JP6211952B2 - Image processing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image processing apparatus that converts a color image into a monochrome image, and an image forming apparatus.

  When printing a color image read by a color scanner in monochrome, the color image is converted into a monochrome image, and the converted monochrome image is printed.

  Conventionally, as a conversion method for converting a color image into a monochrome image, there is a method of converting an RGB signal of a color image into a luminance signal using a well-known conversion formula, and binarizing the converted luminance signal into a monochrome image. is there. In this conversion method, since the RGB signal does not necessarily match the human color sensation, it may be converted into a monochrome image having a density change different from the human color sensation.

  Therefore, in order to convert a color image into a monochrome image having the same density change as the human color sense, an LHC signal (or Lab signal or Luv signal) designed to approximate the RGB signal of the color image to the human color sense. ), Adjusting L (lightness), H (hue), and C (saturation), and inversely converting to RGB signals, then converting to luminance signals using a well-known conversion formula, and converting to a monochrome image (For example, see Patent Document 1)

JP 2001-16459 A

  However, in the conversion method described above, an area (for example, a red area and a blue area) having different three attributes (hue, saturation, and brightness) of the color of the color image is converted into an area having the same density in the monochrome image. There is. For this reason, in the converted monochrome image, areas having different three attributes of the color of the color image cannot be identified.

  An object of the present invention is to provide an image processing apparatus and an image forming apparatus that convert a monochrome image so that areas with three different attributes of a color image can be identified.

  The image processing apparatus of the present invention includes a monochrome conversion unit and an output unit. The monochrome conversion unit converts the color image into a monochrome image when the color image is a chromatic image. The output unit outputs a monochrome image to the outside. The monochrome conversion unit divides the color image into areas for each combination of predetermined attributes among the three attributes of the color, adjusts at least one of the predetermined attributes, and the density of the area for each combination of color images exceeds a certain level Convert to monochrome image differently.

  In this configuration, when the color image is a chromatic image, the monochrome conversion unit divides the color image into areas for each hue after each color reduction (for each combination of predetermined attributes), for example. The monochrome conversion unit adjusts the RGB signals of the area for each combination of color images), and converts the color image to a monochrome image so that the density of the area for each combination after monochrome conversion differs by a certain level or more. The output unit outputs the monochrome image converted by the monochrome conversion unit to the outside.

  The image processing apparatus according to the present invention includes a monochrome conversion unit, a storage unit, a halftone generation unit, and an output unit. The monochrome conversion unit converts the color image into a monochrome image when the color image is a chromatic image. The storage unit stores a plurality of dither patterns. The halftone generation unit generates a halftone of the monochrome image with reference to the storage content of the storage unit. The output unit outputs a monochrome image to the outside. The monochrome conversion unit divides the color image into areas for each combination of predetermined attributes among the three attributes of the color, and the halftone generation unit performs different dithering for areas where the density difference is less than a certain value among the areas for each combination. A halftone is generated using a pattern.

  In this configuration, when the color image is a chromatic image, the monochrome conversion unit performs monochrome conversion by dividing the color image into areas for each hue (for each combination of predetermined attributes) after color reduction. The halftone generation unit generates a halftone using different dither patterns for areas where the density difference is less than a constant among the areas for each combination of monochrome images. As a result, the image processing apparatus forms halftones with different dither patterns for each of the areas for each combination in which the density difference in the monochrome image is less than a certain value, and thus for each combination in which the density difference in the monochrome image is less than a certain value. The area can be identified.

  Further, in the configuration further comprising: a display unit that displays a color image; and an operation unit that accepts selection of a plurality of areas from areas for each combination of color images displayed on the display unit, the monochrome conversion unit is an operation unit It is preferable to adjust at least one of the predetermined attributes of the plurality of areas for which selection has been received, and convert the color image into a monochrome image so that the density of the plurality of areas for which selection has been received by the operation unit differs by a certain level or more. .

