JP2006247877A - Printing controlling apparatus, printing controlling method and printing controlling program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of the quality of an image in a case when a period using the same nozzle and a period of delivering and non-delivering coincide with each other. <P>SOLUTION: When a printing apparatus performing printing by delivering a recording material while scanning is performed by a plurality of nozzles, is controlled, a constitution comprises acquiring image data expressing the image by a plurality of pixels, determining a period of use for the same nozzle in the scanning, determining successively presence or absence of delivering on every pixel based on the image data, and printing the image according to the determined presence or absence of delivering. When the presence or absence of delivering is to be determined, the pixels for which the presence or absence of delivering has been determined are referred, and the presence or absence of delivering is determined so that such the pixel that indicates delivering of the recording material by a period with an integer multiple of the period of use, is not introduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a print control apparatus, a print control method, and a print control program.

When an image is printed in a printing apparatus that ejects ink using a plurality of nozzles, the presence or absence of recording of a recording material is usually determined for each pixel. In a normal printing device, the number of gradations that can be expressed by the presence or absence of a recording material is 2 to 4, so the number of gradations is converted for image data expressed in multiple gradations (for example, 256 gradations). Perform halftone processing. In this halftone process, in order to suppress the deterioration of image quality, a device for suppressing the generation of a periodic pattern has been made (for example, Patent Document 1).
JP 2003-283828 A

  In the prior art, further improvement has been desired in order to suppress deterioration in image quality due to recording a recording material in a periodic pattern. That is, when recording a recording material on a printing medium with a plurality of nozzles, by using the same nozzle for each of the plurality of pixels, the recording material of adjacent pixels in the two-dimensionally arranged pixels is The recording may be performed by different nozzles. According to this configuration, adjacent pixels are recorded by different nozzles, and the recording position deviation of the recording material that may occur for each nozzle can be made inconspicuous.

However, when the cycle in which the same nozzle is used matches the ejection and non-ejection cycles, the recording material may be recorded only by the same nozzle. In this case, the image quality is deteriorated.
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and provides a print control apparatus, a print control method, and a print control program capable of suppressing deterioration in image quality caused by periodically using the same nozzle. For the purpose of provision.

  In order to achieve the above object, according to the present invention, when determining the presence or absence of ejection from a nozzle, the recording material is ejected at a cycle that is an integral multiple of the use cycle of the same nozzle, with reference to the pixels for which ejection has already been determined. The presence or absence of discharge is determined so as not to occur. As a result, the use cycle of the same nozzle and the occurrence cycle of the presence / absence of ejection from the nozzle do not become the same cycle, and deterioration of image quality caused by periodically using the same nozzle can be suppressed. it can.

  For example, when there is a shift in the recording position of a recording material at a certain nozzle, if a large number of pixels are recorded using this nozzle, the positions of these pixels will shift with the same tendency, resulting in degradation of image quality. It becomes easy to be recognized as. However, if the presence / absence of ejection is determined so that the recording material is not ejected at a cycle that is an integral multiple of the above-described usage cycle, it will not be possible to continue recording a specific pattern using only the same nozzle, and deterioration in image quality will be recognized. Can be difficult. As a result, the image quality is improved.

  Here, in the printing apparatus, it is only necessary that the recording material can be recorded on the printing medium while scanning with a plurality of nozzles, and a plurality of nozzles are arranged in parallel in either the main scanning direction or the sub-scanning direction. However, in order to improve the printing speed, a configuration in which both are arranged in parallel is preferable. Of course, it is possible to adopt various configurations such as a configuration in which different nozzle arrays are configured for each color of the recording material and a plurality of nozzles are arranged in parallel in the sub-scanning direction for a common color. The main scanning direction is a direction substantially perpendicular to the print medium feeding direction, and the sub-scanning direction is a direction substantially parallel to the printing medium feeding direction.

  In image data, an image may be expressed by a plurality of pixels, and the color system and the number of gradations are not limited. That is, the image data acquired by the image data acquisition unit is not limited as long as it can be determined whether or not the recording material is ejected based on the image data. For example, it is possible to employ data representing gradation of the recording amount for each color of ink used in the printing apparatus. If a plurality of ink droplets can be ejected in the printing apparatus, it is possible to employ data that represents the gradation of the recording amount of each ink droplet.

  The nozzle cycle determining means only needs to be able to determine the use cycle of the same nozzle in the scanning. That is, when printing is performed by scanning in the printing apparatus, all pixels on the print medium can be filled while repeatedly using a limited number of nozzles. At this time, as described above, adjacent pixels are recorded by different nozzles. According to this configuration, the same nozzle is used for each of a plurality of pixels.

