JP5589700B2 - Image processing apparatus, image forming apparatus, image processing method, image processing program, and recording medium - Google Patents

Description

  The present invention relates to an image processing apparatus, an image forming apparatus, an image processing method, an image processing program, and a recording medium, and more particularly, to an image processing apparatus, an image forming apparatus, and an image processing that perform image processing with clear toner added to an image. The present invention relates to a method, an image processing program, and a recording medium.

  In recent years, image forming apparatuses such as copying apparatuses and composite apparatuses have been demanded to improve the quality of output images, and toners of four reference colors of C (cyan), M (magenta), Y (yellow), and K (black) are used. In addition to (developer), special color toner (hereinafter referred to as clear toner) such as transparent toner and white toner is added to form an image with five or more colors of toner, thereby improving the image quality. It has been broken.

  In addition, today, in order to save resources, material-saving image formation (for example, toner save printing) in which image formation materials such as toner are reduced to form an image has been performed. If the image is formed by reducing the number of image forming materials, the appealing effect, which is the power to attract the person who sees the formed image, and the distinguishability from the surrounding image are reduced. The appeal effect here refers to an effect that attracts the line of sight of the person who sees the formed image.

  Conventionally, the toner amount per unit area of the transparent image to be formed on the recording material is set according to the designated image forming mode among the transparent image forming mode having a high glossiness and the transparent image forming mode having a low glossiness. Thus, a technique for changing the glossy visibility of a transparent image has been proposed (see Patent Document 1).

  In other words, this conventional technology, for example, by performing toner save printing, puts clear toner (particularly, transparent toner) on the character area where the appeal effect and discriminating ability are reduced, so that the glossy visibility of the character area is improved. We are trying to improve.

  However, in the prior art described in the above publication, the clear toner is simply placed on the character area in order to improve the appeal effect and the discriminability of the character. In other words, the clear toner is placed on the sheet, and the readability of fine characters is reduced.

  Accordingly, the present invention provides an image processing apparatus, an image forming apparatus, an image processing method, and an image processing that perform image processing with the addition of clear toner that can improve appealability while improving legibility even for fine characters. The object is to provide a program and a recording medium.

In order to achieve the above object, the present invention provides an output mode detecting means for detecting whether or not an image data output mode is a character document mode, and the image data output mode is a character document mode. Character pixel determining means for determining whether or not each pixel data of the image data is character pixel data, and a character area for determining the character area size for each character area based on the determination result of the character pixel determining means A plurality of types of image processing including size determination means and clear toner-attached image data generation processing for generating clear toner-attached image data for forming an image to which the clear toner is added as an output image of the image data. And the character region size determining unit determines at least the character region into three types of large, medium, and small character sizes. When the character size is determined to be small, the image processing means determines image processing content that prohibits the clear toner-added image data generation processing, and the output mode is the character document mode. Otherwise, the image processing apparatus that determines the clear toner-added image data generation process is characterized.

According to the present invention , appealing effect and legibility can be improved by not applying clear toner to small size characters .

1 is a block configuration diagram of an MFP to which a first embodiment of the present invention is applied. FIG. FIG. 3 is a block configuration diagram of a read image data processing unit. FIG. 3 is a block diagram of a color conversion & clear toner application processing unit. The block diagram of a plotter image data processing part. 10 is a flowchart showing clear toner-added image data generation processing. Explanatory drawing of the character size judgment method. The figure which shows an example at the time of performing the edge enhancement of a character. Explanatory drawing of a thick line process. Explanatory drawing of a character expansion process. Explanatory drawing in the case of enlarging only a medium-sized character. FIG. 10 is a block configuration diagram of a read image data processing unit of an MFP according to a second embodiment. The block block diagram of a color difference calculation process part. Explanatory drawing of how to obtain | require the color difference of a character and a background. 9 is a flowchart illustrating clear toner-added image data generation processing based on character size and color difference. 15 is a flowchart showing processing subsequent to FIG. The figure which shows an example when there exists a white character on the black ground. The figure which shows the relationship between a user setting, a color difference, and a toner provision amount. The figure which shows an example in case a black character exists on a gray ground. The figure which shows an example when there exists a blue character on the cyan ground. Explanatory drawing of the hue adjustment method.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 10 are diagrams showing a first embodiment of an image processing apparatus, an image forming apparatus, an image processing method, an image processing program, and a recording medium according to the present invention. FIG. 1 shows an image processing apparatus according to the present invention, 1 is a block configuration diagram of an MFP (Multi Functional Products) 1 to which an image forming apparatus, an image processing method, an image processing program, and a recording medium according to a first embodiment are applied.

  In FIG. 1, an MFP (image forming apparatus) 1 includes a reading unit 2, a read image data processing unit 3, a bus control unit 4, a plotter image data processing unit 5, a plotter I / F unit 6, a plotter unit 7, an HDD (hard disk). ) 8, CPU (Central Processing Unit) 9, memory 10, SB (South Bridge) 11 and ROM (Read Only Memory) 12, operation display unit 13, line I / F unit 14, external I / F unit 15, etc. The CPU 9 and the SB 11 are connected by an expansion bus 16.

  The reading unit 2 includes, for example, a line image sensor using a CCD (Charge Coupled Device), an analog / digital (A / D) conversion circuit, and a drive circuit for driving these, and generally includes an ADF. Yes. A plurality of documents are set in the ADF, and the ADF feeds the set documents one by one to the document reading position of the reading unit 2. The reading unit 2 performs main scanning and sub-scanning on the document conveyed from the ADF, reads an image from the density information of the document with a predetermined resolution, and generates image data of each RGB predetermined bit (for example, 8 bits each). And output to the read image data processing unit 3. The reading unit 2 is not limited to the one using a CCD, and may be one using a CIS (Contact Image Sensor), a CMOS (Complementary Metal Oxide Semiconductor), or the like.

  The read image data processing unit (image processing apparatus) 3 performs a process for unifying the digital image data from the reading unit 2 to a predetermined characteristic. The unified characteristics of the read image data processing unit 3 are characteristics suitable for changing the output destination when image data is stored in the MFP 1 and reused. For example, the operation mode of the MFP 1 is a copy mode. In the CMYK format + transparent toner (also referred to as clear toner), the MFP is in the RGB format when the operation mode of the MFP is a scanner delivery mode for delivering a read image.

