JP2019147331A - Image processing device and image processing method - Google Patents

Abstract

To provide an image processing device suppressing banding and improving printing quality.SOLUTION: An image processing device 110 generates printing data for a printer 100 printing color ink as first ink and clear ink as second ink disposed on the color ink onto a medium S by repeating main scanning and sub-scanning from image data. The image processing device 110 comprises: an image acquisition part acquiring the image data; a halftone processing part performing halftone processing on the basis of the image data; and a printing data generation part generating printing data on the basis of the image data subjected to the halftone processing. The halftone processing part performs the halftone processing with grid arrangement in which a length of a dither mask grid 82 for the clear ink in a sub-scanning direction is longer than a length of a dither mask grid 72 for the color ink in the sub-scanning direction.SELECTED DRAWING: Figure 13

Description

  The present invention relates to an image processing apparatus and an image processing method.

  2. Description of the Related Art Conventionally, an ink jet printing apparatus that prints an image or the like by ejecting droplets toward a medium such as paper or film has been known. In such a printing apparatus, an image processing apparatus that processes image data such as a photograph to generate print data is provided. In order to protect the surface of an image printed with color ink or to improve the black density, There are some which overcoat an image formed with color ink with clear ink. For example, Patent Document 1 discloses a first operation in which a carriage is moved in a first direction to form a color image on a medium, a second operation in which the carriage and the medium are relatively moved in a second direction, and a first operation. A printing apparatus that performs a third operation of ejecting clear ink on a formed color image is disclosed.

JP 2012-121197 A

  Printing devices are required to improve printing speed. Therefore, a method is used in which the number of nozzles ejecting color ink is made larger than the number of nozzles ejecting clear ink to improve the printing speed of color images. As a result, the number of nozzles that discharge clear ink is insufficient, and it becomes impossible to discharge clear ink to all pixels, so that periodic unevenness (banding) is easily visible in the sub-scanning direction, and printing is performed. Quality deteriorates. Therefore, an image processing apparatus that suppresses the occurrence of banding and improves print quality in printing based on the premise that clear ink is not discharged to all pixels has been desired.

  The image processing apparatus of the present application repeats main scanning and sub-scanning, and print data for a printing apparatus that prints the first ink and the second ink disposed on the first ink on the medium from the image data. An image processing apparatus for generating an image acquisition unit that acquires the image data, a halftone processing unit that performs halftone processing based on the image data, and the image data that has been subjected to the halftone processing A print data generation unit that generates the print data, wherein the halftone processing unit has a length of the dither mask grid for the second ink in the sub-scanning direction, and the first ink in the sub-scanning direction. The halftone process is performed with a grid arrangement longer than the length of the dither mask grid for use.

  The image processing apparatus of the present application repeats main scanning and sub-scanning, and print data for a printing apparatus that prints the first ink and the second ink disposed on the first ink on the medium from the image data. An image processing apparatus for generating an image acquisition unit that acquires the image data, a halftone processing unit that performs halftone processing based on the image data, and the image data that has been subjected to the halftone processing A print data generation unit that generates the print data, wherein the halftone processing unit is arranged so that a plurality of dither mask lattices are not continuous with each other in the sub-scanning direction with respect to the first ink. A halftone process is performed on two inks in an arrangement in which a plurality of dither mask lattices are not continuous with each other in the main scanning direction.

  In the above image processing apparatus, the plurality of mask groups constituting the dither mask grating for the second ink is an extension of the plurality of mask groups constituting the dither mask grating for the first ink in the sub-scanning direction. Preferably there is.

  In the image processing apparatus, it is preferable that the first ink is a color ink and the second ink is a clear ink or a light ink.

  Preferably, the image processing apparatus uses clear ink and light ink in combination as the second ink, and the halftone processing unit uses different dither masks for the clear ink and the light ink.

  According to the image processing method of the present application, print data for a printing apparatus that prints a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from image data. An image processing method to generate, an image acquisition step for acquiring the image data, a halftone processing step for performing a halftone process based on the image data, and a method based on the image data subjected to the halftone process A print data generation step for generating the print data, wherein the halftone processing step is such that the length of the dither mask grating for the second ink in the sub-scanning direction is equal to the first ink in the sub-scanning direction. The halftone process is performed with a grid arrangement longer than the length of the dither mask grid for use.

  According to the image processing method of the present application, print data for a printing apparatus that prints a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from image data. An image processing method to generate, an image acquisition step for acquiring the image data, a halftone processing step for performing a halftone process based on the image data, and a method based on the image data subjected to the halftone process A print data generation step for generating the print data, wherein the halftone processing step is an arrangement in which a plurality of dither mask lattices are not continuous with each other in the sub-scanning direction with respect to the first ink. A halftone process is performed on two inks in an arrangement in which a plurality of dither mask lattices are not continuous with each other in the main scanning direction.

1 is a perspective view illustrating a schematic configuration of a printing apparatus according to an embodiment. FIG. 2 is a cross-sectional view showing the overall configuration of the printing system. FIG. 2 is a block diagram schematically showing an electrical configuration for controlling the printing system. The figure explaining the image processing for printing an image. The figure explaining the arrangement | sequence of the nozzle which an ejection head has. The figure which simplifies and shows the nozzle row in FIG. FIG. 4 is a diagram for explaining a relative positional relationship between an ejection head and a medium in a sub scanning direction. The figure which shows the pixel position which can discharge an ink for every pass. The figure explaining a nozzle usage rate. The figure explaining the shading which appears by the difference in a nozzle usage rate. The figure which shows the discharge result of the clear ink by a prior art. The conceptual diagram explaining the dither mask by a prior art. The conceptual diagram explaining the dither mask by this invention. The figure which shows the discharge result of the clear ink by this invention. The flowchart figure explaining an image processing method. The conceptual diagram explaining the dither mask which concerns on the modification 1. FIG. FIG. 9 is a diagram illustrating a discharge result of clear ink according to a first modification. The flowchart figure explaining an image processing method. FIG. 10 is a diagram for explaining an arrangement of nozzles included in an ejection head according to Modification 2. FIG. 9 is a diagram showing pixel positions where ink can be ejected in pass 4;

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, for convenience of explanation, the X axis, the Y axis, and the Z axis are illustrated as three axes orthogonal to each other, the tip side of the arrow indicating the axial direction is “+ side”, and the base end side is “− Side”. The direction parallel to the X axis is referred to as “X axis direction”, the direction parallel to the Y axis is referred to as “Y axis direction”, and the direction parallel to the Z axis is referred to as “Z axis direction”.

(Embodiment)
FIG. 1 is a perspective view illustrating a schematic configuration of a printing apparatus according to an embodiment. FIG. 2 is a cross-sectional view showing the overall configuration of the printing system. FIG. 3 is a block diagram schematically showing an electrical configuration for controlling the printing system. First, a schematic configuration of the printing system 120 according to the present embodiment will be described with reference to FIGS. 1 to 3. In the present embodiment, the inkjet printing apparatus 100 that forms an image or the like on the medium S, and the image processing apparatus 110 that generates print data for the printing apparatus that causes the printing apparatus 100 to execute printing from the image data. The printing system 120 provided will be described as an example.

