in FIG. 2C, the high support portion 265b includes five portions 265b1 to 265b5 arranged side by side from the −Dx direction side to the + Dx direction side. The first portion 265b1 is a portion facing the first roller 261, the third portion 265b3 is a portion facing the print head 250 (a plurality of nozzles 250n), and the fifth portion 265b5 is a portion facing the second roller 262. It is an opposing part. Each of these three portions 265b1, 265b3, 265b5 has an upper surface having the same height, and supports the sheet 300 from the lower surface (hereinafter, the height of the upper surface of these portions is referred to as “reference height SH”). . The remaining two portions 265b2 and 265b4 are recessed below the reference height SH and are separated from the seat 300. As shown in the figure, the print head 250 is provided with a plurality of nozzles 250n whose positions in the transport direction Dx are different from each other. In the present embodiment, such a plurality of nozzles 250n are provided for each CMYK ink.

  As shown in FIG. 2D, the low support portion 265a includes five portions 265a1 to 265a5 arranged side by side from the −Dx direction side to the + Dx direction side. The first portion 265a1 and the fifth portion 265a5 are the same as the first portion 265b1 and the fifth portion 265b5 in FIG. The third portion 265a3 faces the print head 250 (a plurality of nozzles 250n), similarly to the third portion 265b3 in FIG. However, the height of the upper surface of the third portion 265a3 is lower than the reference height SH. Further, the upper surface of the third portion 265a3 is inclined obliquely upward from the −Dx side to the + Dx side (the closer to the second roller 262, the higher). The remaining two portions 265a2, 265a4 are recessed below the reference height SH and are separated from the seat 300.

  A pressing portion 269 is disposed above the second portion 265a2. The pressing portion 269 extends obliquely downward from the position facing the upper surface of the first portion 265a1 toward the conveyance direction Dx side. The height of the end of the pressing portion 269 on the conveyance direction Dx side is lower than the reference height SH. The sheet 300 sent out from between the first roller 261 and the first portion 265a1 is bent by the pressing portion 269 and sent below the reference height SH. On the conveyance direction Dx side of the pressing unit 269, the lower surface of the sheet 300 is supported by the third portion 265a3 and gradually approaches the reference height SH. However, at a position facing the print head 250 (a plurality of nozzles 250n), the height of the sheet 300 is lower than the reference height SH. On the conveyance direction Dx side of the third portion 265a3, the sheet 300 is sandwiched between the second roller 262 and the fifth portion 265a5.

  As shown in FIG. 2B, in this embodiment, the pressing portions 269, the low support portions 265a, and the high support portions 265b are alternately arranged along the first direction Dy. Accordingly, the sheet conveying unit 260 deforms the sheet 300 in the conveying direction Dx in a state of being deformed in a wave shape along the first direction Dy intersecting the conveying direction Dx between the first roller 261 and the second roller 262. Transport. The reason why the sheet 300 is deformed in a wave shape is to prevent the sheet 300 from being lifted from the sheet base 265 toward the print head 250 due to the sheet 300 being rounded. Assuming that the sheet 300 is conveyed flat without being deformed, the sheet that has received ink droplets from the nozzles 250n may be unintentionally deformed as indicated by reference numeral 302 in FIG. There is. Such unintended deformation can cause printing defects. In particular, in this embodiment, the short side of the rectangular sheet is parallel to the transport direction Dx, and the long side is parallel to the first direction Dy. In this case, there is a high possibility that unintended deformation occurs compared to the case where the long side is parallel to the transport direction Dx. Therefore, the printing apparatus 600 according to the present embodiment suppresses unintended deformation by deforming the sheet 300 in a wave shape along the first direction Dy that intersects the transport direction Dx.

  FIG. 3 shows the landing positions (positions in the first direction Dy) of the droplets D1 and D2 ejected from the print head 250 on the sheet. The first droplet D1 indicates a droplet discharged from the print head 250 moving in the + Dy direction, and the second droplet D2 indicates a droplet discharged from the print head 250 moving in the −Dy direction. 3A shows a virtual case where printing is performed on a flat sheet 300f (hereinafter also referred to as “reference sheet 300f”) without deformation, and FIG. 3B is deformed in a wave shape. A case where printing is performed on the sheet 300 of the embodiment will be described.

  The nozzle 250n discharges droplets D1 and D2 vertically downward. The nozzle 250n moves horizontally above the sheets 300 and 300f when the droplets D1 and D2 are discharged. Accordingly, when viewed from the sheets 300 and 300f, the droplets D1 and D2 fly obliquely in the moving direction of the print head 250. As shown in FIG. 3A, in order to form dots at the same target position Py1, the print head 250 that moves in the + Dy direction has a first droplet D1 at a position on the −Dy direction side of the target position Py1. The print head 250 that moves in the −Dy direction discharges the second droplet D2 at a position on the + Dy direction side of the target position Py1. In this way, the ejection timing of the droplets D1 and D2 is adjusted.

  A gap GPs in FIG. 3A indicates a gap between the nozzle surface np and the reference sheet 300f. Here, the nozzle surface np is a plane including the positions of the plurality of nozzles 250n, and is a plane including a position through which the moving nozzle 250n can pass. In the present embodiment, the nozzle surface np is a substantially horizontal plane. The gap is the distance between the nozzle surface np and the sheet, measured perpendicular to the nozzle surface np. Hereinafter, the gap GPs of the reference sheet 300f is also referred to as a reference gap GPs.

  As shown in FIG. 3B, the sheet 300 actually used is deformed in a wave shape along the first direction Dy. In the present embodiment, the gap of the highest portion (portion supported by the high support portion 265b) in the sheet 300 is the same as the reference gap GPs. Hereinafter, the plane 300s corresponding to the reference sheet 300f is referred to as a “reference plane 300s”. The height of the reference surface 300s is the same as the reference height SH in FIGS. 2 (C) and 2 (D).

  As illustrated, the region on the sheet 300 is divided into a first type region A1 and a second type region A2 that are alternately arranged along the first direction Dy. The first type region A1 is a region including a portion pressed by the pressing portion 269. The second type region A2 is a region including a portion supported by the high support portion 265b.

  Also in this embodiment, the ejection timing of the droplets D1 and D2 is adjusted on the assumption that printing is performed on a flat reference surface 300s separated from the nozzle 250n by the reference gap GPs. FIG. 3B shows droplets D1 and D2 ejected to form dots at the same target position Py1 as in FIG. When printing is performed on the first type region A1 far from the reference surface 300s, the landing positions of the droplets D1 and D2 are shifted from the target position Py1. The landing position of the first droplet D1 is a position shifted from the target position Py1 to the moving direction side (+ Dy direction side) of the print head 250, and the landing position of the second droplet D2 is the print head 250 from the target position Py1. The position is shifted to the moving direction side (−Dy direction side). Such a positional deviation of dots is larger as the difference between the gap between the nozzle surface np and the sheet 300 and the reference gap GPs is larger.

  Generally, in order to print an image, a plurality of dots separated from each other are formed. Here, when the difference between the gap and the reference gap GPs is large, some dots may approach other dots due to misalignment of dots, and some dots may be other dots. May be connected. As a result, the printed image may appear rough as compared to the case where there is no dot misalignment (the grain (dot) pattern representing the printed image may appear rough). Such a change in graininess is larger in the first type region A1 far from the reference surface 300s than in the second type region A2 close to the reference surface 300s. The observer of the printed image recognizes the difference in graininess between the first type area A1 and the second type area A2 as graininess unevenness.

  FIG. 4 is a schematic diagram illustrating an example of graininess unevenness. FIG. 4A shows target image data Id (image data to be printed). The target image data Id represents an image Idi having a uniform gradation value. FIG. 4B shows a printed image Ip obtained by printing the target image data Id on a sheet deformed in a wave shape without correction. As shown in the drawing, graininess unevenness occurs between the first type region A1 and the second type region A2. In order to suppress such unevenness in graininess, the printing apparatus 600 (FIG. 1) performs image correction using the correction data 134a in image processing for printing.

  The first type region A1 and the second type region A2 are gaps from the nozzle surface np (FIG. 3B) to a position between the lowest part of the pressing part 269 and the upper surface of the high support part 265b. (Referred to as “gap threshold GPth”). That is, the first type region A1 is a region in which the gap is in the range equal to or larger than the gap threshold value GPth. The second type region A2 is a region where the gap is in a range less than the gap threshold value GPth. The gap threshold value GPth can be, for example, a gap corresponding to an intermediate height between the lowest portion of the pressing portion 269 and the upper surface of the high support portion 265b.

