CN1726455B - Print system and printing method - Google Patents

Abstract

When overlap print requiring at least two dot forming elements for forming one raster is performed using a print head having a plurality of dot forming elements, a larger memory capacity is required for storing dot data. In the inventive print system, an image processor performs first half image processing and delivers intermediate data to a printer under a state requiring development to a plurality of pixels. The printer develops intermediate data including a remarked pixel for which the presence of dot formation is judged, and then judges for the presence of dot formation of the remarked pixel based on that data. When the intermediate data including a remarked pixel is developed every time when the presence of dot formation is judged for the remarked pixel, a large memory capacity is not required for image processing on the printer side. Consequently, image processing can be born effectively between the image processor and the printer even if a storage capacity is low on the printer side and thereby the processing capacity is low.

Description

Printing system and printing method thereof

technical field

The present invention relates to a technique for printing after applying predetermined image processing to an image. Specifically, it relates to a technique for printing an image by sharing the image processing with an image processing device and a printing device. the

Background technique

A printing device that prints an image by forming ink dots on a printing medium is widely used as an output device of various image machines. In such a printing device, an image is processed in a state of being subdivided into small regions called pixels, and ink dots are formed on these pixels. Such a printing device can only express the state of ink dots formed or not formed for each pixel, but it can generate densely formed areas and sparsely formed areas when viewed from the entire image. For example, when dots of black ink are formed on printing paper, areas where dots are densely formed appear darker, whereas areas where dots are sparsely formed appear brighter. Therefore, if the formation density of ink dots is properly controlled in accordance with the gradation value of the image to be expressed, a multi-gradation image can be printed. the

In such a printing device, the following method is generally used to form ink dots with a density corresponding to the gradation value of an image. First, predetermined image processing is performed on an image to be printed, and the image data is converted pixel by pixel into data indicating whether ink dots are formed (hereinafter referred to as “dot data” in this specification). If appropriate image processing is performed on the image, ink dot data for forming ink dots at an appropriate density according to the gradation value of the image data can be generated. Then, the obtained ink dot data indicating whether ink dots are formed or not is supplied to the printing device. In the printing device, ink dots are formed on each pixel based on the data thus sent. In this way, ink dots can be formed at an appropriate density according to the gradation of image data, and a desired image can be printed. the

However, if an image is printed using this method, the number of pixels constituting the image will increase, and it will take time to transmit the image processing data, making it difficult to perform quick printing. Especially in recent years, with the improvement of image quality and the demand for larger format, the number of pixels constituting an image tends to increase, and it is gradually becoming more and more difficult to print images quickly. This subject is described in detail in, for example, JP-A-2000-115716. the

Such ink dots are formed on a printing medium such as printing paper by a dot forming element provided in a printing head, for example, a nozzle that ejects ink droplets. Thereby, if there is deviation in the ink dot formation of this ink dot forming element, such as the deviation of the landing position of the ink drop when forming ink dots with ink droplets, etc., the wire grid (raster) formed by the ink drop forming element will be different from other ink dots. The wire grid is different, and it is easy to insert white lines on the printed matter, that is, the so-called banding phenomenon (banding). Therefore, in a recent printing apparatus, one line grid is formed using at least two dot forming elements provided in a printing head. In this case, in a printing device of the type in which printing is performed by reciprocating the print head relative to the printing medium, one raster is completed by multiple reciprocating or reciprocating movements. That is, first use one ink dot forming element to form ink dots at intermittent positions (for example, one position apart), and if the relative positional relationship between the print head and the printing medium deviates, another ink dot forming element is used to form ink dots. , to fill the spaces of the ink dots that have been formed to complete the wire grid. This method is called overlap. the

However, if this method of forming ink dots is used, there will be a problem that all the already generated ink dot data must be stored until the print head is moved without being used directly. Originally, a method in which a plurality of ink dot forming elements are arranged on the printing nozzle by the amount of several ink dots apart, and the printing nozzle moves forward or back multiple times to first complete a line grid of a certain width (interlaced :interlace), if it is overlapped again, the amount of ink dot data that must be saved will jump and increase. As a result, in order to store a large amount of ink dot data, a large-scale memory has to be used. the

Furthermore, the processing from the original image data to the final printing may be shared between the image processing device (generally a computer) and the printing device, or all the processing may be performed by the printing device side. In either case, there must be a process of storing the dot data according to the development and storage of the dot forming elements, so there is no change in the fact that a large-scale memory is required. When an image processing device and a printing device are combined to form an image, the generation of ink dot data can be performed by the image processing device. In general, an image processing device is realized by running an application program on a computer to perform predetermined processing, and when printing, activates a printer driver, receives necessary data from the application program, and generates data to be output to the printing device. At this time, although enough memory can be prepared on the computer side to expand and store a large amount of ink dot data on the print driver side, another problem will be caused, that is, the amount of data transmitted from the image processing device to the printing device will increase. , Data transmission takes time. the

Contents of the invention

The present invention is intended to solve the above-mentioned problems in the prior art, and an object of the present invention is to provide a technique for efficiently performing image processing by reducing the memory capacity required for developing ink dot data. the

In order to solve at least part of the above-mentioned problems, the present invention provides a printing head that includes a plurality of dot forming elements that form a plurality of ink dots on a printing medium, and uses at least 2 of the printing head to form each grid of pixels. ink dot forming element printing. At this time, the original image data is converted into converted data which is data in a form compressed before being expanded into dot data corresponding to a plurality of dot forming elements, and is compressed. stored in memory. Thereafter, the converted data is sequentially read, and the dot data for driving a plurality of dot forming elements is developed, and printing is performed by driving the dot forming elements accordingly. Thus, with the present invention, since image data can be stored in a compressed form, a large storage capacity is not required. In addition, since the compressed data is expanded to dot data and the dot forming elements are driven, the capacity of the dot data can also be reduced. the

In addition, when such a printing system is constituted by an image processing device and a printing device, and the processing is shared by the two devices, the image processing can be efficiently shared between the image processing device and the printing device. At this time, it can be freely designed in which of the image processing device and the printing device the respective units constituting the printing system are incorporated. For example, processing such as color correction can be performed outside the printing device, and the processed data can be stored in a memory in the printing device in a compressed form, and the data can be expanded into ink dot data while driving the ink of the printing head. Point forming element. In addition, the present invention can also be understood as a printing device and a printing method in addition to the printing system. the

In the present invention, when the ink dot data is developed, the result of judging whether the pixel of interest is formed or not is temporarily stored, and from the stored judgment results, it is possible to conclude the correctness for the application of at least one forward or backward movement. Based on the judgment result of ink dots formed dynamically, a line grid is formed. the

In this way, a wire grid can be formed quickly, so that an image can be printed quickly. the

Alternatively, in such a printing system, printing device, and printing method, after the pixel of interest is set, the data of the position corresponding to the pixel of interest can be expanded from the converted data stored in a state that needs to be expanded, It is judged whether or not the dots are formed. the

In this way, since only the image data at the position corresponding to the pixel of interest can be expanded, the image data will not be unnecessarily expanded. Therefore, the storage capacity required for this part of deployment can be saved. the

Furthermore, in a printing system, a printing device, and a printing method for printing an image while forming a grid of ink dots by repeating reciprocation and reciprocation on a printing medium while forming ink dots, it is possible to set the desired After the pixel of interest is selected, from the stored converted data, the data including the pixel of interest is expanded in units of the raster, and whether or not the ink dot is formed is determined. the

In this way, since the image data to be developed can be easily determined, not only the processing on the side of the printing apparatus can be simplified, but also the processing speed can be increased. the

In addition, in the present invention, the conversion of the image data may be realized by compressing dot data obtained by performing halftone processing on the original image data. the

At this time, a plurality of wire grids at a given interval are formed at once. When forming a plurality of grids, by detecting the pixels constituting the grid, and expanding the ink dot data including the pixels, then acquiring the ink dot data indicating whether ink dots are formed for the pixels, and according to the The ink dot data forms ink dots to print an image. the

In this way, since the ink dot data can be stored in a compressed state, there is no need for a large storage capacity. Therefore, when the printing system is constituted by the image processing device and the printing device, image processing can be efficiently shared between the image processing device and the printing device even if the processing capability of the printing device is not so strong. the

In addition, the printing system or printing device of the present invention can provide a plurality of summarized pixel groups for a plurality of pixels constituting an image, and calculate the number of ink dots formed in the pixel group according to the number of pixels in the image. Data determination, to obtain the converted data, and store the data of the number of ink dots as the converted data, and convert the data of the stored ink dots into the ink dot data, and In each of the pixel groups, for M groups of pixel groups (M is an integer greater than 2 and smaller than N, which is the number of groups of the pixel groups included in the pixel group), the pixel groups obtained by the conversion are converted at least once Ink dot data is stored at the same time. the

In the case of generating the dot data of all the pixels included in the pixel group at one time, the dot data of many pixels has to be stored for a long time because the grid is divided into multiple reciprocating motions to form, and it takes a long time. Large storage capacity. However, if only the ink dot data corresponding to the pixel group is stored in conjunction with the reciprocating movement of the nozzle, the number data must be converted into ink dot data every time the nozzle reciprocates, resulting in reduced conversion efficiency. In contrast, in the present invention, at least once in each pixel group, ink dot data of more than two pixel groups are generated and stored. In this way, as long as the ink dot data of all the pixel groups included in the pixel group is not stored, the temporarily required storage capacity can be controlled, and since the number of times of converting the number data into ink dot data for each pixel group can be reduced, It is also possible to control reduction in conversion efficiency. the

Of course, in the case of simultaneously storing ink dot data of a plurality of pixel groups, in addition to the pixel groups directly forming ink dots, the ink dot data of other pixel groups must be stored until the ink dots are formed. , so storage capacity is required. However, compared with the case of storing ink dot data of all pixel groups, it is still possible to control the required storage capacity. the

Furthermore, when storing the ink dot data of the pixel group, after converting the number data to generate the ink dot data of all the pixels included in the pixel group, only store the ink dot data for the pixels of the target pixel group, or only for The number data of the pixels of the target pixel group is converted into dot data and stored. the

In such a printing system, the converted ink dot data may be simultaneously stored at least for a plurality of pixel groups in which ink dots are continuously formed within the pixel group. the

The multiple groups of ink dot data stored at the same time, as long as they are the data of the pixel groups that continuously form ink dots in the pixel group, for example, even if it is not the pixel group that forms ink dots continuously, since the ink dot data is provided to the nozzle soon, it can be used. Controls the capacity required to store ink dot data. the

Alternatively, the dot data of the pixel group may be stored as follows as the plurality of sets of dot data stored at the same time. That is, the ink dot data contained in the pixel group can be provided to the nozzle pixel group by pixel group to form ink dots at the same time, and the ink dot data of the last multiple pixel groups (all remaining pixel groups in the pixel group at a certain moment), simultaneously stored. the

For the pixel groups that have not been converted into ink dot data, for example, if there are only two groups left, if the ink dot data of these pixel groups are stored, there is no need to store the number data of the pixel groups. That is, it is possible to store the ink dot data of the pixel group 2 with only a small storage capacity required for storing the number data. Based on this, it can be seen that if the ink dot data are converted and stored simultaneously for the plurality of groups of pixel groups in which ink dots are formed last in the pixel group, the increase in the capacity required for storing the ink dot data can be controlled. the

In the above printing system, after converting the number data, when calculating ink dot data according to the number of ink dots formed in a pixel group, the formation of ink dots can be determined according to the order of pixels forming ink dots in each pixel in the pixel group. Pixels of ink dots. the

The sorting of the pixels forming ink dots in the pixel group, that is, if the information of which pixel is the pixel forming ink dots in the pixel group is known, then it can be simply obtained according to the number of ink dots formed in the pixel group Ink point data. the

In addition, the printing device of the present invention may be understood as a program installed in a printing device using a computer to realize various functions of the printing device, or a storage medium storing the program, in addition to the printing method. the

Description of drawings

1A and 1B are explanatory diagrams showing the outline of the invention using a printing system. the

FIG. 2 is a conceptual explanatory diagram showing the configuration of a computer as an image processing device of the present embodiment. the

FIG. 3 is a conceptual explanatory diagram showing the structure of the printer of this embodiment. the

FIG. 4 is an explanatory view showing the arrangement of nozzles formed on the bottom surface of the ink ejection head. the