<Schematic configuration of image processing apparatus>
First, the configuration of the image processing apparatus 110 will be described.
As shown in FIGS. 2 and 3, the image processing apparatus 110 includes a printer control unit 111, an input unit 112, a display unit 113, a storage unit 114, and the like. As the image processing apparatus 110, a personal computer or the like can be used. The image processing apparatus 110 may be configured in the same casing as the printing apparatus 100.

  The printer control unit 111 controls the input unit 112 and the display unit 113 and controls a print job that causes the printing apparatus 100 to perform printing. The printer control unit 111 cooperates with the control unit 1 of the printing apparatus 100 to perform the printing system 120. Control the whole. Software that operates the image processing apparatus 110 includes general image processing application software (hereinafter referred to as an application) that handles image data to be printed, and printer driver software that generates print data for causing the printing apparatus 100 to execute printing. (Hereinafter referred to as the printer driver).

  The printer control unit 111 includes a central processing unit (CPU) 115, an application specific integrated circuit (ASIC) 116, a digital signal processor (DSP) 117, a memory 118, an interface unit (I / F) 119, and the like. Centralized management of the whole. The display unit 113 is configured by, for example, a liquid crystal display. The display unit 113 displays information input from the input unit 112, an image to be printed on the printing apparatus 100, and the like under the control of the printer control unit 111.

  The input unit 112 includes a port to which a keyboard and an information input device are connected, a touch panel provided on the surface of the display unit 113 (liquid crystal display), and the like. The input unit 112 also functions as an image acquisition unit that acquires image data. The display unit 113 displays various command options using a GUI (Graphical User Interface) button or the like, and various commands are input when the user selects a command using the input unit 112. The storage unit 114 is a rewritable storage medium such as a hard disk drive (HDD) or a memory card. The storage unit 114 stores software (a program operated by the printer control unit 111) that operates the image processing apparatus 110, images to be printed, and print jobs. Related information and the like are stored. The memory 118 is a storage medium that secures an area for storing a program for the CPU 115 to operate, a work area for the operation, and the like, and includes a storage element such as a RAM or an EEPROM.

<Schematic configuration of printing device>
Next, the configuration of the printing apparatus 100 will be described with reference to FIGS. 1 to 3. The printing apparatus 100 of the present embodiment is a roll-to-roll large format printer (LFP) that handles relatively large media.

  As shown in FIGS. 1 to 3, the printing apparatus 100 includes a transport roller pair 21 as a transport unit that transports the medium S in the transport direction, and a medium supply for supplying the medium S of the roll body R <b> 1 to the transport roller pair 21. Unit 14, a printing unit 58 that performs printing on the conveyed medium S, and a medium winding unit 15 that winds the printed medium in a roll shape. The printing unit 58 is provided in a substantially rectangular parallelepiped casing 51. Each of these parts is supported by a pair of legs 13 having wheels 12 attached to the lower end. In the present embodiment, the vertical direction along the direction of gravity is the Z axis, and the + Z axis side is “up”. The longitudinal direction (left-right direction) of the casing 51 that intersects the Z-axis direction is taken as the X-axis, and the + X-axis side is taken as “left”. Further, the direction (front-rear direction) intersecting both the Z-axis direction and the X-axis direction is defined as the Y-axis, and the + Y-axis side is defined as “front”. The positional relationship along the transport direction of the medium S is also referred to as “upstream side” and “downstream side”.

  The medium supply unit 14 is provided on the rear side (−Y axis direction) of the casing unit 51. The medium supply unit 14 holds a roll body R1 in which an unused medium S is wound in a cylindrical shape. Note that the medium supply unit 14 is loaded with a plurality of sizes of roll bodies R1 having different widths (lengths in the X-axis direction) and winding numbers of the medium S in an exchangeable manner. Moreover, regardless of the size of the roll body R1, the roll body R1 is loaded into the medium supply unit 14 in a state of being brought close to the end on the −X axis side. Then, the medium supply unit 14 loaded with the roll body R1 is rotated counterclockwise in FIG. 2, whereby the medium S is unwound from the roll body R1 and fed to the printing unit 58. In the present embodiment, an outer roll body R1 in which a printing surface to be printed on the medium S is wound outward is shown. In the printing apparatus 100, as the medium S, for example, a vinyl chloride film having a width of about 64 inches (Inch) is used.

  The medium winding unit 15 is provided on the front side (+ Y-axis direction) of the housing unit 51. A roll body R2 is formed on the medium winding unit 15 by winding the medium S printed by the printing unit 58 into a cylindrical shape. The medium winding unit 15 includes a pair of holders 17 that sandwich a core material for winding the medium S to form the roll body R2. One holder 17a is provided with a take-up motor (not shown) for supplying turning power to the core member. When the winding motor is driven to rotate the core material, the medium S is wound around the core material to form the roll body R2. The medium winding unit 15 is provided with a tension roller 16 that presses the back side of the medium S that hangs down by its own weight and applies tension to the medium S that is wound around the medium winding unit 15.

  In the printing apparatus 100 according to the present embodiment, the medium S can be discharged without being wound around the roll body R2. For example, the medium S after printing can be accommodated in a discharge basket (not shown) attached in place of the medium winding unit 15.

  The printing apparatus 100 includes an upstream guide unit 23, a platen 24, and a downstream guide unit 25 as medium guide units that guide the medium S conveyed by the conveyance roller pair 21 in the conveyance direction. The medium guide unit supports the medium S from below (the −Z axis side) in the conveyance path 22 of the medium S. The upstream guide unit 23 is provided on the rear side (−Y axis side) of the housing unit 51 and guides the medium S supplied from the medium supply unit 14 to the transport roller pair 21. The platen 24 is provided at a position facing the printing unit 58 and supports the medium S during printing. The downstream guide unit 25 is provided on the front side (+ Y axis side) of the housing unit 51 and guides the printed medium S from the platen 24 to the medium winding unit 15. The upstream side guide part 23, the platen 24, and the downstream side guide part 25 constitute a transport path 22 for the medium S.

  The printing apparatus 100 includes a first heater (preheater) 26 that heats the medium S, a second heater (platen heater) 27, and a third heater (afterheater) 28. The first heater 26 preheats the medium S supported by the upstream guide unit 23. The first heater 26 is disposed on the surface (the surface on the −Z axis side) opposite to the surface that supports the medium S in the upstream guide portion 23. The second heater 27 heats the medium S in an area where printing is performed on the medium S. The second heater 27 is disposed on the surface (surface on the −Z axis side) opposite to the surface that supports the medium S in the platen 24. The third heater 28 is configured to quickly dry and fix the ink on the medium S by heating the medium S, thereby preventing bleeding and blurring and improving the image quality. The third heater 28 is disposed on the surface (the surface on the −Z-axis side) opposite to the surface that supports the medium S in the downstream guide portion 25.

