JP4590211B2 - Image processing apparatus, image processing method, and program - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method, and more specifically, a recording head in which each color nozzle row corresponding to each of a plurality of color inks is arranged in a predetermined direction is reciprocated on a recording medium in the predetermined direction. The present invention relates to image processing when generating recording data used in an inkjet recording apparatus that performs recording by scanning.

  For example, as information output devices in word processors, personal computers, facsimiles, and the like, printers that record desired information such as characters and images on a sheet-like recording medium such as paper or film are widely used.

  Various types of recording methods are known for printers, but inkjet methods have recently been used for reasons such as non-contact recording on recording media such as paper, easy colorization, and high quietness. A serial recording method in which recording is performed while reciprocally scanning a recording head that ejects ink according to desired recording information in a direction that intersects with the conveyance direction of a recording medium such as paper. However, it is generally widely used because it is inexpensive and easy to downsize.

  When performing color recording with such a serial type ink jet printer, a recording head corresponding to the number of colors of the ink to be used is mounted on the carriage, and a plurality of ink droplets ejected from each color recording head are used on the recording medium. Configure the pixel.

  In a printer that scans in both directions in a reciprocating manner with a plurality of recording heads arranged in the scanning direction and mounted on the carriage, the ink overlap order differs between forward scanning and backward scanning, The color may be different.

In order to solve this problem, a method has been proposed in which two recording heads are symmetrically provided on a carriage for the same color so that the order of ink ejected in both directions is the same (for example, patents). Reference 1).
Japanese Patent Laid-Open No. 08-295034

  However, if two recording heads are provided symmetrically for the same color in the carriage, the carriage becomes heavier and larger, the apparatus size and head cost increase, and vibration and noise during scanning also increase. End up.

  The present invention has been made in view of the above circumstances, and provides an image processing method and an image processing apparatus that reduce the difference in color between forward scanning and backward scanning without increasing the size and head cost of the apparatus. The purpose is to provide.

An image processing apparatus according to an aspect of the present invention that achieves the above object is configured to reciprocally scan a recording head in which a plurality of nozzle arrays corresponding to each of a plurality of colors of ink are arranged in a predetermined direction on the recording medium in the predetermined direction. An image processing apparatus that generates recording data used in an inkjet recording apparatus that performs recording, and performs color conversion to convert data corresponding to ink using RGB data as a conversion table used to generate the recording data When recording in forward scanning and backward scanning on storage means for storing the first and second conversion tables for processing and image data of the area to be recorded in one scanning Determining means for determining whether or not a predetermined number or more of pixels having a color difference greater than or equal to a predetermined number are included, and according to the determination result of the determination means, the first and second conversion sensors. A color conversion processing unit that performs color conversion processing by switching a table; and an output unit that outputs image data processed in the color conversion processing unit to the ink jet recording apparatus, the color conversion processing unit including the determination If the result does not include (A) a predetermined number or more, both the image data to be recorded in the forward scan and the image data to be recorded in the backward scan are processed using the first conversion table, (B) When a predetermined number or more are included, the image data to be recorded in the forward scan is processed using the first conversion table, and the second image data to be recorded in the backward scan is processed. The processing is performed using the conversion table .

  In addition, the above object is an image processing method having steps corresponding to each means of the above-described image processing apparatus, a program installed in a computer apparatus connected to the recording apparatus, and causing the computer apparatus to execute the image processing method, This can also be achieved by a storage medium storing the program.

  According to the present invention, it is possible to reduce the color difference between forward scanning and backward scanning without increasing the size and cost of the apparatus.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the components described in the following embodiments are merely examples, and are not intended to limit the scope of the present invention only to them.

  In this specification, “recording” (sometimes referred to as “printing”) is not only for forming significant information such as characters and figures, but also for human beings visually perceived regardless of significance. Regardless of whether or not it has been manifested, it also represents a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or the medium is processed.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Furthermore, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly in the same way as the definition of “recording (printing)” above. It represents a liquid that can be used for forming a pattern or the like, processing a recording medium, or processing an ink (for example, solidification or insolubilization of a colorant in ink applied to the recording medium).

  Furthermore, unless otherwise specified, the “nozzle” collectively refers to an ejection port or a liquid channel communicating with the ejection port and an element that generates energy used for ink ejection.

<Outline block diagram>
FIG. 1 is a schematic block diagram illustrating a control configuration example of a recording system according to the present invention. As shown in the figure, a recording system according to the present invention includes an inkjet recording apparatus and a host device connected to the recording apparatus and transmitting data to be recorded. The host apparatus includes an external device such as a digital camera. Connectable.

