JP2007228067A - Image forming system, terminal equipment, and image forming unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming system, etc. enabling reduction of an image data amount to be transmitted, while restraining reduction of the processing capacity. <P>SOLUTION: A PC 80 compresses a K-color image data by a first compression system appropriate for compressing character data, and compresses a CMY-color image data by a second compression system appropriate for compressing graphic images. The PC 80 then forwards the compressed image data to a printer 1. Meanwhile, upon receiving the compressed image data from the PC 80, the printer 1 decompresses the image data compressed by a Mode 9 compression system and the image data compressed by a dither compression system. Thereafter, the printer 1 performs image forming by superimposing the decompressed image data of different colors in an image forming section 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming system, a terminal device, and an image forming apparatus.

When printing an image, image data to be printed is transmitted from a terminal device such as a PC to an image forming apparatus such as a printer.
Here, the image data transmitted to the image forming apparatus preferably has a small amount of data from the viewpoint of transmission efficiency, storage capacity on the image forming apparatus side, and the like. The processed image data is transmitted to the image forming apparatus. When the image forming apparatus receives the compressed image data, the image data is decompressed (decompressed), restored to the original data, and then printed.

Here, it is desirable that the amount of data in the compression is smaller if there is no difference in image quality. Therefore, in order to reduce the amount of data, for example, as shown in Patent Document 1, the image data is divided into a plurality of areas and compressed by different compression methods for each of the areas. A configuration was considered in which the amount of data was reduced as compared with the compression method.
Japanese Patent Laid-Open No. 10-187411

  However, when the image data is divided into a plurality of areas and compressed with different compression methods for each area, the processing for dividing the image data and the determination of the compression method performed for each divided data are performed. Therefore, a large load is applied to the terminal device. In addition, the image forming apparatus also requires processing such as decompression of compressed data for each divided data and restoration of divided areas, which increases the load and decreases the processing capability of the image forming system. There was a problem.

  The present invention has been completed based on the above circumstances, and provides an image forming system and the like that can reduce the amount of image data to be transmitted while suppressing a decrease in processing capability. For the purpose.

  As means for achieving the above object, the invention of claim 1 is an image comprising: a terminal device that transmits image data; and an image forming device that forms an image based on the image data received from the terminal device. In the forming system, the terminal device includes: a first compression unit that compresses image data of one or a plurality of colors among a plurality of color image data constituting the image by a first compression method; Second compression means for compressing image data of a color different from the color of the image data compressed by the first compression method among a plurality of color image data constituting the image data by the second compression method; and the compressed image Sending means for sending data, wherein the image forming apparatus is adapted to receive the compressed image data sent from the sending means of the terminal device and to the first compression method. First decompression means for decompressing the compressed image data, second decompression means for decompressing the image data compressed by the second compression method, and superimposing the decompressed image data of different colors to form an image. And an image forming means to perform.

  According to a second aspect of the present invention, in the first aspect, the color of the image data compressed by the first compression method is black, and the first compression method is more character than the second compression method. It is characterized by a high data compression rate.

  According to a third aspect of the present invention, in the first aspect, the color of the image data compressed by the second compression method is a color other than black, and the second compression method is the first compression method. The feature is that the compression rate of the graphic image is higher than that.

  According to a fourth aspect of the present invention, in the first aspect, the color of the image data compressed by the first compression method is black, and the first compression method is more character than the second compression method. While the data compression rate is high, the color of the image data compressed by the second compression method is a color other than black, and the second compression method has a graphic image compression rate higher than that of the first compression method. It is characterized by high places.

  According to a fifth aspect of the present invention, in the first aspect, the colors of the image data compressed by the first compression method include black and yellow, and the first compression method is the first compression method. The compression rate of the character data is higher than that of the second compression method, and the color of the image data compressed by the second compression method is a color other than the black and yellow, and the second compression method is the first compression method. It is characterized in that the compression rate of graphic images is higher than that of the system.

  According to a sixth aspect of the present invention, in the first aspect, the color of the image data compressed by the first compression method is black, and the first compression method is more character than the second compression method. While the data compression rate is high, the color of the image data compressed by the second compression method is a color other than black, and the second compression method has a graphic image compression rate higher than that of the first compression method. The color of the image data compressed by the high first compression mode and the first compression method includes black and yellow, and the first compression method has a character data compression rate higher than that of the second compression method. The color of the image data compressed by the second compression method is a color other than the black and yellow, and the second compression method has a higher compression rate of the graphic image than the first compression method. Second compression mode Characterized in place with a switching means for switching, when.

  The invention of claim 7 is an image forming system comprising: a terminal device that transmits image data; and an image forming device that forms an image based on the image data received from the terminal device, the terminal device comprising: When the image data is composed of a plurality of colors including black, the black image data is compressed by the first compression method having a high compression rate of the character data, and the image data other than the black is converted to the first data. On the other hand, when the image data is composed only of black while being compressed by the second compression method in which the compression rate of the graphic image is higher than that of the one compression method, the compression means for compressing by the second compression method, and the compressed image Sending means for sending data, wherein the image forming apparatus receives the image data sent from the sending means of the terminal device, and the first pressure. A first decompression unit that decompresses image data compressed by the method, a second decompression unit that decompresses image data compressed by the second compression method, and an image obtained by superimposing the decompressed image data of different colors. And image forming means for performing the formation.

