JP2011120109A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has a normal color mode for forming a color image from basic colorants of CMYK or the like and a full-color mode, during which a color image can be formed over a wider color reproduction area by adding any special colorant thereto, and can appropriately and automatically select which mode is to be used. <P>SOLUTION: On the basis of the color distribution of an input image, it is selected whether an image forming operation for the input image is to be performed under a full-color mode or under a normal color mode. For example, if a specific image region, which has a color of a color gamut that can be reproduced only under the full-color mode and in which a color difference from an adjacent image region becomes less than or equal to a threshold, is present in the input image for a prescribed quantity or more, the full-color mode is selected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms a color image on recording paper or the like.

  In an image forming apparatus such as an electrophotographic system or an inkjet system, generally, a color image is made of four color materials (ink, toner, etc.) of cyan (C), magenta (M), yellow (Y), and black (K). In recent years, there are image forming apparatuses that use 6 or 7 color materials for higher quality printing.

  For example, there is an ink jet printer that uses seven color materials in which red (R), green (G), and blue (B) are added to four colors of C, M, Y, and K (see Patent Documents 1 and 2). ).

  For high-quality printing, light cyan Lc, which is a light cyan color, and light magenta Lm, which is a light magenta color, are printed in a 6-color mode in which four colors C, M, Y, and K are added. However, there is an image forming apparatus that switches to print in a four-color mode of C, M, Y, and K when image quality is not so high. In this apparatus, it is determined whether the image to be printed is an achromatic color or a character ratio exceeding a certain level, and the four-color mode is used when the achromatic color or the character ratio is a certain value or more. (See Patent Document 3).

  In addition, there is an image forming apparatus that switches between a 4-color mode and a 6-color mode according to page settings (see Patent Document 4). More specifically, if Nin1 is set to reduce and combine images for a plurality of pages (N pages) on a single sheet, the image is reduced, so it is determined that high image quality is not necessary, and four colors The mode is automatically selected.

  In addition, although there is no change in the color material to be used, there is an apparatus that detects an image characteristic to be printed and switches a color reproduction process (image processing program) (see Patent Document 5).

JP-A-8-244254 JP 10-44473 A JP 2007-36793 A Japanese Patent Laid-Open No. 2005-169685 JP 2002-182634 A

  In the conventional 6-color mode and 7-color mode, light cyan and light magenta with a low density are added to the four colors C, M, Y, and K, and R, G, and B are mixed by mixing C, M, and Y. In order to avoid the difficulty of accurate reproduction, R, G, and B color materials are added, and an outline of a color region (color reproduction region) that can be reproduced with four color materials, There was almost no difference in the outline of the color reproduction area by 6 or 7 colorants. That is, the use of the 6-color mode or the 7-color mode provides a high-definition image quality within a color reproduction area equivalent to the 4-color mode, and does not provide a wider color reproduction area.

  In the prior art, the criteria for determining whether to use the 6-color mode or the 7-color mode are the achromatic color, the ratio of characters, the presence / absence of Nin1, etc., which are necessary for high-definition image formation. Since this is for determining whether or not the color reproduction region is widened by adding a color material, it is not appropriate as a criterion for determination.

  The present invention is intended to solve the above-described problem. By adding a color material, it is possible to form an image in a wider color reproduction region, and whether or not an image should be formed in a mode in which a color material is added. An object of the present invention is to provide an image forming apparatus capable of automatically selecting more appropriately.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] A basic color material set composed of color materials of a plurality of colors and capable of reproducing the first color region, and the first color region including the first color region by the combined use of the basic color material set Any of a full color mode using at least one special color material capable of reproducing a wider second color region, and a normal color mode using the basic color material set without using the special color material And an image forming unit for forming a color image,
Based on the color distribution of the input image, it is selected whether the image forming operation related to the input image is performed in the full color mode or the normal color mode, and the image forming operation related to the input image is performed in the selected mode. An image forming apparatus comprising: a control unit that causes the image forming unit to perform.

  In the above invention and the invention according to [3] below, a full color mode in which a basic color material set and a special color material are used to form a color image, and a basic color material set is used without using a special color material. The normal color mode for forming a color image is selected based on the color distribution of the input image. The second color region that can be reproduced in the full color mode is a wider color region including the first color region that can be reproduced in the normal color mode, and whether or not a color image should be formed in this wide color region. Automatically selected based on the color distribution of the input image.

[2] The control unit performs color conversion on the input image corresponding to the second color region, and the image after the color conversion is performed for each image region in which pixels in the same color or a predetermined approximate color range are continuous. When the image is divided into two, a specific image region that is a color image region that does not enter the first color region but enters the second color region and has a color difference with a neighboring image region equal to or less than a predetermined value is obtained. The image forming apparatus according to [1], wherein the full color mode is selected when a predetermined amount or more exists.

  In the above invention, the input image is color-converted corresponding to the color region (second color region) that can be reproduced in the full-color mode, and the pixels after the color conversion are continuously in the same color or approximate color range. Divide each image area. Then, an image area (spot color image area) that has a color that does not enter the first color area but has a color that enters the second color area and a color difference with a neighboring image area is equal to or less than a predetermined value is detected. If there is a predetermined amount or more, image formation relating to the input image is performed in the full color mode. In other words, if there is an image area with a color difference that is not reproducible without using a special color material in combination with the image area in the vicinity of the image area, a full color mode that uses the special color material To form a color image.

[3] A basic color material set composed of color materials of a plurality of colors and capable of reproducing the first color region, and the first color region including the first color region by the combined use of the basic color material set Any of a full color mode using at least one special color material capable of reproducing a wider second color region, and a normal color mode using the basic color material set without using the special color material And has an image forming part for forming a color image,
When the input image is color-converted so that the input image corresponds to the second color area, and the color-converted image is divided into image areas in which pixels in the same color or a predetermined approximate color range are continuous In addition, there is a predetermined amount or more of a specific image region that is a color image region that does not enter the first color region but enters the second color region and has a color difference with a neighboring image region that is equal to or less than a predetermined value. If the image is an image, the image forming unit performs the image forming operation related to the input image in the full color mode, and if the specific image area is an image that does not exist in the predetermined amount or more, the image forming operation related to the input image is performed. An image forming apparatus, wherein the image forming unit performs an operation in the normal color mode.

[4] The case where the specific image area is present in a predetermined amount or more is a case where a ratio of the specific image area to the entire input image is a reference value or more. [2] or [3] Image forming apparatus.

  In the above invention, the full color mode is selected when the ratio of the specific image area to the entire input image is equal to or greater than the reference value.

[5] The control unit performs color conversion on the input image so as to correspond to the second color area, and does not enter the first color area in the image after the color conversion. The image forming apparatus according to [1], wherein the full color mode is selected when there are a predetermined number or more of color pixels entering the region.