  The bus control unit 4 controls a data bus for exchanging various data such as image data and control commands necessary in the MFP 1 and has a bridge function between a plurality of types of bus standards. In the MFP 1 of this embodiment, the bus control unit 4 is connected to the read image data processing unit 3, the plotter image data processing unit 5, and the CPU 9 via a PCI (Peripheral Component Interconnect) -Express bus, and is connected to the HDD 8 via an ATA bus. Thus, an ASIC (Application Specific Integrated Circuit) is formed.

  The plotter image data processing unit 5 applies to the digital image data unified to the characteristics predetermined by the read image data processing unit 3 and the image data input through the line I / F unit 14 or the external I / F unit 15. Then, image adjustment / processing and image processing suitable for the output destination designated by the user are performed.

  The HDD 8 is a hard disk of a large-capacity storage device that is also used in ordinary personal computers and the like, and mainly stores digital image data and incidental information (image related information) of the image data. The HDD 8 of this embodiment uses an ATA bus-connected hard disk that is standardized by expanding IDE (Integrated Development Environment). Note that the large-capacity storage device is not limited to the HDD 8, and for example, a silicon disk using a flash memory whose capacity has been increased recently may be used.

  A CPU (image processing control means) 9 is a microprocessor that controls the entire MFP 1. In this embodiment, an integrated CPU in which a predetermined peripheral function is added to a CPU core that has become widespread in recent years is used. This integrated CPU is a CPU in which a connection function with a general-purpose standard I / F and a bus connection function using a crossbar switch are integrated.

  The memory 10 stores data to be temporarily exchanged and the CPU 9 controls the MFP 1 in order to absorb a speed difference when bridging between a plurality of types of bus standards and a processing speed difference between connected components themselves. In addition, it is a volatile memory that temporarily stores programs and intermediate processing data. Since high-speed processing is required for the CPU 9, the system is activated by a boot program stored in the ROM 12 during normal activation, and thereafter, the processing is performed by a program developed in the memory 10 that can be accessed at high speed. In the MFP 1 of this embodiment, a DIMM (Dual Inline Memory Module) that is standardized and used in a personal computer is used as the memory 10.

  When the plotter I / F unit 6 receives digital image data composed of CMYK and CMYK + clear toner (hereinafter referred to as CMYK + α as necessary) sent via the general-purpose standard I / F integrated with the CPU 9, A bus bridge process for outputting the image data to the dedicated I / F of the plotter unit 7 is performed, and a PCI-Express bus is used as the general-purpose standard I / F.

  When the plotter unit 7 receives CMYK digital image data, the plotter unit 7 records and outputs an image of the image data on a recording material by an electrophotographic process using a laser beam. The plotter unit 7 has a function of plotting five colors of CMYK + α. As the plot + fixer, the CMYK 4 plate and clear toner (mainly transparent toner) may be separated.

  The SB 11 is one of chip sets used for a personal computer, and is a general-purpose electronic device called a South Bridge. SB11 is a general-purpose circuit that bridges a bus that is often used when constructing a CPU system that includes a general-purpose standard expansion bus 16 that is mainly PCI-Express and an ISA (Industrial Standard Architecture) bridge. The ROM 12 is bridged.

  The ROM 12 stores a basic program of the MFP 1, a program such as an image processing program for executing an image processing method of the present invention to be described later, and necessary system data, and the CPU 9 stores the memory 10 based on the program in the ROM 12. Is used as a work memory while controlling each part of the MFP 1 to execute basic operation control of the MFP 1 and image processing to be described later.

  The operation display unit (clear toner processing selection means) 13 is a part that performs an interface to the user, and includes a display such as an LCD (Liquid Crystal Display) and a key switch. The operation display unit 13 is connected to the CPU 9 via the expansion bus 16 that is a PCI-Express bus, displays various states and operation methods of the MFP 1 on the display under the control of the CPU 9, and includes keys from the user. Detects switch input operations. In particular, the operation display unit 13 performs an operation of selecting an image data output mode (photo original mode, text original mode, etc.). The CPU 9 and the operation display unit 13 function as output mode detection means as a whole.

  The line I / F unit 14 connects the expansion bus 16, which is a PCI-Express bus, with a telephone line so that various data can be exchanged via the telephone line of the MFP 1, for example, facsimile communication with an external facsimile apparatus FX. The image data is input / output from / to the external facsimile machine FX.

  The external I / F unit 15 connects the expansion bus 16 which is a PCI-Express bus and the external device GS, and exchanges various data with the external device GS. The external I / F unit 15 is connected to a network such as Ethernet (registered trademark), for example, is connected to an external device GS on the network, and inputs / outputs image data to / from the external device GS.

  The external device GS is, for example, a personal computer, and the user uses various kinds of MFP 1 via the external I / F unit 15 using application software and drivers installed in the external device GS such as a personal computer. Control and input / output of image data can be performed.

  The read image data processing unit 3 has a block configuration as shown in FIG. 2, and includes an image area separation & character size determination processing unit 21, a background removal processing unit 22, a γ conversion unit 23, an isolated point removal processing unit 24, A filter processing unit 25, a scaling processing unit 26, a color conversion & clear toner application processing unit 27, and the like are provided. The read image data processing unit 3 receives the image data from the reading unit 2 as input image data to the image area separation & character size determination processing unit 21, unifies the input image data into predetermined characteristics, and performs bus control. Send to part 4.

  The image area separation & character size determination processing unit (character pixel determination unit, character region size determination unit) 21 determines whether the RGB image data received from the reading unit 2 is a character or a pattern (halftone dot) for each pixel. When the character is recognized as a character, the character size is classified based on a plurality of threshold values.

  The background removal processing unit 22 calculates the background portion of the RGB image data received from the reading unit 2 while following each line, and performs processing for removing an appropriate background value. In this background processing, the background removal processing unit 22 exhibits an effect of outputting not only a normal white paper original but also a background such as newspaper or colored paper and outputting it as a pure white original.

  The γ conversion unit 23 performs γ conversion (gamma conversion processing) on the digitized input image data input from the reading unit 2 to obtain a predetermined brightness characteristic, for example, brightness. Convert to linear characteristics. In particular, the γ conversion unit 23 performs gradation correction, gray balance correction, and the like.

  The isolated point removal processing unit 24 detects and deletes isolated points in the image data.

  The filter processing unit 25 improves the sharpness in the character part of the RGB image data according to the separation information obtained by the image area separation process on the γ-corrected input image data, and the pattern of the RGB image data. The part (halftone dot part) performs a smoothing process and performs a filter process to improve smooth gradation.

  The scaling processing unit 26 performs conversion (particularly enlargement processing) of the size (resolution) of the image data input from the reading unit 2 and thickening processing for thickening the character line.