  The ink jet recording apparatus is composed of an MPU, a ROM, a RAM, and the like, and controls the entire recording apparatus 101, a recording buffer 102 that stores recording data before being transferred to the recording head in a raster format, and a recording buffer. A recording head 103 that selectively ejects ink according to the recorded data, a motor control unit 104 that controls a motor for driving a carriage, feeding a recording medium, and discharging paper, and an interface for communicating with a host device ( I / F) unit 105 and a data buffer 106 for temporarily storing recording data received from the host device. Reference numeral 107 denotes a system bus that connects the main control unit 101 and each unit.

  On the other hand, a host device such as a PC that transmits control data and recording data to the ink jet recording apparatus is composed of an MPU, a ROM, a RAM, and the like. An interface (I / F) unit 109 that communicates with the recording apparatus, a main memory 110, an external I / F unit 111 that communicates with a connected external device, a main control unit 108, and a system bus 112 that connects each unit And have.

  The interface between the inkjet recording apparatus and the host device and the interface between the host device and the external device can be used in various specifications regardless of wired or wireless. Typical specifications include the Centronics interface, USB (1.0 and 2.0), IEEE 1394, IrDA, Bluetooth, various wired and wireless LAN standards, etc., which are appropriate for the usage and device configuration. Is appropriately selected.

  Image data input to the host device from an external device, image data created by an application of the host device, various conversion tables downloaded via the network (for example, conversion tables for subsequent processing), etc. are stored in the main memory. 110. When the application instructs to record the image data by the inkjet recording apparatus, the printer driver is activated, and the main control unit 108 performs predetermined image processing on the image data stored in the main memory 110 according to the setting. To generate recording data to be transmitted to the recording apparatus. That is, the host device of this embodiment operates as an image processing apparatus according to the present invention.

  Image data stored in the main memory by the host device is additive color mixture data using three primary colors of RBG suitable for display on a display unit such as a liquid crystal screen or a CRT. On the other hand, the ink jet recording apparatus performs recording on a recording medium (recording paper) with subtractive color mixing including inks of the three primary colors of CMY. Therefore, in the image processing apparatus, it is necessary to perform predetermined image processing including color conversion processing for converting RGB image data into recording data corresponding to ink including the three primary colors of CMY used in the printer. As an example of the predetermined image processing, as will be described in detail below, color conversion that converts image data expressed in RGB into data (also referred to as color separation data) corresponding to the type of ink using the data. Processing (post processing), error diffusion processing for quantizing the color separation data obtained by the post processing, and the like are included. In this print data generation processing, a desired conversion table (for example, a conversion table for performing subsequent processing) is read from the main memory 110 to the buffer memory of the main control unit 108, and image data is read from the main memory 110, for example, by one scan. This is performed by reading the recording size (one band) as a unit and repeating the data conversion process.

  When changing (switching) a conversion table (conversion table for subsequent processing) used when generating recording data to be transmitted to the recording apparatus from image data stored in the main memory 110, the main memory 110 is accessed. Thus, it is necessary to read out the conversion table. That is, when the conversion table is switched in the reciprocating direction, the main memory 110 is accessed for each path, and the conversion table is read.

<Description of inkjet recording apparatus>
FIG. 7 is an external perspective view showing an outline of the configuration of the ink jet recording apparatus according to the present invention.

  As shown in FIG. 7, an ink jet recording apparatus (hereinafter also simply referred to as a recording apparatus) applies a driving force generated by a carriage motor M1 to a carriage 2 on which a recording head 3 that performs recording by discharging ink in accordance with an ink jet system is mounted. The information is transmitted from the transmission mechanism 4, and the carriage 2 is reciprocated in the direction of the arrow A. For example, the recording medium P such as recording paper is fed through the paper feeding mechanism 5 and conveyed to the recording position, and recording is performed at the recording position. Recording is performed by discharging ink from the head 3 to the recording medium P.

  Further, in order to maintain the state of the recording head 3 satisfactorily, the carriage 2 is moved to the position of the recovery device 10 and the ejection recovery process of the recording head 3 is intermittently performed.

  In addition to mounting the recording head 3 on the carriage 2 of the recording apparatus, an ink cartridge 6 for storing ink to be supplied to the recording head 3 is mounted. The ink cartridge 6 is detachable from the carriage 2.

  The recording apparatus shown in FIG. 7 is capable of color recording. For this purpose, the carriage 2 contains four inks containing magenta (M), cyan (C), yellow (Y), and black (K) inks, respectively. A cartridge is installed. These four ink cartridges are detachable independently.