  For example, a configuration in which 2 to 4 adjacent pixels are recorded by different nozzles can be employed. If two adjacent pixels are recorded by different nozzles, different nozzles are assigned to the two adjacent pixels, and this assignment is repeated. As described above, if the allocation of nozzles and pixels is determined, the use cycle of the same nozzle is determined. Further, if the allocation of nozzles and pixels is determined, it is determined that the same nozzle is used for each of a plurality of pixels, so that it may be considered that this allocation is determined by the nozzle cycle determination means.

  It should be noted that when determining the use cycle of the same nozzle, it is sufficient that at least the nozzles that record the recording material on adjacent pixels are determined not to be the same nozzle, and may be determined by various methods. it can. Of course, the nozzle cycle determining means may determine the use cycle for both the main scanning direction substantially perpendicular to the print medium feed direction and the sub-scan direction substantially parallel to the print medium feed direction. You may determine a use period about one side. That is, various scanning cycles can be employed according to the printing speed and image quality.

  The ejection determining means only needs to be able to sequentially determine the presence or absence of the ejection for each pixel based on the image data. That is, in the printing apparatus, an image is formed on the printing medium by recording and non-recording of the recording material. Therefore, the recording and non-recording are determined based on the image indicated by the image data, and the image is printed on the printing medium. Form. Of course, if a plurality of ink droplets can be ejected in the printing apparatus, it is determined whether or not to eject each amount of ink droplets.

  As an example, when the amount of the recording material is expressed in multiple gradations (for example, 256 gradations) for each color of the recording material in the image data, a half for determining whether or not the recording material is ejected from the gradation value. An example of performing tone processing is given. In this example, the presence or absence of the recording material may be determined by comparing a predetermined threshold value with the gradation value in the image data for each pixel. In any case, once the presence or absence of sequential ejection is determined for each pixel by the ejection determining means, data indicating the presence or absence of the ejection is held in a predetermined recording medium in order to perform printing based on this determination.

  Further, when the ejection determining means sequentially determines the presence / absence of ejection for each pixel, this history, that is, the pixels for which ejection has already been determined is referred to. As a result, it is possible to determine whether or not ejection is determined so as to coincide with an integral multiple of the use cycle of the same nozzle. If it is determined that they match, when determining the presence / absence of ejection for the subsequent pixels, the presence / absence of ejection is determined so that the appearance pattern of the presence / absence of ejection does not coincide with an integral multiple of the use cycle of the same nozzle. Since the use cycle of the same nozzle can be defined by the number of pixels as described above, when verifying the pattern of ejection presence / absence, the number of pixels corresponding to an integer multiple of the use cycle is verified. Refer to the history.

  In addition, image quality degradation caused by the same nozzle use cycle may occur due to the recording of the recording material by the same nozzle being performed in the same cycle as the nozzle use cycle. May occur due to the fact that the recording of the recording material is performed at a cycle that is an integral multiple of the nozzle usage cycle. Therefore, it is only necessary to select a value corresponding to an integral multiple of the period so as to suppress the deterioration of the image quality by preventing the occurrence of a periodic pattern in the pixel.

  When the presence / absence of ejection is determined for each pixel, the printing unit prints an image based on the presence / absence of ejection. Here, it is only necessary to perform printing, and various configurations can be employed. For example, if the printing control apparatus is a computer separate from the printing apparatus, data for performing printing may be output to the printing apparatus in accordance with the determined ejection. If the printing control apparatus is integrated with the printing apparatus, a mechanism for executing printing may be controlled in accordance with the determined presence / absence of ejection.

  In the ejection determining means, various configurations can be adopted as the configuration for determining the presence or absence of ejection so that pixels indicating ejection of the recording material do not appear in a cycle that is an integral multiple of the above-described usage cycle. For example, a pattern indicating the presence or absence of ejection may be determined in advance for the number of pixels corresponding to an integral multiple of the nozzle use cycle, and data indicating this pattern may be stored in a predetermined recording medium. According to this configuration, it is possible to easily determine whether or not the periods coincide with each other by comparing the data regarding the presence or absence of ejection with the data.

  Furthermore, the data indicating this pattern may be recorded for the number of pixels corresponding to the period in the main scanning direction, or may be recorded for the number of pixels corresponding to the period in the sub-scanning direction. In the former, when the recording material is recorded using the same nozzles periodically along the main scanning direction, it is possible to suppress deterioration in image quality caused by this period. In the latter case, it is possible to suppress degradation of image quality caused by this cycle when recording a recording material by periodically using the same nozzle along the sub-scanning direction.

  In the ejection determination means, it is only necessary to determine whether or not ejection is performed so that pixels that indicate ejection of the recording material do not appear in a cycle that is an integral multiple of the above-described usage cycle, and various configurations can be employed. For example, the discharge determining means is configured to determine the presence / absence of the discharge by comparing a gradation value for each pixel with a predetermined threshold, and when the discharge cycle should be changed, the threshold is set in advance. What is necessary is just to comprise so that it may change into a value different from the decided value.