  In this configuration, the display unit displays the color image divided into areas for each combination by the monochrome conversion unit. The operation unit accepts selection of a plurality of areas from areas for each combination of displayed color images. For example, the monochrome conversion unit adjusts RGB signals of a plurality of areas selected by the operation unit to convert a color image into a monochrome image. As a result, the image processing apparatus can convert the selected plurality of areas into monochrome images in which the densities of the selected areas are different from each other by a certain level.

  Further, in a configuration further including a display unit that displays a monochrome image and a storage unit that stores an index for identifying an area for each combination, the monochrome conversion unit converts the color image without adjusting predetermined attributes. It has a display output unit that converts it into a monochrome image and outputs it to the display unit. The display unit has a density difference when the density difference of the area for each combination of monochrome images input from the display output unit is less than a certain value. It is preferable to display the area by giving an index to each area of each combination that is less than a certain amount.

  In this configuration, the monochrome conversion unit divides the color image into areas for each combination, and outputs the converted monochrome image without adjusting the three color attributes to the display unit. The display unit displays a monochrome image to which an index such as a thick frame, a halftone dot, a dot pattern, or the like is added in an area where the density difference of the converted monochrome image is less than a certain level. As a result, the image processing apparatus can identify an area for each combination of monochrome images even when an area for each combination having a density difference of less than a certain level exists in the monochrome image converted without adjusting the three color attributes. .

  In addition, in a configuration further including an operation unit that receives an operation instruction, the operation unit preferably receives selection of an attribute to be adjusted by the monochrome conversion unit in a state where an index is displayed on the display unit.

  In this configuration, the operation unit receives selection of an attribute to be adjusted by the monochrome conversion unit in a state where the area for each combination to which the index is assigned is displayed on the display unit. Accordingly, the image processing apparatus can reliably identify the area for each combination even when the converted monochrome image includes an area having a density difference less than a certain value.

  In addition, it is preferable that the monochrome conversion unit selects an attribute to be adjusted by the monochrome conversion unit so that the density of the area for each combination differs by a certain level or more with the index displayed on the display unit.

  In this configuration, the monochrome conversion unit automatically selects the attribute to be adjusted so that the density of the area for each combination differs by a certain level or more while the area for each combination to which the index is assigned is displayed on the display unit. Then, the color image is converted again into a monochrome image. Accordingly, the image processing apparatus can reliably identify the area for each combination even when the converted monochrome image includes an area having a density difference less than a certain value.

  An image forming apparatus according to the present invention includes the above-described image processing apparatus and an image forming section that forms a monochrome image output from an output section of the image processing apparatus on a sheet. As a result, the image forming apparatus can print monochrome images having different densities by a certain level or more.

  According to the present invention, an area for each combination of predetermined attributes among the three attributes of color can be converted into a identifiable monochrome image.

1 is a block diagram showing a functional configuration of an image forming apparatus according to Embodiment 1 of the present invention. 4 is a flowchart of monochrome conversion processing by a control unit of the image forming apparatus. (A) is a color image displayed on the display unit of the image forming apparatus, (B) is a monochrome image, and (C) is a monochrome image in which the color attribute of the color image is adjusted. (A) displayed on the display unit is a monochrome image of a dot screen, and (B) is a monochrome image of a red component as a dot screen and a blue component as a line screen. It is a flowchart of the monochrome conversion process by the same control part which concerns on Embodiment 2 of this invention. It is the monochrome image to which the parameter | index displayed on the display part was provided. It is a flowchart of the monochrome conversion process by the same control part which concerns on Embodiment 3 of this invention. (A) displayed on the display unit is a monochrome image output by dot-type dither, and (B) is a monochrome image output by line-type dither.

  An image forming apparatus 10 according to Embodiment 1 of the present invention will be described with reference to the drawings. As shown in FIG. 1, the image forming apparatus 10 includes an image input device 100, an image processing device 200, an image output device 300, a control unit 400, an operation unit 500, and a display unit 600, and based on instructions from the control unit 400. An image is formed on a sheet.