  The color conversion & clear toner application processing unit 27 has a block configuration as shown in FIG. 3, and includes a hue division masking processing unit 31, a three-dimensional LUT processing unit 32, a UCR / UCA processing unit 33, and a clear toner application processing unit 34. It has.

  The color conversion & clear toner application processing unit 27 uses the hue division masking processing unit 31 to convert the RGB signal input from the scaling processing unit 26 into a previously unified color space, for example, Adobe in which the color space is defined by Adobe. The color space is converted into a color space such as RGB, and the three-dimensional LUT processing unit 32 converts the color space into a color space suitable for the output format by nonlinear conversion. For example, the three-dimensional LUT processing unit 32 converts RGB data into 8 bits for each CMYK in the copy mode.

  The UCR (Under Color Removal) / UCA (Under Color Addition) processing unit 33 performs black generation and then uses the character size information obtained by the image area separation & character size determination processing unit 21 to generate the black ink. Based on this, the application amount of the clear toner amount is obtained. The clear toner application amount may be based on an instruction from the operation display unit 13 or the external device GS by the user of the MFP 1 or may be determined by the MFP 1 itself. For example, when the user selects a photo document on the operation display unit 13, if the MFP 1 itself is a photograph, it is determined that the unevenness of the toner is eliminated, and that the output image looks more beautiful when the entire image has a uniform glossiness. The clear toner amount is determined so as to eliminate the toner. Further, when determining the clear toner amount, it is necessary to pay attention to the total amount restriction amount of CMYK + α. However, if the fixing device is provided separately from the CMYK for the clear toner or if the MFP 1 fixes once with the CMYK and then fixes the clear toner separately, the CMYK total amount restriction and clear Since the total toner amount regulation can be handled independently and the amount of each toner can be increased, the degree of freedom is increased. In the present invention, it is possible to apply both fixing once and fixing twice. In addition, when a watermark, a security mark, or the like is instructed by the user, the UCR / UCA processing unit 33 determines the clear toner amount of each pixel according to the instruction.

  At least the γ conversion unit 23, the filter processing unit 25, the scaling processing unit 26, and the color conversion & clear toner application processing unit 27 perform gamma conversion processing, filter processing, thickening processing, enlargement processing, and color conversion processing as a whole. It functions as an image processing means to perform.

  The plotter image data processing unit 5 has a block configuration as shown in FIG. 4 and includes an edge extraction processing unit 41, a γ conversion processing unit 42, and a gradation processing unit 43.

  The edge extraction processing unit 41 separates an edge portion, a pattern portion, and the like from CMYK image data or CMYK + α image data, and mainly calculates a primary differential filter, a secondary differential filter, and the like in the up, down, left, and right diagonal directions, respectively. The maximum value is obtained as the edge amount.

  The γ conversion processing unit 42 performs γ conversion processing for matching CMYK image data or CMYK + α image data with the characteristics of the plotter unit 7 so that smooth gradation expression can be output. In this γ conversion processing, edge extraction is performed. The processing may be performed by switching the γ conversion according to the edge portion or the pattern portion extracted by the processing.

  The gradation processing unit 43 converts CMYK 8-bit data into a number of bits that can be reproduced by the plotter unit 7. In the MFP 1 of the present embodiment, conversion to 2 bits is performed. The gradation processing unit 43 performs error diffusion processing of pseudo halftone processing while changing the threshold values of the characters and the pattern portion based on the edge extraction processing result of the edge extraction processing unit 41 in processing with a normal character photo document. carry out. Note that the clear toner amount is preliminarily 2-bit data in the color conversion & clear toner application processing unit 27, so that it is not particularly necessary to perform processing in gradation processing.

  The MFP 1 includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-RW (Compact Disc Rewritable), and a DVD (Digital Video). An image processing program for executing the image processing method of the present invention recorded on a computer-readable recording medium such as a disk (SD), a secure digital (SD) card, or a magneto-optical disc (MO) is read into the ROM 12 or the HDD 8. By being introduced, it is constructed as an image forming apparatus equipped with an image processing apparatus that executes an image processing method including clear toner application that improves discrimination and appeal even with fine characters described later. This image processing program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark) or an object-oriented programming language, and is stored in the recording medium. Can be distributed.

  Next, the operation of this embodiment will be described. The MFP 1 of the present embodiment performs image processing with clear toner addition that improves appealability while improving legibility even for fine characters.

  In this embodiment, the clear toner-added image data generation process is performed in the copy operation. The clear toner-added image data generation is similarly performed in the print operation based on the print data from the external device GS. In this case, the printer driver of the external device GS or the CPU of the MFP 1 executes the clear toner application processing of the color conversion & clear toner application processing unit 27 of the read image data processing unit 3. Can respond. Further, the present invention is more effective when the amount of CMYK toner is not sufficient, but an appropriate effect can be obtained even when the amount of CMYK toner is sufficient. The toner amount is not mentioned. For example, when the amount of CMYK toner is not sufficient, for example, when the remaining amount of toner is low, but it is desired to complete the print processing of the current job without replenishing toner, high-speed output (particularly, first print) For this reason, there is a case where it is desired to suppress the toner amount and lower the fixing temperature or a toner save mode.

  First, a copy operation in the MFP 1 will be described. When the user sets a document on the document table of the reading unit 2 and inputs the setting of a desired mode and the like and the start of copying on the operation display unit 13, the operation display unit 13 displays information input by the user. Is converted into control command data and issued. The MFP 1 notifies the CPU 9 of the control command data issued by the operation display unit 13 via the PCI-Express bus, and the CPU 9 executes a copy operation process program in accordance with the copy start control command data to execute the copy operation. Perform necessary settings and operations in order.

  That is, the MFP 1 causes the reading unit 2 to scan a document under the control of the CPU 9 and sends the acquired 8-bit RGB digital image data to the read image data processing unit 3. However, the necessary correction processing is performed on the read image data, and is sent to the bus control unit 4 as CMYK + α (clear toner) image data.

  When receiving the CMYK + α image data from the read image data processing unit 3, the bus control unit 4 accumulates it in the memory 10 via the CPU 9.

  Next, the CPU 9 sends the CMYK + α image data stored in the memory 10 to the plotter image data processing unit 5 via the bus control unit 4.

  The plotter image data processing unit 5 performs gradation processing on the received CMYK + α image data for plotter output, converts it into CMYK + α data for plotter output, and passes it to the plotter unit 7 via the plotter I / F unit 6. Send it out.