  The first, second, and third heaters 26, 27, and 28 are, for example, tube heaters, and are attached to the back surfaces of the upstream guide unit 23, the platen 24, and the downstream guide unit 25 via aluminum tape or the like. Has been. Then, by driving the first, second, and third heaters 26, 27, and 28, the surfaces supporting the medium S in the upstream guide portion 23, the platen 24, and the downstream guide portion 25 are heated by heat conduction, The medium S can be heated from the back side (−Z axis side) of the medium S. For example, the heating temperature of the first heater 26 is set to 40 ° C., and the heating temperature of the second heater 27 is set to 40 ° C. (target temperature). The heating temperature of the third heater 28 is set to 50 ° C., which is higher than that of the first heater 26 and the second heater 27.

  The first heater 26 is configured to promptly dry the ink S upon landing by gradually raising the temperature of the medium S from the normal temperature toward the target temperature (the temperature in the second heater 27). In addition, the second heater 27 is configured to cause the medium S to receive ink landing while maintaining the target temperature, and to promptly dry the ink from landing. Then, in the third heater 28, the temperature of the medium S is raised to a temperature higher than the target temperature, and the ink that has landed on the medium S is quickly dried, and is wound at least by the medium winding unit 15. Before taking the ink, the landed ink is completely dried and fixed on the medium S.

  The transport roller pair 21 extends in a direction crossing the transport direction of the medium S, and is provided between the platen 24 and the upstream guide portion 23. The transport roller pair 21 is disposed on the lower side of the transport path 22 and rotationally driven, and the transport drive roller 21a is disposed on the upper side of the transport drive roller 21a and rotates following the rotation of the transport drive roller 21a. And a roller 21b. The conveyance driven roller 21b is configured to be movable so as to be separated from or pressed against the conveyance driving roller 21a. In a state where the transport driving roller 21a and the transport driven roller 21b are in pressure contact, the transport roller pair 21 feeds the medium S to the printing unit 58 in the transport direction (+ Y-axis direction) while pinching (niping) the medium S. In the casing 51, a conveyance motor (not shown) is provided as a power source that outputs rotational power to the conveyance drive roller 21a. When the transport motor is driven and the transport drive roller 21a is rotationally driven, the medium S sandwiched between the transport driven roller 21b and the transport drive roller 21a is transported in the transport direction (+ Y-axis direction).

  An operation panel 62 is provided on the upper portion of the casing unit 51 in the −X axis direction. The operation panel 62 includes a display unit 64 that displays a print condition setting screen and the like, and an operation unit 63 that is operated when inputting print conditions and giving various instructions. An ink mounting portion 65 capable of mounting an ink storage container (ink cartridge) (not shown) that can store ink is provided at a lower portion in the −X axis direction of the housing portion 51. A plurality of ink cartridges are mounted on the ink mounting portion 65 corresponding to the type and color of ink. For example, cyan (C), magenta (M), yellow (Y), and black (K) color inks as ink types, and the surface of an image printed with the color ink are protected or the black density is improved. Clear ink (CL). Further, in the casing unit 51, a control unit 1 that controls the operation of the devices provided in each unit of the printing apparatus 100 is provided.

  A printing unit 58 is provided inside the housing unit 51. A supply port 18 for supplying the medium S to the printing unit 58 is formed on the back side (−Y-axis side) of the casing unit 51 at a position above the upstream guide unit 23. In addition, a discharge port 19 for discharging the medium S printed by the printing unit 58 is formed on the front side (+ Y axis side) of the casing unit 51 at a position above the downstream guide unit 25. Yes.

  The printing unit 58 is arranged above (+ Z axis side) with respect to the arrangement position of the platen 24 and is provided so as to be movable in the width direction of the medium S. The printing unit 58 includes a discharge head 52 that discharges ink to the medium S fed from the medium supply unit 14 and conveyed along the upstream guide unit 23 and the platen 24, a carriage 55 on which the discharge head 52 is mounted, A head moving unit 59 that moves the carriage 55 in the main scanning direction (X-axis direction) intersecting the transport direction is provided.

  The head moving unit 59 moves the carriage 55 (ejection head 52) in the main scanning direction. The carriage 55 is supported by guide rails 56 and 57 arranged along the X-axis direction, and is configured to be reciprocally movable in the ± X-axis direction by a head moving unit 59. As a mechanism of the head moving unit 59, for example, a mechanism in which a ball screw and a ball nut are combined, a linear guide mechanism, or the like can be employed. Further, the head moving unit 59 is provided with a motor (not shown) as a power source for moving the carriage 55 along the X-axis direction. When the motor is driven under the control of the control unit 1, the ejection head 52 reciprocates along the X-axis direction together with the carriage 55.

  At both ends of the guide rails 56 and 57 in the X-axis direction, there are adjustment mechanisms 53 that change the height (position in the Z-axis direction) of the ejection head 52 in order to adjust the separation distance between the ejection head 52 and the medium S. Is provided. In addition, a reflection type sensor 54 that detects the paper width (width in the X-axis direction) of the medium S is held below the carriage 55 at a position downstream of the ejection head 52 in the transport direction (+ Y-axis side). ing.

  The reflective sensor 54 is an optical sensor including a light source unit and a light receiving unit (not shown). The reflected light of the light emitted downward from the light source unit is received by the light receiving unit, and the reflected light received by the light receiving unit is received. A detection value (voltage value) corresponding to the strength is output to the control unit 1. Further, the reflection type sensor 54 detects the carriage 55 while moving the carriage 55 in the main scanning direction, and the control unit 1 detects the position where the reflection target changes based on the detection value, that is, the positions of both ends of the medium S in the X-axis direction. By detecting, the width of the medium S (length in the X-axis direction) is calculated. Then, according to the detected width of the medium S, printing is performed by the ejection head 52 ejecting the ink supplied from the ink container to the medium S conveyed along the conveyance path 22. The medium S after printing is guided obliquely downward along the downstream guide unit 25 and is taken up by the medium take-up unit 15.

As illustrated in FIG. 3, the printing apparatus 100 includes a control unit 1 that controls each unit included in the printing apparatus 100.
The control unit 1 includes a control circuit 4, an interface unit (I / F) 2, a CPU 3, a memory 5, and the like. The interface unit 2 is for transmitting and receiving data between the image processing apparatus 110 that handles input signals and images, and the control unit 1, and receives print data generated by the image processing apparatus 110. The CPU 3 is an arithmetic processing device for performing various input signal processing and controlling the entire printing apparatus 100.
The memory 5 is a storage medium for securing an area for storing a program of the CPU 3 and a work area, and has storage elements such as a RAM (Random Access Memory) and an EEPROM (Electrically Erasable Programmable Read Only Memory). .

  The control unit 1 controls the drive of the transport motor provided in the transport drive roller 21a by the control signal output from the control circuit 4 to move the medium S in the transport direction (+ Y-axis direction). The control unit 1 controls the drive of the motor provided in the head moving unit 59 by a control signal output from the control circuit 4 so that the carriage 55 on which the ejection head 52 is mounted is moved in the width direction of the medium S (X-axis direction). ). The control unit 1 controls the driving of the ejection head 52 by a control signal output from the control circuit 4 to eject ink toward the medium S. The control unit 1 controls each device (not shown).