  The operation unit 500 includes a plurality of operation keys and accepts various operation instructions.

  The display unit 600 displays a color image. Display unit 600 is configured with a touch panel, and may display a color image and accept various operation instructions based on the pressed position information.

  The image input device 100 is a color scanner that reads a color image from a document. The image input apparatus 100 outputs color image data (hereinafter referred to as RGB signals) read from the document to the image processing apparatus 200.

  The image processing apparatus 200 converts the input RGB signal into monochrome image data (hereinafter referred to as a K signal) and outputs the data to the image output apparatus 300. The image output apparatus 300 includes an image forming unit (not shown) that forms a monochrome image on a sheet using the K signal input from the image processing apparatus 200, and discharges the sheet on which the monochrome image is formed.

  The image processing apparatus 200 includes an input processing unit 201, a determination unit 202, a compression unit 203, a compression unit 203, a storage device 204, a decoding unit 205, a monochrome conversion unit 206, a scaling unit 207, an output tone correction unit 208, and an intermediate A tone generation unit 209 is provided.

  The input processing unit 201 performs gradation conversion processing such as γ correction processing on each of the RGB signals, and outputs the RGB signals to the determination unit 202.

  The determination unit 202 determines whether the color image is a chromatic image or an achromatic color image, outputs an RGB signal to the compression unit 203, and outputs a determination result to the control unit 400.

  Specifically, for each pixel in the color image, the determination unit 202 sets MAX {| RG |, | GB |, | B with the RGB signal density of each pixel as {R, G, B}. It is determined whether −R |} is larger than a predetermined value. The determination unit 202 determines that the color image is a chromatic image when there are more pixels than the predetermined value.

  The compression unit 203 encodes the RGB signal input from the determination unit 202 and outputs the encoded code to the storage device 204. Note that the encoding is performed based on, for example, a JPEG (Joint Photographic Experts Group) system.

  The storage device 204 stores the encoded code input from the compression unit 203 and manages it as filing data. The storage device 204 outputs the encoded code to the decoding unit 205 based on an instruction (print output instruction) from the control unit 400.

  The decoding unit 205 decompresses the encoded code into an RGB signal by performing a decoding process on the encoded code. The decoding unit 205 outputs the RGB signal to the monochrome conversion unit 206.

  The monochrome conversion unit 206 includes a display output unit 216 that outputs RGB signals to the display unit 600. The monochrome conversion unit 206 selectively adjusts the RGB signals based on instructions from the control unit 400, converts the RGB signals into K signals, and outputs the converted K signals to the scaling unit 207.

  The scaling unit 207 performs monochrome image enlargement processing or reduction processing based on an instruction from the control unit 400, and outputs the K signal after the enlargement processing or reduction processing to the output tone correction unit 208. Specifically, the scaling unit 207 enlarges or reduces the monochrome image in accordance with the paper size at the time of image formation processing in the image output apparatus 300.

  The output tone correction unit 208 adjusts the intermediate density tone of the input monochrome image and outputs the adjusted K signal to the halftone generation unit 209.

  The halftone generation unit 209 separates the image into pixels for the adjusted monochrome image input from the output tone correction unit 208 using the dither pattern based on an instruction from the control unit 400, and converts each image into pixels. A gradation reproduction process (halftone generation) for selectively reproducing the gradation is selectively performed. The gradation reproduction processing unit 210 outputs the processed K signal to the image output device 300.

  The control unit 400 controls each functional unit of the image processing device 200 based on the RGB signal input from the image input device 100 and the operation instruction from the operation unit 500, and performs the following monochrome conversion processing on the RGB signal. . In the monochrome conversion process, the description of the process of some functional units is omitted.

