JP2015133607A - Print control device, program, and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the image quality while suppressing the increment of the amount of data.SOLUTION: A print control device executes a color conversion processing step of converting image data in a first color space into image data in a second color space corresponding to ink colors including color ink and black ink discharged from a printer. The print control device includes: a color table for converting the gradation value of a color area except for an achromatic area in the first color space into a gradation value in the second color space; a first table for converting the gradation value of the achromatic area in the first color space to a gradation value in the second color space; and a second table which is different from the first table, and converts the gradation value of the achromatic area in the first color space into a gradation value in the second color space. The print control device executes a first color conversion processing step and a second color conversion processing step of converting the gradation value of a pixel constituting image data in the first color space into a gradation value in the second color space, on the basis of the color table and the first table, and the color table and the second table, respectively while switching the processing steps from one to the other according to the printing condition of the printer.

Description

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

  2. Description of the Related Art A printing apparatus that prints an image by ejecting ink onto a substrate (for example, paper) is known. A print control apparatus that controls such a printing apparatus uses a table (color conversion lookup table) to change the color space (R, G, B) of image data to the color space of ink used in the printing apparatus (for example, C, M, Y, K). Then, ink is ejected from the head of the printing apparatus based on the converted data.

  In addition, not only black ink but also chromatic (for example, cyan, magenta, and yellow) inks within the allowable range of ink duty are used to improve filling when printing an achromatic image (for example, gray) on a substrate. There is also known one that is controlled to be used (overstrike) (for example, see Patent Document 1).

JP 2003-63044 A

  Color development may vary depending on printing conditions. For example, even when the same “paper type name (for example, plain paper)” is selected in the printer driver, the “paper quality” may differ depending on the manufacturer or regional difference (for example, Japan and Europe and America), and the coloring may be different. For this reason, the image quality may change depending on the printing conditions. In particular, as described above, an achromatic color formed using chromatic ink tends to cause a difference in image quality. In addition, if each color conversion lookup table is created for each printing condition, it takes time and the amount of data in the color conversion lookup table becomes enormous.

  Therefore, an object of the present invention is to improve image quality while suppressing an increase in data amount.

  A main invention for achieving the above object is a color conversion process for converting image data in a first color space into image data in a second color space corresponding to the ink colors of the color ink and black ink ejected by the printing apparatus. A color control table for converting gradation values of a color area excluding an achromatic color area of the first color space into a gradation value of the second color space; A first table for converting gradation values of the achromatic color region into gradation values of the second color space, and a second table different from the first table, wherein the achromatic color region of the first color space And a second table for converting the gradation value into the gradation value of the second color space, and the gradation of the pixels constituting the image data of the first color space according to the printing conditions of the printing apparatus The values are stored in the color table and the first table. Based on the first color conversion processing for converting to the gradation value of the second color space, and the gradation value of the pixels constituting the image data of the first color space, the color table and the second table And a second color conversion process for converting to a gradation value of the second color space based on the above.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

FIG. 1A is a block diagram illustrating a printing system having a printer 1 and a computer CP, and FIG. 1B is a perspective view of the printer 1. FIG. 8 is an explanatory diagram of processing by a printer driver. It is explanatory drawing which showed notionally the color conversion LUT referred for a color conversion process. It is a conceptual diagram for demonstrating conversion when RGB image data does not exist in a lattice point. 5A to 5C are diagrams showing each table of the color conversion LUT in this embodiment. 5A is a color table, FIG. 5B is a first gray table, and FIG. 5C is a second gray table. It is a flowchart explaining the color conversion process of 1st Embodiment. FIG. 10 is a diagram illustrating an example of a UI screen for setting printing conditions in the second embodiment.

=== Overview ===
At least the following matters will become clear from the description of the present specification and the drawings.

A printing control apparatus that performs color conversion processing for converting image data in a first color space into image data in a second color space corresponding to the ink colors of the color ink and black ink ejected by the printing apparatus. A color table for converting gradation values of color areas excluding the achromatic color area of the color space into gradation values of the second color space; and gradation values of the achromatic color area of the first color space A first table for converting to gradation values in a two-color space, and a second table different from the first table, wherein the gradation values of the achromatic region in the first color space are A second table for converting to gradation values, and according to printing conditions of the printing apparatus, gradation values of pixels constituting the image data in the first color space are converted to the color table and the first table. Based on the table, the gradation value of the second color space is changed. And the gradation value of the pixel constituting the image data of the first color space is converted into the gradation value of the second color space based on the color table and the second table. A print control apparatus characterized by switching the second color conversion process to be converted is clarified.
According to such a printing control apparatus, the achromatic color area table is changed according to the printing conditions, so that the image quality can be improved. Also, since the color table is used in common, the color table is used for each printing condition. Compared with the case where all the conversion LUTs are created, it takes less time and the increase in the number of tables can be suppressed. Therefore, it is possible to improve the image quality while suppressing an increase in the data amount.

