Control device, control method, and program

Abstract

This reduces the possibility of colors appearing differently between multiple band images that represent the same color. [Solution] Multiple band images forming a target image, arranged in the transport direction on a sheet, are printed by the printing unit through multiple pass processing. The first mode, which is a processing mode for printing a first specific band image to the printing unit through multiple pass processing, is a bidirectional printing processing mode. The multiple pass processing in the first mode includes a preceding partial pass processing that forms part of the multiple dots of a partial line group, and a succeeding partial pass processing that forms the remainder of the multiple dots of the partial line group without moving the sheet in the transport direction after the preceding partial pass processing. The succeeding partial pass processing moves the print head in the opposite direction to the direction of movement of the print head in the preceding partial pass processing.

Description

Technical Field

[0001] This specification relates to a technique for controlling a printing execution unit that ejects ink to print an image.

Background Art

[0002] Patent Document 1 discloses a printing method for performing partial overlay printing. In this printing, partial overlay printing is applied to the lower end side of the upper pattern and the upper end side of the lower pattern.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A printing execution unit that moves a print head in a moving direction intersecting the conveyance direction of a sheet such as paper can be used. Such a printing execution unit prints each of a plurality of band images arranged in the conveyance direction on the sheet by forming a plurality of dots during the movement of the print head. Here, the colors may appear different between a plurality of band images showing the same color.

[0005] This specification discloses a technique for reducing the possibility that the colors appear different between a plurality of band images showing the same color.

Means for Solving the Problems

[0006] The technique disclosed in this specification can be realized as the following application examples.

[0007] [Application Example 1] A control device for controlling a printing execution unit, wherein the printing execution unit comprises a print head having L nozzle groups for outputting L types (L is an integer of 2 or more) of ink, a transport device for transporting a sheet in the transport direction relative to the print head, and a move device for moving the print head in a move direction intersecting the transport direction relative to the sheet, wherein the L nozzle groups are arranged in the move direction, and the L nozzle groups include a plurality of nozzles whose positions in the transport direction are different from each other and which output ink to form dots on the sheet, and the control device is a band processing unit that causes the printing execution unit to print a plurality of band images which form a target image which is an image to be processed, and which are arranged in the transport direction on the sheet, by a plurality of pass processing, wherein the pass processing includes a process of forming a plurality of dots on a raster line extending in the move direction by driving the print head while the print head is moving, and the plurality of band images include a plurality of raster lines arranged in the transport direction with a resolution of N times (N is an integer of 2 or more) the resolution of the plurality of nozzles in the transport direction, The device includes a band processing unit, the band processing unit having a first mode which is a processing mode for printing a first specific band image included in the plurality of band images to the print execution unit by a plurality of pass processing steps, the first mode being a bidirectional printing processing mode which causes the print execution unit to perform a plurality of pass processing steps which represent the alternating execution of a first direction pass processing step which is a pass processing step which moves the print head in a first direction parallel to the direction of movement, and a second direction pass processing step which is a pass processing step which moves the print head in a second direction opposite to the first direction, the plurality of pass processing steps in the first mode including a preceding partial pass processing step which is a first direction pass processing step or a second direction pass processing step which forms a portion of a plurality of dots in a partial line group which is a group of a plurality of raster lines representing a portion of the first specific band image, and a succeeding partial pass processing step which is a pass processing step which, after the preceding partial pass processing step, forms the remainder of the plurality of dots in the partial line group without moving the sheet in the transport direction, the succeeding partial pass processing step which moves the print head in a direction opposite to the direction of movement of the print head in the preceding partial pass processing stepControl device.

[0008] In this configuration, a sub-line group representing a portion of a first specific band image is dotted by both a preceding sub-pass and a succeeding sub-pass in the opposite direction to the preceding sub-pass. This reduces the likelihood that the printed sub-line group's apparent color will be biased towards the color it would appear if all dots were formed by the first direction pass. It also reduces the likelihood that the printed sub-line group's apparent color will be biased towards the color it would appear if all dots were formed by the second direction pass. Therefore, the first specific band image containing the sub-line group can be made less likely to appear color-different from other band images exhibiting the same color.

[0009] Furthermore, the technologies disclosed herein can be implemented in various forms, for example, as a control method and control device for a printing execution unit, a printing apparatus equipped with a printing execution unit and a control device, a computer program for realizing the functions of such a method or apparatus, a recording medium (e.g., a non-temporary recording medium) on which the computer program is recorded, and so on. [Brief explanation of the drawing]

[0010] [Figure 1] This is an explanatory diagram of a multifunction printer 200, which is an example of a printing device. [Figure 2] This is a schematic diagram of the printing execution unit 400. [Figure 3] This is a perspective view showing the configuration of head 410. [Figure 4] This is an explanatory diagram of the printing process. [Figure 5] This is a flowchart illustrating an example of image processing for printing. [Figure 6] This is a flowchart illustrating an example of color banding mode processing. [Figure 7] Figures (A)-(D) illustrate examples of processing the band image of interest. [Figure 8] This diagram shows the path processing and the position of the nozzle NZ in the transport direction Dy. [Figure 9] This diagram shows the path processing and the position of the nozzle NZ in the transport direction Dy. [Figure 10] This diagram shows the path processing and the position of the nozzle NZ in the transport direction Dy. [Figure 11] This diagram shows the path processing and the position of the nozzle NZ in the transport direction Dy. [Figure 12] This is a flowchart illustrating a second embodiment of image processing. [Figure 13] This is a flowchart illustrating an example of color banding mode processing. [Figure 14] This is a flowchart illustrating a third embodiment of image processing. [Figure 15] This is an example of a settings screen. [Modes for carrying out the invention]

[0011] A. First example: Figure 1 is an explanatory diagram of a multifunction printer 200, which is an embodiment of a printing device. The multifunction printer 200 includes a control device 299, a scanner unit 280, and a print execution unit 400. The control device 299 includes a processor 210, a storage device 215, a display unit 240, an operation unit 250, and a communication interface 270. These elements are connected to each other via a bus. The storage device 215 includes a volatile storage device 220 and a non-volatile storage device 230.

[0012] The processor 210 is a device configured to perform data processing, for example, a Central Processing Unit (CPU) or a System on a chip (SoC). The volatile memory device 220 is, for example, a Dynamic Random Access Memory (DRAM), and the non-volatile memory device 230 is, for example, a flash memory. The non-volatile memory device 230 stores the data of each of the program 232 and the color evaluation information DB. In this embodiment, the program 232 and the color evaluation information DB are pre-stored in the non-volatile memory device 230 as firmware by the manufacturer of the multifunction machine 200.

[0013] The display unit 240 is a device configured to display an image, such as a liquid crystal display or an organic EL display. The operation unit 250 is a device configured to receive operations by a user, such as buttons, levers, or a touch panel arranged on top of the display unit 240. The display unit 240 and the operation unit 250 may form a so-called touch screen. The user can input various requests and instructions to the multifunction machine 200 by operating the operation unit 250. The display unit 240 may display operation elements (for example, buttons, sliders, etc.), and the displayed elements may be operated through the operation of the operation unit 250. The communication interface 270 is an interface for communicating with other devices (for example, including one or more of a USB interface, a wired LAN interface, and a wireless interface of IEEE802.11).

[0014] The scanner unit 280 is a reading device configured to optically read an object such as a document using a photoelectric conversion element such as a CCD or a CMOS. The scanner unit 280 generates reading data representing the read image (referred to as a "read image") (for example, RGB bitmap data).

[0015] The printing execution unit 400 is a device that prints an image on a sheet (an example of a printing medium). In this embodiment, the printing execution unit 400 includes a print head 410 (also simply referred to as the head 410), a head drive unit 420, a conveyance device 430, a moving device 440, an ink supply unit 450, and a control circuit 490 that controls these elements 410, 420, 430, 440, 450. In this embodiment, the printing execution unit 400 is an inkjet printing device that uses cyan C, magenta M, yellow Y, and black K inks respectively. The control circuit 490 is an electric circuit configured to control motors and the like, which will be described later. The control circuit 490 may be configured using, for example, a computer or dedicated hardware (such as an Application Specific Integrated Circuit (ASIC)).

[0016] The control device 299 is configured to generate print data using the image data and cause the printing execution unit 400 to print an image using the generated print data. The control device 299 can use the read data or the image data stored in an external storage device (for example, a memory card connected to the communication interface 270) to generate the print data. Also, the control device 299 can cause the printing execution unit 400 to print an image using the print data supplied by another external device connected to the multifunction device 200.

[0017] Figure 2 is a schematic diagram of the printing execution unit 400. The moving device 440 moves the head 410 in a bidirectional manner parallel to the direction Dx. Hereinafter, the bidirectional direction parallel to the direction Dx is referred to as the moving direction DxM. The moving direction DxM indicates the direction Dx and the direction opposite to the direction Dx. Here, the direction Dx is also referred to as the +Dx direction, and the direction opposite to the direction Dx is also referred to as the -Dx direction. Also, the +Dx direction is also referred to as the forward direction F, and the -Dx direction is also referred to as the reverse direction R. For other directions as well, similarly, the positive sign and the negative sign before the sign represent the same direction and the opposite direction.

[0018] In this embodiment, the moving device 440 comprises a carriage 443, a sliding shaft 444, a belt 445, and a plurality of pulleys 446, 447. The carriage 443 mounts the head 410. The sliding shaft 444 extends in the direction of movement DxM. The sliding shaft 444 supports the carriage 443 so that it can move in the direction of movement DxM. The belt 445 is wrapped around the pulleys 446, 447, and a portion of it is fixed to the carriage 443. The pulley 446 is rotated by the power of a motor (not shown, called the head motor). When the head motor rotates the pulley 446, the carriage 443 moves along the sliding shaft 444. As a result, the head 410 moves in the direction of movement DxM relative to the paper PM. Hereinafter, the process of moving the head 410 in the direction of movement DxM will also be called the moving process.

[0019] The transport device 430 transports the paper PM to the head 410 in direction Dy while holding the paper PM. Hereinafter, the Dy direction will also be referred to as the transport direction Dy. The aforementioned direction Dx (and therefore the movement direction DxM) is a direction that intersects the transport direction Dy. In this embodiment, the transport direction Dy is perpendicular to direction Dx.

[0020] In this embodiment, the transport device 430 includes a platen PT configured to support the paper PM, a first roller 431 and a second roller 432 configured to hold the paper PM placed on the platen PT, and a motor (not shown) for driving the rollers 431 and 432. The platen PT is positioned opposite the ink ejection surface of the head 410. Direction Dz in the figure is the direction from the platen PT toward the head 410. In this embodiment, direction Dz is perpendicular to directions Dx and Dy.