  Now, the carriage 2 and the recording head 3 can achieve and maintain a required electrical connection by properly contacting the joint surfaces of both members. The recording head 3 applies energy according to a recording signal to selectively eject ink from a plurality of ejection ports for recording. In particular, the recording head 3 of this embodiment employs an ink jet system that ejects ink using thermal energy, and includes an electrothermal transducer to generate thermal energy, which is applied to the electrothermal transducer. Electric energy is converted into thermal energy, and ink is ejected from the ejection port by utilizing pressure changes caused by bubble growth and contraction caused by film boiling caused by applying the thermal energy to the ink. The electrothermal transducer is provided corresponding to each of the ejection ports, and ink is ejected from the corresponding ejection port by applying a pulse voltage to the corresponding electrothermal transducer in accordance with the recording signal.

  As shown in FIG. 7, the carriage 2 is connected to a part of the driving belt 7 of the transmission mechanism 4 that transmits the driving force of the carriage motor M <b> 1, and slides in the direction of arrow A along the guide shaft 13. It is guided and supported freely. Accordingly, the carriage 2 reciprocates along the guide shaft 13 by forward and reverse rotations of the carriage motor M1. A scale 8 is provided for indicating the absolute position of the carriage 2 along the direction of movement of the carriage 2 (the direction of arrow A). In this embodiment, the scale 8 uses a transparent PET film with black bars printed at a necessary pitch, one of which is fixed to the chassis 9 and the other is supported by a leaf spring (not shown). Yes.

  Further, the recording apparatus is provided with a platen (not shown) facing the discharge port surface where the discharge port (not shown) of the recording head 3 is formed, and the recording head 3 is driven by the driving force of the carriage motor M1. Simultaneously with the reciprocating movement of the mounted carriage 2, recording is performed over the entire width of the recording medium P conveyed on the platen by giving a recording signal to the recording head 3 and discharging ink.

  Further, in FIG. 7, 14 is a transport roller driven by a transport motor M2 to transport the recording medium P, 15 is a pinch roller that abuts the recording medium P against the transport roller 14 by a spring (not shown), and 16 is a pinch. A pinch roller holder 17 that rotatably supports the roller 15 is a conveyance roller gear fixed to one end of the conveyance roller 14. Then, the transport roller 14 is driven by the rotation of the transport motor M2 transmitted to the transport roller gear 17 through an intermediate gear (not shown).

  Further, reference numeral 20 denotes a discharge roller for discharging the recording medium P on which an image is formed by the recording head 3 to the outside of the recording apparatus, and is driven by transmitting the rotation of the transport motor M2. . The discharge roller 20 abuts on a spur roller (not shown) that presses the recording medium P by a spring (not shown). Reference numeral 22 denotes a spur holder that rotatably supports the spur roller.

  Further, as shown in FIG. 7, the recording apparatus includes a desired position (for example, a home position) outside the range of reciprocating motion (outside the recording area) for the recording operation of the carriage 2 on which the recording head 3 is mounted. A recovery device 10 for recovering the ejection failure of the recording head 3 is disposed at a position corresponding to (1).

  The recovery device 10 includes a capping mechanism 11 for capping the ejection port surface of the recording head 3 and a wiping mechanism 12 for cleaning the ejection port surface of the recording head 3, and interlocks with the capping of the ejection port surface by the capping mechanism 11. Ink recovery such as forcibly discharging ink from the discharge port by suction means (suction pump or the like) in the recovery device, thereby removing ink or bubbles having increased viscosity in the ink flow path of the recording head 3 Process.

  Further, when the recording head 3 is not in operation or the like, the ejection port surface of the recording head 3 is capped by the capping mechanism 11 to protect the recording head 3 and to prevent ink evaporation and drying. On the other hand, the wiping mechanism 12 is arranged in the vicinity of the capping mechanism 11 and wipes ink droplets adhering to the discharge port surface of the recording head 3.

  The capping mechanism 11 and the wiping mechanism 12 can keep the ink ejection state of the recording head 3 normal.

<Image processing flow>
Next, the flow of image processing in the ink jet recording system of this embodiment (a system including an ink jet recording apparatus and a host device) will be described with reference to FIG. As described above, a part of the image processing described here, specifically, the image processing executed by the host device is such that when the host device is instructed to record image data, the printer driver is activated, It is executed by the main control unit 108 according to the setting.

  FIG. 2 is a block diagram showing a flow of image data conversion processing in the ink jet recording system of this embodiment. The ink jet recording apparatus applied in the present embodiment performs recording using inks of four colors of cyan, magenta, yellow, and black. For this purpose, a recording head that discharges these four colors of ink is prepared. . As shown in FIG. 2, each processing shown here is assumed to be configured by a recording device and a personal computer (PC) as a host device.