FIG. 5 is an explanatory diagram showing the mechanism of ejecting ink droplets from nozzles under the control of a control circuit. the

FIG. 6 is a flowchart showing the flow of image processing in this embodiment. the

FIG. 7 is an explanatory diagram showing one mode of expanding image data. the

Fig. 8 is an explanatory diagram showing another mode of developing image data. the

FIG. 9 is a conceptual explanatory diagram showing the content of cross printing processing. the

FIG. 10 is an explanatory diagram showing an outline of cross-print processing generally implemented as a reference. the

FIG. 11 is an explanatory diagram showing the outline of halftone and cross print processing in this embodiment. the

Fig. 12 is a conceptual explanatory view showing the principle of judging the presence or absence of ink dots by the dithering method. the

FIG. 13 is a flow chart showing the flow of halftone and cross printing processing in this embodiment. the

FIG. 14 is an explanatory diagram showing a printing system of a modified example. the

FIG. 15 is a flowchart showing the flow of processing for printing an image after generating control data (image printing processing) in this embodiment. the

16A and 16B are explanatory diagrams showing the state of resolution conversion performed in image printing processing. the

FIG. 17 is a flowchart showing the flow of count data generation processing. the

FIG. 18 is an explanatory diagram showing a part of a dither matrix. the

FIG. 19 is a conceptual explanatory diagram showing a state of determining whether or not a dot is formed in a pixel of interest by referring to a dither matrix. the

20A and 20B are conceptual explanatory diagrams showing how the number data is converted into ink dot data. the

FIG. 21 is a flow chart showing the flow of number data decoding processing in this embodiment. the

FIG. 22 is an explanatory view showing a state of printing an image by performing sub-scanning while forming a raster in a plurality of passes. the

FIG. 23 is an explanatory diagram showing an enlarged effective area of an image. the

FIG. 24 is a flowchart showing the flow of processing for generating ink dot data from the number data. the

25A to 25E are conceptual explanatory diagrams showing how ink dot data is generated from number data. the

26A and 26B are conceptual explanatory diagrams showing an example of memory capacity required for storing ink dot data generated by decoding number data when ink dots are formed while repeating main scanning of the ink ejection head. the

27A and 27B are conceptual explanatory diagrams showing another example of memory capacity required for storing ink dot data generated by decoding number data when ink dots are formed while repeating main scanning of the ink ejection head. the

Detailed ways

In order to more clearly describe the functions and effects of the present invention, the embodiments of the present invention will be described in the following order. the

A1. One of the outlines of the embodiments of the invention

A2. Outline 2 of Embodiments of the Invention

B. The structure of the device of the embodiment

C. Outline of image processing in the first embodiment

D. Halftone and cross-print processing

E. Variations

F. Outline of image processing in the second embodiment

G. Generation and processing of number data

H. Decoding processing of number data

A1. One of the outlines of the embodiment of the invention:

Hereinafter, the detailed description will be given based on the examples, but first, two forms of the embodiment of the invention will be briefly described for the sake of easy understanding. FIG. 1A is an explanatory diagram illustrating an embodiment of a printing system of the present invention. The illustrated printing system includes a computer 10A as an image processing device, a printer 20A as a printing device, and the like. To output an image from the computer 10A from the printer 20A, predetermined image processing must be performed on the image data, but in the present invention, this series of image processing is shared between the computer 10A and the printer 20A. the

In the computer 10A, an image is generally expressed as RGB image data of the three primary colors of light, and in the printer 20A, the image is printed using ink mounted on the printer. Therefore, when printing an image on a computer, it is necessary to perform a process of converting RGB image data into data corresponding to the amount of ink. In the printing system shown in FIG. 1 , image processing is performed by a color conversion module provided in a computer 10A. That is, the color conversion process is performed on the computer 10A side. The content of the color conversion processing will be described later. In addition, the computer 10A is further provided with an intermediate data transfer module, and the intermediate data after the image processing performed by the computer 10A side is transferred to the printer 20A from this module. When the intermediate data is transferred, in order to shorten the time required for the transfer, it is necessary to transfer it in a state expanded into a plurality of pixels from the printer 20A side. the

The intermediate data transferred to the side of the printer 20A is directly stored in the intermediate data storage module in the state to be expanded. On the side of the printer 20A, after the remaining image processing is performed on the data thus stored, the finally obtained data is supplied to the print head. The print head, based on the obtained data, forms dots of ink on the print medium to print an image. Here, since the intermediate data transferred from the computer 10A to the printer 20A is not in a format capable of expressing an image with ink dots, it is necessary to convert the intermediate data into data in this format. In addition, since the order in which the ink dots are formed by the print head is not limited to the order stored in the printer 20A, it is sometimes necessary to reorder the order of the data. In the printing system shown in FIG. 1, a halftone microweave module (halftone·microweave module) is provided in the printer 20A. After these processes are performed by this module, the finally obtained data is provided to the print head to print the image. the

As described above, the intermediate data is stored in a state that needs to be expanded into a plurality of pixels by the side of the printer 20A. Therefore, when the halftone and cross printing module performs the above processing, it reads the intermediate data including the pixel to be processed, expands it, and performs predetermined image processing on the pixel to be processed. When the transformation is completed for one pixel, the intermediate data including another pixel is read and expanded, and predetermined image processing is repeated for the target pixel. In this way, although the intermediate data to be processed is expanded in the printer 20A, since most of the intermediate data can be stored without being expanded, a large storage capacity is not required. As a result, even if image processing is shared between the computer 10A and the printer 20A, the storage capacity on the printer 20A side does not become a constraint, and the processing can be shared efficiently. the

A2. The second summary of the embodiment of the invention:

Next, an outline of another embodiment of the present invention will be described with reference to FIG. 1B . FIG. 1B is a schematic explanatory diagram illustrating a printing apparatus and a printing system of the present invention. This printing system is composed of a computer 10B as an image processing device, a printer 20B, etc., and operates by loading a predetermined program into the computer 10B. The computer 10B and printer 20B function as an integrated printing system as a whole. The printer 20B is equipped with a head 22B that ejects fine ink droplets, and when ink droplets are ejected from the head 22B onto the printing medium at an appropriate position on the printing medium, ink dots can be formed at arbitrary positions. With this function, the printer 20B ejects ink droplets while causing the head 22B to reciprocate on the printing medium, and prints an image by forming ink dots with an appropriate distribution on the printing medium. In this way, in order to print an image by forming ink dots, the printer 20B must perform predetermined image processing on the image to be printed and convert it into data indicating which pixel in the image to form ink dots. This image processing is usually performed by a computer 10B provided separately from the printer 20B, and an image is printed by supplying the obtained data from the computer 10B to the printer 20B. the

In this way, in a printing system in which the computer 10B performs image processing and supplies the obtained data to the printer 20B to print the image, if the number of pixels increases, the data of the image becomes larger, and it takes time to supply the data to the printer 20, making it difficult to quickly to print the image. Therefore, in the computer 10B of the printing system illustrated in FIG. 1B , each given plurality of pixels is grouped into one pixel group to determine the number of ink dots formed in the pixel group, and the obtained number data is provided to the printer. 20B. The ink dot number determination module 12B shown in FIG. 1B executes a process of determining the number of ink dots formed in a pixel group for each pixel group by performing predetermined image processing on an image to be printed. the

The box surrounded by dotted lines next to the ink dot number determining module 12B vividly shows how the module determines the number of ink dots formed in the pixel group. Here, a small rectangle shown inside a frame indicates a pixel, and a black dot displayed inside a pixel indicates that an ink dot is formed in the pixel. Pixels forming ink dots can be determined by applying a known image processing method such as error diffusion method or dithering method to image data. In the ink dot number determining module 12B illustrated in FIG. 1B , a total of 4 pixels in two vertical and horizontal columns are classified into pixel groups to determine the number of ink dots formed in the pixel groups. For example, the number of ink dots in each pixel group is determined as follows. For the pixel group located at the leftmost position in the frame surrounded by a dotted line, the number of ink dots formed in the pixel group is 1, from the left The number of ink dots formed in the second pixel group is 0, and the number of ink dots formed in the rightmost pixel group is 2. The number data output module 14B outputs the number of ink dots thus determined for each pixel group to the printer 20B as number data. Since the amount of data can be reduced by outputting the number of ink dots formed in a pixel group in this way compared to outputting the presence or absence of ink dots for each pixel, data can be quickly supplied to the printer 20B. the

In the printer 20B, after converting the number data obtained in this way into data indicating whether ink dots are formed in each pixel, an image is printed by driving the head 22B based on the obtained data. Here, in the printer 20B shown in FIG. 1B , the number data obtained from the computer 10B is not directly converted into data indicating whether ink dots are formed in each pixel, but is temporarily stored in the buffer memory 24B. Then, in conjunction with the action of the head 22B that reciprocates on the printing medium while forming ink dots, the number data is converted into data indicating whether or not ink dots are formed, and an image is printed by driving the head 22B with the obtained ink dot data. That is, use the ink dot data storage module 26B to convert the number data into ink dot data and store it, and provide it to the print head driving module 28B to drive the print head 22B by cooperating with the reciprocating motion of the print head 22B, and form ink dots at an appropriate position on the printing medium . The ink dot data storage module 26B is provided with a pixel group detection unit. Here, whenever the printhead 22B reciprocates, the pixel group which is a plurality of pixels forming ink dots is detected. The number data conversion unit converts the number data into ink dot data, and stores the ink dot data of each pixel included in the pixel group in the ink dot data memory. By supplying the ink dot data of the pixel groups thus stored to the head driving module 28B, an image is printed on the printing medium. the

Here, when storing the dot data in the memory, at least once for each pixel group, a plurality of pixel groups whose number is smaller than the pixel group included in the pixel group is converted into ink dot data and stored. In this way, the storage capacity of the dot data storage memory can be reduced compared to the case where all pixel groups included in the pixel group are converted into dot data. Of course, although the number data must be converted frequently compared with the case of converting all pixel groups into ink dot data, compared with the case of converting the number data into ink dot data every time the head 22B reciprocates, converting The frequency is still reduced. Therefore, while reducing the storage capacity of the memory required to be mounted on the printer 20B, images can be printed quickly. Hereinafter, such a printing system and printer will be described in detail based on embodiments. the

Hereinafter, such a printing system and a printer will be described in detail according to an embodiment. the

B. device structure in the embodiment:

FIG. 2 is an explanatory diagram showing the configuration of a computer 100 as the image processing apparatus of the present embodiment. The computer 100 is a well-known computer configured by connecting a CPU 102 as a center, a ROM 104 , a RAM 106 , and the like via a bus 116 . The computer 100 is connected with a disk controller DDC109 for reading data from a floppy disk 124 or an optical disk 126, a peripheral device interface P-I/F108 for exchanging data with peripheral devices, a video interface V-I/F112 for driving a CRT114, etc. . A hard disk 118, a color printer 200 described later, and the like are connected to the P-I/F 108 . In addition, if a digital camera 120 and a color scanner 122 are connected to the P-I/F 108, images read by the digital camera 120 and the color scanner 122 can also be printed. In addition, if the network interface card NIC110 is installed, the computer 100 can be connected to the communication line 300, and the data stored in the storage device 310 connected to the communication line can be read. the

FIG. 3 is an explanatory diagram showing a schematic configuration of the color printer 200 of the first embodiment. The color printer 200 is an inkjet printer capable of forming ink dots of four colors: cyan, magenta, yellow, and black. Of course, it is also possible to use an inkjet printer capable of forming ink dots of a total of six colors including cyan (light cyan) ink with low dye density and magenta (light magenta) ink with low dye density in addition to these four color inks. Furthermore, cyan ink, magenta ink, yellow ink, and black ink are referred to as C ink, M ink, Y ink, and K ink for short, respectively, depending on the circumstances. the

The color printer 200, as shown in the figure, includes: a mechanism that drives a print head 241 mounted on a carriage 240 to implement ink ejection and ink dot formation; A reciprocating mechanism; a mechanism for conveying the printing paper P by the paper feed motor 235; and a control circuit 260 for controlling ink dot formation, movement of the carriage 240, and conveyance of the printing paper. the

Mounted on the carriage 240 is an ink cartridge 242 storing K ink, and an ink cartridge 243 storing various inks of C ink, M ink, and Y ink. After the ink cartridges 242 and 243 are mounted on the carriage 240 , the respective inks in the ink cartridges are supplied to ink ejection heads 244 to 247 of respective colors provided below the print head 241 through inlet tubes (not shown). The ink ejection heads 244 to 247 for the respective colors eject ink droplets using the thus obtained ink to form ink dots on the printing medium. the