[0021] The first roller 431 is positioned in the -Dy direction relative to the head 410, and the second roller 432 is positioned in the +Dy direction relative to the head 410. Paper PM is supplied to the transport device 430 from a paper tray (not shown) by a paper feed roller (not shown). The paper PM supplied to the transport device 430 is sandwiched between the first roller 431 and a driven roller (not shown) paired with the first roller 431, and is transported in the transport direction Dy by these rollers. The transported paper PM is then sandwiched between the second roller 432 and a driven roller (not shown) paired with the second roller 432, and is transported in the transport direction Dy by these rollers. The transport device 430 transports the paper PM in the transport direction Dy by driving these rollers 431 and 432 with the power of a motor (referred to as a transport motor). Hereinafter, the process of moving the paper PM in the transport direction Dy will be referred to as the transport process.

[0022] The ink supply unit 450 supplies ink to the print head 410. The ink supply unit 450 comprises a cartridge mounting unit 451, a tube 452, and a buffer tank 453. The cartridge mounting unit 451 is detachably fitted with KYCM ink cartridges KC, YC, CC, and MC. The buffer tank 453 is attached to the carriage 443. The buffer tank 453 is located above the print head 410 and temporarily holds the CMYK inks to be supplied to the print head 410, ink by ink. The tube 452 is a flexible tube connecting the cartridge mounting unit 451 and the buffer tank 453. The ink in each ink cartridge KC, KC, YC, CC, and MC is supplied to the print head 410 via the cartridge mounting unit 451, the tube 452, and the buffer tank 453.

[0023] Figure 3 is a perspective view showing the configuration of the head 410 as seen in the -Dz direction. Unlike Figure 2, the transport direction Dy is upward in this figure. The nozzle forming surface 411, which is the -Dz direction side of the head 410, has nozzle groups NK, NY, NC, and NM that output the K, Y, C, and M inks described above. Each nozzle group contains Nznz nozzles NZ (where Nnz is an integer greater than or equal to 2). The positions in the transport direction Dy differ between the Nnz nozzles NZ of a single nozzle group. The positions in the Dx direction differ between the nozzle groups NK, NY, NC, and NM. In this embodiment, the nozzle groups NK, NY, NC, and NM are arranged in this order in the +Dx direction.

[0024] In this embodiment, the positions of multiple nozzles NZ in a single nozzle group are arranged at equal intervals with a nozzle pitch NP in the transport direction Dy. The nozzle pitch NP is the difference in the transport direction Dy position between two adjacent nozzles NZ in the transport direction Dy. Furthermore, in this embodiment, the positions of the nozzles NZ in the transport direction Dy are the same among the four nozzle groups NK, NY, NC, and NM.

[0025] In the figure, the nozzle resolution Rnz is the density of nozzles NZ in the transport direction Dy (unit: e.g., number of nozzles / inch). The nozzle resolution Rnz is associated with the nozzle pitch NP. The nozzle resolution Rnz may be, for example, 100 / inch or 300 / inch.

[0026] Each nozzle NZ is connected to a buffer tank 453 (Figure 2) via an ink channel (not shown) formed inside the head 410. Each ink channel is provided with an actuator (not shown; e.g., a piezoelectric element, heater, etc.) for ejecting ink.

[0027] The head drive unit 420 (Figure 1) includes an electrical circuit that drives each actuator within the head 410 while the head 410 is being moved by the moving device 440. The actuators eject ink from the nozzle NZ toward the paper PM (Figure 1) (i.e., ink is output from the nozzle NZ). This forms dots on the paper PM.

[0028] A2. Printing Overview: Figure 4 is an explanatory diagram illustrating the overview of printing by the printing execution unit 400. The figure shows the paper PM and the target image OI, which is the image to be printed on the paper PM. The target image OI is represented by multiple raster lines RL arranged in the transport direction Dy. The raster lines RL are lines that extend in the movement direction DxM. One nozzle NZ (Figure 3) can form a dot on one raster line RL by outputting ink while the head 410 is moving by the moving device 440 (Figure 2). In this embodiment, four nozzles of KYCM can form dots on one raster line RL. Hereinafter, the process of forming multiple dots on the raster line RL by driving the print head 410 while the print head 410 is moving will be called the dot formation pass process, or simply the pass process. One pass process can form multiple dots on multiple raster lines RL arranged in the transport direction Dy with a nozzle resolution Rnz (Figure 3).

[0029] Multiple raster lines RL are arranged at equal intervals in the transport direction Dy. The line resolution Rrl in the figure is the density of raster lines RL in the transport direction Dy (unit is, for example, lines / inch). In this embodiment, the line resolution Rrl is N times the nozzle resolution Rnz (Figure 3) (N is an integer of 2 or more). The resolution ratio N may be various values. Hereafter, we will assume N=3. If the nozzle resolution Rnz is 100 / inch, the line resolution Rrl is 300 / inch. If the nozzle resolution Rnz is 300 / inch, the line resolution Rrl is 900 / inch.

[0030] The resolution of the dots in the movement direction DxM may be set independently of the line resolution Rrl in the transport direction Dy (i.e., the resolution of the dots in the transport direction Dy). The resolution of the dots in the movement direction DxM may be, for example, 600 dpi or 1200 dpi (dpi = dots per inch).

[0031] The target image OI contains multiple band images BI1-BIn arranged in the -Dy direction from the +Dy edge of the target image OI. As will be described later, in this embodiment, the control device 299 selects a processing mode for each band image to cause the print execution unit 400 to print the band image. In this embodiment, the shape of each band image BI1-BIn is rectangular, extending in the movement direction DxM. The size in the transport direction Dy is the same among multiple band images BI1-BIn. Each band image BI1-BIn contains multiple raster lines RL. The number Nrl in the figure indicates the total number of raster lines RL contained in one band image. In the example in Figure 4, two adjacent band images are arranged in the transport direction Dy without overlapping and without gaps.

[0032] As described above, in this embodiment, the line resolution Rrl is N times the nozzle resolution Rnz. In this case, the total number of raster lines RL contained in one band image, Nrl, may be a multiple of N. In this embodiment, one pass processing is capable of forming dots in the regions of N consecutive band images. In this case, the total number of nozzles NZ contained in one nozzle group, Nnz (Figure 3), may be the same as the total number of raster lines RL contained in N band images (N*Nrl / N=Nrl) (i.e., Nnz=Nrl). The head 410 arranged in Figure 4 can form dots in the regions of three band images BI2-BI4 in one pass processing. Also, one pass processing can form dots on Nrl / N raster lines RL out of Nrl raster lines RL in one band image. That is, multiple dots on Nrl raster lines RL in one band image are formed by N or more pass processing. The method of printing multiple raster lines RL that are continuous in the transport direction Dy through multiple pass processing is also called interlaced printing.

[0033] Two types of pass processing are possible: one that moves the head 410 in the +Dx direction (forward direction F), and another that moves the head 410 in the -Dx direction (reverse direction R). Hereafter, the pass processing in the forward direction F will be called the forward pass processing, and the pass processing in the reverse direction R will be called the reverse pass processing. Printing that alternates between forward and reverse pass processing is also called bidirectional printing. Bidirectional printing can print images at a faster speed compared to cases where dots are formed by only one of the forward or reverse pass processing methods.

[0034] Multiple band images BI1-BIn are printed sequentially from band image BI1 at the +Dy edge of the target image OI toward the -Dy direction. When bidirectional printing is performed, the apparent color difference between multiple band images showing the same color can be significant, as described below. Multiple band images showing the same color indicates that the respective colors of the multiple band images shown by the data of the target image are the same. The stacking order of multiple types of ink differs between forward pass processing and reverse pass processing. In the embodiment of Figure 3, the stacking order of ink by forward pass processing is MCYK, and the stacking order of ink by reverse pass processing is KYCM. If the stacking order of ink differs between two parts of the printed image that show the same color, an observer of the printed image may perceive that the two parts have different colors (i.e., the apparent colors may differ between the two parts). For example, the apparent color may differ between raster line RL where dots are formed by forward pass processing and raster line RL where dots are formed by reverse pass processing. When bidirectional printing is performed, the number of forward and reverse passes may differ between multiple band images. For example, band image BI2 (Figure 4) may be printed with two forward passes and one reverse pass, while the adjacent band image BI3 may be printed with one forward pass and two reverse passes. In this case, even if band images BI2 and BI3 show the same color, their apparent colors may differ. That is, an observer of the printed image may recognize band-like regions that show an inappropriate color. Such regions are also called banding. The magnitude of the apparent color difference due to the direction of pass processing may vary depending on the color being printed. As will be described later, the processor 210 causes the print execution unit 400 to print the band images in a processing mode suitable for band images so as to reduce the possibility of different colors appearing between multiple band images that show the same color.

[0035] A3. Image processing: Figure 5 is a flowchart illustrating an example of image processing for printing. The processor 210 of the control device 299 starts the processing shown in Figure 5 in response to a print instruction. The processor 210 executes the processing shown in Figure 5 according to program 232. In S110, the processor 210 acquires the print instruction and acquires the target image data according to the print instruction. The method for acquiring the print instruction may be any method. In this embodiment, the user inputs the print instruction by operating the operation unit 250 (Figure 1). The processor 210 may also acquire the print instruction from other devices connected to the multifunction printer 200 (e.g., a computer, smartphone, etc.).

[0036] A print instruction includes information that specifies image data (the specified image data is called input image data). The input image data may be various types of data, for example, image data already stored in the storage device 215 (for example, the non-volatile storage device 230). The processor 210 uses the input image data to obtain the target image data.

[0037] In this embodiment, bitmap data of the processing resolution is used as the data for the target image. The pixel value of each pixel in the target image data is represented by 256 gradations of R (red), G (green), and B (blue) color values ​​from 0 to 255. The processing resolution is set to the resolution for printing by the print execution unit 400 (unit: for example, ppi (pixels per inch)). The processing resolution represents the pixel density in the movement direction DxM (Figure 4) and the pixel density in the transport direction Dy. The processing resolution indicates a resolution suitable for the density of multiple dots formed by the print execution unit 400. For example, the processing resolution may be the same as the resolution representing the density of the dots.

[0038] The input image data may be vector data containing drawing commands for drawing an object. In this case, the processor 210 may generate the target image data by rendering (also called rasterizing) the vector data. If the input image data is bitmap data, the processor 210 may generate the target image data at the processing resolution by converting the bitmap data resolution.

