JP2000108420A - Printer, printing method and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printer provided with more than one kind of ink of different density in the same hue and forming dots of different weight of ink in which high image quality is ensured by determining on/off of each dot using a recording rate set for each dot depending on a gray level data. SOLUTION: More than one kind of ink of different density in the same hue is provided and more than two kinds of dots including more than one kind of dot formed by varying the weight of at least one kind of ink are formed and then a multi level halftoning image is printed by distributing the dots. In this regard, on/off of each dot formed by same ink is determined for each pixel consecutively in the order of ink weight and a head 28 is driven depending on the determination results to form each kind of dot. At the time of forming a dot, recording rate of each dot is set based on the gray level data and on/off decision is made by dither method using the recording rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a printing method for printing an image in multiple tones by forming three or more types of dots, a recording medium storing a program for the method, and a printing apparatus for realizing the printing.

[0002]

2. Description of the Related Art Conventionally, as an output device of a computer, there has been proposed an ink jet printer which forms dots by using several colors of ink ejected from a plurality of nozzles provided in a head and records an image. Is widely used to print processed images in multiple colors and multiple gradations. In such a printer, usually, only two gradations of dot on / off can be taken for each pixel. Therefore,
The image is printed after image processing for expressing the gradation of the original image data by the dispersibility of dots, that is, so-called halftone processing.

In recent years, to enrich the gradation expression,
2. Description of the Related Art There has been proposed an ink-jet printer capable of expressing not only ON / OFF for each pixel but also three or more gradations, that is, a so-called multi-value printer. For example, a printer that can express three or more types of densities for each dot by changing the dot diameter and ink density, and a multi-gradation can be expressed by superposing a plurality of dots for each pixel It is a printer. Even in such a printer, halftone processing is required because the gradation of the original image data cannot be sufficiently expressed in each pixel unit.

[0004] As a halftone processing method, a dither method and an error diffusion method are representative. The dither method is a method of determining dot on / off based on a magnitude relationship between a threshold value provided for each pixel by a dither matrix and a tone value of image data. The error diffusion method diffuses a density error generated as a result of deciding on / off of a dot for a certain pixel to peripheral pixels and corrects the gradation data of these pixels. Is a method of determining dot on / off based on the magnitude relation between the dot on and off. The former has an advantage that it can be processed at high speed, and the latter has an advantage that it has excellent image quality.

[0005] In a multi-valued printer capable of expressing three or more levels of gradation, a plurality of types of dots can be formed for the same hue. Normally, in the halftone processing, ON / OFF of these dots is determined individually. However, in order to realize high-quality printing in which multiple gradations are smoothly expressed, it is desirable to avoid that dots corresponding to the same hue are formed in the same pixel. For example, Japanese Patent Laid-Open No.
7167.

In the halftone processing described in the above publication, the dither method is applied as follows to determine on / off of a high density dark dot and a low density light dot. First, the recording rate of a dark dot and the recording rate of a light dot are obtained from a prepared table in accordance with the gradation data. Next, the on / off state of the dots is determined based on the magnitude relation between the threshold and the recording rate given by the same dither matrix in the order of dark dots and light dots. On this occasion,
As for the light dots, ON / OFF is determined by comparing the sum of the recording rate of the dark dots and the recording rate of the light dots with a threshold value. Also, for the pixels for which the dark dot is turned on,
Light dots are turned off. With such a method, both can be recorded on different pixels while maintaining the recording rate of both.

[0007]

However, a multi-valued printer having two or more types of inks having the same hue and different densities and capable of forming dots having different ink weights is disclosed.
The order of judging the on / off of each dot and the halftone process to be used were not sufficiently considered. As such a printer, for example, there is a printer that includes two types of inks of different shades and can form two or more types of dots having different ink weights with each ink.

In order to realize high quality printing, as described above, it is desirable to form dots having the same hue in a dispersed manner. However, the weights for ensuring the dispersibility are different between dots having the same hue. For example, dots formed by inks having different densities
It is usually formed by individual heads. Therefore, even if these dots are formed in the same pixel, the influence on the printing speed is small. On the other hand, if dots formed by changing the ink weight with the same ink are formed in the same pixel, it is necessary to drive the head twice or more for the pixel, so that the printing speed decreases. In consideration of this point, it can be said that the demand for ensuring the dispersibility of dots is particularly high between dots formed by the same ink.

On the other hand, if the number of types of dots for which ON / OFF should be determined for each pixel increases, the time required for halftone processing increases. If halftone processing is performed by the dither method, high-speed processing can be performed to some extent, but sufficient image quality cannot be achieved. In the first place, the purpose of a multi-value printer is to enrich the gradation expression and realize high-quality printing, so that the deterioration of the image quality cannot be overlooked. If the halftone process is performed by the error diffusion method, the image quality is sufficient, but the time required for the process becomes extremely long.

[0010] In consideration of these points, there has been no example of examining in what order and by what method halftone processing should be performed on dots that can be formed by a multilevel printer. The above-described problem has arisen not only in printers but also in various printing apparatuses capable of expressing three or more levels of density for each pixel using inks having different densities and dots having different ink weights. The present invention has been made to solve such a problem, and it is possible to provide two or more types of inks having the same hue and different densities, and to form dots having different ink weights with at least one of them. It is an object of the present invention to provide a technique for determining on / off of each dot in an appropriate order in a multi-value printer and enabling high quality printing.

[0011]

Means for Solving the Problems and Their Functions / Effects To solve at least a part of the above-mentioned problems, the present invention provides:
The following configuration was adopted. The first printing method of the present invention includes two or more types of inks having the same hue and different densities, and includes two or more types of dots formed by changing the ink weight with at least one of the inks. A printing method for printing a multi-tone image based on the distribution of dots using a head capable of forming three or more types of dots on a print medium, wherein (a) inputting tone data of an image to be printed (B) determining on / off of each dot sequentially for each pixel in the order in which the dots formed by the same ink are continuous in the order of the ink weight; and (c) determining the result of the determination. Driving the head accordingly to form the respective types of dots.

Here, the step (b) includes: (b1) a step of setting a recording rate of each dot based on the gradation data; and (b2) a step of setting the recording rate for the first dot to be determined. Based on the magnitude relationship between the rate and the threshold value stored in the previously prepared dither matrix, the on / off state of the dot is determined.
The step of judging off, and (b3) for the second and subsequent dots to be judged, priority is given to the pixels excluding the pixels for which any of the previously judged dots have been turned on, and Determining the on / off state of each dot by determining the on / off state of the dot based on the magnitude relationship between the recording rate reflecting the recording rate of the dot previously determined according to the recording rate and the threshold. It is.

According to the printing method, steps (b1) to (b1)
By the step (b) consisting of (b3), each dot is prevented from being formed overlapping the same pixel,
On / off determination can be made according to the gradation data. A case where the dot is turned on when the recording rate is larger than the threshold value stored in the dither matrix will be described as an example. For a dot to be initially determined to be on / off, the dot is turned on in a portion where the threshold of the dither matrix is relatively small in accordance with the recording rate. In this manner, the on / off state of the next dot to be determined is determined while avoiding the pixel where the dot is turned on. The pixel for which the first dot to be determined is off is a pixel having a relatively large dither matrix threshold value. Therefore, ON / OFF is performed using only the recording rate of the second dot to be determined.
If the determination of OFF is made, it is difficult for the second dot to be determined to be ON. In the above printing step (b3), the threshold value is determined by determining the value obtained by adding the recording rate of the first determination target dot to the recording rate of the second determination target dot, and the threshold value. A desired recording rate is ensured by avoiding a state in which the recording is difficult to be formed. In this way, it is possible to determine the on / off state of the second dot while avoiding overlapping with the first dot to be determined. The same applies to the third and subsequent dots to be determined.

In the above step (b3), the method of reflecting the recording rate of the previously determined dot in accordance with the recording rate of the dot to be determined is such that when either the recording rate or the threshold value is larger, the ON state is set. It depends on whether to judge. When it is determined to be ON when “recording ratio> threshold”, the recording ratio of the dot determined before is added to the recording ratio of the dot to be determined. Conversely, if it is determined that the recording rate is ON when “recording rate <threshold”, the recording rate of the previously determined dot is subtracted from the recording rate of the dot to be determined.

The above steps (b1) to (b3) are not related to the type of ink. For example, consider a case where four types of dots having large and small ink weights are formed by two types of dark and light inks, respectively. Judgment of dot on / off
The order is “large dot with dark ink” → “small dot with dark ink” → “large dot with light ink” → “small dot with light ink”. In the above printing method, for example, when determining “large dot by light ink”, the recording rates of “large dot by dark ink” and “small dot by dark ink”, which are the dots previously determined, are reflected. Thus, regardless of whether the ink types are the same,
By judging on / off of dots after reflecting the previous recording rate, it is possible to easily avoid that dots formed by inks having different densities are formed in the same pixel.

In the above printing method, in the step (b),
On / off of each dot is determined in a predetermined order. At this time, the dots formed by the same ink are determined in a continuous order in the order of the ink weight. The four types of dots exemplified above are determined in the illustrated order. "Large dot with light ink" → "Small dot with light ink" → "Large dot with dark ink" →
The determination may be made in the order of “small dots by dark ink”. It has nothing to do with the density expressed per unit area by each dot. By judging the dots formed by the same ink in a continuous order, there is an advantage that even if the dots have to be formed overlapping each other, the control becomes easy.

Various settings can be made for the dot recording rate, and the total dot recording rate may exceed 100%. When the recording rate exceeds 100%, dots of the same hue are formed overlapping at any pixel. Even if the dots have the same hue, the dots formed with inks having different densities usually have individual forming portions for forming the dots. Therefore, even if these dots are formed to overlap each other, the influence on the printing speed is small. On the other hand, when dots formed by the same ink are formed so as to overlap with each other, it is necessary to drive the forming unit twice or more for one pixel, which causes a reduction in printing speed. According to the printing method of the present invention, it is possible to turn on / off dots formed by the same ink.
Since OFF is determined continuously, it is easy to control the relationship between these dots. Therefore, even when dots have to be formed by overlapping some of the pixels, it is possible to suppress the possibility that dots formed by the same ink are formed by overlapping, and the printing speed is reduced. Can be avoided.

The order of judging dots in the above step (b) can be set in various orders under the condition that dots formed by the same ink are continuous. Turn on / off dots formed with relatively low density ink
After the off-state is determined first, the dot formed by the ink with high density may be determined. Further, dots formed by the same ink may be determined continuously in descending order of ink weight, or may be determined continuously in ascending order of ink weight. further,
The order may be set regardless of the magnitude of the ink weight.

As described above, the determination order can be variously set, but in the step (b), the on / off of the respective types of dots is performed in order from the higher density of the ink forming the dots to the lower density. It is desirable that this is the step of determining.