  That is, when comparing the threshold value with the gradation value for each pixel, the occurrence pattern of the presence / absence of ejection becomes a constant cycle and matches the use cycle of the same nozzle due to the predetermined threshold value. Even in this case, the appearance pattern can be changed by dynamically changing the threshold value. For example, a configuration may be adopted in which it is difficult to generate data indicating that ejection is performed with a larger threshold value, or data that indicates ejection is performed with a smaller threshold value. Of course, the gradation value to be compared with the threshold value may be the image data itself as in the dither method, or by assigning an error to the gradation value by error diffusion, the gradation value is different from the image data itself. May be. Further, it is not essential that the nozzle use cycle and the dot discharge cycle be completely inconsistent. If a part of the nozzle usage cycle and the dot ejection cycle can be made inconsistent, it is possible to prevent deterioration in image quality.

  Furthermore, the application target of the present invention may be applied to all pixels, but may be applied to pixels in which the effects of the present invention are remarkably exhibited. That is, image quality degradation caused by the use cycle of the same nozzle is easily noticeable when the recording amount of the recording material is small. Therefore, a range to which the present invention is applied is determined in advance, and when the gradation value in the image data is within a predetermined range, the presence / absence of ejection is determined with reference to the pixels for which ejection has already been determined. . With such a configuration, it is possible to effectively prevent deterioration in image quality through necessary and sufficient processing.

  Of course, a plurality of patterns having different numbers of pixels may be determined in advance, and the pattern may be changed according to the gradation value in the image data and compared with the history. With such a configuration, it is possible to compare a pattern with an appropriate number of pixels and a history, and to improve the processing speed.

  By the way, the above-described print control apparatus may be implemented alone, or may be implemented with other methods in a state of being incorporated in a certain device, and includes various aspects as an idea of the invention. However, it can be changed as appropriate. It can also be said that the invention exists in the procedure for determining the presence or absence of ejection based on the nozzle use cycle. Therefore, the present invention can also be applied as a method, and the same effect is achieved in the invention according to claim 8. When trying to implement the present invention, a computer may execute a predetermined program. Therefore, the present invention can also be applied as the program, and the same effect is achieved in the invention according to claim 9.

  Of course, it is also possible to make the structure described in claims 2 to 7 correspond to the above method and program. Any storage medium can be used to provide the program. For example, a magnetic recording medium or a magneto-optical recording medium may be used, and any recording medium that will be developed in the future can be considered in the same manner. In addition, even when a part is software and a part is realized by hardware, the idea of the present invention is not completely different, and a part is recorded on a recording medium and is appropriately changed as necessary. It includes a reading form. Furthermore, the same is true for the replication stage such as the primary replica and the secondary replica.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of print control apparatus:
(2) Print control processing:
(2-1) Halftone processing:
(3) Other embodiments:

(1) Configuration of print control apparatus:
FIG. 1 shows a schematic configuration of a print control apparatus according to an embodiment of the present invention. In the present embodiment, a print control apparatus is realized by a part of the functions of the computer 10. The computer 10 includes a CPU 11 that is the center of arithmetic processing, and the CPU 11 controls the entire computer 10 via a system bus 10a. Connected to the system bus 10a are a ROM 12, a RAM 13, a USB I / F 14, a hard disk drive (HDD) 15, a CRTI / F (not shown), an input device I / F, and the like.

  The hard disk drive 15 stores a program such as an operating system (OS) as software, and a program such as a printer driver (PRTDRV) 21 can be installed and stored as necessary. These software are appropriately transferred to the RAM 13 by the CPU 11 at the time of execution. The CPU 11 executes various programs under the control of the OS while appropriately accessing the RAM 13 as a temporary work area. For example, the processing can be advanced while temporarily storing data after halftone processing described later as the history buffer 13a.

  A keyboard 16 and a mouse 17 are connected to the input device I / F as operation input devices. A display 18 for display is connected to the CRTI / F. Therefore, the computer 10 can accept the operation contents by the keyboard 16 and the mouse 17 and can display various information on the display 18. Further, a printer 20 is connected to the USB I / F 14 and an image can be printed based on data output from the computer 10. Of course, the connection I / F with the printer 20 is not limited to the USB I / F, and various connection modes such as a parallel I / F, a serial I / F, and a SCSI connection can be adopted, and any one to be developed in the future. The same applies to the connection mode.

  The printer 20 used in the present embodiment is an ink jet printer, and forms an image on a print medium by ejecting ink with a large number of nozzles (for example, 180 nozzles for each ink color) mounted on the printer 20. . The computer 10 creates print data that can be interpreted by the printer 20 and outputs the print data via the USB I / F 14. The printer 20 prints an image by recording a recording material for each pixel constituting the image based on the print data.

