JPH11314382A - Ink jet recorder and recording medium therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a desired high image quality at the time of bidirectional recording in halftone recording system by suppressing nonuniformity of color. SOLUTION: The ink jet recorder comprises an LUT memory means 201 storing at least two LUTs, means 202 for selecting one LUT among LUTs stored in the memory means 201, means 203 for separating an input image data into a high gray level image data and a low gray level image data based on a selected LUT, and means 206 for binarizing a gray image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printing head having a plurality of nozzle rows for discharging dark ink and a plurality of nozzle rows for discharging light ink, and different from the plurality of nozzle rows on the printing head. The present invention relates to an ink jet recording apparatus that performs recording on recording paper by discharging inks of different colors and different densities.

[0002]

2. Description of the Related Art With the spread of information devices such as word processors and computers, as one of the recording devices of those devices,
2. Description of the Related Art Recording apparatuses that perform digital image recording using a recording head based on an ink-jet method are becoming widespread. Further, with the advancement of the performance and accuracy of these information devices, demands for higher image quality and color in printing apparatuses have been increasing.

As one of the techniques for improving the image quality in such a printing apparatus, there has been proposed a density recording method using dark and light inks of similar colors having different densities.

In this method, by recording the highlight portion with light ink and recording the high density portion with dark ink, the granularity of the highlight portion is improved and the image quality of the high density portion is maintained. Further, in the halftone portion, a delicate color can be expressed by simultaneously recording the dark ink and the light ink.

[0005] However, in the density recording method,
For example, when the density separation is performed using the LUT as shown in FIG. 3 and the input density level of the image exceeds 127, the sum of the ejection amounts of the ink drops of the dark ink and the light ink exceeds 100%, On the other hand, when only dark ink is used, for example, the LUT becomes an LUT as shown in FIG. 5, and the maximum amount of ejected ink drops is 100%. That is, in the light and dark recording method, the ejection amount of ink droplets in the halftone portion is increased as compared with the recording method using only the dark ink. There is a problem that causes a problem when the amount of ejected ink droplets is large, such as generation of a fixing delay due to a delay in drying time. Another problem is that specific density unevenness occurs depending on the overlapping ratio of dark and light inks, thereby deteriorating image quality.

As a solution to such a problem, in a conventional density recording type ink jet recording apparatus, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-183240, ink droplets of similar colors having different densities are applied to the same pixel. There has been provided a method of enabling recording not to be performed and preventing deterioration of recorded image quality caused by overlapping of dark ink and light ink.

On the other hand, Japanese Patent Application Laid-Open No.
There is a recording method called “interlace method” disclosed in, for example, JP-A-1301.

FIG. 8 is an explanatory diagram showing an example of recording by the interlace method. The following parameters are used as parameters for defining the recording method. N: Number of nozzles [pieces] k: Nozzle pitch [dots] D: Nozzle density [pieces / inch] L: Sub-scan feed amount [dots] or [inch] w: Dot pitch [inch] Number of nozzles N [pieces] , The number of nozzles used to form dots. In the example of FIG. 8, N = 3. The nozzle pitch k [dot] indicates how many nozzle pitches in the print head are equal to the print pixel pitch (dot pitch w). In the example of FIG. 8, k = 2. The nozzle density D [pieces / inch] indicates how many nozzles are arranged per inch in the nozzle array of the print head. The sub-scan feed amount L [dot] or [inch] indicates the distance moved by one sub-scan.
The dot pitch w [inch] is a dot pitch in a recorded image. Generally, w = 1 / (D · k), k
= 1 / (D · w) holds.

In FIG. 8, circles including two-digit numbers indicate dot recording positions. As shown in the legend of FIG. 8, among the two-digit numbers in the circles, the numbers on the left indicate the nozzle numbers, and the numbers on the right indicate the recording order (recorded in any number of main scans). Taka).

In the interlaced printing shown in FIG. 8, the nozzle pitch of adjacent nozzles is set to an integer of 2 or more, and the number of nozzles N and the nozzle pitch k are selected to be integers having a prime relationship. . The sub-scan feed amount L is set to a constant value given by N / (D · k).

The interlaced printing has the advantage that variations in nozzle pitch and ink ejection characteristics can be dispersed on the printed image. Therefore, even if there is a variation in the nozzle pitch and the ejection characteristics, these effects can be reduced and the image quality can be improved.

