JPH06106734A - Method and device for printing - Google Patents

Abstract

PURPOSE:To reproduce the contrast of an image according to the difference in density of ink by making the density of ink for dots to reproduce picture elements belonging to a group with a low image density, lower than the density of ink for dots to reproduce picture elements belonging to a group with a high image density. CONSTITUTION:A printing base on the image data of picture elements belonging to a group with a low image density is performed by an ink jet printer 1, and at the same time, a printing base on the image data of picture elements belonging to a group with a high image density is performed by the other ink jet printer 2. The density of ink for dots to reproduce the picture elements belonging to the group with a low image density is made to be lower than the density of ink for dots to reproduce the picture elements belonging to the group with a high image density. Also, printing by the other ink jet printer 2 is performed with a mark as the reference position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method and a printing apparatus for reproducing each pixel constituting an image with a number of dots corresponding to the density of the image.

[0002]

2. Description of the Related Art For example, when an image is reproduced by printing with an ink jet printer or an electrostatic plotter based on image information read by a scanner, the density of each pixel forming the image is obtained, and the image density is calculated for each pixel. Printing is performed by reproducing with the number of dots corresponding to. That is, when an image is reproduced with a density of 16 gradations, as shown in (1) of FIG. 9, the pixel corresponding to the lowest density portion of the image is reproduced with one dot D,
As shown in (2) to (15) of FIG. 9, the number of dots D is increased according to the density, and as shown in (16) of FIG. 9, there are 16 pixels corresponding to the highest density part of the image. Dot D
To reproduce the tone of the image.

[0003]

However, when each pixel is reproduced by the number of dots corresponding to the density of the image, the number of dots for reproducing the pixel is small in the portion where the density of the image is low. There is a problem in that the reproduced images in which are collected are sparse. Further, there is a problem that a gradual change in density called gradation cannot be reproduced with a natural feeling.

It is an object of the present invention to provide a printing method and a printing apparatus which can solve the above-mentioned problems of the prior art.

[0005]

The method of the present invention is characterized in that, in a printing method in which each pixel forming an image is reproduced by a number of dots corresponding to the image density, each pixel is changed according to the image density. It is divided into two or more groups, and the density of dot ink for reproducing pixels belonging to a group having a low image density is made lower than the density of dot ink for reproducing pixels belonging to a group having a high image density.

The device of the present invention is characterized in that the means for obtaining the density of each pixel forming an image, the means for dividing each pixel into two or more groups according to the image density, and each pixel corresponding to the image density. For reproducing pixels that belong to a group having a low image density, and the density of the dot ink used for reproducing pixels that belong to a group having a low image density It is lower than the density of the dot ink used for.

[0007]

According to the structure of the present invention, the density of the dot ink for reproducing the pixels belonging to the low image density group is made lower than the density of the dot ink for reproducing the pixels belonging to the high image density group. This makes it possible to reproduce the shading of an image not only according to the number of dots but also according to the difference in ink density. That is, conventionally, since the shade of an image is reproduced according to only the number of dots, it is necessary to reduce the number of dots for reproducing pixels in proportion to the density of the image. On the other hand, according to the configuration of the present invention, the density of an image is reproduced without reducing the number of dots for reproducing pixels belonging to a low density group to be smaller than the number of dots for reproducing pixels belonging to a high density group. it can.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

The printing apparatus shown in FIG. 1 includes two color inkjet printers 1 and 2, a color scanner 4 for inputting image data, an input device 9 such as a keyboard, and the color inkjet printers 1 and 2 and color printers. The scanner 4 and the control device 3 to which the input device 9 is connected are provided.

Each of the ink jet printers 1 and 2 is provided with an ink jet ejecting head 5 and 6, and each of the heads 5 and 6 has four colors of yellow (Y), magenta (M), cyan (C) and black (K). A known inkjet ejection mechanism having an ink ejection port is provided, and an image is reproduced by dots on the printing paper 7 based on a signal sent from the control device 3 based on the image data input by the scanner 4. The printing paper 7 is in the form of a roll, and is fed from one inkjet printer 1 to the other inkjet printer 2 by a feeding mechanism outside the drawing. The density of the ink ejected from the head 5 of the one inkjet printer 1 is lower than the density of the ink ejected from the head 6 of the other inkjet printer 2. A sensor 10 for detecting a mark M, which will be described later, is attached to the other inkjet printer 2.

The color scanner 4 divides the image on the original 8 into 640.times.484 pixels, and for each pixel, according to the respective densities of the three primary colors of red (R), green (G) and blue-violet (B). Image data of 16 gradations ( _RP , _GP ,
B _P ) _XY (R _P , G _P , B _P = 0 to 15, X = 0 to 63
9, Y = 0-483) is obtained.

The control device 3 can be constituted by a microcomputer having a central processing unit 3a, a storage device 3b and an input / output interface 3c. The control procedure of the control device 3 will be described below with reference to the flowcharts of FIGS.