  There are an application and a printer driver as programs that operate in the operating system of the host device, and the application J0001 executes processing for creating image data corresponding to an image recorded by the recording device. At the time of actual recording, image data created by the application is passed to the printer driver.

  Assume that the printer driver in the present embodiment includes pre-processing J0002, post-processing J0003, γ correction J0004, halftoning J0005 that is multi-level quantization, and print data creation J0006 as processing. Here, each process will be briefly described. The pre-stage process J0002 performs color gamut mapping. For example, in the case of sRGB standard image data, data conversion is performed to map the color gamut reproduced by the sRGB standard image data R, G, B into the color gamut reproduced by the recording apparatus. Specifically, by using a 3D lookup table (3DLUT) for data in which R, G, and B are each expressed in 8 bits, 8 bits of R, G, and B depending on the color gamut that can be expressed by the recording apparatus Convert to data.

The post-stage process J0003 is a color separation data (here, 8-bit data C, M, Y) corresponding to a combination of inks that reproduce the colors represented by the RGB data, using the 8-bit data R, G, B obtained in the pre-stage process J0002. , K). Here, the RGB data is converted into CMYK data by using a conversion table (for example, a three-dimensional lookup table) in which the RGB data and the CMYK data corresponding to ink are associated one-to-one. Specifically, in the three-dimensional lookup table, R, G, and B values each represented by 8 bits (0 to 255) and CMYK values each represented by 8 bits (0 to 255) are stored in advance. Associated with,
From (R, G, B) = (0-255,0-255,0-255) (C, M, Y, K) = (0-255,0-255,0-255,0-255)
Conversion to

For example,
If (R, G, B) = (0, 0, 0),
(C, M, Y, K) = (0, 0, 0, 255), and
If (R, G, B) = (255, 255, 255),
(C, M, Y, K) = (0, 0, 0, 255), and
If (R, G, B) = (0, 128, 0),
(C, M, Y, K) = (0, 128, 128, 0).
In the present embodiment, at least two types of such conversion tables are provided, and the conversion tables are switched according to conditions described later.

  The γ correction J0004 performs gradation value conversion for each ink color data of the color separation data obtained by the post-processing J0003. Specifically, by using a one-dimensional LUT corresponding to the gradation characteristics of each color ink of the recording apparatus, conversion is performed so that the color separation data is linearly associated with the gradation characteristics of the recording apparatus.

  Halftoning J0005 performs quantization by converting 8-bit color separation data Y, M, C, and K into 2-bit data. In this embodiment, multi-level error diffusion is used to convert 256-gradation 8-bit data into 3-gradation 2-bit data. This 2-bit data is data serving as an index for indicating an arrangement pattern in the dot arrangement patterning process performed in the printing apparatus.

  At the end of the process performed by the printer driver, print data is created by adding print control information to the print image data containing the above-mentioned 2-bit index data by print data creation process J0006. The host device transmits this recording data to the recording device.

  The recording apparatus performs a dot arrangement patterning process J0007 on the recording data transmitted from the host device.

  Here, the dot arrangement patterning process J0007 will be described. In the halftone process described above, the number of levels is reduced from 256-value multi-value density information (8-bit data) to ternary tone value information (2-bit data). However, information that can be actually recorded by the ink jet recording apparatus of the present embodiment is binary information indicating whether or not to record ink. In the dot arrangement patterning process, it plays a role of reducing the ternary level from 0 to 2 to the binary level that determines the presence or absence of dots. Specifically, in this dot arrangement patterning process J0007, for each pixel represented by 2-bit data of level 0 to 2 that is an output value from the halftone processing unit, the gradation value (level 0 to 0) of that pixel is represented. A dot arrangement pattern corresponding to 2) is assigned, whereby dot on / off is defined in each of a plurality of areas in one pixel, and ejection of 1 bit of “1” or “0” in each area in one pixel Arrange the data.

  FIG. 8 shows output patterns for input levels 0 to 2 that are converted by the dot arrangement patterning process of the present embodiment. Each level value shown on the right side of the drawing corresponds to level 0 to level 2 which are output values from the halftone processing unit. An area composed of 2 vertical areas × 1 horizontal area arranged on the left side corresponds to an area of one pixel (pixel) output by halftone processing, and is 600 ppi (pixels / inch; reference value) in both vertical and horizontal directions. The size corresponds to the pixel density. Each area in one pixel corresponds to a minimum unit in which dot ON / OFF is defined, and corresponds to a recording density of 1200 dpi (dot / inch; reference value) in the vertical direction and 600 dpi in the horizontal direction. In the recording apparatus of this embodiment, a predetermined amount of ink droplets is recorded in one area represented by about 20 μm in length and about 40 μm in width corresponding to the above recording density to obtain a desired density. It is designed to be In the figure, the filled area indicates an area where dots are recorded, and the number of dots to be recorded increases by one as the number of levels increases.

