JP2015192308A - Printing apparatus and image processing method - Google Patents

Abstract

An image processing method capable of suppressing an increase in processing time of halftone processing and a printing apparatus that performs image processing by this method are provided.
A printer includes a dividing unit that arranges divided image data obtained by dividing the image data in the width direction of the image data in the width direction, and a basic dither mask, from the left side to the right side of the divided image data. A halftone processing unit 47 that performs halftone processing, and an offset amount calculation unit that calculates an offset amount that is a difference in the width direction between the boundary of the divided image data and the basic dither mask 34 across the boundary. . The halftone processing unit 47 uses the basic dither mask 34 for the left divided image data, and uses the reflected dither mask that reflects the offset amount in the basic dither mask 34 for the right divided image data.
[Selection] Figure 1

Description

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

  In recent years, printing apparatuses such as printers and copiers require a large-capacity line memory as the resolution of an output image becomes higher, for example, 2400 dpi or 2800 dpi or higher. For this reason, when image processing such as smoothing processing and halftone processing is performed on a high-resolution image, the line memory may be larger than the capacity that can be held by the CPU of the printing apparatus.

  In order for the CPU to process such a high-resolution image, the CPU divides the image data input to the printing apparatus into a plurality of image data in the width direction, and performs image processing for each of the divided image data. Execute. As a result, the image data that the CPU performs image processing at a time is reduced, so that the line memory held for performing image processing on the divided image data can be reduced (see, for example, Patent Document 1).

JP-A-9-9066

  When halftone processing is performed on the image data DR, as an example, as shown in FIG. 14A, the dither mask DM is in the width direction (main scanning direction) of the image data DR and in a direction orthogonal to the width direction. They are arranged in a certain transport direction (sub-scanning direction). Further, when the dither mask DM is arranged in the sub-scanning direction, the dither mask DM is arranged shifted by a predetermined amount ΔX in the main scanning direction in order to suppress deterioration in image quality.

  When the dither mask DM is arranged on the image data DR as described above, as shown in FIG. 14A, when the image data DR is divided, the divided left image data DR1 and right image data are divided. The dither mask DM may straddle the boundary BR with DR2. For this reason, the boundary MR between the dither mask DM straddling the boundary BR and the right adjacent dither mask DM does not match the boundary BR between the left image data DR1 and the right image data DR2.

  In such a state, each of the left image data DR1 and the right image data DR2 is arranged in a uniform dither mask DM, for example, as in the dither mask DM with respect to the left image data DR1 in FIG. If set, the following problems occur: For example, the dither mask DM arranged at the left end of the left image data DR1 is coincident with the left end of the left image data DR1, and when matching the relationship, the dither mask arranged at the left end of the right image data DR2 The left end of DM is arranged so as to coincide with the boundary BR between the left image data DR1 and the right image data DR2. Therefore, as shown in FIG. 14B, a dither mask DM1 for performing halftone processing on the right end of the left image data DR1, and a dither mask for performing halftone processing on the left end of the right image data DR2. DM2 overlaps as shown by hatching in the figure. For this reason, the continuity of the dither mask DM is lost with respect to the image data DR in the main scanning direction. This may reduce the quality of the printed image.

  In order to solve this problem, it is conceivable to set the mask table of the dither mask DM2 and the start position of the halftone process in the dither mask DM2 so as not to lose the continuity of the dither mask DM. This dither mask DM2 is set every time the dither mask DM2 is arranged in the sub-scanning direction.

  The calculation of the dither mask DM2 is performed by a CPU (not shown) of the printing apparatus, and the calculation result is transferred to a halftone processing unit (not shown) that performs halftone processing. Then, the halftone processing unit performs halftone processing on the right image data DR2 based on the set dither mask DM2.

  However, since the mask table and calculation result of the dither mask DM2 are transferred from the CPU to the halftone processing unit, the processing time of the halftone processing is increased by this transfer time. In particular, since the dither mask DM2 is set every time the dither mask DM2 is arranged in the sub-scanning direction, the processing time of the halftone process becomes remarkably long.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image processing method capable of suppressing an increase in processing time of halftone processing and a printing apparatus that performs image processing using this method. Is to provide.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A printing apparatus that solves the above-described problem is a printing apparatus that prints an image on a medium. The printing apparatus divides the image in the width direction of the image and arranges the divided images in the width direction; Based on the dither mask, a halftone processing unit that performs a halftone process from an image on one side in the width direction to an image on the other side of the divided image, and a boundary between the divided images, An offset amount calculation unit that calculates an offset amount that is a difference in the width direction from the basic dither mask that straddles the boundary, and the halftone processing unit applies the image on the one side of the image after the division. Uses the basic dither mask, and a reflection dither mask reflecting the offset amount in the basic dither mask is used for the image on the other side of the divided images.

  According to the above configuration, the halftone processing unit performs halftone processing on the image on one side of the divided images using the basic dither mask, and performs basic dithering on the image on the other side of the divided images. Halftone processing is performed using a reflection dither mask in which the offset amount is reflected on the mask. For this reason, since a common basic dither mask and a common reflection dither mask are used for each divided image, each time the basic dither mask and the reflection dither mask are arranged in the direction orthogonal to the width direction in the image, the basic dither mask is used. There is no need to set the halftone process start position and mask table for each of the dither mask and the reflected dither mask. This eliminates the need to transfer the start position of the halftone process and the mask table to the halftone processing unit every time the basic dither mask and the reflected dither mask are set, so that the processing time of the halftone processing by the halftone processing unit is long. It can be suppressed.

In the printing apparatus, it is preferable that the offset amount calculation unit calculates the offset amount for each color of the liquid ejected onto the medium.
According to the above configuration, it is possible to set the start position of the halftone process of the divided image in the basic dither mask and the reflected dither mask for each liquid color, thereby suppressing deterioration in image quality accuracy for each liquid color. can do.

The printing apparatus preferably includes a storage unit that stores information regarding pixels on which the halftone process is performed.
According to the above configuration, since information related to pixels on which halftone processing is performed is stored in the storage unit of the printing apparatus, even when used in cooperation with an information processing apparatus that transfers the information to the printing apparatus. Halftone processing can be performed on the printing apparatus side. Therefore, the calculation capacity (storage capacity) of the information processing apparatus can be reduced.

