JP2009124253A - Image processor and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for faithfully reproducing tint, in a document and reproducing an image that a user desires in two-color copy. <P>SOLUTION: When black and red are designated as colors used in the two-color copy and setting for expressing a blue image in black is performed, a control section determines whether a subtracted value B-R, where a pixel value R of red image data is subtracted from a pixel value B of blue image data of a pixel, is larger than a threshold W1, and a subtracted value B-G, where a pixel value G of green image data is subtracted from the pixel value B of the blue image data of the pixel, is larger than a threshold W2 (#2), when the image data of the pixel are color image data (YES in #1). When the subtracted value B-R is larger than the threshold W1, and the subtracted value B-G is larger than the threshold W2 (YES in #4), the image data of the pixel are converted into the black image data (#5). Otherwise (NO in #4), the image data of the pixel are converted into the red image data (#6). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a so-called two-color copy that forms an image of a color document with two colors.

  2. Description of the Related Art Conventionally, a color digital copying machine is equipped with a technique for automatically determining whether an image read by an image reading unit is a monochrome (monochrome) image or a color image by an ACS (Auto Color Selection) process. There are some (see, for example, Patent Document 1 below).

On the other hand, a so-called two-color copying technique for forming an image of a color document with two colors is widely known. In this two-color copying technique, for example, two colors are selected from R (red), G (green), B (blue), and K (black), and an image of a document is expressed on a sheet by the selected color. In particular, an image of a document is represented on a sheet by one color designated by the user (hereinafter referred to as a designated color) and K (black) among R (red), G (green), and B (blue). A two-color copy format is currently widely used.
Japanese Patent Laid-Open No. 04-282968

  In the case of the two-color copy in which an image of a document is represented on a sheet by one color designated by the user among R (red), G (green), and B (blue) and K (black), conventionally, an image of each color is used. Among them, the black image was expressed in black, and the other images were all expressed in the designated color.

  However, for example, a blue image among R (red), G (green), and B (blue) images may be desired to be expressed in black. In the case of the two-color copy as described above, there are some colors (R) (red), G (green), and B (blue) that are more favorably expressed in black. However, in the above-described conventional configuration, the R (red), G (green), and B (blue) images are all expressed by the specified color, and the color of the image formed on the paper is the original image. In some cases, the user feels uncomfortable.

  The present invention has been made to solve the above-described problems. When performing two-color copying, it is possible to reproduce the color of an original in a more natural manner or to reproduce an image desired by a user. The purpose is to provide technology that can be used.

  According to the first aspect of the present invention, image data of an image represented by a plurality of chromatic colors is acquired on a document, and the acquired image data is converted into image data of a first color component which is one color component. An image processing apparatus capable of executing a conversion process and a conversion process for converting to image data of a second color component different from the first color component, which is one chromatic color component, When the image data of the second color component and the image data of the third color component which is a chromatic color component different from the first and second color components are included, the third color component Depending on the difference between the image data and the image data of the second color component, the acquired image data is converted into image data of the first color component, or the second color component Select whether to convert to image data, and select the conversion An image processing apparatus comprising a conversion unit that executes sense.

  According to the present invention, for example, when the difference between the image data of the second color component and the image data of the third color component is relatively small, the acquired image data is used as the second color component. When the difference between the image data of the third color component and the image data of the second color component is relatively large, the acquired image data is converted into image data of the black component. In accordance with the difference between the image data of the third color component and the image data of the second color component, the acquired image data is converted into the first color component (black component in the above example). Whether the image data is to be converted to the image data of the second color component. As a result, the black image data among the image data of each color is expressed in black as in the prior art, and the other image data is all expressed in the designated color according to the color of the original image. It is possible to reproduce an image having a close hue on paper.

