JP2019171647A - Printer and printing method - Google Patents

Abstract

To inhibit bleeding of ink of an edge portion from being generated and a gap from being visually recognized.SOLUTION: A printer comprises: an edge extraction part extracting edge pixels constituting a contour of an image from image data and determining whether adjacent pixels are bright side pixels or dark side pixels for the edge pixels; and a dot data generation part generating dot data indicating a recording state of dots according to the image data for forming a plurality of dots onto a printing medium. The dot data generation part, when the edge pixels are the dark side pixels, executes first processing for discharging an ink amount less than an ink amount discharged when the pixels are non-edge pixels, and when the edge pixels are the bright side pixels, executes second processing for causing the ink amount discharged to be equal to the ink amount discharged or more when the pixels are non-edge pixels.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a printing apparatus and a printing method.

  Technology that suppresses the occurrence of blurring at the edge by reducing the number of dots formed at the edge of the image in an apparatus that prints an image by ejecting ink droplets onto the print medium to form a dot It has been known.

JP 2011-167896 A

  However, in the prior art, there is a case where a gap between dots is visually recognized by reducing the number of dots. Therefore, there has been a demand for a technique capable of suppressing the occurrence of bleeding at the edge and the visual recognition of the gap.

  According to an embodiment of the present disclosure, there is provided a printing apparatus that prints an image by ejecting ink onto a print medium from a print head having nozzles that respectively eject a plurality of colors of ink to form a plurality of dots. . This printing apparatus extracts edge pixels constituting the contour of the image from image data, and determines whether the edge pixels are pixels on the bright side or dark side with respect to adjacent pixels. An edge extraction unit; and a dot data generation unit that generates dot data indicating a recording state of dots according to the image data for forming a plurality of dots on the print medium; Performing the first process of reducing the ink amount to be ejected when the edge pixel is the dark side pixel from the ink amount to be ejected when the pixel is a non-edge pixel; When the pixel is the pixel on the bright side, the second process is executed such that the amount of ink ejected is equal to or greater than the amount of ink ejected when the pixel is a non-edge pixel.

1 is a diagram illustrating a schematic configuration of a printing system as an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating an example of nozzle arrangement in a print head. 10 is a flowchart of print processing. The conceptual diagram of an edge extraction process. The matrix which shows the calculation object pixel at the time of performing an edge extraction process for every channel. The flowchart which shows a halftone process. The figure which shows a dot image when a 1st process and a 2nd process are not performed. The figure which shows the dot image at the time of reducing the ink amount uniformly about an edge pixel. The figure which shows the dot image at the time of performing a 1st process and a 2nd process. The figure which shows schematic structure of the printing system of 2nd Embodiment. 10 is a flowchart of print processing according to the second embodiment. 9 is a flowchart illustrating color conversion processing according to the second embodiment.

First Embodiment FIG. 1 is a diagram showing a schematic configuration of a printing system 10 as an embodiment of the present invention. The printing system 10 of this embodiment includes an image processing apparatus 100 and a printer 200 that actually prints an image under the control of the image processing apparatus 100. The printing system 10 functions as a printing device in a broad sense as a whole.

  The printer 200 includes a printer control unit 210, a transport unit 220, a carriage moving unit 240, and a carriage 230 that includes the print head 23.

  The printer control unit 210 is configured as a computer including a CPU, a memory, and an input / output interface, and based on print data received from the image processing apparatus 100, the transport unit 220, the carriage moving unit 240, and the print head. 23 is controlled.

  The transport unit 220 includes a supply roller 221 around which the print medium P is wound in a roll shape, a storage roller 222 that stores the transported print medium P in a roll shape, and a platen 223 that supports the print medium P. The transport unit 220 transports the print medium P from the supply roller 221 to the storage roller 222 under the control of the printer control unit 210, and moves the print medium P in the sub-scanning direction y.

  The carriage moving unit 240 includes a carriage guide shaft 241 and a carriage motor (not shown). The carriage guide shaft 241 is disposed along the main scanning direction x that intersects the sub-scanning direction y, and both ends are fixed to the casing of the printer 200. The main scanning direction x is also the width direction of the print medium P. The carriage 230 is attached to the carriage guide shaft 241 so as to reciprocate along the main scanning direction x. The carriage moving unit 240 drives the carriage motor under the control of the printer control unit 210 to reciprocate the carriage 230 along the main scanning direction x.

