JP2000238347A - Printer control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance printing quality due to a printer engine for binary output and to increase a processing speed. SOLUTION: In a printer controller (printer control device) 20, the image data sent from a host computer 1 is imagewise developed as multivalue data in a printable manner in a printer engine 10 and the imagewise developed multivalue image data is temporarily stored in an RAM 6 and the operation of a video DMA is started by a DMA controller 7. The DMA controller 7 starts the operation of the video DMA to allow a gradation decoder 21 to read the multivalue data stored in the RAM 6. The gradation decoder 21 converts the read multivalue image data to a resolution higher than that at a time of imagewise development to output the same to the printer engine as binary data through an engine I/F 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer control device (generally referred to as a "printer controller") which develops an image of image data created on a host computer and sends it to a printer engine such as a laser beam printer to execute printing. In particular, the present invention relates to a technique for improving gradation by printing at a high resolution.

[0002]

2. Description of the Related Art In a conventional printer controller,
As a technique for outputting multi-valued data, for example, Japanese Unexamined Patent Publication No.
There is one which is found in JP 210734. Therefore, the technique will be described with reference to FIGS.

FIG. 21 is a block diagram showing a configuration example of a printer system using a conventional printer controller. This printer system is composed of a host computer 1, a printer controller 2, and a printer engine 10, and the printer controller 2 and the printer engine 10 are integrated into a printer, but other printers are also included. .

The printer controller 2 includes a host interface (hereinafter, “interface” is abbreviated as “I / F”) 3, a CPU as a central processing unit, a ROM as a program memory 5, and a RAM as a data memory.
6 are mutually connected by a system bus 9 to constitute a microcomputer. Further, a video DMA controller (VDMA) connected to the system bus 9
C) 7 and an engine I / F 8.

[0005] The host computer 1 is connected to the host I / F3, and the printer engine 10 is connected to the engine I / F8. In this printer system,
The user creates image data to be printed by the host computer 1, designates a printer for printing, and issues a print command for the created image data.

When a print command is issued, the host computer 1 converts image data into a command code system that can be interpreted on the printer controller 2 side by software called a printer driver 1a suitable for the connected printer. The converted image data is output to the host I / F 3 of the connected printer.

In the printer controller 2, the host I / O
When reception of the image data to be printed is started in F3, the CPU 4 draws the image data on the RAM 6 according to the code information (program) written in the ROM 5 and develops the image data. Next, after the CPU 4 develops the image on the RAM 6, it issues a print start command to the printer engine 10 to start printing, and outputs the developed image data to the printer engine 10 via the engine I / F 8. To execute printing.

However, usually, when image data is output to the printer engine 10 (video output), an enormous amount of data must be transferred in a short period of time. Speeding up. By performing such processing and operations, it becomes possible to print the image data created by the user.

A video I / F for output to a printer engine is roughly divided into a data through system in which the gradation of image data is expressed by 1 bit as shown in FIG. There is a multi-value system in which the gradation of image data as shown is represented by multi-values. In the example of FIG. 23, the number of gradations of the image data is represented by 4 bits (16 gradations).

In the data through system, a data line for transferring image data is directly connected to a laser diode used when performing image forming processing in a printer engine, and a laser diode is used in accordance with image data from a printer controller. Is directly driven to perform writing.

On the other hand, in the multi-value system, as shown in FIG.
In (1, T2), a difference in data skew occurs because each data line is separately connected. Therefore, a pixel clock for image data transfer is generated on the printer controller side and output on the video I / F. Then, the printer engine synchronizes with the pixel clock, absorbs the difference in data skew, and performs writing with a laser diode.

Therefore, the data through system is mainly used for video I / Fs of laser printers and the like, and printing can be performed by directly controlling the resolution from the printer controller side. It can be said that there is. On the other hand, in the multi-value system, in a digital copying machine,
Since the gradation of one pixel must be excellent, the printing itself is often expressed by multiple values such as 16 gradations or 256 gradations by one pixel.

For this reason, a multi-value video I / F is often used as an I / F when a digital copying machine is used as a printer, and is used for a printer engine excellent in gradation expression within one pixel. ing. However, on the other hand,
As the resolution is increased, it is naturally necessary to use a high-speed pixel clock. Therefore, it can be said that high resolution has a limit.

Next, the technology described in Japanese Patent Application Laid-Open No. H5-221034 will be described. This technology assumes that input image data is multi-valued data, the printer engine that performs printing can change the resolution (multi-resolution engine), and the number of output gradations is lower than the number of input gradations. It was done. Under these conditions, when printing at high resolution, the number of pixels that can be printed per unit area increases, so area gradation processing is performed within that unit area, and when the number of output gradations is small. Also, printing can be performed without losing the gradation.

Next, the technology disclosed in Japanese Patent Application Laid-Open No. 8-289146 will be described. This technique relates to a method of generating write data when a digital copying machine is used as a printer in a printer controller connected to a digital copying machine capable of printing with multiple values per pixel and a data I / F video I / F. The logical sum of image data sent by the data through method and data obtained by PWM (pulse width) modulation is obtained, thereby enabling multi-value writing.

Further, as a recent printer controller, there is a printer controller which employs a technology (anti-aliasing processing) for eliminating jagged edges. The technology uses a line buffer to extract diagonal lines in an image and pseudo-increases the resolution to complement the dots. Mainly to improve the quality of high-frequency components of text data with a monochrome laser printer used.

[0017]

In recent years, with the development of laser printers, various printers have been developed.
For example, a printer equipped with a printer controller so that a digital copier can be used as a printer, or one pixel (1
Each of them is capable of expressing a gradation per dot in a multi-valued manner, and is also referred to as a color laser printer, each having a special color.