  The plotter unit 7 outputs an image on a sheet using CMYK toner and clear toner based on the received CMYK + α image data, and generates a copy of the document.

  In the MFP 1, the read image data processing unit 3 performs the clear toner-added image data generation process in the copy process as shown in FIG. 5. That is, the read image data processing unit 3 first notifies the CPU 9 of information set by the copy start operation by the user on the operation display unit 13 in order to give an appealing effect to characters and improve legibility. Then, it is confirmed by the notification whether or not the character document mode is set (step S101).

  When NO in step S101, that is, when the document mode is not the character document mode, the read image data processing unit 3 puts clear toner on the color conversion & clear toner application processing unit 27 according to each mode. Clear toner imparted image data generation processing for generating clear toner imparted image data in which a clear toner imparting amount is set is performed (step S102). For example, in the photographic document mode, the read image data processing unit 3 eliminates toner irregularities, and the photographic image looks more beautiful when the entire image has a uniform gloss. The clear toner amount is determined so as to eliminate unevenness.

  If YES in step S101, that is, in the character document mode, after the image area separation & character size determination processing unit 21 of the read image data processing unit 3 determines whether each pixel is a character, The size of the area is determined (steps S103 and S105). The character size can be determined by detecting the number of points of the character by performing matching processing with the dictionary data using the OCR (Optical Character Reader) function. Various methods such as a method of setting the smallest value among these as the size can be used.

  For example, as shown in FIG. 6, in the case of the letter “H”, the minimum width of the main scanning (horizontal) pixel is the pixel area indicated by a or b in FIG. The minimum width is a pixel area indicated by c. Then, the image area separation & character size determination processing unit 21 compares the character size with two threshold values TH1 and TH2 for character size classification as shown below based on the minimum width of these pixel areas. As shown below, it is classified into three types of sizes, large, medium and small.

Large character size: Character size ≥ TH1
Medium character size: TH2 ≦ character size <TH1
Small character size: Character size <TH2
In the following description, the character size is described as being classified into large, medium, small, and three sizes. However, the number of character sizes is not limited to three, but four or more. There may be two.

  In the character original mode, the MFP 1 according to the present embodiment performs processing so as to improve the appeal and legibility of all characters existing in the original, but the appeal and legibility of all characters are improved. It is not limited to the processing method to be improved. For example, when there is a character portion in the manuscript that is particularly desired to improve the appeal, only the character portion is selected by the operation display unit 13 or the like. It is also possible to select a character part and perform the clear toner-added image data generation process described below for only the corresponding character part. In addition, as will be described later, a character having a color different from that of other characters such as red is automatically selected by the read image data processing unit 3 as an appealing target character, and a clear toner-added image data generation process described below is performed. You may do it.

  If YES in step S103, that is, if the character size is large, the image area separation & character size determination processing unit 21 transmits information indicating that the character size is large to each of the subsequent image processing modules 22 to 22. 27 together with the pixel data. In other words, the image area separation & character size determination processing unit 21 has separation data (data indicating any one of characters, white background, and design) and character size data (large, medium, or small) in addition to RGB 8-bit data. In addition, the image data is transmitted to each subsequent image processing module 22-27.

  In this case, the read image data processing unit 3 is basically a color conversion & clear toner application processing unit 27 that performs processing for improving appealability and legibility by placing clear toner on the entire character area. Then, the clear toner imparted image data generation process is terminated (step S104). Specifically, the read image data processing unit 3 uses the filter processing unit 25, and in the case of image data having a large character size, the edge portion is more than necessary even when the appealing property can be improved. Is not emphasized, that is, the edge enhancement filter is weakened. That is, when the edge portion is emphasized, as shown in FIG. 7, only pixels at the boundary portion between the background portion and the character portion are darkened, the inside of the character line is thinned, and there is a possibility that density unevenness occurs. The read image data processing unit 3 is a color conversion & clear toner application processing unit 27, in order to apply clear toner to image data having a large character size, α = 1 (α is 1 bit data). When the clear toner is applied, α = 1, and when not applied, α = 0) is transmitted to the bus control unit 4.

  If NO in step S103, that is, if the character size is not large, the read image data processing unit 3 checks whether the character size is medium (step S105), and if YES, that is, the character size. When the image size is medium size, information indicating that the character size is medium size is transmitted to each subsequent image processing module together with the pixel data, the enlargement processing unit 26 performs enlargement processing of the character area, and color conversion and clearing. The toner application processing unit 27 performs processing for improving appealability and legibility by placing clear toner on the remaining character area, and ends the clear toner application image data generation processing (step S106). That is, when the character size is medium, if the same processing as normal character data processing is performed, the clear toner may be applied over the background portion of the character, and the legibility may be deteriorated. Therefore, when the character size is medium, the read image data processing unit 3 first performs thickening processing and enlargement processing of the character data by the scaling processing unit 26. That is, for example, as shown in FIG. 8, when the character is “H”, the scaling processing unit 26 performs a thickening process for making the line larger (thicker), and makes it easier to place the clear toner. Further, the scaling processing unit 26 performs an enlargement process on the medium size character (for example, “A”) shown in FIG. 9A to a large size character as shown in FIG. 9B. In the thickening process of the character line, if the ratio of thickening the line is increased too much, the scaling processing unit 26 impairs the sharpness of the character or causes a non-edge part (for example, FIG. 9). Therefore, when the character size is “Small”, it is necessary to increase the thickness of the character line as described later. I can't do it. In addition, in the enlargement process of the character size, the enlargement / reduction processing unit 26 performs the enlargement process in consideration of the character size of the entire image because the balance of the text is lost if the character size is increased too much. It is. That is, in the case of a medium-sized character, as shown in FIG. 9A, since the area of the shaded portion surrounded by the character edge is small, most of the shaded portion is caused by the clear toner that protrudes from the character region due to plate misalignment. As shown in FIG. 9B, when the enlargement process is performed, the area of the shaded area where the clear toner is not applied increases, and the gloss between the shaded area and the character itself is increased. The difference can be made clear and the legibility can be improved.

  When the character size is originally “large” or when the character size of “medium” is “large”, as shown in FIG. 9B, even if the clear toner slightly protrudes in the background portion, Not all of the middle part of the character is painted, and because the character is large, the brightness difference is kept clear, so that appealability and legibility are not impaired, and by performing the above processing, Character quality can be improved.

  That is, when the read image data processing unit 3 determines whether or not there is a character area in the read image data processing unit 3 as shown in FIG. Thus, the character size is enlarged to make it easier to place clear toner, and the character size is increased to improve the brightness difference.

