JP2005212456A - Image forming apparatus and image formation supporting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a boundary part in touch with a character of a halftone part or a line drawing part from being blanked or changed in the color while the character or the line drawing part is kept in a clear state. <P>SOLUTION: A character/line drawing layer 100t of characters and line drawings, and a halftone layer 100i of a half tone are arranged adjacent to each other. In original data, a switching position (boundary position) from the character/line drawing layer 100t to the halftone layer 100i of each color toner layer which constitutes the character/line drawing layer 100t is the same (position B in the drawing) for a color K and a color YMC. It is judged here whether or not a toner concentration difference between the character/line drawing layer 100t and the halftone layer 100i is not smaller than a threshold n. In the case where the toner concentration difference becomes not smaller than the threshold n, the character/line drawing layer 100t at the toner layers of CMY is extended by m pixels to the halftone layer 100i side. In other words, the switching position is shifted by m pixels toward the halftone layer 100i side (position of B0). The toner layer of the color K is not extended and the switching position to the halftone layer 100i is maintained as it is at the position of B. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and an image forming support apparatus. For example, an image forming apparatus having a so-called printing function for forming an image on a recording medium, such as a color copying machine, a facsimile, or a printer, and data to the image forming apparatus. The present invention relates to an image forming support apparatus for outputting.

  In conventional printing (for example, offset printing), intermediate products such as paper printing (printing paper) such as photosetting, block printing, net negative, net positive, PS plate (printing plate) are generated, and these intermediate products are used as the original. Printing and bookbinding. In recent years, with the spread of DTP (DeskTop Publishing / Prepress), “direct printing” or “on-demand printing” for directly printing from DTP data is known. In DTP, printing data obtained by processing a page layout on a computer is formed on photographic paper or a plate-making film, and a printing plate is created and printed based on the printing data. In addition, CTP (Computer To Plate) that directly forms a printing plate with electronic data without generating an intermediate product is also attracting attention. As an apparatus that can be used for such a printing process, an image forming apparatus having a printing function such as a printer or a copying machine is known. Image forming apparatuses in recent years have been improved in color with improved image quality. For example, a color printer using an electrophotographic process (xerography) can form high-quality and high-speed images. In this image forming apparatus, print data can be output without receiving print data and generating a printing plate or the like.

  FIG. 8 is a schematic diagram of a conventional image forming system. As shown in FIG. 8A, the image forming system includes an image forming apparatus 11 and a DFE (Digital Front End Processor) apparatus that sends print data to the image forming apparatus 11 and gives a print instruction. ing. FIG. 8B shows a data flow.

  The DFE device has a drawing function and a printer controller (print control device) function. For example, the DFE device sequentially receives print data described in a page description language (PDL) from a client terminal, and the print data is rasterized. The image data is converted into an image (RIP processing; RIP processing), and the RIP processed image data and print control information (job ticket) such as the number of printed sheets and paper size are sent to the image forming apparatus 11, and the print engine of the image forming apparatus 11 And the paper conveyance system is controlled to cause the image forming apparatus 11 to execute the printing process. That is, the printing operation of the image forming apparatus 11 is controlled by a printer controller by the DFE apparatus. The print data includes four colors (YMCK) of three basic colors for color printing, ie, yellow (Y), cyan (C), and magenta (M), and black (K). Sent to.

  The image forming apparatus 11 records an image on printing paper using an electrophotographic process. The image output terminal (IOT) module 12 and a feed module (FM; Feeder Module) connected to the IOT module 12 are used. ) 15, a user interface device 18 for supporting the input of various data including an output module 17 and a touch panel. The IOT module 12 includes a toner supply unit 22 on which YMCK toner cartridges 24 are mounted, and an IOT core unit 20. The IOT core unit 20 has a so-called tandem configuration in which print engines (printing units) 30 having an optical scanning device, a photosensitive drum, and the like are arranged in a line for each color and in the belt rotation direction, and controls the print engine 30. An electric system control storage unit 39 for storing an electric circuit or the like is provided. In the IOT core unit 20, the toner image on the photosensitive drum is transferred to the intermediate transfer belt 43 (primary transfer), and then the toner image is transferred to the printing paper (secondary transfer). Multiple transcribed. The image (toner image) transferred onto the intermediate transfer belt 43 is transferred onto the printing paper conveyed from the feed module 15 at a predetermined timing, and the toner image is melted and fixed onto the paper by a fixing device (Fuser) 70. Is done. Thereafter, the paper is discharged out of the apparatus via the paper discharge processing device 72. Further, during double-sided printing, a sheet of paper that has already been printed on one side is temporarily held on a paper discharge tray (stacker) 74, pulled out from the paper discharge tray 74, reversed through a reverse conveyance path 49, and again IOT core unit 20 Passed to.