In general, dots formed by high-density ink have a property of being easily recognized. Therefore, it is desirable in terms of image quality to ensure sufficient dispersibility of these dots. According to the above sequence, the on / off determination can be made in a state where the degree of freedom is higher for the dots formed by the ink having higher density, so that the dispersibility can be more appropriately secured and the image quality can be improved. .

The printing method of the present invention can be applied, for example, in the following manner. The dots that can be formed by the head are a total of four or more types of dots formed with two or more stages of ink weight using high-density deep ink and low-density light ink, respectively.
In this embodiment, the on / off of dots formed by dark ink is determined in descending order of ink weight, and then the on / off of dots formed by light ink is determined in descending order of ink weight. Of course, it is not limited to such an embodiment.

According to a second printing method of the present invention, two or more kinds of inks having the same hue and different densities are provided, and two or more kinds of inks formed by changing the ink weight with at least one of the inks. A printing method for printing a multi-tone image by a distribution of the dots by using a head capable of forming three or more types of dots including a dot on a print medium, wherein (a) a tone of an image to be printed A step of inputting data; and (b) determining on / off of dots formed by the same ink for each pixel in order of ink weight and excluding the dot having the lowest density evaluation value. And (c) for a dot having the lowest density evaluation value, an error expansion based on correction data in which a density error caused by turning on / off other dots is also reflected in the gradation data. Law comprises a step of determining on-off, and forming (d) is the determination result dot type of each of the drives said head in accordance with the.

Here, the step (b) includes: (b1) a step of setting the recording rate of each of the dots based on the gradation data; and (b2) a step of setting the recording rate for the first dot to be determined. Based on the magnitude relationship between the rate and the threshold value stored in the dither matrix prepared in advance, the ON / OFF of the dot is determined.
The step of judging off, and (b3) if there is a dot to be judged after the second, prioritize the pixels excluding the pixels for which any of the dots previously judged were turned on. Determining the on / off of each dot based on the magnitude relation between the recording rate reflecting the dot recording rate previously determined according to the recording rate of the dot and the threshold value. Is the step of determining

In this printing method, the on / off determination method differs between the dot having the lowest density evaluation value and the other dots. For the dot having the lowest density evaluation value, ON / OFF of the dot is determined by the error diffusion method, and for the other dots, ON / OFF is determined by the dither method. In the determination by the dither method, that is, in the step (b), as in the case of the first printing method, it is possible to determine the on / off state while ensuring the dispersibility of dots of the same hue.

When the on / off state of a dot is determined by the dither method, a local error generated between the density expressed according to the result and the density to be expressed according to the gradation data is relatively large. May be. If the ON / OFF of the dot is determined by the error diffusion method, such a local error can be suppressed. In the above printing method, for the dot with the lowest density evaluation value, ON / OFF of other dots
The on / off state is determined by an error diffusion method in consideration of the density error generated in accordance with the off state. Therefore, local density errors can be suppressed, and high-quality printing can be performed. The error diffusion method has a disadvantage of requiring processing time.
On the other hand, according to the printing method, the dots to which the error diffusion method is applied are minimized by judging on / off of dots other than the dot having the lowest density evaluation value by the dither method. Accordingly, high-quality printing can be realized while suppressing an increase in processing time.

In the above printing method, the target to which the error diffusion method is applied is a dot having the lowest density evaluation value. The dot having the lowest density evaluation value is hard to be visually recognized.
Therefore, if the error diffusion method is applied to such dots, local density errors can be eliminated without making the dots stand out. Note that the dots to which the error diffusion method is applied may be extended to a plurality of dots having a lower density evaluation value as long as the requirements for the processing time are satisfied.

In the above-described second printing method, the dots for which the on / off state is determined by the dither method are the same as in the first printing method regardless of whether or not the inks forming the dots are the same. , The recording rate determined previously. On the other hand, the reflection of the recording rate determined previously may be performed for each ink. At this time, it is desirable to use different dither matrices in order to ensure sufficient dispersibility between dots formed with different inks. Although it is possible to prepare completely different dither matrices according to the type of ink, it is more preferable to realize the dither matrices in the following manner.

The step (b) further comprises the step of: (b0) generating a dither matrix for giving a threshold value in a different arrangement for each type of ink from a pre-stored dither matrix, wherein a dot formed by the same ink is used. For each, using a dither matrix corresponding to the ink,
This is a mode in which the steps (b2) and (b3) are performed to determine ON / OFF.

This makes it possible to newly generate a dither matrix corresponding to each ink from the previously stored dither matrix, thereby saving the capacity of a memory for storing the dither matrix. The generation of the dither matrix corresponding to each ink includes a mode in which the correspondence between the pixels and the dither matrix is changed for each type of ink. After storing the generated dither matrix in the memory,
There is no need to provide for the determination of OFF.

According to the above-described embodiment, the following effects can be obtained by performing the reflection of the recording rate determined before for each ink. For example, if the recording rate is reflected without being divided for each ink, when the dot recording rate is set to exceed 100% as a whole, the determination of dot on / off may be complicated. There is. On the other hand, if the recording rate is reflected separately for each ink, it is possible to avoid the overlap between dots formed by the same ink and to allow the overlap between the dots formed by different inks. Off determination can be realized relatively easily. When the recording rate is reflected for each ink, the ON / OFF determination can be performed in parallel for each ink, so that the processing can be speeded up. Furthermore, since the dot recording rate can be easily controlled for each ink, the control of the ejection amount for each ink can be realized relatively easily.

The second printing method can be applied to a printing apparatus capable of forming dots with various concentrations of ink and various ink weights. Specifically, the second printing method can be applied, for example, in the following manner. The dots that can be formed by the head are a total of four or more types of dots formed by high-density dark ink and low-density light ink at two or more levels of ink weight, respectively, and the dot with the lowest density evaluation value is The dot having the lowest ink weight formed by the light ink. In the step (b), first, the on / off of the dots formed by the dark ink, excluding the dot, is determined in the descending order of the ink weight, Next, an aspect as a step of judging on / off of dots formed by light ink in descending order of ink weight. Of course, it is not limited to such an embodiment.

The above-described printing method is generally realized by driving a printing apparatus based on data processed by a computer based on a predetermined program. Therefore, the printing method of the present invention is also realized as a recording medium on which such a program is recorded. The first recording medium of the present invention includes two or more types of inks having the same hue and different densities, and includes two or more types of dots formed by changing the ink weight with at least one of the inks. A computer-readable recording medium for recording a program for printing an image by a printing apparatus capable of forming three or more types of dots on the printing medium, the function of inputting gradation data of an image to be printed; The dots formed by the same ink are sequentially determined in the order of ink weight, and a determination function for sequentially determining ON / OFF for each dot for each pixel, and driving the head according to the determination result, A function of forming each type of dot can be realized, and the determination function sets the recording rate of each dot based on the gradation data. Features and a first Dot to be determined, function to determine the on-off of the dot on the basis of the magnitude relation between the recording rate and a prepared dither matrix stored threshold,
Regarding the second and subsequent dots to be determined, priority is given to pixels excluding the pixels for which any of the previously determined dots have been turned on, and the recording rate of the previously determined dot is determined. A recording medium on which is recorded a program that is a function of determining the on / off of each dot by a function of determining the on / off of the dot based on a magnitude relationship between the recording rate reflecting the recording rate and the threshold. .

The second recording medium of the present invention comprises two or more types of inks having the same hue and different densities, and two or more types of inks formed by changing the ink weight with at least one of the inks. A computer readable recording medium for recording a program for printing an image by a printing apparatus capable of forming three or more types of dots including dots on a printing medium, and inputting gradation data of the image to be printed. The function and the dots formed by the same ink for each pixel are consecutive in the order of ink weight,
A dither determination function for sequentially determining ON / OFF for dots excluding the dot having the lowest density evaluation value, and a density error generated in accordance with ON / OFF of other dots for the dot having the lowest density evaluation value are also obtained by the above-described processing. A function to determine ON / OFF by an error diffusion method based on correction data reflected in tone data and a function to form the respective types of dots by driving the head in accordance with the determination result can be realized. Wherein the dither determination function is a function of setting the recording rate of each dot based on the gradation data,
A function of determining on / off of a dot to be determined first based on a magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix; When there is a dot that is determined, the priority is given to the pixels excluding the pixel in which any of the previously determined dots have been turned on, and the recording rate of the previously determined dot is determined. A recording medium on which is recorded a program which is a function of judging on / off of each dot by a function of judging on / off of the dot based on a magnitude relationship between the reflected recording rate and the threshold value.

The above-described printing method of the present invention can be realized by executing the program recorded on each of the recording media by a computer. In addition, as a storage medium, a flexible disk or a CD-RO
M, a magneto-optical disk, an IC card, a ROM cartridge, a punched card, a printed matter on which a code such as a bar code is printed, a computer internal storage device (RAM or ROM)
A variety of computer-readable media can be used, such as a memory (e.g., memory) and an external storage device. The present invention also includes an aspect as a program supply device that supplies, via a communication path, a computer program that causes a computer to realize the multilevel function of the image processing device.

The present invention is also realized in a printing apparatus capable of realizing the above-described printing method. The first printing apparatus of the present invention includes two or more types of inks having the same hue and different densities, and includes two or more types of dots formed by changing the ink weight with at least one of the inks. What is claimed is: 1. A printing apparatus comprising: a head capable of forming three or more types of dots on a printing medium; and a printing apparatus capable of printing a multi-tone image based on the distribution of the dots. And dither determining means for sequentially determining ON / OFF of each dot for each pixel in the order in which the dots formed by the same ink are continuous in the order of ink weight, and driving the head according to the determination result Dot forming means for forming the respective types of dots, wherein the dither determining means stores a relationship between a recording rate of each dot and gradation data. And,
With reference to the storage means, setting means for setting the recording rate of each dot in accordance with the gradation data, and ON / OFF has been previously determined for the recording rate of the dot to be determined. A value reflecting the dot recording rate,
On the basis of the magnitude relation with the threshold value stored in the dither matrix prepared in advance, priority is given to the pixels other than the pixels in which any of the previously determined dots has been turned on, and the on / off of the dots is determined. The gist of the invention is that it is means for judging on / off of each dot by the dot formation judging means to be judged.