  An image processing method that solves the above problem is an image processing method of a printing apparatus that prints an image on a medium, and divides the image in the width direction of the image and arranges the divided images in the width direction. A halftone process for performing a halftone process from an image on one side in the width direction to an image on the other side of the divided image based on a basic dither mask; and An offset amount calculating step of calculating an offset amount that is a difference in the width direction between a boundary of the image and a basic dither mask that straddles the boundary, and in the halftone processing step, the one side of the divided image The reflected dither in which the basic dither mask is used for the image of the image and the offset amount is reflected in the basic dither mask for the image on the other side of the divided image. Disk is used.

  According to the above method, in the halftone processing step, halftone processing using a basic dither mask is performed on one image of the divided images, and the other image of the divided images is fundamentally processed. Halftone processing is performed using a reflection dither mask in which the offset amount is reflected in the dither mask. For this reason, since a common basic dither mask and a common reflection dither mask are used for each divided image, each time the basic dither mask and the reflection dither mask are arranged in the direction orthogonal to the width direction in the image, the basic dither mask is used. There is no need to set the halftone process start position and mask table for each of the dither mask and the reflected dither mask. Therefore, it is not necessary to transfer the start position of the halftone process and the mask table to a processing apparatus for performing the halftone process every time the basic dither mask and the reflected dither mask are set. It can suppress that the processing time of a process becomes long.

In the image processing method, it is preferable that the printing apparatus calculates the offset amount for each color of liquid ejected on the medium in the offset amount calculation step.
According to the above method, it is possible to set the start position of the halftone processing of the divided image in the basic dither mask and the reflected dither mask for each liquid color, thereby suppressing deterioration in image quality accuracy for each liquid color. can do.

1 is a schematic configuration diagram of an ink jet printer according to an embodiment. 6 is a flowchart illustrating a processing procedure of image processing executed by the printer. The schematic diagram of the image data which shows the process direction of the smoothing process in the state where the image is not divided | segmented. The schematic diagram which shows an example of a halftone process. The schematic diagram of image data which shows arrangement | positioning of the dither mask with respect to the image data of the state in which the image is not divided | segmented. The flowchart which shows the process sequence of a division | segmentation smoothing process. (A)-(c) is a schematic diagram of the image data which shows the processing content of a division | segmentation smoothing process. The schematic diagram of the image data which shows the order of the process of the unit image data of a division | segmentation smoothing process. The flowchart which shows the process sequence of a division | segmentation halftone process. The schematic diagram of image data which shows arrangement | positioning of the basic dither mask with respect to the image data in the state where the image was divided | segmented. The schematic diagram of the image data for description of creation of a reflection dither mask. The schematic diagram of the image data for description of creation of the 1st dither mask and the 2nd dither mask. The schematic diagram of the image data which shows arrangement | positioning of the basic dither mask in the division | segmentation halftone process of a modification. (A) And (b) is the schematic diagram of the image data which shows arrangement | positioning of the dither mask with respect to the image data of the state in which the image is not divided | segmented in the conventional printer.

Hereinafter, an embodiment in which a printing apparatus is embodied in an ink jet printer will be described with reference to the drawings.
As shown in FIG. 1, an ink jet printer (hereinafter “printer 11”) as an example of a printing apparatus includes a transport device 12 that transports a continuous sheet P of a long sheet that is an example of a medium, and a transport device 12. And a printing unit 13 that performs printing by ejecting ink (liquid) onto the continuous paper P conveyed by the printer. The printer 11 includes a control device 30 that controls the transport device 12 and the printing unit 13, and four cartridges 14 that supply ink to the printing unit 13.

  The transport device 12 includes a feeding unit 15 that feeds the continuous paper P, and a winding unit 17 that winds the continuous paper P fed from the feeding unit 15 and printed by the printing unit 13. That is, in FIG. 1, the feeding unit 15 is arranged at the left side which is the upstream side in the transport direction Y (hereinafter also referred to as “sub-scanning direction Y” in FIG. 1) in the continuous paper P, while the downstream side The winding unit 17 is disposed at the right side position. In the sub-scanning direction Y, the upstream side in the transport direction Y is “rear side”, and the downstream side in the transport direction Y is “front side”.

  The printing unit 13 is disposed at a position between the feeding unit 15 and the winding unit 17 so as to face the conveyance path of the continuous paper P. A plurality of nozzles 13 a for ejecting ink onto the continuous paper P are formed on the surface of the printing unit 13 that faces the transport path of the continuous paper P.

  Further, a support member 19 that supports the continuous paper P is disposed at a position facing the printing unit 13 across the conveyance path of the continuous paper P. A surface of the support member 19 that faces the printing unit 13 is a horizontal support surface 19a that supports the continuous paper P being conveyed.

  The four cartridges 14 contain different types of inks of cyan (C), magenta (M), yellow (Y), and black (K). These cartridges 14 are connected to the printing unit 13 via four supply paths 14a. The ink in the cartridge 14 is supplied to the printing unit 13 by a supply pump (not shown).

  The feeding unit 15 feeds in the width direction X of the continuous paper P (hereinafter also referred to as “main scanning direction X”, the direction orthogonal to the paper surface in FIG. 1), which is a direction orthogonal to the transport direction Y of the continuous paper P. The shaft 16 is provided so as to be rotationally driven. A continuous paper P is supported on the feeding shaft 16 so as to be integrally rotatable with the feeding shaft 16 in a state where the continuous paper P is wound in a roll shape in advance. Then, when the feeding shaft 16 is driven to rotate, the continuous paper P is fed from the feeding shaft 16 toward the downstream side of the transport path.

  A first relay roller 20 for winding the continuous paper P fed from the feeding shaft 16 and guiding it to the printing unit 13 side is disposed rotatably and obliquely above the feeding shaft 16. On the downstream side of the first relay roller 20 in the transport path of the continuous paper P, a pair of paper feed rollers 21 that are driven to rotate and are guided to the support surface 19a while sandwiching the continuous paper P transported from the first relay roller 20 side. Is arranged.

  On the downstream side of the support surface 19a in the conveyance path of the continuous paper P, the continuous paper P is sandwiched from the support surface 19a to the downstream side of the conveyance path of the continuous paper P by rotating the rotation. A pair of paper discharge rollers 22 is arranged to guide it. The second relay roller 23 for winding the continuous paper P conveyed from the discharge roller pair 22 side and guiding it to the take-up unit 17 is rotatable on the downstream side of the discharge roller pair 22 in the conveyance path of the continuous paper P. Is arranged. The winding unit 17 is located obliquely below and to the right of the second relay roller 23.

