JP5625664B2 - Image processing apparatus, image processing method, image forming apparatus, and image processing program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image processing method, an image forming apparatus, and an image processing program.

  In general, in an image forming apparatus that forms an output image by synthesizing four color materials of a C (cyan) color material, an M (magenta) color material, a Y (yellow) color material, and a K (black) color material, When multi-color printing is performed, the linear speed (paper transport speed) is slower than when mono-color printing is performed, and a lot of time is required for image formation.

  The reason is that in the case of monochromatic printing, an image is formed only with the K color material, but in the case of multicolor printing, the image is formed with a combination of the C color material, the M color material, the Y color material, and the K color material. Therefore, the total amount of the color material used for these color materials is larger than the maximum amount of color material used during monochrome printing. As a result, when trying to perform multicolor printing at the same linear velocity as that of single color printing, a fixing defect or the like is caused.

  Therefore, in order to print a multicolor image at a higher speed, the multicolor image to be printed is printed as a single color, or a part of the chromatic color material is not used so that the total amount of the color material used is reduced. A technique (for example, UCR (Under Color Removal) processing) such as replacement with a coloring material is known (see Patent Documents 1 and 2).

  However, if the total amount of color material used is reduced by replacing a part of the chromatic color material with an achromatic K color material based on the conventional UCR processing, the C color material, the M color material, and the Y color material A sufficient effect cannot be obtained when the ratio of the color materials is uneven. As a result, the total amount of the C color material, M color material, Y color material, and K color material exceeds the maximum color material usage amount during monochromatic printing, and there is a problem in that poor fixing of the color material occurs.

  For example, the composition of the color material amount of the C color material, the M color material, and the Y color material is (C, M, Y) = (80%, 60%, 10%), and there is a bias that the Y color material is small. Consider a case (note that the percentage here is the ratio when the maximum color material usage during monochromatic printing is 100%). In this case, in the conventional UCR processing, only the common part of the C color material, the M color material, and the Y color material, that is, min (C, M, Y) = 10% is replaced with the K color material. , Y, K) = (80-10%, 60-10%, 10-10%, 10%) = (70%, 50%, 0%, 10%), and the total amount of color material used is 150%. Can only be reduced to 130%. Thus, if there is a color material with a small amount of color material used (10% of the Y color material in the above example), the amount of replacement with the K color material is also small, so the color material use amount other than the minimum color material is reduced. As a result, the total amount of the C color material, the M color material, the Y color material, and the K color material exceeds the maximum color material usage amount during monochromatic printing.

  The present invention has been made in view of the above, and an image processing apparatus capable of performing multicolor printing at the same speed as single-color printing, even when there is a bias in the ratio of the amount of color material used, An object is to provide an image processing method, an image forming apparatus, and an image processing program.

In order to solve the above-described problems and achieve the object, the present invention belongs to the edge portion and the edge vicinity portion from the image forming data that holds information for determining the color material usage amount for each of the plurality of color materials for each pixel. Edge extracting means for extracting pixels and outputting edge information indicating information relating to pixels belonging to the edge portion and the edge vicinity portion, and a total amount of color material usage of all color materials is calculated for each pixel from the image forming data. Based on the color material use amount calculation means, the edge information and the total amount, the color material for each pixel of the image forming data so that the total amount is within the maximum value of the color material use amount of a single color material limiting the amount of use, the color material using amount limiting means colorant usage outputs the restricted image forming data, wherein the color material using amount limiting means, for the pixels belonging to the edges, using Color material is single color or two color material By limiting the color material usage amount control means for limiting the total color material usage amount of all the color materials to a first predetermined amount or less, and for the pixels belonging to the edge vicinity, the color material usage of the chromatic color material is used. Limiting the color material usage amount of only the chromatic color material so as to keep the ratio of the amount constant, thereby limiting the total color material usage amount of all the color materials to a second predetermined amount or less. By limiting the color material usage amount of only the chromatic color material so as to keep the ratio of the color material usage amount of the chromatic color material constant for the usage amount control means and pixels that do not belong to the edge portion and the edge vicinity portion, A non-edge color material usage amount control means for limiting the total color material usage amount of all the color materials to a third predetermined amount or less, and the sum of the first predetermined amount and the second predetermined amount is: The maximum color material usage amount of a single color material, and the first predetermined amount and the third predetermined amount are And wherein the Shii.
Further, the present invention extracts pixels belonging to the edge portion and the edge vicinity portion from the image forming data that holds the information for determining the color material usage amount for each of the plurality of color materials for each pixel, and sets the edge portion and the edge vicinity portion. Edge extraction means for outputting edge information indicating information relating to the pixel to which the image belongs, color material usage amount calculation means for calculating a total amount of color material usage of all color materials from the image forming data for each pixel, and the edge information Based on the total amount, the color material usage amount is limited by limiting the color material usage amount for each pixel of the image forming data so that the total amount is within the maximum value of the color material usage amount of a single color material. Color material usage amount limiting means for outputting the image forming data, and the color material usage amount control means has the largest color material usage amount among the plurality of color materials for the pixels belonging to the edge portion. When the color material is yellow If the color material usage is limited so that the amount of yellow and achromatic color is approximately equal, and the color material with the largest color material usage is other than yellow, the color other than yellow The color material used only for the color material is limited.