In particular, a color laser printer is required to print halftone image data (especially a low density portion) such as image data and graphic data with high quality. It is important to represent the value image data. When color image data is printed by the electrophotographic method, it is preferable to increase the resolution and reduce the amount of change in the dot diameter in order to improve the gradation. The characteristic that a higher quality image can be obtained than that by increasing the number of gradations per dot,
Proven in experiments.

However, in the conventional printer control device, the technique of changing the resolution and printing is used only for improving the quality of the edge portion of the text data, and the halftone image data for printing with a color printer or the like is used. The value of was developed at the resolution of the image to be finally printed. Accordingly, when importance is placed on gradation, it is necessary to use a printer engine capable of expressing gradation per pixel in multiple values.

A printer engine capable of expressing multi-values is:
As described above, not only is the print quality (image quality) worse than in the case where the change in dot diameter is reduced due to the characteristically high resolution, but also the multi-value print control adjusts the emission power of the laser diode in an analog manner. Therefore, delicate control is very difficult, and furthermore, when the resolution is as high as about 600 DPI, the control is almost impossible. In addition, since it is necessary to use a pixel clock on the video I / F, there is a limit in increasing the speed of the printer itself. Accordingly, since a high-speed pixel clock is used, unnecessary noise is radiated. Was.

The present invention has been made in view of the above points, and a printer control device for (1) for binary output.
It is an object of the present invention to improve the print quality of a printer engine capable of expressing gray scales per pixel only with binary values, and to shorten the time required for printing by speeding up processing.

[0022]

SUMMARY OF THE INVENTION According to the present invention, there is provided a printer control apparatus for expanding image data created on a host computer, sending the developed image data to a printer engine, and executing printing. It is characterized by the following.

According to a first aspect of the present invention, there is provided a rasterization processing means for rasterizing image data sent from a host computer as multi-valued data so that the image data can be printed by a printer engine, Image storage means for temporarily storing image data of a value, and conversion processing for converting multi-valued image data stored in the means to a resolution higher than the resolution at the time of image development and outputting it as binary data to a printer engine Means.

With this configuration, when printing the image data sent from the host computer by the printer engine for binary output, the image data is developed as multi-valued data, and the image is converted to a multi-level data. The resolution is increased to improve the tonality and output to the printer engine as binary data (multi-valued image data stored in the image storage means is converted to a higher resolution than the resolution at the time of image development, and is converted to binary data. Output to the printer engine), so that the printing quality of the binary output printer engine can be improved.

When increasing the resolution of image data, the image data of the image data is developed at a low resolution without increasing the number of pixels, and the image storage means can be managed by the gradation of the pixel. Can be simplified and the processing can be speeded up.

According to a second aspect of the present invention, in the printer control device of the first aspect, the conversion processing means determines the phase of the binary image data to be output based on the multi-valued image data stored in the image storage means. It has means for controlling.

According to the second aspect of the invention, when increasing the resolution of the multi-valued image data stored in the image storage means (generating a pulse of the binary image data), an output is performed based on the image data. By controlling the phase of binary image data to be controlled (gradually thickening dots), when the image data is output to a printer engine and printed, isolated dots are eliminated and output gradation is improved. Therefore, the printing quality can be further improved.

According to a third aspect of the present invention, there is provided the printer control device according to the first or second aspect of the present invention, wherein
An edge correcting means for detecting an edge of the image data of the value and correcting the detected edge is provided.

According to the third aspect of the present invention, when binary image data is output to the printer engine, its edge is detected and the detected edge is corrected (smoothed without jaggedness). Accordingly, the print quality at the edge of image data such as text data can be improved.

According to a fourth aspect of the present invention, in the printer control device of the first or second aspect, the expansion processing means converts the image data sent from the host computer into multi-valued data so that the image data can be printed by the printer engine. When the image is developed, a means for correcting an edge portion in consideration of a phase when the image data is output as binary data from the conversion processing means is provided.

According to the fourth aspect of the present invention, when image data such as text data is developed as multi-valued data, the phase (high resolution) when the image data is output as binary data from the conversion processing means is obtained. By correcting the edge portion in consideration of the phase at the time of printing, the print quality at the edge portion of image data such as text data can be improved as in the invention of claim 5.

According to a fifth aspect of the present invention, in the printer control apparatus of any one of the first to fourth aspects, a line buffer for temporarily storing one line or a plurality of lines of image data to be processed by the conversion processing means is provided. Things.

According to the fifth aspect of the present invention, when the resolution conversion of the multi-valued image data stored in the image storage means is performed, the resolution conversion of each pixel data in the sub-scanning direction is also performed. By temporarily storing the obtained binary image data for one line or a plurality of lines in the line buffer and outputting the data, the data transfer at the time of printing by the printer engine can be efficiently performed. Therefore, the bus traffic can be reduced, and the processing speed can be further increased.

According to a sixth aspect of the present invention, there is provided the printer control device according to any one of the first to fifth aspects, wherein
There is provided a data selection means for selecting the value image data or the multi-value image data from the image storage means and outputting it to the printer engine.

According to the sixth aspect of the present invention, binary image data from the conversion processing means or multi-valued image data from the image storage means can be selected and output to the printer engine. A printer engine that can express the gradation per pixel by multi-valued values can also be used. That is, since the same printer controller can be connected to various printer engines, the cost of the entire system can be reduced.