  A winding shaft 18 extending in the width direction X of the continuous paper P is provided in the winding unit 17 so as to be rotatable. Then, when the winding shaft 18 is rotationally driven, the printed continuous paper P conveyed from the second relay roller 23 side is sequentially wound by the winding shaft 18.

  The control device 30 is a CPU 40, a ROM 31, a RAM 32, and a nonvolatile memory, and includes an EEPROM 33, a communication unit 35, and a printer control unit 36 as an example of a storage unit. The CPU 40, ROM 31, RAM 32, EEPROM 33, communication unit 35, and printer control unit 36 are connected to each other through a bus 37.

  The CPU 40 performs image processing necessary for print control by executing a program stored in the ROM 31. This image processing includes, for example, color conversion processing, smoothing processing, halftone processing, and rasterization processing.

  The RAM 32 temporarily stores calculation results of the CPU 40 and other data. A basic dither mask 34 is stored in the EEPROM 33. The basic dither mask 34 is used for halftone processing, and is composed of a mask table having a plurality of different threshold values. The basic dither mask 34 has a pixel size of M (M is a natural number) in the main scanning direction X and L (L is a natural number) in the sub-scanning direction Y (see FIG. 4). The basic dither mask 34 has a different pixel size and mask table for each color.

  The communication unit 35 receives image data for printing generated by the image generation apparatus 100 configured by an information processing apparatus such as a personal computer. Then, the communication unit 35 transmits image data to the CPU 40.

  The CPU 40 includes a color conversion unit 41, a width calculation unit 42, a division unit 43, a smoothing processing unit 44, a synthesis unit 45, an offset amount calculation unit 46, and a halftone processing unit 47 as functional parts respectively realized by software (program). And a rasterization processing unit 48.

  The color conversion unit 41 receives the image data transmitted from the communication unit 35. The received image data is RGB image data including three color components of red (R), green (G), and blue (B). The color conversion unit 41 performs color conversion processing on the RGB image data. Color conversion processing is the gradation value of each color of cyan (C), magenta (M), yellow (Y), and black (K) that uses image data composed of R, G, and B gradation values in the printer 11. This is a process of converting the data into CMYK image data. Such processing is performed with reference to a color conversion table (lookup table) (not shown). The color conversion table is conversion table data used to express a color expressed by a combination of R, G, and B gradation values by a combination of C, M, Y, and K gradation values. . The CMYK image data is expressed as data having 256 gradation values for each color. In the following description, image data represents image data after color conversion processing.

The width calculation unit 42 calculates the number of pixels in the width direction X of the image data, that is, the main scanning direction X of the image data.
The dividing unit 43 divides the image data in the main scanning direction X of the image data. The dividing unit 43 sets the number by which the image data is divided according to the number of pixels in the main scanning direction X of the image data calculated by the width calculating unit 42. In the following description, the image data divided in the main scanning direction X is also referred to as “divided image data”.

  The smoothing processing unit 44 receives the image data, and smoothes the density of the image data using a smoothing matrix (smoothing filter). As an example of the smoothing filter, a median filter that uses the median density of the peripheral pixels of the pixel of interest as the density of the pixel of interest can be used.

  The smoothing processing unit 44 performs a smoothing process on each color of the image data individually. Further, in the smoothing process of the image data of each color, the smoothing processing unit 44 divides the image data into a plurality of pieces in the sub-scanning direction Y, and performs the smoothing process using the divided image data as one processing unit. In the following description, image data divided in the sub-scanning direction Y as one processing unit is also referred to as “unit image data”.

The synthesizing unit 45 synthesizes the divided image data after the smoothing process when the smoothing process is performed on the divided image data by the dividing unit 43.
When the halftone process is performed on the divided image data, the offset amount calculation unit 46 calculates an offset amount Qx (see FIG. 10) of the basic dither mask 34 for the divided image data in the main scanning direction X. The offset amount Qx includes a boundary BD (see FIG. 10) of the divided image data adjacent in the main scanning direction X and a basic dither mask 34 adjacent to the boundary in the main scanning direction X. And the distance. The offset amount calculation unit 46 calculates the offset amount Qx for each of C, M, Y, and K colors.

  The halftone processing unit 47 performs halftone processing on the undivided image data using the basic dither mask 34, and the reflected dither mask 34a reflecting the offset amount Qx on the basic dither mask 34 on the divided image data. (See FIG. 11) is used together to perform halftone processing. The halftone process is a process for converting the gradation of image data of 256 gradations into image data of two gradations for printing. The two-tone image data is dot data composed of pixels that form dots and pixels that do not form dots for each color ink dot.

  The halftone processing unit 47 individually performs halftone processing for each color of the image data (divided image data). The halftone processing unit 47 performs halftone processing for each unit image data.

  The rasterization processing unit 48 receives the dot data from the halftone processing unit 47 and performs interlace processing. The interlacing process is a process of rearranging dot data in an order to be transferred to the printer control unit 36 in consideration of the dot formation order. Thereafter, the image data subjected to the interlace processing is output to the printer control unit 36.

  The printer control unit 36 reads the image data that has been interlaced by the rasterization processing unit 48 and controls the transport device 12 and the printing unit 13 based on the image data.

  Next, a processing procedure of image processing executed by the CPU 40 will be described with reference to FIGS. In the following description with reference to FIGS. 2 to 12, each component of the printer 11 denoted by a reference numeral represents each component of the printer 11 described in FIG. 1.

  As shown in FIG. 2, the CPU 40 calculates the number of pixels in the width direction X (main scanning direction X) of the color-converted image data in step S10, and in step S20, the CPU 40 calculates the width direction X of the image data (main It is determined whether the number of pixels in the scanning direction X) is equal to or greater than a threshold value. This threshold is an upper limit value of the line memory that can be held by the CPU 40, and is determined by the specifications of the printer 11.

  Further, the number of pixels in the main scanning direction X of the image data varies depending on the print mode of the printer 11. Specifically, when a high-resolution print mode with high print quality is selected, the number of pixels in the main scanning direction X of the image data increases, and when a low-resolution print mode with low print quality is selected, the image The number of pixels in the main scanning direction X of data is reduced.