In order to solve the above-described problems and achieve the object, the present invention belongs to the edge portion and the edge vicinity portion from the image forming data that holds information for determining the color material usage amount for each of the plurality of color materials for each pixel. An edge extraction step of extracting pixels and outputting edge information indicating information relating to pixels belonging to the edge portion and the edge vicinity portion, and a total amount of color material usage of all color materials is calculated for each pixel from the image forming data. a color material using amount calculation step, on the basis of the edge information and the total amount, so that the total amount falls within the maximum value of the amount of consumed color material single colorant, the colorant for each pixel data for the image forming limiting the amount of use, seen containing a color material using amount limiting step of the color material usage outputs the restricted image forming data, wherein the color material using amount limiting step, for a pixel belonging to the edge portion, using Color material to be used is single color or two color material By limiting the color material usage amount control step for limiting the total color material usage amount of all the color materials to the first predetermined amount or less, and for the pixels belonging to the edge vicinity, the color material usage of the chromatic color material is used. Limiting the color material usage amount of only the chromatic color material so as to keep the ratio of the amount constant, thereby limiting the total color material usage amount of all the color materials to a second predetermined amount or less. For the pixels that do not belong to the usage amount control step and the edge portion and the edge vicinity portion, by limiting the color material usage amount of only the chromatic color material so as to keep the ratio of the color material usage amount of the chromatic color material constant, A non-edge color material usage amount control step for limiting the total color material usage amount of all the color materials to a third predetermined amount or less, and the sum of the first predetermined amount and the second predetermined amount is The maximum color material usage amount of a single color material, and the first predetermined amount and the third predetermined amount are And wherein the Shii.
Further, the present invention extracts pixels belonging to the edge portion and the edge vicinity portion from the image forming data that holds the information for determining the color material usage amount for each of the plurality of color materials for each pixel, and the edge portion and the edge vicinity portion are extracted. An edge extraction step for outputting edge information indicating information relating to the pixel to which the pixel belongs; a color material usage amount calculation step for calculating a total amount of color material usage amounts of all color materials from the image forming data for each pixel; and the edge information Based on the total amount, the color material usage amount is limited by limiting the color material usage amount for each pixel of the image forming data so that the total amount is within the maximum value of the color material usage amount of a single color material. A color material usage amount limiting step for outputting the image forming data, wherein the color material usage amount control step has the largest color material usage amount among the plurality of color materials for pixels belonging to the edge portion. When the color material is yellow If the color material usage is limited so that the amount of yellow and achromatic color is approximately equal, and the color material with the largest color material usage is other than yellow, the color other than yellow The color material used only for the color material is limited.

  According to the present invention, even when there is a bias in the amount of color material used during multicolor printing, the color material does not cause poor fixing of the color material even when multicolor printing is performed at the same speed as single color printing. Since the amount of use can be reduced, there is an effect that multicolor printing can be performed at the same speed as single color printing.

FIG. 1 is a block diagram illustrating the overall configuration of the image processing apparatus according to the first embodiment. FIG. 2 is an image example (entire part) of conversion used in the description of the first embodiment. FIG. 3A is a conversion image example (cutout unit) used in the description of the first embodiment. FIG. 3-2 is an example of a conversion image (cutout unit) used in the description of the first embodiment. FIG. 3C is an example of a conversion image (cutout unit) used in the description of the first embodiment. FIG. 3-4 is an example of a conversion image (cutout unit) used in the description of the first embodiment. FIG. 3-5 is an example of a conversion image (cutout unit) used in the description of the first embodiment. FIG. 4 is an example of a Laplacian filter used in the first embodiment. FIG. 5 is a block diagram illustrating the configuration of the color material usage amount limiting unit according to the first embodiment. FIG. 6 is a diagram for explaining a color material usage limit program in the edge portion. FIG. 7 is a diagram illustrating a color material usage amount restriction program in a non-edge portion. FIG. 8 is a flowchart for explaining the image processing method according to the first embodiment. FIG. 9 is a configuration diagram of an information processing apparatus capable of executing a color material selection program that implements the functions of the first embodiment. FIG. 10 is a block diagram illustrating the configuration of the color material usage amount limiting unit according to the second embodiment. FIG. 11 is a flowchart for explaining an image processing method according to the second embodiment.