According to a seventh aspect of the present invention, there is provided a developing process for developing multi-valued or binary image data sent from a host computer as binary data or multi-valued data so that the image data can be printed by the printer engine. Means, image storage means for temporarily storing binary or multi-valued image data developed by the means, and resolution of the binary or multi-valued image data stored in the means at the time of image development. Conversion processing means for converting to high resolution and outputting as binary data to the printer engine is provided, and multi-valued or binary image data sent from the host computer can be printed on the expansion processing means by the printer engine. When an image is developed as binary data or multi-valued data, the above-described multi-valued or binary image data is subjected to area gradation processing.
Equipped with means for controlling the phase as well as the value or multi-value,
The conversion processing means includes means for controlling the phase of the binary image data to be output based on the binary or multi-valued image data stored in the image storage means.

With this configuration, when multi-valued or binary image data sent from the host computer is printed by the printer engine for binary output, the image data is converted into binary or multi-valued data. (At this time, the multi-valued or binary image data from the host computer is binarized or multi-valued by area gradation processing such as dither processing or error diffusion processing, and the phase is controlled). In order to improve the gradation, the resolution is increased and output as binary data to the printer engine (at this time, the phase of the binary image data to be output is controlled based on the image data that has been developed). Tonality is greatly improved,
The printing quality by the printer engine for binary output can be greatly improved.

When increasing the resolution of image data, the image data of the image data is developed at a low resolution without increasing the number of pixels, and the image storage means can be managed by the gradation of the pixel. Can be simplified and the processing can be speeded up.

According to an eighth aspect of the present invention, in the printer control device according to the seventh aspect, when the multi-valued or binary image data is binarized or multi-valued by area gradation processing in the expansion processing means. The reference matrix used has a larger number of pixels in the main scanning direction than in the sub-scanning direction.

When the resolution is increased only in the main scanning direction when the image data is output to the printer engine and printed, the configuration is such that the reference matrix can be treated as a square in the print result, and a more accurate level is obtained. Tone expression can be made possible and the printing quality can be improved.

[0041]

Embodiments of the present invention will be specifically described below with reference to the drawings. In each of the embodiments, a color printer controller (hereinafter simply referred to as “printer controller”) and a color laser printer engine (hereinafter simply referred to as “printer engine”) are used. A monochrome laser printer engine may be used.

First, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration example of a printer system using a printer controller as a printer control device according to a first embodiment of the present invention, and portions corresponding to FIG. 21 are denoted by the same reference numerals. .

This printer system is composed of a host computer 1, a printer controller 20, and a printer engine 10. The printer controller 20 and the printer engine 10 are integrated to form a printer. Including things.

The printer controller 20 has a host I /
F3, a CPU serving as a central processing unit, a ROM 5 serving as a program memory, and a RAM (image storage means) 6 serving as a data memory are mutually connected by a system bus 9 to constitute a microcomputer.

Further, a video DMA controller (VDMAC) 7 and a gradation decoder (conversion processing means) 21 connected to the system bus 9 and an engine I / F 8 connected to the gradation decoder 21 are provided. And
The host computer 1 is connected to the host I / F3, and the printer engine 10 is connected to the engine I / F8.

In this printer system, the user uses the application software on the host computer 1 to create image data to be printed. At this time, as the image data created by the user, there are various image data such as one that covers a plurality of pages and one that is created as color data. Then, when the creation of the image data is completed, the user selects a printer to be printed out of the printers connected to the host computer 1 and capable of printing, and issues a print command (print execution command). .

At this time, the print command from the user includes designation of the number of copies, designation of color or monochrome, designation of the enlargement or reduction ratio, designation of the size of the sheet, and a plurality of pages on one sheet. Various print modes are designated, such as designation of whether to perform collective printing for collective printing and designation of use of the toner save function.

When a print command is issued by a user, the printer is connected by software called a printer driver 1a stored in the host computer 1 so as to satisfy various modes specified by the user. The printer controller 20 converts the image data into a code that can be decoded by the printer controller 20 and outputs the converted image data (code information) to the printer controller 20.

The printer controller 20 has a host I / F 3 comprising a network and various interfaces.
When the reception of image data from the host computer 1 is started, an interrupt is generated to notify the CPU 4 that a print command has been issued, and the received image data is buffered in the RAM 6 and temporarily stored. .

The CPU 4 develops an image of the received and buffered image data in the RAM 6 so that the image data can be printed by the printer engine 10, and converts the received image data as bit information into bit map information (image data).
Is converted and stored. At that time, the CPU 4
The image developing portion 6 is virtually divided into a plurality of bands in the sub-scanning direction to develop the image. The developed image data is stored in the RAM 6 in band units.

At this time, by managing the memory of the RAM 6, for example, as shown in FIG.
The image is developed in the empty area, but it is not necessary to group each color component.

By repeating such processing, one of the image data received by CPU 4
When the image development for the page is completed, the CPU 4 detects the state of the printer engine (color printer engine) 10, and if it is in the ready state, issues a print start command to the printer engine 10 to execute the printing operation. .

Here, when developing the image data into an image, the CPU 4 develops the image data as multi-valued data in the RAM 6 and stores it, and stores the multi-valued image data for one page (multi-valued data). At the time when all
Printing is started, and the video DMA controller 7 performs video DMA operation (directly accesses the RAM 6 to convert the multi-valued image data into a high-speed printer engine 10).
), And the number of gradations of the multi-valued image data developed by the gradation decoder 21 is set.

The video DMA controller 7 controls the video D
When the MA operation is started, a read signal (RD) is output to the gradation decoder 21 to cause the gradation decoder 21 to read the multi-valued image data stored in the RAM 6. The gradation decoder 21 converts the read multi-valued image data into a high resolution, that is, a resolution higher than the resolution at the time of image development, and outputs the binary data to the engine I / F 8 as binary data.

The engine I / F 8 sets the time during which the laser diode of the printer engine 10 emits light to a resolution that can be output by the printer engine 10 based on the binary image data (binary data) from the gradation decoder 21. The data is converted to a suitable time, and the binary data of each pixel is output to the printer engine 10. The printer engine 10 performs a printing operation including an operation of driving the laser diode to emit light from the binary image data sent from the printer controller 20 by a data through method.