The second printing apparatus of the present invention comprises two or more types of inks having the same hue and different densities, and two or more types of inks formed by changing the ink weight with at least one of the inks. A printing apparatus, comprising: a head capable of forming three or more types of dots including dots on a print medium, capable of printing a multi-tone image based on the distribution of the dots, and inputting tone data of an image to be printed. Input means, and dither determination means for sequentially determining on / off for dots excluding the dot having the lowest density evaluation value in the order in which dots formed by the same ink are successive in the order of ink weight for each pixel, For a dot having the lowest density evaluation value, an error diffusion method based on correction data in which a density error caused by turning on / off other dots is also reflected in the gradation data. Error diffusion determining means for further determining on / off, and dot forming means for driving the head in accordance with the determination result to form the respective types of dots, wherein the dither determining means comprises: Storage means for storing the relationship between the recording rate and the gradation data, and setting means for setting the recording rate of each dot in accordance with the gradation data with reference to the storage means. Based on the magnitude relationship between a value that reflects the recording rate of a dot for which on / off has been previously determined with respect to the recording rate of the dot and a threshold value stored in a previously prepared dither matrix, the determination is made in the past. The priority is given to pixels other than the pixels for which any of the target dots have been turned on, and the dot formation determining means for determining whether the dots are on or off turns on or off each dot. And summarized in that a means for the constant.

According to these printing apparatuses, the above-described printing method of the present invention can be realized. The dot formation determining means in the first printing apparatus and the second printing apparatus reflects a recording rate of a dot for which ON / OFF has been previously determined on a recording rate of a dot to be determined. The value is used to determine dot on / off. As for the dot for which ON / OFF is determined first, there is no dot which has been previously determined as the target, so that the ON / OFF of the dot is determined using the recording rate set by the setting means as it is. For the second and subsequent dots to be determined, the on / off state of the dot is determined using a result value in which the recording rate of the dot to be determined so far is reflected in the recording rate of the dot to be determined. I do.

The input means and dither determination means and the dot forming means in the first printing apparatus may be provided in the same housing, or may be provided in different housings. Similarly, in the second printing apparatus, the input unit, the dither determination unit, the error diffusion determination unit, and the dot forming unit may be provided in the same housing, or may be provided in different housings. Is also good. The printing apparatus may be configured from a plurality of housings in various other correspondences.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples. (1) Configuration of Apparatus: FIG. 1 is a block diagram showing the configuration of a printing system to which a printing apparatus as one embodiment of the present invention is applied. As shown, the scanner 12 and the color printer 22 are connected to the computer 90. A predetermined program is loaded and executed on the computer 90 to function as a printing apparatus. The computer 90 includes the following units interconnected by a bus 80, centering on a CPU 81 that executes various arithmetic processes for controlling operations related to printing according to a program. The ROM 82 previously stores programs and data necessary for the CPU 81 to execute various arithmetic processes.
The RAM 83 is a memory for temporarily reading and writing various programs and data necessary for the CPU 81 to execute various arithmetic processes. Input interface 84
Manages the input of signals from the scanner 12 and the keyboard 14, and the output interface 85 manages the output of data to the printer 22. The CRTC 86 controls signal output to the CRT 21 capable of color display, and the disk controller (DDC) 87 controls the hard disk 16 and the CD-RO.
It controls data transfer between the M drive 15 and a flexible drive (not shown). Hard disk 1
6 stores various programs loaded into the RAM 83 and executed, various programs provided in the form of device drivers, and the like.

In addition, a serial input / output interface (SIO) 88 is connected to the bus 80. This SIO 88 is connected to the modem 18 and the modem 1
8 is connected to a public telephone line PNT. The computer 90 is connected to an external network via the SIO 88 and the modem 18. By connecting to a specific server SV, it is also possible to download a program necessary for printing an image to the hard disk 16. . In addition, it is also possible to load a necessary program from a flexible disk FD or a CD-ROM, and cause the computer 90 to execute the program. Naturally, these programs can adopt a mode in which the entire program necessary for printing is loaded collectively, or, for example, a mode in which only a characteristic portion of the present embodiment is loaded as a module.

FIG. 2 is a block diagram showing a software configuration of the printing system. In the computer 90, an application program 95 operates under a predetermined operating system. The operating system includes a video driver 91 and a printer driver 9.
6 are incorporated. An application program 95 for retouching an image reads an image from the scanner 12 and displays the image on the CRT display 21 via the video driver 91 while performing predetermined processing on the image. Data OR supplied from scanner 12
G is original color image data ORG that is read from a color original and includes three color components of red (R), green (G), and blue (B).

This application program 95
When a print command is issued, the printer driver 96 of the computer 90 receives the image data from the application program 95, and receives the image data from the application program 95. The signal can be processed by the printer 22. Signal). In the example shown in FIG. 2, inside the printer driver 96,
Resolution conversion module 97 and color correction module 98
, A color correction table LUT, a halftone module 99, and a rasterizer 100.

The resolution conversion module 97 serves to convert the resolution of the color image data handled by the application program 95, that is, the number of pixels per unit length into a resolution that can be handled by the printer driver 96. The image data whose resolution has been converted in this way is still RGB.
, The color correction module 98 refers to the color correction table LUT and uses the cyan (C), magenta (M), yellow (Y), and black used by the printer 22 for each pixel. (K) is converted into data of each color. The data thus color-corrected is, for example, 2
It has a gradation value with a width such as 56 gradations. The halftone module 99 executes a halftone process for expressing such gradation values in the printer 22 by forming dots in a dispersed manner. The image data thus processed is rearranged by the rasterizer 100 in the order of data to be transferred to the printer 22, and the final print data FN
Output as L. In the present embodiment, the printer 22 only plays a role of forming dots in accordance with the print data FNL, and does not perform the above-described image processing. However, it goes without saying that these processes may be performed by the printer 22.

The schematic configuration of the printer 22 applied to this embodiment will be described with reference to FIG. As shown in the drawing, the printer 22 includes a mechanism for transporting the paper P by a paper feed motor 23, a mechanism for reciprocating a carriage 31 in the axial direction of a platen 26 by a carriage motor 24,
A mechanism for driving a print head 28 mounted on a carriage 31 to eject ink and form dots, and a control for exchanging signals with the paper feed motor 23, carriage motor 24, print head 28 and operation panel 32. And a circuit 40.

A mechanism for reciprocating the carriage 31 in the axial direction of the platen 26 includes a sliding shaft 34 erected in parallel with the axis of the platen 26 and slidably holding the carriage 31.
A pulley 38 for extending an endless drive belt 36 between the carriage motor 24 and a position detection sensor 39 for detecting the origin position of the carriage 31 are provided.

The carriage 31 of the printer 22 includes
Black ink (K) cartridge 71 and cyan (C),
A color ink cartridge 72 containing five color inks of light cyan (LC), magenta (M), light magenta (LM), and yellow (Y) can be mounted. A total of six ink discharge heads 61 to 66 are formed on the print head 28 below the carriage 31. At the bottom of the carriage 31, an ink passage 68 for guiding ink from the ink tank to each color head is provided.

FIG. 4 is an explanatory diagram showing a schematic configuration inside the ink discharge head 28. As shown in FIG. For convenience of illustration, the portions that eject black ink (K), cyan (C), and light cyan (LC) are shown. Actually, as shown in the plan view of FIG. 5, heads 61 to 66 of each color are arranged. When the ink cartridges 71 and 72 are mounted on the carriage 31, the respective color inks are supplied to the respective color heads 61 to 66 of the print head 28 through the ink passage shown in FIG.

A plurality of nozzles Nz are provided in the heads 61 to 66, and a piezo element PE which is one of the electrostrictive elements and has excellent responsiveness is provided for each nozzle as shown in FIG. Are located in As is well known, the piezo element PE is an element that distorts the crystal structure due to the application of a voltage and converts electro-mechanical energy very quickly. In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE is extended by the voltage application time as shown by the arrow in FIG. Then, one side wall of the ink passage 68 is deformed. As a result, the volume of the ink passage 68 contracts in accordance with the expansion of the piezo element PE, and the ink corresponding to the contraction amount becomes the particle Ip.
As a result, the liquid is discharged at a high speed from the tip of the nozzle Nz. Printing is performed by the ink particles Ip penetrating into the paper P mounted on the platen 26.

FIG. 5 is an explanatory diagram showing the arrangement of the ink jet nozzles Nz in the ink discharge heads 61 to 66. The arrangement of these nozzles is composed of six sets of nozzle arrays that eject ink for each color, and 48 nozzles Nz are arranged in a staggered manner at a constant nozzle pitch k. The positions of the nozzle arrays in the sub-scanning direction coincide with each other. The 48 nozzles Nz included in each nozzle array need not be arranged in a staggered manner, but may be arranged on a straight line. However, the arrangement in a staggered manner as shown in FIG. 5 has an advantage that the nozzle pitch k can be easily set small in manufacturing.

The printer 22 of the present invention can form three types of dots having different ink weights, that is, large dots, medium dots, and small dots, using the nozzles Nz having a constant diameter shown in FIG. This principle will be described.
FIG. 6 is an explanatory diagram showing the relationship between the driving waveform of the nozzle Nz when ink is ejected and the ink Ip ejected. The drive waveform indicated by a broken line in FIG. 6 is a waveform when a normal dot is ejected. In the section d2, once the potential of the piezo element PE is set to a low potential, the piezo element PE is deformed in a direction to increase the cross-sectional area of the ink passage 68, contrary to the description with reference to FIG. Since this deformation is performed at a higher speed than the supply speed of the ink from the ink passage 68, the ink interface Me called a meniscus is depressed inside the nozzle Nz as shown in the state A of FIG. When the potential is rapidly decreased as shown in the section d1 using the drive waveform shown by the solid line in FIG. 6, the deformation speed of the ink passage 68 is further increased. It becomes a state (state a). Next, when the voltage applied to the piezo element PE is made positive (section d)
3) Ink is ejected based on the principle described above with reference to FIG. At this time, the state B and the state C are changed from the state in which the meniscus is not much depressed inward (state A).
Large ink droplets are ejected as shown in (a), and small ink droplets are ejected as shown in the state (b) and the state (c) from the state where the meniscus is largely dented inward (state a).

Based on this principle, the weight of the ink to be ejected can be changed in accordance with the rate of change when the potential of the piezo element PE is lowered (section d1, d2), that is, the drive waveform for driving the nozzles. . In this embodiment, the driving waveform for forming the small dot IPs and the medium dot IPm
Are prepared. FIG. 7 shows a driving waveform used in this embodiment. The drive waveform W1 is a waveform for forming small dots IPs, and the drive waveform W2 is a waveform for forming medium dots IPm. As shown in FIG. 7, as the ink weight increases, the flying speed increases. By properly using these drive waveforms, it is possible to form two types of small and medium dots from the nozzle Nz having a constant nozzle diameter. In the printer 22 of this embodiment, these drive waveforms are output continuously and periodically in the order of W1 and W2 as the carriage 31 moves.