  According to an eighth aspect of the present invention, there is provided a terminal device for sending image data of an image to an image forming apparatus, wherein the image data of one or more colors among the image data of a plurality of colors constituting the image is First compression means for compressing by one compression method, and second compression of image data of a color different from the color of the image data compressed by the first compression means among image data of a plurality of colors constituting the image The image processing apparatus includes a second compression unit that compresses the image by a method and a sending unit that sends the compressed image data to the image forming apparatus.

  According to a ninth aspect of the present invention, there is provided an image forming apparatus for forming an image based on image data received from a terminal device, the image data compressed by the first compression method from the terminal device, and compressed by the first compression method. Receiving means for receiving image data of a color different from the image data to be compressed and compressed by the second compression method, and first decompression means for decompressing the image data compressed by the first compression method And a second decompressing unit that decompresses the image data compressed by the second compression method, and an image forming unit that forms an image by superimposing the decompressed image data of different colors. Have

<Invention of Claim 1>
According to this configuration, the image data of a plurality of colors constituting the image is compressed by the first compression method for the image data of one or a plurality of colors, and the image data compressed by the first compression method. Image data of a color different from the color is compressed by the second compression method. Then, the compressed image data is sent from the terminal device to the image forming apparatus side.
Therefore, for example, if black tends to be used for printing characters, a compression method that exhibits a high compression rate for character data is adopted, so that the black image data is more compressed. The amount of data can be reduced. On the other hand, for example, if a color other than black (cyan, magenta, etc.) is likely to be used for printing other than characters, a compression method that exhibits a high compression rate for non-characters (graphics, etc.) is employed. This makes it possible to reduce the amount of compressed image data for colors other than black.
In this way, by reducing the compression method according to the color of the image data, it is possible to reduce the amount of image data to be transmitted while suppressing a decrease in processing capacity due to the load on the terminal device or the image forming apparatus. Is possible.

<Invention of Claim 2>
In general, for images made up of character data (for example, data in text format), black tends to be used. Therefore, according to the present configuration, in such a case, the compression rate of the black image data is increased, so that it is possible to reduce the data amount of the compressed image data.

<Invention of Claim 3>
In general, graphics images tend to use colors other than black. Therefore, according to the present configuration, in such a case, the compression rate of the image data of colors other than black becomes high, so that the data amount can be further reduced.

<Invention of Claim 4>
In general, black tends to be used for images made up of character data (for example, text format data), and colors other than black are likely to be used for graphic image data. Therefore, according to the present configuration, in such a case, the data amount can be further reduced.

<Invention of Claim 5>
According to this configuration, in general, yellow that has little influence on the image is compressed by the first compression method, thereby reducing the concentration of load on the second compression unit as compared with the configuration of claim 4. Can do.

<Invention of Claim 6>
According to this configuration, the switching unit can switch between the first compression mode and the second compression mode according to the processing capability of the image forming apparatus. Problems with the image forming system that may be caused by a load can be suppressed.

<Invention of Claim 7>
In the case of an image composed of a plurality of colors including black, so-called color printing, black is generally used for characters. Therefore, in such a case, for black, image data is compressed by a compression method that exhibits a high compression rate for character data, and for colors other than black, image data is compressed by a compression method that has a high compression rate for graphic images. It becomes possible to reduce the amount of data. On the other hand, in the case of an image consisting only of black, so-called monochrome printing, it is generally considered that there is a relatively high possibility that an image other than characters will be printed even if it is black compared to color printing. Therefore, in such a case, it is possible to reduce the data amount of the image data by compressing the image data by a compression method with a high compression rate of the graphic image.

<Invention of Claim 8>
According to this configuration, since the image data compressed by the compression method that reduces the data amount according to the color of the image data can be sent to the image forming apparatus side, the data amount of the transmitted image data is reduced. And the load on the image forming apparatus can be reduced.

<Invention of Claim 9>
According to this configuration, an image can be formed based on image data received with a smaller amount of data, so that the load on the image forming apparatus can be reduced.

<Embodiment 1>
Embodiment 1 of a printing system of the present invention (an example of an “image forming system” of the present invention) will be described with reference to FIGS. FIG. 1 is a block diagram illustrating a configuration of a printing system.
(Configuration of printing system)
As shown in FIG. 1, the printing system includes, for example, a personal computer (hereinafter referred to as “PC80”, an example of the “terminal device” of the present invention) and a laser printer (hereinafter referred to as “printer 1”). An example of an “image forming apparatus” is connected via a LAN cable (communication means), for example. When the printer 1 receives image data (print data) sent from the PC 80 in response to a print request from the user, the printer 1 forms an image based on the image data.

1. As shown in FIG. 1, the personal computer PC 80 includes an operation unit 81 that receives an input operation from the outside (for example, an input unit such as a keyboard or a mouse), a display unit 82 including a display that displays an image, a ROM 83, The RAM 84, the CPU 85, a hard disk (hereinafter referred to as “HDD 86”), and a network interface (hereinafter referred to as “network I / F 87”, which corresponds to “sending means” of the present invention).

  The HDD 86 stores an application 53 for creating information to be printed, a printer driver 54 of the printer 1 that performs printing (see FIG. 3), and the CPU 85 executes an application based on a command from the operation unit 81. 53 and the printer driver 54 are read from the HDD 86 and operated.

  When the CPU 85 receives a print request from the operation unit 81 by a user input operation, the image data (print data) created by the application 53 is delivered to the printer driver 54, where it is converted (developd) into, for example, PDL data. Next, data transmission is executed via the network I / F 87.