[0012]

However, even in such a prior art example, especially in the case of performing bidirectional printing for high-speed printing, ink droplets in the forward and backward passes in the main scanning direction of the print head. The difference in the order of overlapping, the difference in the ink drying time depending on the recording position in the forward path and the return path, and the like, cause the density unevenness caused by the difference in the bleeding of the ink droplets. There's a problem.

For example, FIG. 9 is a diagram showing an example in which bidirectional recording is performed in interlaced recording when N = 5 and k = 4. In FIG. 9, two-digit circles without diagonal lines indicate dot recording positions on the outward path in the main scanning direction, and two-digit circles with diagonal lines indicate dot recording positions on the return path in the main scanning direction.

In FIG. 9, when the end point of the seventh scan is seen, dots start to be continuously connected after the dot recording position indicated by 41 circles. Therefore, image data is indicated by 41 circles. It is recorded after the recording position of the dot.

As a feature of recording by the interlace method, dots are discrete (the term discrete here means that there is no dot already recorded in the sub-scanning direction at the recording position of the dot to be recorded). And the portion that is recorded continuously (here, continuous means that there is already recorded dots in the sub-scanning direction of the recording position of the dot to be recorded). Can occur.

For example, in FIG. 9, 41, 51, 52,
The dots at the recording positions of the dots indicated by circles 53, 54,... Are discretely recorded, and the dots indicated by the circles 32, 23, 14, 42, 33, 24,. Will be recorded continuously.

Further, when bidirectional printing is performed, dots at the printing positions of dots indicated by circles 41, 51, 53,... Are discretely printed on the outward path in the main scanning direction. ... The dots at the recording positions of the dots indicated by circles are discretely recorded on the return path in the main scanning direction.

Therefore, when interlaced bidirectional printing is performed, an area where dots are continuously printed from dots printed discretely on the outward path in the main scanning direction (for example, a region surrounded by a dotted line in the drawing). An area A) and an area where dots are continuously recorded from dots discretely printed on the return path in the main scanning direction (for example, an area B surrounded by a dotted line in the drawing) are mixed.

Here, in the ink jet recording apparatus, the line width to be recorded by one scanning is set to be larger than the theoretical line width of the recording resolution so that adjacent lines overlap each other. Thus, white stripes in a solid portion caused by the characteristics of the recording head and the accuracy of recording paper conveyance are prevented. Furthermore, in the case of performing color recording, the color of the ink may change due to factors such as the overlapping region and the order of the ink droplets and the difference in the drying time with the next overlapping ink droplet due to the characteristics of the ink. The tint created by a previously recorded ink drop tends to dominate the tint that is to be created by the next successively printed ink drop.

FIG. 10 shows K, C (Cyan), Lc
(Light Cyan), M (dark Magenta), Lm (light M)
3A and 3B are diagrams illustrating the nozzle arrangement of the print head when performing color printing using six dark and light inks of Y, viewed from the nozzle plate side. In the nozzle rows of each color, the nozzle positions in the sub-scanning direction match. When printing is performed using such a print head, ink droplets of each color are ejected in the order of K, C, Lc, M, Lm, and Y in the outward path in the main scanning direction to form an image. Is Y,
An image is formed by ejecting ink droplets of each color in the order of Lm, M, Lc, C, and K. That is, the order in which the colors overlap in the forward path and the return path in the main scanning direction is different.

Therefore, using such a recording head,
As described above, in the case where the interlaced bidirectional printing is performed, an area where dots are continuously printed from dots discretely printed on the outward path in the main scanning direction, and a return path in the main scanning direction. In the above, a color difference occurs in an area where dots are continuously recorded from dots recorded discretely, and specific color unevenness occurs.

Therefore, an object of the present invention is to provide different LUs for unidirectional recording and bidirectional recording.
An object of the present invention is to provide an ink jet recording apparatus which can perform color image processing using T to reduce color unevenness which is likely to occur during bidirectional recording and obtain desired high image quality.