  As shown in FIG. 2, when an RGB signal is input from the image input apparatus 100 to the image processing apparatus 200 (S11), the control unit 400 determines whether the color image is a chromatic color image or an achromatic color image. The determination is made by the unit 202 (S12). If the color image is an achromatic image, the control unit 400 converts the achromatic RGB signal into a K signal by the monochrome conversion unit 206 according to the luminance (S13), and outputs the K signal to the image output apparatus 300. (S19).

  If the color image is a chromatic image, the control unit 400 divides the color image into areas for each predetermined hue by the monochrome conversion unit 206 (S14). Specifically, first, the monochrome conversion unit 206 performs color reduction (for example, color reduction from 8 bits to 3 bits) for each pixel of the color image. Next, the monochrome conversion unit 206 compares the RGB signal after the color reduction of each pixel with the RGB signal after the color reduction of the adjacent pixel, and the number of pixels that the RGB signals after the color reduction match is a predetermined number of pixels (for example, 100 pixels). ) If present, the color image is divided by using pixels with the same RGB after the color reduction as the same area. The predetermined hue is a hue after color reduction. The area for each predetermined hue corresponds to an area for each combination of predetermined attributes according to the present invention.

  The control unit 400 outputs RGB signals from the display output unit 216 of the monochrome conversion unit 206 to the display unit 600, and displays a color image on the display unit 600 (S15). The control unit 400 allows the operation unit 500 to accept selection of a plurality of areas from areas for each predetermined hue while a color image is displayed on the display unit 600 (S16). Upon receiving selection of a plurality of areas by the operation unit 500, the control unit 400 adjusts the RGB signals of the plurality of areas, converts the RGB signals into K signals (S17), and converts the converted K signals into images. The data is output to the output device 300 (S19).

  In addition, when a plurality of areas are not selected, the control unit 400 converts the RGB signal into a K signal without adjusting the RGB signal (S18), and outputs the converted K signal to the image output apparatus 300. (S19).

  As described above, when the color image is a chromatic image, the control unit 400 adjusts the hue of a plurality of areas that have been selected from the areas for each predetermined hue, and converts the color image into a monochrome image. As a result, the image processing apparatus 200 can convert the color image into a monochrome image so that the densities of the plurality of areas for which selection has been received differ by a certain level or more, and these areas can be reliably identified. “Constant” in which the concentration differs by a certain level or more is visually determined in advance by experiments.

  In addition, the monochrome conversion unit 206 may form the entire monochrome image with a dot screen as shown in FIG. 4A when converting to a monochrome image, or as shown in FIG. The red component of the monochrome image may be formed with a dot screen and the blue component of the monochrome image may be formed with a line screen. As shown in FIG. 4B, by converting the color image into a monochrome image by changing the screen shape for each color component, even if the density difference between the areas of different hues is less than a certain level, Each can be made identifiable.

  The image forming apparatus according to the second embodiment of the present invention is different from the image forming apparatus according to the first embodiment in the flow of monochrome conversion processing by the control unit 400. Only the differences will be described below.

  The image forming apparatus further includes a storage unit (not shown) that stores hue density information and a plurality of pieces of conversion setting information.

  The hue density information indicates a predetermined hue relationship in which the density difference is less than a certain value when a color image is converted into a monochrome image. Specifically, the hue density information is a set of relationships in which the density of the K signal obtained by converting the reduced color RGB signal is less than a certain density with the density of the K signal after other conversion.

  The conversion setting information is information on a plurality of conversion settings for setting the hue adjustment amount during monochrome conversion. The plurality of conversion settings have different hue adjustment amounts.

  Next, monochrome conversion processing by the control unit 400 will be described with reference to the drawings. In the monochrome conversion process, the description of the process of some functional units is omitted. Further, the processes of S11 to S14 and S19 in FIG. 5 are the same as the processes of S11 to S14 and S19 in FIG.

  As shown in FIG. 5, after the processing of S14, the control unit 400 converts the RGB signal into the K signal without adjusting the RGB signal by the monochrome conversion unit 206 (S21).