  The control unit 1 controls the head moving unit 59 and the ejection head 52 to perform main scanning in which the carriage 55 (ejection head 52) is moved while ejecting ink from the ejection head 52. Lined raster lines are formed. By repeating this main scanning and sub-scanning in which the control unit 1 controls the transport driving roller 21a to transport the medium S in the transport direction, raster lines are aligned in the transport direction, and an image or the like is formed on the medium S. Is done.

  In the present embodiment, the configuration of the printing apparatus 100 that supplies the long medium S by the roll-to-roll method is shown, but the present invention is not limited to this. For example, the printing apparatus may be configured to supply a sheet of paper that has been cut to a predetermined length in a sheet type, and the medium S after printing is attached instead of the medium winding unit 15 (not shown). The structure accommodated in the discharge basket may be sufficient.

<Image processing>
FIG. 4 is a diagram for explaining image processing for printing an image. Next, print data generation processing will be described with reference to FIG. Printing on the medium S is started when print data is transmitted from the image processing apparatus 110 to the printing apparatus 100. The print data is generated by the printer driver.

  The printer driver receives image data (for example, text data or full-color image data) acquired by the input unit 112 from an application, converts the print data into a format that can be interpreted by the control unit 1 of the printing apparatus 100, and converts the print data. Output to the control unit 1. When converting image data from an application into print data, the printer driver performs resolution conversion processing, color conversion processing (ICC profile generation), halftone processing, rasterization processing, command addition processing, and the like. In other words, the printer driver is a function unit using software (or firmware), a halftone processing unit that performs halftone processing based on image data, and a print data generation unit that generates print data based on halftone processed image data (Not shown).

The resolution conversion process of step S1 is a process of converting the image data output from the application to a resolution (print resolution) when printing on the medium S. For example, when the print resolution is specified as 720 × 720 dpi, the vector format image data received from the application is converted into bitmap format image data with a resolution of 720 × 720 dpi. Each pixel data of the image data after the resolution conversion process is composed of pixels arranged in a matrix. Each pixel has a gradation value of, for example, 256 gradations in the RGB color space. That is, the pixel data after resolution conversion indicates the gradation value of the corresponding pixel.
Pixel data corresponding to one column of pixels arranged in a predetermined direction among pixels arranged in a matrix is called raster data. The predetermined direction in which the pixels corresponding to the raster data are arranged corresponds to the moving direction (main scanning direction) of the ejection head 52 when printing an image.

The color conversion process of step S2 is a process of converting from RGB color space to data in CMYK color space. A color management system is used as a system for performing this conversion. The color management system converts a color space using a profile (for example, an ICC (International Color Consortium) profile) that describes the correspondence between these color spaces. In the color space conversion, a dependent color space (RGB color space) depending on a specific device that handles image data is converted into a device independent color space (for example, CIELAB color space), and then the output side printing apparatus This is performed by converting into 100 color spaces (CMYK color space).
The CMYK colors are cyan (C), magenta (M), yellow (Y), and black (K), and the image data in the CMYK color system space is data corresponding to the ink color that the printing apparatus 100 has. . Therefore, for example, when the printing apparatus 100 uses four types of CMYK color inks, the printer driver generates image data in a CMYK color four-dimensional space based on the RGB data. This color conversion processing is performed based on a table (color conversion lookup table LUT) in which gradation values of RGB data and gradation values of CMYK color system data are associated with each other. Note that the pixel data after the color conversion processing is, for example, CMYK color system data of 256 gradations represented by the CMYK color system space.

The halftone process of step S3 is a process of converting the ink amount data having a high gradation number (256 gradations) into data having the gradation number that can be formed by the printing apparatus 100. Halftone processing is performed by a halftone processing unit. By this halftone process, the ink amount data indicating 256 gradations indicates 1 bit data indicating 2 gradations (with or without dots) or 4 gradations (without dots, small dots, medium dots, large dots). Converted to 2-bit data. Specifically, from the dot generation rate table corresponding to the gradation value (0 to 255) and the dot generation rate, the dot generation rate corresponding to the gradation value (for example, in the case of 4 gradations, no dot, small Pixel data is created so that dots are formed in a dispersed manner using the dither method, error diffusion method, etc. at the obtained generation rate. The
That is, pixel data after halftone processing is 1-bit or 2-bit data, and this pixel data is data indicating dot formation (the presence or absence of dots, the size of dots) in each pixel. For example, in the case of 2 bits (4 gradations), a dot gradation value [00] corresponding to no dot, a dot gradation value [01] corresponding to the formation of a small dot, and a dot gradation corresponding to the formation of a medium dot A value [10] and a dot gradation value [11] corresponding to the formation of a large dot are converted into four levels.

  The rasterization process in step S4 is a process of rearranging pixel data arranged in a matrix (for example, 2-bit data) according to the dot formation order at the time of printing. The rasterizing process includes a path allocating process in which image data composed of pixel data after halftone processing is allocated to each main scan that ejects droplets while the ejection head 52 reciprocates. When the pass assignment is completed, the actual nozzles forming each raster line constituting the print image are assigned.

The command addition process in step S5 is a process for adding command data corresponding to the printing method to the rasterized data. The command data includes, for example, transport data related to the transport specifications of the medium (the amount of movement in the transport direction, the speed, etc.). Rasterization processing and command addition processing are performed by the print data generation unit to generate print data.
The print data transmission process in step S6 is a process of transmitting the generated print data to the printing apparatus 100 via the interface unit 119.
The processing from step S1 to step S6 by the printer driver is performed by the ASIC 116 and the DSP 117 under the control of the CPU 115 (see FIG. 3).

<Configuration of head>
FIG. 5 is a diagram illustrating the arrangement of nozzles included in the ejection head. For convenience of explanation, FIG. 5 shows a nozzle arrangement of black ink (K), which is one kind of a plurality of color inks as the first ink, and clear ink (CL) as the second ink. Yes.
As shown in FIG. 5, the ejection head 52 includes nozzle rows of black ink (K) and clear ink (CL). Each nozzle row has a plurality of nozzles arranged in the sub-scanning direction. In FIG. 5, each nozzle row is composed of, for example, 16 nozzles, and nozzle numbers # 1 to # 16 are shown for each nozzle from the upstream side in the sub-scanning direction. Each nozzle has an odd nozzle row composed of nozzles with odd nozzle numbers and an even nozzle row composed of nozzles with even nozzle numbers. Each nozzle is provided at a nozzle pitch of 300 dpi (dots per inch) in the sub-scanning direction.

  The printing apparatus is required to improve the printing speed. In the printing apparatus 100 according to the present embodiment, the number of nozzles that eject color ink (black ink) is set to be larger than the number of nozzles that eject clear ink. Has improved printing speed. Specifically, black ink ejects ink from nozzles # 1 to # 12, and clear ink ejects ink from nozzles # 13 to # 16. In FIG. 5, nozzles that do not eject ink are indicated by black circles.