[0039] In S120, the processor 210 performs color conversion processing on the target image data. The color conversion processing converts the color value of each pixel from the color value in the color space before conversion (in this embodiment, the RGB color space) to the color value in the printing color space, which is the color space for printing. The printing color space is a color space represented by the color components corresponding to the colorants used by the printing execution unit 400 (in this embodiment, the CMYK color space). The correspondence between the color values ​​in the color space before conversion and the color values ​​in the printing color space is predetermined. The processor 210 stores the color-converted target image data in the storage device 215 (for example, the volatile storage device 220).

[0040] In S130, the processor 210 performs color banding mode processing. In color banding mode processing, the processor 210 determines the configuration of the interlaced printing (specifically, the configuration of the pass processing and transport processing) so that the likelihood of banding being noticeable is reduced.

[0041] Figure 6 is a flowchart illustrating an example of color banding mode processing. In S210, the processor 210 selects an unprocessed band image from among multiple band images BI1-BIn contained in the target image OI (Figure 4) as the band image of interest. The processor 210 then obtains data for the band image of interest from the target image data and the color-converted target image data. The order in which the band images of interest are selected can vary. For example, the processor 210 may select the band images sequentially from the band image BI1 at the +Dy end of the target image OI toward the -Dy direction.

[0042] In S215, the processor 210 calculates the degree of banding for each block in the band image of interest. Figures 7(A)-7(D) illustrate examples of processing of the band image of interest. Figure 7(A) is a flowchart illustrating an example of the process for determining the degree of banding for one block. Figure 7(B) shows the i-th band image BI(i) and the (i+1)th band image BI(i+1) contained in the target image OI. In this embodiment, the band image is represented by a plurality of blocks BL arranged in a grid along the +Dx and +Dy directions. The size of the blocks BL and the arrangement of the plurality of blocks BL within the band image are predetermined.

[0043] In S310 (Figure 7(A)), the processor 210 calculates the percentage of attention pixels RdL within the block. The processor 210 refers to the color evaluation information DB (Figure 1) to determine whether each pixel in block BL is a attention pixel or not. Figure 7(C) is a diagram showing an example of the color evaluation information DB. In this embodiment, the color evaluation information DB represents the correspondence between color values ​​(here, RGB values) and flags FL. A true Tr flag FL indicates that the color difference dL is greater than the threshold dLTh, and a false Fls flag FL indicates that the color difference dL is less than or equal to the threshold dLTh. Attention pixels are pixels that have a color value corresponding to the true Tr flag FL. The color difference dL is calculated as follows.

[0044] In this embodiment, a first patch is printed by a forward F pass according to the color values ​​(here, RGB values), and a second patch is printed by a reverse R pass according to the same color values. Each patch is a uniform color region represented by the same color values. The layering order of multiple types of inks differs between these patches. These patches are color-measured by a colorimeter, and the L* value in the CIELAB color space is obtained. The color difference dL is the absolute value of the difference in L* values ​​between the two patches. The threshold dLTh is experimentally determined in advance such that the color difference dL is greater than the threshold dLTh when the color difference between the two patches is easily perceptible to an observer of the patches, and less than or equal to the threshold dLTh when the color difference between the two patches is not easily perceptible to an observer of the patches.

[0045] In this embodiment, the color evaluation information database represents the correspondence between all RGB combinations (in this case, 256*256*256 combinations). Patch printing and color measurement may be performed for a subset of combinations. For example, the RGB gradation values ​​used for patch printing may be selected from 16 gradation values ​​obtained by equally dividing the range from 0 to 255 into 16 parts. That is, patch printing, color measurement, and color difference dL calculation may be performed for 16*16*16 RGB combinations. The color difference dL for other combinations may be calculated by interpolation. The color evaluation information database is prepared in advance by the manufacturer of the multifunction printer 200.

[0046] In S310 (Figure 7(A)), the processor 210 refers to the color evaluation information DB to identify the flag FL for each of the multiple pixels in block BL. The processor 210 calculates the proportion RdL of the multiple pixels in block BL that are attention pixels, which are pixels that show the flag FL of true Tr.

[0047] In S320, the processor 210 determines whether the ratio RdL is greater than or equal to the extra-large threshold th-LL. If the ratio RdL is greater than or equal to the extra-large threshold th-LL (S320: Yes), in S325, the processor 210 determines the degree of banding of block BL to extra-large B-LL and terminates the process shown in Figure 7(A).

[0048] If the ratio RdL is less than the extra-large threshold th-LL (S320: No), in S330, the processor 210 determines whether the ratio RdL is greater than or equal to the large threshold th-L. If the ratio RdL is greater than or equal to the large threshold th-L (S330: Yes), in S335, the processor 210 determines the degree of banding of block BL to be large BL and terminates the process shown in Figure 7(A).

[0049] If the ratio RdL is less than the large threshold th-L (S330: No), in S340, the processor 210 determines whether the ratio RdL is greater than or equal to the medium threshold th-M. If the ratio RdL is greater than or equal to the medium threshold th-M (S340: Yes), in S345, the processor 210 determines the degree of banding of block BL to medium BM and terminates the process shown in Figure 7(A).

[0050] If the threshold dLTh is less than the intermediate threshold th-M (S340: No), in S355, the processor 210 determines the degree of banding of block BL to small BS and terminates the process shown in Figure 7(A).

[0051] The thresholds th-LL, th-L, and th-M may be various values ​​that satisfy the relationship "th-LL > th-L > th-M". The thresholds th-LL, th-L, and th-M are determined experimentally in advance so that the degree of banding appropriately represents the difference in appearance between when a block BL is printed by forward pass processing and when it is printed by reverse pass processing. For example, the extra-large threshold th-LL may be 5%, the large threshold th-L may be 4%, and the medium threshold th-M may be 3%.

[0052] As described above, in S215 (Figure 6), the processor 210 calculates the degree of banding for each block BL in the band image of interest. The degree of banding for the block BL included in the band image of interest indicates the degree of banding in the band image of interest.

[0053] In S217, the processor 210 calculates the total number of various blocks within the band image of interest. In this embodiment, the processor 210 calculates the total number of block BLs NS, NM, NL, and N-LL for small BS, medium BM, large BL, and extra-large B-LL, respectively. The greater the degree of banding in the block BLs included in the band image of interest, the more likely the band image of interest is to show banding. In S220-S250, the processor 210 selects an interlace printing processing mode for the band image of interest from four modes MD1-MD4 to minimize the likelihood of banding being noticeable.

[0054] Figures 8-11 show the path processing and the position of the nozzle NZ in the transport direction Dy. Figures 8-11 represent modes MD1-MD4, respectively. First, we will explain the configuration common to Figures 8-11.

[0055] Figures 8-11 show the range of the transport direction Dy for three consecutive band images BI(i-1), BI(i), and BI(i+1) in the transport direction Dy. In each figure, the right direction is the +Dx direction (forward direction F), and the upward direction is the transport direction Dy. Here, we assume that the i-th band image BI(i) is the band image of interest. The i-th band image BI(i-1) is the adjacent band image that is printed before the band image of interest BI(i), and the i+1th band image BI(i+1) is the adjacent band image that is printed after the band image of interest BI(i).

[0056] Each figure shows the position of the head 410 and multiple nozzles NZ in the transport direction Dy during the k-th (k is an integer) movement process and subsequent multiple movement processes. The movement process is either a pass process P that forms a dot or a skip process SK that moves the head 410 without forming a dot. The pass process P is either a forward pass process Pf, which is a forward pass process PF, or a reverse pass process Pr, which is a reverse pass process P. Above the symbols P or SK, there is a symbol indicating the direction of movement of the print head 410 (forward F or reverse R). In addition, within the head 410 representing each pass process P, multiple nozzles NZ of the nozzle group NC are shown as representatives. The circle mark and triangle mark represent nozzles NZ, respectively. The circle mark represents the nozzle NZ of the forward pass process Pf, and the triangle mark represents the nozzle NZ of the reverse pass process Pr. In the figure, the raster line number NR is the number of the raster line RL in the band image, and is assigned in ascending order in the -Dy direction.

[0057] As described above, the line resolution Rrl is N times the nozzle resolution Rnz. In the example in Figures 8-11, N=3. The total number of raster lines RL contained in one band image, Nrl, may be set to a multiple of N. In the example in Figures 8-11, Nrl=12. Also, the total number of nozzles NZ contained in one nozzle group, Nnz, is set to the same value as the total number of raster lines RL, Nrl (Nnz=Nrl=12). A single pass process P can form dots in the region of three consecutive band images.

[0058] Each figure shows the transport amounts F1, F2, and F3 connecting two heads 410 representing two consecutive movement processes. Transport amounts F1, F2, and F3 indicate the amount of paper PM transported during the transport process performed between the corresponding two movement processes. For example, in the example in Figure 8, a transport process of the first transport amount F1 is performed between pass process P no. k and pass process P no. k+1. Transport amounts F1, F2, and F3 are predetermined so that multiple pass processes P form dots on different raster lines RL. In the examples in Figures 8-11, printing of multiple raster lines RL of the target image OI is performed by repeating three types of transport processes: F1=13, F2=13, and F3=10.

[0059] One nozzle NZ can print a single raster line RL extending in the direction of movement DxM in a single pass P. The right side of Figures 8-11 shows the direction pattern DS. The direction pattern DS shows the correspondence between the raster line RL and the direction of movement of the head 410 in dot formation. A single raster line is represented by four nozzle NZ marks corresponding to four dots representing multiple dots. For example, raster line RLa, number 1 in the band image BI(i) of Figure 8, is represented by four triangular marks. This indicates that the multiple dots of this raster line RLa are formed by the reverse direction pass P.

[0060] To the right of the direction pattern DS, the order of the movement direction of the head 410 (forward direction F or reverse direction R) in the multiple movement processes for printing the band image is shown (hereinafter, the order of movement directions associated with the band image will be referred to as the movement order). For example, the movement order of the band image BI(i) in Figure 8 is RFR. This indicates that the band image BI(i) in question will be printed in three pass processes P in the order of reverse direction R, forward direction F, and reverse direction R. The direction enclosed in parentheses indicates the movement direction of the skip process SK. For example, the order of the movement directions of the band image BI(i) in Figure 9 is RF(R)F. This indicates that the third movement process is a skip process SK in the reverse direction R.