In general, in a laser printer, there is no data around, and it is difficult to print an isolated dot, and it is difficult to print further as the resolution increases. By performing image development so as not to isolate dots at the time of high resolution, printing can be performed with good gradation and print quality can be improved.

The ROM 5 stores program codes for operating the CPU 4, font information used for image development of text data, and the like. The functions of the expansion processing means and the like in the present invention are the same as those described in
This is realized by U4 operating according to the program code written in ROM5.

Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a configuration example of a printer system using a printer controller which is a printer control device according to a second embodiment of the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals. .

The printer controller 30 of the second embodiment differs from the printer controller 20 of the first embodiment shown in FIG. , An edge correction unit (edge portion correction means) 31 is provided.

In the printer controller 30, the edge correction unit 31 converts the multi-valued image data into a high resolution (converted to a higher resolution than the resolution at the time of image development) by the gradation decoder 21. When the data is output as data, the edge part of the binary image data is detected, and the detected edge part is corrected (smoothed without jaggedness). Thereby, the printing quality of a line drawing or the like can be improved.

In the first and second embodiments, when the CPU 4 develops image data such as text data, the CPU 4 converts the image data into multi-valued data at a resolution lower than the printing resolution. At this time, the image is developed so that the edge portion is corrected and smoothed in consideration of the phase when the image data is output from the gradation decoder 21 as binary data. It is also possible to improve the printing quality of data and the like.

In developing the binary (or multi-level) image data as multi-level (or binary) data, the binary (or multi-level) image data is subjected to dither processing, error diffusion processing, or the like. Can be multivalued (or binarized) by the area gradation processing (processing by the area gradation method).

At this time, when the gradation is represented by a dither pattern (reference matrix used for dither processing) or a reference matrix used for other area gradation processing such as error diffusion processing, printing is performed at high resolution. In some cases, a reference matrix is generated in consideration of how dots are thickened with surrounding dots, and the dot diameter is gradually increased when printing is performed by the printer engine 10, so that gradation expression can be improved. It is also possible to improve the print quality of image data and the like.

Furthermore, in a normal laser printer, increasing the resolution in the main scanning direction (the direction orthogonal to the sheet transport direction) only requires determining the pulse width of the data bits. Because there is, it is easy.
However, it is difficult to increase the resolution in the sub-scanning direction (paper transport direction) because mechanical control is required and the cost is greatly increased.

Therefore, when creating a reference matrix to be used for other area gradation processing such as a dither pattern or an error diffusion processing at the resolution at the time of printing by the printer engine 10 at the final printing, Consider the phase of (control)
In addition to creating the reference matrix, the reference matrix is made a matrix that is horizontally long in the main scanning direction (the number of pixels in the main scanning direction is made larger than the number of pixels in the sub-scanning direction). Since the same area gradation processing can be adopted not only in the scanning direction but also in the sub-scanning direction, the print quality can be further improved.

Next, a third embodiment of the present invention will be described. FIG. 4 is a block diagram showing a configuration example of a printer system using a printer controller as a printer control device according to a third embodiment of the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals. . In the printer controller 40 of the third embodiment, the printer controller 20 of the first embodiment shown in FIG.
The difference between this is that the gradation buffer 21
1 are connected to each other.

In the printer controller 40, the CP
When U4 develops the image data as multi-valued data, the multi-valued image data is also generated in the sub-scanning direction and stored in the RAM 6 (the multi-valued multi-valued image data is generated in the RAM 6). After that, the video DMA controller 7 starts the video DMA operation. Upon starting the video DMA operation, the video DMA controller 7 causes the gradation decoder 21 to sequentially read multi-valued image data for a plurality of lines (two lines in this example) from the RAM 6.

The gradation decoder 21 converts the read multi-valued image data of a plurality of lines into a higher resolution than the resolution at the time of image development, and converts the image data of the first line into binary data as it is in the engine I / F 8. At the same time, the image data of the next line is temporarily stored as binary data in the line buffer 41, and when the image data of the next line is output to the engine I / F 8, the image data is stored in the line buffer 41. The output binary image data is output to the engine I / F 8.

Thereafter, the above processing is repeated. As described above, at the time of the video DMA operation, the multi-valued image data of a plurality of lines are read from the RAM 6 at a time and the time related to the overhead is reduced, so that the throughput of the entire system can be improved and the speed can be increased. Become.

Next, a fourth embodiment of the present invention will be described. FIG. 5 is a block diagram showing a configuration example of a printer system using a printer controller as a printer control device according to a fourth embodiment of the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals. .

The printer controller 50 according to the fourth embodiment differs from the printer controller 20 according to the first embodiment shown in FIG.
MA controller 7, gradation decoder 21, and engine I
/ F8 is provided with a selector (data selection means) 51 connected to the system bus 9.

The video DMA controller 7 controls the video D
When the MA operation is started, the multi-valued image data stored in the RAM 6 is directly read and output to the selector 51, and a read signal (RD) is output to the gradation decoder 21 to output the multi-valued image data stored in the RAM 6. Is read by the gradation decoder 21.

The gradation decoder 21 converts the read multi-valued image data into a higher resolution than the resolution at the time of image development, and outputs it to the selector 51 as binary data. The selector 51 selects multi-valued image data from the video DMA controller 7 or multi-valued image data from the gradation decoder 21 according to an instruction from the CPU 4 and
/ F8.

In this manner, the printer controller 50 is capable of not only the printer engine 10 capable of expressing the gradation per pixel in binary values but also the printer engine capable of expressing the gradation per pixel in multiple values. Since an engine can be connected, the cost of the entire system can be reduced.