  The control unit 400 refers to the hue density information and checks whether there is a set in the color image in which the density difference of the area for each predetermined hue is less than a certain value (S22). The control unit 400 outputs the K signal converted by the process of S21 to the image output apparatus 300 when there is no set in which the density difference is less than a certain value (S19).

  In addition, when there is a set in which the density difference is less than a certain level, the control unit 400 assigns an index to the area corresponding to the group in which the density difference is less than a certain level as illustrated in FIG. 600 is displayed (S23). The index may be a thick frame, shaded pattern, dot pattern, or the like.

  The control unit 400 displays a plurality of conversion settings on the display unit 600 with reference to the storage contents of the storage unit (S24).

  The control unit 400 enables selection of one conversion setting from the plurality of conversion settings displayed on the display unit 600 via the operation unit 500 (S25). When the control unit 400 receives the selection of the conversion setting by the operation unit 500, the control unit 400 adjusts the RGB signal of the area to which the index is assigned based on the conversion setting received, and converts the RGB signal into the K signal ( S26) The converted K signal is output to the image output apparatus 300 (S19). Further, when the operation unit 500 does not accept the conversion setting, the control unit 400 outputs the K signal converted by the process of S21 to the image output device 300 (S19).

  As described above, when the color image is a chromatic image, the control unit 400 converts the color image into a monochrome image by adjusting the hue of a set of areas where the density difference is less than a certain value. Accordingly, the image processing apparatus 200 can convert a set of areas where the density difference is less than a certain value into a monochrome image so that the density difference is more than a certain value, and can reliably identify these areas.

  The image forming apparatus according to the third embodiment of the present invention is different from the image forming apparatus according to the second embodiment in the flow of monochrome conversion processing by the control unit 400. Only the differences will be described below.

  The storage unit stores the hue density information and the conversion setting information in association with each other. A group in which the density difference in the hue density information is less than a certain value is associated with a conversion setting for converting the density so that the density differs by a certain value.

  The monochrome conversion process by the control unit 400 will be described with reference to the drawings. In the monochrome conversion process, the description of the process of some functional units is omitted. Further, the processes of S11 to S14, S19, and S21 to S23 in FIG. 7 are the same as the processes of S11 to S14, S19, and S21 to S23 of FIG.

  As shown in FIG. 7, after the process of S23, the control unit 400 determines an optimum conversion setting from among a plurality of conversion settings by the monochrome conversion unit 206 (S31). Specifically, the monochrome conversion unit 206 refers to the storage content of the storage unit, and determines that the conversion setting associated with the group in which the density difference included in the color image is less than a certain value is the optimal conversion setting. .

  The control unit 400 displays the optimum conversion setting on the display unit 600 (S32). The control unit 400 enables the selection of the optimum conversion setting to be accepted by the operation unit 500 (S33). When the control unit 400 receives the selection of the conversion setting by the operation unit 500, the control unit 400 adjusts the RGB signal of the area to which the index is assigned based on the conversion setting received, and converts the RGB signal into the K signal ( (S34), the converted K signal is output to the image output device 300 (S19). Further, when the operation unit 500 does not accept the conversion setting, the control unit 400 outputs the K signal converted by the process of S21 to the image output device 300 (S19).

  As described above, when the color image is a chromatic image, the control unit 400 automatically adjusts the hue of a set of areas where the density difference is less than a certain value, and converts the color image into a monochrome image. Thereby, the image processing apparatus 200 can convert a color image into a monochrome image so that the density difference of a set of areas in which the density difference is less than a certain level is different by a certain level or more, and can reliably identify these areas. .