  According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, a subtraction value obtained by subtracting the image data of the second color component from the image data of the third color component is calculated. And a determination unit that determines whether or not the subtraction value is greater than a predetermined threshold value, and the conversion unit determines that the subtraction value is greater than the threshold value when the determination unit determines that the subtraction value is greater than the threshold value. A conversion process for converting the acquired image data into the image data of the first color component is executed. Otherwise, the conversion process of converting the acquired image data into the image data of the second color component Is to execute.

  According to this invention, the determination unit calculates a subtraction value obtained by subtracting the image data of the second color component from the image data of the third color component, and whether the subtraction value is greater than a predetermined threshold value. It is determined whether or not. Then, when the subtraction value is larger than the threshold, that is, when the third color component has a relatively large influence, the acquired image data is converted into black image data by the conversion unit. In other cases, the acquired image data is converted into image data of the second color component.

  As a result of such processing, the image of the original is compared with a configuration in which black image data is expressed in black among the image data of each color, and all other image data is expressed in the specified color, as in the past. It is possible to reproduce an image having a color closer to the color tone on the paper.

  According to a third aspect of the present invention, in the image processing apparatus according to the first or second aspect, the first color component is a black component.

  According to the present invention, black is used as one color used for two-color copying, and when it is determined that the subtraction value is greater than the threshold value, the acquired image data is converted into black image data.

  According to a fourth aspect of the present invention, in the image processing device according to the first aspect, the first color component is a black component, and the conversion unit adds the second and third to the acquired image data. When image data of a fourth color component that is a chromatic color component different from the color is included, the difference between the image data of the third color component and the image data of the second color component, and the third color component Depending on the difference between the color component image data and the fourth color component image data, the acquired image data is converted into black component image data, or the second color component image is converted. Whether to perform conversion processing to convert to data is selected, and the conversion processing of the selected one is executed.

  According to this invention, when the first color component is a black component and the acquired image data includes image data of three color components, the image data of the third color component and the second color A conversion process for converting the acquired image data into black component image data in accordance with a difference between the component image data and a difference between the third color component image data and the fourth color component image data; It is selected whether to perform conversion processing for converting to image data of the second color component. As a result, the black image data among the image data of each color is expressed in black as in the prior art, and the other image data is all expressed in the designated color according to the color of the original image. It is possible to reproduce an image having a close hue on paper.

  According to a fifth aspect of the present invention, in the image processing device according to the fourth aspect, a first subtraction value obtained by subtracting the image data of the second color component from the image data of the third color component is calculated. Determining whether the first subtraction value is greater than a predetermined first threshold and subtracting the image data of the fourth color component from the image data of the third color component; And a determination unit that determines whether or not the second subtraction value is greater than a predetermined second threshold value, and the conversion unit uses the determination unit to determine the first subtraction value. Is greater than the first threshold value and the second subtraction value is greater than the second threshold value, a conversion process for converting the acquired image data into black image data is performed, In other cases, the acquired image data is stored in the first image data. And it executes a conversion process of converting the image data of the color components.

  According to this invention, the first subtraction value obtained by subtracting the image data of the second color component from the image data of the third color component is calculated by the determination unit, and the first subtraction value is determined in advance. A second subtraction value obtained by subtracting the image data of the fourth color component from the image data of the third color component is calculated, and the second subtraction value is calculated. It is determined whether or not the subtraction value of 2 is larger than a predetermined second threshold value.

  When the first subtraction value is greater than the first threshold value and the second subtraction value is greater than the second threshold value, that is, the third color component is The acquired image data is converted into black image data if it has a relatively greater influence than the fourth color component, and otherwise the acquired image data is converted into the first color data. Converted to color component image data.

  As a result of such processing, the image of the original is compared with a configuration in which black image data is expressed in black among the image data of each color, and all other image data is expressed in the specified color, as in the past. It is possible to reproduce an image having a color closer to the color tone on the paper.

  A sixth aspect of the present invention is the image processing apparatus according to any one of the first to fifth aspects, further comprising a first input operation unit for performing an input for designating the second color component. .