  Then, when the number of pixels in the main scanning direction X of the image data is less than the threshold value (step S20: NO), the CPU 40 performs the smoothing process without dividing the image data in the main scanning direction X in step S30 (normal smoothing process). ). Thereafter, the CPU 40 performs halftone processing in a state where the image data is not divided in the main scanning direction X in step S40 (normal halftone processing).

The normal smoothing processing method will be described with reference to FIG. The following description is common to all the colors of the image data.
The CPU 40 performs a smoothing process on the image data for each unit image data. The smoothing process is sequentially performed in the main scanning direction X from the left end of the image data Dc1, which is the unit image data in the first row of the image data, as indicated by the dashed arrows in the figure. Then, when the smoothing process is completed to the right end of the image data Dc1, the CPU 40 sequentially processes from the left end of the image data Dc2, which is unit image data in the second row of the image data, to the right end in the main scanning direction X. Hereinafter, such processing is repeatedly performed over the entire image data. Then, the CPU 40 ends the normal smoothing process when the smoothing process is similarly performed for all the colors of the image data.

  Next, a normal halftone processing method will be described with reference to FIGS. FIG. 4 shows only a part of cyan (C) pixel data in the image data for convenience of illustration. The following description applies to any of the other colors of the image data, and therefore, cyan (C) image data will be described as a representative example.

  As shown in FIG. 4, the CPU 40 compares the gradation value of each pixel, which is each pixel data of the image data, with the threshold value of the mask table of the basic dither mask 34. Then, the CPU 40 forms a dot when the gradation value of each pixel is larger than the threshold value of the corresponding mask table of the basic dither mask 34. On the other hand, when the gradation value of each pixel data is equal to or less than the threshold value of the corresponding mask table of the basic dither mask 34, the CPU 40 does not form a dot. In this way, the CPU 40 creates dot data that is two-tone image data.

  As shown in FIG. 5, the CPU 40 places a basic dither mask 34 on the image data. The basic dither mask 34 is shifted by a predetermined amount (hereinafter referred to as “shift amount Ms”) in the main scanning direction X with respect to the basic dither mask 34 adjacent in the sub scanning direction Y for the purpose of improving the print quality. . 4, the CPU 40 has been described with reference to FIG. 4 in order from the front end in the sub-scanning direction Y of the image data to the right end in the main scanning direction X from the left end in the main scanning direction X. Perform halftone processing. In this halftone process, for example, five unit image data are arranged in the sub-scanning direction Y with respect to one basic dither mask 34. After the halftone process is performed from the left end to the right end of the unit image data of 5 rows, the halftone process is performed on the next unit image data of 5 rows using the basic dither mask 34 adjacent in the sub-scanning direction Y. . With such a procedure, halftone processing is performed on the entire image data. Note that the shift amount Ms of the basic dither mask 34 adjacent in the sub-scanning direction Y is individually set for each color of image data.

  As shown in FIG. 2, when the number of pixels in the main scanning direction X of the image data is equal to or larger than the threshold value (step S20: YES), the CPU 40 sets the image data in the main scanning direction X as an example of a division process in step S50. To divide. And CPU40 performs a division | segmentation smoothing process in step S60, and after the division | segmentation smoothing process of step S60 is completed, it performs a division | segmentation halftone process in step S70.

  The detailed content of the division smoothing process will be described with reference to FIGS. In the following, a case where cyan (C) image data is divided into two in the main scanning direction X will be described as an example. Further, for convenience of description of the divided smoothing process, unit image data of the image data will be described.

  As shown in FIG. 7A, the unit image data is divided by the dividing unit 43 so that the first image data Ddc1 that is image data on the left side in the main scanning direction X and the image data that is image data on the right side in the main scanning direction X. Divided into two image data Ddc2.

  As shown in FIG. 6, in step S <b> 61, the CPU 40 adds an overlapping area Dovl to the second image data Ddc <b> 2 as an example of a setting process. Specifically, as shown in FIG. 7B, the CPU 40 extends the left end of the second image data Ddc2 in the main scanning direction X to the left (toward the first image data Ddc1), and has a predetermined number of pixels. The overlapping area Dovl formed by the above is added. This overlapping area Dovl has pixel data corresponding to the right end of the first image data Ddc1.

  As illustrated in FIG. 6, the CPU 40 performs a smoothing process on the second image data Ddc2 in step S62. This smoothing process is the same process as the above-described smoothing process, and is performed sequentially from the left end of the overlapping area Dovl to the right end of the second image data Ddc2 in the right direction.

  In step S63, the CPU 40 performs a smoothing process on the first image data Ddc1. Specifically, as shown in FIG. 7B, the CPU 40 performs the smoothing process on the first image data Ddc1 from the pixel on the opposite side (the left end side in the figure) from the second image data Ddc2. Next, in step S64, the CPU 40 synthesizes the first image data Ddc1 and the second image data Ddc2 as an example of a synthesis process. Specifically, the first image data Ddc1 is arranged so that the right end of the first image data Ddc1 after the smoothing process overlaps the overlapping area Dovl of the second image data Ddc2. At this time, as shown in FIG. 7C, the pixel data of the overlapping region Dovl is overwritten with the pixel data at the right end of the first image data Ddc1 after the smoothing process.

  As shown in FIG. 8, the CPU 40 performs the smoothing process in the order of the second image data Ddc2 and the first image data Ddc1, combines the first image data Ddc1 and the second image data Ddc2, and then in the sub-scanning direction Y. Transition to adjacent first image data Ddc1 and second image data Ddc2. Then, the CPU 40 performs smoothing processing in the order of the second image data Ddc2 and the first image data Ddc1, and synthesizes the first image data Ddc1 and the second image data Ddc2. Smoothing processing is performed over the entire image data in such processing order.

  As shown in FIG. 6, in step S65, the CPU 40 determines whether or not the division smoothing process has been completed for all unit image data of the image data. When the CPU 40 determines that the division smoothing process has not been completed for all the image data (step S65: NO), the CPU 40 proceeds to step S61 and performs the division smoothing process on the unit image data that has not been subjected to the division smoothing process. . On the other hand, when the CPU 40 determines that the division smoothing process has been completed for all unit image data of the image data (step S65: YES), the process ends.