Next, a fifth embodiment of the present invention will be described. FIG. 6 is a block diagram showing a configuration example of a printer system using a printer controller which is a printer control device according to a fifth embodiment of the present invention, and portions corresponding to FIGS. 1, 3 to 5 are the same. Signs are attached.

The printer controller 60 of the fifth embodiment differs from the printer controller 20 of the first embodiment shown in FIG.
A selector 51 connected to the system bus 9 is provided between the MA controller 7 and the engine I / F 8, an edge correction unit 31 is provided between the gradation decoder 21 and the selector 51, and a line buffer is provided in the gradation decoder 21. 41 is provided by connecting them.

In the printer system using the printer controller 60, a user creates image data to be printed by using application software on the host computer 1. At this time, as the image data created by the user, there are various image data such as one that covers a plurality of pages and one that is created as color data.

When the creation of the image data is completed, the user selects a printer to be printed out of the printers connected to the host computer 1 and capable of printing, and issues a print command. At that time, the print command from the user includes designation of the number of copies, designation of color or monochrome, designation of enlargement or reduction ratio, designation of paper size, and printing of multiple pages on one sheet Various print modes are designated, such as designation of whether or not to perform aggregate printing.

When a print command is issued by the user, the printer is connected by software called a printer driver 1a stored in the host computer 1 so as to satisfy various modes specified by the user. The printer controller 60 converts the code into a code that can be decoded, and outputs the converted image data (code information) to the printer controller 60.

At this time, for example, as shown in FIG. 2, the image data is managed by being divided into a plurality of bands in the sub-scanning direction. At this time, for a band in which no image data to be printed exists, only information indicating that the band is blank is output to the printer controller 50.

In the printer controller 60, a host I / F 3 composed of a network and various interfaces
When the reception of image data from the host computer 1 is started, an interrupt is generated to notify the CPU 4 that a print command has been issued, and the received image data is buffered in the RAM 6 and temporarily stored. .

The CPU 4 develops the image data received and buffered as multi-valued data in the RAM 6 so that the image data can be printed by the printer engine 10, and converts the received image data as bit information into bitmap information (image data). ) And store it. that time,
The CPU 4 develops the image in the RAM 6 by virtually dividing the image developing portion into a plurality of bands in the sub-scanning direction. The developed image data is stored in the RAM 6 in band units.

At this time, by the memory management of the RAM 6, for example, as shown in FIG.
The image is developed in the vacant area of No. 6, and each band of each color is subjected to compression processing and written without being taken in order. Also, a band having no image data to be printed is treated as a blank band, and only a band having image data to be printed is developed.

Note that the printer controller 60 does not necessarily need to be able to perform compression processing. Also, even in an environment where compression processing is possible, if the capacity of the RAM 6 is large enough to store enough data, the image data may be stored as it is without performing compression processing. The processing speed increases as much as no processing is performed. Also,
When performing the compression process, there are a case where the compression process is performed using a dedicated compressor and a case where the compression process is performed by the CPU 4.

By repeating the above-described processing, when the image development for one page of the image data received by the CPU 4 is completed, the CPU 4
Detects the state of the printer engine (color printer engine) 10 and, if it is in the ready state, issues a print start command to the printer engine 10 to execute the printing operation.

Next, the processing according to the present invention by the printer controller 60 will be described in detail with reference to FIGS. 7 to 20. Here, when developing the image data as multi-valued data,
0DPI, 2-bit gradation per pixel, 12
The description is made on the assumption that printing is performed at 00 DPI and 1-bit gradation (binary) per pixel.

When printing at 600 DPI and 1-bit gradation (binary) per pixel, it is assumed that the pulses (binary image data) output to the printer engine 10 are as shown in FIG. As shown in the truth table of FIG. 8, when 2 bits representing each pixel of multi-valued image data when the image is developed and stored are D1 and D0, the CPU 4 performs the following processing.

That is, D1 and D0 are "0",
In the case of “0”, image development is performed so that a pulse for 2 dots (2 pixels) is not generated from the pulse gradation decoder 21 (so that white data for 2 dots is output),
D1 and D0 are “0”, “1” or “1”, respectively.
In the case of “0”, the gray scale decoder 21 outputs 600 DPI
The image is developed so that a pulse having a width of 1200 DPI, which is half of the pulse width of, is generated.

At this time, D1 and D0 are respectively
In the case of “0” and “1”, “1” and “1” are set so that the dot is right-justified (the next pixel side in the main scanning direction).
In the case of “0”, there is a difference that a pulse is generated such that the dot is left-justified (one pixel before the main scanning direction). D1 and D0 are “1”,
In the case of “1”, two 1200 DPI pulses overlap, and consequently the width is the same as the pulse width of 600 DPI and one dot.

When the image is developed as in this example, normally, when expressing in 2-bit gradation, four values (four levels) can be expressed, but here, only three values can be expressed. However, in particular, in the case of color image data that needs to be printed with good gradation by a color laser printer or the like, processing using the area gradation method (area Tone representation by tone processing has the characteristic of obtaining a high-quality image. Therefore, even if the gradation per pixel is ternary at 600 DPI, it is more sufficient to increase the gradation than one dot. Quality is improved.

Next, the gradation decoder 21 converts the resolution so that the values in the truth table shown in FIG. 8 actually become the respective pulses shown in FIG. 8 (change from 600 DPI to 1200 DPI). ). For this reason, the pixel clock at the time of generating the pulse is output at a frequency twice as high as the frequency at which the pixel clock is output at the normal 600 DPI. As a result, one pixel clock at 600 DPI becomes two clocks. Of the two bits D0 and D1, D0 (binary data) is used in the first half clock, and D1 (2 data) is used in the second half clock.
Value data).