  According to the present invention, the user can set the specific color when performing two-color copying using any one of black and chromatic colors. Therefore, an image desired by the user can be generated.

  A seventh aspect of the present invention is the image processing apparatus according to any one of the first to sixth aspects, further comprising a second input operation unit for performing an input for designating the third color component. .

  According to the present invention, when performing two-color copying using any one of black and chromatic colors, the user sets another chromatic color different from the specific color that is desired to be expressed in black. can do. Therefore, an image desired by the user can be generated.

  An invention according to an eighth aspect includes an image processing apparatus according to any one of the first to seventh aspects, and an image forming unit that forms an image on a sheet using image data converted by the conversion unit. Forming device.

  According to this invention, in the image forming apparatus, the action of the invention according to any one of claims 1 to 7 can be obtained.

  According to the present invention, when performing two-color copying, it is possible to reproduce the color of an original in a more natural manner or to reproduce an image desired by a user.

  A copier as an example of an image forming apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment of the present invention. As shown in FIG. 1, the copying machine 1 includes image forming units 2M, 2C, 2Y, and 2K for each color of magenta (M), cyan (C), yellow (Y), and black (K) in the copying machine main body. It is installed side by side.

  The image forming units 2M, 2C, 2Y, and 2K (collectively referred to as the image forming unit 2) form (print) a color image on a sheet. For example, the photosensitive drum 3 made of amorphous silicon and the photosensitive drum 3 are used. A charging unit 4, an exposure unit 5, a developing unit 6, and a photoconductor cleaning unit 7 are provided around the body drum 3.

  The charging unit 4 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. The exposure unit 5 irradiates the surface of the photosensitive drum 3 with a laser beam (LED light) generated based on image data transmitted from an image data storage unit 40 (see FIG. 2) described later, and the drum surface. An electrostatic latent image is formed thereon. The developing unit 6 makes the electrostatic latent image appear as a toner image by attaching the toner supplied from the toner supply unit 61 to the electrostatic latent image formed on the photosensitive drum 3. The photoconductor cleaning unit 7 cleans the toner on the surface of the photoconductor drum 3 after the primary transfer of the toner image to the intermediate belt 10 described later.

  Below the image forming units 2M to 2K, an intermediate transfer roller 9 (primary transfer roller) and an intermediate belt (intermediate transfer belt) for performing an intermediate transfer (primary transfer) of the toner image that has become apparent on the surface of the photosensitive drum 3 are provided. 10 is disposed. The intermediate belt 10 is formed of a predetermined belt body and is configured to rotate endlessly by driving rollers 11 to 13 in a state where the intermediate belt 10 is pressed against the photosensitive drum 3 by an intermediate transfer roller 9 disposed to face each photosensitive drum 3. Has been. The toner images of the respective colors formed on the photosensitive drum 3 are transferred and superimposed on the intermediate belt 10 that is rotated endlessly in order of magenta, cyan, yellow, and black at the same timing. As a result, a color image composed of four colors Y, M, C, and K is formed on the intermediate belt 10.

  A secondary transfer roller 14 is provided via the intermediate belt 10 at a position facing the drive roller 13. The secondary transfer roller 14 transfers a color image on the intermediate belt 10 to a sheet by a transfer bias from a control unit 33 described later.

  Further, the copier 1 includes a paper feeding unit 15 that feeds paper toward the image forming units 2Y to 2K. The paper feed unit 15 includes a paper feed cassette 151 that stores paper of each size, a transport path 152 that is a path through which the paper is transported, a transport roller 153 that transports the paper in the transport path 152, and the like. The sheets taken out from the cassette 151 one by one are conveyed toward the image forming units 2Y to 2K, that is, the position of the secondary transfer roller 14. The paper feeding unit 15 conveys the paper subjected to the secondary transfer process to the fixing unit 16 and discharges the paper subjected to the fixing process to the paper discharge tray 17 at the upper part of the copying machine main body.