  Next, printing using the correction data 134a will be described. FIG. 5 is a flowchart of a printing process executed by the printing apparatus 600 (FIG. 1). The printer driver M100 starts print processing in response to a user instruction (for example, an operation of the operation unit 170 by a user or a command from a computer (not shown) connected to the communication unit 190). The printer driver M100 acquires target image data to be printed from an external device connected to the communication unit 190.

  In the first step S200, the corrected data generation unit M104 (FIG. 1) converts the target image data into bitmap data (rasterization processing). The pixel data included in the bitmap data is, for example, a pixel color with gradation values (for example, 256 gradations of 0 to 255) of three color components of red (R), green (G), and blue (B). RGB pixel data representing Further, the pixel density of the bitmap data is the same as the printing resolution (the highest dot density).

  In the next step S210, the corrected data generation unit M104 (FIG. 1) converts the RGB pixel data included in the bitmap data into gradation values (dot formation state) of four color components of cyan, magenta, yellow, and black. Is converted into CMYK pixel data representing the color of the pixel with a number of gradations larger than the total number (four values in this embodiment), for example, 256 gradations from 0 to 255 (color conversion processing). The color conversion process is performed using a lookup table that associates RGB pixel data with CMYK pixel data.

  In the next step S220, the corrected data generation unit M104 (FIG. 1) converts the bitmap data including the CMYK pixel data into dot data representing the dot formation state for each pixel (halftone process). In the present embodiment, the corrected data generation unit M104 generates dot data according to an error diffusion method using the matrix 136. Details of step S220 will be described later.

  In the next step S230, the corrected data generation unit M104 (FIG. 1) generates print data from the dot data. The print data is data expressed in a data format that can be interpreted by the print execution unit 200. In the present embodiment, the corrected data generation unit M104 generates print data so as to perform so-called bidirectional printing.

  In the next step S240, the corrected data supply unit M106 supplies the print data to the print execution unit 200. The print execution unit 200 prints an image according to the received print data.

FIG. 6 is a schematic diagram of halftone processing, and FIG. 7 is a flowchart of halftone processing. Hereinafter, description will be given along the flowchart of FIG. The process of FIG. 7 is executed for each ink color and for each pixel. This process determines the dot formation state for each pixel. In the present embodiment, the dot formation state is determined from the following four states having different ink amounts (that is, dot sizes (density expressed by dots)).
A) Large dot B) Medium dot (Medium dot density <Large dot density)
C) Small dot (small dot density <medium dot density)
D) No dot

  In the first step S504, the corrected data generation unit M104 (FIG. 1) uses the matrix 136 (FIG. 1) and the error buffer EB (FIG. 6) to determine the error value of the pixel to be processed (target pixel). Et is calculated. As will be described later, the error buffer EB stores a density error (tone error value) in each pixel. The error buffer EB is provided in the volatile memory 120 (FIG. 1). The matrix 136 assigns a weight greater than zero to pixels arranged at a predetermined relative position around the pixel of interest. In the matrix 136 of FIG. 6, the symbol “+” represents the pixel of interest, and weights a to m are assigned to surrounding pixels. The sum of the weights a to m is 1. The corrected data generation unit M104 calculates the weighted sum of the error values of the surrounding pixels as the error value Et of the target pixel according to this weight.

  In the next step S506, the corrected data generation unit M104 calculates the sum of the error value Et and the tone value of the target pixel (hereinafter also referred to as the input tone value Vin. For example, the cyan tone value). Calculated as one gradation value Va. A matrix 136 illustrated in FIG. 6 is a matrix when the dot state determination process proceeds in the −Dy direction. When the dot state determination process proceeds in the + Dy direction, a matrix is used in which the relative position in the first direction Dy is inverted with the pixel of interest at the center.

  In the next step S508, the corrected data generation unit M104 refers to the correction data 134a and generates a random value RND according to the position of the target pixel in the first direction Dy. FIG. 8A is a graph showing correction data 134a (hereinafter referred to as “amplitude coefficient data 134a”). The horizontal axis indicates the position Py in the first direction Dy, and the vertical axis indicates the amplitude coefficient Amc. As will be described later, the amplitude coefficient Amc is a coefficient representing the size of a range of values that can be taken by the random value RND (hereinafter referred to as a domain of the random value RND) when generating the random value RND (amplitude). The larger the coefficient Amc, the larger the definition area).

  As shown in FIG. 8A, in this embodiment, the amplitude coefficient Amc is set to “0” at the positions Pya1 to Pya6 of the pressing portion 269, and the amplitude coefficient Amc at the positions Pyb1 to Pyb7 of the high support portion 265b. Is set to “1”. That is, the amplitude coefficient Amc is “1” at the position Py where the gap is the same as the gap (reference gap GPs) of the reference plane 300s in FIG. At other positions Py, the amplitude coefficient Amc is determined by linear interpolation. The amplitude coefficient data 134a is table data representing the amplitude coefficient Amc of the positions Pya1 to Pya6 and Pyb1 to Pyb7.

  Note that the amplitude coefficient Amc of the other position Py is not limited to linear interpolation, and may be determined by other various interpolations (for example, interpolation using a spline function or a sine function). It may be determined according to the shape. Generally, as the amplitude coefficient data 134a, a correction amount (amount of change in graininess) between the case where the printing position in the first direction Dy is in the first type region A1 and the case in the second type region A2. The data defining the printing position dependency of the correction amount can be adopted so that the difference is different. Here, the amplitude coefficient data 134a preferably defines a correction amount such that the printed image becomes relatively rough in the second type area A2 compared to the first type area A1. The amplitude coefficient data 134a may be data in any other format that defines the relationship between the amplitude coefficient Amc and the position Py (for example, a lookup table that defines the relationship between the amplitude coefficient Amc and the position Py). The amplitude coefficient data 134a is determined in advance.

  FIG. 8B is a graph showing the relationship between the amplitude coefficient Amc and the domain RR of the random value RND. The horizontal axis represents the amplitude coefficient Amc, and the vertical axis represents the random number value RND. The lower limit RNDL and the upper limit RNDH indicate the lower limit and the upper limit of the domain RR of the random value RND, respectively. In the figure, the domain RR is hatched. In the present embodiment, the lower limit RNDL is fixed to “0.0”. The upper limit RNDH (> lower limit RNDL) is directly proportional to the amplitude coefficient Amc. Therefore, the width RNDW of the domain RR is wider as the amplitude coefficient Amc is larger. In the present embodiment, the upper limit RNDH is 85 when the amplitude coefficient Amc is “0”, and the upper limit RNDH is 175 when the amplitude coefficient Amc is “1”.

  FIG. 8C is a graph showing the position dependency of the domain RR. The horizontal axis indicates the position Py in the first direction Dy, and the vertical axis indicates the random number value RND. In the figure, the domain RR is hatched. As described above, since the amplitude coefficient Amc changes according to the position Py in the first direction Dy, the domain RR also changes according to the position Py. As shown in the figure, in the first type region A1 including the positions Pya1 to Pya6 of the pressing portion 269, the definition area RR is narrow, and in the second type area A2 including the positions Pyb1 to Pyb7 of the high support portion 265b, RR is wide.

  As described above, the corrected data generation unit M104 determines the amplitude coefficient Amc according to the position Py of the target pixel, determines the domain RR according to the determined amplitude coefficient Amc, and determines the determined domain RR. Generates a random value RND. The generation of the random value RND is performed for each pixel. In the present embodiment, the random value RND is uniformly distributed within the domain RR.

  In subsequent steps S510 to S540 of FIG. 7, the corrected data generation unit M104 pays attention based on the magnitude relationship using the first gradation value Va, the random value RND, and the three reference threshold values Th1 to Th3. The dot formation state of the pixel is determined. In this embodiment, the input gradation value Vin is expressed in 256 levels from 0 to 255. The first reference threshold Th1 is a threshold reference for outputting small dots (for example, zero). The first corrected threshold value Th1r is “first reference threshold value Th1 + random number value RND”. The second reference threshold Th2 is a threshold reference for outputting medium dots (for example, 84). The second corrected threshold Th2r is “second reference threshold Th2 + random number value RND”. The third reference threshold Th3 is a threshold reference for outputting large dots (for example, 170). The third corrected threshold Th3r is “third reference threshold Th3 + random number value RND”.