  When this system is used, in order to realize a demand for high-performance and high-speed image formation processing (print processing) (for example, color printing of 100 sheets to 200 sheets / minute or more), the image forming apparatus supports In addition, the printer controller (DFE device), which is a print control portion for the RIP processing and the image recording unit on the output side, needs to have high speed and high performance.

  However, the DFE device not only performs RIP processing on PDL data from the client terminal, but also rearranges pages according to the print job (rearrangement in ascending / descending order, determination of processing page order during double-sided printing, finisher correspondence positioning, etc. ), And additional processing such as data conversion (for example, gray balance and color misregistration calibration) in accordance with output-side processing characteristics such as a print engine and a fixing device. In order to execute the additional processing, advanced processing according to the characteristics of the image forming apparatus is required. Conventionally, in order to realize high speed and high performance while executing the processing, the DFE apparatus and the image forming apparatus are conventionally used. 11 and a dedicated and independent device configuration in which a dedicated communication protocol is used.

  However, it is necessary to prepare a dedicated device individually, which increases the cost of the entire system and increases versatility.

  Therefore, in recent years, an image formation support apparatus (back-end processor) having a printer controller function that performs control depending on the output side is provided between the DFE apparatus (front-end processor) and the image formation apparatus. A system has also been proposed in which when image data sent from a front-end processor is received, image data is sequentially sent to an image forming apparatus in accordance with processing characteristics on the output side, and printing processing is performed by controlling the image forming apparatus. As a result, when processing or recovery processing adapted to an output form based on a request from a client is performed, it is possible to cope with the processing regardless of the front-end processor.

  By the way, in the image forming apparatus using the above-described electrophotographic process, generally, a color original including a mixture of images and text, a layer of characters and line drawing parts (hereinafter referred to as character / line drawing layer) and background of the color original. And halftone layers (hereinafter referred to as halftone layers), such as areas and photographs, are defined, and resolution processing, gradation correction, etc. are performed so that optimum reproduction results can be obtained for the image signals of each layer. The image processing is performed, and printing is performed by switching the toner density in each of the character / line image layer and the halftone layer.

  However, in the portion of the output image where the low-density halftone layer and the high-density character / line image layer are adjacent to each other, the density of the boundary portion of the halftone layer in contact with the character / line image layer decreases. The color may change or white spots may occur.

  For example, as shown in FIG. 9A, a low density halftone layer toner image composed of (M + Y) from a character / line image layer toner image 90t formed of a high density black (K + C + M + Y). At the switching position to 90i (B in the figure), the toner density difference (toner pile height) of the high density character / line drawing layer and the toner density difference between the low density halftone layer (that is, the toner pile height difference). Will become bigger. As a result, a gap is formed between the transfer material and the photosensitive member, and the character / line image layer side end portion (A in the figure) of the halftone toner image 90i is not sufficiently transferred onto the transfer material (transfer). Bad).

  For this reason, as shown in a portion surrounded by a circle P in FIG. 9B, the character / line image layer toner image 90t side end portion of the toner image 90i of the halftone layer is blanked out, or FIG. As shown in the part surrounded by the circle Q in C), the color changes.

As an apparatus for solving such a problem, when an image output by input image data has a high density character line drawing part in a low density color background part, an edge in contact with the character line drawing part of the color background part Pixels and edge pixels in contact with the color background portion of the character / line drawing portion are detected, and the pixels of the low-density color background portion pixel portion of the input image data based on the position information and pixel value information of the detected edge pixels An image forming apparatus and an image processing apparatus that correct values are known (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 10-065918

  However, in the conventional image forming apparatus and image processing apparatus for correcting the pixel value of the low-density color background portion pixel portion, white spots due to transfer defects can be prevented, but the continuous tone portion around the character line image portion is corrected. Therefore, there is a problem that characters and lines become blurred and lack in clarity.

