JP2641252B2 - Liquid jet recording method and liquid jet recording apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid jet recording method and a liquid jet recording apparatus, and more particularly, to recording on a sheet-like recording medium (hereinafter, referred to as paper) including paper, a thin plastic plate, and the like. The present invention relates to a liquid jet recording method and a liquid jet recording apparatus for improving the fixing property after the fixing.

[Prior Art] A liquid jet recording apparatus, for example, an apparatus for recording characters such as figures and other general images using an ink jet head such as an ink jet printer or an ink jet recorder employs an ink droplet discharging means provided on the ink jet head. It is configured to drive based on the recording information and record an image pattern by a recording head formed by each ink droplet attached to the recording sheet.

In such an ink jet recording method, since dots are formed by liquid ink droplets, the fixability after recording may be a problem.

That is, if the fixing property is poor, for example, an undried formed image appears on the second sheet, the formed image is rubbed when the second sheet is conveyed after recording, and furthermore, the operator touches the sheet. Various inconveniences occur, such as the recorded paper being stained by the rubbing of the finger when handling.

Therefore, conventionally, as a method for improving the fixing property of a formed image, a recording sheet after recording is heated to promote drying, a sheet conveyance amount after recording and discharged is increased, or an ink discharge drive is performed. A method has been used in which the dot width is reduced by reducing the pulse width of the voltage.

[Problems to be Solved by the Invention] By the way, recently, in order to improve recording quality and image resolution, the number of dots per character tends to be increased. Furthermore, there is a tendency to advance to 32 dots and 48 dots.

As described above, when the number of recording dots increases, it is difficult to improve the fixability only by the conventional drying acceleration method as described above. In particular, so-called solid printing, block printing, white (black and white reversal) printing or In the case of a pattern having a large number of recordings with a high dot density, such as a bit image, there is a problem that the fixing property is reduced and a high recording quality cannot be maintained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and provides a liquid jet recording method and a liquid jet recording apparatus that can improve fixability corresponding to dot density while ensuring high recording quality. Aim.

[Means for Solving the Problems] For this purpose, according to the present invention, there is provided a pixel of interest of print data, and a judging means for judging whether or not pixels above, below, left, and right of the pixel of interest are black pixels. When the discriminating unit determines that the target pixel and the upper, lower, left, and right pixels of the target pixel are black pixels, the recording data is thinned by setting the target pixel to a white pixel. It is characterized by having thinning means and recording means for performing recording by ejecting a liquid to a recording medium based on the print data thinned out by the thinning means.

A determining step of determining whether a target pixel of the print data and pixels above, below, left, and right of the target pixel are black pixels; and determining the target pixel and the target pixel by the determining step. When the upper, lower, left, and right pixels are determined to be black pixels, a thinning step of thinning print data by setting the pixel of interest to a white pixel, and a print data thinned by the thinning step. A recording step of performing recording by ejecting a liquid to a recording medium based on the recording step.

[Operation] According to the above configuration, it is determined whether the pixel of interest and the pixels above, below, left, and right in the thinning process are black pixels, and all of the pixels are black pixels. in case of,
Since the process in which the pixel of interest is a white pixel is performed, at least one side is a white pixel, and black pixels forming the contour of a character or the like are not thinned out.
In addition, it is possible to thin out a predetermined ratio only inside or outside the contour.

EXAMPLES The present invention will be described below in detail with reference to the drawings.

FIG. 9 is a longitudinal sectional view of an ink jet recording apparatus suitable for carrying out the liquid jet recording method (ink jet recording method) according to the present invention.

In FIG. 9, a sheet 4 is fed from a direction indicated by an arrow to a sheet feed mechanism including a feed roller 1 and pinch rollers 2 and 3 which are removably pressed against a lower peripheral surface of the feed roller 1, and a platen 5 and an ink jet recording head 6 are provided. While the paper 4 is being conveyed at a predetermined pitch through the recording unit during this period, images such as characters and graphics are formed on the paper 4. Then, the recording paper 4 is discharged upward through the discharge roller 7.

The illustrated recording device (printer) is of a serial type, and has an ink jet recording head 6 having ink ejection ports.
Is mounted on a carriage 9 that reciprocates in the left-right direction along the front surface of the platen 5 (paper 4) along the guide shaft 8.