  In the above invention, when there are a predetermined number or more of pixels having colors that cannot be reproduced unless a special color material is used in combination, the full color mode is selected.

[6] Any one of [1] to [5], wherein the special color material is a color material having the same hue and high saturation as the color material constituting the basic color material set. The image forming apparatus described in 1.

  In the above invention, the color material having the same hue as the color material constituting the basic color material set and higher saturation than the color material is used as the special color material. It is possible to reproduce a color region with high saturation.

[7] The color material constituting the basic color material set and the special color material are toners,
[1] to [6], wherein the basic color material set is composed of cyan toner, magenta toner, yellow toner, or black toner. The image forming apparatus according to claim 1.

[8] The image forming unit includes a developing unit that develops toner of each color of the color material constituting the basic color material set and the special color material,
When forming an image in the full color mode, use a developing device corresponding to the color material constituting the basic color material set and a developing device corresponding to the special color material,
When an image is formed in the normal color mode, the developing device corresponding to the color material constituting the basic color material set is used without using the developing device corresponding to the special color material [7. ] The image forming apparatus described in the above.

  In the above invention, in the normal color mode, the developing device related to the special color material is suspended, so that the deterioration of the developing device and the energy consumption for driving the developing device are reduced.

[9] When an image is formed in the normal color mode, data indicating no image is given to the image forming unit as image data corresponding to the color of the special color material [1] The image forming apparatus according to any one of [7] to [7].

  In the above-described invention, when an image is formed in the normal color mode, the image forming unit is provided with data indicating no image (for example, “0”) as image data corresponding to the color of the special color material. An image forming operation that does not use is realized. Since the normal color mode and the full color mode can be switched only by processing the image data, the apparatus configuration can be simplified.

  According to the image forming apparatus of the present invention, it is possible to form an image in a wider color reproduction region by adding a color material, and automatically determine whether or not to form an image in a mode in which a color material is added based on a more appropriate standard. Selected.

FIG. 2 is an explanatory diagram illustrating a use environment of the image forming apparatus according to the present invention. 1 is a block diagram illustrating a schematic configuration of a terminal device that requests printing to an image forming apparatus according to the present invention. FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus according to the present invention. FIG. 3 is an explanatory diagram illustrating a mechanical schematic configuration of a printing unit included in the image forming apparatus according to the present invention. FIG. 2 is an explanatory diagram illustrating a mechanical schematic configuration of a printing unit included in the image forming apparatus according to the present invention, in which a spot color image forming unit is moved to a retracted position. FIG. 4 is an explanatory diagram illustrating a color area of a color image that can be reproduced by a printing unit of the image forming apparatus according to the present invention. It is a flowchart which shows the operation | work which a user performs with a terminal device, when performing PC printing. FIG. 4 is a front view illustrating an example of a printer driver screen. 6 is a front view illustrating an example of a property screen of a printer driver. FIG. It is a flowchart which shows operation | movement of the printer driver installed in the terminal device. 3 is a flowchart showing an outline of the entire operation performed by the image forming apparatus according to the present invention. 12 is a flowchart showing details of a conversion process to print CMYK data (step S205 in FIG. 11). It is a flowchart which shows the detail of the conversion process to Lab value (step S206 of FIG. 11). It is a flowchart which shows the detail of a mode determination process (step S207 of FIG. 11). It is explanatory drawing which shows the relationship between color difference (DELTA) E and the human sense with respect to the color difference by a list. It is a flowchart which shows the calculation process of a color difference. 12 is a flowchart showing details of a printing process (step S209 in FIG. 11). 18 is a flowchart showing details of developing device usage frequency counting processing (step S309 in FIG. 17). FIG. 6 is a front view illustrating an example of a state where a warning is displayed on an operation panel of the image forming apparatus. It is a flowchart which shows the detail of the printing process (step S209 of FIG. 11) in a modification. It is a flowchart which shows the other example of a mode determination process.

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

  FIG. 1 shows a use environment of an image forming apparatus 10 according to the present invention. The image forming apparatus 10 is used by being connected to a network 2 such as a LAN (Local Area Network) in an office. A terminal device 50 such as a personal computer having a document creation function is connected to the network 2.

  The image forming apparatus 10 includes a copy function that optically reads a document and prints a duplicate image on a recording sheet, a scan function that stores image data of the read document as a file, and transmits the file to an external terminal, and a terminal device This is a device generally referred to as a digital multi-function peripheral (MFP) having a PC print function for printing characters and images on recording paper based on a print file received from 50 or the like. In the PC print function, the image forming apparatus 10 also functions as a print controller that interprets and rasterizes a print file.

  The image forming apparatus 10 has, as operation modes for forming a color image, a normal color mode using four color materials of cyan (C), magenta (M), yellow (Y), and black (K), and the above-described 4 modes. It has a full color mode that forms a color image using a color and a special color material (special color material) other than these, and which mode to use based on the color distribution of the image to be printed The function to select and switch automatically.

  FIG. 2 shows a schematic configuration of the terminal device 50. The terminal device 50 includes a CPU (Central Processing Unit) 51, a memory 52, a hard disk device (HDD (Hard Disk Drive)) 53, a communication I / F (Interface) unit 54, a display unit 55, and an operation unit 56. And connect. The CPU 51 controls the operation of the terminal device 50 based on the program stored in the memory 52. The memory 52 is a ROM (Read Only Memory) that stores programs executed by the CPU 51 and various fixed data, a work memory that temporarily stores various data when the CPU 51 executes the programs, and transmission / reception related to transmission / reception. It is composed of a RAM (Random Access Memory) used as a communication buffer for temporarily storing data.

  The hard disk device 53 is a device that stores various data in a nonvolatile manner. The communication I / F unit 54 functions to communicate with the image forming apparatus 10 and the like through the network 2. The display unit 55 includes a display device such as a liquid crystal display. The operation unit 56 includes an input device such as a keyboard and a mouse (pointing device).

  The terminal device 50 includes, as print data, an OS (Operating System) program, an application program for creating, editing, and processing documents, drawings, illustrations, photographs, and the like, and data such as documents and illustrations created by the application programs. A printer driver program that converts and transmits it to the image forming apparatus 10 is installed. In the application program, a document, an illustration, and the like can be created in color, and the user can specify various colors of the document, the illustration, and the like.

  FIG. 3 shows a schematic configuration of the image forming apparatus 10. The image forming apparatus 10 includes a CPU 11, a memory 12, a hard disk device (HDD) 13, a communication I / F unit 14, an automatic document feeder (ADF) 21, an image reading unit 22, a display unit 23, An operation unit 24, a paper feeding unit 25, a printing unit 26, and a post-processing unit 27 are connected.