  In the above-described embodiment, the monochrome conversion unit 206 adjusts the hue at the time of conversion into a monochrome image and divides the area into areas for each predetermined hue. However, the hue, saturation, and lightness that are the three attributes of color are divided. A combination of predetermined attributes among the three attributes of color by adjusting any one (for example, a predetermined saturation, a combination of a predetermined hue and a predetermined saturation, a combination of a predetermined hue, a predetermined saturation and a predetermined brightness) Etc.) It may be divided into areas. The monochrome conversion unit 206 can more easily convert to a monochrome image in which the density of the area differs by a certain level or more by adjusting the hue.

  In the above-described embodiment, the hue is adjusted when converting the monochrome image. However, the monochrome conversion unit 206 performs monochrome conversion without adjusting the hue, and the halftone generation unit 209 performs halftone using different dither patterns. It may be formed. For example, monochrome conversion may be performed using a dot-type dither pattern as shown in FIG. 8A, and monochrome conversion may be performed using a line-type dither pattern as shown in FIG. 8B. In this way, by forming different halftones, even if the density difference between the areas of different hues is less than a certain level, each of the areas of different hues can be identified.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

200 ... Image processing apparatus 202 ... Determination unit 206 ... Monochrome conversion unit 500 ... Operation unit 600 ... Display unit

Claims (6)

A monochrome conversion unit for converting the color image into a monochrome image when the color image is a chromatic image;
An output unit for outputting the monochrome image to the outside;
A display unit for displaying the monochrome image;
A storage unit for storing an index for identifying an area for each combination of predetermined attributes among the three attributes of color ;
The monochrome conversion unit, the color image is divided into areas for each of the combinations, by adjusting at least one of said predetermined attribute, the said color image as different concentrations of areas for each of the combinations is constant over A display output unit that converts the image into a monochrome image and converts the color image into the monochrome image without adjusting the predetermined attribute;
When the density difference of the area for each combination of the monochrome image input from the display output unit is less than a certain value, the display unit adds the index to the area for each combination with the density difference less than a certain value. Display
The monochrome conversion unit is an image processing apparatus that receives selection of an attribute to be adjusted by the monochrome conversion unit in a state where an index is displayed on the display unit. A monochrome conversion unit for converting the color image into a monochrome image when the color image is a chromatic image;
A storage unit that stores a plurality of dither patterns and stores an index for identifying an area for each combination of predetermined attributes among the three attributes of color ;
A halftone generation unit that generates a halftone of the monochrome image with reference to the storage content of the storage unit;
An output unit for outputting the monochrome image to the outside ;
A display unit for displaying the monochrome image ,
The monochrome conversion unit, the color image is divided into areas for each of the combinations, and the color image is converted into the monochrome image without adjusting the predetermined attribute, a display output unit for outputting to the display unit Have
When the density difference of the area for each combination of the monochrome image input from the display output unit is less than a certain value, the display unit adds the index to the area for each combination with the density difference less than a certain value. Display
The monochrome conversion unit accepts selection of an attribute to be adjusted by the monochrome conversion unit in a state where an index is displayed on the display unit,
The halftone generation unit is an image processing apparatus that generates the halftone using different dither patterns for areas where the density difference is less than a certain value among the areas for each combination. A display unit for displaying the color image;
An operation unit that accepts selection of a plurality of areas from the area for each combination of color images displayed on the display unit,
The monochrome conversion unit adjusts at least one of the predetermined attributes of the plurality of areas that have been selected by the operation unit, and the density of the plurality of areas that has received the selection by the operation unit is adjusted to the color image. The image processing apparatus according to claim 1, wherein the monochrome image is converted so as to differ by a certain amount or more. It further includes an operation unit that receives operation instructions,
The image processing apparatus according to claim 3 , wherein the operation unit receives selection of the attribute. The monochrome conversion unit, an image processing apparatus according to claim 3 in which the concentration of the area of each pre-Symbol combination selects the attribute constant or different. The image processing apparatus according to any one of claims 1 to 5 ,
An image forming apparatus comprising: an image forming unit that forms the monochrome image output from the output unit of the image processing apparatus on a sheet.