  The print head 23 provided on the carriage 230 forms dots by ejecting ink droplets onto the print medium P under the control of the printer control unit 210.

  FIG. 2 is a schematic diagram illustrating an example of an arrangement of nozzles in the print head 23. FIG. 2 shows a surface of the print head 23 that faces the print medium P. As shown in FIG. 2, the print head 23 includes a plurality of nozzle rows 231. The plurality of nozzle rows 231 includes a black ink K nozzle row 231K, a cyan ink C nozzle row 231C, a magenta ink M nozzle row 231M, and a yellow ink nozzle row 231Y. Each nozzle row 231 includes two nozzle chips 232 arranged in the sub-scanning direction y. The nozzle chip 232 has 200 nozzles # 1 to # 200 arranged at a constant nozzle pitch along the sub-scanning direction y. Each nozzle is provided with a piezoelectric element for driving each nozzle to eject ink. Each nozzle is supplied with ink of each ink color from an ink tank (not shown). Black ink K, cyan ink C, magenta ink M, and yellow ink Y are ejected from each nozzle by driving the piezoelectric element under the control of the printer control unit 210. Note that various methods such as a thermal method in which bubbles are generated in the nozzles using a heat generating element and ink is discharged by the bubbles may be used as the ink discharging method.

  With the above configuration, the printer control unit 210 transports the print head 23 provided on the carriage 230 in the main scanning direction x by the carriage moving unit 240 while transporting the print medium P in the sub-scanning direction y by the transport unit 220. Then, an image is printed on the print medium P by ejecting ink from the nozzles of the print head 23 to form dots.

  Returning to FIG. 1, the image processing apparatus 100 is configured as a computer including a CPU 110, a memory 150, and an input / output interface (not shown). The memory 150 stores a print processing program (not shown), a lookup table 161, and a dot recording rate table 181. The look-up table 161 is a table in which a correspondence relationship between data expressed in RGB format and ink values in a color system that can be expressed by the printer 200 is defined. In this embodiment, the color system that can be expressed by the printer 200 is a CMYK color system. The dot recording rate table 181 is a table in which the correspondence relationship between the gradation data of a pixel and the recording rates of small, medium, and large dots that are recorded in the pixel is defined.

  The CPU 110 functions as an image acquisition unit 111, an edge extraction unit 112, a color conversion unit 121, and a halftone processing unit 122 by developing and executing a print processing program stored in the memory 150. The color conversion unit 121 and the halftone processing unit 122 are also referred to as “dot data generation unit 120”. Hereinafter, functions of each unit and print processing executed by the printing system 10 will be described.

  FIG. 3 is a flowchart of the printing process. The image acquisition unit 111 acquires image data from a personal computer (not shown) connected to the image processing apparatus 100 (step S10). In the present embodiment, the image data is RGB format data.

  Next, the edge extraction unit 112 performs edge extraction processing for extracting edge pixels (step S20). Edge pixels are pixels that exist on both sides of a pixel boundary that constitutes an edge (contour) in an image.

  FIG. 4 is a conceptual diagram of edge extraction processing. The edge extraction unit 112 first decomposes the image data D1 in RGB format into red R, green G, and blue B channels, and extracts edge pixels (Rf, Gf, Bf) for each channel. The edge pixel extraction algorithm will be described later. Next, the pixels at positions determined as edge pixels in each channel are merged, and the result is extracted as an edge pixel (RGBf).

  FIG. 5 is a matrix showing calculation target pixels when performing edge extraction processing for each channel. The edge extraction unit 112 performs edge extraction processing using a target pixel for determining whether or not the pixel is an edge pixel and four pixels (peripheral pixels) out of the surrounding 3 × 3 pixels. Among the 3 × 3 pixels shown in FIG. 5, the pixel 0 is the pixel of interest, and the pixels 1, 2, 3, and 4 are calculation peripheral pixels for determination. Whether or not the target pixel is an edge pixel is determined based on the difference between the input value of the target pixel 0 and the input values of the surrounding pixels 1, 2, 3, and 4. The input value is calculated using the following equation (1). In the following equation (1), among the coefficients α1 to α3, only the coefficient corresponding to the channel for determining whether or not it is an edge pixel is set to “1”, and the other coefficients are “0”. Set to. R, G, and B in Equation (1) are the tone values of each component.