In this manner, an ink jet recording apparatus is configured to perform recording by forming an image composed of dot patterns of ink droplets on the paper 4 based on image data sent from a host device such as a computer serving as an image data supply source. You.

In the ink jet recording apparatus shown in FIG. 9, a fixing heater 11 for heating the paper 4 and promoting drying of the recording dots is arranged in a range where a portion immediately after recording on the back side of the platen 5 passes.

In the recording apparatus shown in FIG. 9, when recording is performed in a recording mode or a character having a large number of recording dots, dots are thinned out and recording is performed so that fixability after recording is improved.

Here, the characters include all types of images including graphics and pixels in addition to normal characters.

For such an ink jet recording method, dot thinning information corresponding to each character font data is stored in a character generator 26 described later in a memory, and dot thinning is performed based on the thinning information during recording. In addition, a method of improving the fixability after recording while ensuring high recording quality by performing appropriate thinning set in advance for each character is implemented.

Further, a recording method in which the dot thinning rate is changed by a manual operation such as turning on / off a DIP switch and the recording density is changed as desired can be implemented.

FIG. 10 is a block diagram showing an example of a control system suitable for carrying out the ink jet recording method according to the present invention.

In FIG. 10, the MPU 21 for controlling the inside of the recording device
Connected to the host computer etc. via / O port 22,
Receive recording commands and recording data.

The MPU 21 has an address bus 23 and a data bus 24
A program or the like corresponding to a control procedure described later with reference to FIGS. 1 to 3, 5, or 8 is stored in the RO.
M25, character generator (CG) 26 in which font data of each character is stored, a temporary storage area for a print buffer and CG, and a work area such as a counter
RAM 27, I / O port 28 for transmitting control signals to various operating parts and receiving detection signals from various sensors,
Also, a head controller 29 for controlling the ink jet recording head 6 is connected.

In the illustrated example, the carriage 9 is connected via the I / O port 28.
, A paper feed motor 31 for driving the feed roller 1, a DIP switch 32 for setting thinning printing and its type, and the like, and turning on / off the fixing heater 11 in accordance with the setting conditions.
A fixing heater control circuit 34 to be turned off and the like are connected.
The fixing heater control circuit 34 controls the driving current from the power supply 35 to the fixing heater 11 based on the heater temperature and the like.

FIG. 1 is a flowchart showing an example of an operation procedure when the method of the present invention is performed in the above-described ink jet recording apparatus.

In FIG. 1, when the power is turned on, first, a step is performed.
In S1, the control circuit 21, the inside of the RAM 27, and various operation units are initialized, and the operations of the ROM, RAM, carriage, and the like are checked, and the process proceeds to the next step S2, where the fixing heater 11 is turned on.

Next, the process proceeds to step S3, where it is determined whether or not the paper 4 is supplied by the paper absence sensor provided at an appropriate portion on the paper transport path.

If the paper 4 has been supplied, the process proceeds to step S4 to turn on the online lamp indicating completion of connection with the host machine such as a computer, and outputs an interface signal indicating completion of data reception preparation in step S5. Proceed to and receive the data.

When the data is received, the process proceeds to step S7, where the carriage 9
The recording head 6 is driven while moving the paper, and one line of recording is performed on the paper 4. When the recording of one line is completed, the paper feed motor 31 is driven to convey a predetermined amount of paper in step S8. Perform reverse driving of the motor 30 and
Proceeding to S9, it is determined whether or not the paper feed motor 31 and the carriage motor 30 have stopped.

If these motors are not stopped in step S9, the operation of step S8 is continued.

If it is confirmed that the motor has stopped at step S9, step S4
Repeat the above operation and record the next line.

Further, recording is performed on the entire sheet while repeating the above operation.

If it is determined in step S3 that there is no paper, step S1
At 0, an appropriate notification means, for example, turning on a paper lamp,
Error processing is performed in the next step S11. Subsequently, the process proceeds to step S12, where it is determined whether or not the error has been cleared. If not, the determination in step S12 is performed at regular intervals.

When the error is released, the process returns to step S3 to determine the presence or absence of the sheet 4, and repeats the error processing until the sheet is supplied.

FIG. 2 is a flowchart showing an example of a detailed procedure of the recording operation in step S7 in FIG.

In FIG. 2, when data is received in step S6 and the recording operation is started, first in step S101, a font address is designated from the recording data code stored in the input buffer area of the RAM 27 transferred from the host,
Proceeding to the next step S102, it is determined whether recording is a normal character or a bit image.