The corrected data generation unit M104 determines the dot formation state as follows.
A) First gradation value Va> third corrected threshold value Th3r (S510: Yes): dot formation state = “large dot” (S515)
B) The first gradation value Va is equal to or smaller than the third corrected threshold value Th3r, and the first gradation value Va> second corrected threshold value Th2r (S520: Yes): dot formation state = “medium dot” (S525) )
C) The first gradation value Va is equal to or smaller than the second corrected threshold value Th2r, and the first gradation value Va> first corrected threshold value Th1r (S530: Yes): dot formation state = “small dot” (S535) )
D) The first gradation value Va is equal to or less than the first corrected threshold Th1r (S530: No): dot formation state = “no dot” (S540)

  As described above, in this embodiment, the corrected data generation unit M104 (FIG. 1) corrects the threshold value using the random value RND. Then, the corrected data generation unit M104 determines the dot formation state of the target pixel based on the magnitude relationship between the input gradation value Vin and the corrected threshold values Th1r, Th2r, and Th3r. In the present embodiment, the processing shown in FIG. 7 (determination of dot formation state) is an example of correction processing (image correction). Hereinafter, the image data to be corrected (here, CMYK bitmap data) is also referred to as “input image data”. Further, the entire series of processes (S220 and S230 in FIG. 5) from the correction process to the generation of the print data is “the corrected image data (specifically, the corrected image data by executing the correction process). This is an example of “process for generating (completed print data)” (hereinafter referred to as “corrected image data generation process”, more specifically, “corrected print data generation process”).

  FIG. 8D, FIG. 8E, and FIG. 8F are graphs showing the position dependency of the three threshold values Th3r, Th2r, and Th1r, respectively. The horizontal axis indicates the position Py in the first direction Dy, and the vertical axis indicates the corrected threshold values Th3r, Th2r, Th1r. In the drawing, the range of values that each corrected threshold Th3r, Th2r, Th1r can take is hatched (hereinafter referred to as “threshold ranges TR3, TR2, TR1”). Each of the threshold ranges TR3, TR2, and TR1 changes according to the position Py similarly to the definition area RR of the random value RND. That is, in the first type region A1 including the positions Pya1 to Pya6 of the pressing portion 269, each threshold range TR3, TR2, TR1 is narrow, and in the second type region A2 including the positions Pyb1 to Pyb7 of the high support portion 265b, Each threshold range TR3, TR2, TR1 is wide. Thus, the relationship between the threshold ranges TR3, TR2, and TR1 that change depending on the position Py and the granularity of the printed image will be described later.

In step S550 (FIG. 7) next to the determination of the dot formation state, the corrected data generation unit M104 acquires a gradation value (referred to as dot gradation value Vb) associated with the determined dot formation state. . In this embodiment, the dot gradation value is set as follows.
A) Large dot: dot gradation value Vb = 255
B) Medium dot: dot gradation value Vb = 170
C) Small dot: dot gradation value Vb = 84
D) No dot: dot gradation value Vb = zero The dot gradation value Vb represents the gradation value (density) represented by the dot formation state. Such a correspondence is incorporated in advance in the corrected data generation unit M104 as a dot gradation value table.

In the next step S570, the corrected data generation unit M104 calculates a target error value Ea. The target error value Ea is expressed by the following equation.
Target error value Ea = first gradation value Va−dot gradation value Vb
The corrected data generation unit M104 registers the calculated target error value Ea in the error buffer EB as the error value of the target pixel.

  As described above, the corrected data generation unit M104 determines the dot formation state of each print pixel for each ink color.

  FIG. 9 shows an example of determining the dot formation state. The determination example in FIG. 9A shows a determination example in the first type region A1. In the example of FIG. 9A, the domain of the random number value RND is 0 to 85, and the domain width RNDW is relatively narrow (85). The determination example in FIG. 9B shows a determination example in the second type region A2. In the example of FIG. 9B, the domain of the random number value RND is 0 to 175, and the domain width RNDW is relatively wide (175). These drawings show an example of determining a pixel line in which 16 pixels are formed side by side in the first direction Dy. In the figure, the input gradation value Vin, the first gradation value Va, the random number value RND, the corrected threshold values Th3r, Th2r, Th1r, the dot formation state DS, the dot gradation value Vb, and the target error are shown. The value Ea is shown. In the column of the dot formation state DS, any symbol of “no dot”, “small dot dt1”, “medium dot dt2”, and “large dot dt3” (“no dot” is blank) is displayed.

  Here, the input gradation value Vin is assumed to be the same value (120) for all the pixels. Further, for the sake of simplicity, it is assumed that all errors generated in a certain pixel are added to the first gradation value Va of a pixel adjacent in the + Dy direction. For example, as shown in FIG. 9A, the first gradation value Va of the second pixel P2 that is the second from the top is the input gradation value Vin (120) of the pixel P2 and the first gradation value one higher than the first gradation value Va. It is the sum (156) with the target error value Ea (36) generated in the pixel P1.

  When the definition area width RNDW is narrow, it is difficult to form a large (high density) dot as compared to a wide area. For example, in the example shown in FIG. 9A, the dot formation state DS is either “small dot dt1” or “medium dot dt2”. There is no “large dot dt3” pixel having the highest density. The ratio of the number of pixels (0) of the large dot dt3 to the total number of pixels (16) is zero (0/16). Therefore, for an observer of this dot-formed pattern, the grains (dots) representing the image appear relatively fine. There is also no “dotless” pixel with the lowest density. The ratio of the “no dot” pixel number (0) to the total pixel number (16) is zero (0/16). Therefore, for the observer of the pattern in the dot formation state, the grains (dots) representing the image appear to be distributed relatively evenly (the printed image looks smooth). Thus, when the domain width RNDW is relatively narrow, the dot pattern looks fine. The average value of the dot gradation values Vb is “122” which is approximately the same as the input gradation value Vin (120).

  On the other hand, when the defined area width RNDW is wide, larger (higher density) dots are more easily formed than when the defined area width RNDW is narrow. For example, in the example shown in FIG. 9B, the ratio of the number of pixels of the large dot dt3 is increased (3/16 = 0.0) as compared with the case where the domain width RNDW is relatively narrow (FIG. 9A). 19). Therefore, for the observer of the pattern in the dot formation state, the grains (dots) representing the image look relatively coarse. In the determination example of FIG. 9B, the ratio of the number of pixels “without dots” is increased (5/16 = 0) as compared with the case where the domain width RNDW is relatively narrow (FIG. 9A). .31). Therefore, the observer of the pattern in the dot formation state appears that the grains (dots) representing the image are not evenly distributed but are locally biased. Thus, when the domain width RNDW is relatively wide, the dot pattern looks rough. The average value of the dot gradation value Vb is “117” which is approximately the same as the input gradation value Vin (120).

  As described above, the dot formation pattern is different between FIGS. 9A and 9B (that is, the graininess is different). When the domain width RNDW of the random number value RND is large, the dot pattern can be made coarser than when it is small. The reason for this is as follows. When the random number value RND is large, the corrected threshold values Th1r, Th2r, and Th3r are larger than when the random number value RND is small, so that the dots generated in the target pixel tend to be small (or no dots are generated). For example, although the first gradation value Va (164) of the third pixel P3 in FIG. 9B is larger than the first gradation value Va (105) of the fourth pixel P4, the third pixel P3. The dot size (no dot) is smaller than the dot size (small dot dt1) of the fourth pixel P4. In addition, the smaller the dot, the larger the target error value Ea. Therefore, when the random number value RND is large, the target pixel can disperse a large error value Ea to surrounding pixels.

  When a large error value Ea generated in a pixel having a large random number value RND is added to the first gradation value Va of a target pixel having a small random number value RND, even if the input gradation value Vin of the target pixel is small, A large dot dt3 can be formed (for example, the seventh pixel P7 in FIG. 9B). The formation of the large dot dt3 resulting from the random value RND is promoted as the domain width RNDW of the random value RND is wider.

  When the large dot dt3 is formed on the target pixel due to the random value RND, the dot size of the surrounding pixels is reduced. Therefore, when the ratio of the number of pixels of the large dot dt3 is large, the density distribution represented by the dot pattern becomes unequal compared to the case where it is small. Therefore, the dot pattern can be roughened by increasing the domain width RNDW.

  On the other hand, when the random value RND is small, the corrected threshold values Th1r, Th2r, and Th3r are small compared to the case where the random number value RND is large. For example, although the first gradation value Va (188) of the fifth pixel P5 in FIG. 9B is smaller than the first gradation value Va (238) of the sixth pixel P6, the fifth pixel P5. The dot size (large dot dt3) is larger than the dot size (medium dot dt2) of the sixth pixel P6. In addition, the larger the dot, the smaller the target error value Ea. Therefore, when the random value RND is small, the target pixel can disperse the small error value Ea to the surrounding pixels.

  When a small error value Ea generated in a pixel having a small random value RND is added to the first gradation value Va of a target pixel having a large random value RND, even if the input gradation value Vin of the target pixel is large, In some cases, dots are not formed (for example, the eighth pixel P8 in FIG. 9B). Generation of such “no dot” pixels due to the random value RND is promoted as the domain width RNDW of the random value RND is wider.