The control circuit 260 is centered on the CPU, and in addition to ROM, RAM, peripheral device interface P-I/F, etc., also includes a D/A converter 262 for converting digital data into an analog signal, and a device for temporarily storing data supplied to the print head 241. Drive cache 261 and so on. Of course, it is also possible to realize the same function through hardware or firmware without carrying a CPU. The control circuit 260 is in charge of controlling the main scanning operation and the sub scanning operation of the carriage 240 by controlling the operations of the carriage motor 230 and the feed motor 235 . In addition, the print head 241 is driven at an appropriate timing in accordance with the main scanning and sub-scanning of the carriage 240 . The print head 241 is driven by supplying a drive signal from the D/A converter 262 and supplying control data from the drive buffer 261 . The mechanism of ejecting ink droplets after supplying drive signals and control data will be described later using other drawings. In this way, under the control of the control circuit 260 , ink droplets are ejected at appropriate timing from the ink ejection heads 244 to 247 of the respective colors, thereby forming ink dots on the printing paper P and printing a color image. the

In addition, various methods can be applied to the method of ejecting ink droplets from the heads for ejecting the inks of the respective colors. That is, a method of ejecting ink from a piezoelectric element, a method of ejecting ink droplets by generating bubbles in the ink passage using a heater arranged in the ink passage, or the like can be used. In addition, instead of a printer that ejects ink, it is possible to use a method of forming ink dots on printing paper by utilizing phenomena such as thermal duplication, and a method of adhering toner powder of each color to a printing medium using static electricity. the

FIG. 4 shows a state in which a plurality of nozzles for ejecting ink droplets are formed on the bottom surfaces of the ink ejection heads 244 to 247 of the respective colors. As shown in the figure, on the bottom surface of the ink ejection head of each color, there are formed 4 groups of nozzle rows that eject the respective ink droplets of each color, and 48 nozzles Nz are arranged at intervals of nozzle pitch k in 1 group of nozzle rows. Jagged. These nozzles eject ink droplets simultaneously in accordance with drive signals and control data acquired from the control circuit 260 . This will be described with reference to FIG. 5 . the

FIG. 5 is an explanatory diagram showing the concept of ejecting ink droplets from the heads 244 to 247 for ink ejection according to drive signals and control data. As shown in FIG. 4 , a plurality of nozzles Nz are provided on the bottom surface of the ink ejection head, and each nozzle is connected to a specific area assigned to the drive buffer 261 . In addition, if the D/A converter 262 outputs the driving signal, it will supply the driving signal to all the nozzles together. the

The ink discharge heads 244 to 247 discharge ink droplets as follows. First, a nozzle that ejects ink droplets is selected, and data indicating the selection result is written into the drive buffer 261 . As described above, each of all the nozzles corresponds to a unique area provided on the drive buffer 261 . Then, when a nozzle to eject ink droplets is selected, data "1" is written in the area corresponding to the nozzle, and data "0" is written in the corresponding area when the nozzle is not selected on the contrary. Data is written in the drive buffer 261 in this way, and the data is output to the ink ejection heads 244 to 247 as control data. In addition, a drive signal is output from the D/A converter 262 in conjunction with output of control data from the drive buffer 261 . Although the output drive signal is supplied to all nozzles, only the nozzles selected by the control data are driven. Thus, ink droplets are simultaneously ejected from the nozzles selected to eject ink droplets and whose data in the drive buffer 261 is set to "1". the

The control circuit 260 shown in FIG. 3 sets control data for controlling ejection of ink droplets in the drive buffer 261 and continuously outputs drive signals in synchronization with the main scan and sub scan of the carriage 240 . In this way, ink droplets are formed at appropriate positions on the printing paper P, and an image is printed. the

C. Summary of image processing:

On the premise of the hardware of the embodiment described above, in this embodiment, the following image processing is performed. In this embodiment, the control data for controlling the ejection of ink droplets is generated by performing image processing on an image to be printed. FIG. 6 is a flowchart showing the flow of image processing performed by the printing system of this embodiment. In this embodiment, this processing is shared between the computer 100 and the printer 200 . Hereinafter, an outline of image processing will be briefly described with reference to FIG. 6 . This image processing corresponds to the embodiment shown in FIG. 1A. the

When image processing starts, first, image data of an image to be printed is read (step S100). The data read here is RGB color image data, that is, image data with 256 grayscales ranging from grayscale value 0 to grayscale value 255 for each color of R, G, and B. the

Then, color conversion processing is performed on the read image data (step S102). The color conversion process is a process of converting RGB color image data expressed by a combination of gradation values of R, G, and B into image data expressed by a combination of gradation values of each color used for printing. As mentioned above, the printer 20 prints an image using the four color inks of C, M, Y, and K. Therefore, in the color conversion processing of this embodiment, processing is performed to convert image data represented by RGB colors into image data represented by grayscale values of C, M, Y, and K colors. Color conversion processing is performed by referring to a three-dimensional numerical table called a color conversion table (LUT). Since the gradation values of the C, M, Y, and K colors obtained by color conversion for the GRB color image data are stored in the LUT in advance, color conversion can be quickly performed by referring to the LUT for conversion. Here, RGB image data with 256 grayscales is converted into CMY grayscale data with the same 256 grayscales. the

After the color conversion process is completed, the process of transferring the obtained intermediate data to the color printer 200 starts (step S104). In this embodiment, in order to shorten the time required for transfer, the computer 100 transfers the intermediate data in a state where it needs to be developed by the color printer 200 . Here, the meaning of "the state in which development is required" will be described. the

In the printing system of this embodiment, the printing resolution at which the color printer 200 forms ink dots on the printing medium is set to a value higher than the resolution of the image used by the computer 100 . FIG. 7 is an explanatory diagram illustrating its state, showing that the resolution of image data in the computer 100 is 720 dpi (720 pixels per inch), and the print resolution in the color printer 200 is set to 1440 dpi (per 1 inch). inch 1440 pixels). When converting the resolution to 1440dpi, each pixel of 720dpi is divided into 2 horizontally and vertically to generate 4 pixels per pixel. the

The lower part of FIG. 7 schematically shows the state where the pixel 1 is divided into four in this way. That is, the pixel a with a resolution of 720 dpi is divided into four pixels of pixels a1, a2, a3, and a4 after converting the resolution to 1440 dpi. Similarly, pixel b with a resolution of 720dpi is divided into four pixels b1, b2, b3, and b4 after the resolution is converted to 1440dpi. Furthermore, in this embodiment, the image data of each pixel having a resolution of 1440 dpi after being divided in this way is the same as the image data of pixels having a resolution of 720 dpi before division. Of course, instead of simply dividing the same image data, an interpolation operation may be performed between adjacent pixels. the

Referring to FIG. 7 as an example, let the image data of the pixel a1 and the pixel b1 have the same values as the image data of the pixel a and the pixel b before division, respectively. In addition, the image data of the pixel a2 is obtained through an interpolation operation based on the image data of the pixel a and the pixel b. The image data of the pixel a3 is obtained by interpolating the image data of the pixel a and the image data of the pixels below the pixel. In addition, the image data of the pixel a4 is obtained by performing an interpolation operation with the pixel located on the lower right of the pixel a. the

Alternatively, the above two methods, that is, the method of simply dividing the same image data and the method of performing interpolation calculations, can be used separately according to the amount of change in image data between adjacent pixels (for example, between pixel a and pixel b). . For example, simple division can be performed when the absolute value of the amount of change is greater than a predetermined value, and interpolation can be performed when the absolute value is less than or equal to a predetermined value. The part where the absolute value of the amount of change takes a larger value can be regarded as the part corresponding to the edge in the image, so if it is simply divided instead of interpolated, the edge bluntness can be avoided. On the contrary, if the interpolation operation is performed on the part where the absolute value of the change amount between pixels is small, the gradation of the image data can be smoothed, and a natural-looking image can be obtained. the

One aspect of the "state requiring expansion" means the state before the low-resolution image data is converted into the high-resolution image data, in other words, the state before the pixels are divided, as described above. In addition, in the above-mentioned description, although the high resolution was set as the resolution which was 2 times that of the low resolution, it is not limited to this. For example, the high resolution may be a non-integer multiple of the low resolution. the

In addition, the "state in which expansion is required" also includes a state in which image data is compressed as described below. FIG. 8 shows a case where an image is compressed by so-called RLE (run length) as an example of this form. RLE compression is a method of compressing the same and continuous parts of the data with continuous numbers and numerical representations of continuous data. the

As an example, a case where RLE compression is performed on the data shown in FIG. 8( a ) will be described. The illustrated data consists of 15 numerical values, but among them, the same numerical value "21" is consecutive from the third numerical value to the seventh numerical value. In addition, here, each numerical value is represented by 1 byte. In RLE compression, this part of the data is replaced with data consisting of a compression flag indicating that it has been compressed, a continuous number (here, 5), and a continuous numerical value (here, a numerical value of 21). On the other hand, data that is not a continuous portion of the same value is not subjected to such compression, and a compression flag indicating non-compression is added before each data. the

Fig. 8(b) summarizes such conversion rules when RLE compression is performed. According to this rule, after the data RLE in Figure 8(a) is compressed, the data shown in Figure 8(c) is obtained. Because the first and second values of the original data shown in Figure 8(a) are different "12" and "15", this part is not compressed, and a 1-digit number is added before each value. Compression flag. The compression flag is set to "0" when no compression is performed. In addition, since the 3rd to 7th values of the original data are continuous, after this part is compressed, it is transformed into "5" representing the continuous number and "21" representing the data value. Furthermore, when performing compression, the compression flag is set to "1". Through transformation in this way, the part of the original data that takes 5 bytes is compressed into data with 1 bit of compression flag + 2 bytes. In FIG. 8( c ), the compression flags set to "0" are indicated by blanks, and the compression flags set to "1" are indicated by black solids. Therefore, by performing the above various transformations on the data shown in FIG. 8( a ), it is possible to compress 15-byte data into 12-byte data. On the contrary, when the compressed data shown in Fig. 8(c) is transferred, the data is expanded to the data shown in Fig. 8(a) and used. the

The aspect of "a state requiring expansion" includes a state in which image data is compressed as described above. Furthermore, a form obtained by combining these forms, that is, a form compressed while maintaining a low resolution is also included. In addition, although the case of RLE compression has been described above as an example, other known methods may be used for compression. the

In step S104 of FIG. 6, processing is performed to transfer the image data after the color conversion processing to the color printer 200 in the state in which it needs to be expanded as described above. the

In the color printer 200, the transferred intermediate data is directly stored in a state to be expanded, and halftone and cross printing processing is performed on the data (step S106). It is roughly processed as follows. Although the intermediate data transferred from the computer 100 has been subjected to color conversion processing and converted into grayscale data corresponding to the amount of ink, it is still data having 256 grayscales. In contrast, in the color printer 200, only one of the states of "formation" and "non-formation" of ink dots can be obtained. Therefore, it is necessary to convert the gradation data having 256 gradations into data expressed by whether or not ink dots are formed. This kind of processing is usually called half tone (half toning) processing. Various methods such as error diffusion and dithering are known as methods for performing halftone processing. the

In addition, for the reason described later, the ink ejection head does not form ink dots in the order of the arrangement of pixels, so it is necessary to perform processing to rearrange the data for judging whether or not ink dots are formed so that the ink ejection head actually forms ink. order of points. Here, this processing is called cross printing (microweave). In the halftone and cross print processing shown in step S106 of FIG. 6 , halftone processing and cross print processing are integrally performed. The details of the halftone and cross-print processing will be described later, but here, the cross-print processing will be supplemented. the

As described with reference to FIG. 4 , the nozzles Nz provided on the bottom surfaces of the ink ejection heads 244 to 247 are formed at intervals of a nozzle pitch k from each other. For this reason, in the case of the main scanning of the print head, if each nozzle ejects ink droplets at the same time to form a plurality of grids, gaps will be formed between the grids. For this purpose, a given amount of sub-scanning is performed, and the gap is filled and printed. FIG. 9 shows a conceptual explanatory diagram of such a form. the