[0061] Next, we will explain the details of each mode MD1-MD4. High-speed mode MD1 (Figure 8) is a mode that performs so-called bidirectional printing. High-speed mode MD1 is a bidirectional printing processing mode in which the printing execution unit 400 performs N pass processing, which represents the alternating execution of forward pass processing Pf and reverse pass processing Pr. In the example in Figure 8, the band image of interest BI(i) is printed in the order of movement of the RFR by three pass processing P. In high-speed mode MD1, forward pass processing Pf and reverse pass processing Pr are performed alternately. After each pass processing P, transport processing is performed. In multiple transport processing, transport amounts F1, F2, and F3 are repeated. In the example in Figure 8, the adjacent band images BI(i-1) and BI(i+1) are also assumed to be printed in high-speed mode MD1.

[0062] In high-speed mode MD1, the band image BI(i) of interest is printed through three pass processing Ps, and a transport process is performed between pass processing Ps. Therefore, the band image BI(i) of interest is printed at high speed.

[0063] When multiple band images consecutive in the transport direction Dy are printed in high-speed mode MD1, the movement order of RFR and FRF alternates. Between two adjacent band images, the number of forward pass processing Pf and the number of reverse pass processing Pr are different. That is, the difference (called the directional difference) obtained by subtracting the number of reverse pass processing Pr from the number of forward pass processing Pf is different between two adjacent band images. Therefore, if a band image contains block BLs that indicate a large degree of banding (for example, extra-large B-LL or large BL (Figure 7(A))), banding may be noticeable.

[0064] The semi-high-speed mode MD2 (Figure 9) is a processing mode in which the print execution unit 400 executes N pass processing P and skip processing SK inserted between them. In the example in Figure 9, the band image is printed by four movement processing operations, including three pass processing P and one skip processing SK inserted between them. In the example in Figure 9, four movement processing operations are performed in the order of RF(R)F to print the band image of interest BI(i). Dots are formed by three pass processing operations P(RFF) included in the four movement processing operations. A transport operation is performed after each pass processing operation P. No transport operation is performed between the skip processing SK and the pass processing P following the skip processing SK. Alternatively, the transport operation between the skip processing SK and the pass processing P before the skip processing SK may be omitted, and a transport operation may be performed between the skip processing SK and the pass processing P following the skip processing SK. In the example in Figure 9, the band image BI(i-1) is printed in high-speed mode MD1. The band image BI(i+1) is printed in semi-high-speed mode MD2.

[0065] In the semi-high-speed mode MD2 of this embodiment, one skip process SK is performed between three pass processes P. Therefore, the number of forward pass processes Pf and the number of reverse pass processes Pr are the same for the band image BI(i) of interest printed in semi-high-speed mode MD2 and the band image BI(i-1) printed in high-speed mode MD1 (in the example in Figure 9, the number of forward pass processes Pf is 2 and the number of reverse pass processes Pr is 1). Consequently, the possibility of noticeable banding between the band image BI(i) of interest and the band image BI(i-1) is reduced.

[0066] The insertion position of the skip process SK between the N pass processing steps P for the band image of interest can be at various positions. For example, when processing the next band image of interest after a band image processed in high-speed mode MD1 in semi-high-speed mode MD2, the skip process SK may be inserted after the last pass processing step P for the previous band image. In the example in Figure 9, the skip process SK is inserted after the last pass processing step P(k+2) for the previous band image BI(i-1). This allows for a quick switch from printing the band image in high-speed mode MD1 to printing the band image in semi-high-speed mode MD2.

[0067] The semi-high-quality mode MD3 (Figure 10) is a mode for bidirectional printing. Unlike the high-speed mode MD1, some raster lines RL are printed through multiple pass processing P. The number of pass processing P is one more than the number in high-speed mode MD1. In this embodiment, the band image of interest is printed through four pass processing P.

[0068] In this embodiment, as explained in Figure 8, assuming that N pass processing P is performed in high-speed mode MD1, the number of forward pass processing Pf is 1 greater than the number of reverse pass processing Pr, or the number of reverse pass processing Pr is 1 greater than the number of forward pass processing Pf. The N+1 pass processing P of the semi-high-quality mode MD3 is formed by decomposing one pass processing P, which is associated with the smaller of the number of forward F and reverse R passes, into two bidirectional pass processing P. As a result, the direction of the last pass processing P is reversed. In the example in Figure 10, assuming that the printing of the band image BI(i) of interest is performed in high-speed mode MD1, the movement order is RFR. This second pass processing P is decomposed into two bidirectional pass processing P. As a result, the direction of the last pass processing P changes from reverse R to forward F. For printing the band image BI(i) of interest, four pass processing P(k+1)-P(k+4) are performed in the movement order RFRF. The second pass processing P(k+2) and the third pass processing P(k+3) form dots on a common set of raster lines RLs. No transport processing is performed between these pass processing P(k+2) and P(k+3). Hereafter, a group of multiple raster lines RLs will be referred to as a partial line group LG. In the example in Figure 10, the band images BI(i-1) and BI(i+1) are printed in high-speed mode MD1.

[0069] In two pass processes P(k+2) and P(k+3) that form dots on a common set of raster lines RLs, the first pass process P(k+2) forms dots in a predetermined area on the raster lines RLs. The second pass process P(k+3) forms dots in the remaining area on the raster lines RLs. Thus, the first pass process P(k+2) forms some of the dots on the raster lines RLs, and the second pass process P(k+3) forms the remaining dots on the raster lines RLs. The areas where dots should be recorded by the first pass process P(k+2) and the areas where dots should be recorded by the second pass process P(k+3) can be various areas. For example, the arrangement of the two types of areas can be determined using various mask patterns (e.g., mask patterns with so-called blue noise characteristics). Alternatively, the two types of areas can be arranged alternately and regularly along the direction Dx.

[0070] As mentioned above, the apparent color can differ between two parts of a printed image that show the same color. The difference in apparent color can be significant between a raster line RL where all dots are formed by a forward pass process Pf and a raster line RL where all dots are formed by a reverse pass process Pr. Multiple raster lines RLs have dots formed by both a preceding pass process P(k+2) and a subsequent pass process P(k+3) in the opposite direction to the preceding pass process P(k+2). In other words, dots are formed on raster lines RLs by both a forward pass process Pf and a reverse pass process Pr (hereinafter, raster lines RLs will also be called bidirectional raster lines RLs). The likelihood that the apparent color of printed bidirectional raster lines RLs (i.e., partial line group LG) will be biased towards the apparent color when all dots are formed by a forward pass process Pf is reduced. Furthermore, the likelihood that the apparent color of the printed partial line group LG will be biased towards the apparent color if all dots were formed by the reverse pass processing Pr is reduced. Thus, a band image containing multiple bidirectional raster lines RLs (e.g., band image BI(i) in Figure 10) can reduce the likelihood of appearing different in color from various other band images that exhibit the same color.

[0071] For example, as shown in Figure 8, the difference in the configuration of multiple raster lines RL between band images BI(i-1) and BI(i) printed in high-speed mode MD1 is as follows: The configuration of band image BI(i) is the same as the configuration of band image BI(i-1) obtained by replacing some of the raster lines RL corresponding to the forward direction F with raster lines RL corresponding to the reverse direction R. Therefore, the apparent colors of the printed band images BI(i-1) and BI(i) can differ significantly.

[0072] On the other hand, as shown in Figure 10, the difference in the configuration of multiple raster lines RL between the band image BI(i-1) printed in high-speed mode MD1 and the band image BI(i) printed in semi-high-quality mode MD3 is as follows. That is, the configuration of band image BI(i) is the same as the configuration of band image BI(i-1) obtained by replacing some of the raster lines RL corresponding to the forward direction F with bidirectional raster lines RLs. Compared to the case where the raster lines RL corresponding to the forward direction F are replaced with raster lines RL corresponding to the reverse direction R, the difference in apparent color between the printed band images BI(i-1) and BI(i) is reduced.

[0073] Furthermore, in the semi-high-quality mode MD3, the total number of raster lines RL in the band image of interest that have dots formed by forward pass processing Pf is the same as the total number of raster lines RL that have dots formed by reverse pass processing Pr (4 lines in the example in Figure 10). In the remaining raster lines RLs of the band image of interest, dots are formed by both forward pass processing Pf and reverse pass processing Pr. Therefore, the difference between the total number of dots formed by forward pass processing Pf and the total number of dots formed by reverse pass processing Pr is reduced. As a result, the apparent color of the band image printed in semi-high-quality mode MD3 may be a color between the apparent color of the band image printed with three pass processing P in FRF and the apparent color of the band image printed with three pass processing P in RFR (FRF and RFR are the order of movement in high-speed mode MD1 (Figure 8)). Thus, the apparent color difference between a band image printed in high-speed mode MD1 and a band image printed in semi-high-quality mode MD3 is mitigated compared to the apparent color difference between two types of band images (FRF and RFR) printed in high-speed mode MD1. As shown in Figure 10, when a band image adjacent to band image BI(i), which is printed in semi-high-quality mode MD3, is printed in high-speed mode MD1, the likelihood of noticeable banding between these band images is reduced.

[0074] Furthermore, in the semi-high-quality mode MD3, skip processing SK is not performed, and forward pass processing Pf and reverse pass processing Pr are performed alternately (i.e., bidirectional printing). Therefore, compared to the case where skip processing SK is also performed, band images can be printed at a faster speed.

[0075] High-quality mode MD4 (Figure 11) is a mode for unidirectional printing. High-quality mode MD4 is a processing mode in which the print execution unit 400 alternately executes pass processing P and skip processing SK. The number of pass processing P is N. Also, the direction of the N pass processing P is the same (forward direction F or reverse direction R). In the example in Figure 11, six movement processing is performed in the order of F(R)F(R)F(R) for printing the band image of interest BI(i). Dots are formed by three pass processing P (FFF) included in the six movement processing. A transport process is performed after each skip processing SK. No transport processing is performed between skip processing SK and the pass processing P preceding it. Alternatively, the transport processing between skip processing SK and the pass processing P following it may be omitted, and transport processing may be performed between pass processing P and the skip processing SK following it. In the example shown in Figure 11, the band images BI(i-1) and BI(i+1) are also printed in high-quality mode MD4.

[0076] In high-quality mode MD4, the direction of the pass processing P that forms the dots is predetermined to one direction selected from the forward direction F and the reverse direction R (forward direction F in the example in Figure 11). Therefore, when multiple band images consecutive in the transport direction Dy are printed in high-quality mode MD4, the likelihood of noticeable banding between the multiple band images is reduced.

[0077] In steps S220-S250 of Figure 6, the processor 210 uses the total number of various blocks in the band image of interest (NS, NM, NL, N-LL) to select a mode suitable for the band image of interest from modes MD1-MD4.