  Input value = α1 × R + α2 × G + α3 × B (1)

  The edge extraction unit 112 calculates the absolute value of the difference between the input value of the target pixel 0 and the maximum value (P1_max) of the input values of the peripheral pixels 1, 2, 3, and 4, and the input value of the target pixel 0 and the peripheral pixel 1 , 2, 3 and 4 is determined whether the larger one of the absolute values of the differences from the minimum value (P1_min) of the input values is larger than the threshold value. Specifically, the edge extraction unit 112 inputs the input value calculated using the above equation (1) into the following equation (2), and when the equation (2) is satisfied, the target pixel 0 is an edge pixel. If it is determined that there is a pixel and the expression (2) is not satisfied, it is determined that the target pixel 0 is not an edge pixel. Here, (P1_0) is an input value of the target pixel, and (P1_1 to 4) are input values of the peripheral pixels. (P1_max) is the maximum value of (P1_1 to 4), and (P1_min) is the minimum value of (P1_1 to 4).

  Max (| P1_max−P1_0 |, | P1_min−P1_0 |)> threshold value (2)

  In the edge extraction process, the edge extraction unit 112 further determines whether the edge pixel is a bright pixel or a dark pixel with respect to the adjacent pixel when the target pixel 0 is an edge pixel. The edge extraction unit 112 calculates the luminance values of the pixels 0 to 4 using the following formula (3), and compares the luminance value of the pixel 0 with the average value of the luminance values of the peripheral pixels 1 to 4. To do. In Expression (3), a, b, and c are coefficients for multiplying the gradation values R, G, and B of the respective components, and are determined by the color system.

  L = aR + bG + cB Formula (3)

  When the luminance value of the pixel 0 is larger than the average value of the luminance values of the peripheral pixels 1 to 4, the edge extraction unit 112 determines that the pixel 0 is a bright pixel, and the luminance value of the pixel 0 is the peripheral pixel 1. If it is smaller than the average value of the luminance values of ˜4, the pixel 0 is determined as a dark pixel.

  Returning to FIG. 3, the dot data generation unit 120 performs a dot data generation process (step S30). The dot data is data indicating a dot recording state corresponding to image data for forming a plurality of dots on the print medium P. The dot data generation process includes a color conversion process (step S40) and a halftone process (step S60).

  In the color conversion process, the color conversion unit 121 uses the lookup table 161 to convert RGB data into ink amount data based on the CMYK color system (step S40).

  FIG. 6 is a flowchart showing halftone processing. The halftone processing unit 122 uses the dot recording rate table 181 to convert the ink amount data of each ink color into dot data including a combination of three types of small, medium, and large dots (step S61). As a conversion method from dot recording rate to dot data, an arbitrary halftone method such as an error diffusion method or a dither method can be used. The halftone processing unit 122 ends the halftone processing for pixels that are not edge pixels (step S63, NO).

  The halftone processing unit 122 executes the first process for the dark pixels (step S65, YES) among the edge pixels (step S63, YES) (step S67). The first process is a process of reducing the amount of ink to be ejected when the edge pixel is a darker pixel than the amount of ink to be ejected when the pixel is a non-edge pixel. In the present embodiment, the halftone processing unit 122 reduces the dot size of the dark side pixels in the first processing. Specifically, the halftone processing unit 122 converts large dots into medium dots and medium dots into small dots for the dot data generated in step S61. Small dots need not be converted, or small dots may be converted without dots.