  A fixing unit 16 is provided at an appropriate position downstream of the secondary transfer roller 14 in the conveyance path 152. The fixing unit 16 fixes the toner image transferred to the paper. The fixing unit 16 includes a heat roller 161 and a pressure roller 162. The heat on the paper is melted by the heat of the heat roller 161, and the pressure is applied by the pressure roller 162 to fix the toner on the paper.

  Further, the copying machine 1 includes a static elimination cleaning 18 and a density sensor 19. The neutralization cleaning 18 removes (collects) the toner (residual toner) on the intermediate belt 10. The neutralization cleaning 18 includes a cleaning electrode (not shown) and a cleaning brush (rotating brush), and a cleaning bias having a polarity opposite to the charged charge of the toner is applied to the cleaning brush by the cleaning electrode. The toner is removed by moving the toner to the cleaning brush.

  The density sensor 19 measures the density on the surface of the intermediate belt 10 (hereinafter referred to as “belt surface” as appropriate).

  A document reading unit 20 and a document feeding unit 24 are provided in the upper part of the copying machine main body. The document reading unit 20 includes a scanner unit 21 including a CCD (Charge Coupled Device) sensor and an exposure lamp, and a document table 22 and a document reading slit 23 made of a transparent member such as glass. The scanner unit 21 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 22, the scanner unit 21 is moved along the document surface at a position facing the document table 22 to scan the document image. The image data acquired while scanning is output to the control unit 33 (see FIG. 2). Further, when reading a document fed by the document feeding unit 24, the document is moved to a position facing the document reading slit 23, and is synchronized with the document feeding operation by the document feeding unit 24 via the document reading slit 23. The image of the original is acquired and the image data is output to the control unit 33.

  The document feeder 24 includes a document placement unit 25 for placing a document, a document discharge unit 26 for discharging a document whose image has been read, and a document placed on the document placement unit 25. A document transport mechanism 27 including a paper feed roller, a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 23 and discharging it to the document discharge section 26 is provided. The document transport mechanism 27 further includes a sheet reversing mechanism (not shown) that reverses the document and reversely transports the document to a position facing the document reading slit 23, and images on both sides of the document are passed through the document reading slit 23. Reading is possible from the scanner unit 21.

  Further, the document feeding unit 24 is provided so as to be rotatable with respect to the main body unit 2 so that the front side thereof can move upward. By moving the front side of the document feeder 24 upward to open the upper surface of the document table 22, the operator can place a read document, for example, a book in a spread state, on the upper surface of the document table 22. It has become.

  FIG. 2 is a block configuration diagram illustrating an example of a schematic configuration of the copying machine 1. As shown in FIG. 2, the copying machine 1 includes a network I / F (interface) unit 30, an image data storage unit 40, an operation panel unit 50, a recording unit 60, a cleaning unit 70, a density sensor 19, and a control unit 33. ing.

  The network I / F unit 30 controls transmission / reception of various data to / from an information processing apparatus (external device) such as a PC connected via a network such as a LAN. The image data storage unit 40 temporarily stores image data transmitted from a PC or the like via the network I / F unit 30. The operation panel unit 50 is provided on the front unit of the copier 1 and functions as an input key for inputting various instructions by the user or displays predetermined information.

  The recording unit 60 includes the image forming unit 2, the transfer unit 61, the fixing unit 16, and the paper feeding unit 9, and performs image printing on a sheet based on image data stored in the image data storage unit 40. is there. The transfer unit 61 includes the intermediate belt 10, the driving rollers 11 to 13, the secondary transfer roller 14, and the like, and transfers the toner image on the photosensitive drum 3 to the sheet via the intermediate belt 10.

  The cleaning unit 70 includes the static elimination cleaning 18 (including the photosensitive member cleaning unit 7). The density sensor 19 is the density sensor 19 shown in FIG.