  In the case of the input level 1, two types of patterns are prepared. That is, a pattern for recording the upper area and a pattern for recording the lower area among the two areas arranged vertically. As described above, when there are a plurality of patterns capable of expressing the same density, if the density expression is performed only with the fixed pattern, a texture or a pseudo contour may be generated on the image. Therefore, in the present embodiment, a configuration is adopted in which a plurality of patterns are mixedly arranged even when expressing the same density.

  Referring to FIG. 2 again, the binary data of each color that has been subjected to the dot arrangement patterning process is then input to the drive circuit J0009. The 1-bit data of each color input to the driving circuit J0009 is converted into a driving pulse for the recording head J0010, and ink is ejected from the recording head J0010 for each color at a predetermined timing.

<Color difference due to print head configuration and print scan>
FIG. 3 is a diagram schematically showing the arrangement of each color nozzle row of the recording head 3 used in the ink jet recording apparatus of the present embodiment. This figure shows the arrangement of nozzle rows when the recording head 3 is viewed from above.

  In the figure, reference numerals 301 to 304 denote nozzle arrays for ejecting ink. 301 represents black ink, 302 represents cyan ink, 303 represents magenta ink, and 304 represents a nozzle array that ejects yellow ink. In the illustrated configuration, the number of nozzles constituting each nozzle row is equal, and includes, for example, 256 nozzles.

  The arrangement of the nozzle rows of the recording head is not limited to the example shown in FIG. 3, and various forms such as those in which the arrangement order and the number of nozzles included in each row are different can be used. In the example of FIG. 3, the nozzle row of each color is a head that is integrally formed on one chip, but each color nozzle row may be a head that is formed separately on another chip. Further, one nozzle (for example, K) of four colors (CMYK) and the remaining three (for example, CMY) nozzle arrays may be formed in different chips.

  FIG. 4 is a diagram illustrating an example of scanning by the recording head when recording is performed on one recording medium. In the illustrated example, the recording medium P is conveyed in the direction of arrow F and recorded by four scans (passes) indicated by S1, S2, S3, and S4 from the leading end side. Here, scanning indicated by S1 and S3 is forward scanning in which the recording head moves from left to right, and scanning indicated by S2 and S4 is backward scanning in which the recording head moves from left to right.

  When such a recording scan is performed using a recording head having a nozzle row as shown in FIG. 3, ink droplets are ejected in the order of yellow, magenta, cyan, and black in the scans of S1 and S3. In the scan of S4, since ink droplets are ejected in the order of black, cyan, magenta, and yellow, the order of ink ejected (printed) onto the recording medium differs depending on the scanning direction. For this reason, even if the same amount of ink is ejected from pixels expressed by a plurality of colors of ink, the colors are different. When this color difference (color difference) increases, it is perceived as color unevenness.

FIG. 5 is a graph showing a color reproduction range in forward scanning and backward scanning. In this figure, the color reproduction range shown on the CIE-L ^* a ^* b ^* space is projected onto the ab plane. For example, reference numeral 501 denotes a color reproduction range that can be recorded by forward scanning, and reference numeral 502 denotes a color reproduction range that can be recorded by backward scanning. As is apparent from FIG. 5, the color reproduction range varies depending on the scanning direction. This difference in the color reproduction range is caused by the difference in the overlapping order of the ink in the reciprocation.

As described above, when the color difference (ΔE) between the color recorded in the forward scanning and the color recorded in the backward scanning becomes large, this color difference is perceived as color unevenness. Therefore, in such a case, it is necessary to perform image processing for reducing the color difference. Therefore, in the present embodiment, when there is a high possibility that the color difference becomes large and is perceived as color unevenness, the conversion table to be used (specifically, the three-dimensional lookup table used in subsequent processing) is changed. I am doing so.
In the CIE-L ^* a ^* b ^* space, the color difference ΔE between the two colorimetric values (L1 ^* , a1 ^* , b1 ^* ) and (L2 ^* , a2 ^* , b2 ^* ) is
ΔE = {(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² } ^1/2
Determined by However,
ΔL ^* = L1 ^* −L2 ^*
Δa ^* = a1 ^* −a2 ^*
Δb ^* = b1 ^* −b2 ^*
It is.

  In this embodiment, two types of conversion tables (a first conversion table and a second conversion table) are provided, and in the case of image data in which color unevenness is difficult to occur, the first conversion table is used. Thus, in the case of image data in which color unevenness is likely to occur, the conversion table to be used is switched according to the scanning direction. Specifically, the first conversion table is used during image processing for creating data used in forward scanning, and the second conversion table is used during image processing for creating data used for backward scanning. .