If it is a bit image, it is determined in step S103 whether or not thinning is to be performed at the time of printing the bit image, that is, whether or not the DIP switch 32 is authorized for thinning recording, and the DIP switch (thinning switch) 32 is turned on. If not, in the next step S104, it is determined whether or not the character to be recorded is BGC (block graphic character) recording or reverse recording (white recording).

Step B10 for BGC recording or reverse recording
Proceed to step 5 to develop the image and perform a predetermined thinning control.

In the recording control shown in FIG. 2, thinning recording is not performed in normal character recording with emphasis on recording quality, and it is possible to select whether or not to perform thinning with the DIP switch 32 for bit image recording. An example has been described in which thinning recording is always performed at the time of (including solid printing) and reverse (black and white reversal) recording.

In step S105, after performing BGC and reverse recording data image development and performing a predetermined thinning control,
This is stored in the print buffer in the RAM 27 in step S107.

If the image is not a bit image in step S102, the process immediately proceeds to step S104 to determine whether any of BGC and reverse is present.

If the thinning is performed at the time of bit image recording in step S103 (the DIP switch 32 is in the ON state), the process directly proceeds to step S105 to develop the bit image recording data into an image and perform predetermined thinning control. After that, this is stored in the print buffer in the RAM 27 in step S107.

If the recording data is neither BGC nor reverse in the above step S104 (in this embodiment, normal characters),
After developing the image in step S106, the flow advances to step S107 to store the developed data in the print buffer in the RAM 27.

After the character image data is stored in the print buffer in step S107, the carriage motor
In step S109, it is determined whether the carriage 9 (or the inkjet recording head 6) is at the recording start position.

When it is detected that the carriage 9 has reached the recording start position, a dot image is called in step S110, and recording is performed in step S111.

In step S112, it is detected whether or not the carriage 9 has reached the recording end position of one line, and recording is performed until the carriage 9 reaches the recording end position. When the carriage 9 reaches the recording end position, the process proceeds to step S8 in FIG. Perform feeding.

FIG. 3 is a flowchart showing the operation in step S105 during the recording operation shown in FIG.
FIG. 4 is a flowchart illustrating a specific operation of image expansion and thinning control of BGC or reverse print data, and FIG. 4 is a developed view showing the thinning control of FIG. 3 in a dot image.

In FIG. 3, if the recording data is BGC (block graphic character) or reverse (white) recording, the process proceeds to step S201 to call the font data in the CG 26, and in step S202, the font data is stored in the temporary storage CG area. In step S203, it is determined whether or not all the recording information for one character has been read out. If not, the process proceeds to step S201 to repeat the above operation. After reading all the characters and storing them in the temporary storage area of the RAM 27, the process proceeds to step S204.

In step S204, a row counter m and a column counter n (these counters may be configured by hardware or provided in a work area of the RAM 27) are set to "1". That is, the point a of the dot matrix in FIG. 4 is set as the starting point.

In step S205, the currently specified dot Dot
If (m, n) is white, there is no need to thin out, so step S
Move to 211.

If Dot (m, n) is black, the process proceeds to step S206, where Do
The data at the point t (m−1, n) is read, and if white, the process proceeds to step S211. On the other hand, if it is black, the process proceeds to step S207 to read the data at the point Dot (m + 1, n). If it is white, the process proceeds to step S211. If it is black, the process proceeds to step S208 and Dot (m, n-1). Read the data at point. Step S2
If it is determined that the color is white in step 08, the process proceeds to step S211. If it is black, the process proceeds to step S209 to read out the data of the dot (m, n + 1). If it is white, the process proceeds to step S211. The black data of Dot (m, n) is converted to white (0).

In step S211, the row direction counter m is incremented by +1 (one row).
Then, the sum is stored in a counter m. Further, in step S212, it is determined whether or not the row counter has exceeded the matrix (in the present embodiment, an example of a 48 × 48 matrix is shown. Further, in S206 to S210, the dot positions outside the matrix are indicated by: An example in which the dot is virtually determined to be white will be described.) If the dot exceeds the matrix, that is, if m = 49 or more, the process returns to step S213, otherwise returns to step S205 and repeats the above operation. In step S213, the column counter is incremented by +1 (one column), and the row counter m is reset to 1. In step S214, if the column counter is n = 49 or more, the process proceeds to step S107, and the contents of the CG temporary storage area are stored in the print buffer.