  The halftone processing unit 122 executes the second process for the bright pixels (step S65, NO) among the edge pixels (step S63, YES) (step S69). The second process is a process in which, when the edge pixel is a bright pixel, the amount of ink ejected is equal to or greater than the amount of ink ejected when the pixel is a non-edge pixel. In the present embodiment, the halftone processing unit 122 sets the same amount of ink to be ejected when the pixel on the bright side is a non-edge pixel. That is, in the present embodiment, the halftone processing unit 122 does not convert the dot data generated in step S61. This case is equivalent to the case where the second process is not executed.

  As described above, the halftone processing unit 122 creates data indicating the presence / absence of dot formation for each pixel by performing halftone processing on the ink amount data.

  Next, the CPU 110 generates print data and outputs it to the printer 200 (FIG. 3, step S70). Specifically, the CPU 110 performs rasterization processing that divides data generated by the halftone processing into dot data for each main scanning pass. The CPU 110 generates print data by adding a print control command to the rasterized data, and outputs the print data to the printer 200. The printer control unit 210 prints an image on the print medium P based on the output print data. The print control command includes, for example, information regarding the type of the print medium P, transport data regarding the transport amount and speed of the print medium P in the sub-scanning direction y in one sub-scan, and the like. Information regarding the type of the print medium P may be output to the printer 200 separately from the print control command.

  FIG. 7 is a diagram illustrating a dot image when the first process and the second process are not performed. FIG. 7 shows dots Y1, Y2, K1, and K2 configured with the same ink amount as an example. The dots Y1 and Y2 are dots corresponding to pixels composed of a single yellow ink, and K1 and K2 are dots corresponding to pixels composed of a single black ink. Dots Y1 and K1 indicated by solid lines correspond to edge pixels, and dots Y2 and K2 indicated by broken lines correspond to non-edge pixels. The dot Y1 is a bright pixel among the edge pixels, and the dot K1 is a dark pixel among the edge pixels. The dot size represents the ink amount. If the edge pixel and the non-edge pixel have the same ink amount, bleeding may occur at the edge.

  FIG. 8 is a diagram showing a dot image when the ink amount is uniformly reduced for the edge pixels. For edge pixels, if the ink amount is reduced uniformly without distinguishing between the dark side and the bright side, the occurrence of bleeding at the edge is suppressed, but the print medium P is between the dots. It may be visually recognized.

  FIG. 9 is a diagram illustrating a dot image when the first process and the second process are performed. FIG. 9 shows an example in which the ink amount of the bright side pixel is the same as the ink amount of the non-edge pixel. By performing the first processing, the ink amount of the dot K1 corresponding to the darker pixel among the edge pixels is reduced as compared with FIG. Furthermore, by performing the second process, the dot Y1 corresponding to the brighter pixel among the edge pixels becomes equal to or larger than the ink amount in FIG. In this way, blurring occurs at the edge by reducing the ink amount of the dark side pixel among the edge pixels and setting the ink amount of the bright side pixel to be equal to or larger than the ink amount when it is a non-edge pixel. And the fact that the gap is visually recognized are suppressed.

  According to this aspect, it is possible to suppress the occurrence of blurring at the edge by reducing the amount of ink discharged when the pixel is a non-edge pixel with respect to the dark side pixel among the edge pixels. Among the pixels, regarding the brighter pixel, by setting the ink amount to be equal to or greater than that when the pixel is a non-edge pixel, it is possible to suppress a gap from being visually recognized at the edge.

  According to this aspect, it is possible to suppress the occurrence of blurring at the edge by making the darker pixel of the edge pixels smaller than the dot size when the pixel is a non-edge pixel.

  According to this aspect, it is possible to suppress a gap from being visually recognized at the edge by setting the pixel on the bright side among the edge pixels to a dot size or more when the pixel is a non-edge pixel.

Second Embodiment FIG. 10 is a diagram illustrating a schematic configuration of a printing system 10a according to a second embodiment. Differences from the first embodiment will be described. The dot data generation unit 120a as a functional unit of the CPU 110a causes the color conversion unit 121a to execute the first process and the second process. The halftone processing unit 122a performs halftone processing using the ink amount data generated by the color conversion unit 121a.

