JP2009088714A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of outputting a two-color image hardly creating an uncomfortable feeling without requiring complicated work in outputting a read color document image as a two-color image. <P>SOLUTION: The image forming device 100 includes: a color conversion processing part 41 color-converting image data of a color document read by an image reading part 300 to two-color image data; and an image forming part 500 outputting the two-color image based on the image data color-converted by the color conversion processing part 41, wherein the color conversion processing part 41 includes: a hue conversion part 44 generating hue data representing the hue of a chromatic pixel based on RGB values of the respective pixels constituting the image data; a hue histogram creation part 45 obtaining a histogram of the number of pixels corresponding to the respective hue data; and a pixel data conversion part 46 converting the respective pixel values by considering an achromatic color pixel and a hue value representing a peak value of a hue histogram as a first color and a second color, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a color conversion processing unit for color-converting image data of a color original read by an image reading unit into two-color image data, and a two-color image based on the image data color-converted by the color conversion processing unit. The present invention relates to an image forming apparatus that includes an image forming unit that outputs the image.

  Conventionally, an image forming apparatus configured to read a color original and output it as a two-color image is configured to output a two-color image with two output colors selected by an operator.

Patent Document 1 discloses, as such an image forming apparatus, at least a full-color printing mode, a mono-color printing mode, and a two-color printing mode, and mode switching means for switching and selecting three printing modes, and 2 A color selection unit that selects two specific colors from a plurality of colors in the color printing mode; and a conversion unit that converts image data to be formed into two types of color image data selected by the color selection unit. A color image forming apparatus with a two-color mode has been proposed.
JP 2000-3084 A

  However, in such an image forming apparatus, an operator has to select an output color in order to output a two-color image, and the work is complicated. Further, depending on the output color selected by the operator, the atmosphere generated by the color tone of the color document as a whole cannot be expressed, and the output two-color image may be uncomfortable.

  In view of the above problems, the object of the present invention is to output a two-color image that does not require a complicated operation and generates a sense of incongruity when the read color original image is output as a two-color image. It is in providing a possible image forming apparatus.

  In order to achieve the above object, according to a first characteristic configuration of an image forming apparatus according to the present invention, image data of a color document read by an image reading unit is obtained as described in claim 1 of the claims. An image forming apparatus comprising: a color conversion processing unit that performs color conversion to two-color image data; and an image forming unit that outputs a two-color image based on the image data color-converted by the color conversion processing unit, A hue conversion unit that generates hue data representing the hue of a chromatic color pixel based on the RGB value of each pixel constituting the image data, and a histogram of the number of pixels corresponding to each hue data are obtained in the color conversion processing unit. A hue histogram generation unit and a pixel data conversion unit that converts each pixel value using the achromatic color pixel as the first color and the hue value indicating the peak value of the hue histogram as the second color are provided.

  According to the above-described configuration, the hue histogram generated by the hue histogram generation unit indicates the number of pixels for each hue value of the chromatic color pixels constituting the image data of the color document generated by the hue conversion unit, The second color, which is the hue value indicating the peak value of the hue histogram, is the largest hue among the hues of the chromatic color pixels constituting the image data of the color document.

  Then, the pixel data conversion unit automatically converts the pixel values of the achromatic color pixels constituting the image data of the color original into pixel values indicating the first color, and the chromatic color pixels constituting the image data of the color original Are automatically converted into pixel values indicating the second color. Therefore, the operator is free from the complicated work of selecting the output color.

  The second color is most often included in a chromatic color region made up of chromatic pixels of a color original image, and is the color that most characterizes the atmosphere generated by the overall color of the color original. Therefore, in the two-color image output based on the image data obtained by converting the color image image data into the first color and the second color by the pixel data conversion unit, the color image is generated due to the overall hue of the color document. The atmosphere is secured and there is little risk of discomfort.

  In the second feature configuration, as described in claim 2, in addition to the first feature configuration described above, the pixel data conversion unit converts the hue value set to the second color to any one of CYM. A conversion table for conversion to color mixture data is provided.

  An image forming apparatus that outputs a color image includes at least C (cyan), Y (yellow), and M (magenta) color materials, and outputs an arbitrary color by subtractive color mixing of these color materials. However, when all the color materials are mixed, the saturation tends to decrease, so that the overall saturation is lowered.

  According to the above-described configuration, the image data set to the second color is converted into mixed color data of any two colors of CMY by the pixel data conversion unit based on the conversion table. In the output two-color image, the saturation is prevented from being lowered, and a vivid two-color image is generated.