  Even if the conventional image formation support apparatus adopts a method of correcting the pixel value of the low-density color background portion pixel portion, the same problem occurs.

  The present invention has been made in view of the above circumstances, and prevents a boundary portion that touches a halftone portion of a character or line drawing portion from causing white spots or color change while keeping the character or line drawing portion in a clear state. An object of the present invention is to provide an image forming apparatus and an image forming support apparatus.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that switches a plurality of color materials to form an image of a character or line drawing portion and an image of a halftone portion as separate layers. The image is formed by shifting the color material switching positions of the layers excluding the uppermost layer constituting the character or line drawing portion to the halftone portion side.

  The image forming support apparatus of the present invention also processes a print job to generate and output image data, and switches a plurality of color materials to generate an image of a character or line drawing portion and an image of a halftone portion. An image forming support apparatus provided between image forming apparatuses formed as separate layers, excluding the uppermost layer constituting the character or line drawing portion of the image data input from the front end processor The image data is processed and output to the image forming apparatus so that the color material switching position is shifted to the halftone portion side.

  That is, in the present invention, an image is formed of a plurality of layers of color materials. When the image is composed of an image of a character or line drawing portion and an image of a halftone portion, the two images are formed as separate layers by switching a plurality of color materials.

  At the time of image formation, an image is formed by shifting the color material switching positions of the layers other than the uppermost layer constituting the character or line drawing portion to the halftone portion side. That is, among the plurality of layers constituting the character or line drawing portion, the switching position is not changed for the uppermost color material, and an image is formed by shifting the switching position to the halftone portion side for the layers other than the uppermost layer. .

  An image of a character or line drawing portion often has a relatively high density, and an image of a halftone portion is composed of continuous tone and often has a relatively low density. Accordingly, the density difference of the color material becomes large at the boundary between the character or line drawing portion and the halftone portion, and this may cause white spots or color changes. By shifting the material switching position, it is possible to reduce the density difference by the density of the uppermost color material at the boundary position between the character or line drawing part and the halftone part. Therefore, it is possible to prevent the occurrence of white spots and color changes due to transfer defects that occur when the color material density difference is large.

  In the present invention, since the color material density difference between the character or line drawing portion and the halftone portion is reduced by shifting the color material switching position, the continuous tone portion does not occur. Therefore, the character or line drawing portion can be maintained in a clear state.

  The switching position is preferably shifted to an area where white spots occur or the color changes, and an optimal value may be obtained in advance through experiments or the like, and the formed latent image may be The state (characteristics or change with time) of the image forming apparatus may be determined by sensing, and may be changed as appropriate.

  The process of shifting the color material switching position of the layer excluding the uppermost layer constituting the character or line drawing portion to the halftone portion side is performed by the density of the color material constituting the character or line drawing portion image and the halftone portion. You may make it carry out when the difference with the density | concentration of the color material which comprises the image of a part is more than predetermined value.

  When the color material density difference between the character or line drawing portion and the halftone portion is small, transfer defects do not occur, and an image can be satisfactorily formed without changing the switching position. Therefore, if the process of shifting the switching position is performed only when the density difference is large enough to cause white spots or changes in color, the process can be performed efficiently.

  In addition, since the character or line drawing portion is often formed in black, the uppermost layer of the plurality of color materials constituting the character or line drawing portion can be a K color coloring material. For example, since black characters are often formed by stacking K colors on YMC colors, the edges of the characters or line drawing portions are made black by shifting only the YMC colors excluding K colors to the halftone portion side. It is possible to reduce the density difference of the color material at the boundary position between the character or line drawing portion and the halftone portion while maintaining it.

  As described above, according to the present invention, it is possible to prevent the boundary portion contacting the halftone character or line drawing portion from causing white spots or color change while keeping the character or line drawing portion in a clear state. It has the effect.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Image forming system]
FIG. 1 is a diagram showing an overall schematic configuration of an image forming system according to the present embodiment. The image forming system includes a high-speed LAN (Local Area Network) using a general-purpose communication protocol, and a client terminal for inputting, for example, electronic data (print data) described in a page description language (PDL) to the high-speed LAN. 400 and 402 are connected. The client terminals 400 and 402 are computers capable of executing various application programs under different operating systems (OS). A scanner device 410 that reads an image of a document and outputs the image data is also connected to the high-speed LAN. The high-speed LAN includes DFE devices 500, 502, 504, 506, and 508, BEP (Back End Processor) devices 600, 602, and 604 as image forming support devices according to the present invention, which will be described in detail later. A CTP device 702 that directly creates a printing plate with data is connected.