First, image data (R _K , G _K , B _K ) _XY of 16 gradations corresponding to the respective densities of the three colors RGB of each pixel input from the color scanner 4 is read and stored in the storage device 3b. Store (step 1).

Next, the image data (R _K , G _K , B _K ) _XY corresponding to the respective densities of the three colors of RGB are converted into 4 of YMCK.
Image data of 16 gradations (Y _K , M _K , C _K , K _K ) _XY (Y _K , M _K , C _K , K according to the density of each color
_K = 0 to 15, X = 0 to 639, Y = 0 to 483) (step 2). A known conversion formula can be used for the conversion.

Next, 640 × forming an image on the original 8
The image density of one of the 484 pixels is obtained from the image data corresponding to that pixel (step 3). For example, Y
The highest density among the densities of _K , M _K , C _K , and K _{K is} the density of the pixel.

Next, 640 × forming an image on the original 8
In order to divide the 484 pixels into two groups according to the image density, it is determined whether the image density of the pixel obtained in step 3 is below a certain reference density (step 4). In the present embodiment, each pixel is defined as a density group of the first to fourth gradations and a fifth to fifth density group.
It is divided into a 16th gradation density group.

The image density of the pixel obtained in step 3 is the fourth
If the gradation is lower than the gradation, the image data of the pixel is stored in the storage device 3.
It is stored in the output area for one of the inkjet printers 1b (step 5). If the image density of the pixel obtained in step 3 is equal to or higher than the fifth gradation, the image data of the pixel is stored in the output area to the other inkjet printer 2 in the storage device 3b (step 6).

Next, it is judged whether or not the image data of all the pixels are stored in the output area to any of the ink jet printers 1 and 2 in the storage device 3b (step 7).
Steps 3 to 7 are repeated until the image data of all pixels are stored.

Next, when a print instruction is input from the input device 9 (step 8), the control device 3 sends the image data of the pixels belonging to the group having a low image density to one ink jet printer 1, and the one ink jet printer 1 To execute printing (step 9). At this time, as shown in FIG.
Is also printed. Next, the printing paper 7 is sent to the other inkjet printer 1, the mark M is read by the sensor 10, and this read signal is sent to the control device 3 (step 10). By this signal, the image data of the pixels belonging to the high density group is sent to the other inkjet printer 1 and the other inkjet printer 2 is caused to perform printing by using the mark M as a reference position. As a result, one inkjet printer 1 performs printing based on the image data of the pixels belonging to the low image density group, and the other inkjet printer 2 performs printing based on the image data of the pixels belonging to the high image density group. Be done. That is, the density of the dot ink that reproduces the pixels that belong to the low image density group is made lower than the density of the dot ink that reproduces the pixels that belong to the high image density group. The other inkjet printer 2
Since the mark M is used as a reference position for printing, it is possible to prevent the print image from the one inkjet printer 1 and the print image from the other inkjet printer 2 from deviating from each other.

With the above arrangement, the light and shade of the image is reproduced not only according to the number of dots but also according to the difference in ink density. That is, in the reproduction pattern of the pixels belonging to the low image density group, the pixel corresponding to the lowest density portion is reproduced by four dots D as shown in (1) of FIG. ) To (4), the number of dots D is increased to 8, 12, and 16 according to the density. On the other hand, in the reproduction pattern of the pixels belonging to the high image density group, the pixel corresponding to the lowest density portion is reproduced by the five dots D as shown in (5) of FIG.
As shown in (6) to (16) of FIG. 5, pixels are reproduced by increasing the number of dots D by one according to the density. Since color printing is performed in this embodiment, one dot D is formed by at least one color ink of Y, M, C, and K depending on the color of the image, and may be formed by four color inks. is there.

According to the above-described embodiment, the density of the image is reduced without reducing the number of dots for reproducing the pixels belonging to the low image density group to be smaller than the number of dots for reproducing the pixels belonging to the high image density group. Since the reproduced image can be reproduced, it is possible to prevent the reproduced image from becoming sparse, and it is possible to reproduce the gradual change in density called gradation naturally and smoothly.

The present invention is not limited to the above embodiment. For example, although the two inkjet printers 1 and 2 perform printing in the above embodiment, one inkjet printer 21 may perform the printing as shown in FIG. In this case, the inkjet ejection head 22 of the inkjet printer 21 is
Two sets of inkjet ejecting mechanisms having four ink ejecting ports of yellow (Y), magenta (M), cyan (C), and black (K) are provided, and the ink density ejected from one set of inkjet ejecting mechanisms is It is lower than the density of the ink ejected from the other set of inkjet ejecting mechanisms. Further, since it is not necessary to print the mark M as in the above embodiment, the mark detecting sensor is unnecessary. Others are the same as the above-mentioned embodiment, and the same portions are denoted by the same reference numerals. The printing procedure in this case will be described below with reference to the flowcharts shown in FIGS. 7 and 8.