  The third feature configuration is the low-resolution image data read by the image reading unit, in addition to the first or second feature configuration described above, as described in claim 3. The pixel data conversion unit is configured to convert each pixel value with respect to high-resolution image data read by the image reading unit. .

  According to the above-described configuration, the hue histogram is generated by the hue histogram generation unit based on the low-resolution image data read by the image reading unit in a short time, that is, based on a small number of pixels. The time required is short and the processing load is low.

  As described above, according to the present invention, when a read color original image is output as a two-color image, a two-color image that does not require a complicated operation and is less likely to cause discomfort can be output. A forming apparatus can be provided.

  An embodiment of a digital copying machine as an example of an image forming apparatus to which the present invention is applied will be described below.

  As shown in FIG. 2, a tandem type digital copying machine 100 adopting an electrophotographic system includes an operation unit 200 that is a man-machine interface with an operator, and an image reading unit that photoelectrically converts a document image from a document and reads it as image data. Unit 300, image processing unit 400 that performs image processing on image data of a document image read by image reading unit 300 and converts the image data into output image data, and output image data converted by image processing unit 400. The image forming unit 500 is provided with functional blocks such as an image forming unit 500 that forms a toner image, fixes the sheet onto which the toner image is transferred, and then outputs the fixed image. These functional blocks are centrally controlled by the system control unit 700.

  The operation unit 200 includes a touch panel type liquid crystal display unit that displays an operation screen on which operation keys such as software keys are arranged and displays operation states of the digital copying machine 100, and operation keys that are hardware keys. And is controlled by the operation control unit.

  The image reading unit 300 includes an automatic document feeder that sequentially feeds documents placed on the document feeder 301, a light source that illuminates the document, and reflection from the document that enters through a plurality of mirrors and lenses. An image sensor such as a CCD is provided which photoelectrically converts light and reads a document image as RGB value image data. The image reading operation of the image reading unit 300 is controlled by the image reading control unit.

  The image processing unit 400 is a control board on which a microcomputer including a ROM storing an operation program and a RAM serving as a work area and peripheral circuits such as an image processing ASIC and an interface circuit are mounted.

  The microcomputer of the image processing unit 400 executes an operation program stored in the ROM, and when printing is started, an RGB value image read by the image reading unit 300 based on an algorithm defined by the operation program. The data is subjected to predetermined image processing and converted to output image data having a CYMK value.

  The image forming unit 500 exposes the surface of the photosensitive member by exposing the surface of the photosensitive member by scanning a laser beam based on the output image data, and a charging device that uniformly charges the surface of the photosensitive member. M (magenta), C (cyan), Y (yellow), and K (black) toners are provided with a photosensitive unit 55 that includes a developing device that visualizes the formed electrostatic latent image as a toner image. Prepare for each color.

  The image forming unit 500 transfers and superimposes the toner image formed by each photoconductor unit 55 on the transfer belt 51 that is rotationally driven by the support roller 50, and the transfer roller 52 onto the sheet conveyed from the sheet storage unit 600. The toner image is transferred, and the toner image is melted and fixed on a sheet by a fixing unit 53 including a fixing roller and a pressure roller, and then output. The toner remaining on the transfer belt 51 is cleaned by the blade 54. The image forming operation of the image forming unit 500 is controlled by the image forming control unit.

  An image reading control unit, an image output control unit, an operation control unit, and an image processing unit 400 are connected to the system control unit 700 via a communication bus.

  Each control unit is composed of a microcomputer containing a ROM storing an operation program and a RAM serving as a work area, and a control board on which peripheral circuits such as an interface circuit are mounted.

  The system control unit 700 outputs a control signal via the communication bus and controls the other control units in an integrated manner. Other control units cause each control target to execute a predetermined operation based on the control signal.

  When a document is set on the document feeder 301 and a copy command is input by the operator via the operation unit 300, the copy command is detected by the operation control unit and output to the system control unit 700. Based on a copy command from the operator, the system control unit 700 outputs a control signal to each control unit, the image reading unit 300 reads image data from the original, and the image processing unit 400 performs image processing on the image data and outputs it. The image data is converted into image data, and the image forming unit 500 outputs an image based on the output image data.

  As shown in FIG. 1, the image processing unit 400 includes a scanner correction unit 40 that performs image correction such as shading correction according to the scanner characteristics of the image reading unit 300 on the image data read by the image reading unit 300, and RGB values. A color conversion processing unit 41 that converts the image data into CYMK image data, and a printer correction unit 42 that corrects the image data according to the printer characteristics of the image forming unit 500 and generates output image data.