  The CPU 11 controls the operation of the image forming apparatus 10 based on a program stored in the memory 12. The memory 12 stores a ROM for storing various programs executed by the CPU 11 and fixed data, a work memory for temporarily storing various data when the CPU 11 executes the programs, and data related to transmission / reception temporarily. It comprises a communication buffer to be stored and a RAM used as an image memory for storing image data.

  Various data are stored in the hard disk device 13 in a nonvolatile manner. The hard disk device 13 also stores a color profile for color conversion.

  The display unit 23 is configured by a liquid crystal display or the like, and displays various screens such as an operation screen, a setting screen, a confirmation screen, and a notification screen. The operation unit 24 includes various buttons such as a start key, a stop key, and a numeric keypad, and a touch panel that is provided on the surface of the liquid crystal display and detects a pressed coordinate position. Accept various operations.

  The automatic document feeder 21 feeds the originals stacked on the original placement tray 21a (see FIG. 1) one by one to the original reading position of the image reading unit 22, and discharges the read originals to the original discharge tray 21b. Fulfills the function of

  The image reading unit 22 performs a function of optically reading a document in color or monochrome and acquiring corresponding image data. The image reading unit 22 is a light source that irradiates light on a document, and a color line image that receives reflected light from the document and outputs an electrical signal corresponding to the light intensity for each color component (for example, R, G, B). A sensor and various mirrors and condenser lenses for guiding reflected light from the document to the line image sensor are provided. The image forming apparatus 10 conveys and reads a document by an automatic document conveyance device 21 so as to pass through the document reading position in a state where the reading position of the line unit by the color line image sensor is fixed to a predetermined document reading position. A document can be read in a so-called flow reading format. It is also possible to read a document by placing the document on a platen glass and moving a light source or a mirror along the document.

  The paper feeding unit 25 includes a plurality of paper feeding cassettes (see FIG. 1) 25a for storing recording paper, and fulfills a function of feeding recording paper from one of the selected paper feeding cassettes 25a and feeding it to the printing unit 26.

  The printing unit 26 functions to form a color or monochrome image on the recording paper fed by the paper feeding unit 25. The printing unit 26 uses toners of a plurality of types as color materials for forming an image on recording paper. The printing unit 26 includes an image forming unit 30 that forms a toner image on the recording paper, a fixing unit 28 that fixes the toner image formed by the image forming unit 30 to the recording paper, and the recording paper fed by the paper feeding unit 25. The image forming unit 30 and the fixing unit 28 pass through the image forming unit 30 to the post-processing unit 27 (see FIG. 1).

  The post-processing unit 27 folds the recording paper while binding the recording paper conveyed from the printing unit 26 to the paper discharge tray 27a (see FIG. 1), or binds a plurality of recording papers and staples them. Or post-processing such as punching holes.

  FIG. 4 shows a schematic mechanical configuration of the printing unit 26. The image forming unit 30 of the printing unit 26 is an endless ring-shaped intermediate transfer belt 31 that circulates in the direction of arrow A in the figure, and a basic image forming unit 32 that is disposed along the circulation path of the intermediate transfer belt 31. A special color image forming unit 33, a black image forming unit 34, and a transfer unit 35.

  The basic image forming unit 32 forms a toner image on the intermediate transfer belt 31 with a plurality of color materials (toners) constituting a basic color material set. The basic color material set is composed of cyan (C) toner, magenta (M) toner, and yellow (Y) toner (color material). The basic image forming unit 32 includes an image forming unit that forms a toner image of the color for each of a plurality of colors constituting the basic color material set. Specifically, the basic image forming unit 32 includes a basic color C image forming unit 32c that forms a toner image with cyan (C) toner, and a basic color M image that forms a toner image with magenta (M) toner. An image portion 32m and a basic color Y image forming portion 32y that forms a toner image with yellow (Y) toner are provided.

  The spot color image forming unit 33 is arranged on the upstream side of the basic image forming unit 32 in the circumferential direction of the intermediate transfer belt 31. The special color image forming unit 33 includes a special color C image forming unit 33c ′ that forms a cyan (high-saturated cyan (C ′)) toner image having a higher saturation than the cyan color of the basic color material set, and a basic color material set. The special color M image forming portion 33m ′ for forming a magenta (highly saturated magenta (M ′)) toner image having a higher saturation than the magenta color, and a yellow (high saturation) higher than the yellow color of the basic color material set And a special color Y image forming portion 33y ′ for forming a toner image of a color (referred to as yellow (Y ′)).

  The black image forming unit 34 is disposed on the downstream side of the basic image forming unit 32 in the circumferential direction of the intermediate transfer belt 31. The black image forming unit 34 functions to form a black (K) toner image on the intermediate transfer belt 31.

  Each of the image forming units 32c, 32m, 32y, 33c ′, 33m ′, 33y ′, and 34 includes a cylindrical photosensitive drum 41 on which an electrostatic latent image is formed, and a charging device disposed around the cylindrical photosensitive drum 41. A developing unit 42, a cleaning device, and a writing unit 43 for irradiating the photosensitive drum 41 with laser light. The charging device and the cleaning device are not shown.

  The photosensitive drum 41 is driven by a drive unit (not shown) and rotates in a certain direction (the direction of arrow B in the drawing), and the charging device uniformly charges the rotating photosensitive drum 41. The writing unit 43 includes a laser diode, a polygon mirror, various lenses, a mirror, and the like, and is a laser that is turned on / off according to image data corresponding to the color of toner used by the developing unit of the image forming unit. By scanning the photosensitive drum 41 with light, an electrostatic latent image is formed on the surface of the photosensitive drum 41. The developing device 42 visualizes the electrostatic latent image on the photosensitive drum 41 with toner. The toner image formed on the surface of the photosensitive drum 41 is transferred to the intermediate transfer belt 31 at a location where it contacts the intermediate transfer belt 31. The cleaning device removes and collects the toner remaining on the surface of the photosensitive drum 41 after the transfer by rubbing with a blade or the like.

  By forming the toner images of the respective colors on the intermediate transfer belt 31 by the image forming sections 32c, 32m, 32y, 33c ′, 33m ′, 33y ′, and 34, a color image (toner of various colors) is formed. Image) is formed on the intermediate transfer belt 31.

  The transfer unit 35 functions to transfer the toner image formed on the intermediate transfer belt 31 by the basic image forming unit 32, the special color image forming unit 33, and the black image forming unit 34 to a recording sheet. The transfer unit 35 is a roller pressed toward the intermediate transfer belt 31 at a predetermined position downstream of the black image forming unit 34 in the circumferential direction of the intermediate transfer belt 31, and the recording paper conveyed by the conveyance unit 29 is this. The toner image on the intermediate transfer belt 31 is transferred to the recording paper when passing while being sandwiched between the roller and the intermediate transfer belt 31. A broken line in the figure is a path P along which the conveyance unit 29 conveys the recording paper, and the recording paper is conveyed in the direction of arrow F.