  Further, in the present embodiment, the print control apparatus is configured by the computer 10, but the print control process according to the present invention can be implemented by the program execution environment installed in the printer 20, and the printer 20 is directly connected to the printer 20. The image data may be acquired from a digital camera or the like connected to the printer and the print control process may be performed. Of course, the print control process may be performed with a digital camera in the same configuration, and various other configurations such as performing the print control process according to the present invention by a distributed process may be employed. The print control processing according to the present invention may be performed in a so-called multi-function machine in which a scanner for capturing an image and a printer for printing an image are integrated.

(2) Print control processing:
The PRTDRV 21 can perform printing by performing predetermined processing on an image for which a print instruction has been issued from an application program (not shown). The PRTDRV 21 includes an image data acquisition module 21a, a color conversion module 21b, a correspondence relationship determination module 21c, a halftone processing module 21d, and a print data generation module 21e in order to execute printing. When the above-described print instruction is given, the PRTDRV 21 is driven, and the processing for the RGB image data 15a is performed by each module to generate print data. The generated print data is output to the printer 20 via the USB I / F 14, and the printer 20 executes printing based on the print data.

  FIG. 2 is a flowchart showing this print control processing. When the print instruction is issued, first, the image data acquisition module 21a acquires RGB image data 15a indicating an image for which a print instruction has been given by the application program (step S100). At this time, if there is an excess or deficiency in the number of pixels of the RGB image data 15a, resolution conversion processing is performed as appropriate in order to secure the pixels necessary for printing. In the present embodiment, the RGB image data 15a is data in which each color component of RGB (red, green, blue) is expressed in gradation to define the color of each pixel, and is 256 gradations in each color. In this embodiment, the RGB image data 15a expressing colors by RGB color components will be described as an example. However, various kinds of data such as JPEG image data adopting the YCbCr color system and image data adopting the CMYK color system are used. Can be used.

  The color conversion module 21b converts the color system indicating the color of each pixel (step S105). That is, the LUT (color conversion table) 15b stored in advance in the HDD 15 is appropriately referred to, and the data expressing the color in the RGB color system is converted into the data expressing the color in the CMY color system. Here, the number of color components in the CMY color system is not limited to 3, and the number of colors of ink mounted on the printer 20 is the number of color components. For example, when the printer 20 is loaded with each color ink of CMYKlclm (cyan, magenta, yellow, black, light cyan, light magenta), the color component of the CMY color system is CMYKlclm.

  The LUT 15b is a table that expresses colors by the RGB color system and the CMY color system, associates the two, and describes the correspondence between a plurality of colors. Accordingly, with respect to an arbitrary color expressed in the RGB color system, the CMY color system color corresponding to the arbitrary color can be obtained by interpolation calculation by referring to the surrounding RGB colors defined in the LUT 15b. And color conversion can be performed. Further, the CMY color system data is image data in which each color component of the CMY color system is expressed with a predetermined number of gradations (for example, 256 gradations), and each gradation value is represented by each pixel and each color. This corresponds to the recording rate (ratio of the number of dots recorded per unit area). In the present embodiment, the process of acquiring the image data in step S105 corresponds to the process of the image data acquisition unit in the above claims.

  When the color conversion is performed by the color conversion module 21b, the correspondence determination module 21c determines the correspondence between each pixel in the data after color conversion and the nozzle in the printer 20 (step S107). In the present embodiment, the correspondence between pixels and nozzles is determined in advance for each printing condition, and is recorded in the HDD 15 as nozzle number data 15c for each printing condition. Therefore, the correspondence determination module 21c acquires the necessary nozzle number data 15c according to the printing conditions when printing is performed by the PRTDRV 21.

  FIG. 3 is a diagram illustrating an example of the nozzle number data 15c. In the figure, small rectangles with numerical values correspond to pixels in the data after color conversion, and the horizontal direction on the paper surface is the main scanning direction and the vertical direction on the paper surface is the sub-scanning direction. The number in the rectangle is the nozzle number. In other words, each nozzle provided in the printer 20 is assigned a number in advance, and the correspondence between the pixel and the nozzle is defined by associating the nozzle number with each pixel.

  FIG. 3 shows an example in which numbers from 0 to 179 are assigned to 180 nozzles arranged in the sub-scanning direction. In this nozzle number data, nozzle numbers are associated with a plurality of pixels arranged in the main scanning and sub-scanning directions, and when ink is recorded for a larger number of pixels than these pixels, the nozzle number is recorded. The relationship defined in the data 15c is repeated periodically.

  For example, in FIG. 3, since the nozzle numbers are associated with four pixels arranged in the main scanning direction, the nozzles shown in FIG. 3 are repeatedly used if printing of five or more pixels is performed in the main scanning direction. . More specifically, ink is recorded by the 176, 86, 131, 41, 176, 86, 131, and 41 nozzles in order for the 8 pixels arranged in the main scanning direction. Therefore, the use cycle of the same nozzle in the main scanning direction is 4 pixels. In the example shown in FIG. 3, only a part of the correspondence relationship is shown in the sub-scanning direction, but the relationship defined in the nozzle number data 15c is repeated in the sub-scanning direction, and the use cycle of the same nozzle is defined by pixels. It is possible.