  A first coefficient 171 and a second coefficient 172 are stored in the memory 150a of the image processing apparatus 100a. The first coefficient 171 is a coefficient used in the first process, and the second coefficient 172 is a coefficient used in the second process. The first coefficient 171 and the second coefficient 172 can be determined by determining the relationship between ink wettability on the print medium P, edge bleeding and edge visibility through experiments and simulations.

  FIG. 11 is a flowchart of the printing process according to the second embodiment. In the present embodiment, the first process and the second process are executed in the color conversion process (step S40a) in the dot data generation process (step S30a).

  FIG. 12 is a flowchart of color conversion processing according to the second embodiment. First, the color conversion unit 121a uses the lookup table 161 to convert RGB format data into CMYK color ink amount data (step S41). The color conversion unit 121a ends the color conversion process for pixels that are not edge pixels (NO in step S43).

  The color conversion unit 121a performs the first process on the dark side pixel (step S45, YES) among the edge pixels (step S43, YES) (step S47). The color conversion unit 121 acquires the first coefficient 171 and multiplies the ink amount of each ink color by the first coefficient 171 to reduce the ink amount. The first coefficient 171 is a value that is greater than or equal to 0 and less than 1.0, and is a value greater than 0 and less than 1.0 in the present embodiment.

  Of the edge pixels (step S43, YES), the color conversion unit 121a performs the second process on the brighter side pixel (step S45, NO) (step S49). The color conversion unit 121a acquires the second coefficient 172, and multiplies the ink amount of each ink color by the second coefficient 172. In the present embodiment, the second coefficient 172 is 1.0. That is, the color conversion unit 121a does not convert the ink amount data generated in step S41 for the bright pixels. When the second coefficient 172 is 1.0, the color conversion unit 121a may skip step S49.

  Next, the halftone processing unit 122a refers to the dot recording rate table 181 and executes halftone processing on the ink amount data to create data indicating the presence or absence of dot formation for each pixel (FIG. 11). Step S60a). Since other processes in the printing process are the same as those in the first embodiment, description thereof will be omitted.

  Even in this mode, by reducing the amount of ink discharged when the pixel is a non-edge pixel with respect to the pixel on the dark side among the edge pixels, it is possible to suppress the occurrence of bleeding at the edge. Among them, with respect to the brighter side pixel, by setting the amount of ink to be equal to or greater than that when the pixel is a non-edge pixel, it is possible to suppress a gap being visually recognized at the edge.

Other embodiment 1
In the first embodiment, the halftone processing unit 122 does not convert the dot data generated in step S61 for the brighter pixel (FIG. 6, step S65, NO). In contrast, in the second process, the dot data generation unit 120 increases the amount of ink ejected when the edge pixel is a bright pixel from the amount of ink ejected when the pixel is a non-edge pixel. You may let them. For example, the halftone processing unit 122 may increase the ink amount by converting small dots into medium dots and medium dots into large dots for the brighter pixels. According to this form, it can suppress more that a clearance gap is visually recognized in an edge.

Other embodiment 2
In the second embodiment, the color conversion unit 121a does not convert the ink amount data generated in step S41 for the pixels on the bright side (FIG. 12, step S45, NO). On the other hand, in the second process, the dot data generation unit 120a increases the amount of ink ejected when the edge pixel is a bright pixel than the amount of ink ejected when the pixel is a non-edge pixel. You may let them. For example, the second coefficient 172 may be set to a value larger than 1.0, and the color conversion unit 121a may increase the ink amount of each ink color by multiplying the second coefficient by the second coefficient. According to this form, it can suppress more that a clearance gap is visually recognized in an edge.

Other embodiment 3
When the image data format is the CMYK color system, the edge extraction unit 112 may calculate the input value using the following equation (4) instead of the above equation (1). In this case, the edge extraction unit 112 sets only the coefficient corresponding to the channel for determining whether or not the pixel is an edge pixel among the coefficients β1 to β4 of Expression (4) to “1”, and otherwise. The coefficient of is set to “0”.

  Input value = β1 × C + β2 × M + β3 × Y + β4 × K (4)

Other embodiment 4
When the format of the image data is the CMYK color system, the edge extraction unit 112 converts the data into RGB format data using a conversion formula such as the following formulas (5-1) to (5-3), for example. Furthermore, the luminance may be calculated using the above-described equation (3) to determine whether the edge pixel is a bright pixel or a dark pixel.