[0023]

According to the present invention, there is provided an ink jet recording apparatus comprising: a recording head having a plurality of nozzle rows for discharging dark ink and a plurality of nozzle rows for discharging light ink; and a computer. An ink jet recording apparatus used for recording on recording paper using the recording head, wherein the LUT storage means is capable of storing at least two or more LUTs, and the LUT storage is performed based on recording direction designation information. LUT selection means for selecting one LUT from LUTs stored in the means, and a grayscale image for separating input image data into dark image data and light image data based on the LUT selected by the LUT selection means Processing means for performing a binarization process on each of the dark image data and the light image data Wherein the binarized image data is recorded in an interlaced manner, and each of the LUTs selected by the LUT selection means performs recording with the same density. An LUT selected for unidirectional printing so that the sum of the ejection amounts of the dark ink and the light ink drops required for the bidirectional printing is smaller than the LUT selected for unidirectional printing. The LUT selected at the time of the bidirectional recording is such that the input density level is 256 from 0 to 255.
At the stage, when the input density level is in the range of 0 to 127, both the dark ink and the light ink are used,
When the input density level exceeds 127, the LUT uses only dark ink.

The recording medium according to the present invention is used in a computer for controlling an ink jet recording apparatus having a recording head having a plurality of nozzle rows for discharging dark ink and a plurality of nozzle rows for discharging light ink. A computer-readable recording medium recording a computer program for performing recording on a recording paper using a recording head, wherein the computer program is
(I) a function of having at least two LUTs and selecting one of the LUTs based on the recording direction designation information; and (ii) converting the input image data into a dark image based on the selected LUT. And a function of performing binarization processing after separation into data and light image data.
Is the sum of the ejection amounts of the dark ink and the light ink required for printing at the same density, and the LUT selected for bidirectional printing from the LUT selected for unidirectional printing.
The LUT selected in the bidirectional recording is within the range of the input density level 0 to 127 when the input density level is set to 256 levels of 0 to 255. Is an LUT that uses both dark and light inks and uses only dark ink when the input density level exceeds 127.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 is a diagram illustrating a recording head and a recording operation of an ink jet recording apparatus according to one embodiment of the present invention.

The recording head 101 is fixed to a carriage 102 and is conveyed along a guide shaft 109 in a main scanning direction shown by arrows A and B by a carriage driving belt 103 driven by a carriage driving motor 104. The recording paper 107 is transported in the direction of arrow C by a transport roller 108 driven by a transport roller drive motor (not shown). Further, the ink forming the recording pixels is supplied from the ink supply tank 105 to the recording head 101 through the ink supply pipe 106.

The recording head 101 is an ink jet recording head using a piezoelectric element, and has a plurality of nozzles arranged in an arbitrary matrix or in one row in the sub-scanning direction (the direction of the arrow C).

FIG. 6 is a diagram showing the nozzle arrangement of the recording head 101 used in this embodiment. The recording head 101 has K, C (dark cyan), L in the main scanning direction.
There are six nozzle rows of c (light cyan), M (dark magenta), Lm (light magenta) and Y, and each of the 32 nozzle rows is arranged at a 1/90 inch pitch in the sub-scanning direction. Nozzle group. In this embodiment, in order to perform interlaced printing, printing is performed using 31 nozzle groups out of the 32 nozzle groups.

Next, the operation will be described. Prior to the printing operation, the printing head 10
The recording paper 107 is fed to a position facing the nozzle surface of No. 1. The recording head 101 selectively ejects ink droplets from the nozzles of the recording head 101 in synchronization with the scanning of the carriage 102 and strikes ink droplets on the recording paper 107, and prints characters and images based on the recording data on the recording paper 107. It is formed at a predetermined position. At the end of this scanning, the recording paper 10
7 is transported in the sub-scanning direction by the transport roller 108. By repeating this operation, desired characters and images are formed on the recording paper.

The amount of movement of the recording head 101 in the main scanning direction and the amount of conveyance of the recording paper 107 in the sub-scanning direction are determined according to the recording resolution. In this embodiment, for example, when performing interlaced bidirectional printing at a resolution of 360 dpi, the print head 101 scans 1 /
The ink droplets are selectively ejected every time it moves 360 inches. The recording paper 107 is moved by the conveyance roller 108 at the end of the main scanning in the main scanning direction A of the recording head 101.
By 31/360 inches. Next, the recording head 101 selectively ejects ink droplets each time it moves 1/360 inch while being scanned in the main scanning direction B by the carriage 102. Further, the recording paper 107 is conveyed by the conveying roller 108 at a rate of 31/360 inches when the scanning of the recording head 101 in the main scanning direction B is completed.