FIG. 9 shows a situation where ink ejection nozzles are sub-scanned to fill gaps in rasters. The left side of the figure shows the sub-scanning position of the nozzles, and the right side shows the raster formation according to the position of the nozzles. Here, although the actual sub-scanning is implemented by moving the printing paper relative to the nozzle, for the convenience of description, the following description will be made by fixing the printing paper and moving the nozzle. Furthermore, as described above with reference to FIG. 4 , although four ink ejection heads 244 to 247 are mounted side by side on the print head, only one head is shown in FIG. 9 for simplification of illustration. In addition, 48 nozzles are provided at intervals of nozzle pitch k on the bottom surface of the ink ejection head, but here, four nozzles Nz are provided at intervals of nozzle pitch 3 for simplification of illustration. the

First, the head is positioned at the topmost position in FIG. 9 , and after main scanning is performed while ejecting ink droplets from the nozzles Nz, four wire grids corresponding to the number of nozzles Nz are formed. These wire grids are four wire grids denoted by No. 1 in the figure and indicated by solid lines. Here, since the nozzles are arranged at intervals of 3 nozzle pitches, there is a gap corresponding to the nozzle pitch between the wire grids. Therefore, in order to form a wire grid in this gap, as shown by the arrow in the figure, let the shower head sub-scan 4 wire grids. The rectangle shown by the dotted line in FIG. 9 represents the position of the shower head at this time. By ejecting ink droplets while performing main scanning at this head position, four wire grids marked with No. 2 and indicated by dotted lines are formed. As shown in FIG. 9 , although the grids indicated by broken lines are formed between the grids of solid lines, gaps still remain between the grids. Therefore, make the printhead sub-scan again. The rectangle indicated by the dotted line in FIG. 9 shows the position of the head during such sub-scanning. In addition, the wire grid formed at the nozzle position is marked with No. 3 and indicated by a dotted line. As shown in FIG. 9, after the dot-dashed wire grid is formed, a wire grid without gaps is formed. the

As described above, since the interval between the nozzles is the nozzle pitch k (3 in the example of FIG. 9 ), in the grids formed by each main scan, a gap corresponding to the nozzle pitch is generated between the grids. However, by sub-scanning the shower head by an appropriate amount, the line grid can be formed by continuous k-1 times of sub-scanning to fill the gap. Filling up the gaps between the wire grids by such sub-scanning to form a wire grid without gaps is called "interlace scanning". In order to implement interlaced scanning, when the number of nozzles arranged on the ink ejection nozzle is N, and the nozzle pitch is k, the value is selected so that N and k do not have a common divisor other than 1 (called this relationship between N and k) are "mutually prime numbers"), and an amount of sub-scanning equivalent to the number of N rasters corresponding to the number of nozzles is performed. When performing interlaced scanning in this way, the ink ejection head forms ink dots in an order different from the arrangement of pixels to form a line grid. the

In addition, in the example shown in FIG. 9 , each wire grid has been described to be formed by one main scan, but one wire grid may be formed by dividing into a plurality of main scans. For example, the ink dots of the odd-numbered pixels and the ink dots of the even-numbered pixels may be formed using different main scans. In this way, image quality can be stabilized. In Fig. 9, the sub-scanning of 4 rasters is described, and if the sub-scanning of 2 rasters is performed, since the nozzles will pass through the position of each raster twice, the first main scan can form, for example, the ink of the odd-numbered pixels. Dots, the second main scan forms the ink dots of the even-numbered pixels. Forming each line grid by dividing it into multiple main scans is called "overlap". When overlapping is performed, the ink ejection head also forms ink dots in an order different from the arrangement of pixels. the

Furthermore, in order to increase the printing speed, ink dots are sometimes formed not only when the nozzle moves forward, but also when it moves back. In this way, ink dots are formed at the time of forward movement and return movement, which is called "two-way printing". When performing bidirectional printing, the ink ejection head can also form ink dots in an order different from the arrangement of pixels. the

The cross printing process is a process of rearranging the data after the halftone process into the order of ink dots formed by the ink ejection heads according to the implementation status of so-called interlaced scanning, overlapping, and bidirectional printing. In the halftone and cross print processing of this embodiment shown in step S106 of FIG. 6 , the halftone process and the cross print process are integrally implemented as will be described later. the

After performing the halftone and cross-print processing, the obtained data is output to the drive buffer 261, and provided to the print head 241 from the drive buffer 261 in conjunction with the movement of the carriage 240 (step S108 in FIG. 6 ). In this way, ink droplets are collectively ejected from the nozzles by the mechanism described with reference to FIG. 5, and an image is printed on the printing paper. the

As described above, in the printing system of the present embodiment, the color printer 200 directly stores the intermediate data transferred in the state where expansion is required. Then, since halftone and cross print processing described later is performed on the data, image processing performed on the color printer 200 side does not require a large storage capacity. Therefore, even if the memory capacity installed in the color printer 200 is small, it is not limited by it, and image processing can be efficiently distributed among the computer 100 . The reason for this will be described below. the

D. Halftone and cross-print processing:

Next, the halftone and cross-print processing of the present embodiment will be described in detail, but prior to this, a general cross-print processing will be described as a reference for ease of understanding. the

As a reference example, FIG. 10 shows a state where cross-print processing is performed on halftone-processed image data. In this embodiment, although halftone processing and cross print processing are integrated for the intermediate data stored in the state that needs to be expanded, but as a reference, in the common cross print processing shown in FIG. The processed image data is processed. the

After the halftone processing is performed, the image data converted into the expression of whether or not ink dots are formed for each pixel is stored in the RAM in the printer. From the image data, select the appropriate data according to the order in which the ink dots are formed by the nozzles, and transfer them to the drive buffer. The data transferred to the drive buffer is provided to each nozzle as control data at an appropriate timing after being synchronized with the main scan and sub scan of the head. As described with reference to FIG. 5 , an image is printed by collectively ejecting ink droplets from the nozzles according to the control data. Furthermore, in order to simplify the description, only interlaced scanning is implemented below, and overlapping and bidirectional printing are not implemented. the

In the example shown in FIG. 10 , since the four nozzles on the print head are arranged at intervals of a nozzle pitch of 3, after the main scan of the print head ejects ink droplets simultaneously, four grids are simultaneously formed at a distance of 2 grids from each other. Correspondingly, during the main scanning of the print head, from the image data stored in the RAM, the image data corresponding to 4 grids that are 2 grids away from each other are selected, and output to the drive buffer. For example, in FIG. 10 , when the print head is in the main scan at position A, it is necessary to select the data corresponding to the 4 line rasters indicated by oblique lines in the image data and provide them to the drive buffer. In other words, until these data are supplied to the driver cache, at least the image data of the area a including the hatched data needs to be stored in the RAM of the printer. Similarly, when the head is in the main scan at the B position, the image data of the minimum area b needs to be stored in the RAM until the data on the RAM equivalent to the line grid is output to the drive buffer. the

Although in FIG. 10 , in order to simplify the illustration, four nozzles are provided on the ink ejection head at intervals of a nozzle pitch of 3, but in reality, the number of nozzles is far more than this, and the nozzle pitch k is The value also takes a value larger than 3. Therefore, at least during the period when the image data is output to the drive cache, the amount of data that has to be stored in the RAM will be very large. Since the storage capacity installed on the printer side is basically less than that installed on the computer, since such a large storage capacity is required on the printer side, even if the image processing is shared between the computer and the printer, for example, it will be limited due to storage capacity constraints. cannot be shared efficiently. In the halftone and cross print processing of the present embodiment described below, since the printer does not require a large memory capacity, this problem does not occur, and the image processing can be efficiently shared. the

FIG. 11 is an explanatory diagram showing the outline of halftone and cross print processing in this embodiment. Also in the halftone and cross printing process, the raster data formed by the nozzles during the main scanning is stored in the drive buffer 261, and then output from the drive buffer 261 to the nozzles of the ink ejection heads as control data. The halftone and cross-print processing is implemented by the halftone and cross-print module in the control circuit 260 of the color printer 200 . In this module, first, a pixel whose data is to be transferred to the drive buffer 261 is set as a pixel of interest. Then, from the intermediate data stored in the RAM in the state that needs to be expanded, the corresponding data is read and expanded, and whether the pixel of interest in the expanded data has formed ink dots is judged. Furthermore, in Figure 11, it is assumed that the image data transferred with a resolution of 720dpi is expanded into image data with a resolution of 1440dpi and then printed. When the 1-pixel image data is expanded to 4-pixel image data. In addition, among the expanded pixels of 4 pixels shown in the block, a pixel marked with a circle mark indicates that the pixel is a pixel of interest. the

Whether or not ink dots are formed can be determined using, for example, a method called a dithering method. The dithering method, as shown in FIG. 12 , is to compare the image data of the focused pixel with the threshold value set at the corresponding position in the dithering matrix. If the image data is larger, it is judged that ink dots are formed in the pixel. If the image data If one is smaller, it is judged that a dot is not formed in the pixel. If this method is used to determine whether or not ink dots are formed, it is possible to determine whether or not ink dots are formed immediately after the image data including the pixel of interest is developed. the

After judging whether or not ink dots are formed on the focused pixel, the judging result is stored in the drive buffer 261 . After the processing for one pixel of interest is completed in this way, a new pixel is set as the pixel of interest, the same processing is performed, and the result of judging whether or not ink dots are formed is stored in the drive buffer 261 . After repeating this process, all the data of the line grid formed in one main scan of the head is stored in the drive buffer 261, the carriage 240 executes the main scan, and at the same time outputs the control data from the drive buffer 261 to the head for ink ejection to eject ink droplets. . the

In the above-mentioned halftone and cross-print processing, it is also necessary to store image data including rasters formed by at least one main scan on the RAM. However, since in the halftone and cross print processing of this embodiment, the data of the pixel in question is read out and developed, and then the halftone and cross print processes are performed integrally, therefore, it is possible to perform the halftone and cross print processing on the RAM as needed. Store image data. Therefore, even if the color printer 200 does not have a large storage capacity, halftone and cross print processing can be efficiently performed. the

FIG. 13 is a flowchart showing the flow of the above-mentioned halftone and cross printing process. This processing is carried out by the control circuit 260 of the color printer 200 . Next, the specific content of the processing will be described according to the flowchart. the

After starting the process, the control circuit 260 first requests the computer 100 to transfer a certain amount of intermediate data (step S200). In this embodiment, as described with reference to FIG. 6 , after image processing up to color conversion is performed on the computer 100 side, the image data after the color conversion processing is transferred from the computer 100 in a state requiring development. Therefore, in step S200, the transferred intermediate data is directly stored in the RAM in a state to be expanded. When storing in RAM, the transferred intermediate data can be directly stored in its original state, or can be stored after some preprocessing. the

Then, the pixel of interest is set (step S202). The focused pixel referred to here refers to the focused pixel for determining whether or not ink dots are formed and then writing the determination result into the drive buffer 261 . The color printer 200 performs printing by appropriately combining interlaced scanning, overlapping, bidirectional printing, etc. according to image printing conditions, and changes the order in which ink dots are formed by each nozzle Nz provided in the ink ejecting head according to the printing conditions. In step S202 , the focus pixel is set in consideration of the order in which ink dots are formed by the nozzles Nz according to the printing conditions. the

After the pixel of interest is set, the intermediate data including the pixel of interest is read and expanded (step S204). When reading the intermediate data, the entire line grid including the pixel of interest can be read out, or only the part of the pixel of interest can be read out. the

For example, when the upper left corner of the image to be printed is assumed to be the origin, the pixel of interest is assumed to be the pixel at the Nth row and the Mth column. For example, when the intermediate data transferred from the computer 100 is compressed by RLE, the intermediate data of the Nth row can be directly read and expanded, or the intermediate data of the Nth row can be analyzed to read out only the part including the pixels of the Mth column. Or, if printing is performed after converting the intermediate data with a resolution of 720dpi to a resolution of 1440dpi, the entire raster of row {int(N/4)+1} can be read from the intermediate data, or in In the intermediate data, the data of the pixel at row {int(N/4)+1} and column {int(M/4)+1} is read out. Here, int(N) means an operator that rounds off the fractional part of N and takes only the integer part. In this way, processing is performed in step S204 to expand the transferred and stored intermediate data to the level of pixels that are actually printed by the color printer 200 . the