  The control unit 33 reads a ROM (Read Only Memory) for storing various control programs, a RAM (Random Access Memory) having a function of temporarily storing data and a function as a work area, and the control program and the like from the ROM. The control unit controls the operation of the entire copying machine 1 by transmitting and receiving various control signals to and from the functional units.

  The control unit 33 includes a display control unit 34, a black generation unit 35, a determination unit 36, and a conversion unit 37.

  The display control unit 34 performs two-color copying (in the present embodiment, R (red), G (green), B (blue) by performing a predetermined operation on a display screen (not shown) displayed on the operation panel unit 50. ) Is displayed on the operation panel unit 50 for instructing copying in any one color of (1) and black (K) color. FIG. 3 is a diagram showing an example of this input screen.

  As shown in FIG. 3, the input screen G1 includes a “YES” button 38 for instructing execution of two-color copying and a “NO” button 39 for instructing withdrawal of execution of two-color copying. When the “YES” button 38 is displayed, the display control unit 34 displays the input screen G2 shown in FIG. When the “NO” button 39 is operated, the display control unit 34 displays an initial screen (not shown), for example.

  The input screen G2 shown in FIG. 4 is a screen for selecting which color to use other than black as a color used when performing two-color copying, and for selecting R (red) on the screen G2. "Red" button 40, "green" button 41 for selecting G (green), and "blue" button 42 for selecting B (blue) are displayed. The color designated on the input screen G2 is referred to as a first designated color.

  When any button is operated on the input screen G2, an input screen G3 as shown in FIG. 5 is displayed. Here, in the present embodiment, the first designated color selected on the input screen G2 and an image of a color other than black can be expressed in black (image formation). The input screen G3 This is a screen for setting a color expressed in black.

  That is, the input screen G3 shown in FIG. 5 is a screen displayed on the operation panel unit 50 when, for example, red is set by the “red” button 40 as the first designated color on the input screen G2. In G3, a “green” button 43, a “blue” button 44, and a “not represented in black” button 45 are displayed. In this screen G3, for example, when the “blue” button 44 is operated, the image forming apparatus 1 reproduces the blue image of the original on the paper in black (image formation). In addition, when the “Don't express in black” button 45 is operated, the image forming apparatus 1 reproduces all red, green, and blue images in the original in red on paper. The color designated on the input screen G3 (color to be expressed in black) is referred to as a second designated color.

  When any button is operated on the input screen G3, for example, a confirmation screen G4 shown in FIG. In this confirmation screen G4, in order to make the user confirm the suitability of the processed image 46 performed based on the contents selected on the respective screens G1 to G3 and the contents input on the respective screens G1 to G3. Message 47, an “OK” button 48, and a “NO” button 49 are displayed.

  When the “OK” button 48 is operated on the confirmation screen G4, the display control unit 34 outputs information indicating that to the determination unit 36 and the conversion unit 37, while the “NO” button 49 is operated. Then, any one of the input screens G1 to G3 is displayed again.

  When the black generation unit 35, the determination unit 36, and the conversion unit 37 acquire the image data of each color of R (red), G (green), and B (blue) acquired from the document reading unit 20, the processing described below is performed. Execute. Note that the black generation unit 35, the determination unit 36, and the conversion unit 37 include R (red), G (green), and B (blue) included in an area having a predetermined size among pixels included in the CCD sensor. The image data obtained from each pixel is treated as one pixel image data.

  The black generation unit 35 generates K (black) image data based on the R (red), G (green), and B (blue) image data acquired from the document reading unit 20.