As described above, the recording head 101 ejects an appropriate amount of ink onto the recording medium in the two-way scanning in the main scanning direction A and the main scanning direction B. By repeating a series of operations of being conveyed, bidirectional printing is performed by the interlace method, and desired 360 dpi print data is formed on the recording paper 107.

For unidirectional printing at a resolution of, for example, 360 dpi, the print head 101 is driven by the carriage 102 while scanning in the main scanning direction A.
/ 360 inches of ink droplets are selectively ejected every time it moves. The recording paper 107 is moved by the conveyance roller 108 at the end of the main scanning in the main scanning direction A of the recording head 101.
By 31/360 inches. The recording head 101 is moved in the main scanning direction B by the carriage 102.
And then returned to the recording start position, and again scanned by the carriage 102 in the main scanning direction A for 1
/ 360 inches of ink droplets are selectively ejected every time it moves.

As described above, the recording head 101 ejects ink droplets onto the recording medium in the scanning in the main scanning direction A, and the recording paper 107 is conveyed only when the scanning in the main scanning direction A is completed. By repeating the operation of
Perform unidirectional recording by the interlace method, and
07, desired 360 dpi print data is formed.

When bidirectional printing is performed at a resolution of, for example, 720 dpi, the printhead 101 is scanned by the carriage 102 in the main scanning direction A for one time.
The ink droplets are selectively ejected each time the ink droplet moves by 720 inches. The recording paper 107 is moved by the conveyance roller 108 at the end of the main scanning in the main scanning direction A of the recording head 101.
Is conveyed by 31/720 inch. Next, the recording head 101 selectively ejects ink droplets each time it moves 1/720 inch while being scanned in the main scanning direction B by the carriage 102. Further, the recording paper 107 is conveyed by the conveying roller 108 at a rate of 31/720 inch at the end of the scanning of the recording head 101 in the main scanning direction B.

As described above, the recording head 101 ejects an appropriate amount of ink onto the recording medium in the bidirectional scanning in the main scanning direction A and the main scanning direction B. By repeating a series of operations of being conveyed, bidirectional printing is performed by the interlace method, and desired 720 dpi print data is formed on the printing paper 107.

FIG. 2 is a block diagram showing the configuration of an ink jet recording apparatus according to one embodiment of the present invention. The inside of the broken line in the figure indicates the configuration of the ink jet recording apparatus according to the present embodiment.

In the ink jet recording apparatus according to this embodiment, the LUT storage means 201 capable of storing at least two or more LUTs and the LUT storage means 201 are stored based on the recording direction designation information 221 sent from the external device 220. LUT selecting means 202 for selecting one LUT from among the LUTs, and gray image processing means 20 for separating input image data 222 sent from the external device 220 into gray image data based on the selected LUT.
3 and a binarization processing unit 206 that binarizes the respective image data of the dark image data 204 and the light image data 205 separated by the gray image processing unit 203
Consists of

In the present embodiment, the input image data 222 sent from the external device 220 includes K, C, M, and Y
The ink used in this embodiment is four dark inks of K, C, M, and Y, and light inks Lc and Lm of similar colors of C and M. Since the input image data 222 has two colors, the image data of C and M in the input image data 222 are separated into dark image data and light image data of C, Lc, M, and Lm, and are recorded using dark and light inks. The Y input image data is recorded using only dark ink. Therefore, the LUT storage means 201
LUT for dark and light ink selected during unidirectional printing
210 and a LUT 211 for dark and light ink selected during bidirectional printing, and an LUT 212 for dark ink
The UT is stored, and one of the LUTs is selected based on the recording direction designation information 221.

Here, the LU used in this embodiment is
T will be described. FIG. 3 is a diagram showing a graph of the input density level of the LUT 210 selected at the time of unidirectional printing versus the ink droplet ejection amount.

According to the LUT 210, the light ink is
When the input density level is 127, the ejection amount of the ink droplet becomes 70% of the maximum, and the ink droplet is ejected over the entire area. The dark ink has an input density level of 100.
The ejection of ink droplets is started from a density level exceeding the above, and when the input density level is 255, the ejection amount of ink droplets is continuously increased so that the ejection amount of ink droplets becomes 100%. Looking at the sum of the ejection amounts of the dark ink and the light ink, the ejection amount of the ink droplet exceeds 100% from the density level where the input density level exceeds 127. Become.