  The fixing unit 28 includes a roller heated by a heater and a counter roller pressed against the roller. The recording paper on which the toner image on the intermediate transfer belt 31 is transferred by the transfer unit 35 is further conveyed by the conveyance unit 29, and is heated by pressure when passing between the rollers of the fixing unit 28, so that the toner is fixed to the recording paper. . The recording paper that has passed through the fixing unit 28 is further conveyed and sent to the post-processing unit 27.

  Each of the basic image forming unit 32 and the special color image forming unit 33 can be displaced between a contact position where the photosensitive drum 41 is brought into contact with the intermediate transfer belt 31 and a retracted position where the photosensitive drum 41 is separated from the intermediate transfer belt 31. ing. Each of the units 32 and 33 is driven by a driving unit (not shown) such as a motor or a solenoid (not shown) controlled by the CPU 11 so as to be individually displaced between a contact position and a retracted position. FIG. 5 illustrates a state where the spot color image forming unit 33 is moved to the retracted position. Each of the basic image forming unit 32 and the spot color image forming unit 33 can be retracted to a retracted position and stopped. Note that the black image forming section 34 is not displaced as described above and is always arranged at the contact position.

  When forming a color image in the normal color mode, the image forming apparatus 10 uses the basic image forming unit 32 and the black image forming unit 34, and the special color image forming unit 33 is retracted to the retracted position and is not used. When a color image is formed in the full color mode, the special color image forming unit 33 is displaced to the contact position, and the basic image forming unit 32, the special color image forming unit 33, and the black image forming unit 34 are used. When forming a monochrome image, both the basic image forming unit 32 and the spot color image forming unit 33 are displaced to the retracted position, and only the black image forming unit 34 is used.

  FIG. 6 shows a color area of a color image that can be formed on the recording paper by the printing unit 26 by an expression method generally called gamut. This corresponds to a color space stereoscopic image represented by a Lab value, which will be described later, viewed from above. The gamut represents a color range that can be reproduced by a peripheral device such as a printer or a monitor. LAB is a color model that expresses numerical values and areas of colors with three elements, and L axis = brightness, a axis = green to red, and b axis = blue to yellow. In FIG. 6, the L axis is perpendicular to the paper surface.

  A first color area 61 surrounded by a broken line is a color area (color reproduction area) that can be reproduced by cyan (C), magenta (M), and yellow (Y) toner (normal toner) constituting the basic color material set. Show. The first color region 61 is a color reproduction region when an image is formed in the normal color mode using the basic image forming unit 32 and the black image forming unit 34 without using the special color image forming unit 33. A special color area 62 surrounded by a solid line is a color area (color reproduction area) that can be reproduced by toners of high saturation cyan (C ′), high saturation magenta (M ′), and high saturation yellow (Y ′) used by the special color image forming unit 33. ). Even if black toner is further added, the color reproduction area is the same.

  Note that a color material that includes the first color region 61 and can reproduce a color region wider than the first color region 61 when used in combination with the basic color material set is referred to as a special color material. When the special color material is toner, the toner is called special color toner. Further, the color area that can be expressed by the combined use of the basic color material set and the special color material is changed to the second color area without entering the second color area, the first color area that can be reproduced by the basic color material set. The included area is defined as an extended color area 63.

  The high saturation cyan (C ′), high saturation magenta (M ′), and high saturation yellow (Y ′) are special color toners. If these three special color toners and a basic color material set are used in combination, they are shown in FIG. A region obtained by combining the first color region 61 and the spot color region 62 becomes a second color region, and color reproduction is possible in this color region. A color area (second color area) obtained by combining the first color area 61 and the special color area 62 is an image in a full color mode using the basic image forming unit 32, the special color image forming unit 33, and the black image forming section 34. This is a color reproduction region when forming. In FIG. 6, the shaded area is an extended color area 63 that is expanded by using the above-mentioned three kinds of special color toners together.

  Next, an operation when PC printing is performed from the terminal device 50 will be described.

  First, the operation on the terminal device 50 side will be described. FIG. 7 shows a flow of work performed by the user at the terminal device 50 when performing PC printing. The user creates a document to be printed including a document, a drawing, a photograph, an illustration, and the like on the terminal device 50 using an application. (Step S101). When “Print” is selected from the file menu for printing after completion of the document (step S102), a printer driver screen 71 as shown in FIG. 8 is displayed on the display unit 55 of the terminal device 50. Further, when the property button 72 on the printer driver screen 71 is selected and operated, a property screen 75 as shown in FIG. 9 is displayed on the display unit 55 of the terminal device 50. Through the screen 75, the user can make various settings related to printing, for example, The document size, output size, printing method (single side, double side, booklet, etc.), finishing (staple, punch), etc. can be set (step S103). After performing various settings as necessary, the user selects and operates the OK button 73 on the printer driver screen 71 (FIG. 7, step S104).

  FIG. 10 shows the operation of the printer driver installed in the terminal device 50. The printer driver interprets various settings selected on the property screen 75, and converts the setting contents into various parameter values (step S121). When the printer driver receives a selection operation of the OK button 73 on the printer driver screen 71 (step S122; Yes), the printer driver converts the document data to be printed into a print file (step S123). The print file is a data file in which print contents are described in a language that can be interpreted by the print controller of the image forming apparatus 10. For example, a print file is described using PDL (Page Description Language) or PJL (Printer Job Language). Further, the printer driver transmits the set various parameters and the print file to the image forming apparatus 10 that is the printing destination from the communication I / F unit 54 via the network 2 (step S124), and the process ends.

  Next, the operation of the image forming apparatus 10 that has received the print file from the terminal device 50 will be described. FIG. 11 shows a schematic flow of the entire operation performed by the image forming apparatus 10. The communication I / F unit 14 of the image forming apparatus 10 receives the print file and parameters transmitted from the printer driver of the terminal device 50 (step S201). When the reception is completed (step S202; Yes), the CPU 11 of the image forming apparatus 10 performs rasterization processing based on the received print file to create bitmap format image data (step S203). (Step S204).

  Next, the image data stored in the memory 12 is converted into print CMYK data for each bit (pixel) (step S205). The print CMYK data is data in which each pixel is represented by data indicating the density of the C color, data indicating the density of the M color, data indicating the density of the Y color, and data indicating the density of the K color.