Further, a large dot can be formed by forming a dot using both the drive waveforms W1 and W2 of FIG. This situation is shown in the lower part of FIG. FIG.
The lower part of the drawing shows the sheet P after the ink droplets IPs and IPm of small dots and medium dots ejected from the nozzles are ejected.
Up to. When two types of small and medium dots are formed using the driving waveform of FIG. 7, the medium dots eject the ink droplet IPm more vigorously. By adjusting the timing at which the small dot ink droplets IPs and the medium dot ink droplets IPm are continuously ejected in accordance with the flying speed difference of the ink and the moving speed of the carriage 31 in the main scanning direction, both inks can be adjusted. The droplet can reach the paper P at substantially the same timing. In this embodiment, a large dot having the largest dot diameter is thus formed from the two types of driving waveforms in the upper part of FIG.

In the printer 22 having the above-described hardware configuration, the carriage 31 is reciprocated by the carriage motor 24 (hereinafter, referred to as main scanning) while the paper P is transported by the paper feed motor 23 (hereinafter, referred to as sub-scanning). At the same time, the piezo elements PE of the respective color heads 61 to 66 of the print head 28 are driven to discharge the respective color inks,
A multicolor image is formed on the paper P by forming dots.

In this embodiment, as described above, the printer 22 having the head for discharging ink using the piezo element PE is used, but a printer for discharging ink by another method may be used. . For example, the present invention may be applied to a printer of a type in which a heater disposed in an ink passage is energized and ink is ejected by bubbles generated in the ink passage.

(2) Dot generation processing: Next, the dot generation processing in this embodiment will be described. FIG. 8 shows the flow of the dot generation processing routine. This is the computer 9
0 is a process executed by the CPU 81. When this process is started, the CPU 81 inputs image data (step S10). This image data is data passed from the application program 95 shown in FIG. 2, and includes 256 gradations of values 0 to 255 for each color of R, G, and B for each pixel constituting the image. This is data having a value. The resolution of the image data changes according to the resolution of the original image data ORG and the like.

The CPU 81 converts the resolution of the input image data into a resolution for printing by the printer 22 (step S12). If the image data ORG is lower than the printing resolution, resolution conversion is performed by generating new data between adjacent original image data by linear interpolation. Conversely, if the image data is higher than the print resolution,
Resolution conversion is performed by thinning out data at a fixed rate. Since the resolution conversion processing is not essential in the present embodiment, printing may be performed without performing such processing.

Next, the CPU 81 performs a color correction process (step S14). The color correction processing is to use image data composed of R, G, and B gradation values in
This is a process of converting into tone value data of each hue of M, Y, and K. This processing is performed for C, M, Y, C, M, Y,
A color correction table LUT storing combinations of K (FIG. 2)
Reference). Various well-known techniques can be applied to the processing itself for performing color correction using the color correction table LUT.
And the like described in US Pat.

The CPU 81 performs multi-value processing on the image data color-corrected in this way (step S20,
S50). The multi-value conversion means that the gradation value (256 gradations in this embodiment) of the original image data is converted into a gradation value that can be expressed by the printer 22 for each pixel. In this embodiment, for each ink, “non-formation of dots”, “formation of small dots”
Multi-leveling to four gradations of “formation of medium dots” and “formation of large dots” is performed. As shown in FIG. 5, in the present embodiment, cyan,
Magenta is provided with two types of dark and light inks. Regarding these hues, “Small dot formation”, “Medium dot formation”, “Large dot formation” with dark ink, “Small dot formation”, “Middle dot formation”, “Large dot formation” with light ink, and The multi-value conversion of "non-formation of dots" to seven gradations is performed.

For cyan and magenta, after performing a dark dot formation determination process (step S20), which is a multi-value process for dark ink, successively, a light dot formation determination, which is a multi-value process for light ink, is performed. The processing (step 50) is performed. 1 for yellow and black
Since only the types of ink are prepared, only the dark dot formation determination processing is performed (step S20), and the light dot formation determination processing is skipped. FIG. 8 mainly illustrates a case where two types of ink are provided to avoid complication of the flowchart. In this way, the multi-value processing for all colors is executed (step S80), and the dot generation processing routine ends. The multi-valued data is transferred to the printer 22 after being rearranged in the order of printing by the printer 22.

The multivalue processing of this embodiment will be described below. A description will be given of an example of cyan and magenta having two types of ink. For these hues, as described above, large dots, medium dots, and small dots (hereinafter, referred to as large large dots, dark medium dots,
On / off of six types of dots, called large and small dots formed by light ink, large dots, medium dots, and small dots (hereinafter referred to as light large dots, light medium dots, and light small dots, respectively)
By judging off, multi-value conversion of seven values is performed in total including non-formation of dots.

In the present embodiment, multi-value processing is performed so that each dot is printed at a predetermined printing rate according to the gradation data. FIG. 9 shows an example of the setting of the recording rate in the present embodiment. FIG. 9 is a table that gives the recording rates of six types of dots of large, medium, dark, small, light large, light middle, and light small for the gradation data. This table is stored in the ROM 82 of the computer 90. Level data is
This is data representing the recording rate in 8 bits (256 levels). The value 255 corresponds to a recording rate of 100%. The gradation data is a gradation value of each hue obtained by the color correction processing (Step S14 in FIG. 8). Of course, the recording rate of each type of dot can be set in various ways other than that shown in FIG. Note that the dot recording rate refers to the ratio of dots formed in a certain uniform gradation area to pixels in the area when the area is formed.

FIG. 10 is a flowchart of a dark dot formation determination processing routine in this embodiment. When this process is started, the CPU 81 reads the level data LD of the large dot from the table of FIG. 9 (step S22).
Then, based on the magnitude relationship between the level data LD and the threshold th, it is determined whether the large dot is on or off (step S24). The determination is made by the so-called dither method.

As the threshold th, a different value is set for each pixel by a so-called dither matrix. FIG.
(A) shows the concept of dot on / off determination by the dither method. For convenience of illustration, only some pixels are shown. As shown in FIG. 11, for each pixel, the level of the large dot level data LD is compared with the threshold stored in the corresponding portion of the dither table. When the level data LD is larger than the threshold value indicated in the dither table, the dot is turned on, and when the level data LD is smaller, the dot is turned off. In FIG. 11, the hatched pixels indicate the pixels that turn on the dots.

In this embodiment, a global blue noise mask type matrix in which values from 0 to 255 appear in 64 × 64 square pixels is used. FIG. 12 shows an example of a blue noise mask type dither matrix. For the sake of illustration,
Only a part of the matrix is shown. The use of such a matrix has a feature that the dispersibility of dots is good. If the dots are formed locally in a concentrated manner, the dots can be easily recognized and the image quality deteriorates. The use of a blue noise mask type matrix having good dot dispersibility has an advantage that multi-leveling with relatively excellent image quality can be performed. Of course, it goes without saying that various dither matrices can be applied to multi-value conversion.

In step S24, the level data L
When D is larger than the threshold th, it is determined that the large dot should be turned on, and the data of binary "11" is substituted for the result value Rd indicating the formation of the dot by the dark ink.
Each bit of the result value Rd corresponds to ON / OFF of the drive waveforms W1 and W2 shown in FIG. Result value RE
Is transferred to the driving buffer 47, a large dot is formed because ink is ejected by both the driving waveforms W1 and W2. In this case, the dark dot formation determination processing routine is terminated without performing the determination of the on / off state of the dark medium dot and the dark small dot.

In step S24, the level data L
If D is equal to or smaller than the threshold th, it is determined that the large dot should not be turned on, and the process proceeds to the determination of on / off of the medium dot. The method of determining the on / off state of the dark medium dot is substantially the same as that of the dark dot. CPU81
Reads the level data Ldm of the dark medium dot based on the table shown in FIG. 9 (step S28). The level data LD is corrected by adding the level data to the rich level data LD (step S30). Then, the magnitude of the corrected level data LD is compared with the threshold th (step S32). The threshold th is given by the same dither matrix as the large dot. If the corrected level data LD is larger than the threshold value th, it is determined that the dark medium dot should be turned on, and the binary value “01”, which means that, is substituted for the result value Rd. This result value Rd
Is sent to the printer 22, only the driving waveform W2 for forming a medium dot becomes valid, and a medium dot is formed. If it is determined that a medium dark dot is to be formed, the dark dot formation determination processing routine is terminated without determining whether the small dark dot is on or off.

FIG. 11B shows how to determine the ON / OFF state of the dark medium dot in this embodiment. FIG.
The lower part in (b) shows the level data Ldm of the dark medium dot read from FIG. In this embodiment, the sum of the level data and the level data LD of the previously read large dot is set as the corrected level data LD. The corrected level data is shown in the upper part of FIG. For pixels whose corrected level data LD is larger than the threshold value given by the dither table, it is determined that the medium dot should be turned on. Pixels indicated by hatching in FIG. 11B are pixels determined to be on. FIG.
In comparison with (a), it can be seen that the dark middle dot is turned on at pixels that do not overlap with the large dot.

The reason why the on / off state of the dark middle dot is determined using the level data LD thus corrected will be described. As an extreme example, in the setting of the recording rate shown in FIG. 9, an area where the gradation data is near the value 255, that is, an area where the level data of the middle dot is smaller than the level data of the large dot is considered. In such an area, when the on / off state of the dot is determined using the level data Ldm of the dark medium dot instead of the corrected level data LD, the pixel where the dark dot is turned off (the level data LD < At the time of th), the level data Ldm <th of the middle dark dot is always satisfied, so that the middle dark dot is also turned off. As a result, the recording rate of the dark medium dot becomes 0%, and the recording rate of FIG. 9 cannot be realized. Even in a region where the level data of the dark medium dot is larger than the level data of the large dot, the recording rate of the medium dot is lower than the recording rate set in FIG. 9 due to the same reason. In the present embodiment, the ON / OFF state of the dark medium dot is determined based on the sum of the level data Ldm of the dark medium dot and the level data LD of the heavy dot.
By judging off, it is possible to secure the recording rate of the dark medium dot set in FIG.

In step S32, the level data L
If D is equal to or smaller than the threshold th, it is determined that the dark medium dot should not be turned on, and the process proceeds to the determination of the dark small dot on / off. The method of determining on / off of the dark and small dots is almost the same as that of the other dots. CPU81
Reads the level data Lds of dark and small dots based on the table shown in FIG. 9 (step S36). This level data Lds is corrected by adding it to the level data LD (step S38). Level data LD before correction includes
Since the sum of the level data of the dark and large dots and the level data of the dark and medium dots is stored, at this point, the sum of the level data of the dark and large dots, the dark and medium dots, and the dark and small dots is the corrected level data LD. Will be stored. Then, the magnitude of the corrected level data LD is compared with the threshold th (Step S40). The reason why the corrected level data LD is used to determine the on / off state of the dark and small dots is based on the same reason as in the case of the dark and medium dots. By judging ON / OFF of the dots using such data, it is possible to form the small and large dots at the recording rate set in FIG. 9 while avoiding the overlap with the large and large dots and the dots in the capsule. It is.