  The configuration as described above is employed to prevent ink from being recorded on adjacent pixels by the same nozzle, and to prevent deterioration in image quality that is affected by a recording position shift by individual nozzles. For example, assume that ink is recorded using nozzles of the same number for a certain raster lined up in the main scanning direction, and ink is printed by two different nozzles for two raster lines arranged in the sub-scanning direction.

  At this time, if an ink recording position shift occurs in either of the two nozzles, the ink recording positions of both nozzles shift with a certain tendency. In this case, the image quality is deteriorated, for example, a line parallel to the main scanning direction is generated. Therefore, the above-described deterioration in image quality is prevented by recording ink with different nozzles for pixels adjacent in the main scanning direction. Of course, it is possible to prevent image quality deterioration by recording ink with different nozzles for pixels arranged in the sub-scanning direction. In the present embodiment, the process of step S107 corresponds to the nozzle cycle determining means.

(2-1) Halftone processing:
When the correspondence relationship determination module 21c determines the correspondence relationship between the pixels and the nozzles, the halftone processing module 21d determines the gradation value of each pixel in the data after the color conversion based on the ink ejection / non-ejection (hereinafter referred to as the following). (Referred to as dot on / off) is converted into specified halftone image data (steps S110 to S175). In the present embodiment, halftone processing is performed by error diffusion processing. In this processing, halftone processed data is prevented from forming a constant pattern in the same cycle as the use cycle of the same nozzle.

  FIG. 4 is a diagram for explaining the halftone process. In the upper part of the figure, an example is shown in which the data after the halftone process has a constant pattern in the same cycle as the use cycle of the same nozzle. That is, the example shown at the top indicates a pixel after halftone processing by a rectangle, and “1” indicates dot-on and “0” indicates dot-off. This example shows an arrangement of dot on / off in a certain raster. As shown in the upper part of the figure, one out of four pixels is dot on, and the dot on appears periodically.

  In the present embodiment, since the cycle of using the same nozzle in the main scanning direction is 4 pixels as described above, when a dot-on appears in a cycle of 4 pixels as in the example shown in FIG. 4, a nozzle that forms a dot However, it becomes only the 176th nozzle. Therefore, when dot-on occurs in such a cycle, it is possible to prevent ink from being recorded on adjacent pixels by the same nozzle by associating the pixels with the nozzles by the nozzle number data 15c as described above. It will disappear. In other words, even though the configuration is such that four nozzles are used in the same raster, only one nozzle is actually used. Deterioration cannot be suppressed.

  Therefore, in this embodiment, halftone processing is performed so that the use cycle of the same nozzle does not coincide with the dot-on appearance cycle. The halftone process is a process for determining whether or not to discharge ink for each pixel by comparing a predetermined threshold value and the data after color conversion. In this embodiment, the threshold value is set as threshold data 15e. Recorded in advance in the HDD 15.

  Further, data for verifying whether the halftone processed data has a constant pattern in the same cycle as the use cycle of the same nozzle is recorded in the HDD 15 as the pattern data 15d, and the history verification unit 21d1 Performs this verification in steps S115 to S140. In the pattern data 15d, a pattern corresponding to a cycle in which the same nozzle is used in the nozzle number data 15c is defined in advance.

  That is, the use cycle of the same nozzle depends on the nozzle number data 15c. Since the nozzle number data 15c is defined for each printing condition, the pattern data 15d also corresponds to the nozzle number data 15c for each printing condition. Prepared. In the example shown in the upper part of FIG. 4, pattern data for four pixels corresponding to the dot-on cycle is prepared in order to prevent one pixel from being periodically dot-on in every four pixels. As shown in the lower part of 4, it is 4-bit data of “1000”.

  In the present embodiment, each pixel in the image data after color conversion is specified by coordinate variables X and Y, and halftone processing is sequentially performed on the gradation value P (X, Y) of each pixel for each color. carry out. In this embodiment, the pixel at the left corner is (X, Y) = (1, 1), and the coordinate variables X and Y are first initialized to 1, 1 (step S110). Further, as described above, the deterioration of image quality due to the appearance of dot-on at the same cycle as the usage cycle of the same nozzle is noticeable when only the same nozzle is used and no other nozzle is used. Therefore, in the present embodiment, the use of a specific one of the four nozzles used in the main scanning direction is prevented, and the gradation value indicated by the data after color conversion is a predetermined value. It is determined whether or not (a value corresponding to a recording rate of 25% in this example) or less (step S115).

  That is, in the present embodiment, since the pixel after color conversion is expressed with 256 gradations (0 to 255) for each color, the gradation value P (X, Y) is 255 · (25/100) or less. It is determined whether or not. In step S115, when it is determined that the gradation value is equal to or less than the predetermined value, processing for preventing the dot-on from appearing in the same cycle as the use cycle of the same nozzle is performed in and after step S120.