2. Laser Printer (1) Overall Configuration FIG. 2 is a side sectional view of the laser printer.
This printer 1 is a side-by-side tandem color laser printer in which a plurality of process units 17 are arranged in parallel in the horizontal direction, and feeds a sheet 3 as a recording medium into a main body casing 2. A sheet feeding unit 4 for forming an image, an image forming unit 5 for forming an image on the fed sheet 3, and a sheet discharge unit 6 for discharging the sheet 3 on which the image is formed.

  The main casing 2 has a box-like shape that is substantially rectangular in a side view with the upper side opened, and a top cover 7 is provided on the upper side. The top cover 7 is rotatably supported via a cover shaft 8 provided on the rear side of the main casing 2 (in the following description, the left side in FIG. 2 is the rear side and the right side is the front side). The main casing 2 can be opened and closed.

  The paper feed unit 4 includes a paper tray 9 provided at the bottom of the main body casing 2, a pickup roller 10 and a paper feed roller 11 as supply means provided above the front side of the paper tray 9, and a front side of the paper feed roller 11. A sheet feeding side U-shaped path 12 provided above, a pair of conveying rollers 13 and a pair of registration rollers 14 provided in the middle of the sheet feeding side U-shaped path 12 are provided.

  The paper tray 9 can be pulled out, and the paper 3 is stacked in the paper tray 9, and the paper 3 at the top is first picked up by the pickup roller 10 and forward. Then, the paper is fed to the U-shaped path 12 by the paper feed roller 11.

  The feed-side U-shaped path 12 has an upstream end adjacent to the feed roller 11 at the lower side so that the paper 3 is fed forward, and a downstream end at the upper side, which will be described later. It is formed as a substantially U-shaped sheet 3 conveying path that is adjacent to the conveying belt 38 so that the sheet 3 is discharged rearward.

  Then, the sheet 3 fed forward to the upstream end of the sheet feeding side U-shaped path 12 is conveyed by the conveying roller 13 in the sheet feeding side U-shaped path 12 and the conveying direction is reversed. After registration by the registration roller 14, the paper is discharged backward by the registration roller 14.

The image forming unit 5 includes a process unit 17, a transfer unit 18, and a fixing unit 19.
The process unit 17 is provided for each color of a plurality of colors of toner. That is, the process unit 17 includes four units, that is, a yellow process unit 17Y, a magenta process unit 17M, a cyan process unit 17C, and a black process unit 17K. The process units 17 are sequentially arranged in parallel so as to be overlapped in the horizontal direction at intervals from the front to the rear.

  Each process unit 17 includes a scanner unit 20 as an exposure apparatus fixedly disposed in each process unit 17, and a process cartridge 21 that is detachably attached to each process unit 17.

  The scanner unit 20 includes a laser light emitting unit (not shown), a polygon mirror 22, a lens 23, and a reflecting mirror 24. In the scanner unit 20, the laser light based on the image data emitted from the laser light emitting unit is reflected by the polygon mirror 22, passes through the lens 23, is reflected by the reflecting mirror 24, and is directed to the photosensitive drum 25 described later. Are emitted.

  Each process cartridge 21 is inclined in the front-rear direction and the vertical direction (the thickness direction of the paper 3), that is, in the direction inclined from the upper side to the lower side toward the rear side (the direction in which the upper side is inclined forward). A photosensitive drum 25 as a photosensitive member, a scorotron charger 26, a developing roller 27, and a supply roller 28 are provided.

  The scorotron charger 26 is a positively charged scorotron charger that includes a wire and a grid, and generates corona discharge. Has been.

  The developing roller 27 is disposed above the photosensitive drum 25 so as to face the photosensitive drum 25 and is in pressure contact with the photosensitive drum 25.

  The supply roller 28 is disposed above the developing roller 27 so as to face the developing roller 27 and is in pressure contact with the developing roller 27.

  The upper part of the process cartridge 21 is formed as a toner storage chamber 35 for storing toner, and stores toner for each color. That is, in the toner storage chamber 35, for each process unit 17, yellow for the yellow process unit 17Y, magenta for the magenta process unit 17M, cyan for the cyan process unit 17C, and black for the black process unit 17K. A positively chargeable non-magnetic one-component polymerized toner having the following characteristics is accommodated.

  In each process unit 17, during the image forming operation, the toner for each color stored in each toner storage chamber 35 is supplied to the supply roller 28, and is supplied to the developing roller 27 by the rotation of the supply roller 28. . At this time, the toner is positively frictionally charged between the supply roller 28 and the developing roller 27 to which a developing bias is applied.

  On the other hand, the scorotron charger 26 generates a corona discharge by applying a charging bias to uniformly positively charge the surface of the photosensitive drum 25. The surface of the photosensitive drum 25 is uniformly positively charged by the scorotron charger 26 as the photosensitive drum 25 rotates, and then exposed by high-speed scanning of laser light from the scanner unit 20 to form on the paper 3. An electrostatic latent image corresponding to the image to be formed is formed.

  When the photosensitive drum 25 is further rotated, the toner held on the surface of the developing roller 27 and positively charged toner comes into contact with the photosensitive drum 25 by the rotation of the developing roller 27 so as to face the photosensitive drum 25. The electrostatic latent image formed on the surface, that is, the surface of the photosensitive drum 25 that is uniformly positively charged, is supplied to an exposed portion that is exposed to laser light and has a lowered potential. As a result, the electrostatic latent image on the photosensitive drum 25 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 25 for each color.