The threshold value th is given by the same dither matrix as the large dot. Modified level data LD
Is larger than the threshold th, it is determined that the dark and small dots should be turned on, and the binary value “1” indicating that is turned on.
"0" is substituted for the result value Rd (step S42). When the result value Rd is sent to the printer 22, only the drive waveform w1 for forming a small dot becomes valid, and a small dot is formed. If the level data LD is equal to or smaller than the threshold th, it is determined that a dark dot should not be formed, and the result value R
Substitute “00” in binary for d. Thus, the CPU 8
1 ends the dark dot formation determination processing routine.

Next, the CPU 81 executes a light dot formation determination process (step S50). FIG. 13 shows a flowchart of the light dot formation determination process. When the light dot formation determination processing routine is started, the CPU 81 determines whether any of the dots formed with the dark ink is on (step S52). If the dark dot is on, the light dot on / off determination processing routine is ended without determining on / off of the light dot to avoid overlapping of the dots.

If the dark dot is not turned on,
The on / off determination of the light dots is performed by the same dither method as the formation determination of the dark dots. The CPU 81 reads the level data LL of the light large dot (step S54). The level data LL is given by the table shown in FIG. Next, the level data LL is corrected by adding the value of the level data LD used in the dark dot determination processing to the level data LL (step S56). The corrected level data LL stores the sum of the level data of all the dots formed by the dark ink and the level data of the light large dots. Then, the magnitude of the corrected level data LL is compared with the threshold th (Step S58). The threshold th is given by the same dither matrix used in the dark dot formation determination processing routine.

As described above, in this embodiment, the level data LL corrected by adding the level data of each dot formed by dark ink is used for the determination of the on / off state of the light dot.
By doing so, the dots formed by the dark ink,
An attempt is made to avoid overlapping with dots formed with light ink.

When the level data LL is larger than the threshold value th, it is determined that a light large dot is to be formed, and the result value Rl indicating the formation of the dot by light ink is "1" in binary.
The data of "1" is substituted (step S60). Result value R
The meaning of the value assigned to l is the same as the result value Rd of the dark dot. When it is determined that a light large dot is to be formed, the light dot formation determination processing routine is terminated without determining whether other dots are on or off.

If the level data LL is equal to or smaller than the threshold value th, it is determined that a large light dot should not be formed, and the process proceeds to a medium light dot determination. This determination method is similar to the other dot determination methods. The CPU 81 reads the level data Ldm of the light and medium dot (step S62), and corrects this value by adding it to the level data LL (step S6).
4). The corrected level data LL stores the sum of the level data of each dot formed by dark ink and the level data of light large dots. The level data LL is compared with the threshold th (step S6).
6) If the level data LL is larger than the threshold th, it is determined that a light and medium dot should be formed, and a value meaning it, that is, “01” in binary, is substituted for the result value Rl (step). 68).

If the level data LL is equal to or smaller than the threshold value th, it is determined that the medium light dot should not be formed, and the process proceeds to the light small dot determination. The CPU 81 reads the level data Lds of the light and small dots (step S70), and corrects this value by adding it to the level data LL (step S7).
2). The corrected level data LL stores the total sum of the level data of all the dots. The level data LL is compared with the threshold th (step S7).
4) If the level data LL is larger than the threshold th, it is determined that a light small dot is to be formed, and a value meaning it, that is, “10” is substituted for the result value Rl in a binary number (step). S78).

If the level data LD is equal to or smaller than the threshold th, it is determined that light and small dots should not be formed, and a value meaning it, that is, "00" in binary, is substituted for the result value Rd (step S1). S76). Thus, the CPU 81
Ends the light dot formation determination processing routine. By the above processing, for one hue, the determination of on / off of all the dots formed by the dark ink and the dots formed by the light ink is completed, and the seven-value conversion is completed. By executing this process for all hues and for all pixels, print data FNL is completed.

FIG. 14 shows how the state in which dots are formed by the processing of this embodiment changes in relation to gradation values. For convenience of illustration, 4 × 4 16 pixels are shown. It is assumed that dot on / off is determined using the dither matrix shown in FIG. This matrix is a kind of distributed matrix called Bayer type.

FIG. 14B shows how dots are formed in a region where the gradation data is relatively low.
The circles with hatching in the figure represent dots. This is a state in a range where only light and small dots are formed as in an area A1 in FIG. The recording rates of the dots other than the light and small dots are all zero. Therefore, based on the recording rate of the small light dots, the dots are turned on in the dither matrix (FIG. 14A) in order from the pixel with the smallest threshold. FIG.
(B) shows a state where the dot is turned on in a pixel having a threshold value of 4 or less.

FIG. 14C shows that the recording rate of light small dots is 1
This shows a state in an area of 00%. According to the setting of FIG. 9, the recording rates of the other dots are all 0 in this area.
It is. Therefore, as shown in FIG. 14C, small light dots are formed in all the pixels.

FIG. 14D shows a state in the gradation area where the formation of the middle-light dot begins. This corresponds to the area A2 in FIG. In such an area, only light small dots and medium light dots are formed. In addition, the sum of both recording rates is 1
It is set to be 00%. As described above, the on / off determination of the medium light dot is performed before the light small dot. Therefore, the light medium dots are formed in order from the pixel having the smaller threshold in the dither matrix (FIG. 14A) according to the recording rate. In FIG. 14D,
The state in which only one light and medium dot is formed in a pixel corresponding to the threshold value 1 is shown. A circle with a large diameter in FIG. 14D indicates a light medium dot. Light and small dots are formed in the remaining pixels.

FIG. 14E shows a state where the gradation value is further increased. This corresponds to the area A3 in FIG. This is an area where only small light dots and medium light dots are formed. As described above, light and medium dots are formed in order from the pixel having the smaller threshold value in the dither matrix. FIG. 14E shows a state in which light and medium dots are formed in a portion where the threshold value is 4 or less. Light and small dots are formed by other pixels. As described above, the number of pixels in which light and medium dots are formed increases in order from the pixel with the smaller threshold value of the dither matrix, and according to the recording rate setting shown in FIG.
0%.

FIG. 14F shows a state in a gradation area where light large dots begin to be formed. This corresponds to the area A4 in FIG. In such an area, only light medium dots and light large dots are formed. In addition, the sum of both recording rates is 1
It is set to be 00%. As described above, the determination of on / off of the light large dot is performed before the light medium dot. Therefore, the large light dots are formed in order from the pixel having the smaller threshold in the dither matrix according to the recording rate. FIG. 14F shows a state in which only one light and medium dot is formed in a pixel corresponding to the threshold value 1.
A large circle in FIG. 14F means a light large dot. The hatching pattern is shown in a different manner for discrimination from light and medium dots. Light and medium dots are formed in the remaining pixels.

FIG. 14 (g) shows a state where the gradation value is further increased. This corresponds to the area A5 in FIG. This is an area in which only light medium dots and light large dots are formed. FIG.
(G) shows a state where light large dots are formed in a portion where the threshold value is 4 or less. Light and medium dots are formed by other pixels. As described above, the number of pixels on which light large dots are formed increases in order from the pixel having the smaller threshold value of the dither matrix.

FIG. 14 shows the state of the gradation value at which only light dots are formed. In a region where dark dots are formed, the number of dark dots increases in a similar manner. That is, dark dots are formed in order from the pixel having the smaller threshold value of the dither matrix. In addition,
FIG. 14 shows only an example based on the recording rate shown in FIG. Depending on the setting of the recording rate, for example, the formation of light and medium dots may start before the light and small dots become 100%. Further, as the number of light and medium dots increases, the recording rate as a whole may temporarily decrease. Furthermore, three or more types of dots may coexist. In any case, there is no change in the tendency that the dot whose on / off is to be determined first is formed in a pixel having a smaller threshold value of the dither matrix.

According to the printing apparatus of the present embodiment described above, the on / off determination of the six types of dots is all performed by the dither method, so that the halftone processing can be executed at a very high speed. At this time, for the second and subsequent dots to be determined, ON / OFF is determined based on a value obtained by adding the recording rate of the previous dot. Therefore, it is possible to perform the halftone processing while securing the recording rate of each dot while avoiding the dots from being formed overlapping each other. By using the value obtained by adding the recording rate of the dots formed by the dark ink when determining the on / off state of the dots formed by the light ink, the dot formed by the dark ink and the dot formed by the light ink are used. Overlap can also be easily avoided.

In the above embodiment, the on / off of dots formed by dark ink is determined in order from the one with the largest amount of ink, and then the on / off of dots formed by light ink is determined from the one with the largest amount of ink. Judge in order. In general, dots formed with dark ink tend to be more visible than dots formed with light ink. In the above embodiment, by giving priority to dots formed by dark ink over dots formed by light ink, it is possible to determine ON / OFF with a high degree of freedom. As a result, the dispersibility of the dots formed by the dark ink is more appropriately secured, and high-quality printing can be realized.
This effect is particularly effective when the sum of the dot recording rates is set to a value exceeding 100%.

(3) Second Embodiment: Next, a printing apparatus according to a second embodiment of the present invention will be described. The hardware configuration of the printing apparatus according to the second embodiment is the same as that of the first embodiment (FIG. 1). In the second embodiment, the light dot formation determination processing routine of the dot generation processing routine (FIG. 8) is different from that of the first embodiment (step 20). The dark dot formation determination processing routine is the same as in the first embodiment.

FIG. 15 shows a flowchart of the light dot formation determination processing routine in the second embodiment. When this processing is started, the CPU 81 inputs a result value Rd designating formation of a dot with dark ink (step S10).
0). Further, correction data Cd in which the diffusion error is reflected in the gradation data is calculated (step S102). These values will be used in later processing.

The correction data Cd reflecting the diffusion error will be described. In the second embodiment, as described later, the on / off state of a small dot is determined by the error diffusion method. The correction data Cd is data used for this processing. In the error diffusion method, a local density error generated in a pixel for which dot on / off has been determined is diffused at a predetermined rate to peripheral unprocessed pixels. The pixel of interest for which dot on / off is to be determined reflects the error diffused from the processed pixel in the gradation data, and then determines dot on / off. The density error generated as a result of the on / off determination of the target pixel is further diffused to surrounding unprocessed pixels. FIG. 18 shows the error diffusion rate. The density error generated at the pixel of interest PP is diffused over several pixels in the scanning direction of the carriage and in the paper transport direction at the rate shown in the figure. In order to determine the ON / OFF state of the dot in this process, in step S102, the diffused error is reflected by adding it to the gradation data, and the correction data Cd is obtained. The on / off determination by the error diffusion method will be described later.