According to the thinning control described above, as shown in FIG. 4, the outline of at least one character of the print data that has been thinned according to the information of one dot at the top, bottom, left and right of the dot of interest is all recorded, and the inside thereof is one line. Since alternate dot thinning is performed one by one, the dot density excluding the outline of the print data,
Almost half, that is, thinning recording of about 50% of the thinning rate can be performed.

FIG. 5 is a flowchart showing another operation procedure (embodiment) of the recording operation in step S7 in FIG.

In the ink jet recording method according to the present embodiment, the thinning rate is changed in accordance with each character instead of the thinning information determination routine, thereby making it possible to improve the fixability by the thinning and appropriately change the recording density. That is, the flowchart of FIG. 5 shows an example of the procedure of a printing operation using thinning control corresponding to each character that can cope with this density change.

In FIG. 5, after receiving the data in step S6,
When the recording operation starts, first, in step S301, a font address is specified from the print data code, and in the next step S302,
After calling the font data in CG26, step S303
It is determined whether or not one character has been read. If not, the procedure of step S302 is executed.

On the other hand, if one character has been completed, the process proceeds to step S304a, where the row counter m and the column counter n are set to “1”, respectively, and then proceeds to step S304b. In step S304b, the thinning information stored in the font 26 is specified according to the recording code or the like, and the determination is made in step S305. If the mode is 1/2 thinning mode, the process proceeds to step S306. If the mode is 1/2 thinning mode B, the process proceeds to step S316. If the mode is 1/4 thinning information, the process proceeds to step S326. Here, the operation in the 1/2 thinning-out A mode, that is, the operation from step S306 to S315 is the same as step S205 to S214 in FIG.
The description is omitted.

Next, the 1/2 thinning B mode will be described. In step S316, the currently specified dot Dot (m, n) is determined. If white, the process proceeds to step S322. If black, the process proceeds to step S317. In step S317, the dot of Dot (m-1, n-1) is determined. If white, the process proceeds to step S322. If black, the process proceeds to step S3.
Move to 18. In step S318, Dot (m + 1, n + 1)
Is determined, the process proceeds to step S322 if white, and to step S319 if black. In step S319, Dot (m + 1, n
+1), and if white, the process proceeds to step S322. If black, the process proceeds to step S320. In this step S320, Dot (m + 1, n +
If the dot of 1) is determined and the color is white, the process proceeds to step S322. If the color is black, the currently designated dot Dot (m, n) is converted to white (0).

In step S322, the row counter m is incremented by one row, and it is determined whether or not m = 49 in step S322. If the determination is affirmative, the process proceeds to step S324. On the other hand, if the difference is less than 49, the process proceeds to step S316, and the above operations (S316 to S322) are repeated.

In step S324, the column counter n is added by one column, and the row counter m is set to "1". In step S325, n
It is determined whether or not the number has reached 49. If the determination is affirmative, the process proceeds to step S107. If the value is less than 49, the process proceeds to step S316 to repeat the above operation.

If it is determined in step S305 that the mode is the 1/4 thinning-out mode, the process proceeds to step S326. The processing of steps S327 to S334 in this mode includes steps S307 to S310 and S317
Since the operations of S320 to S320 can be performed by performing the operations in series, the description thereof is omitted. Then, step S336
Then, the row counter m is incremented by 1, and in step S337, m = 49.
Is determined, and if the determination is affirmative, the process proceeds to step S338, the column counter n is incremented by 1, the row counter m is set to “1”, and the process proceeds to step S339.
If it is determined in step S339 that the column counter has reached 49, the process proceeds to step S107, and if less than 49, the process proceeds to step S326 to repeat the above operation.

In performing the thinning control of the recording dots in FIG. 5,
It is preferable that recording dot thinning information corresponding to each recording font data in a CG (character generator) 26 is stored in the memory together with the font data, and that when printing, dot thinning is performed based on the thinning information.

FIG. 6 illustrates font data (font data of the character “A” in the illustrated example) stored in the CG 26.

In FIG. 6, for example, a thinning-out information area 52, a density information area 53, and another information area 54 are provided adjacent to the left side of a font data area 51 of 48 × 48 dots. That is, information representing the type of dot thinning (thinning rate) is assigned to the address together with the font information.