  If NO in step S105, that is, if the character size is a small size, the image area separation & character size determination processing unit 21 indicates that the character size is a small size by using each subsequent image processing module. Are transmitted together with the pixel data. When the character size is small, as described above, when clear toner is placed on the character portion, the clear toner is also placed on the background portion, and the readability of the character may be lowered. In view of this, the read image data processing unit 3 uses the γ conversion unit 23 to reduce the density of the background portion of the character to a lower level than usual in order to prevent a decrease in legibility and appeal of small size characters, and a filter processing unit. 25, the character portion emphasis filter is larger than normal, and the color conversion & clear toner application processing unit 27 changes the character color, that is, performs character color change processing and color conversion & clear toner application processing. The unit 27 performs processing (α = 0) for prohibiting application of clear toner (step S107).

  In other words, when the character size is small, the read image data processing unit 3 first uses the γ conversion unit 23 in the background portion of the small size character in order to improve the appeal and legibility of the small size character. The density is made smaller than usual, and the filter processing unit 25 makes the character part emphasis filter larger than usual. The read image data processing unit 3 further changes the character color by the color conversion processing of the color conversion & clear toner application processing unit 27. In the color conversion processing of the color conversion & clear toner application processing unit 27, basically, when the amount of toner is limited, the secondary color and the tertiary color are less likely to produce saturation. Therefore, by shifting the hue of the character color in the primary color direction and in the direction of the highly visible hue, the saturation is increased and the appeal is improved. For example, in the case of a red character, the appeal is improved by shifting the color of the small size character in the M (magenta) direction of the CMYK in the M (magenta) direction. The read image data processing unit 3 does not apply clear toner in terms of appeal and legibility in the clear toner application image data generation process of the color conversion & clear toner application processing unit 27 when the characters are small. Therefore, α = 0 is transmitted to the small-size character area, and image data is transmitted to the bus control unit 4. Thus, appealing effect and legibility can be improved by not applying clear toner to small size characters.

  However, in the filter processing of the filter processing unit 25, if the emphasis filter is made stronger than usual, particularly when the character becomes large, side effects become conspicuous as shown in FIG. 7, so that it can be used for all character sizes. is not. Further, since the character color is changed in the color correction processing of the color conversion & clear toner application processing unit 27, it is not faithful to the original, but the most important character appealing and legibility are improved. Can do.

  As described above, the MFP 1 according to the present embodiment detects whether the output mode of the image data is the character document mode. If the image data output mode is the character document mode, the MFP 1 uses character pixel data for each pixel data of the image data. Determine whether or not there is, determine the character area size for each character area, and generate clear toner-added image data that forms an image with clear toner applied as an output image of the image data for the image data In the case of performing a plurality of types of image processing including clear toner imparted image data generation processing, the clear toner imparted image data generation processing is performed when the output mode of the image data is other than the character document mode. If the output mode of the image data is the character original mode, the image data of the character area is converted into the image data of the character area based on the size of the character area size of the character area. And determine the contents of the image processing to apply to.

  Therefore, it is possible to perform image processing with the application of clear toner that can improve appealability while improving legibility even for fine characters.

  In addition, the MFP 1 according to the present embodiment determines the character area to have three types of character area sizes, large size, medium size, and small size, and the contents of the small size character area are used as the contents of the image processing performed on the character area. With respect to the image data, the γ conversion processing unit 23 reduces the background density, the filter processing unit 25 performs the enhancement filter processing, and the color conversion processing of the color conversion & clear toner application processing unit 27 performs character color conversion. The image processing contents that change processing and prohibit the clear toner-added image data generation processing are employed.

  Therefore, when the character size is small, the clear toner is not placed on the character region, so that it is possible to prevent the legibility from being deteriorated by applying the clear toner to the background portion of the character. It is possible to perform image processing for improving the appeal of small-size characters as compared to normal character data processing.

  Further, the MFP 1 according to the present embodiment causes the enlargement / reduction processing unit 26 to perform thickening processing as the content of the image processing performed on the image data of the medium-size character area. A character enlargement process is performed, and a color conversion & clear toner application processing unit 27 performs a clear toner application image data generation process.

  Therefore, when the character size is medium, the clear area is applied to the character area by placing the clear toner on the character area as it is. Can be prevented, and legibility can be improved.

  Further, the MFP 1 according to the present exemplary embodiment causes the filter processing unit 25 to perform weak edge enhancement filter processing as the content of the image processing performed on the image data of the large size character area, and the color conversion & clear toner application processing unit 27. Therefore, the image processing content for performing the clear toner-added image data generation processing is employed.

  Therefore, when the character size is large, by weakening the emphasis filter at the character outline, if the edge is simply emphasized with the emphasis filter, only the character outline will be noticeable and the character will become thinner. In addition to preventing density unevenness in the lines, the large size of the characters can improve the appeal of the characters by placing clear toner without straddling the background. .

  11 to 20 are diagrams showing a second embodiment of the image processing apparatus, the image forming apparatus, the image processing method, the image processing program, and the recording medium of the present invention. FIG. 11 shows the image processing apparatus of the present invention, FIG. 6 is a block configuration diagram of a read image data processing unit 50 of the MFP 1 to which an image forming apparatus, an image processing method, an image processing program, and a recording medium according to a second embodiment are applied.

  This embodiment is applied to the same MFP as the MFP 1 of the first embodiment. In the description of this embodiment, the same reference numerals are given to the same components as the MFP 1 of the first embodiment. The description thereof will be omitted and the description thereof will be omitted, and portions not shown will be described using the reference numerals used in the description of the first embodiment as they are as necessary.

  The MFP 1 of this embodiment has the same configuration as that of the MFP 1 of the first embodiment shown in FIG. 1, and the read image data processing unit 50 is configured as a block as shown in FIG.

  In FIG. 11, a read image data processing unit 50 includes an image area separation & character size determination processing unit 21, a color difference calculation processing unit 51, a background removal processing unit 22, a γ conversion unit 23, an isolated point removal processing unit 24, and a filter processing unit. 25, a scaling unit 26, and a color conversion & clear toner application processing unit 27.

  The image area separation & character size determination processing unit 21 is the same as in the first embodiment, but in this embodiment, the character size is set to “large” or “small” based on one threshold value TH. Classify into two character sizes.

  The color difference calculation processing unit (color difference detection means) 51 is configured as a block as shown in FIG. 12, and includes a line buffer 61, a character area labeling unit 62, a character color extraction unit 63, a character background color extraction unit 64, and a color difference calculation unit. 65, a color difference classification processing unit 66, and the like, and detects the magnitude of the color difference between the character area and the background area with respect to a predetermined threshold color difference.