  Here, the first conversion table is a basic table used when creating at least forward scan data regardless of image data. It is used to create reciprocal scan data for image data that is less likely to cause color unevenness, and it is used to create only forward scan data for image data that is more likely to cause color unevenness. The On the other hand, the second conversion table is a color difference reduction table used only in the case of image data in which color unevenness is likely to occur. In the case of image data in which color unevenness is likely to occur, it is used to create reverse scan data.

  The second conversion table has a configuration in which data conversion is performed so as to approximate the color in the case of printing by forward scanning. In other words, the second table is created using the first table as a target for the color that appears when recording in the forward direction.If the same RGB value is input, the second table is used in the backward direction. The color recorded using is adjusted so as to be as close as possible to the color recorded using the first table in the forward direction. As a result, when the data is generated using the first conversion table in the forward scan and using the second conversion table in the backward scan, compared to the case where the data of both reciprocal scans are generated using the first conversion table. In this case, the color difference between when printing is performed by forward scanning and when recording is performed by backward scanning is reduced.

<Conversion table switching process>
Hereinafter, the conversion table switching process in this embodiment will be described with reference to the flowchart of the print data generation process by the printer driver shown in FIG.

  First, image data to be recorded in one scan (pass) is input in step S601. That is, image data corresponding to one band is input. As described above, the image data is 8-bit RGB data. Next, in step S602, it is determined whether the image data corresponding to the one band is image data in which color unevenness is likely to occur. In this embodiment, in order to determine whether or not the image data is likely to have color unevenness, it is checked whether or not a predetermined number or more of pixels of a specific color are included in the image data. Here, the predetermined number may be an integer greater than or equal to 1, but the optimum value is the type of media such as plain paper or coated paper, fast, standard, recording mode such as clean, and whether it is dye or pigment. It is determined in consideration of the ink type.

  Here, the specific color is a color in which the difference between the color recorded in the forward scanning and the color recorded in the backward scanning is a predetermined color difference (for example, ΔE = 2) or more. For example, a color having a color difference ΔE recorded in both directions of two or more is registered in advance in the database, and each pixel included in the input image data is checked against the database to check in step S602. Note that in the stage of step S602, data corresponding to each pixel constituting the image data corresponding to the one band is expressed by RGB values. Therefore, by registering in advance an RGB value corresponding to a color having a color difference ΔE of 2 or more and searching whether the RGB value of the pixel matches the registered RGB value, the color difference ΔE is 2 Whether the color is the above or not is determined.

  If a predetermined number or more of pixels of a specific color are not included in step S602, that is, if the band is less likely to cause color unevenness, the first conversion table is read regardless of the scanning direction, and the process proceeds to step S606. . On the other hand, if a predetermined number or more of pixels of a specific color are included in step S602, that is, if the band is likely to cause color unevenness, the process proceeds to step S603 to check whether the scanning direction is the forward direction. A check is made, and if it is forward direction recording, the process advances to step S604 to read the first conversion table. On the other hand, if the scanning direction is the backward direction, the process proceeds to step S605 to read the second conversion table.

  Note that the conversion table to be switched according to the scanning direction in this embodiment is a conversion table for performing color conversion processing from data expressed in RGB to data expressed in CMYK, which is used in the subsequent processing J0003 in FIG. .

  Thereafter, in step S606, the recording data is subjected to image processing including post-processing J0003 performed using the conversion table (specifically, post-processing 0003, γ correction processing J0004, halftone processing J0005, etc. described in FIG. 2). The recording data generated in step S607 is transmitted to the recording apparatus.

  Here, the post-processing J0003 performed in step S606 will be described. When step S604 is performed before step S606, data processing using the first conversion table is performed, and when step S605 is performed before step S606, data processing using the second conversion table is performed. Made. Thereby, even when color unevenness is likely to occur, color unevenness in reciprocating scanning can be reduced. On the other hand, when the process directly goes from step S602 to step S606 without passing through step S604 or step S605, that is, when it is determined in step S602 that the color unevenness is unlikely to occur, the first data is displayed regardless of the scanning direction. Data processing using the conversion table is performed.

  In step S608, it is checked whether or not the processing of the recording data for all passes has been completed. If not, the process returns to step S601 to repeat the subsequent processing. If it is determined in step S608 that the recording data processing for all passes has been completed, the processing ends.

  As described above, according to the present embodiment, when color unevenness is likely to occur in which a predetermined number or more of pixels having a color difference greater than or equal to a predetermined number are included, the conversion table used for generating print data is set in the scanning direction. Switch accordingly.

  For this reason, the color difference in reciprocating scanning can be reduced.