In such a print control apparatus, it is desirable to switch between the first color conversion process and the second color conversion process in accordance with the paper quality of the substrate.
According to such a print control apparatus, it is possible to suppress deterioration in image quality due to a difference in paper quality.

In this printing control apparatus, it is preferable that the first table and the second table have different black ink generation inclinations.
According to such a print control apparatus, the color reproducibility of the achromatic color region can be improved.

In this print control apparatus, the gradation value corresponding to the black ink when the gradation value of the achromatic color region in the first color space is converted by the first table is converted by the second table. In this case, it is desirable that the gradation value corresponding to the black ink is different.
According to such a print control apparatus, the color reproducibility of the achromatic color region can be improved.

  Further, a color table for converting the tone values of the color areas excluding the achromatic color area of the first color space into the tone values of the second color space corresponding to the ink colors of the color ink and the black ink ejected by the printing apparatus. A first table for converting gradation values of the achromatic color region of the first color space into gradation values of the second color space, and a second table different from the first table, A second table for converting the gradation value of the achromatic color region of one color space into the gradation value of the second color space, and converting the image data of the first color space into the image data of the second color space. According to the printing conditions of the printing apparatus, the gradation values of the pixels constituting the image data in the first color space are set to the color control table and the first table. Is converted into a gradation value of the second color space based on A first color conversion process and a gradation value of a pixel constituting the image data in the first color space are converted into a gradation value in the second color space based on the color table and the second table. The program is characterized by switching and executing the second color conversion processing.

  An image processing method for performing color conversion processing for converting image data in a first color space into image data in a second color space corresponding to the ink colors of color ink and black ink discharged from a printing apparatus, A color table for converting gradation values of color areas excluding the achromatic color area of the first color space into gradation values of the second color space; and gradation values of the achromatic color area of the first color space. A first table for converting the gradation value of the second color space to a second table different from the first table, wherein the gradation value of the achromatic region in the first color space is converted to the second color; And using the second table for converting to the gradation value of the space, the gradation value of the pixels constituting the image data of the first color space is converted into the color table and the color table according to the printing conditions of the printing apparatus. Based on the first table, the floor of the second color space A first color conversion process for converting to a value and a gradation value of a pixel constituting the image data in the first color space, based on the color table and the second table, in the second color space. An image processing method characterized by switching between the second color conversion process for converting to a tone value is clarified.

=== First Embodiment ===
<Explanation of terms>
First, the meanings of terms used in describing this embodiment will be described.

  A “print image” is an image printed on a substrate (paper in the present embodiment). The print image of the ink jet printer is composed of countless dots formed on paper.

  “Image data” is data indicating a two-dimensional image. In an embodiment described later, there are image data in the RGB color space, image data in the CMYK color space, and the like.

  The image data includes 256 gradation image data and 4 gradation image data. When the printer forms dots with four gradations (large dots, medium dots, small dots, and no dots), the four gradation image data in the CMYK color space indicates the formation state of the dots constituting the print image. For this reason, the four-tone image data in the CMYK color space is sometimes called “print image data”.

  A “pixel” is a minimum unit that constitutes an image. An image is formed by arranging these pixels two-dimensionally. Mainly means a pixel on the image data.

  “Pixel data” is data indicating the gradation value of a pixel. The image data is composed of a large number of pixel data. The pixel data is sometimes referred to as “pixel gradation value”.

  However, the meanings of general terms such as “image data” and “pixel” are appropriately interpreted not only according to the above description but also in accordance with ordinary technical common sense.

<Configuration of printing system>
FIG. 1A is a block diagram illustrating a printing system having a printer 1 and a computer CP, and FIG. 1B is a perspective view of the printer 1. The printer 1 ejects ink, which is a kind of liquid, toward a printing material such as paper, cloth, or film.