  FIG. 6 is a diagram showing the nozzle rows in FIG. 5 in a simplified manner. As shown in FIG. 6, the nozzle row of black ink (K) and the nozzle row of clear ink (CL) shown in FIG. 5 are the nozzles of nozzle numbers # 1 to # 12 that discharge black ink, and the clear ink. It can be regarded as an ejection head 52X having a single nozzle row that is a combination of nozzles # 13 to # 16 that eject (CL).

  FIG. 7 is a diagram illustrating the relative positional relationship between the ejection head and the medium S in the sub-scanning direction. The printing apparatus 100 according to the present embodiment repeats four times of main scanning (hereinafter also referred to as a pass) for moving in the main scanning direction while discharging ink from the discharge head 52X, and sub-scanning for feeding the medium S in the sub-scanning direction. Thus, a raster line in which dots are arranged in the main scanning direction is formed, and the black ink (K) and the clear ink arranged on the black ink (K) are printed on the medium S. Since the clear ink has an effect of improving the black density, the image quality can be improved by using the clear ink as the second ink.

  As shown in FIG. 7, after executing the first pass (pass 1), the control unit 1 transports the medium S in the sub-scanning direction by a distance corresponding to four nozzles, and passes the next pass (pass 2). Run. By repeating this until pass 4, a raster line in which dots are arranged in the main scanning direction is formed. In FIG. 7, for convenience of explanation, the ejection head 52 </ b> X is illustrated as moving relative to the medium S, but in reality, the medium S moves relative to the ejection head 52 </ b> X in the sub-scanning direction.

<Position where dots can be formed>
FIG. 8 is a diagram illustrating pixel positions where ink can be ejected for each pass. The left side of FIG. 8 shows the relative positions of the ejection head 52X and the medium S in each pass, and the right side of FIG. 8 shows the pixel positions where dots can be formed on the medium S in each pass. On the left side of the medium S in each pass, raster line numbers (for example, “L16”) corresponding to pixels arranged in the main scanning direction are shown. On the upper side of the medium S, the horizontal position corresponding to the pixels arranged in the sub-scanning direction is indicated by a number “1” or “2”.

  As shown in FIG. 8, raster lines with raster line numbers L13 to L16 are formed by four passes from pass 1 to pass 4. In the printing apparatus 100 of the present embodiment, in the main scan of pass 1 (odd number of passes), the nozzles with odd nozzle numbers can form dots at the pixel position of the horizontal position “1”, and even nozzles The numbered nozzle can form dots at the pixel position of the horizontal position “2”. In the main scan of pass 2 (even number of passes), the nozzles with odd nozzle numbers can form dots at the pixel position of the horizontal position “2”, and the nozzles with even nozzle numbers are in the horizontal position. A dot can be formed at the pixel position “1”. That is, each nozzle is configured to be able to eject ink to one of the horizontal pixel positions “1” or “2” in one pass.

  Attention is paid to raster line numbers L13 to L16 in which raster lines are formed in four passes. Raster line numbers L13 to L16 indicate that color ink (black) is applied to all pixels at horizontal positions “1” and “2” by at least one of the nozzles of nozzle numbers # 1 to # 12 in pass 1 to pass 3. Ink (K)) is ejected to form a color image. In the raster line numbers L13 to L16, the clear ink is ejected from the nozzles # 13 to # 16 in pass 4 to overcoat the color image. However, since the number of nozzles that eject clear ink is smaller than the number of nozzles that eject color ink, in each raster line, the clear ink is applied only at one of the horizontal positions “1” or “2”. A dot cannot be formed.

<Nozzle usage rate>
FIG. 9 is a diagram illustrating the nozzle usage rate. The nozzle usage rate of a certain nozzle being 50% means that 50% of pixels are actually ejected with respect to pixels that can be ejected by the nozzle. FIG. 10 is a diagram for explaining the shading that appears due to the difference in nozzle usage rate. FIG. 11 is a diagram illustrating a discharge result of the clear ink according to the conventional technique. In FIG. 11, the clear ink ejected on the white ink image is represented by black dots.

  The ejection head 52X is shown on the left side of FIG. 9, and the nozzle usage rate of each nozzle of the plurality of nozzles (nozzle number # 1 to nozzle number # 16) arranged in the sub-scanning direction is connected on the right side by moving average. An example of the shape is shown. This is called a mask pattern. This mask pattern is positioned at both ends of each of the nozzle that discharges the color ink and the nozzle that discharges the clear ink in order to alleviate streaks that are easily visible at both ends in the sub-scanning direction of the discharge head 52X in one pass. The nozzle usage rate increases linearly from the nozzle to the nozzle located in the center.

The amount of ink ejected from the nozzles changes as the nozzle usage rate changes. This occurs when the drive voltage for ejecting ink changes due to a change in the amount of ink used, and this is called the frequency characteristic of the ejection head 52. The amount of ink ejected from a nozzle having a high nozzle usage rate tends to be larger than the amount of ink ejected from a nozzle having a low nozzle usage rate.
FIG. 10 shows pixel positions of clear ink ejected by nozzles # 13 to # 16. A pixel 31 indicates a pixel position that can be ejected from a nozzle (nozzle number # 14, # 15) having a high nozzle usage rate. The pixel 32 indicates a pixel position that can be ejected from a nozzle (nozzle number # 13, # 16) having a low nozzle usage rate. For example, dots of clear ink with a large amount of ink are formed on raster line numbers L14 and L15, and dots of clear ink with a small amount of ink are formed on raster line numbers L16 and L17. As described above, printing giving priority to the printing speed is realized by reducing the number of passes for discharging the clear ink. As a result, clear ink cannot be formed on all the pixels, and a method of relaxing banding by forming one raster line with different nozzles cannot be used. It becomes easy to be visually recognized as unevenness (gloss banding). As shown in FIG. 11, in the printing according to the conventional technique, gloss banding generated at every pass cycle or four pass cycle is visually recognized.

  Since the dots of each ink are dispersed in a specific arrangement due to the dither mask used in the halftone process, the inventors of the present application have studied to improve the gloss banding by the above-described halftone process.

  FIG. 12 is a conceptual diagram illustrating a conventional dither mask. The halftone processing unit converts the ink amount data into dot data using the dither mask 70. The printing apparatus 100 prints an image on the medium S at a resolution of 1200 × 1200 dpi. FIG. 12 shows a 1200 × 1200 dpi resolution grid 71 for an image to be printed on the medium S. Also shown is a dither mask grid 72 that is arranged relative to the image.

  The size of the dither mask grid 72 is 1024 × 1024 pixels. Further, the dither mask grating 72 is composed of a plurality of similar mask groups 73. The size of the mask group 73 can be set to an arbitrary number of pixels. For example, on the dither mask grating 72, mask groups 73 are periodically arranged in the main scanning direction and the sub scanning direction in order from the upper left in FIG. Further, the entire image is covered with a periodically arranged dither mask grating 72. The halftone processing unit determines whether or not to form a dot by comparing the dot generation rate corresponding to the gradation value for each pixel of the image with the dither threshold value set for each pixel of the dither mask grid 72.