<Other embodiments>
In the above-described embodiment, the first and second conversion tables are provided, and when the color unevenness is easily noticeable, the two types of conversion tables are switched according to the scanning direction. Regardless of the configuration, the first conversion table is used, but the number of conversion tables is not limited to two. For example, when three types of conversion tables (conversion tables A to C) are provided and the color unevenness is not noticeable, the basic table (conversion table A) is used regardless of the scanning direction, and the color unevenness is easily noticeable. May be configured to switch between two types of color difference reduction conversion tables (conversion tables B and C) according to the scanning direction. In any case, when color unevenness is conspicuous, it is only necessary to switch between two types of conversion tables in accordance with the scanning direction.

  In the above embodiment, whether or not to switch the conversion table is determined depending on whether or not a predetermined number of pixels of a specific color with a color difference equal to or greater than a predetermined value are included. The criterion for determining whether or not to switch is not limited to this example. As described above, this determination criterion only needs to be able to determine whether the image data is likely to cause color unevenness. For example, whether the image data includes a predetermined number of pixels (color data) other than black is used as the determination criterion. Also good. In the case of only black data, reciprocal color unevenness cannot occur, and reciprocal color unevenness occurs only when color data is included. Therefore, it is also effective to use whether or not pixels of data other than black are included in image data corresponding to one band. This is effective, for example, in a document in which photographs and characters are mixed.

  Also, in general, the difference in color depending on the scanning direction becomes significant in an ink jet recording apparatus when the amount of ink used is large. Therefore, the criterion for determining whether to switch the conversion table is the ink usage amount. It may be determined whether or not a predetermined number or more of pixels are included. Here, the predetermined number is an integer of 1 or more.

  Furthermore, in the above-described embodiment, as a conversion table that is switched according to the scanning direction, a conversion table that performs color conversion processing from data expressed in RGB to data expressed in CMYK corresponding to the used ink is taken as an example. However, the conversion table switched according to the scanning direction is not limited to this type of conversion table. Any conversion table used in the image processing as shown in FIG. 2 may be used. For example, the conversion table used in the pre-stage processing J0002 may be switched.

  In the above-described embodiment, an example is described in which a conversion table that can change the color (at least one of hue, brightness, and saturation) of a recording pixel is used to reduce reciprocal color unevenness. The process of reducing the color unevenness is not limited to changing the conversion table. In short, in order to reduce reciprocal color unevenness, it is only necessary to change the color of the recording pixel (at least one of hue, brightness, and saturation). In order to change the color (at least one of hue, brightness, and saturation) of the recording pixel, the halftone processing method may be changed or the dot arrangement method of the dot arrangement pattern may be changed. Therefore, it is also effective to change the halftone processing method and the dot arrangement method of the dot arrangement pattern according to the scanning direction. Of course, such a change is performed only in the case of image data in which color unevenness is likely to occur.

  Further, in the above-described embodiment, the mode of using four types of CMYK inks has been described, but it goes without saying that the type of ink to be used is not limited to this. For example, six types of inks may be used in which four types of CMYK plus LC (light cyan) and LM (light magenta) inks are used. In this case, the conversion table used in the subsequent process converts data expressed in RGB into color separation data corresponding to the above six types of ink.

  In addition, in the above embodiment, as described with reference to FIG. 2, the post-processing J0003, the gamma correction processing J0004, the halftone processing J0005, and the recording data creation processing J0006 are performed in the host device (printer driver). In this embodiment, the dot pattern arrangement processing J0007 is performed. However, these processing J0003 to J0007 may be performed by either the host device or the ink jet recording apparatus. For example, when the host device performs up to the pre-stage process J0002 and the image processing after the post-stage process J0003 is performed on the recording apparatus side, the recording apparatus side executes a process of switching the conversion table used in the post-stage process according to the scanning direction. become.

  As described above, the present invention may be applied to a recording system including a plurality of devices as described above. For example, a slot into which a storage medium can be inserted and an image input device such as a digital camera are provided. Even when applied to an inkjet recording apparatus such as a so-called direct printer, which has a connectable interface and can directly record image data stored in a storage medium or an image input device without connecting a host device. good. In the case of a direct printer not connected to a host device, all image processing including pre-processing J0002 to dot pattern arrangement processing J0007 is performed by the ink jet recording apparatus.

  In the present invention, a software program (in this embodiment, a printer driver corresponding to the flowchart shown in FIG. 6) for realizing the functions of the above-described embodiment is directly or remotely supplied to a system or apparatus, and the system or This includes the case where the computer of the apparatus is also achieved by reading and executing the supplied program code. In that case, as long as it has the function of a program, the form does not need to be a program.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. That is, the claims of the present invention include the computer program itself for realizing the functional processing of the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

  As a recording medium for supplying the program, for example, flexible disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R).