First, image data (R _K , G _K , B _K ) _XY of 16 gradations corresponding to the densities of the three colors RGB of each pixel input from the color scanner 4 is read and stored in the storage device 3b. Store (step 1).

Next, the image data (R _K , G _K , B _K ) _XY corresponding to the respective densities of the three colors of RGB are converted into 4 of YMCK.
Image data of 16 gradations (Y _K , M _K , C _K , K _K ) _XY (Y _K , M _K , C _K , K according to the density of each color
_K = 0 to 15, X = 0 to 639, Y = 0 to 483) (step 2). A known conversion formula can be used for the conversion.

Next, 640 × forming an image on the original 8
The image density of one of the 484 pixels is obtained from the image data corresponding to that pixel (step 3). For example, Y
The highest density among the densities of _K , M _K , C _K , and K _{K is} the density of the pixel.

Next, 640 × forming an image on the original 8
In order to divide the 484 pixels into two groups according to the image density, it is determined whether the image density of the pixel obtained in step 3 is below a certain reference density (step 4). In the present embodiment, each pixel is defined as a density group of the first to fourth gradations and a fifth to fifth density group.
It is divided into a 16th gradation density group.

The image density of the pixel obtained in step 3 is the fourth
If the gradation is lower than the gradation, the image data of the pixel is stored in the storage device 3.
It is stored in the output area for one set of the inkjet ejection mechanism in b (step 5). If the image density of the pixel obtained in step 3 is equal to or higher than the fifth gradation, the image data of the pixel is stored in the output area to the other set of the inkjet ejection mechanism in the storage device 3b (step 6).

Next, it is judged whether or not the image data of all the pixels are stored in the output area to any one of the ink jet ejection mechanisms in the storage device 3b (step 7), and the image data of all the pixels are stored. Until step 3 to step 7 are repeated.

Next, when a print instruction is input from the input device 9 (step 8), the control device 3 sends the image data to the ink jet printer 21 to execute printing (step 9). As a result, one of the inkjet ejection mechanisms performs printing based on the image data of the pixels belonging to the low image density group, and the other inkjet ejection mechanism performs printing based on the image data of the pixels belonging to the high image density group. Be done. That is, the density of the dot ink for reproducing the pixels belonging to the low image density group is made lower than the density of the dot ink for reproducing the pixels belonging to the high image density group, and the same effect as that of the above-described embodiment is obtained. It is also possible to have a single printer.

Further, in the above embodiment, the gradation of the density of the reproduced image is set to 16 gradations, but it is not particularly limited. Moreover, the number of pixels forming an image is not particularly limited. Also,
Each pixel forming an image may be divided into three or more groups according to the image density, and inks having different densities may be set to three or more according to the number of groups. Further, although the inkjet printer is used as a means for reproducing the pixel by the number of dots corresponding to the image density, the invention is not limited to this.
For example, an electrostatic plotter may be used. The dot ink is not limited to a liquid, and may be solid ink such as toner or ink ribbon. Further, the present invention can be applied to the case of performing monochrome printing.

[0031]

According to the present invention, since the light and shade of an image can be reproduced not only by the number of dots but also by the difference in ink density, it is possible to increase the number of dots in an image portion where low density pixels are gathered, and to reproduce the image. It is possible to prevent the image from becoming sparse, and it is possible to reproduce a gradual change in density called gradation, which looks natural.

[Brief description of drawings]

FIG. 1 is a configuration explanatory diagram of a printing apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart of the first embodiment of the present invention.

FIG. 3 is a flowchart of the first embodiment of the present invention.

FIG. 4 is a plan view of a reproduced image according to the embodiment of the present invention.

FIG. 5 is a diagram showing a pixel configuration pattern according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of a configuration of a printing apparatus according to a second embodiment of the present invention.

FIG. 7 is a flowchart of the second embodiment of the present invention.

FIG. 8 is a flowchart of the second embodiment of the present invention.

FIG. 9 is a diagram showing a pixel configuration pattern of a conventional image.

[Explanation of symbols]

 1, 2 and 21 printer 3 control device 4 scanner

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8703-2C B41J 3/12 G

Claims (2)

[Claims] 1. A printing method in which each pixel forming an image is reproduced by a number of dots corresponding to the image density, and each pixel is divided into two or more groups according to the image density and belongs to a group having a low image density. A printing method, wherein the density of dot ink for reproducing pixels is set lower than the density of dot ink for reproducing pixels belonging to a group having a high image density. 2. A means for obtaining the density of each pixel forming an image, a means for dividing each pixel into two or more groups according to the image density, and a means for reproducing each pixel by a number of dots corresponding to the image density. The density of the dot ink used by the reproducing means for reproducing the pixels belonging to the group having a low image density is the density of the dot ink used for reproducing the pixels belonging to the group having a high image density. A printing device characterized by being made lower than.