  For this purpose, first, the pattern data 15d corresponding to the printing conditions is acquired from the HDD 15 (step S120). Further, in this embodiment, data indicating ON / OFF for each pixel obtained after the halftone process is held in the history buffer 13a, which is predetermined data and is the nearest number of pixels corresponding to the use cycle. Data (hereinafter referred to as history data) is compared with the pattern data 15d. In the present embodiment, the logical product of the pattern data 15d and the history data is acquired (step S125).

  When the logical product is acquired, the logical sum of all bits in the logical product is further acquired (step S130). As a result, if any one of the values after the logical product is “1”, it is “1”, otherwise it is “0”. That is, it is possible to determine whether any one of the history data matches the pattern data by logical sum. Therefore, it is determined whether or not the logical sum is “1” (step S135). If it is determined that the logical sum is “1”, the threshold value value th used for error diffusion is set to a predetermined amount α. Increase (step S140). As a result, it is possible to make it difficult for dots to be turned on for the error diffusion target pixel. On the other hand, when it is not determined that the logical sum is “1”, step S140 is skipped. Then, an error diffusion process is performed in which the obtained threshold th is compared with the gradation value P (X, Y) to determine dot on / off of the coordinate variables X and Y (step S145). Note that the value of α may be set so as to make it difficult for dots to be turned on.

  That is, as shown in the middle part of FIG. 4, when a pixel corresponding to a broken-line rectangle is a target of halftone processing, pattern data 15d is obtained by taking a logical product of the history data of the latest four pixels and the pattern data prepared in advance. The logical product is “1” when the pixel that is “1” matches the pixel that is “1” in the history data. In the present embodiment, since the highest order bit of the pattern data is “1” and the subsequent 3 bits are “0” as described above, it is determined whether or not “1” is included in the logical product by logical sum. By determining, it can be determined whether or not the dot is on at the same cycle as the use cycle of the same nozzle.

  In the above processing, by adjusting the content of the pattern data 15d, it is possible to determine whether or not the history data having the number of pixels corresponding to the predetermined cycle includes pixels that match the predetermined pattern. . According to this process, a predetermined pattern can appear in a predetermined cycle, but of course, if it is determined whether or not dot-on appears in the same cycle as the use cycle of the same nozzle, the pattern A configuration may be adopted in which it is determined whether or not both the highest bit of data and the history data corresponding to the pixel are “1”. In the present embodiment, the processing in steps S110 to S145 corresponds to the processing in the discharge determination unit.

  When the error diffusion processing for the coordinate variables X and Y is finished by the above processing, whether or not the processing is finished up to the end in the X direction (the maximum value in the X direction in the data after color conversion) based on the coordinate variable X. (Step S150), and if it is not determined that the process has been completed up to the end in the X direction, the coordinate variable X is incremented (step S155), and the processes in and after step S115 are repeated. If it is determined in step S150 that the process has been completed up to the end in the X direction, it is determined whether or not the process has been completed up to the end in the Y direction (the maximum value in the Y direction in the data after color conversion) (step S160).

  Again, if it is not determined that the process has been completed up to the end in the Y direction, the coordinate variable Y is incremented (step S165), and the processes in and after step S115 are repeated. If it is determined in step S160 that the process has been completed up to the end in the Y direction, the error diffusion process for all pixels for a certain color has been completed, so the error diffusion process has been completed for all colors in the color-converted data. It is determined whether or not (step S170). If it is not determined in step S170 that error diffusion processing has been completed for all colors, the color to be processed is changed to an unprocessed color (step S175), and the processing from step S115 is repeated.

  If it is determined in step S175 that the error diffusion processing has been completed for all colors, the print data generation module 21e acquires data used in one main scan from the data subjected to the error diffusion processing, and the printer 20 sequentially. The printing process to be output to is performed (step S180). The printer 20 forms an image on the print medium based on this data. In the present embodiment, the process in step S180 corresponds to the process in the printing unit. As described above, halftone processing is performed for each pixel, and past history data is referred to at this time, but the number of pixels in the history data reaches the number of pixels corresponding to the use cycle of the same nozzle. If not, the deficient number of pixels may be supplemented with dummy data (eg, “0”).

  In the above processing, since it is possible to prevent the dot-on from occurring at the same cycle as the use cycle of the same nozzle, it is possible to prevent image quality deterioration due to the dot-on continuing at the same cycle as the use cycle of the same nozzle. Can do. Therefore, when the configuration in which the pixels adjacent in the main scanning direction are recorded with a plurality of nozzles as described above, the effect of preventing image quality degradation due to the plurality of nozzles can be surely exhibited.