  When a “no dot” pixel occurs due to the random number value RND, the dot size of surrounding pixels increases. Therefore, when the ratio of the number of “no dots” pixels is large, the density distribution represented by the dot pattern becomes unequal compared to the case where the number of pixels is small. Therefore, the dot pattern can be roughened by increasing the domain width RNDW.

  FIG. 10 is a schematic diagram illustrating an example of a change in graininess in the printing process. FIG. 10A shows input image data IDin (CMYK bitmap data to be subjected to halftone processing). The input image data IDin represents an image having a uniform gradation value (hereinafter also referred to as “input image Iin”). The input image Iin represents, for example, the same image as the image Idi in FIG. FIG. 10B shows corrected print data IDc (corrected image data IDc) generated by executing halftone processing (FIG. 7: correction processing) using the input image data IDin. The areas A1 and A2 and the directions Dx and Dy in the figure indicate the areas A1 and A2 and the directions Dx and Dy based on the printed image when the corrected image data IDc is printed. As described with reference to FIGS. 8A to 8F, in the second type region A2, the definition range width RNDW of the random number value RND is wider than that in the first type region A1. As described with reference to FIGS. 9A and 9B, when the definition area width RNDW is wide, the pattern of the dot formation state is rough as compared with the narrow case. Accordingly, in the corrected image data IDc of FIG. 10B, the dot formation state pattern in the second type region A2 is coarser (hereinafter referred to as the corrected image) than the dot formation state pattern in the first type region A1. The image represented by the data IDc is called “corrected image Ic”).

  If the sheet is conveyed in a flat state without being deformed at the time of printing (for example, when printing on the reference sheet 300f in FIG. 3B), printing obtained by printing the corrected image data IDc The completed image is the same as the corrected image Ic. FIG. 10C is a graph showing a schematic example of a spatial frequency spectrum in such a printed image (corrected image Ic). The horizontal axis indicates the spatial frequency SF (unit: cycle / millimeter), and the vertical axis indicates the intensity m. The first graph mcA1 shows the spectrum of the printed image in the first type region A1, and the second graph mcA2 shows the spectrum of the printed image in the second type region A2. This spatial frequency spectrum is a so-called winner spectrum. Such a spatial frequency spectrum is obtained as follows. First, image data representing the printed corrected image Ic is generated by optically reading the printed corrected image Ic. Next, the image data is converted into image data representing a color in the L * a * b * space. Next, a two-dimensional FFT (Fast Fourier Transform) is performed on the L * component image. Next, the result of the two-dimensional FFT is converted into data expressed in a polar coordinate system. And the spectrum of FIG.10 (C) is obtained by making the data represented by a polar coordinate system into one dimension using the averaging about an angle.

  As illustrated, the spectrum differs between the first type region A1 (first graph mcA1) and the second type region A2 (second graph mcA2). Specifically, in the second type region A2 (second graph mcA2), the intensity m of the low frequency component lower than the specific spatial frequency SF1 is stronger than in the first type region A1 (first graph mcA1). This indicates that the dot pattern looks rougher in the second type region A2 than in the first type region A1.

  FIG. 10D is a schematic diagram of the virtual printed image IPin. The virtual printed image IPin indicates a printed image printed on a wavy sheet using the input image data IDin without performing correction using the random number value RND. As described with reference to FIG. 4B, the printed image looks rougher in the first type area A1 than in the second type area A2.

  FIG. 10E is a schematic diagram of a printed corrected image IPc obtained by printing the corrected image data IDc on a wave-shaped sheet. The position dependency of the graininess change (position in the first direction Dy) in the printed corrected image IPc is the position dependence of the graininess change caused by the wavy deformation of the sheet (FIG. 10D) and the image. The position dependence of the change in graininess due to correction (FIG. 10B) is obtained in total. Here, the position dependency of the graininess change in the virtual printed image IPin in FIG. 10D is opposite to the position dependence of the graininess change in the corrected image Ic in FIG. Therefore, in the printed corrected image IPc, the difference in graininess between the first type area A1 and the second type area A2 is reduced. That is, the unevenness in graininess is small compared to the case where the input image data IDin is printed without correction.

  FIG. 10F is a graph showing a schematic example of the spatial frequency spectrum in the printed corrected image IPc. The horizontal axis indicates the spatial frequency SF (unit: cycle / millimeter), and the vertical axis indicates the intensity m. The first graph mpA1 represents the spectrum of the printed image in the first type region A1, and the second graph mpA2 represents the spectrum of the printed image in the second type region A2. As described in FIG. 3B, in the second type region A2, the change in graininess due to the wavy deformation of the sheet is small, so the second graph mpA2 is the second graph mcA2 in FIG. Is roughly the same. On the other hand, in the first type region A1, the graininess changes due to the wavy deformation of the sheet (the printed image becomes rough), so the spectrum in the first type region A1 (first graph mpA1) Compared with the spectrum in the corrected image Ic in the flat case (first graph mcA1 in FIG. 10C), it is closer to the spectrum in the second type region A2 (second graph mpA2).

  As described above, in the first embodiment, as described with reference to FIGS. 10B and 10C, the input image data IDin (FIG. 10A) represents an image with uniform gradation values. In addition, when the sheet is conveyed in a flat state without being deformed during printing (for example, when printing on the reference sheet 300f in FIG. 3B), in the printed image, a plurality of first type regions Correction processing (FIG. 7) is performed so that the spectrum of the spatial frequency differs between the plurality of printed partial images printed on A1 and the plurality of printed partial images printed on the plurality of second type regions A2. ) Is executed to generate corrected image data IDc. Here, the printed image is the same image as the corrected image Ic shown in FIG. That is, the plurality of first type regions A1 and the plurality of second type regions A2 are regions extending along the transport direction Dx, and each first type region A1 and each second type region A2 are in the first direction. Alternating along Dy. Accordingly, it is possible to reduce unevenness in graininess of the printed image due to the wavy deformation of the sheet. In particular, in the present embodiment, the correction process (FIG. 7) is executed so that the printed partial image in the second type area A2 becomes rougher than the printed partial image in the first type area A1. Corrected image data IDc is generated. Therefore, when the printed partial image of the first type region A1 becomes rougher than the printed partial image of the second type region A2 due to the wavy deformation of the sheet, the printing of the second type region A2 is performed. Since the granularity of the completed partial image can be brought close to the granularity of the printed partial image in the first type region A1, unevenness in granularity can be appropriately suppressed.

  In the first embodiment, as described with reference to FIGS. 9A, 9B, 10A, and 10B, the input image data IDin (FIG. 10A) is assumed. Represents a uniform image of gradation values, and when a sheet is conveyed in a flat state without being deformed at the time of printing, a plurality of printed partial images of a plurality of first type regions A1, a plurality of The correction process (FIG. 7) is executed so that the ratio of the print pixels in the dot presence state (large dot dt3) having the highest density differs from the plurality of printed partial images in the second type region A2. The dot formation state for each print pixel is determined. Accordingly, the spatial frequency spectrum can be made different between the printed partial images of the first type region A1 and the second type region A2 (FIG. 10C). As a result, it is possible to reduce graininess unevenness of the printed image due to the wavy deformation of the sheet.

  In FIG. 3, the specific range GR is indicated by hatching. The specific range GR is a range in which the gap between the nozzle surface np and the sheet is less than the gap threshold GPth. As shown in the figure, the first type region A1 is a region where the gap between the sheet 300 and the nozzle 250n (nozzle surface np) is outside the specific range GR, and the second type region A2 is a specific range of the gap. It is a region in the GR. As shown in FIG. 10C, the image correction (the determination process of the dot formation state (FIG. 7)) makes the spatial frequency spectrum different between the first type region A1 and the second type region A2. The graininess unevenness of the printed image due to the gap of the partial region (first type region A1) deviating from the specific range GR can be reduced. In particular, since the specific range GR that is the gap range of the second type region A2 is a range less than the gap threshold value GPth, the first type region A1 having a relatively large gap and the second type region A2 having a relatively small gap. Graininess unevenness between the two can be reduced. Here, as described with reference to FIGS. 9A and 9B, the image correction is a ratio of the number of pixels in the dot formation state of the maximum density in the second type region A2 as compared with the first type region A1. To increase. Accordingly, when the printed partial image of the first type region A1 becomes rougher than the printed partial image of the second type region A2 due to the wavy deformation of the sheet 300, the second type region A2 Since the granularity of the printed partial image can be brought close to the granularity of the printed partial image in the first type region A1, unevenness in granularity can be suppressed.