R = 1−min (1, C × (1−K) + K) (5)
G = 1−min (1, M × (1−K) + K) (Formula 5-2)
B = 1−min (1, Y × (1−K) + K) (formula 5-3)

Other embodiment 5
When the format of the image data is an ink amount, the edge extraction unit 112 may calculate the input value using the following equation (6) instead of the above equation (1). Expression (6) is an example in which the ink of the plurality of colors used by the printer 200 includes cyan ink C, magenta ink M, yellow ink Y, black ink K, orange ink Or, and green ink Gr. Equation (6) can be modified depending on the number of colors. The edge extraction unit 112 sets only the coefficient corresponding to the channel for determining whether or not it is an edge pixel among the coefficients γ1 to γ6 to “1”, and sets the other coefficients to “0”.

  Input value = γ1 × C + γ2 × M + γ3 × Y + γ4 × K + γ5 × Or + γ6 × Gr (6)

Other embodiment 6
The ink used by the printer 200 may include white ink Wh. The white ink Wh is an ink for forming a base layer of an image printed on the print medium P using another ink. The printer control unit 210 may form a base layer on the print medium P by discharging the white ink Wh from the nozzle prior to the other inks under the control of the CPUs 110 and 110a. Image data composed of the white ink Wh is a single channel of the white ink Wh. An input value for determining whether or not the pixel of the image data relating to the white ink Wh is an edge pixel can be calculated using the following equation (7).

  Input value = ω1 × Wh (7)

Other embodiment 7
In the embodiment described above, printing is performed in the printing systems 10 and 10a configured by the image processing apparatuses 100 and 100a and the printer 200. On the other hand, the printer 200 itself may perform printing by inputting image data from a digital camera or various memory cards. That is, the CPU (not shown) of the printer control unit 210 of the printer 200 may perform printing by executing processing equivalent to the above-described color conversion processing and halftone processing.

-Other forms This indication is not restricted to the embodiment mentioned above, but can be realized with various forms in the range which does not deviate from the meaning. For example, this indication is realizable also with the following forms. The technical features in the above embodiment corresponding to the technical features in each embodiment described below are intended to solve part or all of the problems of the present disclosure, or part or all of the effects of the present disclosure. In order to achieve the above, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

  (1) According to an aspect of the present disclosure, there is provided a printing apparatus that prints an image by ejecting ink onto a print medium from a print head having nozzles that eject inks of a plurality of colors, thereby forming a plurality of dots. Provided. This printing apparatus extracts edge pixels constituting the contour of the image from image data, and determines whether the edge pixels are pixels on the bright side or dark side with respect to adjacent pixels. An edge extraction unit; and a dot data generation unit that generates dot data indicating a recording state of dots according to the image data for forming a plurality of dots on the print medium; Performing the first process of reducing the ink amount to be ejected when the edge pixel is the dark side pixel from the ink amount to be ejected when the pixel is a non-edge pixel; When the pixel is the pixel on the bright side, the second process is executed such that the amount of ink ejected is equal to or greater than the amount of ink ejected when the pixel is a non-edge pixel.

  According to this aspect, it is possible to suppress the occurrence of blurring at the edge by reducing the amount of ink discharged when the pixel is a non-edge pixel with respect to the dark side pixel among the edge pixels. Among the pixels, regarding the brighter pixel, by setting the ink amount to be equal to or greater than that when the pixel is a non-edge pixel, it is possible to suppress a gap from being visually recognized at the edge.

(2) In the above embodiment, the dot data generation unit determines, in the first process, the dot size when the edge pixel is the dark side pixel from the dot size when the pixel is a non-edge pixel. May be made smaller.

  According to this aspect, it is possible to suppress the occurrence of blurring at the edge by making the darker pixel of the edge pixels smaller than the dot size when the pixel is a non-edge pixel.

(3) In the above aspect, the dot data generation unit sets the dot size when the edge pixel is the bright pixel in the second processing to be equal to or larger than the dot size when the pixel is a non-edge pixel. Also good.