Next, the CPU 81 determines on / off of each dot formed by the light ink. First, C
The PU 81 reads the level data LL of the light large dot (step S104). This data is read from the table of FIG. 9 as in the case of the first embodiment. Then, the level data LL is compared with the threshold th (step S1).
06). If the level data LL is larger, it is determined that light large dots should be formed, and "11" is input as a binary number to the result value Rl for specifying the formation of light dots (step S108). The meaning of the value input to the result value Rl is the first
This is the same as in the embodiment.

In the light dot formation determination processing routine of the second embodiment, the processing of adding the dark dot level data LD to the light large dot level data LL is not performed (see step S56 in FIG. 13). In the second embodiment, the on / off state is determined using a dither matrix different from the dither matrix used for determining the dark dot. This is because if different dither matrices are used, it is possible to avoid the overlap between the dark dot and the light dot without adding the level data LD of the dark dot.

FIG. 16 shows an example of a dither matrix used in the second embodiment. For convenience of illustration, a dither matrix of 4 × 4 16 pixels will be described as an example. In the present embodiment, a dither matrix UM used for determining on / off of light dots is generated based on a dither matrix TM used for determining on / off of dark dots. As shown in the figure, the matrix UM is generated by moving the position of each component of the basic matrix vertically to the target. For example, the threshold value 1 located at the upper left in the basic matrix TM is located at the lower left in the matrix UM. In this embodiment, a new matrix is generated by exchanging the components of the basic matrix in this way.

In the present embodiment, in practice, the matrix UM is formed by associating the pixel to be processed with the dither matrix in a different relationship from the dark dot formation determination routine in the light dot formation determination routine. The same effect as that generated is obtained. The description will be made assuming that the coordinate values of each pixel in the paper transport direction are expressed as y = 0, 1, 2, 3,. The components in the paper transport direction of the dither matrix TM in FIG. 16 are My = 0, 1, 2, and 3. When determining a dark dot, the dither matrix TM is made to correspond to a pixel in a state where the dither matrix TM is correctly positioned. The relationship between the coordinate value y in the paper transport direction and the component My of the dither matrix TM is “My = y%
4 ". Here, “%” is a surplus operator. With this relationship, for example, a pixel represented by y = 0, 4, 8,... Corresponds to a threshold represented by a component of My = 0.

On the other hand, when the light dot is determined, the dither matrix is made to correspond to the pixel in a state where the dither matrix is inverted in the paper transport direction. Coordinate value y in paper transport direction and dither matrix T
The relationship between M and the component My is “My = 3-y% 4”.
If the correspondence is made in such a relationship, the following correspondence is obtained. pixels at y = 0, 4, 8,... → thresholds represented by components of My = 3; pixels at y = 1, 5, 9,... → thresholds represented by components of My = 2; y = Pixels of 2, 7, 10,... → thresholds represented by My = 1 components; y = 3, 8, 11,... Pixels → thresholds of My = 0 components; The same correspondence as that obtained by using the matrix UM is obtained. In the present embodiment, the correspondence between the pixels is switched in this manner, and the basic dither matrix TM is used, thereby saving the memory amount for storing the matrix.

FIG. 17 shows a state in which dots are formed by the dither matrix of this embodiment. The filled circles in the figure correspond to the dark dots, and the hatched circles correspond to the light dots. FIG. 17A shows a state in which one dark dot and one light dot are formed. Since the dark dot is determined using the dither matrix TM, it is formed at the upper left pixel with the smallest threshold.
Since the light dot is determined using the dither matrix UM, it is formed at the lower left pixel having the smallest threshold value.

FIG. 17B shows a state in which dark dots and light dots are formed at a recording rate of 50%. The dark dots are formed from the side of the dither matrix TM where the threshold is small, and the light dots are formed from the side of the dither matrix UM where the threshold is small. By using the dither matrices having different arrangements as described above, it is possible to prevent dark dots and light dots from being formed overlapping the same pixel.

The description returns to the light dot formation determination processing routine. In step S106, when the level data LL of the light large dot is equal to or smaller than the threshold th, it is determined that the light large dot should not be formed, and the process proceeds to forming the light medium dot. The level data Llm of the light and medium dots is read from the table of FIG. 9 (step S110), and the level data LL is read.
Is corrected by adding this value Llm to (step S1).
12). In the corrected level data LL, the sum of the level data of the light large dot and the level data of the medium light dot is stored. The magnitude of the level data LL is compared with the threshold th (step S114). The threshold th is a dither matrix used for light large dots, that is, U
Given by the dither matrix corresponding to M.

If the level data LL is larger than the threshold value th, it is determined that the light and medium dot should be turned on, and a binary value "01" meaning this is input to the result value Rl (step S116). . When it is determined that the light and medium dot should be turned on, the determination of on / off of the light and small dot is not performed.

If the level data LL is equal to or smaller than the threshold value th, the process proceeds to the determination of on / off of the small light dot. In the second embodiment, the ON / OFF determination of the small light dots is performed by the error diffusion method. The light and small dots are turned on and off using the correction data Cd previously calculated in step S102. C
The PU 81 compares the magnitude of the correction data Cd with the threshold Ted (step S118). Here, the threshold value Ted is a preset constant value. The threshold Ted can be set to any value. In this embodiment, the value is set to a value corresponding to the density evaluation value of the small light dot. When the correction data Cd is equal to the threshold Ted
If it is larger, it is determined that a light small dot is to be formed, and the binary value “10” indicating the small dot is set to the result value Rl.
(Step S120). If the correction data Cd is equal to or smaller than the threshold value Ted, it is determined that a small light dot is not to be formed, and a binary value “00” meaning this is substituted for the result value Rl (step S122).

By the above processing, the result value Rd for specifying the formation of a dark dot and the result value Rl for specifying the formation of a light dot
And was identified. That is, the target pixel PP to be processed is converted into seven values. The CPU 81 performs error calculation and error diffusion processing based on the result values Rd and Rl (step S124). The error refers to an error between the density expressed when a dot is formed in the target pixel PP according to the multi-level quantization result and the density to be expressed based on the correction data Cd. The density expressed when a dot is formed on the target pixel PP is obtained based on a density evaluation value RV preset for each pixel.

The error ERR is obtained by using the correction data Cd and the density evaluation value RV as ERR = RV-Cd. For example, assuming that the density evaluation value of a large dot is equivalent to 255 in gradation data, if a large dot is formed even though the correction data Cd has a value of 199, there is 199-255. That is, a density error of −56 has occurred. This means that the expressed density is too high.

The error diffusion is a process of diffusing the error obtained in this way by assigning a predetermined weight to pixels around the pixel PP currently being processed. FIG. 18 shows weight values applied in this embodiment. Since the error should be diffused to the unprocessed pixels, as shown in FIG. 18, it is diffused only to the pixels arranged in the scanning direction of the carriage and the transport direction of the sheet. If the error is “−56”, “−14” corresponding to 相当 of the error “−56” is diffused to the pixel P1 adjacent to the pixel PP currently being processed. This error is reflected in step S102 the next time the pixel P1 is processed. For example, if the gradation data of the pixel P1 is the value 214, the correction data Cd is set to the value 200 by adding the diffused error “−14”. By repeatedly executing such processing, it is possible to perform halftone processing in which local density errors are minimized.

According to the printing apparatus of the second embodiment described above, very high-quality printing can be realized at high speed. When dot on / off is determined by the dither method, a local error generated between the density expressed according to the result and the density to be expressed according to the gradation data may be relatively large. is there. In the printing apparatus according to the second embodiment, for light and small dots, the ON / OFF of other dots is performed.
The on / off state is determined by an error diffusion method in consideration of the density error generated in accordance with the off state. Therefore, local density errors can be suppressed, and high-quality printing can be performed. Here, in the printing apparatus of the second embodiment, the error diffusion method which requires a long time for processing is applied only to small dots, and the other dots are turned on / off by the dither method. Increase can be suppressed.

In the second embodiment, dither matrices having different arrangements are used in the dark dot formation determination routine (FIG. 10) and the light dot formation determination routine (FIG. 15). Further, in each routine, as in the first embodiment, the dot on / off determination is performed after adding the dot level data determined before. By applying such a process, it is possible to prevent dots formed by the dither method from being formed overlapping each other. As in the first embodiment, the same dither matrix is applied in both routines, and the on / off determination is performed after the dark dot recording rate is reflected in the light dot recording rate. You can also.

In the above-described embodiment, an example has been described in which dots are formed with three types of ink weights, large, medium, and small, with two types of inks of different shades. The present invention is applicable even when the ink concentration and the ink weight are different from these.

In each of the above embodiments, the ink jet printer 22 has been described as an example. In the above-described embodiment, an ink jet printer having a piezo element has been described as an example. However, various types of printers, such as a printer that discharges ink by bubbles generated in ink by energizing a heater provided in a nozzle, and other printing apparatuses Applicable to the device. Further, the present invention can be applied to a printing apparatus other than a printer as long as the apparatus expresses an image by assigning dots to each pixel.

Since the printing apparatus described above includes processing by a computer, the printing apparatus can also be implemented as a recording medium on which a program for realizing such processing is recorded. Examples of such a recording medium include a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punched card, a printed matter on which a code such as a bar code is printed, and a computer internal storage device (such as a RAM or ROM). memory)
And various computer-readable media such as an external storage device. Further, an embodiment as a program supply device for supplying a computer program for performing the above-described image processing and the like to a computer via a communication path is also possible.

Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various embodiments can be made without departing from the gist of the present invention. For example, various control processes described in the above embodiments may be partially or entirely realized by hardware.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a printing apparatus according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a software configuration of the printing apparatus according to the embodiment.

FIG. 3 is a schematic configuration diagram of a printer 22.

FIG. 4 is an explanatory diagram illustrating a dot forming principle of the printer 22.

FIG. 5 is an explanatory diagram showing an example of a nozzle arrangement of the printer 22.

FIG. 6 is an explanatory diagram illustrating the principle of forming dots having different diameters by the printer 22.

FIG. 7 is an explanatory diagram illustrating the principle of forming a large dot by the printer 22.

FIG. 8 is a flowchart of a dot generation processing routine.

FIG. 9 is an explanatory diagram showing a set value of a dot recording rate in the embodiment.

FIG. 10 is a flowchart of a dark dot formation determination processing routine.

FIG. 11 is an explanatory diagram showing a concept of dot on / off determination by a dither method.

FIG. 12 is an explanatory diagram showing a part of a dither matrix in the present embodiment.

FIG. 13 is a flowchart of a light dot formation determination processing routine.

FIG. 14 is an explanatory diagram showing how dots are formed according to the present embodiment.

FIG. 15 is a flowchart of a light dot formation determination processing routine according to the second embodiment.

FIG. 16 is an explanatory diagram showing a dither matrix relationship in the second embodiment.