  As shown in FIG. 12, the dither mask gratings 72 of the dither mask 70 are arranged continuously in the main scanning direction and are not arranged in the sub scanning direction. That is, the dither mask gratings 72 arranged in the sub-scanning direction are arranged at positions that are sequentially shifted in the main scanning direction. In the prior art, the halftone processing unit performs halftone processing using the same dither mask 70 for both color ink and clear ink.

FIG. 13 is a conceptual diagram illustrating a dither mask according to the present invention. FIG. 14 is a diagram showing the discharge result of the clear ink according to the present invention. In FIG. 14, the clear ink ejected on the white ink image is represented by black dots.
The halftone processing unit performs halftone processing with a grid arrangement in which the length of the dither mask grid 82 for clear ink in the sub-scanning direction is longer than the length of the dither mask grid 72 for color ink in the sub-scanning direction. That is, the halftone processing unit performs the halftone process of the color ink using the dither mask 70, and performs the halftone process of the clear ink using the dither mask 80.

  As shown in FIG. 13, a plurality of mask groups 83 constituting a dither mask lattice 82 of a dither mask 80 used for clear ink are a plurality of mask groups constituting a dither mask lattice 72 of a dither mask 70 used for color ink. 73 is doubled in the sub-scanning direction. By using this mask group 83, a dither mask lattice 82 expanded to 2048 × 1024 pixels that is twice as long in the sub-scanning direction can be easily configured. As a result, the dither mask 80 has a long period in the sub-scanning direction, and the similar mask group 83 is also dispersed long in the sub-scanning direction, so that the gloss banding is hardly visually recognized as shown in FIG. In the present embodiment, the dither mask grating 82 expanded twice is shown, but a dither mask grating expanded twice or more may be used.

<Image processing method>
Next, an image processing method in the image processing apparatus will be described with reference to FIG. FIG. 15 is a flowchart for explaining the image processing method.

  Step S101 is an image acquisition step for acquiring image data. The printer control unit 111 acquires image data (RGB color space data) to be printed by the printing apparatus 100 and stores the acquired image data in the storage unit 114.

  Step S102 is a resolution conversion / color conversion process. The image data is converted into a resolution for printing in the resolution conversion process. Then, color conversion processing is performed on the image data for which the resolution conversion processing has been completed, and image data in the CMYK color space is obtained.

  Step S103 is a halftone processing step for performing halftone processing based on the image data. The halftone processing unit performs a halftone process for each ink type using a dither mask. In this embodiment, different dither masks are used for color ink and clear ink. Specifically, in the halftone processing step, halftone processing is performed with a dither mask 80 having a grid arrangement in which the length of the dither mask grid 82 for clear ink in the sub-scanning direction is longer than the dither mask grid 72 for color ink in the sub-scanning direction. Is done. Thereby, pixel data (image data) in which the dots of clear ink are dispersed in the sub-scanning direction than the color ink is created.

  Step S104 is a print data generation process for generating print data based on the halftone-processed image data. The print data generation unit performs rasterization processing on the halftone-processed image data, and finally performs command addition processing to generate print data.

  Step S105 is a print data transmission step. The generated print data is transmitted to the printing apparatus 100 via the interface unit 119.

  In the present embodiment, the second ink has been described as being a clear ink, but the second ink may be a light ink. As the light ink, light black (LK), very light black (LLK), or the like can be used. The same effect can be obtained by using light ink instead of clear ink.

As described above, according to the image processing apparatus 110 and the image processing method according to the present embodiment, the following effects can be obtained.
The printer driver of the image processing apparatus 110 is a function unit using software (or firmware), a halftone processing unit that performs halftone processing based on image data, and printing that generates print data based on the image data subjected to halftone processing. A data generation unit is provided. In the halftone processing unit, the length of the dither mask lattice 82 for clear ink as the second ink in the sub-scanning direction is longer than the length of the dither mask lattice 72 for color ink as the first ink in the sub-scanning direction. Halftone processing is performed in a lattice arrangement. Thereby, the dots of the clear ink that are periodically generated are dispersed in the sub-scanning direction in the sub-scanning direction, so that the glossy banding is difficult to be visually recognized. Therefore, it is possible to provide the image processing apparatus 110 that improves the print quality.

The plurality of mask groups 83 constituting the dither mask grating 82 are obtained by extending the plurality of mask groups 73 constituting the dither mask grating 72 in the sub-scanning direction. By using the mask group 83 extended in the sub-scanning direction, a dither mask grating 82 long in the sub-scanning direction can be easily configured.
The first ink is a color ink, and the second ink is a clear ink or a light ink. Since clear ink and light ink have the effect of improving black density, image quality can be improved by overcoating clear ink or light ink.

  The image processing method of the image processing apparatus 110 includes an image acquisition step of acquiring image data, a halftone processing step of performing halftone processing based on the image data, and print data based on the image data subjected to halftone processing. A print data generation step for generating the print data. In the halftone processing step, the length of the dither mask lattice 82 for clear ink as the second ink in the sub-scanning direction is longer than the length of the dither mask lattice 72 for color ink as the first ink in the sub-scanning direction. Halftone processing is performed with the arranged dither mask 80. Accordingly, since the dots of clear ink that are periodically generated are dispersed in the sub-scanning direction in the sub-scanning direction, the glossy banding is difficult to be visually recognized. Therefore, it is possible to provide an image processing method that improves print quality.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below. Moreover, about the same component as embodiment, the same number is used and the overlapping description is abbreviate | omitted.

(Modification 1)
FIG. 16 is a conceptual diagram illustrating a dither mask according to the first modification. FIG. 17 is a diagram illustrating a discharge result of the clear ink according to the first modification. In FIG. 17, the clear ink ejected on the white ink image is represented by black dots.
The halftone processing unit is arranged such that the plurality of dither mask lattices 72 are not continuous with each other in the sub-scanning direction with respect to the color ink as the first ink, and the plurality of dither masks with respect to the clear ink as the second ink. Halftone processing is performed in an arrangement in which the gratings 72 are not continuous with each other in the main scanning direction. Specifically, the halftone processing unit performs the halftone processing of the color ink using the dither mask 70 (see FIG. 12), and performs the halftone processing of the clear ink using the dither mask 90.

  As shown in FIG. 16, the dither mask gratings 72 of the dither mask 90 are arranged so as not to be continuous with each other in the main scanning direction, and are arranged to be continuous with each other in the sub scanning direction. That is, since the dither mask grating 72 arranged in the main scanning direction is arranged at a position sequentially shifted in the sub scanning direction, the dither mask 90 does not have the same mask group 73 arranged in the main scanning direction. Accordingly, the dot dispersion period of the clear ink in the main scanning direction is different from the dot dispersion period of the color ink and is shifted in the sub-scanning direction, so that the glossy banding is hardly visually recognized as shown in FIG.

  Next, an image processing method in Modification 1 will be described with reference to FIG. FIG. 18 is a flowchart for explaining the image processing method. Note that steps S201, S202, S204, and S205 of the present modification are the same as steps S101, S102, S104, and S105 described in the embodiment, and thus description thereof is omitted.