  The CPU 11 further converts the print CMYK data into Lab values (step S206). This is an operation for calculating the color difference with colors that can be reproduced by the image forming apparatus 10, not the original image data. Each converted data is stored in a predetermined storage area of the memory 12.

  Thereafter, a mode determination process is performed to determine whether the printing related to the image data should be printed in the full color mode or the normal color mode (step S207). After the mode determination, various parameters set by the user using the printer driver are analyzed (step S208), the analysis result is notified to the printing unit 26, and the printing process is executed by the printing unit 26 (step S209).

  FIG. 12 shows details of the conversion process to print CMYK data (step S205 in FIG. 11). First, image data to be converted is input (step S221). The input image data is in RGB format in which each pixel is represented by R, G, and B color components, or in CMYK format in which each pixel is represented by C, M, Y, and K color components. is there. Image processing is performed on the image data as necessary (step S222). For example, enlargement / reduction, resolution conversion, and the like are performed.

  Thereafter, the output device information of the image forming apparatus 10 is used to perform color conversion into print CMYK data when toner is used (step S223), and the color-converted data is output (step S224), thereby ending the processing. . This color conversion is performed using an ICC (International Color Consortium) profile corresponding to the output device. Here, when the basic image forming unit 32, the spot color image forming unit 33, and the black image forming unit 34 are used in combination, that is, cyan (C), magenta (M), yellow (Y), and high chroma cyan (C ′). Using high saturation magenta (M ′), high saturation yellow (Y ′), and black (K) toners, color conversion is performed using a reproducible color space as a color space of the output device.

  FIG. 13 shows details of the conversion process to the Lab value (step S206 in FIG. 11). The print CMYK data to be converted is input (step S241), the output device information of the image forming apparatus 10 is input (step S242), and the print CMYK data is reflected using the color conversion table reflecting the characteristics of the printing unit 26. The data is converted into Lab data in which each pixel is represented by a Lab value (step S243) and output (step S244). That is, the input print CMYK data can be reproduced by using the basic image forming unit 32, the special color image forming unit 33, and the black image forming unit 34 in combination (the first color region 61 and the special color color in FIG. 6). The print CMYK data is converted to Lab data by recognizing that the data is a color reproduction area (color space combined with the area 62).

  FIG. 14 shows details of the mode determination process (step S207 in FIG. 11). This process is performed on the Lab data obtained by the process of FIG.

  In this process, the entire image is divided (area division) into areas (same color areas) where the same color or approximate colors continue, and only the same color area that exceeds the specified area is extracted, and the extracted same color area is expanded. The same color area having the color of the color area 63 is further extracted, the color difference ΔE between the same color area and the adjacent same color area is obtained and compared with a threshold value, and the comparison result is set to the full color mode or the normal color mode. Is judged.

  Specifically, the color of the target pixel is compared with the colors of the surrounding pixels, and if the color difference is equal to or smaller than a predetermined value, the target pixel and the surrounding pixels are determined to be the same color image region (same color region) ( Step S261). Specifically, an area that can be expanded from the target pixel to the periphery to the maximum within a range in which the color difference from the target pixel satisfies the condition of a predetermined value or less is set as the same color area. It is determined whether or not the area of the same color area thus obtained is equal to or greater than the specified area (step S262). If not equal to the specified area (step S263; No), the process proceeds to step S265. If it is equal to or larger than the prescribed area (step S263; Yes), the color, position and area of the same color area are stored as area information (step S264), and the process proceeds to step S265.

The specified area may be set to an arbitrary value such as 1 cm ² . Further, in steps S262 and S263, instead of using the area as a reference, the perimeter of the same color region or the length of the portion where the same color region and one adjacent same color region are in contact may be used as a reference. The length and area may be used as a standard.

  In step S265, it is checked whether or not the above processing (steps S261 to S264) has been completed for all the pixels. If not all pixels have been completed (step S265; No), an unchecked pixel is set as a new pixel of interest in step S261. And continue processing. If all pixels have been completed (step S265; Yes), the process proceeds to step S266. At the time when all the pixels are completed, the determination target image is divided into a plurality of the same color regions, and the region information of the same color image region larger than the specified area is stored.

  In step S266, the stored area information is referred to, and for each of the same color areas having the color of the extended color area 63, a color difference from another adjacent same color area is calculated. If the same color area having the color of the extended color area 63 and the same color area with a color difference from the adjacent same color area equal to or smaller than the threshold value (this is a specific image area) is present (step S267; Yes), the determination is made. The result is set to the full color mode (step S268), and the process is terminated. If the specific image area does not exist (step S267; No), the determination result is set to the normal color mode (step S269), and the process is terminated.

  When the color difference between the same color area (the noticed same color area) having the color of the extended color area 63 and the same color area adjacent thereto (adjacent same color area) is larger than the threshold, for example, the color of the noticed same color area in FIG. When the color of the same color area is set to Q2, there is no significant difference in the color difference between the target same color area and the adjacent same color area even if printing is performed in the full color mode or the normal color mode. That is, in the full color mode, the color difference between the color Q1 of the noticed same color area and the color Q2 of the adjacent same color area is the distance between Q1 and Q2. When this is printed in the normal color mode, the color Q2 of the adjacent same color area is originally in the first color area 61 and thus does not change, and the color Q1 of the target same color area in the extended color area 63 is the first color area. The color Q1 ′ reproduced in 61 is obtained, and the color difference between the target same color area and the adjacent same color area is Q1′−Q2. Thus, when the color difference (Q1-Q2) in the full color mode is large, the rate of change from the color difference (Q1-Q2) in the full color mode to the color difference (Q1'-Q2) in the normal color mode is relatively small. So, the difference is hardly perceivable by humans. Therefore, there is substantially no difference in image quality between when the normal color mode is used and when the full color mode is used, and the necessity for using the full color mode is low.

  On the other hand, when the color difference between the target same color region and the adjacent same color region is small in the color reproduction region of the full color mode, for example, when the color of the target same color region is Q1 and the color of the adjacent same color region is Q3 in FIG. Then, the subtle color difference that is reproduced becomes even smaller in the normal color mode (and is sometimes crushed), making it impossible for humans to see. That is, in the full color mode, the color difference between the color Q1 of the noticed same color area and the color Q3 of the adjacent same color area is Q1-Q3. When this is printed in the normal color mode, the color Q3 of the adjacent same color area is originally the first color. Since it is in the area 61, it does not change as it is, and the color Q1 of the noticed same color area in the extended color area 63 becomes the color Q1 'reproduced in the first color area 61, and the noticed same color area and the adjacent same color area The color difference is Q1'-Q3. In this way, when the color difference (Q1-Q3) in the full color mode is a small color difference that a person originally feels slightly, the color difference (Q1'-Q3) cannot be recognized by a person in the normal color mode. turn into. In other words, subtle color differences that are recognizable in the full color mode are no longer reproduced in the normal color mode, so using the full color mode improves image quality compared to using the normal color mode, and enables the full color mode. The profit to use appears.