  The line buffer 62 accumulates several hundred to several thousand lines of image data from the image area separation & character size determination processing unit 21, and the character area labeling unit 62 stores character area information for each pixel of the image data in the line buffer 61. Character area labeling is performed using.

  The character color extracting unit 63 obtains an average RGB value from the RGN value of each pixel of the character region that has been labeled by the character region labeling unit 62.

  As shown in FIG. 13, the character background color extraction unit 64 extracts several pixels around the character region to obtain an average RGB value, and the color difference calculation unit 65 calculates the average RGB value of the character region and the background portion. From the average RGB value, the color difference, mainly the difference in hue, is obtained. This method of obtaining the color difference may be a normal method of calculating the Euclidean distance in the Lab space by performing color conversion from RGB to Lab, or the hue from the relative difference between the R signal, G signal, and B signal. A method may be used in which the angle is calculated and the degree of the hue angle is determined by comparison.

  The color difference classification processing unit 66 compares the numerical value of the color difference obtained by the color difference calculation unit 65 with a predetermined threshold value, and determines whether the character color and the background color are similar colors.

  Referring back to FIG. 11 again, the read image data processing unit 50 includes a background removal processing unit 22, a γ conversion unit 23, an isolated point removal processing unit 24, a filter processing unit 25, a scaling processing unit 26, and a color conversion & clear toner. The application processing unit 27 is the same as in the first embodiment, but performs image processing and clear toner added image data generation processing based on the color difference and character size obtained by the color difference calculation processing unit 51.

  Next, the operation of this embodiment will be described. The MFP 1 according to this embodiment controls image processing and clear toner-added image data generation processing for characters based on not only the character size but also the color difference between the character color and the character background color.

  In this embodiment, the clear toner-added image data generation process is performed in the copying operation. The clear toner-added image data is similarly applied to the print operation based on the print data from the external device GS. Generation processing can be performed. In the following description, it is assumed that the output mode is the character document mode.

  In the copy process, as shown in FIG. 14, in the MFP 1, the read image data processing unit 3 performs a clear toner-added image data generation process based on the character size and the color difference. That is, the read image data processing unit 50 first notifies the CPU 9 of the information set by the copy start operation by the user on the operation display unit 13 in order to give an appealing effect to the characters and improve the legibility. When it is confirmed that the character manuscript mode is set by the notification, the image area separation & character size determination processing unit 21 determines whether each pixel is a character, and then determines the size of the character area (step) S201). The method for determining the character size is the same as in the first embodiment, but the image area separation & character size determination processing unit 21 in this embodiment determines the character size based on one threshold for character size determination. They are classified into two types, large size and small size.

  In the following description, the character size is described as being classified into two sizes, large and small. However, the number of character sizes is not limited to two.

  If YES in step S201, that is, if the character size is large, the image area separation & character size determination processing unit 21 outputs information indicating that the character size is large to each subsequent image processing module. The data difference is transmitted together with the data, and the color difference calculation processing unit 51 determines whether or not the color difference between the character color and the character background color is larger than a predetermined threshold (threshold color difference) (step S202).

  If YES in step S202, that is, if the color difference between the character color and the background color is large (the character color and the background color are not similar colors), as shown in FIG. It is checked whether it is white (white character) (step S203).

  If YES in step S203, that is, for example, as shown in FIG. 16, for example, a white character (white character on the black ground), the color difference calculation processing unit 51 has a large character size, character color, and background color. Is transmitted to the subsequent image processing module, and the filter processing unit 25 weakens the edge enhancement filter to perform edge enhancement processing, and performs color conversion and clear. The toner application processing unit 27 automatically turns off the clear toner application image data generation process and does not apply the clear toner to the white character portion (α = 0) (step S204). That is, as shown in FIG. 16, when the character size is large, the color difference between the character color and the background color is large, and the character color is a white character, the white character has no toner, and the background has a certain density. Since a dark toner (black toner in FIG. 16) is loaded, the relative gloss difference is increased when the clear toner is not loaded, and the appeal can be improved.

  If NO in step S203, that is, if the character color is not white, the color difference calculation processing unit 51 has a large character size, a large color difference between the character color and the background color, and the character color is not a white character. To the subsequent image processing module, the filter processing unit 25 weakens the edge emphasis filter to perform edge emphasis processing, and the color conversion & clear toner application processing unit 27 reduces the consumption amount of the clear toner. It is determined whether or not to apply clear toner to the character portion according to the selection on the operation display unit 13 by the user as to whether to save or prioritize image quality (step S205). The relationship between the setting information (clear toner save mode or image quality priority (high image quality) mode) by the user, the color difference between the character color and the character background color, and the amount of clear toner applied is shown in FIG. There is such a relationship. In FIG. 17, in the clear toner (transparent toner) save mode, if the color difference is medium, a small amount of clear toner is placed on the character portion, and if the color difference is large, the clear toner is not placed on the character portion. It is set. In addition, when the user setting is the image quality priority (high image quality) mode and the color difference is medium, a medium amount of clear toner is placed on the character portion, and when the color difference is large, a small amount of clear toner is applied. Put it on the text. That is, the larger the color difference, the smaller the amount of clear toner, and the clear toner save mode reduces the clear toner than the high image quality mode. In short, when the text size is large, the color difference between the text color and the background color is large, and the text color is not white text, the discriminability has reached a certain level even without putting clear toner. The amount to be loaded is left to the user's judgment.

  When NO in step S202 of FIG. 14, that is, for example, as shown in FIG. 18, when there is a black character on the ground, the color difference between the character color and the background color is small (the character color and the background color are The color difference calculation processing unit 51 transmits information that the character size is large and the color difference between the character color and the background color is small to the subsequent image processing module, and the filter processing unit 25 The edge enhancement filter is weakened to perform edge enhancement processing, and the color conversion & clear toner application processing unit 27 applies more clear toner than normal characters (step S206). That is, if the background of the character is a similar color, the appeal is weak, and therefore the filter processing unit 25 emphasizes the edge more than necessary even in the case where the appeal is improved in a pixel with a large character size. Do not. In this case, if the edge portion is emphasized, as shown in FIG. 7, only the pixels at the boundary portion between the background portion and the character portion become dark and the inside of the character line becomes thin. Then, the color conversion & clear toner application processing unit 27 applies the clear toner to the character area, but the clear toner application amount is larger (thicker) than the normal application amount, and the character portion Improve glossiness. In this case, if the application amount of the clear toner is further increased, the characters can be seen three-dimensionally, and the appeal can be further improved. In this case, since the character size is large, even if the clear toner is slightly deviated, the character readability does not deteriorate. In this way, when the character size is large and the color difference between the character color and the background color is small, the edge emphasis filter is weakened, and the amount of clear toner applied to the character portion is increased more than usual, thereby Appealability can be further improved and legibility can be maintained.