  According to this aspect, it is possible to suppress a gap from being visually recognized at the edge by setting the pixel on the bright side among the edge pixels to a dot size or more when the pixel is a non-edge pixel.

(4) In the above embodiment, in the second process, the dot data generation unit determines the amount of ink to be ejected when the edge pixel is the bright pixel, and the pixel is the non-edge pixel. It is also possible to increase the amount of ink ejected at a time.

  According to this aspect, it is possible to further suppress the gap from being visually recognized at the edge by increasing the pixel on the bright side among the edge pixels from the ink amount when the pixel is a non-edge pixel.

  The present disclosure can also be realized in various forms other than the printing apparatus. For example, in the form of an edge processing method, a printing method, an image processing method using the image processing apparatuses 100 and 100a, a computer program for realizing the method, a non-transitory storage medium on which the computer program is recorded, and the like. Can be realized.

  DESCRIPTION OF SYMBOLS 10, 10a ... Printing system, 23 ... Print head, 100, 100a ... Image processing apparatus, 110, 110a ... CPU, 111 ... Image acquisition part, 112 ... Edge extraction part, 120, 120a ... Dot data generation part, 121, 121a ... color converter, 122, 122a ... halftone processor, 150, 150a ... memory, 161 ... lookup table, 171 ... first coefficient, 172 ... second coefficient, 181 ... dot recording rate table, 200 ... printer, 210 ... Printer control unit, 220 ... Conveying unit, 221 ... Supply roller, 222 ... Storage roller, 223 ... Platen, 230 ... Carriage, 231, 231C, 231K, 231M, 231Y ... Nozzle array, 232 ... Nozzle chip, 240 ... Carriage movement , 241 ... carriage guide shaft, D1 ... image data , K1, K2, Y1, Y2 ... dot, P ... print medium, x ... main scanning direction, y ... sub scanning direction

Claims (5)

A printing apparatus that prints an image by ejecting ink onto a print medium from a print head having nozzles that respectively eject a plurality of colors of ink to form a plurality of dots,
An edge extraction unit that extracts edge pixels that form an outline of the image from image data, and determines whether the edge pixels are pixels on a bright side or a dark side with respect to adjacent pixels;
A dot data generation unit that generates dot data indicating a recording state of dots according to the image data for forming a plurality of dots on the print medium;
The dot data generation unit
When the edge pixel is the pixel on the dark side, a first process is performed to reduce the amount of ink to be ejected compared to the amount of ink to be ejected when the pixel is a non-edge pixel;
When the edge pixel is the pixel on the bright side, a second process is performed in which the amount of ink to be ejected is equal to or greater than the amount of ink to be ejected when the pixel is a non-edge pixel.
Printing device. The printing apparatus according to claim 1,
The dot data generation unit, in the first process, makes the dot size when the edge pixel is the dark pixel smaller than the dot size when the pixel is a non-edge pixel. The printing apparatus according to claim 1 or 2, wherein
The dot data generation unit is configured to set a dot size when the edge pixel is the bright pixel in the second processing to be equal to or larger than a dot size when the pixel is a non-edge pixel. A printing apparatus according to any one of claims 1 to 3, wherein
In the second process, the dot data generation unit increases the amount of ink ejected when the edge pixel is the bright pixel, compared to the amount of ink ejected when the pixel is a non-edge pixel. , Printing device. A printing method for printing an image on a print medium,
Processing for extracting edge pixels constituting the contour of the image from image data;
A process of generating dot data indicating a recording state of dots according to the image data for forming a plurality of dots on the print medium;
Generating dot data indicating a recording state of dots according to the image data for forming a plurality of dots on the print medium,
In the extraction process, it is determined whether the edge pixel is a bright side pixel or a dark side pixel with respect to an adjacent pixel,
In the process of generating the dot data,
When the edge pixel is the pixel on the dark side, a first process is performed to reduce the amount of ink to be ejected compared to the amount of ink to be ejected when the pixel is a non-edge pixel;
A printing method that executes a second process in which when the edge pixel is a pixel on the bright side, the amount of ink ejected is equal to or greater than the amount of ink ejected when the pixel is a non-edge pixel.

Images