  The CPU 40 similarly performs the division smoothing process for the image data of other colors, and when the division smoothing process is completed for the image data of all colors, the division smoothing process (see FIG. 2) in step S60 ends.

The detailed contents of the divided halftone process will be described with reference to FIGS.
As an example, a case where cyan (C) image data is divided into two in the main scanning direction X as in the case of the division smoothing process will be described.

  As shown in FIG. 9, in step S71, the CPU 40 calculates an offset amount Qx of the basic dither mask 34 in the main scanning direction X, and creates a reflected dither mask 34a (see FIG. 11) in consideration of this offset amount. . Next, in step S72, the CPU 40 calculates an offset amount Qy in the sub-scanning direction Y of the basic dither mask 34 in the last row, and creates a first dither mask 34b (see FIG. 12) corresponding to the offset amount Qy. . In step S73, the CPU 40 calculates an offset amount Qy in the sub-scanning direction Y of the reflected dither mask 34a in the last row, and creates a second dither mask 34c (see FIG. 12) corresponding to the offset amount Qy.

  As shown in FIG. 10, the offset amount Qy in the sub-scanning direction Y of the basic dither mask 34 indicates the difference between the rear end of the basic dither mask 34 in the last row and the rear end of the image data. The offset amount Qy in the sub-scanning direction Y of the reflected dither mask 34a indicates the difference between the rear end of the last row of the reflected dither mask 34a and the rear end of the image data. Further, the offset amount Qy of the basic dither mask 34 and the offset amount Qy of the reflection dither mask 34a are equal to each other. These offset amounts Qy have different values depending on the image data of other colors.

A method of creating the reflected dither mask 34a will be described.
As shown in FIG. 10, when the image data is divided into two in the main scanning direction X, the boundary BD (one-dot chain line in the figure) between the left divided image data and the right divided image data is adjacent to the main scanning direction X. The boundary BM of the matching basic dither mask 34 does not match.

  In this state, as shown in FIG. 11, the reflection dither mask 34a has a boundary BD between the left divided image data and the right divided image data, and the left end of the reflection dither mask 34a arranged in the main scanning direction X. Is created to match.

  The offset amount Qx of the basic dither mask 34 in the main scanning direction X is calculated as follows. That is, as shown in FIG. 10, the CPU 40 shifts Ms of the basic dither mask 34 used in the image data, and the basic dither mask arranged at the left end of the image data and the first line and the left end of the basic dither mask 34. An initial offset amount Qf that is a difference from the left end of 34 is acquired. The shift amount Ms and the initial offset amount Qf are stored in the ROM 31 in advance.

  Next, the CPU 40 sets an offset amount (hereinafter referred to as “reference”) from the boundary BD between the left divided image data and the right divided image data when the basic dither mask 34 is arranged without offset and shift with respect to the image data. An offset amount Qk ") is calculated. Specifically, the reference offset amount Qk is calculated by the remainder when the number of pixels in the main scanning direction X of the basic dither mask 34 is divided from the number of pixels in the main scanning direction X of the left divided image data.

  Next, the CPU 40 calculates an offset amount Qx in the main scanning direction X of the basic dither mask 34 in the first row based on the initial offset amount Qf and the reference offset amount Qk. Then, the CPU 40 reflects the offset amount Qx in the basic dither mask 34 that straddles the boundary BD between the left divided image data and the right divided image data in the basic dither mask 34 in the first row, thereby making the configuration shown in FIG. A reflection dither mask 34a as shown is created.

  A method of creating the first dither mask 34b and the second dither mask 34c will be described. Since the method of creating the dither masks 34b and 34c is the same, the method of creating the first dither mask 34b will be mainly described with reference to FIGS.

  The number N of lines of unit image data (number of pixels in the sub-scanning direction Y) input to the halftone processing unit 47 differs depending on the print mode. In particular, in the print mode in which the divided halftone process is performed, the number N of lines of unit image data is larger than in the print mode in which the normal halftone process is performed. For this reason, as shown in FIG. 10, the first image data Ddc1 in the last row (14th row) may straddle in the sub-scanning direction Y with respect to the basic dither mask 34 in the last row (5th row). For this reason, when halftone processing is performed only with the basic dither mask 34 and the reflected dither mask 34a, there is a possibility that the halftone processing is not performed on the rear end of the image data depending on the print mode.

  In this embodiment, the first dither mask is used as a dither mask corresponding to a portion where the first image data Ddc1 in the last row (14th row) straddles the sub-scanning direction Y with respect to the basic dither mask 34 in the last row (5th row). A mask 34b is created. Then, the halftone processing unit 47 performs halftone processing on the portion of the image data where the basic dither mask 34 is insufficient, using the first dither mask 34b.

  Also, as shown in FIG. 10, since the basic dither masks 34 arranged in the sub-scanning direction Y are shifted by the shift amount Ms in the main scanning direction X, the mask table of the first dither mask 34b has a predetermined basic dither mask. A mask table of two basic dither masks 34 adjacent to the mask 34 in the sub-scanning direction Y is used.

  Note that the second dither mask 34c is used as a dither mask corresponding to a portion where the second image data Ddc2 in the last row (14th row) straddles the sub-scanning direction Y with respect to the reflected dither mask 34a in the last row (5th row). create. Similarly to the basic dither mask 34, the reflection dither mask 34a is shifted by the shift amount Ms in the main scanning direction X when arranged in the sub-scanning direction Y, so that the mask table of the second dither mask 34c has a predetermined reflection. A mask table of two reflection dither masks 34a adjacent to the dither mask 34a in the sub-scanning direction Y is used.

  Then, as shown in FIG. 9, in step S74, the CPU 40 calculates the addresses of the basic dither mask 34 and the reflected dither mask 34a for processing the unit image data. The address of each dither mask 34, 34a indicates a position (pixel) at which halftone processing is started in the mask table of each dither mask 34, 34a.

  A method of calculating the addresses of the dither masks 34 and 34a will be described with reference to FIG. Since the calculation methods of the dither masks 34 and 34a are common, the calculation method of the basic dither mask 34 will be described as a representative.

  In principle, the position of the basic dither mask 34 at the left end in the main scanning direction X and the front end in the sub-scanning direction Y is the start position (address) of halftone processing in the basic dither mask 34. Then, the halftone processing address of the basic dither mask 34 is calculated for each unit image data.