Of course, the thinning information of each character may be collectively assigned to another address.

Note that the thinning information is represented by, for example, “0010” in a 1/2 thinning A mode, “0100” in a 1/2% thinning B mode, and “0011” in a 4/1 thinning mode in a 4-bit binary code. Can be.

FIG. 7A is a development view of a dot image when performing the thinning control of 1/4 thinning (thinning rate of about 25%).

This quarter thinning is performed in steps S320 to S3 in FIG.
An example obtained by the control operation at 39 is illustrated, and the control is performed such that the dots around the target dot are thinned out when all the dots around the target dot are black from the dot matrix.

FIG. 7 (B) shows the 1/2 thinning B mode (thinning rate of about 50
FIG. 7 is a development view of a dot image when performing thinning control of (%). In this 1/2 thinning B mode, the one obtained by the control in steps S316 to S325 in FIG. 5 is shown.
1 on the diagonal line from the dot matrix to the dot of interest
When all the four dots at the dot shifted positions are black, control is performed so as to thin out the dots of interest.

FIG. 8 is a flowchart showing still another embodiment of the recording operation in step S7 in FIG.

In FIG. 8, when the recording operation starts upon receiving the recording data in step S6, first, in step S501, a font address is specified based on the recording data code and the like.
After the font data in the CG 26 is called in the next step S502, the signal K of the DIP switch 32 (FIG. 10) is called in a step S503.
It is determined whether 2 is “1” (low density recording) or “0” (not low density recording).

If the low-density printing is set, the process proceeds to step S504, where the signal K4 of the DIP switch 32 (FIG. 10) is set to “1” (1/2).
It is determined whether the thinning A mode is "0" (1/2 thinning B mode), and if "1", the process proceeds to step S508 to perform the thinning in accordance with the same processing as steps S306 to S315 in FIG. Perform deployment. On the other hand, if the signal K4 is "0", the process proceeds to step S509, and the image is developed by thinning out according to the same processing as in steps S316 to S325 in FIG.

If it is determined in step S504 that the recording is not the low density recording, the process proceeds to step S505, where the dip switch 32 (the tenth
It is determined whether the signal K3 in FIG. 7 is "1" (medium density recording) and "0" (high density recording).

For medium density printing, go to step S506 and skip the thinning rate.
Perform image thinning by performing thinning control of 25% (1/4 thinning mode). In the case of high-density recording, the flow advances to step S507 to develop the image without thinning.

After the development into the dot image, the process proceeds to step S107 in FIG. 2 to store the dot image in the print buffer, and the recording is performed while performing the operations of steps S108 to S112 in FIG.

According to each embodiment described above, the following effects can be achieved.

(I) The fixing property after recording is improved by the recording dot thinning control. For example, an image appears on the second sheet, or the formed image is rubbed by feeding the second sheet after recording.
It has become possible to prevent a problem that a finger touches and becomes dirty.

(II) For patterns with high dot density and poor fixability, such as solid printing, reverse (white) recording, or block graphic character (BGC) recording, dot thinning is performed to improve the fixability and improve the fixability of normal characters. By performing printing without thinning out dots on a pattern having a small dot density and having no problem in fixing property, it is possible to achieve both improvement in fixing property and retention of recording quality.

In this case, for a recording pattern such as a bit image having a large dot density and a large number of recordings, whether or not to perform the thinning with the DIP switch 32 is configured so that the operator can manually operate the image. It is now possible to select whether to emphasize recording quality.

(III) Since the thinning rate can be changed for various characters, it was possible to improve the fixing property while securing the recording quality.

(IV) In the conventional thinning method, the outline part is not accurate because the outline is thinned. However, in the present embodiment, since the inside is thinned while leaving all the outlines, accurate characters and images are obtained. .

It is also possible to employ a configuration in which the recording density can be changed in more steps according to the operator's preference by positively utilizing dot thinning.

Further, the presence or absence of thinning and the mode setting thereof are not limited to the above-described DIP switches, and may take various forms. For example, a key switch provided on the printer side or the host side may be used, or the host side may automatically add a command or the like to data according to an image to be recorded and transmit the data.

Further, in the above example, the case where the present invention is applied to a serial printer has been described. However, it goes without saying that the present invention can be very effectively and easily applied to a line printer in which discharge ports are aligned in the width direction of paper.