  Step S203 is a halftone processing step for performing halftone processing based on the image data. The halftone processing unit performs a halftone process for each ink type using a dither mask. In this modification, different dither masks are used for color ink and clear ink. Specifically, in the halftone processing step, halftone processing is performed with the dither mask 70 in which the plurality of dither mask lattices 72 are not continuous with each other in the sub-scanning direction with respect to the color ink, and the plurality of dither mask lattices are performed with respect to the clear ink. Halftone processing is performed with a dither mask 90 in which 72 is not arranged mutually in the main scanning direction. As a result, pixel data (image data) in which the dispersion period of the clear ink dots in the main scanning direction is different from the color ink dot dispersion period and shifted in the sub-scanning direction is created.

  In the present modification, the dither mask 90 has been described as having the dither mask grating 72 composed of the same plurality of mask groups 73 as in the prior art, but a mask group and dither mask different from the dither mask 70 are described. It may be a lattice.

(Modification 2)
FIG. 19 is a diagram illustrating the arrangement of nozzles included in the ejection head according to the second modification. In Modification 2, clear ink (CL) and light ink (LLK) are used in combination as the second ink. In FIG. 19, for convenience of explanation, black ink (K) which is one kind of a plurality of color inks as the first ink, clear ink (CL) and light ink (LLK) as the second ink, The nozzle arrangement is shown.

  As shown in FIG. 19, the ejection head 252 includes nozzle rows of black ink (K), clear ink (CL), and light ink (LLK). Each nozzle row has a plurality of nozzles arranged in the sub-scanning direction. In FIG. 19, each nozzle row is composed of, for example, 16 nozzles, and nozzle numbers # 1 to # 16 are shown from the upstream side in the sub-scanning direction for the black ink (K) and clear ink (CL) nozzles. For the light ink (LLK) nozzles, nozzle numbers # 1 ′ to # 16 ′ are shown from the upstream side in the sub-scanning direction. Each nozzle has an odd nozzle row composed of nozzles with odd nozzle numbers and an even nozzle row composed of nozzles with even nozzle numbers. Each nozzle is provided at a nozzle pitch of 300 dpi (dots per inch) in the sub-scanning direction.

  The position of the nozzle row of light ink (LLK) in the sub-scanning direction is arranged at a position shifted from the nozzle position of the nozzle row of clear ink (CL) by a distance corresponding to 1/2 of the nozzle pitch. . In other words, the clear ink (CL) and light ink (LLK) nozzles that overcoat the color ink (black ink (K)) are provided at a nozzle pitch of 600 dpi in the sub-scanning direction.

  FIG. 20 is a diagram illustrating pixel positions where ink can be ejected in pass 4. As in FIG. 8 described in the embodiment, the raster line numbers L13 to L16 are set in the horizontal positions “1” and “1” by at least one of the nozzles # 1 to # 12 in pass 1 to pass 3. Color ink (black ink (K)) is ejected to all the pixels 2 ”, and a color image is formed. In the raster line numbers L13 to L16, the clear ink is ejected from the nozzles # 13 to # 16 in pass 4 to overcoat the color image. At the same time, there are nozzles at the intermediate position between the raster line numbers L13 and L14, the intermediate position between the raster line numbers L14 and L15, the intermediate position between the raster line numbers L15 and L16, and the intermediate position between the raster line numbers L16 and L17. Light ink is ejected from nozzles # 13 'to # 16' to overcoat the color image.

  For pixels that cannot form dots as described in the embodiment, half of the pixel area is filled with light ink. For example, in a pixel at which the raster line number L14 and the horizontal position “1” intersect, in which dots cannot be formed, the downstream half in the sub-scanning direction has a nozzle number # 16 at an intermediate position between the raster line numbers L13 and L14. It is covered with light ink ejected from '. Thereby, the area which cannot overcoat a color image can be reduced.

  In the second modification, in the halftone processing of the image processing, the halftone processing unit uses different dither masks for clear ink (CL) and light ink (LLK). For example, the halftone processing unit performs the clear ink (CL) halftone process using the dither mask 80 described in the embodiment, and performs the light ink (LLK) halftone process in the first modification. To do. As a result, the clear ink (CL) dots and the light ink (LLK) dots are dispersed in an array with different periods, so that the glossy banding is hardly visually recognized.

  In the above-described embodiment, another device may have at least a part of the functions of the image processing device 110. In addition, the printing apparatus may have all the functions of the image processing apparatus 110. Even in such a configuration, the same effects as in the above embodiment can be obtained.

The contents derived from the embodiment will be described below.
The image processing apparatus of the present application repeats main scanning and sub-scanning, and print data for a printing apparatus that prints the first ink and the second ink disposed on the first ink on the medium from the image data. An image processing apparatus for generating an image acquisition unit that acquires the image data, a halftone processing unit that performs halftone processing based on the image data, and the image data that has been subjected to the halftone processing A print data generation unit that generates the print data, wherein the halftone processing unit has a length of the dither mask grid for the second ink in the sub-scanning direction, and the first ink in the sub-scanning direction. The halftone process is performed with a grid arrangement longer than the length of the dither mask grid for use.

  According to this configuration, the image processing apparatus includes the halftone processing unit that performs halftone processing based on the image data, the print data generation unit that generates print data based on the image data subjected to the halftone processing, and the like. . The halftone processing unit performs halftone processing with a grid arrangement in which the length of the dither mask grid for the second ink in the sub-scanning direction is longer than the length of the dither mask grid for the first ink in the sub-scanning direction. Accordingly, the dots of the second ink that are periodically generated in the sub-scanning direction are dispersed in the sub-scanning direction, so that banding is difficult to be visually recognized. Therefore, it is possible to provide an image processing apparatus that improves print quality.

  The image processing apparatus of the present application repeats main scanning and sub-scanning, and print data for a printing apparatus that prints the first ink and the second ink disposed on the first ink on the medium from the image data. An image processing apparatus for generating an image acquisition unit that acquires the image data, a halftone processing unit that performs halftone processing based on the image data, and the image data that has been subjected to the halftone processing A print data generation unit that generates the print data, wherein the halftone processing unit is arranged so that a plurality of dither mask lattices are not continuous with each other in the sub-scanning direction with respect to the first ink. A halftone process is performed on two inks in an arrangement in which a plurality of dither mask lattices are not continuous with each other in the main scanning direction.

  According to this configuration, the image processing apparatus includes the halftone processing unit that performs halftone processing based on the image data, the print data generation unit that generates print data based on the image data subjected to the halftone processing, and the like. . The halftone processing unit performs a halftone process on the first ink so that the plurality of dither mask lattices are not continuous with each other in the sub-scanning direction, and the plurality of dither mask lattices with respect to the second ink are mutually connected in the main scanning direction. Halftone processing is performed in a discontinuous arrangement. As a result, the dispersion period of the dots of the second ink in the main scanning direction is different from the dot dispersion period of the first ink, and image data shifted in the sub-scanning direction is created, so that it is difficult to visually recognize the banding. Therefore, it is possible to provide an image processing apparatus that improves print quality.

  In the image processing apparatus, the plurality of mask groups constituting the dither mask grating for the second ink is an extension of the plurality of mask groups constituting the dither mask grating for the first ink in the sub-scanning direction. Preferably there is.