Then, according to the expanded data, it is judged whether or not ink dots are formed in the pixel of interest (step S206). Here, whether or not ink dots are formed is judged by applying a so-called dither method. That is, the image data in the pixel of interest in the expanded data is compared with the threshold value set at the position corresponding to the pixel of interest in the dither matrix, and if the image data is larger, it is determined that an ink dot is formed on the pixel of interest. Otherwise, it is judged that ink dots are not formed. the

After judging whether or not ink dots are formed on the focused pixel in this way, processing is performed, and the judging result is written into the corresponding position of the drive buffer 261 (step S208 ). As explained with FIG. 5, in the drive buffer 261, a dedicated area is assigned to each head. Therefore, the determination result of whether or not ink dots are formed is stored in the area assigned to the hypothetical nozzle when focusing on the pixel setting. the

After the processing of one pixel of interest is completed in this way, it is judged whether all the data of one process, that is, the data representing the judgment results of all pixels formed by the carriage 240 during one main scan, are stored in the drive buffer 261 (step S210). Then, if all the data of one process has not been stored (step S210: No), return to step S202 to set a new pixel of interest, and repeat a series of processes. the

After repeating these various processes, soon after it is judged that all the data of one course are stored (step S210: YES), the stored data is output to the ink ejection head as control data as explained in FIG. 6 . Then, it is judged whether the printing is finished (step S212 ), and if not finished (step S216 : No), return to step S200 and request new intermediate data to the computer 100 . In addition, if it is determined that the printing is finished (step S216: Yes), the halftone and cross printing process shown in FIG. 13 is ended, and the image processing subroutine shown in FIG. 6 is returned. the

In the image processing of FIG. 6 , after returning from the halftone and cross printing processing, the data stored in the drive buffer 261 is output as control data in conjunction with the movement of the carriage 240 . Thus, an image is printed out on the printing medium. the

As described above, in the image processing of this embodiment, the intermediate data acquired from the computer 100 in a state requiring expansion is stored as it is. Then, whether or not ink dots are formed is judged every time the intermediate data including the pixel of interest is read, and the judgment result is stored in the drive buffer 261 . Therefore, even if the color printer 200 does not have a large storage capacity, halftone processing and cross printing processing can be performed. Therefore, when the image processing is distributed between the computer 100 and the color printer 200 , the processing can be efficiently distributed without being constrained by insufficient memory capacity mounted on the printer 200 side. the

E. Variation:

In the above-described embodiment, the computer 100 performs up to the color conversion process, and the printer 200 performs halftone processing and thereafter, but the allocation of image processing is not limited to this method. FIG. 14 shows a conceptual explanatory diagram of an example of such a modification. the

In the modified example shown in FIG. 14 , color conversion processing and halftone processing are performed on the computer 100 side. Halftone processing is not limited to the dithering method described above, and various methods can be applied. In particular, when a method such as the error diffusion method, which can obtain high image quality but requires high processing power, is used, since the processing power of the general computer 100 is higher than that of the color printer 200, the processing can be performed quickly. In this way, after halftone processing, compression processing such as RLE compression is performed on the image data, and the image data is transferred to the color printer 200 . the

The color printer 200 stores the transferred intermediate data as it needs to be expanded, and performs cross print processing on the intermediate data. That is, a pixel of interest is set, and intermediate data including the pixel of interest is developed. The pixel-wise data is then stored in the driver cache. In this modified example, since the color printer 200 is not required to have a large storage capacity, it is possible to efficiently share image processing with the computer 100 . the

In addition, a software program (application program) that realizes the above-mentioned functions may be provided to the main memory of the computer system and an external storage device through a communication line to be executed. Of course, software programs stored in CD-ROM or floppy disks can also be read and run. the

Furthermore, although in the above-mentioned various embodiments, the case where the size of ink dots formed on printing paper is constant has been described, it is also applicable to so-called variable ink dot printers and the like, which are formed on printing paper. The size of the ink dots formed on the printer can be controlled. the

In addition, in each of the above-mentioned embodiments, although the case where the image data conversion process is implemented in a computer has been described, part or all of the image data conversion process can also be performed on the printer side or by a dedicated image processing device. implement. the

F. Summary of image processing in the second embodiment:

Next, a second embodiment of the present invention will be described. The structure of the printing system of the second embodiment corresponds to the embodiment shown in FIG. 1B, and its hardware structure is the same as that of the first embodiment. In this embodiment, the control data used to control the ejection of ink droplets is generated by performing predetermined image processing on an image to be printed. 15 is a flowchart showing the flow of processing for printing an image after generating control data (image printing processing) in the present invention. As will be described later, in the image printing process of this embodiment, the first half of the processing is implemented by the function of the CPU built in the computer 100 , and the second half of the processing is implemented by the function of the CPU built in the control circuit 260 of the printer 200 . Next, an outline of image printing processing will be described with reference to FIG. 15 . the

After the computer 100 starts the image printing process, it first starts to read the image data to be converted (step S1000), and then executes the color conversion process (S1020). Since the reading processing and color conversion processing of these image data are the same as those in the first embodiment, detailed description thereof will be omitted. the

After the color conversion process ends, the resolution conversion process starts next (step S1040). The resolution conversion process is a process of converting the resolution of image data into a resolution (print resolution) for printing by the printer 200 . Generally speaking, in order to improve the print quality, it is more effective to reduce the pixel size and print at a higher resolution. However, in order to increase the printing resolution, it is not necessary to increase the resolution of the original image data. The reason for this is that when printing an image by forming ink dots, there are only two types of whether ink dots are formed or not formed in each pixel. Of course, in the printer, by changing the size of the ink dots, or changing the density of the ink used to form the ink dots, even the ink dots alone can express more states. However, in such a printer, the number of gradations that can be represented by one pixel is only a limited number of gradations. In contrast, even if the image data read in has only 1 byte of data, each pixel can represent 256 gray levels. In this way, since there is a large difference in the gradation that can be expressed by each pixel, the print quality can be improved only by setting the print resolution to be higher than the resolution of the read image data. For this reason, in step S1040 of FIG. 15 , processing is performed to convert the resolution of the image data to a higher resolution printing resolution. the

16A and 16B show the state of resolution conversion performed in the first embodiment. In addition, although image data of C, M, Y, and K colors are obtained by color conversion as described above, the processing described below is similarly performed on image data of each color. Therefore, in order to simplify the description, the following description will be made without designating a color. the

FIG. 16A schematically shows an enlarged part of the color-converted image data. The multiple rectangles shown in FIG. 16A schematically represent pixels respectively, and the numerical values represented in the rectangles represent grayscale values assigned to each pixel. As shown in the figure, image data is data in which gradation values are assigned to individual pixels arranged in a grid. In order to convert the resolution of this image data to a higher resolution, new pixels can be generated by performing interpolation operations between pixels, and in this embodiment, as the simplest method, by dividing pixels into smaller pixels for resolution conversion. the

Fig. 16B shows a case where resolution is converted by dividing pixels. In the illustrated example, one pixel is divided into eight pixels by dividing each pixel into four in the main scanning direction (left-right direction in the figure) and in two in the sub-scanning direction (vertical direction in the figure). The dotted line shown in FIG. 16B shows the case where the pixels are divided. The small pixels thus generated are assigned the same gradation value as the gradation value of the original pixel before division. By performing the above processing, the resolution of the image data is converted to 4 times the resolution in the main scanning direction and 2 times the resolution in the sub scanning direction. Of course, the increase ratio of the resolution can be set to various ratios as required. the

As described above, after the resolution of the image data is converted into the print resolution, the computer 100 starts count data generation processing (FIG. 15, step S1060). The number data generation process refers to the following process. The image data after color conversion is gradation data in which gradation values are assigned to individual pixels. In contrast to this, the printer 200 prints an image by forming ink dots in pixels so that ink dots are formed at an appropriate density corresponding to the gradation value of the image data. Therefore, the gradation data must be transferred to the printer 200 after being converted into data indicating whether ink dots are formed in each pixel. Also, since the data indicating whether or not ink dots are formed is transferred to the printer 200 in units of pixels, the time required for transfer becomes longer as the number of pixels increases, making it difficult to quickly print an image. Therefore, in the image printing process of this embodiment, a predetermined number of pixels are grouped into pixel groups, and data on the number of ink dots formed in the pixel group is transferred to the printer 200 . Here, the data on the number of ink dots formed in a pixel group can be obtained by converting the image data into data indicating whether or not ink dots are formed in each pixel in advance, and then grouping a plurality of pixels into a pixel group. Alternatively, the number of ink dots formed in each pixel within a pixel group may be determined after a plurality of pixels are initially grouped into a pixel group. In the count data generating process of step S1060 , processing is performed to generate data (count data) on the number of ink dots thus formed in the pixel group, and transfer the obtained count data to the printer 20 . The details of the number data generation process will be described later. the

The CPU built in the control circuit 260 of the printer 200 receives the number data output from the computer 100, and starts the number data decoding process (step S1080). The count data decoding process is as follows. As described above, the printer 200 prints an image based on data indicating whether ink dots are formed in each pixel. However, the computer 100 of this embodiment outputs number data indicating the number of ink dots to be formed in a pixel group instead of data indicating whether or not ink dots are formed in each pixel. Therefore, it is first necessary to perform processing to convert the number data into data indicating whether or not ink dots are formed in each pixel. In this specification, data indicating whether or not a dot is formed in each pixel is referred to as dot data. The method of converting the number data into ink dot data will be described later. Then, by outputting the obtained ink dot data from the drive buffer 261 as control data in accordance with the main scanning movement of the ink ejection heads 244 to 247, ink droplets are ejected on the printing medium to print an image. The so-called number data decoding process is a process of obtaining ink dot data based on the number data, and outputting it from the drive buffer 261 as control data in conjunction with the main scanning of the ink ejection heads 244-247. The details will be described later. In the number data decoding process of this embodiment, instead of converting the number data of each pixel group once and then storing all the ink dot data, it is considered that the reciprocating motion of the nozzle is divided into Multiple times to convert the number data, and store the ink dot data. Therefore, it is possible to control the memory capacity of the printer 200, and at the same time, quickly convert the number data into ink dot data, and quickly print the image. the

For the convenience of explanation, the number data generation process will be described first below, and then the content of the number data decoding process in this embodiment and the reason why the memory capacity to be mounted on the printer 200 can be reduced by implementing the number data decoding process will be described. illustrate. the

G: Quantity data generation processing:

FIG. 17 is a flowchart showing the flow of count data generation processing. Hereinafter, the number data generation process will be briefly described according to the flowchart. the

After starting the number data generation process, first, a plurality of predetermined pixels are combined to generate a pixel group (step S2000). Here, in the resolution conversion process, after one pixel is divided into 8 pixels, the 8 pixels obtained by dividing the same pixel are grouped into a pixel group. For example, if we focus on the pixel in the upper left corner of Figure 16A, as shown in the upper left corner of Figure 16B, after the pixel is divided into 8 pixels with 2 vertical rows and 4 horizontal columns, in step S2000, these 8 pixels are summarized Generate pixel clusters. Furthermore, the pixels to be classified as a pixel group are not necessarily pixels that must be adjacent to each other, as long as they have a given positional relationship, no matter what kind of pixels can be classified into a pixel group. the

In addition, when the pixels divided from the same pixel are grouped into pixel groups in this way, the resolution conversion processing in FIG. 15 can also be omitted. In this case, in the following description, it is possible to perform basically the same processing by appropriately replacing the "pixel group" with some part. the

Next, among the pixels classified into the pixel group, one pixel of interest (pixel of interest) is set to determine whether ink dots are formed (step S2020 ). Then, by comparing the gradation value assigned to the pixel of interest with the threshold value of the dither matrix, it is judged whether or not ink dots are formed for the pixel of interest (step S2040). Here, the so-called dithering matrix is a two-dimensional numerical table that stores a plurality of threshold values in a lattice form. The process of judging whether or not ink dots are formed using the dither matrix will be described with reference to FIGS. 18 and 19 . the

FIG. 18 is an explanatory diagram showing a part of a dither matrix as an example. In the illustrated matrix, 64 pixels in the horizontal and vertical directions, a total of 4096 pixels, randomly store threshold values selected from the range of gradation values 0 to 255 without omission. Here, the grayscale value of the threshold value is selected from the range of 0-255, because the image data in this embodiment is 1-byte data, and the grayscale value assigned to the pixel corresponds to a value of 0-255. Furthermore, the size of the dithering matrix is not limited to 64 pixels horizontally and vertically as shown in FIG. 18 , and may include various sizes with different pixels horizontally and vertically. the