  The computer CP is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer CP transmits print image data corresponding to the image to the printer 1. In addition, a printer driver is installed in the computer CP. The printer driver is a program that causes a display device (not shown) of the computer CP to display a user interface (hereinafter also referred to as UI), or allows the computer CP to perform color conversion processing or the like. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Alternatively, the printer driver can be downloaded to the computer CP via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions. Processing by the printer driver will be described later.

  Note that “printing apparatus” means an apparatus that prints an image on a substrate, and corresponds to, for example, the printer 1. The “printing control device” means a device that controls the printing device, for example, a computer CP in which a printer driver is installed.

  The printer 1 includes a paper transport mechanism 10, a carriage movement mechanism 20, a head unit 30, a drive signal generation circuit 40, a detector group 50, and a controller 60.

  The paper transport mechanism 10 transports the substrate (paper S) in the transport direction.

  The carriage moving mechanism 20 moves the carriage 21 to which the head unit 30 is attached in a direction intersecting with the transport direction (hereinafter also referred to as a movement direction).

  The head unit 30 includes a head 31 and a head controller HC. The head 31 ejects ink toward the paper S. The head controller HC controls the head 31 based on a head control signal from the controller 60 of the printer 1.

  The head 31 has nozzle rows that discharge cyan (C) ink, magenta (M) ink, yellow (Y) ink, and black (K) ink, respectively. Each nozzle row includes a plurality of nozzles that are ejection ports for ejecting ink of each color. Piezo elements are arranged corresponding to the nozzles of the head 31. By the operation of this piezo element, it is possible to eject ink from the nozzle.

  The drive signal generation circuit 40 generates a drive signal COM. When the drive signal COM is applied to the piezo element, the piezo element expands and contracts. Ink is ejected from the corresponding nozzle of the head 31 according to the expansion and contraction of the piezo element.

  The detector group 50 includes a plurality of detectors that monitor the status of the printer 1. Detection results by these detectors are output to the controller 60.

  The controller 60 performs overall control in the printer 1. The controller 60 includes an interface unit 61, a CPU 62, and a memory 63. The interface unit 61 exchanges data with the computer CP. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. Note that the memory 63 of the present embodiment also stores a flag (hereinafter also referred to as area data) indicating a use area (described later). The CPU 62 controls each control target (paper transport mechanism 10, carriage movement mechanism 20, head unit 30, drive signal generation circuit 40, detector group 50) according to a computer program stored in the memory 63.

  In such a printer 1, the controller 60 intermittently ejects ink from the head 31 while moving the carriage 21 in the moving direction, and forms dots on the paper S, and the paper S in the transport direction. And a carrying process for carrying the paper repeatedly. As a result, dots are formed at positions different from the positions of the dots formed by the previous dot formation process, and a two-dimensional image is printed on the paper S.

<Overview of printer driver processing>
The above printing process starts when print image data is transmitted from the computer CP connected to the printer 1. The print image data is created by processing by the printer driver. Hereinafter, processing by the printer driver will be described with reference to FIG. FIG. 2 is an explanatory diagram of processing by the printer driver.

  The image data before color conversion processing is image data of 256 gradations in the RGB color space (corresponding to the first color space). The printer driver performs resolution conversion processing before color conversion processing so that the resolution of the input image data matches the printing resolution as necessary. For example, when the resolution of the image data received from the application program is 600 dpi × 600 dpi and the print resolution is 1200 dpi × 600 dpi, 600 dpi × 600 dpi is converted into 1200 dpi × 600 dpi.

  Next, the printer driver performs color conversion processing for converting image data in the RGB color space into image data in a CMYK color space (corresponding to the second color space) that is the same color space as the ink color. In this color conversion process, a table (color conversion lookup table: hereinafter referred to as “color conversion LUT”) in which gradation values of pixel data in the RGB color space and gradation values of pixel data in the CMYK color space are associated with each other is printed. This is done by referring to the driver. The image data after the color conversion process is image data of 256 gradations in the CMYK color space.

  After the color conversion process, the printer driver performs a halftone process for converting 256-gradation image data into 4-gradation image data that can be formed by the printer. In the halftone process, a dither method, a γ correction, an error diffusion method, or the like is used. The image data after the halftone process becomes print image data indicating the formation status (the presence / absence of dots, the size of the dots) of the dots constituting the print image.