When the second designated color (blue in the above example) is designated for each pixel on the input screen G3, the determination unit 36 compares the image data of the second designated color with image data of other colors. It is determined whether or not the color of the pixel has a great influence. That is, the determination unit 36 calculates values obtained by subtracting pixel values of image data of other colors (not including black) from pixel values of image data of the second designated color (hereinafter referred to as subtraction values), respectively. It is determined whether or not the subtraction value is greater than a predetermined threshold value. For example, when the second designated color is B (blue), the determination unit 36 determines the pixel value R of the R (red) image data from the pixel value B of the B (blue) image data of the pixel. The subtraction value (B−R) when subtracted and the subtraction value (B) when the pixel value R of the G (green) color image data is subtracted from the pixel value B of the B (blue) color image data of the pixel. -G), respectively,
BR> W1 (1)
BG> W2 (2) (W1 and W2 are threshold values)
It is determined for each pixel whether or not both of the expressions (1) and (2) are satisfied.

  When the determination unit 36 determines that both the expressions (1) and (2) are satisfied, the conversion unit 37 converts the image data of the pixel into K (black) color image data, while the determination If the unit 36 determines that only one or both of the equations (1) and (2) are satisfied, the image data of the pixel is converted to image data of the first designated color (here, red).

  As a result, when the image data of the second designated color (blue in the above example) has a greater influence on the color of the pixel as compared with the image data of other colors, it is expressed by the second designated color. The displayed image is not expressed in the first designated color but is expressed in black.

  The control unit 33 outputs image data of each color output from the document reading unit 20, image data of K (black) color generated by the black generation unit 35, and K (generated by the conversion processing by the conversion unit 37. Image processing such as correction processing such as gamma correction, image data compression or expansion processing, enlargement or reduction processing is performed on the image data of black) and R (red) colors. The first color component is a black component, the second color component is an R (red) color component, the third color component is a B (blue) color component, and the fourth color component is a G (green) component. Equivalent to.

  FIG. 7 is a diagram illustrating a flowchart of processing by the control unit 33 during two-color copying. The control unit 33 executes the process shown in FIG. 3 for each pixel. Here, it is assumed that the R (red) color is selected as the first specified color and the B (blue) color is selected as the second specified color.

  As shown in FIG. 7, the control unit 33 determines whether the image data of the pixel is color image data (step # 1). If the image data is color image data (step # 1). YES), a subtraction value (BR) obtained by subtracting a pixel value R of R (red) image data from a pixel value B of B (blue) image data of the pixel, and B ( Subtraction values (BG) obtained by subtracting the pixel values R of the G (green) color image data from the pixel values B of the blue (blue) color image data are respectively calculated, and the subtraction values (BR) thereof. Is greater than the threshold value W1, and it is determined whether the subtraction value (BG) is greater than the threshold value W2 (step # 2).

  When the determination unit 36 determines that the subtraction value (BR) is greater than the threshold value W1 and the subtraction value (BG) is greater than the threshold value W2 (YES in step # 2). ) On the other hand, the image data of the pixel is converted into black image data (step # 3). In other cases, that is, when at least one of the expressions (1) and (2) is not satisfied (step # 3). 2), the pixel image data is converted into R (red) color image data (step # 4).

  If the image data is not color image data in step # 1 (NO in step # 1), the series of processes is terminated without executing the processes in steps # 2 to # 4.

  As described above, the subtraction value (BR) obtained by subtracting the pixel value R of the R (red) color image data from the pixel value B of the B (blue) color image data of the pixel, A subtraction value (BG) obtained by subtracting a pixel value R of G (green) image data from a pixel value B of B (blue) image data is calculated, and the subtraction value (BR) is calculated. ) Is greater than the threshold value W1 and the subtraction value (BG) is determined to be greater than the threshold value W2, the image data of the pixel is converted to black image data. Since the process of converting the image data of the pixel into the image data of R (red) color is performed for each pixel, the image data of the second designated color is the color of the pixel compared to the image data of other colors. That is expressed in the second designated color in the manuscript. Images can be represented by the black that. Thereby, in the case of two-color copying, it is possible to reproduce the color of the original more faithfully or to reproduce an image desired by the user.

  In this case, the following modifications may be employed instead of or in addition to the embodiment.