  Exemplary embodiments of an image processing apparatus and an image processing method according to the present invention will be explained below in detail with reference to the accompanying drawings.

  For ease of explanation, it is assumed that the color materials used for the multicolor printing are only examples of four color materials of C color material, M color material, Y color material, and K color material. The image forming data for each pixel for multicolor printing is expressed as CMYK raster data. Further, the total amount of color material usage for the four color materials of C color material, M color material, Y color material, and K color material is expressed as the total color material amount of CMYK. Similarly, in the following description and drawings, abbreviated expressions that mean C color material, M color material, Y color material, and K color material are used as appropriate by “CMYK”. Further, specific amounts of the C color material, the M color material, the Y color material, and the K color material are expressed by the values of the corresponding components of the raster data.

(First embodiment)
In the following description, an example in which the image processing apparatus according to the present invention is applied to a multifunction peripheral (MFP) having at least two of a copy function, a printer function, a scanner function, and a facsimile function will be described. The image processing apparatus according to the present embodiment can be applied to any image forming apparatus such as a printer, a printer, or a facsimile machine.

[Configuration of image forming apparatus]
FIG. 1 is a block diagram illustrating an entire configuration of an image processing apparatus according to the first embodiment and an image forming apparatus A using the image processing apparatus. As shown in FIG. 1, the image forming apparatus A according to the first embodiment of the present invention includes a rendering unit 1, an image processing device 2, a print mode selection unit 3, and an image forming unit 4.

  The rendering unit 1 performs processing for converting input data to the image forming apparatus A into CMYK raster data (hereinafter, this processing is referred to as rendering). That is, the rendering unit 1 converts the input data into data for each pixel that uses the color material usage amount of each color material as a component. Here, for example, the input data may be RGB data. When the image forming apparatus A of the present embodiment is a printer, the input data may be described in a page description language.

  The image processing apparatus 2 reduces the amount of color material used in the CMYK raster data for each pixel by a method described in detail later so that the total amount of CMYK color materials is equal to or less than a predetermined value. However, in the image processing apparatus 2 according to the present embodiment, when the print mode selection unit 3 designates a print mode for performing multicolor printing at the same speed as single color printing (hereinafter referred to as a monochrome same speed color printing mode). It is possible to perform a selection control of performing a process of reducing the color material use amount and not performing a process of reducing the color material use amount when the monochrome same speed color printing mode is not designated.

  The print mode selection unit 3 can be a touch panel type operation unit provided in the multifunction peripheral. Alternatively, when the present embodiment is implemented by a program on a general-purpose information processing device as will be described later, the print mode selection unit 3 can be a computer display device and an input device such as a mouse. The image processing apparatus 2 and the image forming unit 4 are controlled by the input to the print mode selection unit 3.

  The image forming unit 4 fixes the C color material, the M color material, the Y color material, and the K color material on the recording medium (paper) based on the CMYK raster data input from the image processing apparatus 2. At this time, the image forming unit 4 has a linear speed that is the same as that of monochrome printing and the monochrome uniform color printing mode is not designated when the monochrome uniform speed color printing mode is designated by the printing mode selection unit 3. The image is formed by feeding paper at a normal linear speed.

[Configuration of image processing apparatus]
Here, the configuration of the image processing apparatus 2 will be described in detail. As illustrated in FIG. 1, the image processing apparatus 2 includes an edge extraction unit 21, a color material usage amount calculation unit 22, and a color material usage amount restriction unit 23.

  The edge extraction unit 21 extracts pixels belonging to the edge portion from the CMYK raster data rendered by the rendering unit 1 and uses information about whether each pixel belongs to the edge portion (hereinafter referred to as edge information) as a color material. Output to the usage limit unit 23. The color material usage amount calculation unit 22 calculates the total color material amount of CMYK in the raster data rendered by the rendering unit 1 for each pixel, and outputs information on the total color material amount to the color material usage amount restriction unit 23.