[0078] In S220, the processor 210 determines whether the number of extra-large blocks N-LL is 1 or greater. If the number of extra-large blocks N-LL is 1 or greater (S220: Yes), the processor 210 selects the high-quality mode MD4 in S225 and proceeds to S260. Figure 7(D) shows an example of mode selection. In the example in Figure 7(D), the number of extra-large blocks N-LL for the band image BI(i) is 1 or greater. Therefore, the high-quality mode MD4 is applied to the band image BI(i).

[0079] If the extra-large block count N-LL is less than 1 (Figure 6: S220: No), in S230, the processor 210 determines whether the large block count NL is 1 or greater. If the large block count NL is 1 or greater (S230: Yes), the processor 210 selects the semi-high image quality mode MD3 in S235 and proceeds to S260.

[0080] If the number of large blocks NL is less than 1 (S230: No), in S240, the processor 210 determines whether the number of medium blocks NM is 1 or greater. If the number of medium blocks NM is 1 or greater (S240: Yes), the processor 210 selects the semi-high-speed mode MD2 in S245 and proceeds to S260.

[0081] If the number of medium blocks NM is less than 1 (S240: No), processor 210 selects high-speed mode MD1 in S250 and proceeds to S260.

[0082] Thus, the processor 210 selects a mode with a higher banding suppression capability the greater the degree of banding of block BLs included in the band image of interest. Conversely, the processor 210 selects a mode with a higher printing speed improvement capability the less the degree of banding of block BLs included in the band image of interest.

[0083] In S260, the processor 210 generates printable image data by performing halftone processing using the color-converted data of the band of interest image. The printable image data represents the dot pattern to be formed on the paper PM (Figure 4). The halftone processing may be performed using various methods, such as error diffusion or a dither matrix.

[0084] In S265, the processor 210 determines the configuration for interlaced printing of the band image of interest according to the image data for printing of the band image of interest and the processing mode selected in S220-S250. The processor 210 determines the configuration of multiple move processes and multiple transport processes suitable for the processing mode, as described in Figures 8-11.

[0085] Here, the processor 210 may adjust the interlacing printing configuration of the band image of interest to match the interlacing printing configuration of the adjacent band image which is printed before the band image of interest. Preferably, multiple dots in the adjacent band image are formed by multiple pass processing P associated with the processing mode of the adjacent band image. Preferably, multiple dots in the band image of interest are formed by multiple pass processing P associated with the processing mode of the band image of interest. The processor 210 may associate the move processing for the adjacent band image with the move processing for the band image of interest so that such interlacing printing can proceed.

[0086] For example, if the mode of the adjacent band image is semi-high-speed mode MD2 (Figure 9) and the mode of the band image of interest is semi-high-quality mode MD3 (Figure 10), the processor 210 may use the last three of the four move processes for the adjacent band image as the first three pass processes P for the band image of interest. Also, if the mode of the adjacent band image is high-quality mode MD4 (Figure 11) and the mode of the band image of interest is high-speed mode MD1 (Figure 8), the processor 210 may use the third and sixth of the six move processes for the adjacent band image as the first two pass processes P for the band image of interest.

[0087] Similarly, for other mode combinations, the processor 210 may associate a move operation for an adjacent band image with a move operation for the band image of interest, such that multiple dots in the band image are formed by multiple pass operations P, each corresponding to a processing mode for the band image. For proper interlaced printing, the processor 210 may add a skip operation SK between the two pass operations P. The correspondence between the move operation for an adjacent band image and the move operation for the band image of interest may be predetermined for each mode combination. The processor 210 may determine the configuration for interlaced printing by referring to data defining such correspondences.

[0088] In S270 (Figure 6), the processor 210 determines whether all band images have been processed. If there are unprocessed band images remaining (S270: No), the processor 210 proceeds to S210 and processes the new band images. If all band images have been processed (S270: Yes), the processor 210 terminates the process in Figure 6, i.e., the process in S130 in Figure 5.

[0089] In S160, the processor 210 generates job data using the interlaced printing configuration determined in S130. The job data is data represented in a data format that can be interpreted by the control circuit 490 of the print execution unit 400 (Figure 1) (such job data is also called print data). The processor 210 generates the job data, for example, by arranging data representing the dot formation state in the order used for printing, and adding a printer control code and a data identification code.

[0090] In S170, the processor 210 sends job data to the print execution unit 400. The control circuit 490 of the print execution unit 400 prints the target image OI onto the paper PM according to the job data. The control circuit 490 prints each of the multiple band images BI1-BIn according to the processing mode associated with the band image. Then the process shown in Figure 5 is completed.

[0091] The target image data may represent an image with multiple pages. In this case, the processor 210 may perform color banding mode processing (S130) for each page.

[0092] As described above, in this embodiment, the printing execution unit 400 (Figure 2) comprises a head 410, a transport device 430, and a moving device 440. The head 410 (Figure 3) has L nozzle groups NK, NY, NC, and NM for outputting L types of ink (in this embodiment, L=4). The transport device 430 (Figure 2) transports the paper PM to the print head 410 in the transport direction Dy. The moving device 440 moves the print head 410 in the moving direction DxM, which intersects the transport direction Dy with respect to the paper PM. As shown in Figure 3, the L nozzle groups NK, NY, NC, and NM are arranged in the moving direction DxM. That is, the L nozzle groups NK, NY, NC, and NM are lined up along the moving direction DxM. Each of the L nozzle groups NK, NY, NC, and NM includes a plurality of nozzles NZ whose positions in the transport direction Dy are different from each other. The nozzles NZ output ink to form dots on the sheet.

[0093] The processor 210 of the control device 299 (Figure 1) performs the following processing according to program 232. The processor 210 generates job data by executing S130 and S160 (Figure 5). In S170, the processor 210 sends the job data to the print execution unit 400. As a result, the processor 210 causes the print execution unit 400 to print each of the multiple band images BI1-BIn that form the target image OI (Figure 4) through multiple pass processing P (Figures 8-11). The processor 210 is an example of a band processing unit that performs such processing (S130, S160, S170). Here, the multiple band images BI1-BIn (Figure 4) are arranged on the paper PM in the transport direction Dy. The pass processing P (Figures 8-11) includes the process of forming multiple dots on a raster line RL extending in the movement direction DxM by driving the print head 410 while the print head 410 is moving. The multiple band images BI1-BIn (Figure 4) contain multiple raster lines aligned in the transport direction Dy with a line resolution Rrl that is N times (N is an integer greater than or equal to 2) the nozzle resolution Rnz (Figure 3). The nozzle resolution Rnz (Figure 3) is the resolution of multiple nozzles NZ in the transport direction Dy.

[0094] The processor 210 has a semi-high-quality mode MD3 (Figure 10), which is a processing mode for printing a band image to the print execution unit 400 through multiple pass processing P. As explained in the pass processing P(k+1)-P(k+4) in Figure 10, the semi-high-quality mode MD3 is a bidirectional printing processing mode that causes the print execution unit 400 to perform multiple pass processing P, which represent the alternating execution of forward pass processing Pf and reverse pass processing Pr. Forward pass processing Pf is a pass processing P that moves the print head 410 in the forward direction F, which is parallel to the movement direction DxM. Reverse pass processing Pr is a pass processing P that moves the print head 410 in the reverse direction R, which is opposite to the forward direction F.

[0095] The multiple pass processing P in the semi-high-quality mode MD3 includes a preceding pass processing P(k+2) and a succeeding pass processing P(k+3). The preceding pass processing P(k+2) is a pass processing P that forms a portion of multiple dots in a partial line group LG, which is a group of multiple raster lines RLs representing a portion of the band image BI(i) (hereinafter, such a pass processing P(k+2) will also be called a preceding partial pass processing Pa). In the example in Figure 10, the preceding pass processing P(k+2) is a forward pass processing Pf. Although not shown in the illustration, the movement order of the adjacent band image (i-1) that is printed before the band image BI(i) may be RFR instead of FRF. In this case, the movement order of the band image BI(i) may be FRFR instead of RFRF. Thus, the preceding pass processing P(k+2) may be a reverse pass processing Pr.

[0096] The subsequent pass processing P(k+3) is performed after the preceding pass processing P(k+2) without moving the paper PM in the transport direction Dy. The subsequent pass processing P(k+3) is a pass processing P that forms the remaining dots of multiple sub-line group LG of multiple raster lines RLs (hereinafter, such a pass processing P(k+3) will also be called the subsequent sub-pass processing Pb). The subsequent pass processing P(k+3) moves the print head 410 in the opposite direction to the direction of movement of the print head 410 in the preceding pass processing P(k+2).

[0097] In this configuration, dots are formed on multiple raster lines RLs by both a preceding pass process P(k+2) and a subsequent pass process P(k+3) in the opposite direction to the preceding pass process P(k+2). The likelihood that the apparent color of the printed raster lines RLs will be biased towards the apparent color that would occur if all dots were formed by the forward pass process Pf is reduced. Furthermore, the likelihood that the apparent color of the printed raster lines RLs will be biased towards the apparent color that would occur if all dots were formed by the reverse pass process Pr is also reduced. Therefore, a band image containing multiple raster lines RLs can reduce the likelihood of appearing different in color from various other band images that exhibit the same color. For example, the difference in apparent color between band images BI(i-1) and BI(i) in Figure 10 is reduced compared to the difference in apparent color between band images BI(i-1) and BI(i) in Figure 8. Also, the semi-high-quality mode MD3 is a processing mode for bidirectional printing. Compared to the case where a skip operation SK is performed in addition to the preceding pass operation P(k+2) and the subsequent pass operation P(k+3), high-speed printing is possible.

[0098] Note that forward direction F is an example of a first direction parallel to the movement direction DxM. Forward pass processing Pf is an example of a first-direction pass processing, which is a pass processing P that moves the print head 410 in the first direction. Reverse direction R is an example of a second direction, which is the opposite direction to forward direction F. Reverse pass processing Pr is an example of a second-direction pass processing, which is a pass processing P that moves the print head 410 in the second direction. Semi-high-quality mode MD3 is an example of a first mode for printing a band image to the print execution unit 400 through multiple pass processing, including preceding partial pass processing and succeeding partial pass processing. The band image to which semi-high-quality mode MD3 is applied (for example, band image BI(i) in Figure 10) is an example of a first specific band image to which the first mode is applied.

[0099] Furthermore, in this embodiment, the total number of multiple pass processes P in the semi-high-quality mode MD3 is 4, which is an even number. In the multiple pass processes of the semi-high-quality mode MD3, the number of forward pass processes Pf (2) is the same as the number of reverse pass processes Pr (2). Therefore, the possibility of different colors appearing among multiple band images to which the semi-high-quality mode MD3 is applied is reduced.