FIG. 19 is an explanatory diagram showing a state of judging whether or not ink dots are formed for a pixel of interest with reference to a dither matrix. When judging whether or not ink dots are formed, first, the grayscale value of the pixel of interest is compared with the threshold value stored in the corresponding position in the dither matrix. The thin dotted arrows shown in the figure schematically represent the comparison between the gray value of the pixel of interest and the threshold value stored in the corresponding position in the dithering matrix. Then, when the gradation value of the pixel of interest is greater than the threshold value of the dither matrix, it is determined that an ink dot is formed in the pixel. On the contrary, when the threshold value of the dither matrix is large, it is determined that ink dots are not formed in the pixel. Specifically, in FIG. 19 , for the pixel at the upper left corner of the image data, the grayscale value of the pixel data is 97, and the threshold value of the dithering matrix is 1. That is, when the gradation value of the image data is larger than the threshold value, it is determined that ink dots are formed in the pixel. The arrow indicated by the solid line in FIG. 19 schematically shows a situation where it is determined that an ink dot is formed in the pixel and the result of the determination is written into the memory. On the other hand, since the grayscale value of the image data is 97 for the pixel next to the right side of the pixel, the threshold value of the dither matrix is 177, and the threshold value is larger, so it is judged that ink dots are not formed for this pixel . In step S2040 of FIG. 17 , processing is performed with reference to the dither matrix in this way, and it is judged whether or not ink dots are formed in the pixel of interest. the

Then, it is judged whether the above-mentioned processing has been performed on all pixels in the pixel group (step S2060), and if there are unprocessed pixels in the pixel group (step S2060: No), return to step S2020 to implement a series of processing. In this way, after the judgment of whether ink dots are formed in all the pixels in the pixel group is completed (step S2060: Yes), the number of ink dots formed in the pixel group is detected, and stored in the memory in a state corresponding to the pixel group in (step S2080). In the example shown in FIG. 19 , after it is determined that 3 ink dots are formed for the pixel group at the upper left corner of the image, the number of ink dots for this pixel group is 3 and stored. the

As mentioned above, after the processing of one pixel group is completed, it is judged whether the processing is complete for all pixels (step S2100). A series of processing, and the number of ink dots formed in the pixel group is stored (step S2080). This process is repeated, after the processing of all pixels in the image is finished (step S2100: yes), the number of ink dots stored in each pixel group is output to the printer 200 (step S2120), and the process shown in Figure 17 is ended. Data generation processing. the

FIG. 20A schematically shows data obtained by performing the above-described number data generation processing on image data. The plurality of rectangles shown in the figure represent pixel groups respectively, and the numerical values displayed in the pixel groups represent the situation in which the number of ink dots formed is stored in the pixel group. In this embodiment, the computer 100 converts the color-converted image data into the data shown in FIG. 20A , and then outputs only the number data stored in each pixel group to the printer 200 as the number data. By outputting in the state of number data in this way, compared with outputting data (ink dot data) indicating whether or not ink dots are formed in each pixel, the amount of data can be reduced and output can be performed quickly. This point will be supplemented below. the

FIG. 20B shows how it is determined whether or not ink dots are formed for each pixel in a pixel group. Thin dotted lines shown in FIG. 20B indicate that a pixel group is composed of a plurality of pixels, and oblique lines in a pixel indicate that it is determined that an ink dot is formed in the pixel. the

Now, assume that the dot data in the state shown in FIG. 20B is output from the computer 100 to the printer 200 . If there is one type of dot, since each pixel has only two states of dot formation and non-formation, one bit of dot data for one pixel is sufficient. Since a pixel group is composed of 8 pixels, the data to be output to the printer 200 as dot data is 8-bit data per pixel group. the

On the other hand, when outputting as number data, since the number of ink dots formed in one pixel group takes only values from 0 to 8, there is only 4-bit data for one pixel group. That is, compared with the case of outputting data indicating whether ink dots are formed in each pixel, the amount of data can be reduced by half. This is number data generation (encoding) processing. Therefore, it is possible to output data to the printer 200 quickly by outputting the number data. the

The number data thus transferred from the computer 100 is decoded in the control circuit 260 of the printer 200 as described below, converted into data indicating whether ink dots are formed in each pixel, and then output to the ink ejection as control data. Nozzles 244-247. the

H. Number data decoding processing:

FIG. 21 is a flow chart showing the flow of number data decoding processing in this embodiment. This processing is implemented by the function of the CPU built in the control circuit 260 of the printer 200 . In the printer 200 of this embodiment, since such processing is performed to convert the number data, it is possible to control the memory capacity required to be mounted in the printer 200, and at the same time realize fast decoding processing. Next, description will be made according to this flowchart. the

After starting the count data decoding process, the CPU of the control circuit 260 first reads the count data transferred from the computer 100 (step S3000), and then executes the process of setting the print pass (step S3020). As a preparation, before describing the content of the processing, a case where the printer 200 prints an image by repeating main scanning and sub-scanning of the ink ejection head while forming ink dots on printing paper will be described. the

As described with reference to FIG. 4 , since a plurality of nozzles are provided on the ink discharge head, if the main scanning is performed while forming ink dots with these nozzles, a plurality of rasters can be formed by one main scanning. However, since the interval between these nozzles is the nozzle pitch p, there is a gap corresponding to the nozzle pitch p between the formed wire grids. If there is a gap between the wire grids as it is, an image cannot be expressed. Therefore, the wire grid is formed in the gap part by slightly shifting the formation position of the wire grid by performing sub-scanning. In addition, the term "pass" refers to an operation in which the head for ink ejection performs main scanning. In addition, the term "printing process" refers to an ink dot row formed by causing the head to perform one main scan while ejecting ink droplets. the

In addition, each raster is not formed in one process, but is formed in multiple processes, mainly according to the need for image quality. That is, when the wire grid is formed in one pass, the wire grid is formed at the position where the nozzle passes. In other words, each wire grid is formed with one nozzle. At this time, among the plurality of nozzles provided on the head, there may occasionally be nozzles having characteristics different from other nozzles, and the grid formed by this nozzle may be different from other grids. Among the formed plurality of rasters, if the specific rasters are different, the image quality will be seriously damaged. On the other hand, if each raster is formed in a plurality of stages, since different nozzles can be used to form ink dots in each stage, it is possible to avoid deterioration of the image quality due to the above-mentioned factors. the

FIG. 22 is a conceptual diagram showing a state where the printer 200 prints an image by forming a raster in a plurality of processes while performing sub-scanning in this way. Furthermore, as mentioned above, although the nozzles for ink ejection are provided with a plurality of (48 nozzles for each color in this embodiment) nozzles for each color, in order to simplify the description, only the nozzles in FIG. The case where there are 4 nozzles will be described. In addition, a case where the nozzle pitch is 3 and one wire grid is formed by two main scans will be described. the

The left half of FIG. 22 shows how the relative position of the ink ejection head with respect to the printing paper is slightly shifted by performing sub-scanning. The elongated rectangle shown in the left half of FIG. 22 represents a head for ejecting ink of one color, and the circle marked with oblique lines in the rectangle schematically represents a nozzle Nz for ejecting ink droplets. As shown in the figure, there are 4 nozzles on the nozzles of each color, and the distance between each nozzle is set to be equivalent to the distance of 2 nozzles (if viewed from the center of the nozzles, it is equivalent to 3 times the diameter of the nozzles). the

In addition, the right half of FIG. 22 shows the state in which ink dots are being formed on the printing paper by the main scanning of the head. The circle marks shown in the right half of FIG. 22 schematically represent ink dots formed on the printing paper. Furthermore, as described above using FIG. 3 , although the actual sub-scanning is carried out by conveying the printing paper, rather than the nozzles for ink ejection moving toward the sub-scanning direction, in FIG. Paper is used as a benchmark, and it appears that the nozzle is moving. the

At the time of printing, first, main scanning is performed while forming ink dots with the head at the position shown in (1) in the figure. By this main scanning, ink dots showing “1” in the right half of FIG. 22 are formed on the printing paper. Then, the head moves two wire grids in the sub-scanning direction. Thereby, the spray head moves to the position indicated by the left half (2) of FIG. 22 . The solid line arrow shown in the left half of FIG. 22 schematically represents the sub-scanning operation of the print head. After the sub-scanning is performed in this way, the main scanning is performed again to form ink dots on the printing paper. By this main scanning, ink dots indicated by “ 2 ” in the right half of FIG. 22 are formed on the printing paper. Then, the sub-scan is performed again, the head is moved to the position indicated by (3), and ink droplets are ejected while performing the main scan to form ink dots indicated by "3". As described above, by repeating the sub-scanning of the head to move the position slightly while forming ink dots, the gaps formed between the grids are finally filled with the grids, and a grid without gaps is formed in the subsequent area. In the example shown in FIG. 22 , after the fifth pass, a raster without gaps is formed on the printing paper. That is, the area after the fifth pass is the effective display area of the image. the

Carefully observe the effective display area in Figure 22, the first row of grid in this area is composed of the ink dots formed in the second process and the ink dots formed in the fifth process (in other words, the grid consists of 2 processes form). For the grid below it (the second line grid in the effective display area), it is composed of ink dots formed in the first process and ink dots formed in the fourth process. In addition, for the first row of the effective display area For a 3-line grid, it is composed of ink dots formed in the 3rd pass and 6th pass. That is, half of the ink dots in the second row are formed before the ink dots in the first row of the effective display area are formed. Then, before forming the remaining ink dots of the second row to complete the grid, half of the ink dots located in the first row are formed, and in the state where neither the grid of the second row nor the grid of the first row is completed, a Half of the ink dot located in row 3. In this way, after forming half of the ink dots from the first row to the third row, the grid of the second row is finally completed in the fourth row. In addition, while the grid of the second row is completed in the fourth pass, half of the ink dots located in the fifth row are also formed. In the 5th process, half of the ink dots located in the 4th row are formed while the 1st line grid is completed, and half of the ink dots located in the 6th line are formed while the 3rd line grid is completed in the 6th process . the

In this way, in the printer 200 , ink dots are not formed sequentially from the pixel located at the top of the effective display area of the image, but an image is printed while forming ink dots in a given order in a mosaic-like manner. Therefore, in step S3020 of FIG. 21 , the processing performed is processing of setting a schedule (print schedule) for ink dots formed from now on. When the number data decoding process shown in FIG. 21 is first performed, the printing process is set to be the first. the

Then, it is judged whether the ink dot data of the pixels (printing pixels) forming ink dots in the set printing process are complete (step S3040). That is, since a plurality of nozzles are provided on the ink ejection head, ink dots can be formed on pixels located in multiple rows in one process, so it is necessary to judge whether the ink dot data of these all pixels are stored in the RAM of the control circuit 260 . When the printing process is set as the first process, the ink dot data has not been generated yet, so it is judged as "No" in step S3040, and the process of detecting a pixel group including printing pixels is performed (step S3060). This processing will be described with reference to FIG. 23 . the

FIG. 23 is an explanatory diagram showing an enlarged effective display area of the image shown in FIG. 22 . As described with reference to FIG. 22, the printing pixels in the first pass are the odd-numbered pixels located in the second row of the effective display area. Here, in this embodiment, as mentioned above, 8 pixels in 2 rows and 4 columns are used as a concentrated pixel group unit to process image data. In FIG. 23 , pixel groups subjected to rounding processing are indicated by dotted rectangles. As shown in FIG. 23 , the printing pixels of the first pass are included in the pixel group of the row indicated by (a) in the figure. Therefore, in step S3060 of FIG. 21 , the pixel group of row a is detected as a pixel group including printing pixels. the

A process is performed to decode the number data of the pixel group thus detected, and to store the dot data of the printing pixel and subsequent pixels in memory (step 3080). Here, the so-called subsequent pixel is a pixel that forms an ink dot next to the printing pixel within the pixel group. As mentioned above, since the ink dots are formed in a mosaic shape in a given order, the printing pixel and the subsequent pixels do not necessarily constitute a continuous process, that is, a continuous process such as the second process and the third process. For example, the pixels included in the pixel group are formed by the second pass, the fourth pass, the fifth pass, and the seventh pass, and when the printed pixels are the pixels of the second pass, the pixels formed in the fourth pass are subsequent pixels. Referring to Fig. 24 below, the processing of storing the ink dot data of the printing pixel and subsequent pixels in the memory will be described. the