  If NO in step S201, that is, if the character size is small, the color difference calculation processing unit 51 determines whether the color difference between the character color and the background color is large (step S207). When the color difference between the character color and the background color is large, the color difference calculation processing unit 51 transmits information that the character size is small and the color difference between the character color and the background color is large to the subsequent image processing module. No particularly large image processing change is performed, and clear toner is not applied to the character portion (step S208). That is, when the character size is small and the color difference between the character color and the background color is large, the contrast is high and the character portion is considered to have some appealing and readable characteristics. Therefore, the read image data processing unit 50 is particularly large enough to perform image processing such that the γ conversion unit 23 slightly lowers the background density or the filter processing unit 25 slightly enhances edge enhancement. The image processing is not changed, and the color conversion and clear toner application processing unit 27 does not apply clear toner. In other words, when the character size is small and the color difference between the character color and the background color is large, it is considered that both the legibility and appealability have already reached a certain level in the normal state, and if image processing is performed, The side effects are likely to be larger, so no image processing is performed.

  If NO in step S207, that is, if the color difference between the character color and the background color is small, the color difference calculation processing unit 51 indicates that the character size is small and the color difference between the character color and the background color is small. It is transmitted to the image processing module at the subsequent stage, and the filter processing unit 25 increases the emphasis filter of the character part so as to increase the appeal, and the color conversion & clear toner application processing unit 27 Color conversion is performed in a direction in which the color difference between the character color and the character background color increases, and clear toner is not applied to the character portion (α = 0) (step S209). That is, when the character size is small and the color difference is small, the appeal is low. For example, as shown in FIG. 19, when the cyan color is the background and is blue (when blue is on the cyan ground), the secondary color of blue (B) is cyan (C By performing the process of shifting the hue of the character in the direction of magenta (M) opposite to (), contrast with the background color can be given and the appeal can be improved. Further, if a black character is in a gray background of the same color, contrast can be given by lowering the background density.

  Further, when the character size is small, as described above, if clear toner is applied to the character, the clear toner protrudes from the character background, and thus the clear toner cannot be applied. Therefore, when the character size is small and the color difference between the character color and the background color is small, the appeal and readability are improved by performing edge enhancement or changing the hue. However, since the image processing is performed more strongly than usual, the image is slightly shifted from the original, but the appeal and readability that are more important can be improved.

  In each of the above embodiments, image processing with clear toner is performed for all character portions of a document. However, only specific character portions of a document are subjected to image processing with clear toner. It may be a target.

  For example, in the case of a red-black document in which red and black are mixed, the above-mentioned clear toner-applied image that improves appeal by setting the red character portion that the user thinks is most important as an image processing target with the provision of clear toner. Perform data generation processing. In addition, for example, in a document using a highlighter, the clear toner-applied image data generation process for improving appeal is performed by using characters painted with the highlighter as an image processing target with clear toner. . In addition, in a manuscript that uses a highlighter pen, the letters are painted with the highlighter pen. Clear toner may be applied to the toner.

  If the red character portion or the portion painted with the highlighter is detected from the image data of the document if it is a red character portion, in the case of the second embodiment, the character color extracting unit 63 determines whether the character is a red character. If it is a highlighter pen, in the case of the second embodiment, the character background color extraction 64 determines that it is other than a white background.

  In this way, it is possible to automatically discriminate important red character portions of red and black originals and characters painted with fluorescent pens on originals with fluorescent pens, thereby improving appeal.

  As described above, the MFP 1 according to the present embodiment detects the size of the color difference between the character region and the background region of the character region with respect to the predetermined threshold color difference, and converts the character region into two types of character region sizes, a large size and a small size. judge. The MFP 1 prohibits the clear toner-added image data generation processing in the color conversion & clear toner applying processing unit 27 for a character region having a small size and a large color difference as the contents of the image processing applied to the character region. However, a strong edge emphasis filter process is performed by the filter processing unit 25 for a small-sized character region having a small color difference, and the background region is detected by the color conversion process of the color conversion and clear toner application processing unit 27. A color conversion process that increases the contrast with the color is performed, and the color conversion and clear toner application processing unit 27 prohibits the clear toner application image data generation process. Further, the MFP 1 causes the filter processing unit 25 to perform weak edge emphasis filter processing on a large-sized character region having a small color difference, and the color conversion & clear toner application processing unit 27 performs more than usual. Clear toner application image data generation processing for applying a lot of clear toner is performed. Further, the MFP 1 causes the filter processing unit 25 to perform weak edge emphasis filter processing on a character region having a large size, a large color difference, and a white character color, and color conversion and clear toner applying processing. The clear toner imparted image data generation process in the unit 2727 is prohibited, and a weak edge emphasis filter is used in the filter processing unit 25 for a character region having a large size, a large color difference, and a character color other than white. In addition to performing the process, the image processing content is used for processing the clear toner imparted image data generation process in the color conversion & clear toner imparting processing unit 2727 according to the user's selection in the operation display unit 13.

  Therefore, since the appeal effect also depends on the color difference (contrast) between the character color and the character background color, the color difference between the character region and the background region can be used as a criterion for applying clear toner to reduce the consumption of clear toner. However, the appeal effect can be improved effectively.

  Specifically, for example, when the character size is large and the contrast with the background is small, the glossiness is greatly increased by placing more clear toner than usual, and the appeal is more appealing than when clear toner is not used. Can be further improved. In addition, when the character size is large and the contrast with the background is large, there is appeal to some extent, so by reducing the consumption of clear toner while maintaining appeal, by applying less or less clear toner than usual. Can be reduced. Furthermore, if the character size is large, the contrast with the background color is large, and the character is white, the toner is placed on the background and no toner is placed on the character portion. Since the appeal based on the contrast based on the gloss difference of the toner is already sufficient, the consumption of the clear toner can be suppressed while maintaining the appeal by not using the clear toner.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

  The present invention relates to an image processing apparatus that effectively applies clear toner such as transparent toner, an image forming apparatus such as a printer, a copying apparatus, and a composite apparatus equipped with the image processing apparatus, an image processing method, an image processing program, and a recording medium. Can be used.