[0100] In this embodiment, the processor 210 also has a semi-high-speed mode MD2 (Figure 9). As shown in Figure 9, the total number of pass processes P for printing the adjacent band image BI(i-1), which is printed before the band image BI(i) to which semi-high-speed mode MD2 is applied, can be odd (3 in the example in Figure 9). Semi-high-speed mode MD2 causes the print execution unit 400 to perform a skip process SK, a forward pass process Pf, and a reverse pass process Pr. The skip process SK is a process that moves the print head 410 without forming dots. The number of forward pass processes Pf is the same as the number of forward pass processes Pf for printing the adjacent band image BI(i-1) (2 in Figure 9). The number of reverse pass processes Pr is the same as the number of reverse pass processes Pr for printing the adjacent band image BI(i-1) (1 in Figure 9). This configuration reduces the likelihood that printed band images BI(i) and BI(i-1) will appear to have different colors when band image BI(i) and the adjacent band image BI(i-1) show the same color.

[0101] The semi-high-speed mode MD2 is an example of a second mode for causing the print execution unit 400 to perform the above-mentioned movement processing, including the skip processing SK. The adjacent band image printed after the band image printed by an odd number of pass processing P, to which the semi-high-speed mode MD2 is applied (for example, band image BI(i) in Figure 9), is an example of a second specific band image to which the second mode is applied.

[0102] In this embodiment, there are no other bands between a band image and an adjacent band image. The band image and the adjacent band image represent two band images that are consecutive in the transport direction Dy. The band image and the two adjacent band images represent three band images that are consecutive in the transport direction Dy. The adjacent band image that is printed before the band image of interest (for example, a second specific band image) refers to one of the two band images adjacent to the band image of interest whose printing is completed before the printing of the band image of interest.

[0103] In this embodiment, the processor 210 has Q processing modes (Q is an integer of 2 or more) including the first mode (here, the semi-high quality mode MD3) as processing modes for printing the band image to the print execution unit 400 (in this embodiment, Q=4). In S130 of Figure 5, the processor 210 executes the processing shown in Figure 6. In S215, S217, S220, S230, and S240 of Figure 6, the processor 210 analyzes the band image of interest to determine the magnitude of the apparent color difference in the band image of interest caused by the difference in the direction of movement of the print head 410 in pass processing P, in Q steps. As explained in Figures 7(A) to 7(D), the degree of banding of block BL calculated in S215 (Figure 6) (small BS, medium BM, large BL, extra-large B-LL) indicates the magnitude of the apparent color difference caused by the difference in the direction of movement of the print head 410 in pass processing P. The total number of various blocks NS, NM, NL, and N-LL calculated in S217 are examples of parameters that indicate the magnitude of the apparent color difference of the band image of interest due to differences in the direction of the pass processing P. In S225, S235, S245, and S250, the processor 210 selects a processing mode that corresponds to the stages of the magnitude of the apparent color difference of the band image of interest. In S265, the processor 210 determines the configuration of interlaced printing (including a configuration of multiple move processes and multiple transport processes) according to the selected processing mode. In S160 and S170 (Figure 5), the processor 210 causes the print execution unit to print the band image of interest according to the determined interlaced printing configuration (i.e., the selected processing mode). With this configuration, the processor 210 can cause the print execution unit to print the band image of interest in a processing mode that corresponds to the stages of the magnitude of the apparent color difference of the band image of interest.

[0104] Furthermore, in this embodiment, the total number of processing modes Q is 3 or more. Therefore, the processor 210 can print the band image of interest to the print execution unit using a processing mode suitable for the magnitude of the apparent color difference in the band image of interest, compared to the case where the total number of processing modes Q is less than 3.

[0105] Furthermore, in this embodiment, the processor 210 has multiple processing modes, including a first mode (here, a semi-high-quality mode MD3), as processing modes for printing the band image to the print execution unit 400. The multiple processing modes include the above-mentioned modes MD1, MD2, and MD3 (Figures 8, 9, and 10).

[0106] In high-speed mode MD1 (Figure 8), three pass processing steps P in the order RFR and three pass processing steps P in the order FRF may be performed. In semi-high-speed mode MD2 (Figure 9), three pass processing steps P (RFF) included in four RF(R)F movement processes and three pass processing steps P (FFR) included in four F(R)FR movement processes may be performed. In semi-high-quality mode MD3 (Figure 10), four pass processing steps P in the order RFRF may be performed. Although not shown in the figure, four pass processing steps P in the order FRFR may also be performed.

[0107] Thus, the multiple modes MD1, MD2, and MD3 cause the print execution unit 400 to perform both printing of the band image using multiple pass processing P starting from forward pass processing Pf, and printing of the band image using multiple pass processing P starting from reverse pass processing Pr. If the multiple pass processing P for printing the band image always starts from the same direction of pass processing P, the number of skip processing SK may increase in order to adjust the direction of movement of the head 410. As a result, the printing speed may decrease. When any of modes MD1, MD2, or MD3 is applied to multiple consecutive band images, the skip processing SK to adjust the direction of movement of the head 410 can be omitted, thus reducing the possibility of a decrease in printing speed.

[0108] Furthermore, in this embodiment, the semi-high-quality mode MD3 (Figure 10), which is an example of the first mode, can cause the print execution unit 400 to print a band image using multiple pass processing P (RFRF) starting from reverse pass processing Pr. These multiple pass processing P include a preceding partial pass processing Pa and a succeeding partial pass processing Pb that are performed consecutively without transporting the paper PM. Although not shown in the figure, the semi-high-quality mode MD3 can also cause the print execution unit 400 to print a band image using multiple pass processing P (FRFR) starting from forward pass processing Pf. The second and third pass processing P of these multiple pass processing P correspond to the preceding partial pass processing Pa and the succeeding partial pass processing Pb, respectively, that are performed consecutively without transporting the paper PM. Thus, the semi-high-quality mode MD3 can cause the print execution unit 400 to perform both printing a band image using multiple pass processing P starting from forward pass processing Pf and printing a band image using multiple pass processing P starting from reverse pass processing Pr. When the semi-high-quality mode MD3 is applied to multiple consecutive band images, the skip process SK can be omitted to adjust the movement direction of the head 410, thus reducing the possibility of a decrease in printing speed.

[0109] B. Second example: Figure 12 is a flowchart representing a second embodiment of image processing. The only difference from the image processing in Figure 5 is that in this embodiment, the processing mode is selected for each page. The available processing modes are the same as in the first embodiment, four modes MD1-MD4 (Figures 8-11). In this embodiment, program 232 is configured to execute the processing shown in Figure 12. The processor 210 executes the processing shown in Figure 12 according to program 232.

[0110] S110 and S120 are the same as S110 and S120 in Figure 5, respectively. The processor 210 acquires the target image data and performs color conversion processing on the target image data.

[0111] In S130b, processor 210 performs color banding mode processing. Unlike the processing in S130 (Figure 5), processor 210 selects a processing mode for each page.

[0112] Figure 13 is a flowchart illustrating an example of color banding mode processing. The difference from the processing shown in Figure 6 is that the processing mode is selected per page, rather than per band image.

[0113] In S210b, the processor 210 selects the image of an unprocessed page from among the U pages (where U is an integer greater than or equal to 1) represented by the target image data as the page of interest image. Then, the processor 210 obtains the data of the page of interest image from the target image data and the color-converted target image data.

[0114] In S215b, the processor 210 calculates the degree of banding for each block within the page image of interest. The process for calculating the degree of banding for block BL is the same as the process described in Figures 7(A)-7(C).

[0115] In S217b (Figure 13), the processor 210 calculates the total number of various blocks within the page image of interest. In this embodiment, the processor 210 calculates the total number of block BLs Np-S, Np-M, Np-L, and Np-LL for small BS, medium BM, large BL, and extra-large B-LL, respectively. The greater the degree of banding of the block BLs included in the page image of interest, the more likely the page image of interest is to exhibit banding. In this embodiment, the interlace printing processing mode for the page image of interest is selected from four modes MD1-MD4 to minimize the likelihood of noticeable banding.

[0116] S220b-S250b is the same process as in S220-S250 in Figure 6, where the total number of various blocks NS, NM, NL, and N-LL in the band image of interest is replaced with the total number of various blocks Np-S, Np-M, Np-L, and Np-LL in the page image of interest.

[0117] If the number of extra-large blocks Np-LL is 1 or more (S220b:Yes), high-quality mode MD4 is selected (S225b). If the number of extra-large blocks Np-LL is less than 1 and the number of large blocks Np-L is 1 or more (S220b:No, S230b:Yes), semi-high-quality mode MD3 is selected (S235b). If the number of large blocks Np-L is less than 1 and the number of medium blocks Np-M is 1 or more (S230b:No, S240b:Yes), semi-high-speed mode MD2 is selected (S245b). If the number of medium blocks NM is less than 1 (S240:No), high-speed mode MD1 is selected (S250b).

[0118] In S260b, processor 210 generates print-ready image data by performing halftone processing using the color-converted data of the page image in question. The halftone method is the same as the halftone method in S260 shown in Figure 6.

[0119] In S265b, the processor 210 determines the configuration for interlaced printing of the page of interest image according to the image data for printing of the page of interest image and the processing mode selected in S220b-S250b. In this embodiment, multiple band images included in the page of interest image are processed in the same processing mode.

[0120] In S270b, the processor 210 determines whether all pages have been processed. If there are unprocessed pages remaining (S270b: No), the processor 210 proceeds to S210b and processes new pages. If all pages have been processed (S270b: Yes), the processor 210 terminates the process shown in Figure 13, i.e., the process shown in S130b in Figure 12.

[0121] S160 and S170 are the same as S160 and S170 in Figure 5, respectively. The processor 210 generates job data and sends the generated job data to the print execution unit 400. The control circuit 490 of the print execution unit 400 prints the images of U pages onto U sheets of paper PM according to the job data. Then the process in Figure 12 is completed.

[0122] As described above, in this embodiment, the processor 210 selects a processing mode for each page. The processor 210 can cause the print execution unit to print the image of each page using a processing mode appropriate for that page.

[0123] In this embodiment, the image processing for printing is performed in the same manner as in the first embodiment, except that the processing mode is selected for each page. Therefore, this embodiment can provide the same various advantages as those provided by the first embodiment.