FIG. 17 is an explanatory diagram showing how to form dark dots and light dots in the second embodiment.

FIG. 18 is an explanatory diagram showing setting of weight values in the error diffusion method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Scanner 14 ... Keyboard 15 ... CD-ROM drive 16 ... Hard disk 18 ... Modem 21 ... Color display 22 ... Color printer 23 ... Paper feed motor 24 ... Carriage motor 26 ... Platen 28 ... Print head 31 ... Carriage 32 ... Operation panel 34 ... Sliding shaft 36 ... Driving belt 38 ... Pulley 39 ... Position detection sensor 40 ... Control circuit 61-66 ... Ink ejection head 67 ... Introduction pipe 68 ... Ink passage 71 ... Black ink cartridge 72 ... Color ink cartridge 80 ... Bus 81 ... CPU 82 ... ROM 83 ... RAM 84 ... Input interface 85 ... Output interface 86 ... CRTC 87 ... Disk controller (DDC) 88 ... Serial input / output interface (SIO) 90 ... Personal computer 91 ... video driver 95 ... application program 96 ... printer driver 97 ... resolution conversion module 98 ... color correction module 99 ... halftone module 100 ... rasterizer

[Procedure amendment]

[Submission date] April 14, 1999 (1999.4.1
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

According to a second printing method of the present invention, two or more kinds of inks having the same hue and different densities are provided, and two or more kinds of inks formed by changing the ink weight with at least one of the inks. A printing method for printing a multi-tone image by a distribution of the dots by using a head capable of forming three or more types of dots including a dot on a print medium, wherein (a) a tone of an image to be printed A step of inputting data; and (b) a predetermined number of dots formed by the same ink in each pixel in a continuous order in the order of ink weight, and a predetermined number of dots from the dot having the lowest density evaluation value to the dot having the lowest density evaluation value.
And determining the sequential on-off Dot excluding dot, (c) a predetermined number of dots of the density evaluation value is low side
(D) determining the on / off state of the dot by an error diffusion method based on the correction data in which the density error generated in accordance with the on / off state of the other dots is also reflected in the gradation data; Driving the head according to the result to form the respective types of dots.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

The operation of the printing method is performed by setting the predetermined number to a value of 1.
An example will be described. In such a case, the dot with the lowest density evaluation value and the other dots are turned on and off.
The method of determining off is different. For the dot having the lowest density evaluation value, ON / OFF of the dot is determined by the error diffusion method, and for the other dots, ON / OFF is determined by the dither method.
In the determination by the dither method, that is, in the step (b), as in the case of the first printing method, it is possible to determine the on / off state while ensuring the dispersibility of dots of the same hue.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

Here, the operation has been described by taking as an example the case where the predetermined number is the value 1, that is, the case where the target to which the error diffusion method is applied is a dot having the lowest density evaluation value. The dot having the lowest density evaluation value is hard to be visually recognized. Therefore, if the error diffusion method is applied to such dots, local density errors can be eliminated without making the dots stand out. In addition,
A predetermined number within the range that satisfies the processing time requirement
May be set to a value of 2 or more, and the dots to which the error diffusion method is applied may be extended to a plurality of dots on the lower side of the density evaluation value.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

The second recording medium of the present invention comprises two or more types of inks having the same hue and different densities, and two or more types of inks formed by changing the ink weight with at least one of the inks. A computer readable recording medium for recording a program for printing an image by a printing apparatus capable of forming three or more types of dots including dots on a printing medium, and inputting gradation data of the image to be printed. The function and the dots formed by the same ink for each pixel are consecutive in the order of ink weight,
From the dot with the lowest density evaluation value to the lowest density evaluation value
A dither determination function for sequentially determining ON / OFF for dots excluding a predetermined number of dots ;
A function of determining on / off of a predetermined number of dots by an error diffusion method based on correction data in which a density error generated in accordance with on / off of other dots is also reflected in the gradation data; A function of driving the head in accordance with the result to form the respective types of dots; and a function of setting the recording rate of each dot based on the gradation data. When,
A function of determining on / off of a dot to be determined first based on a magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix; When there is a dot that is determined, the priority is given to the pixels excluding the pixel in which any of the previously determined dots have been turned on, and the recording rate of the previously determined dot is determined. A recording medium on which is recorded a program which is a function of judging on / off of each dot by a function of judging on / off of the dot based on a magnitude relationship between the reflected recording rate and the threshold value.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

The second printing apparatus of the present invention includes two or more types of inks having the same hue and different densities, and two or more types of inks formed by changing the ink weight with at least one of the inks. A printing apparatus, comprising: a head capable of forming three or more types of dots including dots on a print medium, capable of printing a multi-tone image based on the distribution of the dots, and inputting tone data of an image to be printed. Input means, and for each pixel, the dots formed by the same ink are successively arranged in the order of ink weight, excluding a predetermined number of dots from the dot having the lowest density evaluation value to the dot having the lowest density evaluation value. before dither determination unit that determines on-off, with <br/> a predetermined number of dots of the density evaluation value is low side, also the density error occurring in response to the other of the dot on-off Error diffusion determination means for determining on / off by an error diffusion method based on the correction data reflected on the gradation data, and dots for forming the respective types of dots by driving the head according to the determination result Forming means, wherein the dither determination means stores a relationship between the recording rate of each dot and gradation data, and refers to the storage means to determine the recording rate of each dot by the gradation. A setting means for setting according to the data, a value reflecting the recording rate for the dot for which the ON / OFF was previously determined for the recording rate for the dot to be determined, and a dither matrix prepared in advance. On the basis of the magnitude relation with the stored threshold value, a dot for which ON / OFF of the dot is prioritized for a pixel other than a pixel in which any of the previously determined dots has been turned ON. The gist of the present invention is to determine on / off of each dot by the formation determining unit. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 10, 1999 (1999.9.1
0)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] Claim 9

[Correction method] Change

[Correction contents]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] Claim 12

[Correction method] Change

[Correction contents]

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] Claim 17

[Correction method] Change

[Correction contents]

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] Claim 20

[Correction method] Change

[Correction contents]

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

Here, the step (b) includes: (b1) a step of setting a recording rate of each dot based on the gradation data; and (b2) a step of setting the recording rate for the first dot to be determined. Based on the magnitude relationship between the rate and the threshold value stored in the previously prepared dither matrix, the on / off state of the dot is determined.
And (b3) for the second and subsequent dots to be determined, in order from the pixel in which any of the previously determined dots has been turned off, in order from the pixel whose recording rate is off. Determining the on / off state of each dot based on the magnitude of the recording rate reflecting the recording rate of the determined dot and the threshold value.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

Here, the step (b) includes: (b1) a step of setting the recording rate of each of the dots based on the gradation data; and (b2) a step of setting the recording rate for the first dot to be determined. Based on the magnitude relationship between the rate and the threshold value stored in the dither matrix prepared in advance, the ON / OFF of the dot is determined.
(B3) When there is a dot to be determined in the second and subsequent steps, any of the previously determined dots is turned off in order from the pixel in which it is off .
Determining the on / off state of each dot based on a magnitude relationship between the recording rate reflecting the recording rate of the dot previously determined according to the recording rate of the dot and the threshold value. This is the step of determining.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

The above-described printing method is generally realized by driving a printing apparatus based on data processed by a computer based on a predetermined program. Therefore, the printing method of the present invention is also realized as a recording medium on which such a program is recorded. The first recording medium of the present invention includes two or more types of inks having the same hue and different densities, and includes two or more types of dots formed by changing the ink weight with at least one of the inks. A computer-readable recording medium for recording a program for printing an image by a printing apparatus capable of forming three or more types of dots on the printing medium, the function of inputting gradation data of an image to be printed; The dots formed by the same ink are sequentially determined in the order of ink weight, and a determination function for sequentially determining ON / OFF for each dot for each pixel, and driving the head according to the determination result, A function of forming each type of dot can be realized, and the determination function sets the recording rate of each dot based on the gradation data. Features and a first Dot to be determined, function to determine the on-off of the dot on the basis of the magnitude relation between the recording rate and a prepared dither matrix stored threshold,
Regarding the second and subsequent dots to be determined, one of the previously determined dots is off.
In order from the pixels, the function of determining the ON / OFF of each dot based on the magnitude relationship between the recording rate reflecting the recording rate of the dot previously determined in accordance with the recording rate of the dot and the threshold value has been described. This is a recording medium that records a program that is a function of determining ON / OFF.

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

The second recording medium of the present invention comprises two or more types of inks having the same hue and different densities, and two or more types of inks formed by changing the ink weight with at least one of the inks. A computer readable recording medium for recording a program for printing an image by a printing apparatus capable of forming three or more types of dots including dots on a printing medium, and inputting gradation data of the image to be printed. The function and the dots formed by the same ink for each pixel are consecutive in the order of ink weight,
A dither determination function for sequentially determining ON / OFF for dots excluding a predetermined number of dots in order from a dot having the lowest density evaluation value to a dot having the lowest density evaluation value; A function of determining on / off by an error diffusion method based on correction data in which a density error generated according to dot on / off is also reflected in the gradation data, and driving the head in accordance with the determination result And the function of forming the respective types of dots can be realized, and the dither determination function is a function of setting the recording rate of each dot based on the gradation data;
A function of determining on / off of a dot to be determined first based on a magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix; If there is to become dot, one dot off became determination target previously
In order from the pixel having the function of determining the on / off of the dot based on the magnitude relationship between the recording rate reflecting the recording rate of the dot previously determined according to the recording rate of the dot and the threshold. This is a recording medium on which a program for recording ON / OFF of each dot is recorded.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

The above-described printing method of the present invention can be realized by executing the program recorded on each of the recording media by a computer. In addition, as a storage medium, a flexible disk or a CD-RO
M, a magneto-optical disk, an IC card, a ROM cartridge, a punched card, a printed matter on which a code such as a bar code is printed, a computer internal storage device (RAM or ROM)
A variety of computer-readable media can be used, such as a memory (e.g., memory) and an external storage device. Also, a server that supplies a computer program for realizing the multi-level function of the image processing apparatus to a computer via a communication path.
The embodiment as a bar is also included.

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

The present invention is also realized in a printing apparatus capable of realizing the above-described printing method. The first printing apparatus of the present invention includes two or more types of inks having the same hue and different densities, and includes two or more types of dots formed by changing the ink weight with at least one of the inks. What is claimed is: 1. A printing apparatus comprising: a head capable of forming three or more types of dots on a printing medium; and a printing apparatus capable of printing a multi-tone image based on the distribution of the dots. And dither determining means for sequentially determining ON / OFF of each dot for each pixel in the order in which the dots formed by the same ink are continuous in the order of ink weight, and driving the head according to the determination result Dot forming means for forming the respective types of dots, wherein the dither determining means stores a relationship between a recording rate of each dot and gradation data. And,
With reference to the storage means, setting means for setting the recording rate of each dot in accordance with the gradation data, and ON / OFF has been previously determined for the recording rate of the dot to be determined. A value reflecting the dot recording rate,
On the basis of a magnitude relationship with a threshold value stored in a previously prepared dither matrix, dot formation for judging on / off of any of the previously determined dots is sequentially performed from a pixel in which the dot is off. The gist of the present invention is that the determination means determines whether each dot is on or off.