24 is a flowchart showing a flow of processing (dot data generation processing) for storing ink dot data of a printing pixel and subsequent pixels in a memory. Next, the contents of the processing will be described based on the flowchart. the

After the processing starts, first, the threshold value corresponding to each pixel of the pixel group to be processed is acquired from the dither matrix (step S4000). As mentioned above, when determining the number of ink dots formed in a pixel group, the gray value of the pixel in question is compared with the threshold value set in the dither matrix (see Figures 17 to 19). In the processing, the threshold value corresponding to each pixel of the pixel group is read from the dither matrix. the

Then, a process is performed to determine a pixel to form an ink dot in the pixel group (step S4020). The pixels to form ink dots in the pixel group can be determined based on the threshold value of the dither matrix read out for each pixel and the number data of the pixel group. This method will be described with reference to specific examples shown in FIGS. 25A to 25E . the

FIG. 25A is a conceptual explanatory diagram schematically showing how data on the number of pixels acquired from the computer 100 is stored in the RAM built in the control circuit 260 of the printer 200 . Now, assume that the pixel group to be processed is the upper left pixel group in FIG. 25A . FIG. 25B is a conceptual explanatory diagram schematically illustrating a situation in which the threshold value set at the position corresponding to the pixel group is acquired from the dither matrix. It can be considered that the threshold values shown in FIG. 25B indicate the order in which ink dots are easily formed in the pixel group. The reason for this is that, as described above using FIG. 19 , when judging whether or not ink dots are formed in a certain pixel, the grayscale value of the image data is compared with the threshold value of the dither matrix, and if the grayscale value is larger, it is judged to form ink dots in that pixel. That is, the smaller the threshold value of the dither matrix shown in FIG. 25B is, the easier it is to form dots. Therefore, it can be considered that the threshold values of the dither matrix indicate the order in which dots are easily formed. the

As shown in FIG. 25A , it can be seen from the number data that the number of ink dots formed in the target pixel group (upper left pixel group) is three. If ink dots are formed according to the sorting in Fig. 25B, then as shown in Fig. 25C, in the figure, the pixel with the smallest threshold value encircled by realization, the pixel with the second smallest threshold value encircled by a dotted circle, and the threshold value encircled by a dotted dotted line Ink dots are formed in the three pixels of the third smallest pixel. FIG. 25D is a conceptual diagram schematically showing how dot data for each pixel in a pixel group is generated by converting the number data in this way. the

In step 4020 of FIG. 24 , by converting the number data into ink dot data in this way, processing is performed to determine the pixels to form ink dots in the pixel group. the

After converting the number data into ink dot data of each pixel, only the ink dot data of the printing pixel and subsequent pixels are stored in the memory, that is, the RAM built in the control circuit 260 (step S4040). Now, the case where the printing process is in the first process is described. The printing pixel is the pixel indicated by "1" in FIG. , that is, the pixel at the left end of the row above and the second pixel from the left. Therefore, in step S4040 of FIG. 24 , ink dot data “0” is stored for each printing pixel, and ink dot data “1” is stored for subsequent pixels. Here, dot data "0" means that a dot is not formed in the pixel, and dot data "1" means that a dot is formed in the pixel. the

In this way, for the target pixel group, after storing the dot data of the printing pixel and subsequent pixels in the memory, the dot data generation process shown in FIG. 24 is ended, and the process returns to the number data decoding process shown in FIG. 21 . Moreover, for the convenience of description, in FIG. 24 and FIG. 25A to FIG. 25E, after generating the ink dot data of all pixels included in the pixel group, only the ink dot data of the printing pixel and subsequent pixels are stored in the memory as Examples are described. Of course, ink dot data for all pixels may not be generated, but ink dot data for printing pixels and subsequent pixels may be generated and stored in the memory. the

In the number data decoding process shown in FIG. 21 , after returning from the above-mentioned ink dot data generation process, the ink dot data of the printing pixel stored in the memory is read and output to the ink ejection head (step S3100 ). Specifically, the ink dot data read from the RAM is written into the drive buffer 261 . In this way, ink droplets are ejected from the corresponding nozzles provided in the head to form ink droplets on the printing paper. the

Then, it is judged whether or not the processing of all pixels has been completed (step S3120). Of course, since only the ink dots of the first course have been formed, the judgment here is "No", and the process returns to step S3020, and this time the printing course is set as the second course. Then, it is judged whether the ink dot data of the pixels formed in the second process are complete (step S3040). As described above, in the first subroutine, in addition to printing pixels, ink dot data is also stored in the memory for subsequent pixels. Therefore, in step S3040, it is checked whether the ink dot data of the printing pixel that is about to form ink dots has not been stored in the memory. the

As shown in FIGS. 22 and 23 , in the second process, ink dots are formed on pixels located in the first row and pixels located in the fourth row of the effective display area of the image. In contrast, although for the pixels located in the first row, the ink dot data has been generated and stored in the memory at the same time as the printing pixels of the first process in the first subroutine, but for the pixels located in the fourth row In terms of pixels, dot data has not yet been generated. That is, since all the pixel data of the printing pixels to form ink dots in the second process are not yet complete, it is judged as "No" in step S3040, and a pixel group including printing pixels without ink dot data is detected (step S3060). Since the printing pixels in the second process that have not stored ink dot data are the pixels located in the fourth row of the effective display area, so in step S3060, the pixel group shown as row "b" in FIG. 26 is detected. the

Then, ink dot data of printing pixels and subsequent pixels are generated for the detected pixel group, and stored in the memory (step S3080). Here, the printing pixels are pixels formed in the second process. In addition, the subsequent pixels, that is, the pixels on which ink dots are formed next in the pixel group are the pixels in the third process. the

After storing the ink dot data of the printing pixel and subsequent pixels in this way, output the ink dot data of the printing process to the nozzle to form ink dots (step S3100), and judge whether the processing has ended for all pixels (step S3120). Then, if there are still unprocessed pixels, return to step S3020 again, set a new printing process, and judge whether all ink dot data constituting the new printing process are complete (step S3040). If all ink dot data have been stored (step S3040: Yes), output these ink dot data to the nozzle to form ink dots (step S3100). On the other hand, if there is a printing pixel without ink dot data (step S3040: No), the pixel group including the printing pixel is detected (step S3060), and the ink dot data of the printing pixel and subsequent pixels are stored (step S3080 ). the

This process is repeated, and when it is determined that the process has been completed for all pixels (step S3120: Yes), the number data decoding process shown in FIG. 21 is skipped, and the image printing process shown in FIG. 15 is ended. the

As described above, in the number data decoding process of this embodiment, when the number data is converted into ink dot data, the ink dot data of the printing pixel and subsequent pixels are stored in the memory. In this way, it is possible to control the memory capacity required to be mounted on the printer 200 side, and at the same time, quickly convert the number data into ink dot data. The reason for this will be described below. the

26A and 26B are conceptual explanatory diagrams schematically showing a situation in which memory is used for ink dot data of pixel groups generated by decoding number data when main scanning of an ink ejection head is repeated and ink dots are formed simultaneously. Specifically, it shows how the memory capacity for storing ink dot data varies with the repeating process of the print head. In addition, in FIG. 26A and FIG. 26B , for the convenience of illustration, only the pixel group indicated by the line "a" in FIG. 23 is taken out, and the memory capacity of one pixel group is shown. In addition, FIG. 26A shows the case where the number data decoding process of this embodiment is performed, and FIG. 26B shows the case where the ink dot data of all the pixels in the pixel group are stored in the memory at once as a reference. the

As shown in Figure 23, in the pixel group of row "a", in addition to the pixels forming ink dots in the first process, there are also pixels formed in the second process, pixels formed in the fourth process, and pixels formed in the fifth process. Pixels formed in the process. Therefore, for the pixel group in row "a", the number data is decoded before the shower head performs the main scan of the first process. Then, as explained with FIG. 21, the ink dot data of the printing pixel and subsequent pixels are stored in the number data decoding process of the present embodiment, so for the pixels of the first pass and the pixels of the second pass, the ink dot data Point data is simultaneously stored in memory. In contrast, in FIG. 26A , ink dot data of 2 pixels formed in the first process and 2 pixels formed in the second process, a total of 4 pixels, are temporarily stored in the memory before the head performs the main scanning of the first process. middle. Then, in the main scan of the first process, the ink dot data of half, that is, 2 pixels, is provided to the nozzle, and then, in the scanning of the second process, the remaining half of the ink dot data of 2 pixels is provided to the nozzle. the

In this way, after the ink dot data of the first process and the second process are output, and before the fourth process, the ink dot data of 4 pixels formed by the fourth process and the fifth process are stored in the memory this time. Then, in the main scan of the fourth process, the ink dot data of 2 pixels are provided to the print head, and in the main scan of the fifth process, the ink dot data of the remaining 2 pixels are provided to the print head. Therefore, for each pixel group located in row "a" in FIG. 23, only the memory with the capacity indicated by oblique lines in FIG. 26A is required to store ink dot data. the

On the other hand, when storing the dot data of all the pixels in the pixel group, as shown in FIG. 26 , it is necessary to store the dot data of 8 pixels in the memory before the first pass. Then, the ink dot data of 2 pixels is output to the head in the main scan of the first pass, and the ink dot data of 2 pixels is also output to the head in the second pass. When the print head finishes the main scanning of the second process, the memory stores the ink dot data of 4 pixels, that is, the ink dot data output to the print head in the fourth process and the fifth process. Then, in the main scan of the fourth process, the ink dot data of 2 pixels are output to the print head, and in the main scan of the fifth process, the ink dot data of the remaining 2 pixels are output to the print head. the

Comparing the area of the part marked with oblique lines in FIG. 26A with the area of the part marked with oblique lines in FIG. 26B, it can be clearly seen that if the image data decoding process of this embodiment is implemented, compared with the area of all the pixels in the pixel group Compared with the case of ink dot data storage, the required memory capacity can be significantly saved. In addition, the temporarily required maximum memory capacity can be significantly saved. the

For the pixels located in the "a" row of Fig. 23, the printing pixel and subsequent pixels are formed in a continuous process, that is, the first process and the second process, or the fourth process and the fifth process, the ink forming the printing pixel After the dot, the next process is used to directly form the ink dots of the subsequent pixels. But even if printing pixels and subsequent pixels are not pixels of such a continuous process, significant savings in memory capacity can be achieved. This will be explained by taking the pixel group shown as the "g" row in FIG. 23 as an example. the

27A and 27B are conceptual explanatory diagrams schematically showing how the number data is converted into ink dot data and stored in a memory for pixels in row "g" of Fig. 23 . FIG. 27A shows a case where the number data decoding process of this embodiment is performed, and FIG. 27B shows a case where ink dot data of all pixels in a pixel group are stored in a memory at once. the

As shown in Figure 23, the pixel group in row "g" includes pixels formed in the seventh process, pixels formed in the tenth process, pixels formed in the eleventh process, and pixels formed in the fourteenth process. pixels. Therefore, the number data of the pixel group in row "g" is decoded before the print head performs the main scanning of row 7. the

As described above with reference to FIG. 21 , in the number data decoding process of the present embodiment, a pixel that forms a dot in the seventh pass and a pixel that forms a dot as a subsequent pixel in the tenth pass add up to four pixels in total. Ink dot data are stored in memory at the same time. That is, as shown in FIG. 27A, before the seventh pass, dot data of 4 pixels are stored in the memory. Among them, the ink dot data of 2 pixels is output to the print head during the main scan of the seventh process, and the ink dot data of the remaining 2 pixels are output to the print head during the main scan of the tenth process. the

Immediately before the 11th pass, immediately before the 11th pass after the main scanning of the 10th pass is completed, dot data of 4 pixels in total formed in the 11th pass and the 14th pass are stored in the memory this time. Then, in the main scan of the 11th process, the ink dot data of 2 pixels is output to the print head, and then in the main scan of the 14th process, the ink dot data of the remaining 2 pixels are output to the print head. Therefore, for each pixel located in the "g"th row in Fig. 23, in order to form ink dots, a memory with a capacity indicated by oblique lines in Fig. 27 is required. the