1 MFP
2 Reading unit 3 Reading image data processing unit 4 Bus control unit 5 Plotter image data processing unit 6 Plotter I / F unit 7 Plotter unit 8 HDD (hard disk)
9 CPU
10 memory 11 SB
12 ROM
DESCRIPTION OF SYMBOLS 13 Operation display part 14 Line | wire I / F part 15 External I / F part 16 Expansion bus 21 Image area separation & character size judgment processing part 22 Background removal processing part 23 γ conversion part 24 Isolated point removal processing part 25 Filter processing part 26 Change Double processing unit 27 Color conversion & clear toner application processing unit 31 Hue division masking processing unit 32 Three-dimensional LUT processing unit 33 UCR / UCA processing unit 34 Clear toner application processing unit 41 Edge extraction processing unit 42 γ conversion processing unit 43 Gradation processing Unit 50 read image data processing unit 51 color difference calculation processing unit 61 line buffer 62 character area labeling unit 63 character color extraction unit 64 character background color extraction unit 65 color difference calculation unit 66 color difference classification processing unit

JP 2009-58941 A

Claims (10)

Output mode detecting means for detecting whether or not the output mode of the image data is a character document mode;
When the image data output mode is the character document mode, character pixel determination means for determining whether or not each pixel data of the image data is character pixel data;
Based on the determination result of the character pixel determination means, character area size determination means for determining the character area size for each character area;
Image processing means for subjecting the image data to a plurality of types of image processing including clear toner imparted image data generation processing for generating clear toner imparted image data for forming an image imparted with clear toner as an output image of the image data When,
Have
The character region size determination means executes a process of determining at least the character region into three types of large, medium and small character sizes,
When the character size is determined to be small, the image processing means determines the image processing content that prohibits the clear toner-added image data generation processing, and the output mode is other than the character original mode. An image processing apparatus that determines the clear toner-added image data generation processing . The image processing apparatus according to claim 1 , wherein when the character size is determined to be small, the image processing unit performs image processing to compensate for the amount of clear toner that cannot be applied . The character area size determining means includes:
The character area is determined as three types of character area sizes, large size, medium size, and small size,
The image processing means includes
As the image processing, at least a function of performing thickening processing of characters and processing of enlarging characters,
The image processing control means includes
As the contents of the image processing of the image processing means, the thick line processing is performed on the image data of the medium-sized character area in the thick line processing, and the large size character is processed in the enlargement processing. 3. The image processing apparatus according to claim 1, wherein an image processing content for performing the enlargement process and for performing the clear toner-added image data generation process is determined. The character area size determining means includes:
The character area is determined as three types of character area sizes, large size, medium size, and small size,
The image processing means includes
As the image processing, it has a function of performing at least gamma conversion processing and filter processing,
The image processing control means includes
As the contents of the image processing of the image processing means, weak image enhancement processing is performed on the image data of the large-sized character area by the filtering processing, and the clear toner-added image data generation processing is performed. The image processing apparatus according to claim 1, wherein the content of image processing to be performed is determined. The image processing apparatus includes:
Color difference detection means for detecting the magnitude of a color difference between the character area and the background area of the character area with respect to a predetermined threshold color difference;
Clear toner processing selection means for selecting execution and prohibition of the clear toner-attached image data generation processing;
With
The character area size determining means includes:
The character area is determined as two types of character area sizes, a large size and a small size,
The image processing means includes
As the image processing, it has a function of performing at least gamma conversion processing, filter processing, and color conversion processing,
The image processing control means includes
As the contents of the image processing of the image processing means, the clear toner-added image data generation processing is prohibited for the small-sized character region having the large color difference, and the small-size character difference of the color difference is prohibited. For a small character region, the filter processing performs strong edge enhancement filter processing, and the color conversion processing performs color conversion processing for increasing contrast with the color of the background region, and the clear toner. The attached image data generation processing is prohibited, and the character processing having the small size and the small color difference is subjected to weak edge enhancement filter processing by the filter processing, and more clear toner than usual is applied. The clear toner imparted image data generation process to be performed is performed, and the character area having the large size, the large color difference, and the white character color is In the filter process, weak edge emphasis filter process is performed, and the clear toner-added image data generation process is prohibited, and a character area having a large size, a large color difference, and a character color other than white is used. Is characterized in that it performs weak edge emphasis filter processing in the filter processing, and determines image processing contents for processing the clear toner-added image data generation processing according to selection by the clear toner processing selection means. The image processing apparatus according to claim 1. The image processing apparatus includes:
Specific color detecting means for detecting whether or not the character region is a specific color;
The image processing control means includes
6. The image processing apparatus according to claim 1, wherein the image processing is determined as processing content of the image processing means only for the character region having the specific color.   An image forming apparatus comprising the image processing apparatus according to claim 1. An output mode detection processing step for detecting whether the output mode of the image data is the character document mode;
A character pixel determination processing step for determining whether or not each pixel data of the image data is character pixel data if the output mode of the image data is a character document mode;
A character area size determination processing step for determining the character area size for each character area based on the determination result in the character pixel determination processing step;
An image processing step of performing a plurality of types of image processing including clear toner imparted image data generation processing for generating clear toner imparted image data for forming an image imparted with clear toner as an output image of the image data. When,
Have
In the character area size determination processing step, a process of determining at least the character area into three types of large, medium, and small character sizes is performed,
In the image processing step, when the character size is determined to be small, the image processing content for prohibiting the clear toner-added image data generation processing is determined, and the output mode is other than the character original mode. An image processing apparatus that determines the clear toner-added image data generation processing . On the computer,
An output mode detection process for detecting whether the output mode of the image data is a character document mode;
When the output mode of the image data is a character document mode, a character pixel determination process for determining whether or not each pixel data of the image data is character pixel data;
A character area size determination process for determining a character area size for each character area based on the determination result in the character pixel determination processing step;
Image processing for performing a plurality of types of image processing including clear toner-applied image data generation processing for generating clear toner-applied image data for forming an image to which clear toner is applied as an output image of the image data; ,
An image processing program for executing
In the character area size determination process, at least the character area is determined to have three types of large, medium, and small character sizes,
In the image processing, when the character size is determined to be small, a process for determining the image processing content for prohibiting the clear toner-added image data generation processing is executed, and the output mode is other than the character original mode. An image processing program for executing a process for determining the clear toner-added image data generation process .   A computer-readable recording medium on which the image processing program according to claim 9 is recorded.

Images