  When unit image data is included in the basic dither mask 34, the number of rows of the basic dither mask 34 and the number of pixels in the sub-scanning direction Y of the basic dither mask 34 are divided from the cumulative number of lines of unit image data. The position of the unit image data in the sub-scanning direction Y in the basic dither mask 34 is calculated by the remainder of the division. In this case, the address of the basic dither mask 34 is the leftmost pixel of the basic dither mask 34 at the position of the unit image data in the sub-scanning direction Y in the basic dither mask 34.

  On the other hand, for example, when the first image data Ddc1 in the third row straddles the rear end of the basic dither mask 34 in the first row and the first column in the sub-scanning direction Y, the halftone process of the first image data Ddc1 is performed. The basic dither mask 34 in the second row and the first column and the basic dither mask 34 in the second row and the second column are used. When halftone processing is performed on the first image data Ddc1 on the fourth row, the basic dither mask on the second row is considered in consideration of the amount of the first dither mask 34 across the first image data Ddc1 on the third row and the shift amount Ms. 34 addresses are calculated.

  Based on such an idea, the CPU 40 calculates the number of extra lines Nb that is the number of lines of the first image data Ddc1 straddling the basic dither mask 34 and the number of rows of the basic dither mask 34. The number of extra lines Nb is a remainder obtained by dividing the number of pixels in the sub-scanning direction Y of the basic dither mask 34 by the value obtained by multiplying the number of lines of the first image data Ddc1 by the number of lines of the first image data Ddc1 across the basic dither mask 34. Is calculated as The number of rows of the basic dither mask 34 is calculated by dividing the number of pixels in the sub-scanning direction Y of the basic dither mask 34 from the cumulative value of the number of lines of the first image data Ddc1 subjected to the halftone process.

  Then, the CPU 40 multiplies the number of extra lines Nb by the number of pixels in the main scanning direction X of the basic dither mask 34 to offset the address of the basic dither mask 34 for the first image data Ddc1 across the basic dither mask 34. . Then, the CPU 40 calculates an address in the sub-scanning direction Y of the basic dither mask 34 at the start of processing of the first image data Ddc1 that is adjacent to the first image data Ddc1 straddling the basic dither mask 34 in the sub-scanning direction Y. Then, the CPU 40 multiplies the number of rows of the basic dither mask 34 by the shift amount Ms to calculate an address in the main scanning direction X of the basic dither mask 34 at the start of processing of the first image data Ddc1 at that time. For example, when the CPU 40 performs halftone processing on the first image data Ddc1 on the fourth row using the basic dither mask 34 on the second row, the address of the basic dither mask 34 is sub-scanned by the number of extra lines Nb. The point A in the figure moves in the direction Y and moves to the left by the shift amount Ms. That is, the sub-scanning direction Y of point A is the number of lines (Nb + 1) next to the number of extra lines Nb. Then, as shown in the figure, using the basic dither mask 34 in the second row, the halftone process of the first image data Ddc1 in the fourth row is performed using the point A as a reference.

  In step S75, the CPU 40 transfers the mask tables of the dither masks 34, 34a, 34b, and 34c, and the addresses of the basic dither mask 34 and the reflected dither mask 34a to the halftone processing unit 47, and in step S76, the half dither mask 34a and the reflecting dither mask 34a are addressed. Halftone processing is performed by the tone processing unit 47. Specifically, the CPU 40 uses the basic dither mask 34 to perform halftone processing from the left end to the right end of the first image data Ddc1 in the first row. Then, after the first image data Ddc1 in the first row is completed, the CPU 40 performs halftone processing from the left end to the right end of the second image data Ddc2 in the first row using the reflection dither mask 34a. When starting halftone processing for the first image data Ddc1 in the fourth row, the CPU 40 starts processing based on the set address of the basic dither mask 34 in the second row, and similarly, in the second row in the fourth row. When halftone processing is started for the image data Ddc2, processing is started based on the set address of the reflection dither mask 34a.

  In step S77, the CPU 40 determines whether halftone processing has been performed on all the lines of the image data. If the CPU 40 has not performed halftone processing on all the lines of the image data (step S77: NO), the CPU 40 proceeds to step S76 and continues the halftone processing. Further, when the halftone process is performed on all the lines of the image data (step S77: YES), the CPU 40 ends the divided halftone process for the cyan (C) image data.

  The CPU 40 similarly performs divided halftone processing on the image data of other colors. Specifically, the size of the basic dither mask 34, the shift amount Ms, and the initial offset amount Qf are different for each color. For this reason, the offset amounts Qx and Qy of the basic dither mask 34 are different for each color. Therefore, the basic dither mask 34, the reflected dither mask 34a, the first dither mask 34b, and the second dither mask 34c are created for each color. Then, halftone processing is performed using each of 34, 34a to 34c. Then, when the divided halftone process is completed for the image data of all colors, the CPU 40 ends the divided halftone process in step S70.

  Finally, in the image processing, as shown in FIG. 2, after completing one of the normal smoothing process and the normal halftone process, and the divided smoothing process and the divided halftone process, the CPU 40 performs the rasterization process in step S80. To end the process.

The operation of the printer 11 will be described.
First, the effect | action regarding a division | segmentation smoothing process is demonstrated.
For example, when the image data is divided in the main scanning direction X, if the smoothing process is performed only with the second image data Ddc2, the left end of the second image data Ddc2 reflects the image data at the right end of the first image data Ddc1. It will not be processed. For this reason, image continuity is lost at the boundary between the first image data Ddc1 and the second image data Ddc2.

  Therefore, in the present embodiment, the overlap area Dovl is added to the left end of the second image data Ddc2 in the divided smoothing process. This overlapping area Dovl corresponds to the image data of the left part including the right end of the left image data. For this reason, when performing the smoothing process on the left end image data of the second image data Ddc2 by performing the smoothing process from the overlapping area Dovl to the right side, the smoothing filter including the right end image data of the first image data Ddc1 Will be processed. Then, the continuity of the image at the boundary BD between the first image data Ddc1 and the second image data Ddc2 can be maintained by overwriting the overlapping area Dovl with the first image data Ddc1.

  By the way, when the second image data Ddc2 having such an overlapping area Dovl is set and the smoothing process is performed in the order of the first image data Ddc1 and the second image data Ddc2, the following problem occurs.