FIG. 4 shows an LUT selected during bidirectional recording.
FIG. 11 is a diagram illustrating a graph of an input density level 211 and the ejection amount of ink droplets 211. According to the LUT 211, when the input density level is 63, the ejection amount of the ink droplet becomes 40% of the maximum when the input density level is 63, and when the input density level is 127, the ejection amount of the ink droplet becomes 0%. For dark ink, the ejection of ink droplets is started from a density level where the input density level exceeds 40, and the input density level becomes 255.
In this case, the ink droplets are continuously ejected so that the ejection amount of the ink droplets becomes 100%, and the ink droplets are ejected. Looking at the sum of the ink droplet ejection amounts of the dark ink and the light ink, when the input density level is the maximum of 255, the ejection amount of the ink droplet becomes 100% of the maximum. The sum of the quantities does not exceed 100%.

FIG. 5 shows an LUT when only dark ink is used.
FIG. 12 is a diagram illustrating a graph of the input density level versus the ejection amount of the ink droplet at 212. According to the LUT 212, when the input density level is 255, the dark ink is continuously increased so that the ejection amount of the ink droplet becomes 100%, and the ink droplet is ejected.

Next, the recording operation in this embodiment will be described. The LUT selection unit 202 provides one of the LUTs stored in the LUT storage unit 201 to the grayscale image processing unit 203 based on the recording method designation information 221 sent from the external device 220. For example, if the recording direction designation information 221 designates unidirectional recording, the LUT 21
If the recording direction designation information 221 specifies bidirectional recording, the LUT 211 is selected and provided to the grayscale image processing means 203.

The grayscale image processing means 203 is
A process is performed to separate the input image data 222 sent from 0 into gray image data based on the LUT selected by the LUT selection means 202.

For example, when the LUT 210 is selected, image data having an input density level of 127 is separated into dark and light image data in which 25% of dark ink droplets and 75% of light ink droplets are ejected. In this embodiment,
Assuming that the density level when the ink droplet ejection amount reaches 100% is 255, the density level calculated from the ink droplet ejection amount is the output density level of the image data to be recorded. That is, 25% of the dark ink droplets
The output density level at the time of ejection is 255 × 25% = 64, and the output density level at the time of 75% ejection of light ink droplets is 255 × 75% = 191. The output density levels thus calculated are stored in the dark image data storage unit 204 and the light image data storage unit 205 as gray image data.

For example, when the LUT 211 is selected, the image data of the input density level 127 is separated into dark and light image data such that dark ink 55% and light ink 0%. That is, the output density level of the dark ink is 25
5 × 55% = 140, output density level of light ink is 25
5 × 0% = 0, and the respective output density levels correspond to the dark image data storage unit 204 and the light image data storage unit 2
05 is stored. The binarization processing unit 206 includes the dark image data storage unit 204 and the light image data storage unit 2.
A binarization process is performed on each of the gray image data stored in the image data 05.

Here, the binarization processing means 206 in this embodiment uses a binarization processing method using error diffusion processing as the binarization processing means. The error diffusion process includes:
When the current pixel of interest is binarized by the set threshold value, an error between the density value of the pixel of interest and the binarized result is set to, for example, a peripheral pixel indicated by an arrow as shown in FIG. This is a method of spreading and compensating, and is generally used as a method of obtaining a result of a high-quality binarization process.
This is a value processing method.

In this embodiment, the recording data subjected to the binarization processing is sent to the recording head driving means 230 and recorded on recording paper. Specifically, the recording head driving unit 230 receives the binarized recording data and generates a head driving signal for performing recording. Thereafter, the head driving unit 230 allocates and applies the generated head driving signal to each nozzle on the recording head 101.

The recording head 101 forms a desired image on the recording paper 107 by discharging ink droplets in accordance with the head driving signal applied by the head driving means 230.

The embodiment of the ink jet recording apparatus according to the present invention has been described above. The configuration described in the above embodiment is replaced with software, the program is formed on a computer-readable recording medium, and the program is executed on a computer. It is good also as a form. Also, L
The UT is not limited to this, and can be provided for each color. Also, the recording head has been described as an example using an ink jet recording head of a type using a piezoelectric element,
The present invention is not limited to this, and a type using a heating element, that is, a so-called bubble jet type ink jet recording head can also be used.

[0051]

According to the present invention, it is possible to reduce color unevenness that occurs during bidirectional printing in a grayscale printing method by using an ink jet printing apparatus configured to select different LUTs during unidirectional printing and bidirectional printing. It is possible to perform high-speed recording without deteriorating the image quality.