  In the halftone process, it is easy to generate a situation in which dot-on continues for a certain period for various reasons. For example, when error diffusion processing is performed, processing for distributing an error between a threshold value and a gradation value to other pixels is performed. At this time, one or more processing for comparing the threshold value and the gradation value is not performed. The error is distributed to the pixel. Therefore, a pixel in which an error is likely to be accumulated can occur depending on the order in which the error diffusion processing is performed. As a result, a situation in which dot-on continues in a certain cycle is likely to occur. If this period is the same period as the use period of the same nozzle, the image quality is likely to be deteriorated. However, according to the present invention, it is possible to prevent the dot-on from continuing in this period. It can be effectively suppressed.

  Of course, various methods can be used for error distribution in the error diffusion process, and the error between the threshold value and the gradation value can be multiplied by a predetermined coefficient and distributed to one or more pixels. is there. Moreover, the structure which performs error diffusion processing collectively about several pixels may be sufficient. For example, four pixels, each consisting of two pixels in the vertical and horizontal directions, are used as one block, the block is used as a unit, compared with a predetermined threshold value, and ON / OFF of the pixels in the entire block is determined according to the conditions. The processing may be a combination of processing for determining on / off for each time. Even in this case, the appearance of dot-on is likely to occur in a certain cycle, and the present invention has the effect of preventing image quality deterioration as long as this cycle matches the use cycle of the same nozzle. Further, if the frequency of use of the nozzles becomes too low, the amount of ink ejected from each nozzle may not be stable. However, according to the present invention, it is possible to prevent only specific nozzles from being used. The amount of ejected ink is stabilized, contributing to image quality improvement.

  Further, by combining the present invention with a technique for preventing the generation of periodic dots as in the prior art described above, it becomes possible to prevent image quality deterioration more reliably. FIG. 5 is a diagram showing this state. In the figure, an example in which the dot on / off is not corrected is shown in the upper part. Further, an example in which a period of three pixels in the main scanning direction, that is, the same raster is recorded by three different nozzles is shown as an example. In this example, when processing for preventing the occurrence of dots with a period of two pixels in the main scanning direction is performed by the conventional technique or the like, as shown in the upper part of FIG. Because of the delay, the third pixel from the left is dot off, and the fourth pixel from the left is dot on.

  When processing is performed in this way, the first pixel is dot-on and the fourth pixel is dot-on, which coincides with the use cycle of the same nozzle in this example. Therefore, if the history data is acquired for three pixels and the process of the present invention is performed with the pattern data set to “100”, it is possible to prevent the dot-on from continuing in the same cycle as the use cycle of the same nozzle. Can be prevented. That is, in order to reliably prevent image quality deterioration, it is extremely important to take measures to prevent the image quality deterioration for each cause.

(3) Other embodiments:
The above embodiment is an example constituting the present invention, and various configurations are adopted as long as it is possible to prevent pixels indicating ejection of the recording material from appearing with an integer multiple of the use cycle of the same nozzle as the cycle. Is possible. For example, the pattern data 15d is not limited to “1000”. That is, in the above-described embodiment, “1000” is used to prevent image quality deterioration at a recording rate of 25% or less. However, pattern data of 8 is used to prevent image quality deterioration at a recording rate of 12.5% or less. Data in which one of the pixels is turned on, for example, “10000000” may be employed.

  That is, the pattern data 15d is prepared in a number corresponding to the number of pixels that is an integral multiple of the use cycle of the same nozzle, and the appearance cycle of “1” indicating dot-on in this pattern data is also the same as the use cycle of the same nozzle. It may be an integer multiple. Therefore, in addition, the pattern data “100010000000” when the recording rate is 16.7% or less, the pattern data “100010001000” when the recording rate is 25% or less, the pattern data “1000100000000” when the recording rate is 12.5% or less, and the recording rate 8. Various pattern data can be applied, such as applying pattern data “100000000000000” at 3% or less, and pattern data “1000000000000000” at a recording rate of 6.25% or less.

  Of course, at this time, the number of pixels acquired as history data is the same as the number of pixels in the pattern data 15d. If the number of pixels in the pattern data is small, the processes in steps S125 and S130 can be performed at high speed. On the other hand, if the recording rate is limited, it is possible to increase the speed in the sense that there are few application targets of the verification processing in the present invention.

  Furthermore, the use cycle of the same nozzle is not limited to 4 pixels or 3 pixels as described above, and the cycle of the pattern data 15d may be set according to the cycle defined by the nozzle number data 15c. For example, when the use cycle of the same nozzle is 2 pixels, various pattern data such as pattern data “10”, “101010”, etc. can be applied to a recording rate of 25% or less.

  Further, the nozzle number data 15c may be prepared in advance as described above, or may be created by the correspondence determination module 21c according to the printing conditions. Further, in the above-described embodiment, the dot-on arrangement is corrected based on the history data for all the ink color nozzles. However, of course, the color in which the image quality is significantly deteriorated (for example, only K, only CMY, etc.). The present invention may be applied to other inks, and other inks may not be corrected.