  Further, in the first embodiment, the corrected data generation unit M104 (FIG. 1) uses the input tone value Vin of the target pixel and the peripheral located around the target pixel in the halftone process (correction process) of FIG. Using the error value Et obtained in the pixel and the random value RND, the dot formation state of the pixel of interest and the target error value Ea of the pixel of interest according to the dot formation state of the pixel of interest are determined. As shown in FIG. 8C, the corrected data generation unit M104 uses a correction parameter (more specifically, a random number value RND) used in determining the dot formation state according to the error diffusion method. The possible range (definition area RR) is changed according to the position Py of the target pixel in the first direction Dy. Accordingly, it is possible to change the characteristics of the dot formation state according to the printing position in the first direction Dy. As a result, it is possible to easily suppress the graininess unevenness of the printed image due to the wavy deformation along the first direction Dy of the sheet 300.

  In the first embodiment, as shown in FIGS. 2 and 3, the sheet conveying unit 260 includes a plurality of high support portions 265 b that support the sheet 300 from the lower surface. The plurality of high support portions 265b are arranged side by side along the first direction Dy at positions facing the print head 250 that moves parallel to the first direction Dy. In addition, the sheet conveying unit 260 moves the sheet 300 downward from the upper surface (more specifically, downward from the contact position (reference height SH) between the high support unit 265b and the sheet 300). A plurality of pressing portions 269 to be pressed are included. The position of each pressing portion 269 in the first direction Dy is disposed between two adjacent high support portions 265b. Therefore, the sheet conveying unit 260 can appropriately deform the sheet 300 into a wave shape. In particular, in the present embodiment, the positions in the first direction Dy of the plurality of pressing portions 269 and the positions in the first direction Dy of the plurality of high support portions 265b are alternately arranged. Therefore, since the sheet 300 is deformed into a wave shape that repeats peaks and valleys, the possibility that the sheet 300 is unintentionally deformed as indicated by reference numeral 302 in FIG. 2C can be reduced.

  In the first embodiment, as described with reference to FIG. 10D, when printing is performed on the sheet 300 deformed in a wave shape without performing image correction, the first type region A1 and the second type region are used. Graininess will differ from A2. Specifically, the granularity of the first type area A1 is larger than the granularity of the second type area A2 (the printed image of the first type area A1 is larger than the printed image of the second type area A2). ) In order to suppress such graininess unevenness, it is preferable to reduce the graininess difference between the two types of regions A1 and A2. Here, it is difficult to further improve the granularity of the printed image in the first type area A1 without changing the configuration of the printing apparatus 600 (to make the image finer). Therefore, in this embodiment, the graininess between the two types of areas A1 and A2 is reduced by reducing the graininess of the second type area A2 (by roughening the printed image of the second type area A2). The difference is reduced.

B. Second embodiment:
FIG. 11 is a schematic diagram of halftone processing in the second embodiment, and FIG. 12 is a flowchart of halftone processing in the second embodiment. Unlike the first embodiment of FIGS. 6 and 7, in the second embodiment, matrices 136A to 136F that change according to the position Py in the first direction Dy are used instead of the random number value RND. In FIG. 12, the same reference numerals are assigned to the same steps as those in FIG. The procedure of the printing process is the same as that in the embodiment of FIG. The configuration of the printing apparatus that executes the printing process is the same as that of the printing apparatus 600 of FIGS. 1 and 2 except that the nonvolatile memory 130 stores six matrices 136A to 136F instead of the matrix 136. The same.

  FIGS. 13A to 13F show examples of six matrices 136A to 136F, respectively. In the drawing, a first direction Dy and a second direction Dx are shown. One square represents one pixel. The symbol “+” indicates the target pixel. The position of each pixel is a relative position with respect to the target pixel. The numerical value described in each pixel indicates a weighting factor. A value obtained by normalizing the weighting factor of each pixel so that the sum of the weighting factors of all the pixels becomes 1 is the actual weighting. Each of the matrices 136A to 136F is a matrix when the dot state determination process proceeds in the -Dy direction. When the dot state determination process proceeds in the + Dy direction, a matrix is used in which the relative position in the first direction Dy is inverted with the pixel of interest at the center.

  FIG. 13G is a table showing the granularity evaluation values GE of the respective matrices 136A to 136F. The graininess evaluation value GE is obtained by quantifying the graininess (roughness of the image) of the printed image, and is calculated according to the formula of FIG. The larger the graininess evaluation value GE, the rougher the printed image. Here, u is a spatial frequency (unit: cycle / millimeter), and WS (u) is the above-described winner spectrum. VTF (u) is a visual spatial frequency characteristic and is calculated by the equation of FIG. D is the average density of the printed image used for calculating the winner spectrum. L in the equation of FIG. 13I is an observation distance (the unit is millimeter), and in this embodiment, L = 300 mm. Note that a uniform gray image (a gray image represented by a CMY composite) is used to calculate the winner spectrum. In this embodiment, the L * of the printed image used for calculating the graininess evaluation value GE is approximately 50, and the print resolution is 600 dpi (dot per inch). Further, when printing an image used for calculating the winner spectrum, the image is printed on a flat sheet corresponding to the reference plane 300s (FIG. 3B). The calculation method of the winner spectrum WS (u) and the graininess evaluation value GE is described in, for example, the following document “Journal of the Photographic Society of Japan Vol. 60, No. 6 (1997) Image Quality Evaluation of Inkjet Printer Makoto Fujino” Has been.

  As shown in FIG. 13G, the order of the matrices 136A to 136F is the order from the smallest granularity evaluation value GE. Even when the input image data is the same, the first matrix 136A generates a dot pattern that looks fine, and the sixth matrix 136F generates a dot pattern that appears coarse. That is, even if the input image data is the same, the spatial frequency spectrum of the dot pattern is different for each of the matrices 136A to 136F. Further, the ratio of the print pixel having the highest density dot state may be different for each of the matrices 136A to 136F. The corrected data generation unit M104 can change the roughness of the pattern in the dot formation state by switching the matrix.

  Next, description will be given along the flowchart of FIG. In the first step S502, the corrected data generation unit M104 (FIG. 1) refers to the amplitude coefficient data 134a (FIG. 8A), and the amplitude coefficient Amc associated with the position of the target pixel in the first direction Dy. Use to select a matrix. FIG. 13J is a schematic diagram showing the relationship between the amplitude coefficient Amc and the matrix. The horizontal axis shows the range of the amplitude coefficient Amc from zero to one. As illustrated, the range of the amplitude coefficient Amc is divided into six partial ranges AA1 to AA6 by five boundary values Amc1 to Am5. Six matrices 136A to 136F are associated with the six partial ranges AA1 to AA6 on a one-to-one basis. The larger the amplitude coefficient Amc of the partial range, the larger the granularity evaluation value GE of the matrix. In the present embodiment, the widths of the partial ranges AA1 to AA6 are the same. However, the width of some partial ranges may be different from the width of other partial ranges.

  FIG. 13K is a graph showing the relationship between the position Py in the first direction Dy and the granularity evaluation value GE of the selected matrix. The horizontal axis indicates the position Py, and the vertical axis indicates the granularity evaluation value GE of the selected matrix. As shown in the figure, in the first type region A1, matrices 136A, 136B, and 136C having a relatively small granularity evaluation value GE are selected. In the second type region A2, matrices 136D, 136E, and 136F having a relatively large granularity evaluation value GE are selected. That is, as in the first embodiment of FIGS. 10B and 10C, the second type region A2 has a coarser dot pattern (the first type region A1 and the first type region A1) than the first type region A1. The spatial frequency spectrum differs between the second type region A2).

  The corrected data generation unit M104 uses the selected matrix instead of the random value RND to determine the dot formation state as in the first embodiment of FIG. The next steps S504 and S506 in FIG. 12 are the same as steps S504 and S506 in FIG. 7 (the first gradation value Va is determined). In subsequent steps S510b to S540, the corrected data generation unit M104 determines the dot formation state of the pixel of interest based on the magnitude relationship between the first gradation value Va and the reference threshold values Th1 to Th3. In steps S510b, S520b, and S530b, reference threshold values Th3, Th2, and Th1 are used instead of the corrected threshold values Th3r, Th2r, and Th1r, respectively. Subsequent steps S550 and S570 are the same as steps S550 and S570 in FIG. 7, respectively.

  As described above, in the second embodiment, the correction parameter (more specifically, the matrix) used in determining the dot formation state according to the error diffusion method is the position of the target pixel in the first direction Dy. It changes according to Py. Therefore, it is possible to change the characteristics of the dot formation state according to the position in the first direction Dy. As a result, it is possible to easily suppress unevenness in the granularity of the printed image due to the wavy deformation of the sheet.