  The RGB value image data read by the image reading unit 300 is corrected to image data from which the influence of the scanner characteristics has been removed by the scanner correction unit 40. The RGB value image data corrected by the scanner correction unit 40 is converted by the color conversion processing unit 41 into CYMK value image data. The CYMK value image data converted by the color conversion processing unit 41 is corrected as output image data according to the printer characteristics by the printer correction unit 42 and output to the image forming unit 500.

  Here, when the copy command from the operator is a command requesting that the color original image data be output as a two-color image, the color conversion processing unit 41 reads the color original image data read by the image reading unit 300. Is converted into two-color image data, and the color original image data read by the image reading unit 300 is converted into two-color (first color and second color) image data, The image is output to the image forming unit 500.

  The color conversion processing unit 41 separates each pixel constituting the image data into an achromatic color pixel and a chromatic color pixel, and the hue of the chromatic color pixel based on the RGB value of each pixel constituting the image data. A hue conversion unit 44 that generates hue data to be represented; a hue histogram generation unit 45 that obtains a histogram of the number of pixels corresponding to each hue data; and a hue value that indicates the peak value of the hue histogram for the achromatic color pixel as the first color. A pixel data conversion unit 46 that converts each pixel value as the second color is provided.

  The region separation unit 43 calculates a difference value between the maximum value and the minimum value among the R value, the G value, and the B value that are pixel values of each pixel constituting the image data, and the difference value is set in advance. A pixel corresponding to a predetermined threshold value or less is determined to be an achromatic pixel, a pixel corresponding to the predetermined threshold value being exceeded is determined to be a chromatic pixel, and each pixel constituting the image data is determined to be an achromatic pixel. Separate into chromatic pixels.

  Specifically, the region separation unit 43 secures a memory region corresponding to each pixel constituting the image data in the RAM provided in the image processing unit 400, and stores the memory region corresponding to the pixel determined to be an achromatic pixel. Sets “0” and sets “1” in the memory area corresponding to the pixel determined to be a chromatic color pixel, thereby separating each pixel constituting the image data into an achromatic color pixel and a chromatic color pixel.

  In the present embodiment, chromatic color pixels are classified into 256 hues, and unique hue data is set for each hue. As shown in FIG. 3A, for example, hue data for R (red) is “0”, hue data for Y (yellow) is “42”, hue data for G (green) is “84”, C The hue data for (cyan) is set to “127”, the hue data for B (blue) is set to “169”, and the hue data for M (magenta) is set to “212”.

The hue conversion unit 44 generates hue data of each pixel of the chromatic color pixels separated by the region separation unit 43 based on the mathematical formula [Equation 1]. The hue data generated by the hue conversion unit 44 is normalized to a range of 0 to 255 based on [Equation 1].

  The difference value of [Equation 1] is the difference value between the maximum value and the minimum value among the R value, G value, and B value of each pixel of the chromatic color pixel, and the hue data of each pixel is in the range of 0 to 255. This is a standard for normalization. The hue conversion unit 44 uses the difference value calculated for each pixel by the region separation unit 43 as the difference value.

  For example, when the RGB value of the pixel X is (128, 255, 0), that is, when the pixel X is yellow-green, the B value is the smallest, “G value−R value” is “127”, and the difference value (G value−B value) is “255”, and the hue data of the pixel X is “63”. That is, as shown in FIG. 3B, the hue data “63” generated by the hue conversion unit 44 based on [Equation 1] includes Y (yellow) hue data and G (green) hue data. It matches the intermediate value, that is, the yellowish green hue data.

  The hue histogram generation unit 45 classifies the chromatic color pixels of the image data of the color original for each hue, and obtains a hue histogram indicating the number of pixels for each hue. Specifically, the hue histogram is as shown in the upper graph of FIG. That is, the hue corresponding to the peak value P of the hue histogram indicates the most abundant hue of the color image, in other words, characterizes the overall hue of the color image.

  The pixel data conversion unit 46 converts each pixel value of the achromatic pixel constituting the image data of the color document into a pixel value indicating the first color. In the present embodiment, the first color is preset to K (black), and the pixel data conversion unit 46 converts each pixel value of the achromatic pixel into a K value.

  Specifically, the pixel data conversion unit 46 obtains the luminance of each pixel of the achromatic pixel based on a predetermined conversion formula for converting the RGB value into the YUV value or the YCbCr value, and each pixel corresponds to the luminance. Are converted from RGB values to K values.