  Printing is performed in the press device 710 using the printing plate created by the CTP device 702. Further, a BEP device 600 is connected to the CTP device 702 in parallel (to a high-speed LAN). A high-speed printer 746 similar to the image forming apparatus 11 is connected to the BEP device 600.

  An output device 730, high-speed printers 740 and 742 having the same configuration, and a CTP device 700 are connected to the output side of the BEP device 604 connected to the high-speed LAN. The output device 730 and the high-speed printers 740 and 742 perform print output, and the CTP device 700 creates a printing plate. The DFE device 502 is connected to printer proofers 720 and 722 having the same configuration via the BEP device 602. The printer proofers 720 and 722 are for confirming output for printing, and may function as an example of an image forming apparatus.

  The DFE device 504 is connected to a high-speed printer 744, and the DFE device 504 and the high-speed printer 744 are responsible for a department in charge of on-demand printing processing. The DFE device 506 is connected to the output device 732, and the DFE device 508 is connected to the large output device 750. The configuration including the DFE device 506 and the output device 732 and the configuration including the DFE device 508 and the large output device 750 are the same as the configuration of the conventional image forming apparatus.

  The image forming system according to the present embodiment has a configuration in which CTP and an apparatus having a POD (print on demand) function can be mixed in the same system. This is because the BEP device according to the present embodiment has a function for variously processing the data after the print data from the client is converted into raster data (RIP processing).

[Configuration example]
In the image forming system having the above configuration, in order to simplify the description of the embodiment of the present invention, a representative example of a configuration in which a printing plate is created and printed and a configuration in which printing is performed without creating a printing plate are described as an embodiment. Will be described. That is, the configuration A in the case of forming an image using the client terminal 400, the DFE device 500, the CTP device 700, and the press device 710, the client terminal 400, the DFE device 500, the BEP device 600, and the high-speed printer 746 ( The configuration B in the case of forming an image using the apparatus of the image forming apparatus 11) will be described.

  The DFE apparatus 500 has a function of converting data from the client terminal 400 into raster data (RIP processing) and compressing the converted raster image. In this embodiment, the DFE apparatus 500 includes the image forming apparatus 11. Does not require a printer controller function to perform a dependent print control function. That is, the DFE device 500 may have a configuration mainly having only a function of RIP processing.

  FIG. 2 is a diagram showing an embodiment of an image forming system according to the present invention. In other words, the configuration A in which an image instructed to be printed by the client terminal 400 is RIPed by the DFE device 500 and a printing plate is created by the CTP device 702 and then printed by the press device 710, and the RIP image is sent via the BEP device 600. The configuration B for printing by the high-speed printer 746 (image forming apparatus 11) will be described as an embodiment of the image forming system according to the present invention. FIG. 2A shows an outline of a system configuration including the configuration A and the configuration B in the present embodiment, and FIG.

[Configuration A]
In the configuration A, printing is performed using a CTP device 702 that creates a printing plate, a DFE device 500 that outputs print data to the CTP device 702 and instructs printing plate creation, and a printing plate created by the CTP device 702. The press apparatus 710 constitutes a system.

  Since the configuration A is the same as the conventional print processing, detailed description thereof is omitted. However, the DFE apparatus 500 is configured by a front end processor (FEP) unit or ROP (Raster Operation) processing by a front engine. A function of converting data from the client terminal 400 into raster data (RIP processing) and compressing the converted raster image is provided. The DFE apparatus 500 mainly executes only the RIP process in order to create a printing plate. A plate is created by the CTP device 702 from the raster data of the RIP-processed raster image (compressed). An image is pressed on a printing medium by a press device 710 using the printing plate created by the CTP device 702, and printing is performed.