  In particular, in the second embodiment, as described with reference to FIG. 13K, in the second type region A2, the matrix granularity evaluation value GE is larger than that in the first type region A1. Therefore, when the input image data IDin as shown in FIG. 10A is printed, the printed partial image of the second type region A2 is similar to that in FIGS. 10B and 10C. The corrected image data IDc is generated so as to be coarser than the printed partial image of the first type area A1. Therefore, the graininess unevenness can be appropriately suppressed.

  In the second embodiment, the corrected data generation unit M104 selects a matrix associated with the position Py (amplitude coefficient Amc) in the first direction Dy from the six matrices 136A to 136F. Therefore, the graininess can be smoothly changed as compared with the case where the total number of matrices is small (for example, 2). As a result, graininess unevenness can be appropriately suppressed. As the total number of matrices, various numbers of 2 or more can be adopted. In any case, the corrected data generation unit M104 preferably uses a plurality of matrices having different granularity evaluation values GE. As shown in FIG. 13K, the closer the position Py of the target pixel in the first direction Dy is to the positions Pya1 to Pya6 of the pressing portion 269, the smaller the granularity evaluation value GE is, and the position Py is the high support portion 265b. It is preferable that the granularity evaluation value GE is larger as the positions are closer to the positions Pyb1 to Pyb7. In this way, it is possible to appropriately suppress graininess unevenness. Note that the graininess evaluation value GE may vary depending on printing conditions (for example, ink type, sheet type, and printing resolution). Therefore, it is preferable to evaluate the graininess evaluation value GE for each matrix in accordance with actual printing conditions.

  Also in this embodiment, as in the first embodiment of FIG. 9, the density is the highest between the printed partial image of the first type area A1 and the printed partial image of the second type area A2. You may comprise a matrix so that the ratio of the printing pixel of a high dot presence state (large dot dt3) may differ.

  The second embodiment is the same as the first embodiment except that a plurality of matrices 136A to 136F are used instead of the random value RND. Therefore, the second embodiment has various effects similar to those of the first embodiment. The process of FIG. 12 is an example of “correction process”.

  In the present embodiment, the total number of dot formation states may be two. The corrected data generation unit M104 (FIG. 1) follows, for example, the flowchart obtained by omitting the step SRb (S520b, S525, S530b, S535) for the medium dot dt2 and the small dot dt1 from the flowchart of FIG. The dot formation state may be determined. Also in this case, it is possible to reduce unevenness in the granularity of the printed image due to the wavy deformation of the sheet.

C. Third embodiment:
In the first embodiment shown in FIG. 7, the total number of dot formation states may be two (that is, two gradations of “with dot” and “without dot”). FIG. 14 shows an example of determining the dot formation state when the total number of dot formation states is two. In FIG. 14, the process is simplified as in FIG. FIG. 14 shows a dot formation state of a pixel line in which 25 pixels are formed side by side in the first direction Dy. In the figure, the input gradation value Vin, the first gradation value Va, the random number value RND, the corrected threshold value Thr, the dot formation state DS, the dot gradation value Vb, the target error value Ea, It is shown. Unlike the determination example of FIG. 9, in the determination example of FIG. 14, the dot formation state is either “no dot” or “large dot dt3” (hereinafter, the large dot dt3 is simply referred to as “dot dt3”). Called). The reference threshold value is 128, and the corrected threshold value Thr is “reference threshold value (128) + random number value RND”. In addition, the upper limit RNDH (FIG. 8B) of the random number value RND changes in the range of 85 to 128. The processing for determining the dot formation state is the same as that in FIG. 7 in which step SRa (S520, S525, S530, S535) for medium dot dt2 and small dot dt1 is omitted (in step S510, the first step). 3) The corrected threshold value Thr is used instead of the corrected threshold value Th3r.

  FIG. 14A shows an example of determination in the first type region (for example, the first type region A1 in FIG. 10B). In the example of FIG. 14A, the domain of the random value RND is 0 to 85, and the domain width RNDW is relatively narrow (85). The determination example in FIG. 14B shows a determination example in the second type region (for example, the second type region A2 in FIG. 10B). In the example of FIG. 14B, the definition area of the random number value RND is 0 to 128, and the definition area width RNDW is relatively wide (125).

  When the definition area width RNDW is narrow, the deviation of the arrangement of the dots dt3 is smaller than when the definition area width RNDW is wide. For example, in the example of FIG. 14A, pixels of “dot dt3” and “no dot” are arranged approximately alternately. There is only one portion where pixels of the same type continue (in the first portion Pva, two “dotless” pixels continue). Therefore, it seems to the observer of this dot pattern that the grains (dots) representing the image are distributed relatively evenly (the printed image looks smooth). The average value of the dot gradation values Vb is “122” which is approximately the same as the input gradation value Vin (120).

  On the other hand, when the defined area width RNDW is wide, the dots dt3 are arranged in a biased manner as compared with the narrow case. For example, in the example of FIG. 14B, pixels in which the dot dt3 is formed are continuous at the three portions Pd1 to Pd3. In addition, “no dot” pixels continue in five portions Pv1 to Pv5. Therefore, for an observer of this dot pattern, the dot pattern looks rough. The average value of the dot gradation values Vb is “122” which is approximately the same as the input gradation value Vin (120).

  As described above, when the total number of dot formation states is 2, as in the first embodiment, when the domain width RNDW of the random number value RND is large, the dot pattern is roughened compared to the case where the random number is small. Can do. The reason for this is as follows. As described with reference to FIG. 9, when the large error value Ea generated in the pixel having a large random value RND is added to the first gradation value Va of the pixel of interest having a small random value RND, the input gradation value Vin of the pixel of interest is added. Even if is small, dot dt3 can be formed. On the contrary, when the small error value Ea generated in the pixel having a small random value RND is added to the first gradation value Va of the pixel of interest having a large random value RND, the input gradation value Vin of the pixel of interest is large. However, dots may not be formed. The generation of “no dot” pixels due to the random value RND and the generation of “dot dt3” pixels are promoted as the domain width RNDW of the random value RND is wider. Accordingly, the wider the domain width RNDW of the random number value RND, the more likely the dot distribution becomes uneven. As a result, the dot pattern can be roughened by increasing the domain width RNDW. That is, the spatial frequency spectrum can be made different between the first type region A1 and the second type region A2 by changing the domain width RNDW.

  As described above, also in the present embodiment, the corrected data generation unit M104 (FIG. 1) changes the domain width RNDW according to the position Py as shown in FIGS. 8B and 8C. Thus, similar to the embodiment of FIG. 10, it is possible to reduce the unevenness of the granularity of the printed image due to the wavy deformation of the sheet.

  The third embodiment is the same as the first embodiment except for the point that the total number of dot formation states is different. Therefore, the third embodiment has various effects similar to those of the first embodiment.

D. Fourth embodiment:
FIG. 15A is an explanatory diagram showing another embodiment of the reference gap. FIG. 15A shows the landing positions of the droplets D1 and D2 and the sheet 300, as in FIG. In this embodiment, the printing apparatus 600 shown in FIGS. 1 and 2 is used. Then, instead of the portion supported by the high support portion 265b of the sheet 300, the gap GPsa of the portion pressed downward by the pressing portion 269 is used as a reference gap (hereinafter referred to as a reference from the nozzle 250n (nozzle surface np)). The plane 300sa separated by the gap GPsa is referred to as “reference plane 300sa”). In the present embodiment, the ejection timing of the droplets D1 and D2 is adjusted assuming that printing is performed on the reference surface 300sa (in the drawing, the droplets D1 and D2 have the same target position in the first direction Dy). It is assumed that dots are formed on Py1). Accordingly, the smaller the gap, that is, the closer the sheet 300 is to the nozzle 250n, the greater the positional deviation of the dots. Therefore, in the present embodiment, the dot pattern in the first type region A1a in which the gap is outside the range (specific range GRa) equal to or greater than the gap threshold GPth is compared to the second type region A2a in which the gap is in the specific range GRa. Corrected image data (print data) is generated so that the image becomes rough. In the drawing, the specific range GRa is indicated by hatching.

  The pattern depending on the position Py of the amplitude coefficient Amc is the same as the pattern in which “1” and “0” of the amplitude coefficient Amc in the embodiment of FIG. That is, the amplitude coefficient Amc is set to “1” at the positions Pya1 to Pya6 of the pressing portion 269, and the amplitude coefficient Amc is set to “0” at the positions Pyb1 to Pyb7 of the high support portion 265b (not shown). That is, at the position where the gap is the same as the reference gap GPsa of the reference surface 300sa (position Py in the first direction Dy), the amplitude coefficient Amc is “1”.