[Brief description of the drawings]

FIG. 1 is a schematic view of an ink jet recording apparatus according to the present invention.

FIG. 2 is a block diagram showing components of the ink jet recording apparatus of the present invention.

FIG. 3 is a graph showing the relationship between the input density level of the LUT and the ejection amount of ink droplets during unidirectional printing according to the present invention.

FIG. 4 is a graph showing the relationship between the input density level of the LUT and the ejection amount of ink droplets during bidirectional printing according to the present invention.

FIG. 5 is a graph showing the relationship between the input density level of the LUT and the ejection amount of ink droplets when only the deep ink of the present invention is used.

FIG. 6 is a diagram showing a nozzle arrangement of the print head 101 according to the embodiment of the present invention.

FIG. 7 is a diagram showing a target pixel and its peripheral pixels in an error diffusion process according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating recording by an interlace method.

FIG. 9 is a diagram illustrating a case where bidirectional printing is performed in interlaced printing.

FIG. 10 is a diagram illustrating a nozzle arrangement of a recording head when performing color recording using dark and light inks.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Recording head 102 Carriage 103 Carriage drive belt 104 Carriage drive motor 107 Recording paper 108 Conveyance roller 109 Guide shaft 201 LUT selection means 202 LUT storage means 203 Gray image processing means 204 Dark image data storage means 205 Light image data storage means 206 Binary LU 210 for dark and light ink selected during unidirectional printing
T 211 LU for dark and light ink selected during bidirectional printing
T212 LUT 230 for thick ink Printhead driving means

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/23 101 B41J 3/12 G

Claims (7)

[Claims] 1. A print head having a plurality of nozzle rows for discharging dark ink and a plurality of nozzle rows for discharging light ink, wherein different colors and different densities are respectively obtained from the plurality of nozzle rows on the print head. 2. Description of the Related Art In an ink-jet recording apparatus that performs recording on recording paper by discharging ink, a table (hereinafter referred to as a LUT (Look Up Table)) that determines the ejection amount per unit area of dark ink and light ink with respect to an input density level. LUT storage means capable of storing at least two or more LUTs), LUT selection means for selecting one LUT from the LUTs stored in the LUT storage means based on recording direction designation information, Based on the LUT selected by the LUT selection means, the image data is converted into dark image data and light image data. An ink jet recording apparatus characterized by comprising a gray image processing means for separating, and binarization means for applying a binarization processing to the dark image data and light image data each image data, to the. 2. The ink jet recording apparatus according to claim 1, wherein said binarized image data is recorded in an interlace system. 3. The LUTs selected by the LUT selection means each store the sum of the ink droplet ejection amounts of dark ink and light ink required for printing at the same density.
2. The ink jet printing apparatus according to claim 1, wherein the LUT selected during bidirectional printing is smaller than the LUT selected during unidirectional printing. 4. An LU selected during the bidirectional recording
T indicates that when the input density level is set to 256 levels of 0 to 255, both the dark ink and the light ink are used within the range of the input density level 0 to 127, and when the input density level exceeds 127, 2. The ink jet recording apparatus according to claim 1, wherein only the dark ink is used. 5. A computer for controlling an ink jet recording apparatus having a recording head having a plurality of nozzle rows for discharging dark ink and a plurality of nozzle rows for discharging light ink, wherein recording is performed using the recording head. A computer-readable recording medium having recorded thereon a computer program for performing recording on paper, wherein the computer program has (i) at least two or more LUTs, and stores the LUT in the LUT based on recording direction designation information. The computer has a function of selecting one LUT and a function of (ii) separating input image data into dark image data and light image data based on the selected LUT and then performing binarization processing. A computer-readable recording medium to be realized. 6. The LUT to be selected, in which the sum of the ejection amounts of ink drops of dark ink and light ink required for printing at the same density is determined in bidirectional printing from the LUT selected in unidirectional printing. 6. The computer-readable recording medium according to claim 5, wherein the number of LUTs to be selected is a smaller number of LUTs. 7. An LU selected during the bidirectional recording
T indicates that when the input density level is set to 256 levels of 0 to 255, both the dark ink and the light ink are used within the range of the input density level 0 to 127, and when the input density level exceeds 127, L using only dark ink
The computer-readable recording medium according to claim 5, wherein the recording medium is a UT.