  As described above, in the present embodiment, whether or not to form an image in the full color mode in which the reproducible color area is expanded is determined based on the color distribution of the image to be printed. Therefore, the normal color mode and the full color mode are determined. Which one should be used can be automatically selected appropriately.

  FIG. 15 shows the relationship between the color difference ΔE and the human sense for the color difference. The threshold value in step S267 in FIG. 14 may be set to a color difference that is “slightly felt”, for example. In addition, the predetermined value for determining the same color area in step S261 may be set to 0 or a color difference of “feeling faint”.

FIG. 16 shows a color difference calculation process. For each component (a, b, L) of the Lab value, differences (Δa, Δb, ΔL) between the target pixel and its surrounding pixels are obtained (step S281), and the color difference ΔE = (Δa ² × Δb ² × ΔL ² ) × 1/2 (step S282). Although the above calculation simply calculates the difference between two colors (distance in the color space), the absolute value of the square root of (Δa ² × Δb ² × ΔL ² ) may be calculated as ΔE. It doesn't matter.

  FIG. 17 shows details of the printing process (step S209 in FIG. 11). In the printing process, when the operation mode determined in the mode determination process is the full color mode (step S301; Yes), the CPU 11 uses the original image data (the image data input in step S221 in FIG. 12) as the basic image forming unit. 32, the special color image forming unit 33, and the black image forming unit 34 are used to convert to print data corresponding to a reproducible color space (step S302). For example, pixels in a color region (first color region 61) that can be reproduced by the basic image forming unit 32 and the black image forming unit 34 are represented by data of C color, M color, Y color, and K color. The pixels in the extended color area 63 are converted so as to be represented by high saturation cyan (C ′), high saturation magenta (M ′), high saturation yellow (Y ′), and K color data. In this way, the amount of high-saturation toner used can be reduced.

  Subsequently, the printing unit 26 is set to the full color mode (step S303), and the printing unit 26 is caused to perform printing related to the converted print data. The printing is performed according to various parameters (settings relating to paper size, printing method (single-sided, double-sided, etc.), post-processing, etc.) sent together with the print data. When the full color mode is set, the printing unit 26 performs printing using the basic image forming unit 32, the spot color image forming unit 33, and the black image forming unit 34 (step S304).

  Specifically, as shown in FIG. 4, the basic image forming unit 32, the special color image forming unit 33, and the black image forming unit 34 are set at contact positions at which the photosensitive drum 41 contacts the intermediate transfer belt 31, respectively. The image unit 32, the special color image forming unit 33, and the black image forming unit 34 are driven to perform printing. At this time, the CPU 11 gives print data for C color to the writing unit 43 of the basic color C image forming unit 32c of the basic image forming unit 32, and prints for M color to the writing unit 43 of the basic color M image forming unit 32m. Data is provided, and print data for Y color is provided to the writing unit 43 of the basic color Y image forming unit 32y. Also, print data for high saturation cyan (C ′) color is given to the writing unit 43 of the special color C image forming unit 33c ′ of the special color image forming unit 33, and high saturation magenta (M) is supplied to the writing unit 43 of the special color M image forming unit 33m ′. ') The print data for the color is given, and the print data for the high saturation yellow (Y') color is given to the writing unit 43 of the special color Y image forming unit 33y '. In addition, printing is performed by giving print data for K color to the writing unit 43 of the black image forming unit 34.

  Thereafter, the developing device usage limit count processing is performed (step S309), and the processing is terminated. Details of the developing device usage limit count processing will be described later.

  When the mode determined in the mode determination process is the normal color mode (step S301; No), the original image data (the image data input in step S221 in FIG. 12) is converted into the basic image forming unit 32 and the black image forming unit 34. Are converted into print data corresponding to a reproducible color space (first color region 61) (step S305). Here, conversion is performed so as to be represented by data of C color, M color, Y color, and K color.

  Subsequently, the printing unit 26 is set to the normal color mode (step S306), and the printing unit 26 is caused to perform printing related to the converted print data. The printing is performed according to various parameters (settings relating to paper size, printing method (single-sided, double-sided, etc.), post-processing, etc.) sent together with the print data. When the normal color mode is set, the printing unit 26 performs printing using the basic image forming unit 32 and the black image forming unit 34 without using the special color image forming unit 33. That is, as shown in FIG. 5, the special color image forming unit 33 is retracted to the retracted position and is stopped (step S307), and the basic image forming unit 32 and the black image forming unit 34 are respectively connected to the photosensitive drum 41 and the intermediate transfer belt 31. The basic image forming unit 32 and the black image forming unit 34 are driven to perform printing (step S308).

  At this time, the CPU 11 gives print data for C color to the writing unit 43 of the basic color C image forming unit 32c of the basic image forming unit 32, and prints for M color to the writing unit 43 of the basic color M image forming unit 32m. Data is provided, and print data for Y color is provided to the writing unit 43 of the basic color Y image forming unit 32y. In addition, printing is performed by giving print data for K color to the writing unit 43 of the black image forming unit 34.

  Thereafter, the developing device usage limit count processing is performed (step S309), and the processing is terminated.

  As described above, in the normal color mode, since color printing is performed without using the special color image forming unit 33, the maintenance cycle of the special color image forming unit 33 can be extended, and waste, energy and consumption of high-saturation toner can be increased. Can be suppressed. In the normal color mode, the special color image forming unit 33 is retracted to the retracted position, so that unnecessary toner can be prevented from adhering to the intermediate transfer belt 31.

  FIG. 18 shows details of the developing device usage frequency counting process (step S309 in FIG. 17). Since the basic image forming unit 32, the special color image forming unit 33, and the black image forming unit 34 each have a limit on the number of times of use, the number of times of each operation is counted. Is displayed on the display unit 23 to prompt the user for replacement maintenance.

  Specifically, the CPU 11 updates the values of the developer use frequency counters corresponding to the image forming units 32 and 33 and the black image forming unit 34 used at the time of printing (step S321). More specifically, when printing is performed in the full color mode, the values of the developer usage frequency counters corresponding to the basic image forming unit 32, the spot color image forming unit 33, and the black image forming unit 34 are respectively incremented by one. When printing is performed in the normal color mode, the values of the developer use frequency counters corresponding to the basic image forming unit 32 and the black image forming unit 34 are respectively incremented by one.