  The transfer unit 18 is disposed in the main casing 2 above the paper feed unit 4 and below the process unit 17 along the front-rear direction, and includes a driving roller 36, a driven roller 37, a conveyance belt 38, and a transfer roller 39. , And a belt cleaning device 40.

  The drive roller 36 is disposed at a low height so as not to overlap the photosensitive drum 25 in the horizontal direction behind the photosensitive drum 25 of the process cartridge 21 attached to the black process unit 17K.

  The driven roller 37 is disposed in front of the photosensitive drum 25 of the process cartridge 21 mounted on the yellow process portion 17Y and above the driving roller 36.

  The conveyor belt 38 is an endless belt, and is formed of a resin such as conductive polycarbonate or polyimide in which conductive particles such as carbon are dispersed. The conveyor belt 38 is wound between a driving roller 36 and a driven roller 37.

  The transfer roller 39 is disposed so as to face the photosensitive drum 25 of each process unit 17 and the conveyor belt 38 in the conveyor belt 38 wound between the driving roller 36 and the driven roller 37. A transfer bias is applied to the transfer roller 39. .

  Further, the belt cleaning device 40 is disposed in a relatively large space formed below the conveying belt 38 and closer to the driven roller 37 side. The belt cleaning device 40 includes a cleaning box 46 and a cleaning roller 47. A backup roller 110 facing the cleaning roller 47 is provided in the transport belt 38.

  The fixing unit 19 is disposed behind the transfer unit 18. The fixing unit 19 includes a heating roller 48 and a pressure roller 49.

The heating roller 48 is made of a metal base tube having a release layer formed on the surface thereof, and a halogen lamp is provided along the axial direction thereof. Then, the surface of the heating roller 48 is heated to the fixing temperature by the halogen lamp. The pressure roller 49 is provided so as to press the heating roller 48.
Then, the color image transferred onto the paper 3 is then conveyed to the fixing unit 19 and thermally fixed while the paper 3 passes between the heating roller 48 and the pressure roller 49.

The paper discharge unit 6 includes a paper discharge side U-shaped path 50, a paper discharge roller 51, and a paper discharge tray 52.
The discharge-side U-shaped path 50 has an upstream end adjacent to the fixing unit 19 at the lower side and a downstream end at the upper side so that the sheet 3 is fed rearward. Is formed as a substantially U-shaped paper 3 conveyance path so that the paper 3 is discharged forward.

The paper discharge roller 51 is provided as a pair of rollers at the downstream end of the paper discharge side U-shaped path 50.
The discharge tray 52 is formed on the upper surface of the main casing 2 as an inclined wall that is inclined downward from the front to the rear.

  The sheet conveyed from the fixing unit 19 is fed rearward to the upstream end of the discharge side U-shaped path 50, and the conveyance direction is reversed in the discharge side U-shaped path 50. The paper is ejected forward onto a paper ejection tray 52 by a paper ejection roller 51.

(2) Electrical Configuration Next, the electrical configuration of the laser printer will be described.
As shown in FIG. 1, the printer 1 includes a control device 90 that controls each component by a control unit 95 including a CPU 91, a ROM 92, a RAM 93, and an ASIC 66 (Application Specific Integrated Circuit). Furthermore, in a form electrically connected to the control unit 95, the main motor 96, the scanner motor 97, the image forming unit 5, an operation unit 98 including an input panel, a display unit 99 including various lamps, various sensors, etc. The detection unit 100 and the like are provided, and a control system is configured by these.

  The ROM 92 and RAM 93 are connected to the CPU 91, and the CPU 91 controls each component via the control unit 95 while storing the processing results in the RAM 93 according to the processing procedure stored in the ROM 92.

  The main motor 96 is a motor that rotates the above-described conveyance belt 38 and the like. The scanner motor 97 is a motor that rotates the polygon mirror 22 in the scanner unit 20.

  The CPU 91 performs drive control of the main motor 96 and the scanner motor 97 based on a program stored in the ROM 92 in advance.

  The control unit 95 controls the image forming unit 5 in accordance with a command from the CPU 91. Specifically, exposure control for exposing the surface of the photosensitive drum 25 is performed by each unit constituting the scanner unit 20, and transfer bias control for transferring toner onto the paper 3 is performed.

Further, the control device 90 is provided with a network I / F 94 (corresponding to “reception means” of the present invention) for connecting to an external device such as the PC 80.
The detection unit 100 includes various sensors, and these sensors are electrically connected to the control unit 95.

3. Configuration for Reducing Image Data Amount Transmitted from PC to Printer FIG. 3 is a diagram for explaining a configuration for reducing the amount of image data.
(1) Configuration of PC The HDD 86 of the PC 80 stores various applications 53, a printer driver 54, an OS (Operating System) (not shown), and the like. The application 53 and the printer driver 54 are installed in the HDD 86 using, for example, a storage medium such as a CD-ROM (not shown) or a program sent from a predetermined server.

  The application 53 is various application programs such as word processor software and image creation software, and is loaded into a predetermined area of the RAM 84 and executed by the CPU 85 when the process is executed. When the application 53 is executed, the user can create images such as characters and graphics using word processor software or the like.

  The printer driver 54 is loaded into a predetermined area of the RAM 84 and executed by the CPU 85, and includes a printer memory information acquisition unit 55, a drawing processing unit 56 that develops an image to be printed into bitmap data, and bitmap data. A compression processing unit 57 that performs compression processing (and dump processing) of the print data as four-color print data (PDL data), and a print data transfer unit 58 that transfers the compressed print data to the spooler 59. Configured.