  The color material usage amount restriction unit 23 is calculated by the edge information obtained by the edge extraction unit 21 and the color material usage amount calculation unit 22 when the monochrome mode printing mode is designated in the print mode selection unit 3. Based on the information on the total amount of color material, a process for limiting the amount of color material used for each color material is performed so that the total amount of color material for each pixel is equal to or less than the maximum value for single color printing (100% use of K color material).

[Internal processing in edge extraction unit and color material usage calculation unit]
In the following, details of processing in the edge extraction unit 21 and the color material usage amount calculation unit 22 will be described with examples. An example in which “ABC” is written in blue letters on a white background is shown in FIGS. FIG. 2 visually represents the color difference by hatching and the like, and FIG. 3 represents numerical data. Since the data input to the edge extraction unit 21 and the color material usage amount calculation unit 22 is CMYK raster data, the processing in the edge extraction unit 21 and the color material usage amount calculation unit 22 corresponds to the color material usage amount. The calculation will be described for each component of the CMYK raster data.

  First, the edge extraction unit 21 sets the value obtained by subtracting the values of the respective CMY component and K component from 255 (the value of the component corresponding to the maximum color material usage amount of each color material is 255). Let B ′ (see Equation 1). Next, the edge extraction unit 21 calculates an RGB value using Expression 2 from the value of R′G′B ′. Note that Max (R ′, 0) indicates that when R ′ is a positive number, the value is R, and when R ′ is a negative number, R = 0. . The same applies to G and B.

R ′ = 255− (C + K)
G ′ = 255− (M + K) (Formula 1)
B ′ = 255− (Y + K)

R = Max (R ′, 0)
G = Max (G ′, 0) (Equation 2)
B = Max (B ′, 0)

  An example of the converted raster data is shown in FIG. 2A. A part of the raster data is cut out and shown as numerical data in FIG. In FIG. 3A, regarding the R component and the G component, the value is 255 in the white background portion, and the value in the blue character portion is 0. On the other hand, for the B component, the white background portion is 255, and the blue character portion is also 255.

  Next, luminance data is calculated from the R component, G component, and B component values calculated in this way using Equation 3. For example, in the white background portion, since (R, G, B) = (255, 255, 255), luminance = 0.3 * 255 + 0.59 * 255 + 0.11 * 255 = 255.

  Luminance = 0.3 * R + 0.59 * G + 0.11 * B [Equation 3]

  In this way, the luminance information (illustrated in FIG. 2B and FIG. 3-2) is calculated, and the edge extraction unit 21 performs edge integration using a Laplacian filter as illustrated in FIG. To extract. The extracted edge portion is illustrated in FIGS. 2 (c) and 3-3.

  Thereafter, the edge extraction unit 21 binarizes the data after the edge extraction processing by the filter. In the example of this embodiment, the edge extraction unit 21 sets the non-zero component to 255 in the data after applying the Laplacian filter (FIG. 3-4).

  As described above, the edge extraction unit 21 performs edge extraction on the input CMYK raster data, and outputs binarized edge information data (FIG. 3-4) to the color material usage amount restriction unit 23. To do.

  The color material usage amount calculation unit 22 receives the CMYK raster data rendered by the rendering unit 1, calculates the CMYK color material total amount for each pixel, and calculates the calculated CMYK color material total amount for each pixel. Output to the limiting unit 23. For example, when the pixel is (C, M, Y, K) = (125, 100, 50, 10), sum (125, 100, 50, 10) = 285. The total amount of CMYK color materials may be simply the sum of the digital values of the CMYK components of the raster data, or a ratio when the maximum use amount of a single color material is 100% (in the above example, 285 / 255 * 100 = 112% (rounded up after the decimal point)).

  Further, the CMYK raster data rendered by the rendering unit 1 is sent to the color material usage amount limiting unit 23 in parallel with the edge information and the total color material amount information.

[Configuration of color material usage restriction part]
Next, the details of the configuration of the color material usage amount limiting unit 23 will be described with reference to FIG. FIG. 5 is a block diagram illustrating an internal configuration of the color material usage amount limiting unit 23 according to the first embodiment. As shown in the drawing, the color material usage amount limiting unit 23 in this embodiment includes an edge portion color material usage amount limiting unit 231, a non-edge portion color material usage amount limiting unit 232, and an output data combining unit 234. .