  After the halftone process, the printer driver transmits print image data to the printer 1. When transmitting the print image data to the printer 1, the printer driver converts the order in which the pixel data of the print image data is arranged, if necessary, and command data necessary for controlling the printer 1 to the print image data. Perform command addition processing to be added to.

  The printer that has received the print image data ejects ink from each nozzle of the head 31 in accordance with the gradation value indicated by each pixel data of the print image data, and forms dots in the pixel area on the printed material. Accordingly, the printer 1 can print the image indicated by the print image data on the printing material.

  Note that the printer driver of the present embodiment improves the ink filling when the printer 1 prints an achromatic (for example, gray) image, so that not only the black ink (K) but also a chromatic color within an allowable range. Ink (CMY) is also controlled to be used (this process will be described later). An achromatic image is formed by superimposing K and CMY.

<Color conversion processing according to paper quality and its problems>
(Problem 1)
There is a regional difference in the paper quality of the substrate (paper S). For example, paper quality differs between Japan and Europe and America. For this reason, even when the same “paper type name (for example, plain paper)” is selected in the printer driver, the “paper quality” varies depending on the area difference, and the color of the printed image may be different. The color developability is “saturation” when CMY ink is applied, and depends on the surface residual rate of the ink pigment. For example, when the surface residual rate is large, color development is good, and conversely, when the surface residual rate is low, color development is poor.

  In particular, in the case of paper that is difficult to bleed (the surface residual ratio is large), the difference in color development (saturation) of color dots increases depending on the paper quality. For this reason, when there are many CMY when printing gray, a color shift tends to occur according to paper quality. For example, redness may appear depending on the paper quality.

  Therefore, when printing gray on such paper, it is desirable to reduce CMY and increase K. That is, a color conversion processing table (color conversion LUT) corresponding to the paper quality is required.

(Problem 2)
If a color conversion LUT for each paper quality is created in accordance with all the paper qualities in consideration of regional differences, many color conversion LUTs must be created, which is troublesome. Further, the total data amount of the color conversion LUT becomes enormous.

  Therefore, in this embodiment, the color conversion LUT is divided into a color table and a gray table, the color table is shared, and the gray table is prepared according to the paper quality.

<About color conversion processing>
As described above, the color conversion LUT is used in the color conversion process. The color conversion LUT is a table that defines the correspondence between data in one color space and data in another color space for a plurality of grid points. The color conversion LUT according to the present embodiment is a three-dimensional color conversion table, and the gradation value of the RGB color space is converted into a color space (CMYK color space in the present embodiment) corresponding to the ink used in the printer 1. Convert to key value.

  FIG. 3 is an explanatory diagram conceptually showing a color conversion LUT referred to for color conversion processing. The origin (0, 0, 0) in the figure is black (darkest part), and is a color space formed by the R axis, G axis, and B axis. Each of R, G, and B has 256 gradations (0 to 255), and the coordinates (255, 255, 255) are white. In the figure, an axis connecting the origin (0, 0, 0) and the coordinates (255, 255, 255) (that is, an area where RGB values are equal) is called a gray axis (corresponding to an achromatic area).

  All RGB image data can always be displayed in association with coordinate points in the color space. From this, if each of R-axis, G-axis, and B-axis is subdivided and a large number of grid points are set in the color space, each grid point can be considered to represent RGB image data. The gradation value of each color in the C, M, Y, K color space corresponding to the RGB image data can be associated with each grid point. The color conversion LUT can be considered as a three-dimensional number table in which gradation values of each color of C, M, Y, and K are stored in association with the grid points thus provided in the color space. If color conversion processing is performed based on the correspondence between the RGB image data stored in the color conversion LUT and the gradation data of each color of C, M, Y, and K, the RGB image data is converted into C, M , Y, and K can be quickly converted to gradation data.

  FIG. 4 is a conceptual diagram for explaining conversion when RGB image data is not at a grid point. In the figure, the RGB image data to be converted is indicated by black dots (hereinafter referred to as black dots). The black point is a coordinate (r, b, g) and is located between eight lattice points. In this case, weighting is performed according to the positional relationship between the black points and the surrounding lattice points (eight lattice points in the figure), and complementation is performed using the data of each lattice point. Note that there are various methods such as linear interpolation and spline interpolation in the interpolation calculation. As described above, even when the target RGB image data is not on the grid point, the color conversion processing can be performed on the gradation data of each color of C, M, Y, and K by performing complementation.