  In the configuration A, the case where the CTP device 702 is connected to the high-speed LAN and the printing plate is created from the print data from the DFE device 500 has been described. However, the CTP device 702 is connected via the BEP device 600. Alternatively, the BEP device 604 and the CTP device 700 in FIG. 1 may be configured. In this case, as described in the configuration B below, the BEP apparatus 600 performs processing depending on the downstream apparatus such as the image forming apparatus 11 and outputs the data based on the print data from the DFE apparatus 500. When the CTP device 700 is adopted as the downstream device, the BEP device 600 performs processing depending on the CTP device 700 and outputs data.

[Configuration B]
Next, the configuration B includes an image forming apparatus 11, a DFE apparatus 500 that passes print data to the image forming apparatus 11 and gives a print instruction, and a BEP apparatus 600 provided between the image forming apparatus 11 and the DFE apparatus 500. Configure the system.

  The image forming apparatus 11 includes an IOT module (IOT main body) 12, a feed (paper feed) module (FM; Feeder Module) 15, an output module 17, and a user interface device 18 such as a personal computer (PC). The feed module 15 may have a multistage configuration. Moreover, you may provide the connection module which connects between each module as needed. In addition, a finisher module may be connected to the subsequent stage of the output module 17. As the finisher module, for example, there are a stacker for stacking sheets and a stapler for binding one or more places, or a punching mechanism for punching holes.

  The DFE device 500 has a function of converting data from the client terminal 400 into raster data (RIP processing) and compressing the converted raster image, and mainly performs RIP processing. This data is processed by the BEP device 600 and output to the image forming apparatus 11.

  The BEP device 600 has a process control function depending on the image forming apparatus 11, but this control function may be instructed by the user interface device 18 or may be determined in advance. When instructing by the user interface device 18, the user interface device 18 has an input device such as a keyboard or a GUI (Graphic User Interface) function that accepts an instruction input while presenting an image to the user, and depends on the image forming device 11. What is necessary is just to comprise so that a process may be instruct | indicated.

  The BEP device 600 enables efficient high-speed output by using the RIP processed data stored in the DFE device. That is, the BEP device 600 generates a command code based on the print control information received from the DFE device 500, and controls the processing timing of each unit in the image forming apparatus 11 according to the engine characteristics. In addition, the BEP device 600 completes the spool processing so as to match the engine characteristics of the IOT module 12, the feed module 15, the output module 17, etc., and then passes the image data to the IOT module 12.

  For example, data including a raster base image subjected to RIP processing is sent from the DFE device 500 to the BEP device 600. As this data, in addition to compressed raster-based image file data such as the TIFF (Tagged Image File Format) format, the number of copies, double-sided / single-sided, color / monochrome, composite printing, sort presence, presence / absence of stapler, etc. are printed. Control information and the like are included.

  Rotation, page allocation (N-UP) within one sheet, repeat processing, paper size adjustment, CMS (Color Management System) for correcting device differences, resolution conversion, contrast adjustment Processing related to RIP processing such as compression ratio designation (low / medium / high) is processed by the DFE device 500, and the control command is not notified to the BEP device 600 (non-notification).

  In addition, collation (booking), double-sided printing, stamping / punching / stapler finisher devices or paper tray alignment processing, discharge surface (up / down) alignment, calibration processing such as gray balance and color shift correction As for screen designation processing and the like (IOT-dependent processing) that is strongly related to the processing characteristics of the image forming apparatus 11, the BEP device 600 processes the control command through the DFE device 500.

  As described above, the DFE device side of this embodiment transfers one job (JOB) unilaterally to the BEP device side in the order of RIP processing without depending on the engine characteristics, and rearranges pages for printing on the BEP device side. To do.

  FIG. 3 is a conceptual block diagram that focuses on the flow of data when the BEP device 600 is interposed between the DFE device 500 and the image forming device 11.

  The DFE device 500 receives print data (hereinafter referred to as PDL data) described in PDL from the client terminal 400, interprets the PDL data, and generates (rasterizes) page-unit image data (raster data). Further, the generated image data is compressed according to a predetermined format and transferred to the BEP device 600 via an interface unit (not shown).

  Note that the DFE apparatus 500 converts color PDL data into a layer of characters and line drawing parts (hereinafter referred to as “character / line drawing layer”) and a layer of halftone parts such as background parts and photographs (hereinafter referred to as “intermediate”) during rasterization. (Layering) is divided into two layers and rasterized, and layer information including information on the position and shape of each layer is created. The image data generated separately for each of the two layers is compressed and transferred to the BEP device 600 together with layer information generated separately.