[Effects of the Invention] As is clear from the above description, it is determined whether or not the pixel of interest and the pixels above, below, left, and right in the thinning process are black pixels. If the target pixel is a pixel, a process is performed in which the pixel of interest is a white pixel, so that at least one side is a white pixel, and black pixels forming the contour of a character or the like are thinned out. In addition, it is possible to perform thinning at a predetermined ratio only inside or outside the contour.

As a result, it is possible to improve the fixing property of the recording and perform high-quality recording of characters and the like.

[Brief description of the drawings]

1 is a flowchart showing an operation procedure of an ink jet recording method according to one embodiment of the present invention, FIG. 2 is a flowchart of a first embodiment of the recording operation in FIG. 1, and FIG. 3 is a flowchart in FIG. FIG. 4 is a flowchart illustrating a specific procedure of the thinning control, FIG. 4 is a schematic explanatory view of a dot image in which the half thinning A mode is performed, and FIG. 5 is a second embodiment of the recording operation in FIG. Flowchart, FIG. 6 is a schematic explanatory diagram illustrating a memory of character font data, FIG. 7 (A) is a schematic explanatory diagram illustrating a quarter thinning state, and FIG. FIG. 8 is a schematic explanatory view illustrating the state of 1 thinning B mode, FIG. 8 is a flowchart of a third embodiment of the recording operation in FIG. 1, and FIG. 9 is an ink jet recording apparatus suitable for carrying out the present invention. FIG. 10 is a sectional view of an embodiment of the present invention. It is a block diagram of a preferred control system. 4 paper, 6 ink jet head, 11 fixing heater, 21 control unit, 26 CG, 27 RAM, 32 DIP switch.

Claims (6)

(57) [Claims] A determination unit configured to determine whether a pixel of interest of print data and pixels above, below, left, and right of the pixel of interest are black pixels; If the upper, lower, left, and right pixels of the target pixel are determined to be black pixels, the target pixel is set to a white pixel, and the recording data is thinned. Recording means for performing recording by ejecting a liquid to a recording medium based on the recording data obtained. 2. The method according to claim 1, wherein the determination unit determines whether the pixel of interest and pixels above, below, left, right, upper left, lower left, upper right, and lower right of the pixel of interest are black pixels. The thinning means is configured to determine the target pixel by the determination means;
And, when it is determined that the upper, lower, left, right, upper left, lower left, upper right, and lower right pixels of the target pixel are black pixels, the recording data is thinned out by setting the target pixel to a white pixel. The liquid jet recording apparatus according to claim 1, wherein: A determining step of determining whether a pixel of interest of the print data and pixels above, below, left, and right of the pixel of interest are black pixels; and If the upper, lower, left, and right pixels of the target pixel are determined to be black pixels, a thinning step of thinning print data by setting the target pixel to a white pixel, and thinning is performed by the thinning step. A recording step of performing recording by ejecting a liquid to a recording medium based on the recording data. 4. The method according to claim 1, wherein the determining step includes determining whether the target pixel and pixels above, below, left, right, upper left, lower left, upper right, and lower right of the target pixel are black pixels. The thinning step includes the above-mentioned target pixel, and the above, below, left, right, upper left,
4. The liquid jet recording method according to claim 3, wherein when the lower left pixel, the upper right pixel, and the lower right pixel are determined to be black pixels, recording data is thinned out by setting a pixel of interest to a white pixel. 5. A discriminating means for discriminating whether or not a pixel of interest of recording data and a pixel at the upper left, lower left, upper right, lower right of the pixel of interest is a black pixel; When the upper left, lower left, upper right, and lower right pixels of the target pixel are determined to be black pixels, the target pixel is a white pixel, and a thinning unit that thins out recording data; Recording means for performing recording by ejecting a liquid to a recording medium based on the drawn recording data. 6. A discriminating step of discriminating whether or not a pixel of interest of recording data and a pixel at the upper left, lower left, upper right, or lower right of the pixel of interest is a black pixel. And when the upper left, lower left, upper right, and lower right pixels of the target pixel are determined to be black pixels, a thinning step of thinning recording data by setting the target pixel to a white pixel; and a thinning step by the thinning step. A recording step of performing recording by ejecting a liquid to a recording medium based on the recording data obtained.