  In addition, the printer driver according to the present embodiment uses, as the color conversion LUT, a color table for a color area other than the gray axis, and two tables for the gray axis (a first gray table and a second gray table). It has. When comparing Japanese paper with Western paper, Western paper usually has a lower surface residual rate than Japanese paper (that is, poor color development). Therefore, the gray table corresponding to Japan (first gray table) has a smaller number of CMY and a larger K than the gray table corresponding to Europe and the United States (second gray table).

  5A to 5C are diagrams illustrating an example of each table of the color conversion LUT in the present embodiment. 5A is a color table, FIG. 5B is a first gray table, and FIG. 5C is a second gray table. As shown in the figure, each table is associated with a value (input value) on the color space (R, G, B) of the image data and an ink amount (output value) corresponding to the input value. ing. More specifically, in each table, the values of (C, M, Y, K) are associated with each lattice point shown in FIG. 3 (for every 32 gradations for each color of R, G, B).

  The color table is a conversion table for grid points excluding the gray axis (R = G = B). As can be seen from FIG. 3, the data amount of the color table (in other words, the number of grid points) is much larger than the data amount of the gray axis table. For this reason, if the color table is used in common regardless of the conditions, it is possible to save time and effort for creating the table and to suppress an increase in the amount of data compared to the case of creating the color table for each condition. be able to.

  The gray table is a conversion table for grid points on the gray axis (R = G = B). The first gray table (FIG. 5B) and the second gray table (FIG. 5C) have different CMYK gradation values for the same RGB gradation values. For example, when the image data is (R, G, B) = (32, 32, 32), the image data is color-converted with the first gray table (C, M, Y, K) = (63, 63). , 63, 245) and color conversion using the second gray table results in (C, M, Y, K) = (75, 75, 75, 225). Thus, even if the input RGB values are the same, the CMYK tone values after conversion by the two gray tables are different.

  In addition, the ratio of the change amount of the CMY and K tone values to the change amount of the RGB tone values (occurrence slope of each ink) is also different between the first gray table and the second gray table. For example, as shown in FIG. 5B and FIG. 5C, the change amount of the K gradation value is larger in the second gray table than in the first gray table with respect to the change in the input gradation value (RGB) ( That is, the slope of black ink generation is large). In addition, the change amount of each CMY tone value (CMY ink generation slope) in accordance with the change amount of the K tone value is also different between the first gray table and the second gray table. Thus, by preparing a plurality (two in this embodiment) of different gray tables and selecting and using them appropriately according to the printing conditions, it is possible to improve the reproducibility of gray (achromatic color).

FIG. 6 is a flowchart for explaining color conversion processing according to the first embodiment.
The memory 63 of the printer 1 stores in advance a region flag (region data) indicating a region in use (here, Japan and Europe and the United States). The printer driver of the computer CP includes the color table described above as the color conversion LUT and two gray tables (a first gray table and a second gray table).

  First, the printer driver of the computer CP acquires regional data from the memory 63 of the printer 1 (S101).

  Then, the printer driver determines whether or not the acquired regional data indicates Japan (S102).

  If it is determined that the regional data indicates Japan (YES in S102), the printer driver selects the first gray table (S103). Then, the gradation values of the pixel data constituting the RGB image data are converted into gradation values in the CMYK color space using the color table and the first gray table (S104: equivalent to the first color conversion process).

  For example, when the pixel data to be converted is on a grid point (see FIG. 3), color conversion is performed using the data of the grid point. At this time, if the grid point is not the gray axis, color conversion is performed using the color table, and if it is the gray axis, color conversion is performed using the first gray table.

  For example, when the pixel data to be converted is not on the grid, color conversion is performed by complementation using data of the surrounding grid (for example, eight grid points shown in FIG. 4). At this time, if at least one of the eight grid points is a gray axis grid point, color conversion is performed by complementation using the color table and the first gray table, respectively, and the eight grid points are assigned to the gray axis. If the grid point is not included, color conversion is performed by interpolation using only the color table.

  On the other hand, if it is determined that the regional data indicates other than Japan (Europe and America) (NO in S102), the printer driver selects the second gray table (S105). Then, the gradation values of the pixel data constituting the RGB image data are converted into gradation values in the CMYK color space using the color table and the second gray table (S106: equivalent to the second color conversion process).