  On the other hand, the BEP device 600 receives and holds compressed image data processed by the DFE device 500 regardless of the print job and the processing characteristics of the print engine 30 (for example, processed asynchronously with the processing speed of the print engine 30). The compressed image data is read from the image storage unit (not shown) and the image storage unit, and decompression processing corresponding to the compression processing on the DFE apparatus 500 side is performed. An image processing unit 610 that performs optimum image processing (definition processing, gradation correction, etc.) suitable for line drawing or halftone and sends the processed image to the IOT core unit 20 side is provided. The BEP device 600 is further provided with a data receiving unit (not shown) for receiving various data including image data from the DFE device 500. The image processing unit 610 is followed by the image recording unit (IOT core). An interface unit (not shown) for sending to the unit 20) is provided.

  The image processing unit 610 includes a first image processing unit 612, a second image processing unit 614, and an image composition unit 616. The first image processing unit 612 decompresses the character / line image layer image data received from the DFE device 500 and stored in the image storage unit, and performs optimum image processing on the character / line image layer. The second image processing unit 614 expands the image data of the halftone layer received from the DFE device 500 and stored in the image storage unit, and performs optimal image processing for the halftone layer. The image composition unit 616 uses the layer information to be described later to process the image data of the character / line image layer processed by the first image processing unit 612 and the image data of the halftone layer processed by the second image processing unit 614. Composition is performed based on the layer information edited by the editing unit 620.

  The BEP device 600 further includes a layer information editing unit 620. The layer information editing unit 620 edits the layer information received from the DFE device 500. The layer information editing unit 620 is configured as a part of the function of a printer controller configured by a microcomputer that controls each unit of the BEP device 600 and the IOT core unit 20 depending on the processing performance of the IOT core unit 20. ing.

  Furthermore, the image forming apparatus 11 (IOT core unit 20) that receives the image data from the BEP device 600 switches the toner layers of a plurality of colors to form the character / line image layer and the halftone layer as a plurality of separate layers. Can do. That is, an image is formed by switching each color toner layer at the boundary between a character / line image layer formed by laminating a plurality of color toner layers and a halftone layer.

[Operation]
In the image forming system configured as described above, each component operates as follows.

  FIG. 4 is a flowchart for explaining the operation of the DFE apparatus 500. In step 800, print data (PDL data) is input from the client terminal 400 via the network. In step 802, the input PDL data is interpreted, and character / line image layer image data and halftone image data are created in units of pages. In step 804, layer information of the character / line image layer and the halftone layer is created. The layer information is used for image processing performed by the BEP device 600.

  FIG. 5 is a flowchart for explaining the operation of the layer information editing unit 620 of the BEP device 600. The following operations are performed in units of pages. In step 810, based on the layer information input from the DFE device 500, it is determined whether there are a plurality of attributes. That is, an affirmative determination is made if the page is composed of both the character / line image layer and the halftone layer, and a negative determination is made if the page is composed of only one of the character / line image layer and the halftone layer.

  If it is determined in step 810 that there are a plurality of attributes, it is determined in step 812 whether or not the difference in toner density (toner pile height) at the boundary between the attributes is greater than or equal to a threshold value n from the image data of each attribute. to decide. When there are a plurality of boundary portions, the determination is made for each boundary.

  This determination will be described in detail with reference to the explanatory diagram of FIG. In the example shown in FIG. 7A, a character / line drawing character / line drawing layer 100t and a halftone halftone layer 100i are arranged adjacent to each other. The character / line drawing layer 100t is a high-density black layer formed by laminating the respective color toner layers in the order of (K + C + M + Y). The halftone layer 100i is a halftone layer having a relatively low density that is formed by laminating the respective color toner layers in the order of (M + Y). When the image data is input, the switching positions (boundary positions) of the color toner layers constituting the character / line image layer 100t from the character / line image layer 100t to the halftone layer 100i are the same for the K color and the YMC color ( B position in the figure).