[0124] C. Third embodiment: Figure 14 is a flowchart representing a third embodiment of image processing. The main difference from the image processing in Figures 5 and 12 is that in this embodiment, the processing mode is selected according to user instructions. The available processing modes are the same as in the first embodiment, four modes MD1-MD4 (Figures 8-11). In this embodiment, program 232 is configured to execute the processing shown in Figure 14. The processor 210 executes the processing shown in Figure 14 according to program 232.

[0125] S110 and S120 are the same as S110 and S120 in Figure 5, respectively. The processor 210 acquires the target image data and performs color conversion processing on the target image data.

[0126] In the S132c, the processor 210 displays a settings screen on the display unit 240 that accepts user instructions for selecting a processing mode. Figure 15 shows an example of the settings screen. This settings screen UI represents a slider SL and a completion button BT. The user can select one of four levels, from "high speed" to "high quality," by operating the slider SL via the operation unit 250. The four levels correspond to four modes MD1-MD4 (Figures 8-11). The user can complete the level selection by operating the completion button BT via the operation unit 250.

[0127] In S134c (Figure 14), the processor 210 obtains user instructions for level selection in response to the operation of the completion button BT. In S136c, the processor 210 determines the processing mode according to the user instructions. In this embodiment, the processing mode is applied commonly to all pages of the target image data. Alternatively, the processor 210 may allow the user to select the processing mode for each page.

[0128] In S140c, the processor 210 generates image data for printing by performing halftone processing using the data of the color-converted target image. The halftone method is the same as the halftone method in S260 in Figure 6.

[0129] In S150c, the processor 210 determines the configuration for interlaced printing for each page of the target image data, according to the image data for printing and the processing mode determined in S136c.

[0130] S160 and S170 are the same as S160 and S170 in Figure 5, respectively. The processor 210 generates job data and sends the generated job data to the print execution unit 400. The control circuit 490 of the print execution unit 400 prints the image of each page according to the job data. Then the process in Figure 14 is completed.

[0131] As described above, in this embodiment, the processor 210 has V processing modes (where V is an integer of 3 or more) including the first mode (here, the semi-high quality mode MD3) as processing modes for printing band images to the print execution unit 400. The processor 210 performs the following processing according to the program 232. In S132c, the processor 210 displays a setting screen UI (Figure 15) on the display unit 240. The setting screen UI is an example of a screen that accepts user instructions for selecting a processing mode for printing multiple band images to the print execution unit 400. In S136c, the processor 210 determines a processing mode for printing multiple band images to the print execution unit 400 according to the user's instructions. With this configuration, the processor 210 can print band images to the print execution unit 400 using a processing mode suitable for the user's instructions.

[0132] In this embodiment, the image processing for printing is performed in the same manner as in the second embodiment, except that the processing mode is determined according to user instructions. Therefore, this embodiment can provide the same various advantages as those provided by the second embodiment.

[0133] D. Variations: (1) The process for determining the magnitude of the apparent color difference in the band image of interest is not limited to the process shown in Figure 6, but may be any of the various processes. For example, the threshold values ​​used in S220, S230, and S240 may be greater than 1.

[0134] (2) When the semi-high-quality mode MD3 (Figure 10) is applied, the configuration of interlaced printing is a configuration in which forward pass processing Pf and reverse pass processing Pr are performed alternately, and may include various configurations including a preceding partial pass processing Pa and a succeeding partial pass processing Pb. For example, the processor 210 may determine the configuration of interlaced printing by decomposing one of the N pass processing Ps, assuming that the high-speed mode MD1 is applied, into a preceding partial pass processing Pa and a succeeding partial pass processing Pb. Here, it is preferable that the pass processing P that is performed before the last pass processing P and is associated with the smaller of the number of forward pass processing Pfs and the number of reverse pass processing Prs is decomposed. With this configuration, the direction of the pass processing P after the decomposed pass processing P is reversed, so the difference between the total number of dots formed by the forward pass processing Pf and the total number of dots formed by the reverse pass processing Pr is reduced. Therefore, the band image printed in semi-high-quality mode MD3 can reduce the apparent color difference between it and various other band images that exhibit the same color. Furthermore, semi-high-quality mode MD3 allows the print execution unit 400 to perform only one of the following: printing of the band image by multiple pass processing P starting from forward pass processing Pf, or printing of the band image by multiple pass processing P starting from reverse pass processing Pr. In either case, the first specific band image to which semi-high-quality mode MD3 is applied is not limited to the band images to which semi-high-quality mode MD3 is applied according to the embodiments in Figures 6, 13, and 14, but may be various other band images.

[0135] (3) When the semi-high-speed mode MD2 (Figure 9) is applied, the configuration of interlaced printing may include various configurations including a skip process SK, forward pass processes Pf the same number of times as the forward pass processes Pf for the adjacent band image to be printed first, and reverse pass processes Pr the same number of times as the reverse pass processes Pr for the adjacent band image to be printed first. Among the multiple movement processes including the skip process SK and the pass processes P, the order of the skip process SK may be in various orders. Here, it is preferable that the number of skip processes SK is 1. In any case, the band images to which the semi-high-speed mode MD2 is applied are not limited to the band images to which the semi-high-speed mode MD2 is applied according to the embodiments of Figures 6, 13, and 14, but may be various band images. Here, the adjacent band image to be printed after the band image printed by an odd number of pass processes P, to which the semi-high-speed mode MD2 is applied (for example, the band image BI(i) in Figure 9) is an example of a second specific band image to which the second mode is applied.

[0136] (4) In high-quality mode MD4 (Figure 11), dots may be formed by reverse pass processing Pr instead of forward pass processing Pf.

[0137] (5) The available processing modes are not limited to modes MD1-MD4 (Figures 8-11) and may include various other modes. For example, one or more modes arbitrarily selected from modes MD1-MD4 may be omitted. For example, the available modes may include high-speed mode MD1 and semi-high-quality mode MD3. The available modes may further include semi-high-speed mode MD2. It is preferable that the available modes include semi-high-quality mode MD3, more preferably semi-high-speed mode MD2, particularly preferably high-speed mode MD1, and most preferably high-quality mode MD4.

[0138] In either case, the available modes may be configured to cause the print execution unit 400 to perform only one of the following: printing of a band image by multiple pass processing P starting with forward pass processing Pf, or printing of a band image by multiple pass processing P starting with reverse pass processing Pr.

[0139] (6) As in the embodiment shown in Figure 6, when the magnitude of the apparent color difference of the band image of interest caused by the difference in the direction of movement of the print head 410 is determined, the number of magnitude steps Q may be a variety of numbers of 2 or more. The number of magnitude steps Q may be the same as the total number of available modes.

[0140] (7) The ratio N of the resolution Rrl (Figure 4) of the raster line RL in the transport direction Dy to the resolution Rnz (Figure 3) of the nozzle NZ in the transport direction Dy is not limited to 3, but may be any integer greater than or equal to 2. In any case, a single band image can be printed by N or more pass processes P.

[0141] The ratio N may be any odd number. Here, when bidirectional printing is performed, as in the example in Figure 8, the total number of raster lines RL corresponding to the forward direction F and the total number of raster lines RL corresponding to the reverse direction R will differ between two consecutive band images. Therefore, banding may be noticeable. Here, the available modes may include high-speed mode MD1 and semi-high-quality mode MD3. When a band image printed in high-speed mode MD1 is adjacent to a band image printed in semi-high-quality mode MD3, the likelihood of noticeable banding between these band images is reduced. Note that the ratio N may be any even number.

[0142] (8) The total number of nozzles NZ in each nozzle group NK, NY, NC, NM (Figure 3), Nnz, may be any integer greater than or equal to 2. Also, the total number of raster lines RL (Figure 4) contained in a single band image, Nrl, may be any integer greater than or equal to 2. Here, the total number of raster lines RL, Nrl, may be the same as the total number of nozzles NZ, Nnz, or it may be different from the total number Nnz.

[0143] (9) The number of ink types L available for use by the printing execution unit 400 is not limited to 4, but may be any number of 2 or more. For example, black K ink may be omitted. In addition to cyan C ink, light cyan ink may be available. Two types of chromatic inks (for example, cyan C and magenta M) may be available. Two types of achromatic inks (for example, black K and gray) may be available.

[0144] (10) In determining the flag FL in Figure 7(C), various evaluation values ​​representing color differences may be used instead of the difference in L* values ​​in the CIELAB color space. For example, the color difference in the CIELAB color space (e.g., the color difference according to the CIE DE2000 color difference formula) may be used.

[0145] (11) In the embodiment shown in Figure 4, two adjacent band images are aligned in the transport direction Dy without overlapping and without any gaps. Alternatively, two adjacent band images may be arranged so that parts of them overlap. Multiple raster lines RL in the overlapping region may be distributed between the two band images.

[0146] (12) The total number of dot types Nd that can be formed by the printing execution unit 400 may be any integer of 1 or more. For example, the total number of dot types Nd may be 1. That is, an image may be represented by the presence or absence of dots. Alternatively, two or more types of dots having different sizes may be formed. In either case, the halftone processing may be configured to determine the formation state of each of the Nd types of dots.

[0147] (12) The configuration of the print execution unit 400 is not limited to the configuration described in Figures 2 and 3, but may be any other configuration. For example, the head drive unit 420 may be included in the print head 410. The ink supply unit 450 (including the cartridge mounting unit 451) may be mounted on the carriage 443. The multifunction printer 200 may have a large-capacity ink tank instead of the ink cartridges KC, YC, CC, MC and the cartridge mounting unit 451. The configuration of the print execution unit may be any configuration comprising a print head, a transport device, and a moving device. The configuration of the print head may be any configuration having L nozzle groups for outputting L types (L is an integer of 2 or more) of ink. The configuration of the transport device may be any configuration that transports the sheet in the transport direction relative to the print head. The configuration of the moving device may be any configuration that moves the print head in a moving direction intersecting the transport direction relative to the sheet.

[0148] (13) The medium used for printing is not limited to paper PM, but may be various sheets such as film or cloth.

[0149] (14) The control device that controls the print execution unit is not limited to the control device 299 in Figure 1, but may be any type of device. For example, the control device may be an external data processing device connected to the print execution unit (e.g., a personal computer, tablet computer, smartphone, etc.). Alternatively, multiple devices (e.g., computers) that can communicate with each other via a network may each share a portion of the image processing function performed by the control device, and together they may provide the image processing function (a system equipped with these devices corresponds to the control device).

[0150] In each of the above embodiments, some of the configurations implemented by hardware may be replaced with software, and conversely, some or all of the configurations implemented by software may be replaced with hardware. For example, the processing in Figure 6 or Figure 13 may be performed by a dedicated hardware circuit such as an Application Specific Integrated Circuit (ASIC).