  The printer memory information acquisition unit 55 acquires information related to an empty area in which print data is stored in a print data storage unit 65 of the printer 1 described later.

The drawing processing unit 56 creates bitmap data of an image for which a print command has been given.
The compression processing unit 57 includes a compression method determination unit 57A that determines a compression method for each color print data (color plane), a dither compression processing unit 57B (an example of the “second compression unit” of the present invention), and Mode 9 compression. And a processing unit 57C (an example of the “first compression unit” of the present invention).

  The compression method determination unit 57A is suitable for compression of character data (for example, text data) in order to reduce the amount of image data transmitted to the printer 1 side for each of the four color print data (four color planes). Perform compression by the first compression method (which can further reduce the amount of character data) or suitable for compression of graphic images (for example, landscape image data) (graphics compared to text data) It is determined whether to perform compression by the second compression method (which can further reduce the data amount of the image).

  As the first compression method, various compression methods suitable for character data compression can be used. In this embodiment, the run-length compression method and the previous line comparison compression method (the previous line comparison compression method is A method (hereinafter referred to as “Mode 9”) in which data of each plane row (data of one line in the width direction of the image) is compared with data of the previous row and compression is performed depending on whether the data is the same. The compression method will be described as the first compression method. As the second compression method, various compression methods suitable for compression of graphic images can be used. In this embodiment, a dither method is used, and a pixel data group (predetermined predetermined) is used. The section has a size corresponding to a cycle of data (dither matrix) indicating whether each pixel is equal to or greater than a predetermined threshold (hereinafter referred to as “dither compression system”). Will be described as the second compression method.

  Then, the compression method determination unit 57A determines which compression method to use depending on the color of the print data (plane).

  Specifically, as a combination of compression methods that differ depending on the color of the print data (plane), setting A and setting B are stored in the memory in advance, and the user selects one of the settings from a setting screen such as a driver. Can be done. Instead of the user determining the setting, any setting may be determined in advance at the initial setting (manufacturing time).

  Here, for setting A, black (hereinafter referred to as “K color”) print data (K plane) is subjected to Mode 9 compression processing using the Mode 9 compression method and cyan (hereinafter referred to as “C color”). ), Magenta color (hereinafter referred to as “M color”), yellow (hereinafter referred to as “Y color”) print data (CMY plane) is set (combined) to perform dither compression processing using a dither compression method. is there.

On the other hand, setting B performs Mode 9 compression processing using the Mode 9 compression method for KY color print data (KY plane), and dither using the dither compression method for CM color print data (CM plane). This is a setting (combination) for performing compression processing.
In the following description of the present embodiment, it is assumed that the setting A is selected (determined) as a combination of compression methods according to colors. Incidentally, when the setting B is selected (determined), in the following description, the Y color is subjected to the same processing as the K color.

  The spooler 59 temporarily stores print data when there are a plurality of print requests, and outputs the print data to the printer 1 in order. The print data output from the spooler 59 is a network. The data is sent to the printer 1 via the I / F 87.

(2) Printer Configuration The printer 1 includes a network I / F 94 that receives print data from the PC 80, a buffer 62 that temporarily stores the received print data, a PDL program software 63 that processes the print data, and an ASIC 66. (Application Specific Integrated Circuit), a control signal converting unit 67 that converts the decompressed print data into a control signal for controlling image formation, and an image forming unit 5 that forms an image of the print data. It is configured.

  The PDL program software 63 includes a dither decompression processing unit 64 (an example of the “second decompression unit” in the present invention) that performs decompression (decompression) processing of print data compressed by the dither compression method, and print data that accumulates print data. And an accumulation unit 65.

The print data accumulation unit 65 accumulates (stores) uncompressed print data decompressed by the dither decompression processing unit 64 and print data compressed by the Mode 9 compression method (Mode 9 compressed data). It has become.
In the present embodiment, the decompression by the dither decompression processing unit 64 is realized by software processing based on the PDL program software 63. Here, in order to perform the decompression by the dither decompression processing unit 64 without delaying the progress of image formation performed by the image forming unit 5, it is necessary to use a CPU that performs relatively high-speed processing, but such a CPU is expensive. This is undesirable from a cost standpoint.
Therefore, in this embodiment, in order to keep the cost relatively low, instead of using an expensive CPU, the print data decompressed in advance is stored in the print data storage unit 65 to some extent, so that the image formation progresses. The image can be output to the image forming unit 5 without delay. Therefore, depending accumulates much print data that is being decompressed and uncompressed (dithered compressed have image) beforehand, so that the changes significantly the capacity required for the print data storage unit 65.

  The ASIC 66 includes a Mode 9 decompression processing unit 66A (an example of the “first decompression unit” in the present invention) that performs decompression (decompression) processing of print data compressed by the Mode 9 compression method.

  The control signal converter 67 converts the print data decompressed by the Mode 9 decompression processing unit 66A and the dither decompression processing unit 64 into a control signal for controlling image formation.

  The control signal converted by the control signal conversion unit 67 is output to the image forming unit 5, and the image forming unit 5 is controlled according to the control signal, so that an image corresponding to the print data is formed. It has become.

4). Processing Performed When Printing by Printing System (1) Processing Performed by PC FIG. 4 is a flowchart showing processing performed by the PC 80.
As shown in FIG. 4, when the CPU 85 receives a print command from the application 53 in response to a user operation (S11), the CPU 85 loads the printer driver 54 from the HDD 86 to a predetermined area of the RAM 84 (S12).