  According to this configuration, the plurality of mask groups constituting the dither mask grating used for the second ink is an extension of the plurality of mask groups constituting the dither mask grating used for the first ink in the sub-scanning direction. . By using this mask group, a dither mask grating extended in the sub-scanning direction can be easily configured. As a result, the period of the dither mask grating becomes longer in the sub-scanning direction, and the mask group is also dispersed longer in the sub-scanning direction, so that banding is hardly visible.

  In the image processing apparatus, it is preferable that the first ink is a color ink and the second ink is a clear ink or a light ink.

  According to this configuration, since clear ink and light ink have an effect of improving color density, a color image is formed using color ink as the first ink, and clear-in or light ink is used as the second ink. Image quality can be improved by overcoating with color ink.

  Preferably, the image processing apparatus uses clear ink and light ink in combination as the second ink, and the halftone processing unit uses different dither masks for the clear ink and the light ink.

  According to this configuration, the halftone processing unit uses different dither masks for the clear ink and the light ink used as the second ink. As a result, the clear ink dots and the light ink dots are dispersed in an array with different periods, so that it is difficult to visually recognize the banding.

  According to the image processing method of the present application, print data for a printing apparatus that prints a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from image data. An image processing method to generate, an image acquisition step for acquiring the image data, a halftone processing step for performing a halftone process based on the image data, and a method based on the image data subjected to the halftone process A print data generation step for generating the print data, wherein the halftone processing step is such that the length of the dither mask grating for the second ink in the sub-scanning direction is equal to the first ink in the sub-scanning direction. The halftone process is performed with a grid arrangement longer than the length of the dither mask grid for use.

  According to this method, the image processing method includes an image acquisition step of acquiring image data, a halftone processing step of performing halftone processing based on the image data, and print data based on the image data subjected to halftone processing. And a print data generation step for generating. In the halftone processing step, halftone processing is performed with a grid arrangement in which the length of the dither mask grid for the second ink in the sub-scanning direction is longer than the length of the dither mask grid for the first ink in the sub-scanning direction. As a result, the dots of clear ink that are periodically generated in the sub-scanning direction are dispersed in the sub-scanning direction, so that banding is difficult to be visually recognized. Therefore, it is possible to provide an image processing method that improves print quality.

  According to the image processing method of the present application, print data for a printing apparatus that prints a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from image data. An image processing method to generate, an image acquisition step for acquiring the image data, a halftone processing step for performing a halftone process based on the image data, and a method based on the image data subjected to the halftone process A print data generation step for generating the print data, wherein the halftone processing step is an arrangement in which a plurality of dither mask lattices are not continuous with each other in the sub-scanning direction with respect to the first ink. A halftone process is performed on two inks in an arrangement in which a plurality of dither mask lattices are not continuous with each other in the main scanning direction.

  According to this method, the image processing method includes an image acquisition step of acquiring image data, a halftone processing step of performing halftone processing based on the image data, and print data based on the image data subjected to halftone processing. And a print data generation step for generating. In the halftone processing step, halftone processing is performed on the first ink so that the plurality of dither mask lattices are not continuous with each other in the sub-scanning direction, and the plurality of dither mask lattices are mutually connected with respect to the second ink in the main scanning direction. Halftone processing is performed in a discontinuous arrangement. As a result, the dispersion period of the dots of the second ink in the main scanning direction is different from the dot dispersion period of the first ink, and image data shifted in the sub-scanning direction is created, so that it is difficult to visually recognize the banding. Therefore, it is possible to provide an image processing method that improves print quality.

  DESCRIPTION OF SYMBOLS 1 ... Control part, 2,119 ... Interface part, 3,115 ... CPU, 4 ... Control circuit, 5,118 ... Memory, 14 ... Medium supply part, 15 ... Medium winding part, 21 ... Conveyance roller pair, 22 ... Transport path 31, 32 ... Pixel, 51 ... Housing part, 52, 52X, 252 ... Discharge head, 55 ... Carriage, 58 ... Printing part, 59 ... Head moving part, 62 ... Operation panel, 64, 113 ... Display part 65: Ink mounting portion, 70, 80, 90 ... Dither mask, 71 ... Resolution grid, 72, 82 ... Dither mask grid, 73, 83 ... Mask group, 100 ... Printing device, 110 ... Image processing device, 111 ... Printer Control unit, 112... Input unit, 114... Storage unit, 116.

Claims (7)

An image processing apparatus that generates print data for a printing apparatus that prints a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from the image data. And
An image acquisition unit for acquiring the image data;
A halftone processing unit for performing halftone processing based on the image data;
A print data generation unit that generates the print data based on the halftone processed image data,
The halftone processing unit has the lattice arrangement in which the length of the dither mask grating for the second ink in the sub scanning direction is longer than the length of the dither mask grating for the first ink in the sub scanning direction. Processing,
An image processing apparatus. An image processing apparatus that generates print data for a printing apparatus that prints a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from the image data. And
An image acquisition unit for acquiring the image data;
A halftone processing unit for performing halftone processing based on the image data;
A print data generation unit that generates the print data based on the halftone processed image data,
The halftone processing unit
With respect to the first ink, a plurality of dither mask lattices are arranged not to be continuous with each other in the sub-scanning direction,
Performing a halftone process on the second ink in an arrangement in which a plurality of dither mask lattices are not continuous with each other in the main scanning direction;
An image processing apparatus. The plurality of mask groups constituting the dither mask grating for the second ink are obtained by extending the plurality of mask groups constituting the dither mask grating for the first ink in the sub-scanning direction;
The image processing apparatus according to claim 1. The first ink is a color ink;
The second ink is a clear ink or a light ink;
The image processing apparatus according to any one of claims 1 to 3, wherein As the second ink, a clear ink and a light ink are used in combination,
The halftone processing unit is configured to make different dither masks to be used for the clear ink and the light ink;
The image processing apparatus according to any one of claims 1 to 3, wherein An image processing method for generating print data for a printing apparatus for printing a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from the image data. And
An image acquisition step of acquiring the image data;
A halftone processing step for performing halftone processing based on the image data;
A print data generation step of generating the print data based on the halftone processed image data,
In the halftone processing step, the halftone is arranged in a grid arrangement in which the length of the dither mask grid for the second ink in the sub-scanning direction is longer than the length of the dither mask grid for the first ink in the sub-scanning direction. Processing,
An image processing method characterized by the above. An image processing method for generating print data for a printing apparatus for printing a first ink and a second ink disposed on the first ink on a medium by repeating main scanning and sub-scanning from the image data. And
An image acquisition step of acquiring the image data;
A halftone processing step for performing halftone processing based on the image data;
A print data generation step of generating the print data based on the halftone processed image data,
The halftone processing step includes
With respect to the first ink, a plurality of dither mask lattices are arranged not to be continuous with each other in the sub-scanning direction,
Performing a halftone process on the second ink in an arrangement in which a plurality of dither mask lattices are not continuous with each other in the main scanning direction;
An image processing method characterized by the above.

Images