  [1] Before performing the determination process by the determination unit 36, the image data of each color of R (red), G (green), and B (blue) is converted into C (cyan), M (magenta), and Y (yellow). ), The C (cyan), M (magenta), and Y (yellow) image data are again converted to the R (red), After the image data is converted into G (green) and B (blue) image data, the determination process by the determination unit 36 may be performed. Alternatively, the equations (1) and (1) for each complementary color image data may be performed. An equation corresponding to 2) may be set, and based on this equation, it may be determined whether to convert the image data of the pixel into, for example, black image data or red image data.

  [2] The above embodiment assumes a two-color copy of any one of R (red), G (green), and B (blue) and black (K). The present invention can be similarly applied to a two-color copy using two colors of red, G (green), and B (blue).

1 is a side view schematically showing an internal configuration of an embodiment of an image forming apparatus according to the present invention. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus. It is a figure which shows the input screen G1. It is a figure which shows the input screen G2. It is a figure which shows the input screen G3. It is a figure which shows the input screen G4. It is a figure which shows the flowchart of the process by the control part at the time of two-color copying.

Explanation of symbols

33 Control Unit 34 Display Control Unit 35 Black Generation Unit 36 Determination Unit 37 Conversion Unit

Claims (8)

Conversion processing for acquiring image data of an image represented by a plurality of chromatic colors on a document, and converting the acquired image data into image data of a first color component which is one color component, and one chromatic color component An image processing apparatus capable of executing a conversion process for converting to image data of a second color component different from the first color component,
When the acquired image data includes image data of the second color component and image data of a third color component that is a chromatic color component different from the first and second color components, the first color component In accordance with a difference between the image data of the third color component and the image data of the second color component, a conversion process for converting the acquired image data into the image data of the first color component is performed. An image processing apparatus including a conversion unit that selects whether to perform conversion processing to convert image data of two color components and executes the conversion processing of the selected one. A determination unit that calculates a subtraction value obtained by subtracting the image data of the second color component from the image data of the third color component, and determines whether the subtraction value is greater than a predetermined threshold;
When the determination unit determines that the subtraction value is greater than the threshold value, the conversion unit performs a conversion process for converting the acquired image data into image data of the first color component, 2. The image processing apparatus according to claim 1, wherein a conversion process is performed to convert the acquired image data into image data of the second color component.   The image processing apparatus according to claim 1, wherein the first color component is a black component. The first color component is a black component;
When the acquired image data further includes image data of a fourth color component, which is a chromatic color component different from the second and third colors, the image of the third color component In accordance with the difference between the data and the image data of the second color component, and the difference between the image data of the third color component and the image data of the fourth color component, the acquired image data is converted into a black component. 2. The image processing apparatus according to claim 1, wherein it is selected whether to perform conversion processing to convert the image data into image data of the second color component or to perform conversion processing to convert to the image data of the second color component, and to execute the conversion processing of the selected one. . A first subtraction value obtained by subtracting the image data of the second color component from the image data of the third color component is calculated, and whether or not the first subtraction value is larger than a predetermined first threshold value And calculating a second subtracted value obtained by subtracting the image data of the fourth color component from the image data of the third color component, and the second subtracted value is determined in advance. A determination unit for determining whether or not the threshold is greater than
When the determination unit determines that the first subtraction value is greater than the first threshold value and the second subtraction value is greater than the second threshold value, the conversion unit obtains the acquired image. 5. The conversion process for converting data into black image data is executed, and otherwise, the conversion process for converting the acquired image data into image data of the first color component is executed. Image processing apparatus.   The image processing apparatus according to claim 1, further comprising a first input operation unit for performing an input for designating the second color component.   The image processing apparatus according to claim 1, further comprising a second input operation unit for performing an input designating the third color component. An image processing apparatus according to any one of claims 1 to 7,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet using image data converted by the converting unit.

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