  FIG. 15B is an explanatory view showing still another embodiment of the reference gap. Similarly to FIG. 15A, FIG. 15B also illustrates droplets D1a and D1b ejected from the print head 250 moving in the + Dy direction and droplets ejected from the print head 250 moving in the −Dy direction. The landing positions of D2a and D2b and the seat 300 are shown. In this embodiment, the printing apparatus 600 shown in FIGS. 1 and 2 is used. The gap GPsb at the intermediate position between the lowest portion of the pressing portion 269 and the upper surface of the high support portion 265b is used as a reference (hereinafter, referred to as a plane 300sb separated from the nozzle 250n (nozzle surface np) by the gap GPsb). Is referred to as “reference plane 300 sb”). The ejection timing of the droplets D1a, D1b, D2a, and D2b is adjusted assuming that printing is performed on the reference surface 300sb (in the drawing, the droplets D1a and D2a form a tod at the same target position Py1a. It is assumed that the droplets D1b and D2b form dots at the same target position Py1b). Accordingly, as the gap becomes farther from the reference gap GPsb, the positional deviation of the dots increases. Therefore, in the present embodiment, in the first type regions A1b1 and A1b2 in which the absolute value of the difference between the gap and the reference gap GPsb is not more than a specific value and the gap is outside the range GRb, the gap is within the range GRb. The corrected image data (print data) is generated so that the dot pattern becomes coarse compared to the certain second type area A2b. In the drawing, the range GRb is indicated by hatching.

  The position Py dependency of the amplitude coefficient Amc is as follows. That is, the amplitude coefficient Amc is set to “0” at each of the positions Pya1 to Pya6 of the pressing portion 269 and the positions Pyb1 to Pyb7 of the high support portion 265b. Specifically, in the intermediate position between the adjacent pressing part 269 and the high support part 265b, the amplitude is the same at the position where the gap is the same as the reference gap GPsb of the reference surface 300sb (position Py in the first direction Dy). The coefficient Amc is set to “1”.

  Each of FIG. 15A and FIG. 15B can be applied to the above-described embodiments.

E. Variations:
(1) As the correction processing executed so that the spatial frequency spectrum differs between the printed partial image of the first type region and the printed partial image of the second type region, In addition to the correction process, various processes can be employed. For example, the domain RR of the random number value RND described above is not limited to the range described with reference to FIG. 8B, and other various ranges can be employed. For example, the lower limit RNDL of the domain RR, or both the lower limit RNDL and the upper limit RNDH may be negative values. The negative random number value RND can increase the ratio of the number of pixels of the large dot dt3 by reducing the corrected threshold values Th1r, Th2r, and Th3r. Further, the random value RND may be selected from a plurality of discrete values. For example, in the example of FIG. 8B, the random number value RND may be either the lower limit RNDL or the upper limit RNDH (binary random number). Further, the halftone process (correction process) in step S220 of FIG. 5 may be a process using a dither matrix instead of the error diffusion method. In this case, it is preferable to prepare a plurality of dither matrices having different granularity evaluation values GE. The corrected data generation unit M104 (FIG. 1) may select a dither matrix according to the print position in the first direction Dy as in the embodiment of FIG. 13 (K). In this case, the dither matrix changes according to the position of the print pixel in the first direction Dy. In addition, determining the dot formation state by changing the dither matrix according to the position in the first direction Dy is an example of the correction process. Further, the corrected data generation unit M104 adds a random number to the RGB gradation value of the bitmap data to be processed in step S210 in FIG. 5 or the CMYK gradation value of the bitmap data to be processed in step S220. By doing so, the spatial frequency spectrum may be changed. In this case, the bit map data to which random numbers are added is an example of input image data, and the addition of random numbers is an example of correction processing. A series of processes from addition of random numbers to generation of print data is an example of “corrected print data generation process”.

(2) As shown in FIG. 2D, the gap between the nozzle 250n and the sheet 300 may differ depending on the position in the transport direction Dx. In the present embodiment, the gap is smaller at the position of the nozzle 250n on the + Dx direction side than at the position of the nozzle 250n on the −Dx direction side. Therefore, in each of the above-described embodiments, the corrected data generation unit M104 uses parameters (for example, FIGS. 7 and 8 (FIG. 7 and FIG. The domain width RNDW of the random value RND in the embodiment of B) and the matrices 136A to 136F in FIGS. 11 and 12 may be changed. At this time, the corrected data generation unit M104 changes the parameter according to the position in the transport direction Dx at the time of dot formation, similarly to changing the parameter according to the position Py in the first direction Dy.

(3) In each of the above embodiments, parameters used in the process for determining the dot formation state (for example, the definition of the amplitude coefficient data 134a in FIG. 8A and the random value RND in FIGS. 7 and 8B). The band width RNDW or the matrices 136A to 136F in FIGS. 11 and 12 may be prepared for each type of sheet (print medium). The sheet type may be selected from general types such as “glossy paper” and “matte paper”, and may be specified by the model number of the sheet. The corrected data generation unit M104 uses parameters associated with the sheet type. In this way, the corrected data generation unit M104 can perform correction suitable for the sheet type.

  A server (not shown) may store a plurality of types of parameters for a plurality of types of sheets in a memory (for example, a non-volatile memory). A correction data acquisition unit (not shown) is provided in the print control apparatus, and the correction data acquisition unit acquires parameters associated with the type of sheet specified by the user from the server via the network. May be.

(4) The configuration of the print execution unit is not limited to the configuration of the print execution unit 200 of each of the above embodiments, and various configurations can be employed. For example, the ink that can be used by the print execution unit is not limited to four types of CMYK inks, and one or more various inks can be used. Further, the positional deviation of dots described with reference to FIG. 3 may occur not only when bidirectional printing is performed but also when unidirectional printing is performed. Therefore, the corrected image data generation process of each embodiment described above may be applied to a print execution unit that performs unidirectional printing. Further, the total number of dot formation states is not limited to 2 or 4, and various numbers of 2 or more can be adopted.

(5) In each of the above embodiments, the configuration of the sheet conveying unit 260 is not limited to the configuration illustrated in FIGS. 1 and 2, and various configurations can be employed. For example, the low support portion 265a may be omitted. The pressing portion 269 may be configured using various members, for example, may be configured using a hard resin member, or may be configured using an elastic body such as a leaf spring. Further, a driven roller facing the first roller 261 may be provided instead of the first portions 265a1 and 265b1 of the support portions 265a and 265b. Similarly, a driven roller facing the second roller 262 may be provided instead of the fifth portions 265a5 and 265b5.

(6) In each of the embodiments described above, the reference gaps GPs, GPsa, and GPsb can be specified using the print result. That is, printing is performed using image data representing a plurality of straight lines (straight lines extending along the transport direction Dx) having different positions Py in the first direction Dy. In the print area (position Py) where the gap is close to the reference gap, the positional deviation of the dots is small, so that a straight line is clearly printed. On the other hand, in the printing region (position Py) where the gap is far from the reference gap, the positional deviation of the dots is large, so that the straight line is blurred and printed. As described above, the gap at the position Py where the straight line is clearly printed is the reference gap. Further, the first type region and the second type region can be specified as follows. That is, the first type region is a region where the absolute value of the difference between the actual gap and the specified reference gap is larger than that of the second type region.

(7) In the above embodiments, the control device 100 and the print execution unit 200 may be realized as independent devices housed in different housings. In each of the above embodiments, a plurality of computers that can communicate with each other via a network share a part of the functions required for image processing for printing, and as a whole, the functions of image processing for printing are provided. May be provided. As described above, the print control apparatus (for example, the control apparatus 100) may be configured by a computer system including a plurality of computers (a technique using such a computer system is also referred to as cloud computing).

(8) In each of the above embodiments, a part of the configuration realized by hardware may be replaced with software, and conversely, part or all of the configuration realized by software is replaced with hardware. You may do it. For example, the function of the corrected data generation unit M104 in FIG. 1 may be realized by a dedicated hardware circuit having a logic circuit.