  The pixel data conversion unit 46 obtains an average value of RGB values that are pixel values of each of the achromatic pixels constituting the image data, and based on the average value, the pixel value of each pixel is converted into a K value from the RGB value. It may be converted to. The pixel data conversion unit 46 may convert each pixel value of the achromatic color pixel into a CYM value in which each CYM component has the same value instead of the K value.

  The pixel data conversion unit 46 obtains a peak value with reference to the hue histogram generated by the hue histogram generation unit 45, and sets the color of the hue value indicating the peak value as the second color. The pixel data conversion unit 46 includes a conversion table for converting the hue value set for the second color into color mixture data of any two colors of CYM, and the mixing ratio of the two colors is set corresponding to the hue value. With reference to the conversion table, the pixel values of the chromatic color pixels constituting the image data of the color document are converted into color mixture data of any two colors of CYM corresponding to the hue value set to the second color. Convert.

  Specifically, the pixel data conversion unit 46 obtains the luminance of each pixel of the chromatic color pixel based on a predetermined conversion formula for converting the RGB value into the YUV value or the YCbCr value, and calculates the pixel value of each pixel from the RGB value. The CYM value corresponding to the hue value set for the second color corresponding to the luminance, that is, the conversion table in which the mixing ratio of the two colors is set corresponding to the hue value, Conversion to color mixing data of any two colors of CYM maintaining the mixing ratio.

  For example, when the hue histogram generated by the hue histogram generation unit 45 is the hue histogram shown in the upper side of FIG. 4, the pixel data conversion unit 46 obtains the peak value P from the hue histogram and the hue indicating the peak value P Let the hue of the value HUEp be the second color. Further, the pixel data conversion unit 46 refers to the conversion data shown on the lower side of FIG. 4, and the C value (Cp), the Y value (0) corresponding to the hue value HUEp set for the second color, The M value (Mp) is obtained.

  Thereafter, the pixel data conversion unit 46 converts each pixel value from the RGB value to the CYM value in accordance with the luminance of each pixel of the chromatic color pixel without changing the ratio between the C value (Cp) and the M value (Mp). Convert to (Cp1, 0, Mp1). Specifically, when Cp / Mp = 2, the pixel value of the pixel with low luminance is, for example, (Cp1, Yp1, Mp1) = (2, 0, 1), and the pixel value of the pixel with high luminance is For example, (Cp1, Yp1, Mp1) = (255, 0, 128). In this embodiment, each CYM value is 8 bits.

  The pixel data conversion unit 46 obtains an average value of RGB values, which are pixel values of each of the achromatic pixels constituting the image data, and calculates the pixel value of each pixel from the RGB value corresponding to the average value. CYM value corresponding to the hue value set for the second color, that is, the conversion table in which the mixing ratio of the two colors is set corresponding to the hue value, and the CYM value maintaining the mixing ratio is referred to It may be converted into any two color mixed data.

  As described above, when outputting a two-color image, the output color of the two-color image is automatically set by the pixel data conversion unit 46 without the operator having to perform complicated work.

  The operation of the digital copying machine 100 when reading color image data and outputting it as a two-color image will be described below with reference to the flowchart shown in FIG.

  When a two-color image output command input by the operator is input from the operation control unit to the system control unit 700, the system control unit 700 outputs a control signal requesting each control unit to perform a two-color image output operation. Then, the function block corresponding to each control unit is controlled by each control unit, and the output operation of the two-color image is started. The image reading unit 300 starts prescanning of a color document. The pre-scan is performed at a low resolution by the image reading unit 300 (S1).

  A difference value between the maximum pixel value and the minimum pixel value of each pixel is calculated from the image data corrected by the scanner correction unit 40, and the image data is determined to be an achromatic pixel based on the difference value. Separated into chromatic color pixels (S2, S3).

  Based on the pixel data of the chromatic color pixel from the region separation unit 43, the hue value of each pixel of the chromatic color pixel is calculated by the hue conversion unit 44 (S4). Based on the hue value of each pixel of the chromatic color pixel from the hue conversion unit 44, a hue histogram of the chromatic color pixel of the image data is generated by the hue histogram generation unit 45 (S5).

  The peak value is obtained from the hue histogram generated by the hue histogram generation unit 45 by the pixel data conversion unit 46, the hue value indicating the peak value is set as the second color, the conversion table is referred to, and the chromatic color pixel Color mixture data of any two colors of CYM corresponding to the hue value of the second color is set (S6, S7).