  For example, when the pixel data to be converted is on a grid point (see FIG. 3), color conversion is performed using the data of the grid point. At this time, if the grid point is not the gray axis, color conversion is performed using the color table, and if it is the gray axis, color conversion is performed using the second gray table.

  For example, when the pixel data to be converted is not on the grid, color conversion is performed by complementation using data of the surrounding grid (for example, eight grid points shown in FIG. 4). At this time, if at least one of the eight grid points is a gray axis grid point, color conversion is performed by complementation using the color table and the first gray table, respectively, and the eight grid points are assigned to the gray axis. Is not included, color conversion is performed by interpolation using a color table.

  As described above, in the present embodiment, the color conversion LUT (color table) for the color area excluding the gray axis and two different color conversion LUTs for the gray axis (first gray table, second gray) Table).

  Then, the printer driver performs a color conversion process based on the color table and the first gray table in accordance with the region of use of the printer 1 (Japan, Europe and the United States) when performing the color conversion process, The process of performing color conversion is switched and executed based on the second gray table.

  Thereby, a change in image quality due to a difference in “paper quality (regional difference)” (difference in color development) can be suppressed. Therefore, the image quality can be improved. Further, only the gray table needs to be prepared according to “paper quality (regional difference)”. That is, since the color table for the color area excluding the gray axis is used in common, it is less time-consuming and the amount of increase in the table compared to the case where all color conversion LUTs are created for each printing condition. Can be suppressed.

In the present embodiment, there are two set use regions (region data) (Japan, Europe and the United States). However, the present invention is not limited to this, and may be three or more. In this case, a plurality of gray tables corresponding to the number of regional data may be created, and a table corresponding to the regional data may be selected during the color conversion process.
Further, for example, in the same region, two or more types of gray tables may be prepared according to the difference in paper quality, and a gray table suitable for the paper to be used may be selected. Even in this case, since the data amount of the gray table is small, an increase in the data amount can be suppressed as compared with the case where a plurality of color conversion LUTs are prepared.

=== Second Embodiment ===
In the second embodiment, the paper type can be selected on the UI of the printer driver. In the second embodiment, a plurality of gray tables are prepared according to the paper type.

Note that the configurations of the printer 1 and the computer CP, the contents of the color table, and the gray table are the same as those in the first embodiment, and a description thereof will be omitted.

  7A and 7B are diagrams illustrating an example of a UI screen for setting print conditions in the second embodiment.

  In the second embodiment, the user can select a print mode and a paper type on the UI screen of FIG. 7A. As the print mode, a high definition mode, a normal mode, and a speed priority mode can be selected. A4, A3, etc. can be selected as the paper size. As the paper type, as shown in FIG. 7B, plain paper (new paper) and plain paper (recycled paper) can be selected. A gray table is created for each of the two paper types. Even with the same plain paper, recycled paper is more likely to bleed than new paper. That is, recycled paper has poor color developability and a low surface residual rate. For this reason, even when CMY is used when printing gray, image quality deterioration (deviation from gray) is not noticeable. Therefore, in the second embodiment, a gray table (for example, a table similar to the second gray table in the first embodiment) with a large amount of CMY and a small amount of K is used for easily bleed paper (recycled paper). It corresponds.

  On the other hand, in the case of paper that is difficult to bleed (new paper), if CMY is used when printing gray, image quality deterioration is likely to be noticeable. Here, for plain paper (new paper) that does not easily spread, a gray table (for example, the same table as the first gray table of the first embodiment) with a larger K and a smaller CMY is used. Yes.

The printer driver according to the second embodiment selects a gray table to be used and performs color conversion processing according to the selection of the paper type on the UI screen in FIG. 7B.
Since processing other than this paper selection is the same as in the first embodiment, description thereof is omitted.

  As described above, in the second embodiment, a gray table is prepared according to the paper type selected on the UI screen. If the selected paper type is easy to bleed, a gray table with more CMY is selected, and if it is difficult to bleed, a gray table with more K is selected.

  Even in this case, image quality can be improved by selecting the gray axis table according to the paper type. Further, compared with the case where all color conversion LUTs are created for each printing condition, it is less time-consuming and the amount of increase in the table can be suppressed.

  In the above embodiment, there are two types of paper that can be selected on the UI screen: plain paper (new paper) and plain paper (recycled paper). However, the present invention is not limited to this. For example, glossy paper, matte paper, etc. May also be selectable. In this case as well, a gray table may be created according to each paper quality (ease of bleeding), and the gray table may be selected according to the selected paper.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
The printer 1 of the above-described embodiment is a serial printer, but is not limited thereto, and may be a printer of another type. For example, a line printer may be used.