  That is, when the second image data Ddc2 is arranged to perform the smoothing process on the first image data Ddc1 that has been subjected to the smoothing process, the overlap area Dovl overlaps the right end of the first image data Ddc1, and thus the first image data Ddc1 The right end is overwritten on the overlapping area Dovl that has not been subjected to the smoothing process. For this reason, the image is not smoothed at the boundary between the first image data Ddc1 and the second image data Ddc2.

  In order to solve this problem, the second image data Ddc2 is copied to another processing area, smoothing processing is performed on the second image data Ddc2 in the processing area, the overlapping area Dovl is cut, and then the first image data A method of arranging in Ddc1 is conceivable. However, in this method, a dedicated processing area for performing the smoothing process on the second image data Ddc2 is required, and the second image data Ddc2 needs to be copied. And the processing time of the smoothing process becomes longer.

  In order to solve such a problem, in the present embodiment, after the smoothing process is performed on the second image data Ddc2, the smoothing process is performed on the first image data Ddc1, and the first image data Ddc1 and the second image data Ddc2 are synthesized. To do. By such a processing order, the right end of the first image data Ddc1 after the smoothing process is overlaid on the overlapping area Dovl, and the overlapping area Dovl is overwritten with the first image data Ddc1 after the smoothing process. For this reason, the smoothing process of the second image data Ddc2 is not performed in another processing area. That is, the smoothing process can be performed on the second image data Ddc2 in the same processing area as the first image data Ddc1.

Next, the operation related to the divided halftone process will be described.
If the boundary BD between the left divided image data and the right divided image data does not coincide with the boundary BM of the basic dither mask 34 adjacent in the main scanning direction X, the basic dither mask 34 is applied to the second image data Ddc2. If halftone processing is used, it is difficult to maintain the continuity of the dither mask. Therefore, in order to maintain the continuity of the dither mask, it is necessary to set the arrangement position of the basic dither mask 34.

  The basic dither mask 34 is set such that the position of the basic dither mask 34 is set so that a suitable dither mask is obtained at the current position and halftone processing can be started from the left front end of the basic dither mask 34. . The CPU 40 transfers the set basic dither mask 34 to the halftone processing unit 47. For this reason, since the information related to the basic dither mask 34 is transferred to the halftone processing unit 47 every time the basic dither mask 34 is set, the data transfer time becomes long and the image processing time becomes long.

  In order to solve such a problem, the inventor of the present application paid attention to the law of arrangement of the basic dither mask 34. That is, a dither mask (reflection dither mask) shifted to the right by an offset amount Qx that is a difference between the boundary BD between the left divided image data and the right divided image data and the left end of the basic dither mask 34 across the boundary. When 34a) is arranged in the main scanning direction X, the value of the mask table does not change from when the basic dither mask 34 is arranged in the main scanning direction X. Therefore, when halftone processing is performed on the left divided image data, the same halftone processing as when the basic dither mask 34 is arranged in the main scanning direction X is performed by arranging the reflection dither mask 34a in the main scanning direction X. It can be performed.

  Then, by transferring the mask table of each dither mask 34, 34a to 34c, and the addresses of the basic dither mask 34 and the reflected dither mask 34a to the halftone processing unit 47 before the halftone processing is started, the transfer time is obtained. Since this is before the start of image processing, an increase in processing time of image processing is suppressed.

  Then, by transferring each dither mask 34, 34a and its address to the halftone processing unit 47 before the halftone process is started, the transfer time is before the start of the image process. Is suppressed from becoming longer.

According to the printer 11 of the present embodiment, the following effects can be obtained.
(1) Since the smoothing process of the second image data Ddc2 including the overlapping region Dovl is performed in the divided smoothing process, the left end of the second image data Ddc2 reflects the right end image data of the first image data Ddc1. It becomes. Therefore, when the first image data Ddc1 is combined with the second image data Ddc2, it is possible to maintain image continuity at the boundary between the first image data Ddc1 and the second image data Ddc2.

  (2) In the divided smoothing process, the smoothing process is performed in the order of the second image data Ddc2 and the first image data Ddc1 in the unit image data of each row. Therefore, it is not necessary to perform the smoothing process on the second image data Ddc2 in another processing area, and the time for transferring the second image data Ddc2 in order to process the second image data Ddc2 in another processing area is omitted. Can do. Therefore, the processing time can be shortened. Further, since another processing area itself is not necessary, an increase in the capacity of the smoothing processing unit 44 can be suppressed.

  (3) In the divided halftone process, the mask table of each dither mask 34, 34a to 34c corresponding to the divided image data, and the addresses of the basic dither mask 34 and the reflected dither mask 34a before the start of the image processing are halftone processing units. 47, and halftone processing is performed based on these dither masks 34, 34a to 34c. For this reason, it is not necessary to set a dither mask for each divided image and for each row during execution of halftone processing, and therefore the dither mask mask table and address are transferred to the halftone processing unit 47 for each divided image and for each row. There is no need. Accordingly, the processing time for image processing is shortened.

  In particular, when image processing and print control are performed in parallel, if the processing time of the image processing is long due to the setting of the basic dither mask 34 during the image processing, it is difficult to appropriately print the image on the continuous paper P. In this regard, in this embodiment, since the processing time of the image processing is shortened by not setting the basic dither mask 34 during the image processing, the image can be appropriately printed on the continuous paper P.

  (4) Since the offset amount and address of the basic dither mask 34 are set for each ink type in the divided halftone process, the dither masks 34, 34a to 34c are created according to the ink type. Halftone processing can be performed using each dither mask 34, 34a to 34c appropriate for the type of ink. For this reason, it is possible to suppress deterioration in image quality.

  (5) Information related to the basic dither mask 34 is stored in the EEPROM 33. For this reason, even when the printer 11 is electrically connected to an information processing apparatus (image generation apparatus 100) such as a personal computer and used in cooperation, the printer 11 performs image processing and the image generation apparatus 100 side. Does not perform image processing. Therefore, an increase in calculation load due to image processing of the CPU and the memory of the image generation apparatus 100 is suppressed.

In addition, you may change the said embodiment into another embodiment as follows.
In the above embodiment, the number of images after the image data is divided by the dividing unit 43 may be three or more. In this case, it is preferable that the division smoothing process is performed from unit image data of third image data (not shown) which is the rightmost of the image data. In short, in the main scanning direction X of image data, it is preferable that the direction of the smoothing process and the order of the divided image data to be processed are opposite to each other. In this case, the divided halftone process creates a reflection dither mask for the third image data. The method of creating the reflection dither mask is the same as the method of creating the reflection dither mask 34a described above.