By the above processing, the image data developed as multi-value data (multi-value image data) is converted to a higher resolution than the resolution at the time of developing the image, and is output as binary data (pulse data). Therefore, printing can be performed by the printer engine 10 for binary output using the data through method. Further, the gradation decoder 21 converts the multi-valued image data into a higher resolution than the resolution at the time of image development and, when outputting the binary data, controls the phase (gradation) as described below. You can do it.

For example, as shown in FIG.
If there is a 4-pixel square image represented by DPI,
The multi-valued image data corresponding to the image is converted to a higher resolution than the resolution at the time of image development, and the phase is controlled when outputting as binary data. The area ratio between the case where the thickness is maximized (the density is increased) as shown in FIG. 7 and the case where the density is maximized (the density is reduced) as shown in FIG. Can be expressed.

In this example, since only the highest and lowest densities of the image are expressed, merely changing the method of allocating the densities of the pixels increases the types of halftone images between them.
As a result, the gradation can be increased. In the case of a curved line, for example, as shown in FIGS. 10A, 10B, and 10C, the gradation can be similarly increased by changing the distribution method of the density of each pixel.

For example, when there is an image as shown in FIG. 11A, if it is desired to slightly increase the density of the next succeeding pixel and increase the density as a whole, (b) of FIG. ) (c)
However, in the case of (c) in the figure, if a normal laser printer (particularly a color laser printer) separates the dots, the toner is transferred to the paper. Is difficult, the dots are scattered, and the effect of increasing the density is not so much exhibited.

On the other hand, in the case shown in FIG. 11B, the toner can also be applied to the surroundings, so that the density can be increased. Therefore, when determining the density, the tone decoder 21 considers adjacent dots and the like and controls the phase of the binary data to be output, so that the above-described problem is solved and the tone is more accurately determined. Can be raised.
Note that, in this example, the case of a straight line is handled, but it is obvious that the same can be said for a curved line or arbitrary data.

On the other hand, the edge correcting section 31 detects an edge portion of the binary image data output from the gradation decoder 21 and corrects the detected edge portion. For example, when an image (edge image) corresponding to the detected edge portion is as shown in FIG.
Two binary data (1) corresponding to the image portion of (row, d column)
"0" and "0" as bit data) are changed to "1" and "0", respectively. As a result, the edge image becomes smooth as shown in FIG. 3B, and the image quality is improved.

Note that other edge portions can be corrected in the same manner as described above. Further, when the CPU 4 develops image data from the host computer 1 as multi-value data, the edge portion is corrected in advance in consideration of the phase of the binary image data output by the gradation decoder 21. You can also. For example, the multi-value data (2-bit data) D1 and D0 corresponding to the image portion of the coordinates (b row and d column) of the edge image shown in FIG. 12A are changed to “1” and “0”, respectively. I do.

When developing the image data as multi-valued data, the CPU 4 generates multi-valued image data also in the sub-scanning direction and stores it in the RAM 6 (multi-valued image data of a plurality of lines). Is generated and stored in the RAM 6).
In order to start the MA operation, when the video DMA controller 7 starts the video DMA operation, the video DMA controller 7 directly reads the multi-valued image data stored in the RAM 6 and outputs it to the selector 51, and also outputs the multi-valued data for a plurality of lines from the RAM 5. Is read by the gradation decoder 21.

The gradation decoder 21 converts the read multi-valued image data of a plurality of lines (two lines in this example, but three or more lines) to a resolution higher than the resolution at the time of image development. Then, the image data of the first line is output as binary data to the selector 51 as it is, and the image data of the next line (or image data of a plurality of lines) is temporarily stored in the line buffer 41 as binary data. Remember.

Then, when outputting the image data of the next line to the selector 51, the binary image data stored in the line buffer 41 is output to the selector 51. The selector 51 receives the multi-value data from the video DMA controller 7 or the gradation decoder 2 in accordance with an instruction from the CPU 4.
The multi-valued image data from 1 is output to the engine I / F 8. Thereafter, the same processing as described above is repeated.

As described above, during the video DMA operation, the RA
Reads multi-valued image data for a plurality of lines from M6,
By reducing the time associated with overhead,
It is possible to improve the throughput of the entire system and increase the speed. Also, the printer controller 60
Can be connected to a printer engine capable of expressing grayscales per pixel only in binary values in addition to the printer engine 10 capable of expressing grayscales per pixel only in binary values. The overall cost can be reduced.

The CPU 4 is connected to the host computer 1
The multi-valued or binary image data sent from the computer can be developed as binary data or multi-valued data. When multi-valued or binary image data is developed, the image data can be binarized or multi-valued by area gradation processing (dither processing in this example) and the phase can be controlled.

For example, when image data of 8-bit gradation is developed into binary data by binarizing the image data of 8-bit gradation by dither processing, a dither pattern as shown in FIG. (Reference matrix).

This dither pattern is 8 × 8 in this example.
However, since the image data to be developed as an image is a very large area than the pattern, for example, as shown in FIG. Comparing the density data value of the pixel with the corresponding threshold value of the dither pattern,
If it is larger than the threshold, it is determined that there is a dot, and the data is stored. If it is equal to or smaller than the threshold, it is determined that there is no dot (white), and the data is stored.

Further, the density values 20/255, 60/2 of the same area as in FIG. 14 are obtained by the dither pattern shown in FIG.
When dithering each data of 55, 120/255,
As shown in FIG. 15, FIG. 16, and FIG. 17, since the size of the aggregated dots (shown by oblique lines) increases as the density increases, the dots gradually increase. It is configured to get fat.