  As described above, the hue histogram generation unit 45 generates a hue histogram for low-resolution image data read by the image reading unit 300. As a result, the image processing unit 400 can generate a hue histogram with a relatively small processing load and a fast processing time.

  The image scanning unit 300 starts a color image main scan. The main scan is performed at a high resolution by the image reading unit 300 (S8). The high-resolution image data read by the image reading unit 300 is corrected by the scanner correction unit 40.

  The image data corrected by the scanner correction unit 40 is calculated by the region separation unit 43 as a difference value between the maximum pixel value and the minimum pixel value of each pixel, and the image data is determined to be an achromatic pixel based on the difference value. Separated into chromatic color pixels.

  The pixel data conversion unit 46 converts the pixel value of the achromatic color pixel into a K value (S9, S10), and the pixel value of the chromatic color pixel is a mixed color of any two colors of CYM corresponding to the hue value of the second color. It is converted into a CYM value consisting of data. (S9, S11)

  The printer correction unit 42 corrects image data composed of K-valued achromatic pixels and CYM-valued chromatic color pixels according to the printer characteristics of the image forming unit 500, and generates high-resolution output image data with CYMK values. . Based on the output image data generated by the printer correction unit 42, a two-color image is formed and output by the image forming unit 500 (S12).

  As described above, the pixel data conversion unit 46 converts each pixel value to the high-resolution image data read by the image reading unit 300. Therefore, since the digital copying machine 100 outputs a high-resolution two-color image that appropriately reflects the color tone of the color image as a whole, there is little possibility that the two-color image will feel uncomfortable.

  Another embodiment will be described below. In the above-described embodiment, the hue of the hue value indicating the peak value of the hue histogram generated by the hue histogram generation unit 45 is set as the second color by the pixel data conversion unit 46. However, depending on the color image, The peak value of the hue histogram generated by the hue histogram generation unit 45 is not necessarily one. That is, the hue histogram may have two or more peak values.

  As shown in FIG. 6, when the hue histogram has two peak values and the number of pixels corresponding to each peak value is substantially the same, the hue value of each peak value is set as a median and a predetermined range (L) The pixel data conversion unit 46 may be configured so as to obtain a total value of the number of pixels having the hue value (hatched portion by hatching in the drawing) and to use the peak value with the larger total value as the peak value of the hue histogram. it can.

  This is because the color image has many hues close to the hue corresponding to the peak value where the total number of pixels is large, and the hue of the peak value is suitable as a hue that characterizes the overall hue of the color image. is there.

  The hue histogram has two peak values P2 and P3. As shown in FIG. 7, the hue value of each peak value is set to the median value, and the number of pixels having a hue value in a predetermined range (L). When the total value (hatched portion by hatching in the drawing) is obtained, the total value on the peak value P3 side may be larger than the total value on the peak value P2 side.

  In such a case, the pixel data converter 46 can be configured so that the peak value P3 is the peak value of the hue histogram. This is because since the color image has many hues close to the hue corresponding to the peak value P3, it can be considered that the hue of the peak value P3 is suitable as a hue that characterizes the overall hue of the color image. is there.

  When the hue histogram has two peak values P4 and P5, and the number of pixels corresponding to the peak value P4 and the peak value P5 is substantially the same, the hue value of each peak value is set as a median value, Even if the total value of the number of pixels having a hue value in the range (L) is obtained, there may be no significant difference in the total value.

  In such a case, as shown in FIG. 8, the number of pixels corresponding to the peak value P4 or the peak value P5 is set as a threshold value, and two threshold values corresponding to the threshold value including the hue value corresponding to the peak value P4 are set. The number of pixels having a hue value between two hue values corresponding to the threshold value, in which the total value of the number of pixels having the hue value between the hue values (hatched portion by hatching in the drawing) includes the hue value corresponding to the peak value P5. The pixel data conversion unit 46 can be configured so that the peak value P5 is the peak value of the hue histogram when the total value is smaller than the total value (hatched portion by hatching in the drawing).

  This is because the color image has many hues close to the hue corresponding to the peak value P5, and therefore, it can be considered that the hue of the peak value P5 is suitable as a hue that characterizes the overall hue of the color image. is there.

  That is, the pixel data conversion unit 46 selects the peak value of the hue value that characterizes the overall hue of the color image as the peak value of the hue histogram, and sets the hue of the hue value indicating the peak value as the second color. Any configuration may be used.