  In step S13, the drawing processing unit 56 of the printer driver 54 creates (draws and develops) bitmap data (dot image data) of an image requested to be printed, and the bitmap data is stored in a drawing memory (not shown). ).

  Next, the compression processing unit 57 performs a process of converting the bitmap data into four color planes (print data) of CMYK (S14), and a data compression process is performed (S15).

<Data compression processing>
In the data compression process, as shown in FIG. 5, the compression method determining unit 57A determines whether or not each color plane is a K color plane (S21).

  When the compression method determination unit 57A determines that the plane is the K color plane ("Y" in S21), the compression method is determined to be the Mode 9 compression method, and the K color plane is compressed by the Mode 9 compression processing unit 57C to perform Mode 9 compression. It is compressed by the method (S22).

  If the compression method determination unit 57A determines that the plane is not a K color plane ("N" in S21), that is, if it is a CMY color plane, the dither compression method is determined and the CMY color plane is determined. Each is compressed by the dither compression method in the dither compression processing unit 57B (S23).

  4, the compressed print data (image data) of each color plane is transferred to the spooler 59 by the print data transfer unit 58, stored in the spooler 59, and then further spooler 59. Is transferred to the network I / F 87 (S17), and is output from the network I / F 87 to the printer 1 side.

(2) Processing Performed by Printer FIG. 6 is a flowchart showing processing performed by the printer 1.
As shown in FIG. 6, the print data output from the network I / F 87 of the PC 80 is stored in the input buffer 62 (S31), and then processed by the PDL program software 63 (S32).

<Processing by PDL program software>
In the processing by the PDL program software, as shown in FIG. 7, it is determined whether or not the received print data is data compressed by the dither compression method (S41).

When the received print data is data compressed by the dither compression method (“Y” in S41), the print data storage unit 65 secures a storage area for print data when uncompressed (S42).
Then, the dither decompression processing unit 64 performs decompression (decompression) processing of the print data compressed by the dither compression method (S43), the decompressed uncompressed data is accumulated in the print data accumulation unit 65 (S44), and the ASIC 66 Is output.

  On the other hand, if the received print data is not data compressed by the dither compression method (“N” in S41), that is, print data compressed by the Mode 9 compression method, the print data storage unit 65 stores the print data. A storage area for one page of the compressed print data is secured (S45).

Then, the print data compressed by the Mode 9 compression method is accumulated one page at a time in the print data accumulation unit 65 (S46), and sequentially output to the ASIC 66.
Next, processing by the ASIC 66 is performed.

<Processing by ASIC>
As shown in FIG. 8, the ASIC 66 first determines whether the received print data is data compressed by the Mode 9 compression method (S51).

When the received print data is data compressed by the Mode 9 compression method (“Y” in S51), the print data is decompressed (decompressed) by the Mode 9 decompression processing unit 66A (S52), and the control signal is converted. The data is output to the unit 67.
On the other hand, if the received print data is not data compressed by the Mode 9 compression method (“N” in S51), that is, if the print data is uncompressed print data, the print data is output to the control signal converter 67. To do.

Next, the control signal conversion unit 67 converts the print data into a control signal (analog signal) for controlling the image forming operation, and outputs (transfers) it to the image forming unit 5 (S34).
The image forming unit 5 controls the image forming operation of the process unit 17 for each color by the control signal, and the image for each color is superimposed and printed according to the conveyance of the paper (S35).

5). Advantages of the present embodiment (1) According to the present embodiment, the PC 80 (terminal device) causes the Mode 9 compression processing unit 57C (first compression means) to select the K color (if the setting A is selected (determined)). Black) print data (one or more color image data among a plurality of color image data constituting the image) is compressed by the Mode 9 compression method (first compression method), and the dither compression processing unit 57B (second The CMY color print data (image data of a color different from the K color) is compressed by the dither compression method (second compression method) by the compression means). Then, the print data (image data) compressed by the network I / F 87 (sending means) of the PC 80 is sent to the printer 1 (image forming apparatus).
On the other hand, when the printer 1 receives the compressed print data (image data) sent from the network I / F 87 of the PC 80 by the network I / F 94 (reception unit), the Mode 9 decompression processing unit 66A (first expansion unit). Print data compressed by the Mode 9 compression method (first compression method) is decompressed, and the print data compressed by the dither compression method (second compression method) is decompressed (expanded) by the dither decompression processing unit 64 (second decompression means). ) Then, image formation is performed by superimposing print data of different colors decompressed (expanded) by the image forming unit 5 (image forming means).

  In this way, by changing the compression method according to the color of the print data, the print data to be transmitted is suppressed while suppressing a decrease in processing capacity due to the load on the PC 80 (terminal device) or the printer 1 (image forming apparatus). It becomes possible to reduce the amount of data.

(2) According to the present embodiment, if setting A is selected, the color of the print data (image data) compressed by the Mode 9 compression method (first compression method) is K, and the Mode 9 compression The method (first compression method) has a higher compression rate of character data than the dither compression method (second compression method). Here, generally, an image made up of character data (for example, data in text format) tends to use K color. Accordingly, in such a case, the compression rate of the K-color print data is increased, so that the amount of print data (image data) to be compressed can be reduced.