On the other hand, in the case of storing the dot data of all the pixels of the pixel group, as shown in FIG. 27B , the dot data of 8 pixels is stored in the memory before the seventh process, and then in the main scan of the seventh process The ink dot data of 2 pixels is output to the print head, and the ink dot data of 2 pixels are output to the print head successively in the main scanning of the 10th process, the 11th process, and the 14th process. Therefore, in order to store the dot data of all pixels, a memory with a capacity indicated by oblique lines in FIG. 27B is required. the

In FIG. 27A and FIG. 27B , comparing the areas of the hatched parts in the figures, it can be seen that by implementing the image data decoding process of this embodiment, the memory capacity can be significantly saved. the

Of course, if only saving the memory capacity is considered, and only the ink dot data of the printing pixels are stored, the memory capacity can be saved even more. However, in this way, it is necessary to decode the number data and write the ink dot data of the printing pixels into the memory every time the print head is main-scanned, which makes it difficult to increase the processing speed. In contrast, in this embodiment, there is no need to decode and store in the memory every main scan, so the number data can be quickly converted into ink dot data. the

In the image data decoding processing of the present embodiment, the reason why the memory capacity can be saved as mentioned above and at the same time the fast processing can be implemented is because the ink dot data of all the pixels of the pixel group are not stored at one time, but The reason for storing ink dot data for printed pixels as well as additional pixels. Therefore, in the above-mentioned embodiment, although the ink dot data of the printing pixel and the ink dot data of the subsequent pixel forming the ink dot are simultaneously stored in the memory as an example, the same can be obtained in other cases. Effect. That is, dot data of two passes is not always stored, but dot data of any number of passes can be simultaneously stored as long as the number of passes is less than all the passes included in the pixel group. In addition, it is not necessary to always store the dot data of a plurality of processes, and it is also possible to store only the dot data of one process. In this case, too, the required memory capacity can be significantly saved compared to the case of simultaneously storing ink dot data for all processes. the

Of course, if the pixels that store ink dot data simultaneously with the printing pixels are pixels that form ink dots as close as possible to the printing pixels in the pixel group, the effect of saving memory capacity is better. the

As mentioned above, although various Example was demonstrated, this invention is not limited to the said Example, As long as it does not deviate from the range of the summary, it can implement in various forms. For example, a software program (application program) realizing the above functions may be provided to the main memory of the computer system or an external storage device through a communication line for implementation. Of course, the software program stored in a CD-ROM or a floppy disk can also be read out and implemented. the

Claims (19)

1. print system, the original digital image data that will print finally is converted to expression and has or not the data Jimo point data that forms ink dot, and to be unit as the wiregrating according to the arrangement of the ink dot of this ink dot data formation, image is printed, it is characterized in that possessing:

Print and use head, it possesses a plurality of ink dots that form described ink dot on print media and forms element;

Print with a control module, it adopts at least 2 ink dots to form element and prints each wiregrating that forms image;

Image data conversion unit, it is converted to described original digital image data and changes the data that finish, the described conversion data that finish are to be launched into corresponding to described a plurality of ink dots to form form before the ink dot data of elements, and are in a ratio of the data of compressed form with these ink dot data;

The conversion data storage cell that finishes, it stores this conversion data that finish;

Data are launched the unit, and its conversion that will store data that finish are read successively, expand into the ink dot data of the described a plurality of ink dots formation elements of driving; With

Output unit, its these ink dot data that will be unfolded are exported with a control module to described printing.

2. print system according to claim 1 is characterized in that,

Described data are launched the unit and are possessed:

Have the pixel setup unit in mind, its setting will be judged the pixel of having in mind that has or not the formation ink dot;

Have or not to form the ink dot judging unit, its conversion by the data storage cell storage that finishes in described conversion data that finish launch to comprise the view data that this has pixel in mind, and according to the view data of this expansion, judge that this has pixel in mind and have or not the formation ink dot;

Describedly have pixel in mind and repeat this simultaneously and have or not the judgement that forms ink dot by moving, expand into the unit of the ink dot data that drive described a plurality of ink dots formation elements.

3. print system according to claim 2 is characterized in that,

Described printing is by repeating toward moving and double action on described print media and forming ink dot simultaneously, form the unit as the wiregrating of ink dot row with head;

Described data are launched the unit and are possessed and have the judged result storage unit that judged result that having or not of pixel form ink dot is temporarily stored in mind with described;

Described output unit be among the judged result of described storage, gather described printing with head with at least 1 time after the judged result of moving or the ink dot that double action forms, export to the unit that a control module is used in described printing.

4. print system according to claim 2 is characterized in that, describedly has or not that to form the ink dot judging unit be that conversion from described storage finishes among the data, launch the corresponding described data of having locations of pixels in mind after, judge to have or not the unit that forms described ink dot.

5. print system according to claim 1 is characterized in that,

Constitute with head forms image on print media printing equipment by the image processing apparatus of the described original digital image data of processing that forms separately from each other with described printing;

Described image data conversion unit is assembled in the described image processing apparatus,

Described conversion finishes data storage cell, data expansion unit, output unit and printing with a control module, is assembled in the described printing equipment with first with described printing.

6. print system according to claim 5 is characterized in that,

Described image processing apparatus possesses transfer unit, and it transfers to described printing equipment with the described conversion data that finish;

Described printing equipment possesses the Data Receiving unit, and it obtains described conversion of passing on and finishes after the data, exports to the described conversion data storage cell that finishes;

Described data are launched the unit and are possessed:

Have the pixel setup unit in mind, its setting will be judged the pixel of having in mind that has or not the formation ink dot;

Have or not to form the ink dot judging unit, it finishes the data from the finish conversion of data storage cell storage of described conversion, launches to comprise the view data that this has pixel in mind, and according to the view data of this expansion, judges that this has pixel in mind and have or not the formation ink dot;

Describedly have pixel in mind and repeat this simultaneously and have or not the judgement that forms ink dot by moving, expand into the unit of the ink dot data that drive described a plurality of ink dots formation elements.

7. print system according to claim 1 is characterized in that, described image data conversion unit is by implementing the ink dot data compression that halftone process obtains, the unit of implementing described conversion to described original digital image data.

8. print system according to claim 7 is characterized in that,

Described printing possesses with a control module:

Described printing is being repeated on the described print media toward moving and double action, simultaneously at least in each unit that drives each other during toward moving or double action that the described ink dot at a distance of given interval forms element, forms many described wiregratings with head;

The position mobile unit, it is the described printing relative position with head and described print media, moves on the direction of intersecting with this wiregrating, with the interval between the described wiregrating of filling up formation before with this wiregrating that forms afterwards.

9. print system according to claim 8 is characterized in that,

Described data are launched the unit and are possessed the ink dot data storage cell, its conversion from be stored in described storage unit finishes in the data, expansion includes the ink dot data of the ink dot data that constitute each wiregrating corresponding with described a plurality of ink dots formation elements, and when expansion constitutes the ink dot data of the wiregrating of following this wiregrating formation, this ink dot data storage is prepared against the next wiregrating of formation.

10. print system according to claim 1 is characterized in that,

Described image data conversion unit, the pixel group that obtains with every given a plurality of conclusions for a plurality of pixels that will constitute described image, by according to described view data, determine the number of the ink dot that forms in this pixel group, obtain the described conversion data that finish;

Described data storage cell with the individual logarithmic data of this ink dot as the described conversion data storage that finishes;

The number data of the ink dot that described data expansion unit will be stored are converted to described ink dot data, and possesses the ink dot data storage cell, it is to the pixel groups of M group in each described pixel group, at least once described ink dot data that are converted to of storage simultaneously, wherein M is more than 2 and counts the integer of N less than the group of the described pixel groups that comprises as this pixel group.

11. print system according to claim 10 is characterized in that, described ink dot data storage cell, and as the ink dot data of described M group, the ink dot data that form a plurality of pixel groups of ink dot to the described pixel group of major general are continuously stored simultaneously.

12. print system according to claim 11 is characterized in that, described ink dot data storage cell, and as the ink dot data of described M group, the ink dot data of last remaining a plurality of pixel groups are stored simultaneously to the described pixel group of major general.

13. print system according to claim 10 is characterized in that, described ink dot data storage cell, and the ordering according to forming the pixel of ink dot in each pixel in the described pixel group is converted to described ink dot data with described number data.

14. a printing equipment obtains the data of the image that correspondence will print from the outside, by form ink dot on print media, print the image corresponding to these data, it is characterized in that possessing:

Print and use head, it possesses a plurality of ink dots that form described ink dot on print media and forms element;

Print with a control module, it adopts at least 2 ink dots to form element and prints each wiregrating that forms image;

Change the data storage cell that finishes, its storage conversion data that finish, this conversion data that finish are to be to be launched into corresponding to described a plurality of ink dots to form the form before the ink dot data of elements and be the data of the form compressed than these ink dot data with described image transitions;

Data are launched the unit, and its conversion that will store data that finish are read successively, expand into the ink dot data of the described a plurality of ink dots formation elements of driving; With

Output unit, it is exported to described printing these ink dot data that are unfolded with a control module.

15. printing equipment according to claim 14 is characterized in that,

The described conversion data storage cell that finishes, the pixel group that obtains with every given a plurality of conclusions for a plurality of pixels that constitute described image, will by according to described view data, determine the individual logarithmic data of the ink dot that the number of the ink dot that forms in this pixel group obtains, as the described conversion data storage that finishes;

The number data of the ink dot that described data expansion unit will be stored are converted to described ink dot data, and possesses the ink dot data storage cell, to the pixel groups of M group in each described pixel group, at least once described ink dot data that are converted to of storage simultaneously, wherein M is more than 2 and counts the integer of N less than the group of the described pixel groups that comprises as this pixel group.

16. Method of printing, the original digital image data that will print finally is converted to expression and has or not the data Jimo point data that forms ink dot, and according to these ink dot data, driving is located at a plurality of ink dots of printing with on the head and is formed element, on print media, form ink dot, and be unit, image is printed with wiregrating as the arrangement of ink dot, it is characterized in that

Described original digital image data is converted to the conversion data that finish, and the described conversion data that finish are to be launched into corresponding to described a plurality of ink dots to form the form before the ink dot data of elements and be in a ratio of the data of compressed form with these ink dot data;

This conversion of storage data that finish in storer;

The conversion of this storage data that finish are read successively, expand into and drive the ink dot data that described a plurality of ink dots form elements;

The ink dot data of this expansion are arranged, print each wiregrating that forms image to adopt at least 2 ink dots to form element;

According to the ink dot data of this arrangement, the ink dot that drives described printhead forms element.

17. Method of printing according to claim 16 is characterized in that,

In the described storer, the pixel group that obtains with every given a plurality of conclusions for a plurality of pixels that constitute described image, will be by according to described view data, determine the individual logarithmic data of the ink dot that the number of the ink dot that forms in this pixel group obtains, as the described conversion data storage that finishes;

The expansion of described ink dot data, the number data of the ink dot of described storage are converted to described ink dot data, and pixel groups to M group in each described pixel group, at least once described ink dot data that are converted to of storage simultaneously, wherein M is more than 2 and counts the integer of N less than the group of the described pixel groups that comprises as this pixel group.

18. Method of printing, the original digital image data that will print finally is converted to expression and has or not the data Jimo point data that forms ink dot, and according to these ink dot data, driving is located at a plurality of ink dots of printing with on the head and is formed element, on print media, form ink dot, and be unit, image is printed with wiregrating as the arrangement of ink dot, it is characterized in that

Described original digital image data converted to be launched into corresponding to described a plurality of ink dots form the form before the ink dot data of elements and be in a ratio of the data of compressed form, finish data storage in storer as conversion with these ink dot data;

The conversion of this storage data that finish are read successively, expand into and drive the ink dot data that described a plurality of ink dots form elements;

The ink dot data of this expansion are arranged, print each wiregrating that forms image to adopt at least 2 ink dots to form element;

According to the ink dot data of this arrangement, the ink dot that drives described printhead forms element.

19. Method of printing according to claim 18 is characterized in that:

In the described storer, the pixel group that obtains with every given a plurality of conclusions for a plurality of pixels that constitute described image, the individual logarithmic data of the ink dot that will obtain by the number of the ink dot that determines according to described view data to form in this pixel group is as the described conversion data storage that finishes;

The expansion of described ink dot data, the number data of the ink dot of described storage are converted to described ink dot data, and pixel groups to M group in each described pixel group, at least once described ink dot data that are converted to of storage simultaneously, wherein M is more than 2 and counts the integer of N less than the group of the described pixel groups that comprises as this pixel group.

Images