  The layer information editing unit 620, based on the image data of the character / line drawing layer 100t and the image data of the halftone layer 100i, and the toner density (toner pile height) of the character / line drawing layer 100t and the toner density of the halftone layer 100i. And the difference H between the toner densities of the two is calculated. Further, the calculated H and the threshold value n are compared to determine whether or not the difference H is greater than or equal to the threshold value n. As for the threshold value n, white spots and color changes occur in the peripheral portion of the character / line drawing layer 100t (that is, the end portion of the halftone layer 100i side of the character / line drawing layer 100t) indicated by A in FIG. As a value to be stored, it is stored in advance in a ROM (not shown) of the microcomputer. Note that the threshold value n may be variable according to the characteristics on the output side.

  If it is determined in step 812 that the difference in toner density (toner pile height) at the boundary between the attributes is equal to or greater than the threshold value n, in step 814, the layer information is converted into the character / line image layer 100t in the CMY toner layer. Is edited so that m pixels spread to the halftone layer 100i side, that is, the switching position is shifted by m pixels to the halftone layer 100i side. At this time, the switching position is not changed for the uppermost K color. Accordingly, as shown in FIG. 7B, the switching position of the uppermost K color toner layer remains unchanged at the B position, and the switching position of the YMC color toner layer is changed to B0. Thus, the switching position between the character / line image layer 100t and the halftone layer 100i is different between the K toner layer and the YMC toner layer.

  The extent to which the character / line drawing layer 100t is expanded, that is, the number of pixels m is stored for each density difference in the ROM (not shown) of the microcomputer. An appropriate value for the number of pixels m can be obtained in advance through experiments or the like. In addition, since the degree of whiteout depends not only on the density difference but also on the characteristics on the output side (IOT core unit 20 side) and the temporal change of the IOT core unit 20, the number of pixels m is set in the IOT core unit 20. It can be made variable accordingly.

  In step 814, the image processing unit 610 is controlled to enlarge the area of the character / line image layer 100t. Specifically, according to the edited layer information, the CMY color toner layer of the character / line drawing layer 100t is expanded by m pixels toward the halftone layer 100i so that the switching position of the CMY color toner layer is B0. To control. Further, control is performed so that the switching position with the halftone layer 100i remains at the B position without spreading the K toner layer.

  If a negative determination is made in step 810, the processing in steps 814 and 816 is not performed because there are no multiple attributes. If a negative determination is made in step 812, it is determined that there is no difference enough to cause white spots or color changes, and similarly, the processing in steps 814 and 816 is not performed.

  FIG. 6 is a flowchart for explaining the operation of the image processing unit 610 of the BEP device 600. In step 820, it is determined whether an area enlargement instruction for the character / line image layer 100 t is received from the layer information editing unit 620. If the enlargement instruction is received, in step 822, the first image processing unit 612 and the second image processing unit 612 are processed. The image processing unit 614 changes the image data of the character / line drawing layer 100t and the image data of the halftone layer 100i. Specifically, according to the edited layer information, the YMC color toner layer of the character / line drawing layer 100t is expanded to m pixels toward the halftone layer 100i so that the switching position of the CMY color toner layer is B0. To process the image data. Further, the image data is processed so that the switching position with the halftone layer 100i remains at the B position without spreading the K toner layer.

  In step 824, image processing (gradation correction) matching each attribute of the character / line drawing layer 100t and halftone layer 100i is performed on each image data. That is, the first image processing unit 612 performs image processing optimal for the character / line image layer 100t on the image data of the character / line image layer 100t, and the second image processing unit 614 performs the image processing optimal for the halftone layer 100i. Processing is performed on the image data of the halftone layer 100i.

  In step 826, the image composition unit 616 synthesizes the image data of the character / line drawing layer 100t and the halftone layer 100i based on the layer information. As described above, if the layer information is edited so that the character / line drawing layer 100t in the CMY color toner layer spreads m pixels toward the halftone layer 100i, the switching of each toner layer is performed according to the edited layer information. The position is adjusted and synthesized. If the layer information is not edited, the switching positions of the toner layers are synthesized with the original state according to the layer information generated by the DEF device 500.

  In step 828, the image composition unit 616 outputs the synthesized image data to the IOT core unit 20. The IOT core unit 20 performs print processing based on the image data input from the BEP device 600.