<Discharge method>
In the above-described embodiment, ink is ejected using a piezoelectric element (piezo element). However, the method of ejecting ink is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<About print control device>
In the above-described embodiment, the color conversion processing is performed by the printer driver of the computer CP. However, the present invention is not limited to this. For example, using a printer capable of color conversion processing, the color conversion processing may be performed by the printer. In this case, the printer (the part that performs color conversion processing) corresponds to the print control apparatus.

<About printing conditions>
In the above-described embodiment, the gray table is selected according to the region and the paper type. However, the gray table is not limited to this, and the gray table may be selected according to other printing conditions (for example, printing speed and printing resolution). Good.

<About ink>
In the above-described embodiment, inks of four colors of cyan, magenta, yellow, and black are used. However, the present invention is not limited to this. For example, color inks other than four colors (orange ink, red ink, etc.) may be further used. In that case, a color table corresponding to the ink to be used may be prepared and used.

1 printer, 10 paper transport mechanism,
20 carriage movement mechanism, 21 carriage,
30 head units, 31 heads,
40 drive signal generation circuit,
50 detector groups,
60 controller, 61 interface part,
62 CPU, 63 memory,
CP computer, HC head controller

Claims (6)

A print control device that performs color conversion processing for converting image data in a first color space into image data in a second color space corresponding to the ink colors of the color ink and black ink ejected by the printing device,
A color table for converting gradation values of color areas excluding the achromatic color area of the first color space into gradation values of the second color space;
A first table for converting gradation values of the achromatic color region of the first color space into gradation values of the second color space;
A second table different from the first table, wherein the second table converts a gradation value of the achromatic region in the first color space into a gradation value of the second color space;
Depending on the printing conditions of the printing device,
A first color conversion process for converting gradation values of pixels constituting the image data of the first color space into gradation values of the second color space based on the color table and the first table; ,
A second color conversion process for converting gradation values of pixels constituting the image data in the first color space into gradation values in the second color space based on the color table and the second table; A printing control apparatus characterized by switching between the two. The print control apparatus according to claim 1,
A print control apparatus that switches between the first color conversion process and the second color conversion process in accordance with a paper quality of a substrate. The print control apparatus according to claim 1 or 2,
The first table and the second table have different black ink generation slopes.
A printing control apparatus characterized by that. The print control apparatus according to any one of claims 1 to 3,
Corresponding to the gradation value corresponding to the black ink when the gradation value of the achromatic color area of the first color space is converted by the first table and the black ink when converted by the second table The gradation value to be
A printing control apparatus characterized by that. A color table that converts gradation values of the color area excluding the achromatic area of the first color space into gradation values of the second color space corresponding to the ink colors of the color ink and the black ink discharged from the printing apparatus; A first table for converting a gradation value of the achromatic color region of the first color space into a gradation value of the second color space; and a second table different from the first table, wherein the first color A second table for converting the gradation value of the achromatic color region of the space into the gradation value of the second color space, and converting the image data of the first color space into the image data of the second color space. In the print control device that performs color conversion processing,
Depending on the printing conditions of the printing device,
A first color conversion process for converting gradation values of pixels constituting the image data of the first color space into gradation values of the second color space based on the color table and the first table; ,
A second color conversion process for converting gradation values of pixels constituting the image data in the first color space into gradation values in the second color space based on the color table and the second table; A program characterized by switching and executing. An image processing method for performing color conversion processing for converting image data in a first color space into image data in a second color space corresponding to the ink colors of color ink and black ink discharged from a printing apparatus,
A color table for converting gradation values of color areas excluding the achromatic color area of the first color space into gradation values of the second color space;
A first table for converting gradation values of the achromatic color region of the first color space into gradation values of the second color space;
A second table different from the first table, wherein the second table converts the gradation value of the achromatic color region of the first color space into the gradation value of the second color space;
Depending on the printing conditions of the printing device,
A first color conversion process for converting gradation values of pixels constituting the image data of the first color space into gradation values of the second color space based on the color table and the first table; ,
A second color conversion process for converting gradation values of pixels constituting the image data in the first color space into gradation values in the second color space based on the color table and the second table; An image processing method characterized in that the switching is performed.

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