When developing binary image data as multi-valued data, a multi-valued dither pattern is used. However, three types of patterns similar to the dither pattern shown in FIG. The image data to be developed is compared with each of the three types of dither patterns to determine a multi-valued (2-bit) value. At this time, for example, in a normal multi-valued dither (four-valued dither in this example) pattern as shown in FIG. 18, one less dither pattern than the number of gradations to be expressed is prepared, and each dither pattern is prepared. Perform a comparison of magnitude.

However, comparing the threshold values of the same coordinates in each dither pattern shown in FIGS. 18 (a), (b) and (c),
In the dither pattern of (a), a large value is always arranged at any coordinate, and in the dither pattern of (c), a small value is always arranged at any coordinate.

However, in the multi-valued dither pattern used in this embodiment, for example, as shown in FIG. 19, the dither pattern of (a) is different from the dither patterns of (b) and (c) at any coordinates. Although the value is always large, comparing the threshold values of the same coordinates in each of the dither patterns (b) and (c), it is not always the case that the large value is arranged. The right side (for example, coordinates (C, c)) of the dot has a larger value for the dither pattern of (c), and the left side (for example, coordinates (F, c)) of the dot has a larger value for the dither pattern of (b). Is larger.

As such a dither pattern, (b)
If it is larger than the dither pattern of (a) and smaller than the dither pattern of (a), the values of D1 and D0 are set to "0" and "1", respectively, and are larger than the dither pattern of (c) and (a). If the dither pattern is smaller than the dither pattern, the values of D1 and D0 are set to "1" and "0",
When increasing the resolution, a pulse as shown in FIG. 8 can be generated.

When developing binary image data as multi-valued data by using only one dither pattern, for example, a dither pattern as shown in FIG. Make a comparison. However,
In this embodiment, the image is virtually developed at the resolution at which printing is finally performed by the printer engine 10.

Further, in this example, two adjacent pixels are put together, and when the value of the image data is larger than the threshold value of both pixels, the values of the 2-bit data D1 and D0 are set to “1”, respectively. Set to “1” and “0”, “1” when only the left pixel has a larger image data value than the threshold value
When only the right pixel has a value of the image data larger than the threshold value, it is set to “1” or “0”. When both pixels have a smaller value of the image data than the threshold value, it is set to “0”. ,
Set to “0”.

As a result, when thickening the dots, the dots can be gradually increased without being isolated.
The gradation expression gradually increases, the image quality can be improved, and the reference matrix is made horizontally long in the main scanning direction as shown in FIG. By increasing the number of pixels in the direction, the gradation can be expressed at the same area ratio in both the main scanning direction and the sub-scanning direction, even when the resolution is increased.

The present invention can be applied to a printer controller which can be used for various image forming apparatuses such as a high-speed color laser printer, a digital color copying machine, a color ink jet printer, and the like.

[0115]

As described above, claims 1 to 6 are described.
According to the printer control apparatus of the invention, when printing the image data sent from the host computer by the printer engine for binary output, the image data is developed as multi-valued data, Since the resolution is increased (to convert the multi-valued image data stored in the image storage means to a resolution higher than the resolution at the time of image development) to improve the operability, the data is output to the printer engine as binary data. The print quality by the output printer engine can be improved.

When the resolution of the image data is increased, the image development of the image data is performed at a low resolution without increasing the number of pixels, and the image storage means can be managed by the gradation of the pixel. Can be simplified, the processing can be speeded up, and the time required for printing can be reduced. According to each of the second to sixth aspects of the present invention,
In addition to the above, the following effects can be obtained.

According to the second aspect of the invention, when increasing the resolution of the multi-valued image data stored in the image storage means, the phase of the binary image data to be output is controlled based on the image data. Thus, when the image data is output to the printer engine and printed, the isolated dots can be eliminated and the output gradation can be improved, so that the print quality can be further improved.

According to the third aspect of the present invention, when binary image data is output to the printer engine, its edge is detected and the detected edge is corrected (smoothed without jaggedness). Thereby, the print quality at the edge of image data such as text data can be improved.

According to the fourth aspect of the present invention, when image data such as text data is developed as multi-valued data, the phase (high resolution) when the image data is output as binary data from the conversion processing means is obtained. By correcting the edge portion in consideration of the phase at the time of printing, the print quality at the edge portion of image data such as text data can be improved with the same effect as the invention of the fifth aspect. .

According to the fifth aspect of the present invention, when the resolution conversion of the multi-valued image data stored in the image storage means is performed, the resolution conversion of each pixel data in the sub-scanning direction is also performed. By temporarily storing the obtained binary image data for one line or a plurality of lines in the line buffer and outputting the data, the data transfer at the time of printing by the printer engine can be efficiently performed. Therefore, the bus traffic can be reduced, and the processing speed can be further increased.

According to the invention of claim 6, since binary image data from the conversion processing means or multi-valued image data from the image storage means can be selected and output to the printer engine, the multi-valued output printer can be selected. Engines can also be used. That is, since the same printer controller can be connected to various printer engines, the cost of the entire system can be reduced.

According to the printer control apparatus of the seventh and eighth aspects of the present invention, when multi-valued or binary image data sent from the host computer is printed by the printer engine for binary output, the image is output. The image is developed as binary or multi-level data (at this time, the multi-level or binary image data from the host computer is binarized or multi-leveled by area gradation processing such as dither processing or error diffusion processing). Control the phase), increase the resolution to improve the gradation, and output it as binary data to the printer engine (the phase of the binary image data to be output based on the image data developed at this time) ), So that the output gradation can be greatly improved, and the print quality of the binary output printer engine can be greatly improved.