  Furthermore, in the above embodiment, it is assumed that the amount of ink ejected from each nozzle is the same ink amount, but the configuration is such that the amount of ink ejected from the nozzle can be adjusted in a plurality of stages. The present invention may be applied when determining whether dots are on or off. In this case, the gradation value for each color may be converted into a gradation value corresponding to the ink recording rate at each stage in step S105 in FIG. 2, and the processing after step S107 may be performed for each stage.

  Further, as described above, since the same nozzle is periodically used in the sub-scanning direction, the same processing may be performed for the period in the sub-scanning direction. Furthermore, the present invention may be applied in order to prevent dots from appearing in the same cycle as the use cycle of the same nozzle in processing other than error diffusion processing, for example, dither processing.

FIG. 2 is a block diagram illustrating a schematic configuration of a print control apparatus. 6 is a flowchart illustrating print control processing. It is a figure which shows the example of nozzle number data. It is a figure explaining a halftone process. It is a figure explaining a mode that degradation of image quality is prevented.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... CPU, 12 ... ROM, 13 ... RAM, 13a ... History buffer, 15 ... Hard disk drive, 15a ... RGB image data, 15b ... LUT, 15c ... Nozzle number data, 15d ... Pattern data, 15e ... Threshold Data, 20 ... Printer, 21a ... RGB image data acquisition module, 21b ... Color conversion module, 21c ... Correspondence determination module, 21d ... Halftone processing module, 21e ... Print data generation module

Claims (9)

A printing control apparatus that controls a printing apparatus that performs printing by ejecting a recording material while scanning with a plurality of nozzles,
Image data acquisition means for acquiring image data representing an image by a plurality of pixels;
Nozzle period determining means for determining a use period of the same nozzle in the scanning;
Discharge determining means for sequentially determining the presence or absence of the discharge for each pixel based on the image data;
Printing means for printing an image according to the determined presence or absence of ejection,
The ejection determining means refers to a pixel for which ejection has already been determined, and determines whether ejection has occurred so that a pixel indicating ejection of a recording material does not appear in a cycle that is an integral multiple of the use cycle. Print control device. The nozzle period determining means determines a use period of the same nozzle in a main scanning direction substantially perpendicular to the print medium feeding direction and a sub-scanning direction substantially parallel to the printing medium feeding direction. The printing control apparatus according to 1. The ejection determining means includes a pattern in which the presence / absence of ejection is determined in advance for the number of pixels corresponding to the period in the main scanning direction and the pixels in which the presence / absence of ejection has already been determined. The print control apparatus according to claim 1, wherein the print control apparatuses are compared. The ejection determining means includes a pattern in which the presence / absence of ejection is determined in advance for the number of pixels corresponding to the period in the sub-scanning direction, and pixels for which ejection has already been determined. The print control apparatus according to claim 1, wherein comparison is performed. The ejection determining means determines the presence / absence of the ejection by comparing a gradation value for each pixel with a predetermined threshold, and a pixel indicating ejection of the recording material does not appear in a cycle that is an integral multiple of the usage cycle. The print control apparatus according to any one of claims 1 to 4, wherein the threshold value is changed to a value different from a predetermined value when determining whether or not to discharge. The discharge determining means determines whether or not to discharge with reference to the pixels for which discharge has already been determined when a gradation value in the image data is within a predetermined range. The printing control apparatus according to any one of claims 1 to 5. The print control apparatus according to any one of claims 3 to 6, wherein the number of pixels of the pattern is determined in advance by a gradation value in the image data. A printing control method for controlling a printing apparatus that performs printing by discharging a recording material while scanning with a plurality of nozzles,
An image data acquisition step of acquiring image data representing an image by a plurality of pixels;
A nozzle cycle determining step for determining a use cycle of the same nozzle in the scan;
A discharge determination step of sequentially determining the presence or absence of the discharge for each pixel based on the image data;
A printing process for printing an image according to the determined presence or absence of ejection,
In the ejection determination step, the presence or absence of ejection is determined with reference to pixels for which ejection has already been determined, so that pixels that indicate ejection of the recording material do not appear in a cycle that is an integral multiple of the use cycle. Print control method. A printing control program for controlling a printing apparatus that performs printing by discharging a recording material while scanning with a plurality of nozzles,
An image data acquisition function for acquiring image data representing an image by a plurality of pixels;
A nozzle cycle determination function for determining the use cycle of the same nozzle in the scan;
A discharge determination function for sequentially determining the presence or absence of the discharge for each pixel based on the image data;
The computer realizes a printing function that prints an image according to the determined presence or absence of ejection,
The discharge determining function refers to pixels that have already been determined whether or not to discharge, and determines whether or not to discharge so that pixels that indicate discharge of a recording material do not appear in a cycle that is an integral multiple of the use cycle. Print control program.

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