When each component operates as described above, the difference H between the toner density of the character / line drawing layer 100t and the toner density of the halftone layer 100i shown in FIG. 7A is shown in FIG. 7B. Thus, the toner density of the K toner layer is reduced by H ₁ and becomes H ₂ . That is, since the toner density difference between the character / line drawing layer 100t and the halftone layer 100i is reduced, it is possible to prevent transfer defects and to prevent image quality defects such as white spots and color changes. Note that, in the character / line image layer 100t in the region from B to B0 formed by changing the switching position, the toner density itself of each color is not reduced, so that continuous gradation is not achieved. For this reason, the edge of the character / line image layer 100t is not blurred, and a clear state is maintained.

  In the above-described embodiment, the example in which the BEP device 600 performs the process of determining the attribute and shifting the switching position of the character / line image layer 100t and the halftone layer 100i has been described. However, the IOT core unit of the image forming apparatus 11 20 itself may be provided with a function for performing such processing. Thereby, even when the image forming apparatus 11 alone receives a print instruction from the client terminal, the same effect can be obtained. In this case, the configuration of the BEP device 600 shown in FIG. 3 described above may be added to the configuration of the general IOT core unit 20.

  In the above-described embodiment, the example in which the switching position of the CMY color toner layer excluding the uppermost K color has been described. However, the present invention is not limited to this, and for example, the character / line image layer 100t is K. In the case of a dark brown layer composed of a CMY color toner layer that does not include a color, it is possible to perform processing so as to shift the switching position of the MY color toner layer excluding the uppermost layer C color.

  Furthermore, as to the extent to which the character / line image layer 100t is expanded, that is, the number of pixels m can be obtained in advance by an experiment or the like as described above, the state of the latent image in the IOT core unit 20 can be obtained. It is also possible to calculate how much white spots are caused from this state and appropriately change the value of the number of pixels m. As a result, processing can be performed while shifting by an appropriate number of pixels in accordance with changes over time of the IOT core unit 20.

1 is a schematic diagram illustrating an overall configuration of an image forming system according to an exemplary embodiment. 1 is a diagram illustrating an embodiment of an image forming system. It is a block diagram which shows one Embodiment of a DFE apparatus and a BEP apparatus. It is a flowchart explaining operation | movement of a DEF apparatus. It is a flowchart explaining operation | movement of the layer information editing part of a BEP apparatus. It is a flowchart explaining operation | movement of the image process part of a BEP apparatus. It is explanatory drawing explaining the process which shifts a switching position. 1 is a diagram illustrating an outline of a conventional image forming system. It is explanatory drawing explaining the conventional problem.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Image forming device 400 ... Client terminal 500 ... DFE device 600 ... BEP device 610 ... Layer information editing unit 620 ... Image processing unit 700 ... CTP device 710 ... Press device 720 ... Printer proofer 730 ... Output device 740 ... High-speed printer 750 ... Large output machine

Claims (6)

An image forming apparatus that switches a plurality of color materials to form an image of a character or line drawing portion and an image of a halftone portion as separate layers,
An image forming apparatus for forming an image by shifting a color material switching position of a layer excluding the uppermost layer constituting the character or line drawing portion to a halftone portion side.   When the difference between the density of the color material constituting the image of the character or line drawing portion and the density of the color material constituting the image of the halftone portion is equal to or greater than a predetermined value, the uppermost layer constituting the character or line drawing portion The image forming apparatus according to claim 1, wherein an image is formed by shifting a color material switching position of a layer excluding the layer to a halftone portion side.   The image forming apparatus according to claim 1, wherein an uppermost layer of the plurality of color materials constituting the character or line drawing portion is a K color material. A front-end processor that processes a print job to generate and output image data, and an image forming apparatus that switches a plurality of color materials to form a character or line drawing portion image and a halftone portion image as separate layers An image forming support apparatus provided between
In the image data input from the front-end processor, the image data is processed so that the color material switching position of the layer excluding the uppermost layer constituting the character or line drawing portion is shifted to the halftone portion side, and An image forming support apparatus that outputs to an image forming apparatus.   When the difference between the density of the color material constituting the image of the character or line drawing portion and the density of the color material constituting the image of the halftone portion is a predetermined value or more, the image data input from the front end processor 5. The image data is processed and output to the image forming apparatus so that a color material switching position of a layer excluding the uppermost layer constituting the character or line drawing portion of the image is shifted to a halftone portion side. Image forming support apparatus.   6. The image forming support apparatus according to claim 4, wherein an uppermost layer of the plurality of color materials constituting the character or line drawing portion is a K color material.

Images