When the resolution of the image data is increased, the image data of the image data is developed at a low resolution without increasing the number of pixels, and the image storage means can be managed by the gradation of the pixel. Can be simplified, the processing can be speeded up, and the time required for printing can be reduced.

Further, according to the invention of claim 8, as a reference matrix used when the multi-valued or binary image data is binarized or multi-valued by area gradation processing by the expansion processing means, By using a pixel whose number of pixels in the main scanning direction is larger than the number of pixels in the sub-scanning direction, if image data is output to a printer engine and printed, if the resolution is to be increased only in the main scanning direction, the As a result, a configuration in which the reference matrix can be treated as a square can be used, and more accurate gradation expression can be performed, thereby improving print quality.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a printer system using a printer controller as a printer control device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an image developing process by a CPU 4 of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration example of a printer system using a printer controller as a printer control device according to a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a printer system using a printer controller as a printer control device according to a third embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration example of a printer system using a printer controller as a printer control device according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration example of a printer system using a printer controller as a printer control device according to a fifth embodiment of the present invention.

FIG. 7 shows 600 DPI, one bit gradation per pixel (2
FIG. 7 is a diagram illustrating pulses (binary image data) output to the printer engine 10 of FIG. 6 when printing is performed with (value).

8 is a diagram for explaining a resolution conversion process according to the present invention by the gradation decoder 21 of FIG. 6;

FIG. 9 is a diagram for explaining phase control according to the present invention.

FIG. 10 is another diagram for explaining the phase control according to the present invention.

FIG. 11 is still another diagram for explaining the phase control according to the present invention.

FIG. 12 is a diagram for explaining edge correction processing according to the present invention by the edge correction unit 31 or the CPU 4 in FIG. 6;

13 is a diagram showing an example of a dither pattern (reference matrix) used for dither processing (area gradation processing) performed by the CPU 4 on image data sent from the host computer 1 of FIG.

14 is a diagram for explaining a dither process performed by a CPU 4 on image data sent from the host computer 1 in FIG. 6;

15 is a diagram illustrating an example of an image obtained by dither processing performed by a CPU 4 on multi-valued image data sent from the host computer 1 in FIG. 6;

FIG. 16 is a diagram showing another example.

FIG. 17 is a diagram showing still another example.

FIG. 18 shows a multi-valued (4) used for normal multi-valued dither processing.
FIG. 9 is a diagram illustrating an example of a (value) dither pattern.

19 is a diagram showing an example of a multi-value dither pattern used for multi-value dither processing performed by the CPU 4 on image data sent from the host computer 1 of FIG.

FIG. 20 is a diagram showing an example of another multilevel dither pattern.

FIG. 21 is a block diagram illustrating a configuration example of a printer system using a conventional printer controller.

FIG. 22 is a diagram for describing a video I / F of a data through system.

FIG. 23 is a diagram for describing a multi-level video I / F.

FIG. 24 is another diagram for describing a multi-level video I / F.

[Explanation of symbols]

 1: Host computer 1a: Printer driver 3: Host I / F 4: CPU 5: ROM 6: RAM 7: Video DMA controller 8: Engine I / F 9: System bus 10: Printer engine 20, 30, 40, 50, 60: Printer controller 21: Gradation decoder 31: Edge correction unit 41: Line buffer 51: Selector

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Claims (8)

[Claims] 1. A printer control device that develops image data created on a host computer and sends it to a printer engine to execute printing, wherein the printer engine prints image data sent from the host computer. Expansion processing means for expanding the image as multi-valued data so as to enable the image processing; image storage means for temporarily storing multi-valued image data expanded by the means; A printer control device for converting data to a resolution higher than the resolution at the time of image development and outputting the binary data to the printer engine. 2. The image processing apparatus according to claim 1, wherein the conversion processing unit outputs the image data based on multi-valued image data stored in the image storage unit.
2. The printer control device according to claim 1, further comprising means for controlling a phase of the value image data. 3. The printer control device according to claim 1, further comprising an edge correction unit that detects an edge of the binary image data output from the conversion processing unit and corrects the detected edge. A printer control device, comprising: 4. The image processing apparatus according to claim 1, wherein the developing unit expands the image data sent from the host computer into multi-valued data so that the image data can be printed by the printer engine. 3. The printer control device according to claim 1, further comprising means for correcting an edge portion in consideration of a phase when the data is output as binary data from the means. 5. The printer control device according to claim 1, further comprising a line buffer for temporarily storing one line or a plurality of lines of image data to be processed by the conversion processing unit. A printer control device characterized by the above-mentioned. 6. The printer control device according to claim 1, wherein binary image data from the conversion processing unit or multi-valued image data from the image storage unit is selected. A printer control device comprising a data selection means for outputting to the printer engine. 7. A printer control device for expanding image data created on a host computer, sending the image data to a printer engine, and executing printing, wherein the multi-valued or binary image data sent from the host computer is Expansion processing means for developing an image as binary data or multi-value data so that printing can be performed by the printer engine; and image storage for temporarily storing binary or multi-value image data developed by the means. Means for converting binary or multi-valued image data stored in the means to a resolution higher than the resolution at the time of image development, and outputting the binary data to the printer engine; Means for printing multi-valued or binary image data sent from the host computer by the printer engine When the image is developed as binary data or multi-value data, the multi-value or binary image data is binarized or multi-valued by area gradation processing and the phase is controlled, and the conversion is performed. The processing means stores the 2 stored in the image storage means.
A printer control device comprising means for controlling the phase of binary image data to be output based on value or multi-value image data. 8. A reference matrix according to claim 7, wherein said expansion processing means binarizes or binarizes said multi-valued or binary image data by area gradation processing. Is a printer control device, wherein the number of pixels in the main scanning direction is larger than the number of pixels in the sub-scanning direction.