  In the image processing according to the above-described embodiment, the halftone processing may be processing for converting the gradation of CMYK image data of 256 gradations into image data of 4 gradations for printing. In this case, the dot data includes pixels that form large dots, pixels that form medium dots, pixels that form small dots, and pixels that do not form dots.

  In the image processing of the above embodiment, the basic dither mask 34 may be arranged differently from the arrangement of the basic dither mask 34 shown in FIG. For example, at least one of the initial offset amount Qf and the shift amount Ms may be changed. Further, at least one of the initial offset amount Qf and the shift amount Ms may be omitted. Since the offset amount Qx of the basic dither mask 34 is changed according to the change in the arrangement of the basic dither mask 34, the reflection dither mask 34a is changed.

  In the divided halftone processing of the image processing of the above embodiment, a dither mask 34d corresponding to the number N of lines of the first image data Ddc1 can be added to the rear end of the basic dither mask 34 as shown in FIG. . The mask table of the dither mask 34d corresponds to the number N of lines of the first image data Ddc1 from the front end of the mask table of the basic dither mask 34 adjacent in the sub-scanning direction Y, and the basic dither mask 34 considering the shift amount Ms. It corresponds to a mask table.

  According to this configuration, when the first image data Ddc1 in the third row crosses the boundary between the basic dither mask 34 in the first row and the second row, halftone processing is performed on the first image data Ddc1 by the dither mask 34d. The address of the basic dither mask 34 in the second row when the halftone process is performed on the first image data Ddc1 in the fourth row is the same as the sub-scanning direction Y in the remaining line Nb of the first image data Ddc1 in the third row. And a point B which is a position where the shift amount Ms is shifted in the main scanning direction X is set. When the number of remaining lines Nb of the first image data Ddc1 is different for each number of rows of the basic dither mask 34, the CPU 40 calculates the number of remaining lines Nb of the first image data Ddc1 with respect to the number of rows of the basic dither mask 34. Then, the CPU 40 sets an address for each number of rows of the basic dither mask 34 based on the number of extra lines Nb and the shift amount Ms. The addresses for the number of extra lines Nb and the number of rows of the basic dither mask 34 are transferred to the halftone processing unit 47 before the start of the halftone process (step S76). As for the reflected dither mask 34a, a dither mask corresponding to the number of lines of the second image data Ddc2 and considering the shift amount Ms can be added to the rear end of the reflected dither mask 34a in the same manner as the dither mask 34d.

In the image processing of the above embodiment, the smoothing process may be performed after the halftone process.
In the image processing of the above embodiment, the division smoothing process may be performed after the division halftone process.

-In the division | segmentation smoothing process of the said embodiment, a smoothing process can also be performed in order of 1st image data Ddc1 and 2nd image data Ddc2.
In the above embodiment, part of the image processing may be performed by the information processing apparatus (image generation apparatus 100).

In the image processing of the above embodiment, the smoothing process and the divided smoothing process can be omitted.
The printing apparatus may be a dot impact printer or a laser printer as long as it can print on a medium such as continuous paper. The printing apparatus is not limited to a printer having only a printing function, and may be a multifunction machine. Furthermore, the printing apparatus is not limited to a serial printer, and may be a line printer or a page printer.

  The medium is not limited to continuous paper, and may be a resin film, a metal foil, a metal film, a resin-metal composite film (laminate film), a woven fabric, a nonwoven fabric, a ceramic sheet, or the like.

  The state of the liquid ejected as a minute amount of liquid droplets from the printing unit 13 includes those that are granular, tear-like, or thread-like. The liquid here may be any material that can be ejected from the printing unit 13. For example, it may be in the state when the substance is in a liquid phase, and a liquid material having high or low viscosity, sol, gel water, other inorganic solvents, organic solvents, solutions, liquid materials such as liquid resins are used. Shall be included. Further, not only a liquid as one state of a substance but also a particle in which solid particles such as a pigment are dissolved, dispersed or mixed in a solvent is included. When the liquid is an ink, the ink includes various liquid compositions such as general water-based ink and oil-based ink, gel ink, and hot-melt ink.

  DESCRIPTION OF SYMBOLS 11 ... Printer as an example of a printing apparatus, 33 ... EEPROM as an example of a memory | storage part, 34 ... Basic dither mask, 34a ... Reflection dither mask, 43 ... Dividing part, 46 ... Offset amount calculation part, 47 ... Halftone processing part , 100... Image generation device as an example of information processing device, BD... Border of divided image, Qx... Offset amount, X .. width direction (main scanning direction)

Claims (5)

A printing apparatus for printing an image on a medium,
A dividing unit that divides the image in the width direction of the image and arranges the divided images in the width direction;
Based on a basic dither mask, a halftone processing unit that performs halftone processing from an image on one side in the width direction to an image on the other side in the divided image;
An offset amount calculation unit that calculates an offset amount that is a difference in the width direction between a boundary of the image after the division and a basic dither mask across the boundary;
The halftone processing unit
Using the basic dither mask for the one side image of the divided image,
A printing apparatus that uses a reflection dither mask that reflects the offset amount in the basic dither mask for the image on the other side of the divided images. The printing apparatus according to claim 1, wherein the offset amount calculation unit calculates the offset amount for each color of liquid ejected onto the medium. The printing apparatus according to claim 1, further comprising: a storage unit that stores information relating to a pixel on which the halftone process is performed. An image processing method for a printing apparatus for printing an image on a medium,
A dividing step of dividing the image in the width direction of the image and arranging the divided images in the width direction;
A halftone processing step of performing halftone processing from one image in the width direction of the divided image toward the other image based on a basic dither mask;
An offset amount calculation step of calculating an offset amount that is a difference in the width direction between the boundary of the image after the division and the basic dither mask straddling the boundary, and
In the halftone processing step, the basic dither mask is used for the image on one side of the divided image, and the offset to the basic dither mask for the image on the other side of the divided image. An image processing method that uses a reflected dither mask that reflects the amount. The image processing method according to claim 4, wherein the printing apparatus calculates the offset amount for each color of liquid ejected onto the medium in the offset amount calculation step.