[0151] Furthermore, if some or all of the functions of this disclosure are implemented by a computer program, that program may be provided in the form of a computer-readable recording medium (e.g., a non-temporary recording medium). The program may be used while stored on the same or a different recording medium (computer-readable recording medium) as it was provided. "Computer-readable recording medium" is not limited to portable recording media such as memory cards and CD-ROMs, but may also include internal storage devices within a computer, such as various ROMs, and external storage devices connected to a computer, such as hard disk drives.

[0152] The above embodiments and modifications can be combined as appropriate. Furthermore, the above embodiments and modifications are provided to facilitate understanding of this disclosure and do not limit the present invention. The present invention can be modified and improved without departing from its spirit, and equivalents thereof are included. [Explanation of symbols]

[0153] 200…Multifunction printer, 210…Processor, 215…Storage device, 220…Volatile storage device, 230…Non-volatile storage device, 232…Program, 240…Display unit, 250…Operation unit, 270…Communication interface, 280…Scanner unit, 299…Control device, 400…Print execution unit, 410…Print head, 411…Nozzle forming surface, 420…Head drive unit, 430…Transport device, 431…First roller, 432…Second roller, 440…Moving device, 443…Carriage, 444…Sliding shaft, 445…Belt, 446…Pulley, 450…Ink supply unit, 451…Cartridge mounting unit, 452…Tube, 453…Buffer tank, 490…Control circuit, NZ… Nozzle, NK, NY, NC, NM… Nozzle group, DxM… Movement direction, F… Forward direction, R… Reverse direction, Dy… Transport direction, PT… Platen, PM… Paper, Rnz… Nozzle resolution, Rrl… Line resolution, KC, YC, CC, MC… Ink cartridge, UI… Settings screen, BT… Complete button, SL… Slider, MD1… High-speed mode, MD2… Semi-high-speed mode, MD3… Semi-high-quality mode, MD4… High-quality mode, OI… Target image, P… Pass processing, Pa… Preceding partial pass processing, Pb… Successor partial pass processing, Pf… Forward pass processing, Pr… Reverse pass processing, SK… Skip processing, RL… Raster line, RLs… Bidirectional raster line, LG… Partial line group

Claims

1. A control device for controlling the printing execution unit, The aforementioned printing execution unit, A print head having L nozzle groups for outputting L types of ink (where L is an integer of 2 or more), A conveying device that conveys a sheet in the conveying direction relative to the print head, A moving device that moves the print head in a moving direction intersecting the transport direction with respect to the sheet, Equipped with, The L nozzle groups are arranged in the direction of movement. The L nozzle groups include a plurality of nozzles whose positions in the transport direction are different from each other, and which are for outputting ink to form dots on a sheet. The control device is A band processing unit prints a plurality of band images, which form a target image to be processed and are arranged in the transport direction on a sheet, to the print execution unit by a plurality of pass processing, wherein the pass processing includes a process of forming a plurality of dots on a raster line extending in the transport direction by driving the print head while the print head is moving, and the plurality of band images include a plurality of raster lines arranged in the transport direction with a resolution of N times (N is an integer of 2 or more) the resolution of the plurality of nozzles in the transport direction, the band processing unit comprises The band processing unit has a first mode, which is a processing mode for printing a first specific band image included in the plurality of band images to the print execution unit through multiple pass processing steps. The first mode is a bidirectional printing processing mode in which the print execution unit performs multiple pass processing operations, which represent the alternating execution of a first direction pass processing, which is a pass processing operation that moves the print head in a first direction parallel to the direction of movement, and a second direction pass processing, which is a pass processing operation that moves the print head in a second direction opposite to the first direction. The multiple pass processing in the first mode is A preceding partial pass process, which is a first directional pass process or a second directional pass process, that forms a portion of a portion of a subline group, which is a group of multiple raster lines representing a portion of the first specific band image, A subsequent partial pass processing is a pass processing that forms the remaining dots of the partial line group without moving the sheet in the transport direction after the preceding partial pass processing, wherein the subsequent partial pass processing moves the print head in the opposite direction to the direction of movement of the print head in the preceding partial pass processing, including, Control device.

2. A control device according to claim 1, The total number of passes in the first mode is even. In the multiple pass processing in the first mode, the number of first-direction pass processing is the same as the number of second-direction pass processing. Control device.

3. A control device according to claim 1 or 2, The band processing unit has a second mode, which is a processing mode for causing the print execution unit to print a second specific band image included in the plurality of band images. The total number of passes required for printing an adjacent band image that is printed before the second specific band image is odd. The second mode is, A process that moves the print head without forming dots, The same number of first-direction pass processes as the number of first-direction pass processes for printing the adjacent band image, The same number of second-direction pass processes as the number of second-direction pass processes for printing the adjacent band image, The printing execution unit is to execute the following: Control device.

4. A control device according to claim 1 or 2, The band processing unit has Q processing modes (where Q is an integer of 2 or more) including the first mode, as processing modes for printing the band images included in the plurality of band images to the printing execution unit. The aforementioned band processing unit, By analyzing the band image of interest, the magnitude of the apparent color difference in the band image of interest caused by the difference in the direction of movement of the print head during the pass processing is determined in Q stages corresponding to each of the Q processing modes. A processing mode that corresponds to the stages of magnitude of the apparent color differences in the band image of interest is used to cause the print execution unit to print the band image of interest. Control device.

5. A control device according to claim 4, A control device in which the total number Q of the processing modes is 3 or more.

6. A control device according to claim 1 or 2, The band processing unit has a plurality of processing modes, including the first mode, as processing modes for printing the band images included in the plurality of band images to the print execution unit. The plurality of processing modes include a plurality of processing modes that cause the printing execution unit to perform both printing of a band image by multiple pass processing starting from the first direction pass processing and printing of a band image by multiple pass processing starting from the second direction pass processing. Control device.

7. A control device according to claim 1 or 2, The first mode causes the printing execution unit to perform both: printing of a band image by multiple pass processing starting from the first directional pass processing, which includes the preceding partial pass processing and the succeeding partial pass processing; and printing of a band image by multiple pass processing starting from the second directional pass processing, which includes the preceding partial pass processing and the succeeding partial pass processing. Control device.

8. A control device according to claim 1 or 2, The band processing unit has V processing modes (where V is an integer of 3 or more) including the first mode, as processing modes for printing the band images included in the plurality of band images to the printing execution unit. The aforementioned band processing unit, A screen is displayed on the display device that accepts user instructions for selecting a processing mode for printing the plurality of band images to the print execution unit. The processing mode is determined to cause the user to print the plurality of band images to the print execution unit according to the user's instructions. Control device.

9. A method for controlling the printing execution unit, The aforementioned printing execution unit, A print head having L nozzle groups for outputting L types of ink (where L is an integer of 2 or more), A conveying device that conveys a sheet in the conveying direction relative to the print head, A moving device that moves the print head in a moving direction intersecting the transport direction with respect to the sheet, Equipped with, The L nozzle groups are arranged in the direction of movement. The L nozzle groups include a plurality of nozzles whose positions in the transport direction are different from each other, and which are for outputting ink to form dots on a sheet. The control method described above is A band processing step comprising printing a plurality of band images, which form a target image to be processed and are arranged on a sheet in the transport direction, to the printing execution unit by a plurality of pass processing steps, wherein the pass processing steps include a process of forming a plurality of dots on a raster line extending in the transport direction by driving the print head while the print head is moving, and the plurality of band images include a plurality of raster lines arranged in the transport direction with a resolution of N times (N is an integer of 2 or more) the resolution of the plurality of nozzles in the transport direction, The band processing step includes a step of printing the first specific band image included in the plurality of band images to the printing execution unit in a first mode, which is a processing mode for printing the first specific band image to the printing execution unit through multiple pass processing steps, The first mode is a bidirectional printing processing mode in which the print execution unit performs multiple pass processing operations, which represent the alternating execution of a first direction pass processing, which is a pass processing operation that moves the print head in a first direction parallel to the direction of movement, and a second direction pass processing, which is a pass processing operation that moves the print head in a second direction opposite to the first direction. The multiple pass processing in the first mode is A preceding partial pass process, which is a first directional pass process or a second directional pass process, that forms a portion of a portion of a subline group, which is a group of multiple raster lines representing a portion of the first specific band image, A subsequent partial pass processing is a pass processing that forms the remaining dots of the partial line group without moving the sheet in the transport direction after the preceding partial pass processing, wherein the subsequent partial pass processing moves the print head in the opposite direction to the direction of movement of the print head in the preceding partial pass processing, including, Control method.

10. A program for controlling the printing execution unit, The aforementioned printing execution unit, A print head having L nozzle groups for outputting L types of ink (where L is an integer of 2 or more), A conveying device that conveys a sheet in the conveying direction relative to the print head, A moving device that moves the print head in a moving direction intersecting the transport direction with respect to the sheet, Equipped with, The L nozzle groups are arranged in the direction of movement. The L nozzle groups include a plurality of nozzles whose positions in the transport direction are different from each other, and which are for outputting ink to form dots on a sheet. The aforementioned program, A band processing function that causes a printing execution unit to print a plurality of band images, which form a target image and are arranged on a sheet in the transport direction, by multiple pass processing, wherein the pass processing includes a process of forming a plurality of dots on a raster line extending in the transport direction by driving the print head while the print head is moving, and the plurality of band images include a plurality of raster lines arranged in the transport direction with a resolution of N times (N is an integer of 2 or more) the resolution of the plurality of nozzles in the transport direction, and the band processing function is implemented by a computer. The band processing function includes a function that causes the print execution unit to print a first specific band image included in the plurality of band images in a first mode, which is a processing mode for printing the first specific band image to the print execution unit through multiple pass processing, The first mode is a bidirectional printing processing mode in which the print execution unit performs multiple pass processing operations, which represent the alternating execution of a first direction pass processing, which is a pass processing operation that moves the print head in a first direction parallel to the direction of movement, and a second direction pass processing, which is a pass processing operation that moves the print head in a second direction opposite to the first direction. The multiple pass processing in the first mode is A preceding partial pass process, which is a first directional pass process or a second directional pass process, that forms a portion of a portion of a subline group, which is a group of multiple raster lines representing a portion of the first specific band image, A subsequent partial pass processing is a pass processing that forms the remaining dots of the partial line group without moving the sheet in the transport direction after the preceding partial pass processing, wherein the subsequent partial pass processing moves the print head in the opposite direction to the direction of movement of the print head in the preceding partial pass processing, including, program.

Images