  In the embodiment described above, K (Bragg) is set in advance as the first color, but the first color is not limited to K. For example, a color other than K may be set in advance, or the first color may be set in advance by an operator.

  Further, the first color may be set by the pixel data conversion unit 46 based on the hue histogram. For example, when the hue histogram has two peak values, the hue of the hue value indicating the peak value with a small number of pixels is set to the first color, and the hue of the hue value indicating the peak value with the large number of pixels is set to the second color. The color may be set.

  In this case, both the first color and the second color are hues that characterize the overall hue of the color image. Depending on the overall hue of the color image, the first color and the second color may be more than when the first color is set to K. In some cases, it is possible to output a two-color image that is less likely to cause a sense of incongruity, and both the first color and the second color are automatically set, so the operator does not have to perform complicated operations. .

  In the above-described embodiment, the hue histogram generation unit 45 is configured to generate a hue histogram for low-resolution image data read by the image reading unit 300, and the pixel data conversion unit 46 is the image reading unit 300. Although the description has been made assuming that each pixel value is converted with respect to the read high-resolution image data, the present invention is not limited to this.

  For example, when outputting a two-color image that does not require high resolution, the hue histogram generation unit 45 generates a hue histogram for the low-resolution image data read by the image reading unit 300, and the pixel data conversion unit 46. May convert each pixel value. In this case, the image reading unit 300 only needs to read the image data once, and since the processing load on the image processing unit 400 is small and the processing time is short, a two-color image can be output quickly.

  Conversely, the hue histogram generation unit 45 may generate a hue histogram for the high-resolution image data read by the image reading unit 300, and the pixel data conversion unit 46 may convert each pixel value. . In this case, although the processing load on the image processing unit 400 is increased and the processing time is increased, the second color can be set more accurately by the image processing unit 400 and less likely to cause a sense of incongruity. Can be output.

  In the above-described embodiment, the pixel data conversion unit 46 has been described as including a conversion table that converts the hue value set for the second color into color mixture data of any two colors of CYM. The table may not be provided. In this case, although there is a possibility that the saturation of the output two-color image may be reduced, the memory capacity for providing the conversion table can be reduced. In addition, the processing load for converting the pixel values originally composed of three colors of CYM into two colors is reduced, and the processing time can be shortened so that a two-color image can be output quickly.

  In the above-described embodiment, the digital copying machine 100 which is an example of an image forming apparatus to which the present invention is applied has been described. However, the present invention is applied to other image forming apparatuses such as a multifunction machine and a printer other than the digital copying machine. Needless to say, it is applicable.

  Each of the above-described embodiments is merely an example of the present invention, and the scope of the present invention is not limited by the description. The specific configuration of each part is appropriately selected within the scope of the effects of the present invention. It goes without saying that changes can be designed.

Explanatory diagram of the image processing unit of a digital multifunction device Illustration of digital copier (A) is explanatory drawing of hue data, (b) is explanatory drawing of the hue value produced | generated by the hue conversion part. Illustration of hue histogram and conversion table A flowchart for explaining the operation of the digital multi-function peripheral when outputting a two-color image Explanatory drawing of the hue histogram in another embodiment Explanatory drawing of the hue histogram in another embodiment Explanatory drawing of the hue histogram in another embodiment

Explanation of symbols

40: Scanner correction unit 41: Color conversion processing unit 42: Printer correction unit 43: Area separation unit 44: Hue conversion unit 45: Hue histogram generation unit 46: Pixel data conversion unit 300: Image reading unit 400: Image processing unit 500: Image forming unit

Claims (3)

A color conversion processing unit that converts color document image data read by the image reading unit into two-color image data, and an image that outputs a two-color image based on the image data color-converted by the color conversion processing unit An image forming apparatus including a forming unit,
A hue conversion unit that generates hue data representing the hue of a chromatic color pixel based on the RGB value of each pixel constituting the image data, and a histogram of the number of pixels corresponding to each hue data are obtained in the color conversion processing unit. An image forming apparatus comprising: a hue histogram generation unit; and a pixel data conversion unit that converts each pixel value using an achromatic color pixel as a first color and a hue value indicating a peak value of the hue histogram as a second color.   The image forming apparatus according to claim 1, wherein the pixel data conversion unit includes a conversion table for converting a hue value set for the second color into color mixture data of any two colors of CYM.   The hue histogram generation unit is configured to generate a hue histogram for low resolution image data read by the image reading unit, and the pixel data conversion unit is a high resolution image read by the image reading unit. The image forming apparatus according to claim 1, wherein each pixel value is converted with respect to data.

Images