  It is checked whether or not the value of the developing device usage frequency counter corresponding to the spot color image forming unit 33 is equal to or greater than the predetermined use limit number of times, and if it is equal to or greater than the use limit number of times (step S322; Yes), A warning is displayed that the unit 33 has reached the limit of use (step S323). Thereafter, when the special color image forming unit 33 is maintained (for example, replaced) and the value of the corresponding developing device usage frequency counter is reset (step S324; Yes), the previous warning display is deleted (step S331).

  If the value of the developer usage frequency counter corresponding to the spot color image forming unit 33 is not equal to or greater than the usage limit number (step S322; No), then the value of the developer usage frequency counter corresponding to the basic image forming unit 32 is a predetermined value. It is checked whether or not the usage limit number is exceeded. If the usage limit number is exceeded (step S325; Yes), a warning is displayed on the display unit 23 that the basic imaging unit 32 has reached the usage limit number (step S326). . Thereafter, when the special color image forming unit 33 is maintained (for example, replaced) and the value of the corresponding developing device usage frequency counter is reset (step S327; Yes), the previous warning display is deleted (step S331).

  When the value of the developing device usage frequency counter corresponding to the basic image forming unit 32 is not equal to or greater than the usage limit number (step S325; No), the value of the developing device usage frequency counter corresponding to the black image forming unit 34 is subsequently set to a predetermined value. It is checked whether or not the usage limit number is exceeded. If the usage limit number is exceeded (step S328; Yes), the display unit 23 displays a warning that the black image forming unit 34 has reached the usage limit number (step S329). . Thereafter, when the special color image forming unit 33 is maintained (for example, replaced) and the value of the corresponding developing device usage frequency counter is reset (step S330; Yes), the previous warning display is deleted (step S331).

  In addition, it is checked in parallel whether or not the value of each developer use frequency counter corresponding to the basic image forming unit 32, the special color image forming unit 33, and the black image forming unit 34 has reached the use limit number. The warnings for all the units and the like may be displayed on the display unit 23 in parallel at the same time.

  FIG. 19 illustrates an example of a state in which the above warning display is performed on the display unit 23 of the operation panel of the image forming apparatus 10.

  Next, a modified example related to the printing process will be described.

  FIG. 20 shows the flow of printing processing in the modification. The same steps as those in FIG. 17 are denoted by the same step numbers. In the modification, when printing in the normal color mode, data indicating no image (data “0” in this case) is given to the special color image forming unit 33. In this way, even if the special color image forming unit 33 is driven, image formation by the special color image forming unit 33 is not performed. Therefore, the spot color image forming unit 33 is driven at the contact position (the same operation state as in the normal color mode), and it is not necessary to retract or pause the retracted position. Of course, it may be retracted to the retracted position.

  The operation in the full color mode is the same as in FIG. In the case of the normal color mode (step S301; No), the original image data (image data input in step S221 in FIG. 12) can be reproduced using the basic image forming unit 32 and the black image forming unit 34. The print data corresponding to the color space is converted into the print data (high-saturation cyan (C ′) color print data, high-saturation magenta (M ′) color print data, high-saturation yellow ( Y ′) color print data) are all set to “0” (step S341). After that, the process proceeds to step S303, and the same operation as in the full color mode is performed. As a result, data “0” is given to each of the image forming units 33m ′, 33c ′, 33y ′ of the special color image forming unit 33. Therefore, even if the special color image forming unit 33 is driven in the contact position, the special color image forming unit 33 is driven. An image is not formed by the unit 33.

  Next, mode determination processing using a method different from that in FIG. 14 will be described. This process is performed on the Lab data obtained by the process of FIG.

  In FIG. 14, the determination is made in units of the same color area, but in this process, the determination is made in units of pixels. That is, for each pixel having a color in the extended color region 63, a color difference with a surrounding pixel (for example, four surrounding pixels of the target pixel) is calculated, and the color difference is 0 or larger than a predetermined threshold value. And the number of pixels that are greater than or equal to 0 and less than or equal to the threshold are counted. If the former pixel ratio exceeds a predetermined reference value, the determination result is a full color mode, and if the ratio is less than the reference value, the determination is made. The result is the normal color mode.

  Specifically, one unchecked pixel is extracted from the image to be processed (step S401), and it is checked whether the color of the pixel is a color in the extended color area 63 (step S402). If the color is not within the extended color area 63 (step S402; No), the process proceeds to step S407. If the color is within the extended color region 63 (step S402; Yes), the color difference from the surrounding pixels is calculated (step S403). If the calculated color difference is greater than 0 and less than or equal to the predetermined threshold (step S404; Yes), the color difference minute count value is incremented by 1 (step S406) and the process proceeds to step S407. If the calculated color difference is 0 or exceeds the threshold (step S404; No), the color difference large count value is incremented by 1 (step S405), and the process proceeds to step S407.

  In step S407, it is checked whether or not the above process has been completed for all pixels. If all the pixels have not been completed (step S407; No), the process returns to step S401 and continues. If all the pixels are completed (step S407; Yes), the ratio of the color difference large count value to the total value (all count values) of the color difference large count value and the color difference minute count value is calculated (step S408). When this ratio exceeds a predetermined reference value (for example, 99%) (step S409; Yes), the determination result is set to the normal color mode (step S411), and when the calculated ratio is equal to or less than the reference value (step S409). No), the determination result is set to the full color mode (step S410), and the process is terminated.

  That is, a pixel having a color in the extended color area 63 and having a slight color difference (not 0) from the surrounding pixels is a predetermined ratio among pixels having a color in the extended color area 63 If there is more than one, it is determined that it is necessary to reproduce the subtle color difference between the pixel having the color in the extended color region 63 and the adjacent pixel, and the full color mode is selected. . For the pixels having the color in the first color area 61, the color can be reproduced by the basic image forming unit 32 regardless of the color difference from the surrounding pixels. Only the pixels that have the pixel (only the pixels that become Yes in step S402) are the pixels to be determined.

  Even in the above method, it is possible to appropriately determine whether the normal color mode or the full color mode is set.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  For example, in FIG. 14, the full color mode is selected when there is at least one same color area (specific image area) whose color difference is equal to or less than the threshold value, but the full color mode is selected when there is a predetermined amount or more of the specific image area. You may make it do. In addition to the case where there is at least one specific image region, the predetermined amount or more may be, for example, a case where the ratio (area ratio) of the specific image region to the entire input image is a predetermined reference value or more, or an extended color region The ratio of the specific image area to the entire image area having the color of 63 may be a reference value or more.

  In the processing of FIG. 14, the color difference between the same color area having the color of the extended color area 63 and the same color area adjacent to the extended color area 63 is obtained. You may make it ask.