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

The second printing apparatus of the present invention includes two or more types of inks having the same hue and different densities, and two or more types of inks formed by changing the ink weight with at least one of the inks. A printing apparatus, comprising: a head capable of forming three or more types of dots including dots on a print medium, capable of printing a multi-tone image based on the distribution of the dots, and inputting tone data of an image to be printed. Input means, and for each pixel, the dots formed by the same ink are successively arranged in the order of ink weight, excluding a predetermined number of dots from the dot having the lowest density evaluation value to the dot having the lowest density evaluation value. Dither determination means for determining on / off, and for a predetermined number of dots on the lower side of the density evaluation value, a density error generated in accordance with on / off of other dots is also determined by the above-mentioned factor. Error diffusion determining means for determining on / off by an error diffusion method based on correction data reflected in data, and dot forming means for driving the head according to the determination result to form the respective types of dots Wherein the dither determination means comprises: storage means for storing a relationship between the recording rate of each dot and gradation data; and referring to the storage means, the recording rate of each dot is stored in the gradation data. Setting means for setting in accordance with the setting, a value reflecting a recording rate for a dot for which ON / OFF has been previously determined with respect to a recording rate for a dot to be determined, and a value stored in a previously prepared dither matrix. was based on the magnitude relationship between the threshold value, in order from the pixels either became determination target previously dots are turned off, the dot formation determination hand determines on-off of the dot And summarized in that a means for determining the respective dot on-off by the.

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0108

[Correction method] Change

[Correction contents]

Since the printing apparatus described above includes processing by a computer, the printing apparatus can also be implemented as a recording medium on which a program for realizing such processing is recorded. Examples of such a recording medium include a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punched card, a printed matter on which a code such as a bar code is printed, and a computer internal storage device (such as a RAM or ROM). memory)
And various computer-readable media such as an external storage device. Further, an embodiment as a server that supplies a computer program for performing the above-described image processing and the like to a computer via a communication path is also possible.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2C057 AG44 AM15 AM16 DA05 DC02 2C262 AA02 AA24 AB13 AB19 AC07 AC11 BB03 BB06 BB08 BB10 BB16 BB19 BB27 BC07 BC17 5C074 AA02 BB16 CC26 DD05 DD24 DD28 EE08 FF08 H04 MPC NN02 NN05 NN08 NN12 PP15 PQ12 PQ22 RR09 RR14 SS02 SS05 TT05

Claims (10)

[Claims] 1. Three or more types of dots including two or more types of inks having the same hue and different densities, and including two or more types of dots formed by changing the ink weight with at least one of the inks. A printing method for printing a multi-gradation image by the distribution of dots by using a head capable of forming the image on a printing medium, wherein (a) inputting gradation data of an image to be printed; b) determining the on / off state of each dot for each pixel in the order in which the dots formed by the same ink are continuous in the order of ink weight; and (c) controlling the head in accordance with the determination result. Driving to form the respective types of dots, wherein the step (b) comprises: (b1) a step of setting the recording rate of each dot based on the gradation data; and (b2) (B3) determining the on / off state of a dot to be initially determined based on a magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix; With respect to the dots to be determined, priority is given to pixels other than the pixels for which any of the previously determined dots have been turned on, and the recording rate of the previously determined dot is reflected to the recording rate of the dot. Determining whether the dots are on or off based on the magnitude relationship between the recording rate and the threshold value. 2. The printing according to claim 1, wherein the step (b) is a step of determining on / off of the respective types of dots in order from a higher density of ink forming the dots to a lower density. Method. 3. The printing method according to claim 1, wherein the dots that can be formed by the head are formed by two or more ink weights each with a high density dark ink and a low density light ink. In the step (b), on / off of dots formed by dark ink is determined in descending order of ink weight, and then on / off of dots formed by light ink is determined by ink weight. Printing method, which is a step of determining in descending order. 4. Three or more types of dots including two or more types of inks having the same hue and different densities, and including two or more types of dots formed by changing the ink weight with at least one of the inks. A printing method for printing a multi-gradation image by the distribution of dots by using a head capable of forming the image on a printing medium, wherein (a) inputting gradation data of an image to be printed; b) for each pixel, determining dots formed by the same ink in order of ink weight, and sequentially determining ON / OFF for dots excluding the dot having the lowest density evaluation value;
(C) For a dot having the lowest density evaluation value, the on / off determination is made by an error diffusion method based on the correction data in which the density error caused by the on / off of the other dots is also reflected in the gradation data. And (d) driving the head according to the determination result to form the respective types of dots. The step (b) comprises: (b1) determining a recording rate of each of the dots. (B2) turning on the dot to be initially determined based on the magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix. The step of judging off, and (b3) if there is a second or subsequent dot to be judged, priority is given to pixels excluding pixels for which any of the previously judged dots have been turned on. hand Determining the on / off state of each dot based on a magnitude relationship between the recording rate reflecting the dot recording rate previously determined according to the dot recording rate and the threshold value. A printing method which is a step of determining 5. The printing method according to claim 4, wherein the step (b) further comprises: (b0) generating a dither matrix for giving a threshold value in a different arrangement for each type of ink from the dither matrix stored in advance. (B2) using a dither matrix corresponding to each ink formed by the same ink for each dot formed with the same ink.
And (b3) to determine ON / OFF. 6. The printing method according to claim 4, wherein the dots that can be formed by the head are each formed by two or more stages of ink weight with high density dark ink and low density light ink. The dots having the lowest density evaluation value are the dots having the lowest ink weight formed by the light ink, and the step (b) is performed by first forming the dark ink with the exception of the dots. A printing method for determining on / off of dots to be formed in descending order of ink weight, and then determining on / off of dots formed by light ink in descending order of ink weight. 7. Three or more types of dots including two or more types of inks having the same hue and different densities, and including two or more types of dots formed by changing the ink weight with at least one of the inks. Is a computer-readable recording medium for recording a program for printing an image by a printing device capable of forming an image on a print medium, the function of inputting gradation data of an image to be printed, and the same ink A determination function for sequentially determining ON / OFF for each of the dots in each pixel in a continuous order in the order of ink weight; and driving the head in accordance with the determination result to drive the respective types of dots. A function of setting the recording rate of each dot based on the gradation data; and A function of determining on / off of a dot to be determined first based on a magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix; and a second and subsequent determination targets. With respect to the dot to be determined, the recording rate reflecting the recording rate of the previously determined dot is prioritized to the pixels excluding the pixel in which any of the previously determined dots has been turned on. A recording medium on which is recorded a program which is a function of determining the ON / OFF of each dot by a function of determining the ON / OFF of the dot based on the magnitude relationship between the threshold and the threshold. 8. Three or more types of dots including two or more types of inks having the same hue and different densities, and including two or more types of dots formed by changing the ink weight with at least one of the inks. A computer-readable recording medium for recording a program for printing an image by a printing device capable of forming the image on a printing medium, the function of inputting gradation data of an image to be printed, A dot formed by the same ink has a dither determination function of sequentially determining ON / OFF for dots excluding the dot having the lowest density evaluation value in the order in which the dots have the lowest density evaluation value. The density error generated in accordance with the on / off of the dot is also turned on by the error diffusion method based on the correction data reflecting the gradation data. And a function of driving the head in accordance with the determination result to form the respective types of dots, and the dither determination function can determine the recording rate of each dot. Is set on the basis of the gradation data, and on / off of the dot to be initially determined based on the magnitude relationship between the recording rate and a threshold value stored in a previously prepared dither matrix. Function, and if there is a dot to be determined after the second,
A priority is given to the pixels excluding the pixels in which any of the dots that were previously determined to be on are turned on, and the recording rate of the dot and the recording rate that reflects the recording rate of the dot that was previously determined and the threshold are compared. A recording medium on which a program is recorded, which is a function of judging on / off of each dot by a function of judging on / off of the dot based on a magnitude relation. 9. Three or more types of dots including two or more types of inks having the same hue and different densities, and including two or more types of dots formed by changing the ink weight with at least one of the inks. A printing device, comprising: a head capable of forming an image on a print medium, and capable of printing a multi-tone image by the distribution of dots, wherein input means for inputting tone data of an image to be printed; Dither determining means for sequentially determining ON / OFF for each of the dots for each pixel in the order in which the dots are formed in the order of the ink weight; and driving the heads according to the determination result to drive the respective Dot forming means for forming a type of dots; the dither determining means; a storing means for storing a relationship between a recording rate of each dot and gradation data; Setting means for setting the recording rate of each dot in accordance with the gradation data with reference to the storage means; and a dot which has been previously determined to be on / off with respect to the recording rate of the dot to be determined. Based on the magnitude relationship between the value reflecting the recording rate for and the threshold value stored in the dither matrix prepared in advance, pixels other than the pixels for which any of the previously determined dots were turned on are excluded. A printing apparatus which is a means for determining on / off of each dot by a dot formation determining means for determining on / off of the dot by priority. 10. Three or more types of dots including two or more types of inks having the same hue and different densities, and including two or more types of dots formed by changing the ink weight with at least one of the inks. A printing device capable of printing a multi-tone image according to the distribution of dots, comprising: a head capable of forming a tone on a print medium; and an input unit for inputting tone data of an image to be printed; In addition, dither determination means for sequentially determining ON / OFF for dots excluding the dot having the lowest density evaluation value in the order in which dots formed by the same ink are consecutive in the order of ink weight, and for the dot having the lowest density evaluation value, Also, the on / off state is determined by an error diffusion method based on the correction data that reflects the density error generated in accordance with the on / off state of the other dots in the gradation data. Error diffusion determining means, and dot forming means for driving the head according to the determination result to form the respective types of dots, wherein the dither determining means comprises a recording rate and a gradation of each dot. Storage means for storing a relationship with data; setting means for setting a recording rate of each dot in accordance with the gradation data with reference to the storage means; and a recording rate for a dot to be determined. On the other hand, based on a magnitude relationship between a value reflecting the recording rate of a dot for which on / off has been previously determined and a threshold value stored in a previously prepared dither matrix, one of the previously determined determination targets Means for giving priority to the pixels excluding the pixels for which the dot is turned on, and for determining whether each dot is on or off by means of dot formation determining means for determining whether the dot is on or off. Printing apparatus.