(3) According to the present embodiment, if setting A is selected, the color of the print data (image data) compressed by the dither compression method (second compression method) is CMY color (a color other than K color). The dither compression method (second compression method) has a higher graphic image compression rate than the Mode 9 compression method (first compression method). Here, generally, for graphic images, CMY colors (colors other than K colors) tend to be used. Therefore, according to the present embodiment, in such a case, since the compression rate of print data (image data) of CMY colors (colors other than K color) is increased, the data amount can be further reduced.

(4) According to this embodiment, if setting B is selected, the colors of print data (image data) compressed by the Mode 9 compression method (first compression method) are K color and Y color (yellow). Thus, the Mode 9 compression method (first compression method) has a higher compression rate of character data than the dither compression method (second compression method). The color of the print data compressed by the dither compression method (second compression method) is a CM color (a color other than K and Y colors), and the dither compression method (second compression method) is Mode 9 compression. The compression rate of graphic images is higher than that of the method (first compression method). Here, in general, the Y color with a low usage rate (less influence on the image) is compressed by the Mode 9 compression method (first compression method), so that the dither compression processing unit 57B ( The load concentration on the second compression means can be reduced.

<Embodiment 2>
Next, a second embodiment (corresponding to the invention of claim 6) of the present invention will be described with reference to FIG.
In the first embodiment, the user selects one of two types of combinations (setting A or setting B) in advance for the combination of compression methods applied to each color plane. In the second embodiment, Any combination (setting A or setting B) is automatically determined according to the size of the empty area in the print data storage unit 65 of the printer 1. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The size of the free area (free memory size) of the print data storage unit 65 of the printer 1 is transmitted to the printer memory information acquisition unit 55 at predetermined time intervals (see the dotted line in FIG. 3).

  Then, as shown in FIG. 9, the CPU 85 of the PC 80 acquires the information of the free area given to the printer memory information acquisition unit 55 (S61), and the size of the free area (free memory size) of the print data storage unit 65. ) Is greater than or equal to M (byte) (S62). This M (byte) is a preset amount of information. For example, when the setting A is set, a free area in which uncompressed data of the CMY three-color planes can be stored in the print data storage unit 65. Is set to a size M that can be secured.

  If the size of the free area (free memory size) of the print data storage unit 65 is equal to or greater than M (byte) (“Y” in S62), a combination of compression methods applied to each color plane is set. Set to A (switch. S63).

  On the other hand, if the size of the free area (free memory size) of the print data storage unit 65 is not M (bytes) or more (“N” in S62), the combination of compression methods applied to each color plane is set B. (Switched to S64). Therefore, the CPU 85 is an example of the “switching unit” in the present invention.

(Effect of Embodiment 2)
When the print data that is decompressed by the dither decompression processing unit 64 and becomes uncompressed becomes large, a large burden is placed on the print data storage unit 65 that stores the print data.
Therefore, according to the second embodiment, when the storage capacity of the print data storage unit 65 is small (according to the processing capability of the image forming apparatus), the CPU 85 (switching unit) stores the print data in the print data storage unit 65. The setting A is switched from the setting A having a large amount of uncompressed print data to the setting B having a relatively small amount of uncompressed print data stored in the print data storage unit 65. Thereby, since the load concerning the print data storage part 65 can be suppressed, the malfunction of the printing system resulting from this load can be suppressed. In addition, it is possible to perform good image formation without using the print data storage unit 65 having a large storage capacity in advance or an expensive CPU for proceeding with image formation in accordance with the decompression of the print data.

<Embodiment 3>
Next, Embodiment 3 (corresponding to the invention of claim 7) of the present invention will be described with reference to FIG. The third embodiment will be described assuming that setting A is selected (determined) as a combination of compression methods according to colors.
In the third embodiment, the print data compression method is different depending on whether color printing or monochrome printing is performed.

As shown in FIG. 10, the CPU 85 of the PC 80 determines whether the image print request is color printing (S71).
When the CPU 85 determines that the request is for monochrome printing (“N” in S71), the dither compression processing unit 57B performs dither compression on the print data requested to be printed (S73).

  On the other hand, if the CPU 85 determines that the color print request is made (“Y” in S71), the print data of K color is subjected to Mode 9 compression by the Mode 9 compression processing unit 57C and other than K color (CMY color). For the print data, dither compression is performed by the dither compression processing unit 57B (S72).

(Effect of Embodiment 3)
When the PC 80 (terminal device) is color print data (image data composed of a plurality of colors including K color), the Mode 9 compression method (the first character data compression rate for the K color print data is high). The print data of CMY color (other than K color) is compressed by the dither compression method (second compression method). On the other hand, in the case of monochrome print data (print data consisting of only K color), compression is performed using a dither compression method (second compression method). Then, the compressed print data is sent to the printer 1 (image forming apparatus) by the network I / F 87 (sending means).

  Here, in the case of an image composed of a plurality of colors including K color, that is, so-called color printing, the K color is generally used for characters. Therefore, in such a case, the K color is compressed by a compression method showing a high compression rate for character data, and the colors other than the K color are compressed by a compression method having a high compression rate for graphic images. It becomes possible to reduce the amount of print data. On the other hand, in the case of an image consisting of only K color, so-called monochrome printing, it is generally considered that there is a relatively high possibility that an image other than characters will be printed even for K color compared to color printing. Therefore, in such a case, it is possible to reduce the data amount of the print data by compressing the print data by a compression method with a high compression rate of the graphic image.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not departing from the gist of the invention other than the following. Various modifications can be made.