  As another program supply method, a client computer browser is used to connect to an Internet homepage, and the computer program of the present invention itself or a compressed file including an automatic installation function is downloaded from the homepage to a recording medium such as a hard disk. Can also be supplied. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the scope of the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  In addition to the functions of the above-described embodiments being realized by the computer executing the read program, the OS running on the computer based on an instruction of the program is a part of the actual processing. Alternatively, the functions of the above-described embodiment can be realized by performing all of them and performing the processing.

  Furthermore, after the program read from the recording medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion board or The CPU or the like provided in the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

1 is a block diagram showing a schematic configuration of an embodiment of a recording system according to the present invention. It is a figure for demonstrating the flow of the image processing in the recording system of embodiment. FIG. 4 is a diagram illustrating an arrangement of nozzle rows of a recording head. It is a figure which shows the example of the scanning by the recording head at the time of recording on a recording medium. It is a graph which shows the example of the color reproduction range when a color difference comes out in a scanning direction. It is a flowchart of the recording data generation process in the embodiment. 1 is an external perspective view showing an outline of a configuration of an ink jet recording apparatus according to the present invention. It is a figure which shows the dot arrangement pattern with respect to the gradation levels 0-2.

Claims (3)

Recording data used in an inkjet recording apparatus that performs recording by reciprocally scanning a recording head in which a plurality of nozzle arrays corresponding to each of a plurality of colors of ink are arranged in a predetermined direction on the recording medium is generated. An image processing apparatus,
Storage means for storing first and second conversion tables for performing color conversion processing for conversion into data corresponding to ink using RGB data as the conversion table used for generating the recording data;
Determining whether or not the image data of the area to be recorded in one scan includes a predetermined number or more of pixels that cause a color difference greater than or equal to a predetermined value when recorded by a forward scan and when recorded by a backward scan Determination means to perform,
Color conversion processing means for performing color conversion processing by switching the first and second conversion tables according to the determination result of the determination means ;
Output means for outputting the image data processed in the color conversion processing means to the ink jet recording apparatus ,
When the determination result does not include (A) a predetermined number or more in the determination result, the color conversion processing means performs the first conversion on both the image data to be recorded in the forward scanning and the image data to be recorded in the backward scanning. Processing is performed using the conversion table. (B) When a predetermined number or more are included, processing is performed on the image data to be recorded by forward scanning using the first conversion table, and recording is performed by backward scanning. An image processing apparatus that performs processing on power image data using the second conversion table . Image processing for generating recording data used in an ink jet recording apparatus that performs recording by reciprocally scanning a recording head in which nozzle arrays corresponding to each of a plurality of colors of ink are arranged in a predetermined direction on the recording medium. A method,
The image data recording region in one scan, determines whether a pixel given more color difference occurs between when being recorded when a backward scan recorded by forward scan that contain more than a predetermined number A determination step to
A color conversion processing step for switching the first and second conversion tables for performing color conversion processing for converting color data into data corresponding to ink using RGB data according to the determination result in the determination step. When,
An output step of outputting the image processed in the color conversion processing step to the ink jet recording apparatus ,
In the color conversion processing step, when the determination result does not include (A) a predetermined number or more, the first color conversion processing step is performed on both the image data to be recorded in the forward scanning and the image data to be recorded in the backward scanning. Processing is performed using the conversion table. (B) When a predetermined number or more are included, processing is performed on the image data to be recorded by forward scanning using the first conversion table, and recording is performed by backward scanning. An image processing method comprising: performing processing on power image data using the second conversion table . Installed in a computer device connected to an ink jet recording apparatus that performs recording by reciprocally scanning a recording head in which a nozzle row corresponding to each of a plurality of colors of ink is arranged in a predetermined direction on the recording medium; A program for generating and outputting recording data used in a recording device,
The image data recording region in one scan, determines whether a pixel given more color difference occurs between when being recorded when a backward scan recorded by forward scan that contain more than a predetermined number A determination step to
A color conversion processing step of performing color conversion processing by switching between the first and second conversion tables for performing color conversion processing for conversion to data corresponding to ink using RGB data according to the determination result in the determination step When the determination result does not include (A) a predetermined number or more, the first conversion table is applied to both the image data to be recorded in the forward scanning and the image data to be recorded in the backward scanning. (B) When a predetermined number or more are included, the image data to be recorded in the forward scanning is processed using the first conversion table, and the image data to be recorded in the backward scanning. A color conversion processing step for performing processing using the second conversion table ,
For causing a computer device to execute the program.

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