  In addition, when part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. “Computer-readable recording media” are not limited to portable recording media such as memory cards and CD-ROMs, but are connected to internal storage devices in computers such as various RAMs and ROMs, and computers such as hard disk drives. It also includes an external storage device.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

DESCRIPTION OF SYMBOLS 100 ... Control apparatus, 110 ... CPU, 120 ... Volatile memory, 130 ... Non-volatile memory, 132 ... Program, 134a ... Amplitude coefficient data (correction data), 136, 136A to 136F ... matrix, 170 ... operation unit, 180 ... display unit, 190 ... communication unit, 200 ... print execution unit, 210 ... control circuit, 212 ... movement control , 214 ... head drive unit, 216 ... transport control unit, 240 ... head moving unit, 242 ... moving motor, 244 ... support shaft, 250 ... print head, 250n .. . Nozzle, 260... Sheet conveying section, 261... First roller, 262. Second roller, 263... Conveying motor, 265. ... high support portion, 269 ... pressing portion, 300 ... sheet, 300f ... reference sheet, 300s ... reference surface, 300sa ... reference surface, 300s ... reference plane, 600 ... printing device, M100 ... printer driver, M104 ... corrected data generation unit, M106 ... corrected data supply unit, EB ... error buffer, np .. Nozzle surface, Dy ... first direction, Dx ... transport direction (second direction),

Claims (13)

A print head having a sheet conveying unit that conveys the sheet in a second direction intersecting the first direction and a plurality of nozzles that eject droplets in a state where the sheet is deformed in a wave shape along the first direction. A head moving unit that moves the print head in parallel with the first direction; and driving the print head while the print head is moving to discharge the droplets toward the wave-deformed sheet. A print control apparatus that causes a print execution unit including a print head drive unit to execute printing,
A corrected data generation unit that executes a process of generating corrected image data from input image data by executing a correction process;
A corrected data supply unit that supplies the corrected image data to the print execution unit;
With
The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. A plurality of first type printed partial images printed on a plurality of first type regions on the sheet and a plurality of second type printed partial images printed on a plurality of second type regions on the sheet. And processing for generating the corrected image data by executing the correction processing using the input image data so that the spectrum of the spatial frequency is different between,
The plurality of first type regions and the plurality of second type regions are regions extending along the second direction, and the first type regions and the second type regions are along the first direction. are arranged alternately Te,
The corrected image data is determined for each print pixel, which is determined from a non-dot state in which dots are not formed and a plurality of dot states in which dots are formed and different in density from each other. Represents the dot formation state,
The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. The input image so that the ratio of the printed pixels having the highest density is different between the plurality of first type printed partial images and the plurality of second type printed partial images. Including a process of determining the dot formation state for each print pixel by executing the correction process using data,
Print control device. A print head having a sheet conveying unit that conveys the sheet in a second direction intersecting the first direction and a plurality of nozzles that eject droplets in a state where the sheet is deformed in a wave shape along the first direction. A head moving unit that moves the print head in parallel with the first direction; and driving the print head while the print head is moving to discharge the droplets toward the wave-deformed sheet. A print control apparatus that causes a print execution unit including a print head drive unit to execute printing,
A corrected data generation unit that executes a process of generating corrected image data from input image data by executing a correction process;
A corrected data supply unit that supplies the corrected image data to the print execution unit;
With
The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. A plurality of first type printed partial images printed on a plurality of first type regions on the sheet and a plurality of second type printed partial images printed on a plurality of second type regions on the sheet. And processing for generating the corrected image data by executing the correction processing using the input image data so that the spectrum of the spatial frequency is different between,
The plurality of first type regions and the plurality of second type regions are regions extending along the second direction, and the first type regions and the second type regions are along the first direction. are arranged alternately Te,
The corrected image data represents a dot formation state for each print pixel, determined from a dot non-state in which dots are not formed and a dot presence state in which dots are formed.
Print control device. The print control apparatus according to claim 1 or 2 ,
The first type region is a region where a gap between the sheet and the nozzle is outside a specific range,
The second type area is a print control apparatus in which the gap is an area within the specific range. The print control apparatus according to claim 3 ,
The specific control range is a print control apparatus in which the gap is a range less than a specific threshold value. The print control apparatus according to any one of claims 1 to 4 ,
The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. The correction processing using the input image data is performed so that the plurality of second type printed partial images are rougher than the plurality of first type printed partial images. A print control apparatus including processing for generating corrected image data. The print control apparatus according to any one of claims 1 to 5 ,
The input image data represents each color of a plurality of print pixels as an ink color gradation value that is a gradation value of a color component of the droplet,
The corrected image data represents a dot formation state for each print pixel,
The corrected data generation unit, in the process of generating the corrected image data, a gradation value of the target pixel, an error value obtained in peripheral pixels located around the target pixel, and a random value And determining the dot formation state of the pixel of interest and the error value of the pixel of interest according to the dot formation state of the pixel of interest,
The possible range of the random number value is a print control apparatus that changes according to the position of the target pixel in the first direction as a parameter of the correction process. The print control apparatus according to any one of claims 1 to 5 ,
The corrected image data represents a dot formation state for each print pixel,
The corrected data generation unit, in the process of generating the corrected image data, according to an error diffusion method using a correction parameter that changes according to the position of the print pixel in the first direction, A printing control apparatus that determines a dot formation state for each. The printing control apparatus according to claim 7 ,
In the process of generating the corrected image data, the corrected data generation unit uses a gradation value of a target pixel, an error value obtained in a peripheral pixel located around the target pixel, and a correction parameter. And determining the dot formation state of the pixel of interest and the error value of the pixel of interest according to the dot formation state of the pixel of interest using a random number value determined accordingly,
The possible range of the random number value is a print control apparatus that changes as the correction parameter according to the position of the target pixel in the first direction. The printing control apparatus according to claim 7 ,
In the process of generating the corrected image data, the corrected data generation unit adds a gradation value of a target pixel, an error value obtained in peripheral pixels located around the target pixel, and the error value. And a weight determined for each relative position of the peripheral pixel with respect to the target pixel, and according to the dot formation state of the target pixel and the dot formation state of the target pixel And determining an error value of the target pixel,
The weight is a printing control apparatus that changes according to a position of the target pixel in the first direction as the correction parameter. The print control apparatus according to any one of claims 1 to 9 ,
The print execution unit;
A printing apparatus comprising: The printing apparatus according to claim 10 ,
The sheet conveying unit is
A plurality of support portions arranged side by side along the first direction at positions facing the print head moving in parallel with the first direction, and supporting the sheet from the lower surface of the sheet;
A plurality of pressing portions that press the sheet downward from the upper surface of the sheet, wherein the positions of the pressing portions in the first direction are adjacent to each other among the plurality of supporting portions. A plurality of pressing portions disposed between the portions;
A printing apparatus comprising:   A print head having a sheet conveying unit that conveys the sheet in a second direction intersecting the first direction and a plurality of nozzles that eject droplets in a state where the sheet is deformed in a wave shape along the first direction. A head moving unit that moves the print head in parallel with the first direction; and driving the print head while the print head is moving to discharge the droplets toward the wave-deformed sheet. A computer program for causing a print execution unit including a print head drive unit to execute printing,
  A corrected data generation function for executing processing for generating corrected image data from input image data by executing correction processing;
  A corrected data supply function for supplying the corrected image data to the print execution unit;
  Is realized on a computer,
  The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. A plurality of first type printed partial images printed on a plurality of first type regions on the sheet and a plurality of second type printed partial images printed on a plurality of second type regions on the sheet. And processing for generating the corrected image data by executing the correction processing using the input image data so that the spectrum of the spatial frequency is different between,
  The plurality of first type regions and the plurality of second type regions are regions extending along the second direction, and the first type regions and the second type regions are along the first direction. Are lined up alternately,
  The corrected image data is determined for each print pixel, which is determined from a non-dot state in which dots are not formed and a plurality of dot states in which dots are formed and different in density from each other Represents the dot formation state,
  The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. The input image so that the ratio of the printed pixels having the highest density is different between the plurality of first type printed partial images and the plurality of second type printed partial images. Including a process of determining the dot formation state for each print pixel by executing the correction process using data,
  Computer program.   A print head having a sheet conveying unit that conveys the sheet in a second direction intersecting the first direction and a plurality of nozzles that eject droplets in a state where the sheet is deformed in a wave shape along the first direction. A head moving unit that moves the print head in parallel with the first direction; and driving the print head while the print head is moving to discharge the droplets toward the wave-deformed sheet. A computer program for causing a print execution unit including a print head drive unit to execute printing,
  A corrected data generation function for executing processing for generating corrected image data from input image data by executing correction processing;
  A corrected data supply function for supplying the corrected image data to the print execution unit;
  Is realized on a computer,
  The processing for generating the corrected image data is performed when the input image data represents an image having a uniform gradation value and the sheet is conveyed in a flat state without being deformed during printing. A plurality of first type printed partial images printed on a plurality of first type regions on the sheet and a plurality of second type printed partial images printed on a plurality of second type regions on the sheet. And processing for generating the corrected image data by executing the correction processing using the input image data so that the spectrum of the spatial frequency is different between,
  The plurality of first type regions and the plurality of second type regions are regions extending along the second direction, and the first type regions and the second type regions are along the first direction. Are lined up alternately,
  The corrected image data represents a dot formation state for each print pixel, determined from a dot non-state in which dots are not formed and a dot presence state in which dots are formed.
  Computer program.

Images