  (1) In the above embodiment, the color using a compression method suitable for character data (text data) is K color (in the case of setting A) or KY color (in the case of setting B), but is not limited thereto. Absent. For example, if the user prints character data (text data) in another color, a compression method suitable for the character data (text data) may be used for the character color used by the user. Similarly, colors using a compression method suitable for printing graphic images are also set to CMY colors (in the case of setting A) or CM colors (in the case of setting B), but the user can print other colors for printing graphic images. If it is frequently used, a compression method suitable for the graphic image may be used for the color used by the user.

  (2) In the above embodiment, printing using four color toners (color planes) has been described. However, the present invention can also be applied to a printing system using toners other than four colors. For example, the present invention may be applied to a printing system using toner (color plane) of six colors (the above-mentioned four colors plus two colors of light cyan and light magenta).

1 is a block diagram illustrating an electrical configuration of a printing system according to a first embodiment. Side sectional view showing schematic configuration of laser printer The figure explaining the structure for reducing the data amount of an image Flow chart of processing performed on PC Flow chart of data compression processing Flow chart of processing performed in the printer Flow chart of processing by PDL program software Flow chart of processing by ASIC Flowchart of processing for automatically switching modes in the second embodiment Flowchart of processing for switching compression methods according to monochrome or color printing in the third embodiment

Explanation of symbols

1. Laser printer (image forming device)
5. Image forming unit (image forming means)
54 ... Printer driver 55 ... Printer memory information acquisition unit 56 ... Drawing processing unit 57B ... Dither compression processing unit (second compression means)
57C: Mode 9 compression processing unit (first compression means)
63 ... PDL program software 64 ... Dither decompression processing unit (second decompression means)
65: Print data storage unit 66A: Mode 9 decompression processing unit (first decompression unit)
80. Personal computer (terminal device)
85 ... CPU (switching means)

Claims (9)

An image forming system comprising: a terminal device that transmits image data; and an image forming device that forms an image based on the image data received from the terminal device,
The terminal device
A first compression means for compressing one or a plurality of color image data among a plurality of color image data constituting the image by a first compression method;
A second compression means for compressing, by a second compression method, image data of a color different from the color of the image data compressed by the first compression method among a plurality of color image data constituting the image;
Sending means for sending the compressed image data,
The image forming apparatus includes:
Receiving means for receiving the compressed image data sent from the sending means of the terminal device;
First decompression means for decompressing image data compressed by the first compression method;
Second decompression means for decompressing the image data compressed by the second compression method;
Image forming means for forming an image by superimposing the expanded image data of different colors; and
An image forming system comprising: The color of image data compressed by the first compression method is black, and the first compression method has a higher compression rate of character data than the second compression method. Image forming system. The color of image data compressed by the second compression method is a color other than black, and the second compression method has a higher compression rate of graphic images than the first compression method. 2. The image forming system according to 1. The color of the image data compressed by the first compression method is black, and the first compression method has a higher compression ratio of character data than the second compression method,
The color of image data compressed by the second compression method is a color other than black, and the second compression method has a higher compression rate of graphic images than the first compression method. 2. The image forming system according to 1. The color of the image data compressed by the first compression method includes black and yellow, and the first compression method has a higher compression ratio of character data than the second compression method,
The color of the image data compressed by the second compression method is a color other than the black and yellow, and the second compression method has a higher compression rate of the graphic image than the first compression method. The image forming system according to claim 1. The color of the image data compressed by the first compression method is black. The first compression method has a higher compression ratio of character data than the second compression method and is compressed by the second compression method. The color of the image data is a color other than black, and the second compression method includes a first compression mode in which the compression rate of the graphic image is higher than that of the first compression method;
The colors of the image data compressed by the first compression method include black and yellow. The first compression method has a higher compression rate of character data than the second compression method, and the second The color of the image data compressed by the compression method is a color other than the black and yellow, and the second compression method includes a second compression mode in which the compression rate of the graphic image is higher than that of the first compression method;
The image forming system according to claim 1, further comprising a switching unit that switches between the two. An image forming system comprising: a terminal device that transmits image data; and an image forming device that forms an image based on the image data received from the terminal device,
The terminal device
When the image data is composed of a plurality of colors including black, the black image data is compressed by the first compression method having a high compression rate of the character data, and the image data other than the black is converted to the first data. A compression unit that compresses a graphic image using a second compression method having a higher compression ratio than that of the first compression method, and compresses the image data only of black, using the second compression method;
Sending means for sending the compressed image data,
The image forming apparatus includes:
Receiving means for receiving the image data sent from the sending means of the terminal device;
First decompression means for decompressing image data compressed by the first compression method;
Second decompression means for decompressing the image data compressed by the second compression method;
And an image forming unit that forms an image by superimposing the expanded image data of different colors. A terminal device for sending image data of an image to an image forming apparatus,
Of the image data of a plurality of colors constituting the image, the image data of one or more colors is compressed by a first compression method;
A second compression means for compressing image data of a color different from the color of the image data compressed by the first compression means among a plurality of color image data constituting the image by a second compression method;
Sending means for sending the compressed image data to the image forming apparatus;
A terminal device comprising: An image forming apparatus for forming an image based on image data received from a terminal device,
Image data compressed by the first compression method and image data of a color different from the image data compressed by the first compression method and image data compressed by the second compression method are received from the terminal device Receiving means for
First decompression means for decompressing image data compressed by the first compression method;
Second decompression means for decompressing the image data compressed by the second compression method;
Image forming means for forming an image by superimposing the expanded image data of different colors; and
An image forming apparatus.

Images