  Further, another determination criterion may be adopted when the mode is determined by the method of FIG. For example, instead of the determination in step S409, when the ratio of the color difference minute count value to the total number of pixels of the input image exceeds the reference value, the full color mode is selected, or pixels having colors in the extended color area 63 When the ratio of the color difference minute count value to the number exceeds the reference value, the full color mode may be selected.

  Further, the full color mode may be selected when a predetermined amount or more of pixels having colors in the extended color area 63 exist, and the normal color mode may be selected when the number of pixels is less than the predetermined amount. That is, the mode determination may be performed based on whether or not there is a predetermined amount or more of pixels in a color region that cannot be reproduced unless the special color image forming unit 33 is used together. The case where the predetermined amount or more exists may be, for example, a case where the ratio of the pixels having the color in the extended color region 63 to the entire input image is equal to or more than the reference value.

  In the embodiment, the color material used in the special color image forming unit 33 has the same hue and the same hue as the color material used in the basic image forming unit 32, but the hue may be different. However, both hue and saturation may be different. In any case, any color material can be used as long as it can be used in combination with the basic image forming unit 32 as compared with a case where a color region that can be reproduced is not used together.

  In the embodiment, the color difference is obtained based on the data converted into the Lab value. However, the color difference may be obtained by conversion into another color system.

  In the embodiment, the basic color C image forming unit 32c, the basic color M image forming unit 32m, and the basic color Y image forming unit 32y are housed in one basic image forming unit 32, and the special color C image forming unit 33c ′ and the special color. Although the M image forming unit 33m ′ and the special color Y image forming unit 33y ′ are accommodated in one special color image forming unit 33, each image forming unit is individually arranged along the intermediate transfer belt 31 without being unitized. It may be configured as follows. In this case, it is preferable that the displacement to the contact position and the retracted position can be performed for each image forming unit.

  The present invention is not limited to printing by the PC print function, and can also be applied to color copying. In color copying, color image data (for example, RGB format) obtained by reading an original with the image reading unit @ 22 may be stored as image data in step S204 in FIG. The operations after step S205 are the same as in the case of PC printing.

  The image forming apparatus 10 is not limited to a digital multi-function peripheral, and may be a copier, a printer, or the like as long as the apparatus has printing. Further, the color material is not limited to toner, and may be ink.

2 ... Network 10 ... Image forming apparatus 11 ... CPU
DESCRIPTION OF SYMBOLS 12 ... Memory 13 ... Hard disk apparatus 14 ... Communication I / F part 21 ... Automatic document conveying apparatus 21a ... Document loading tray 21b ... Document discharge tray 22 ... Image reading part 23 ... Display part 24 ... Operation part 25 ... Paper feed part 25a ... paper feeding cassette 26 ... printing unit 27 ... post-processing unit 27a ... paper discharge tray 28 ... fixing unit 29 ... transport unit 30 ... image forming unit 31 ... intermediate transfer belt 32 ... basic image forming unit 32c ... basic color C image forming Part 32m ... Basic color M image forming part 32y ... Basic color Y image forming part 33 ... Special color image forming unit 33c '... Special color C image forming part 33m' ... Special color M image forming part 33y '... Special color Y image forming part 34 ... Black Image forming section 35 ... transfer section 41 ... photosensitive drum 42 ... developing device 43 ... writing section 50 ... terminal device 51 ... CPU
52 ... Memory 53 ... Hard disk device 54 ... Communication I / F unit 55 ... Display unit 56 ... Operation unit 61 ... First color region 62 ... Special color region 63 ... Extended color region 71 ... Printer driver screen 72 ... Property button 73 ... OK button 75 ... Property screen

Claims (9)

A basic color material set composed of a plurality of color materials and capable of reproducing the first color region, and a combination of the basic color material set, the first color region is included and is wider than the first color region. Color in either of a full color mode using at least one special color material capable of reproducing two color regions, and a normal color mode using the basic color material set without using the special color material An image forming unit for forming an image;
Based on the color distribution of the input image, it is selected whether the image forming operation related to the input image is performed in the full color mode or the normal color mode, and the image forming operation related to the input image is performed in the selected mode. An image forming apparatus comprising: a control unit that causes the image forming unit to perform. The control unit performs color conversion on the input image so as to correspond to the second color area, and divides the image after the color conversion into image areas where pixels in the same color or a predetermined approximate color range are continuous. In this case, there is a predetermined amount or more of a specific image area that does not enter the first color area but enters the second color area and has a color difference with a neighboring image area that is not more than a predetermined value. The image forming apparatus according to claim 1, wherein the full color mode is selected when the image is to be displayed. A basic color material set composed of a plurality of color materials and capable of reproducing the first color region, and a combination of the basic color material set, the first color region is included and is wider than the first color region. Color in either of a full color mode using at least one special color material capable of reproducing two color regions, and a normal color mode using the basic color material set without using the special color material An image forming unit for forming an image;
When the input image is color-converted so that the input image corresponds to the second color area, and the color-converted image is divided into image areas in which pixels in the same color or a predetermined approximate color range are continuous In addition, there is a predetermined amount or more of a specific image region that is a color image region that does not enter the first color region but enters the second color region and has a color difference with a neighboring image region that is equal to or less than a predetermined value. If the image is an image, the image forming unit performs the image forming operation related to the input image in the full color mode, and if the specific image area is an image that does not exist in the predetermined amount or more, the image forming operation related to the input image is performed. An image forming apparatus, wherein the image forming unit performs an operation in the normal color mode. 4. The image forming apparatus according to claim 2, wherein the case where the specific image area exists in a predetermined amount or more is a case where a ratio of the specific image area to the entire input image is a reference value or more. The control unit performs color conversion of the input image so as to correspond to the second color area, and enters the second color area without entering the first color area in the color-converted image. The image forming apparatus according to claim 1, wherein the full color mode is selected when a predetermined number or more of color pixels are present. The image forming according to any one of claims 1 to 5, wherein the special color material is a color material having the same hue and high saturation as the color material constituting the basic color material set. apparatus. The color material constituting the basic color material set and the special color material are toners,
7. The basic color material set is composed of cyan toner, magenta toner, yellow toner, or black toner. The image forming apparatus according to one item. The image forming unit includes a developing unit that develops toner of the color for each color of the color material and the special color material constituting the basic color material set,
When forming an image in the full color mode, use a developing device corresponding to the color material constituting the basic color material set and a developing device corresponding to the special color material,
When developing an image in the normal color mode, a developing device corresponding to a color material constituting the basic color material set is used without using a developing device corresponding to the special color material. 8. The image forming apparatus according to 7. 8. The image forming unit according to claim 1, wherein when the image is formed in the normal color mode, data indicating no image is given to the image forming unit as image data corresponding to the color of the special color material. The image forming apparatus according to claim 1.

Images