  The edge color material usage amount limiting unit 231 determines for each pixel whether the CMYK color material total amount exceeds 255 using the CMYK color material total amount information received from the color material usage amount calculation unit 22. If the value does not exceed 255, the edge color material usage limit unit 231 outputs the CMYK raster data value as it is to the output data synthesis unit 234 for the pixel. Further, the edge color material usage restriction unit 231 uses the edge information received from the edge extraction unit 21 to determine whether or not the pixel belongs to the edge part. Even when the pixel does not belong to the edge part, the edge part color material usage amount restriction part 231 outputs the input CMYK raster data value to the output data composition part 234 as it is.

  On the other hand, when the total color material amount of CMYK exceeds 255 and the pixel belongs to the edge portion, the edge portion color material usage amount restriction unit 231 performs a color material usage amount restriction process for the edge portion. Specifically, as illustrated in FIG. 6, first, the edge part color material usage amount limiting unit 231 obtains the maximum value among the C component, M component, Y component, and K component values of the target pixel, for example, When the maximum value is the C component, the C component is set to 255, and the other M, Y, and K components are set to 0. Similarly, when the M component or the K component is the maximum, the edge portion color material usage limit unit 231 sets the M component or the K component to 255 and sets the other components to 0, respectively. However, when the Y component is maximum, Y = 128, K = 127, and other values are set to 0. This is because, when the background of the image is white (paper white), if a single color of the Y color material is used, the contrast is low, and the identification of characters and the like becomes very poor. For this reason, when the usage amount of the Y color material is maximum, the contrast with the background is ensured by combining the Y color material and the K color material approximately in half. The CMYK raster data in which the color material usage amount is limited for all the pixels of the input CMYK raster data is sent to the output data synthesis unit 234.

  Next, the processing of the non-edge portion color material usage limit unit 232 will be described. The non-edge color material usage limit unit 232 determines whether or not the total color material amount of CMYK exceeds 255 for each pixel, as in the processing of the edge color material usage limit unit 231. If not exceeded, the non-edge color material usage limit unit 232 outputs the CMYK raster data value for the pixel to the output data synthesis unit 234 as it is. The non-edge portion color material usage limit unit 232 uses the edge information received from the edge extraction unit 21 to determine whether the pixel belongs to the edge portion. When the pixel belongs to the edge portion, the non-edge portion color material usage limit unit 232 outputs the value of the CMYK raster data to the output data synthesis unit 234 as it is.

  On the other hand, when the total color material amount of CMYK exceeds 255 and the pixel does not belong to the edge portion, the non-edge portion color material usage amount limiting unit 232 limits the color material usage amount as follows. FIG. 7 illustrates the program.

  First, when the K color material usage amount of the target pixel is less than 255, the non-edge color material usage amount limiting unit 232 determines the CMYK from the total color material amount (variable TOTAL in the drawing) which is the sum of the digital values of CMYK. Of these, the value of the K component is subtracted to obtain the total amount of color material usage only for CMY (in the figure and here referred to as variable CMY). Next, the non-edge color material usage limit unit 232 divides the value obtained by subtracting the value of the K component from 255 by the variable CMY, and determines this as the coefficient k. Then, if the non-edge portion color material usage limit unit 232 is, for example, a C component, the coefficient k is multiplied by the value of the C component, the decimal part is rounded down, and this is the new C component value after the limit process. And The processing for limiting the M component and the Y component is the same as the processing for the C component. As for the K component processing, the input K component value is held as it is.

  On the other hand, when the value of the K component of the CMYK raster data is 255, it means that the pixel has a low brightness, low saturation, and a color that is difficult to understand. The color material usage restriction unit 232 performs achromatic color such that the value of the K component is 255 and the values of the other CMY components are 0.

  The CMYK raster data with the color material usage amount restricted as described above is sent from the non-edge portion color material usage amount restriction unit 232 to the output data synthesis unit 234.

  The output data composition unit 234 receives the edge CMYK raster data received from the edge color material usage limit unit 231 and the non-edge CMYK raster data received from the non-edge color material usage limit unit 232. Then, CMYK raster data for image formation is synthesized. Specifically, the output data synthesis unit 234 refers to the edge part information from the edge extraction unit 21 for each pixel, and when the pixel belongs to the edge part, received from the edge part color material usage amount restriction part 231. The CMYK raster data is output to the image forming unit 4, and when the pixel belongs to the non-edge portion, the CMYK raster data received from the non-edge portion color material usage amount limiting unit 232 is output to the image forming unit 4. To synthesize. FIG. 2D shows an example of an image after synthesis using the above-described example in which “ABC” is written in blue characters on a white background.

  The CMYK raster data after the color material usage limit processing is input to the image forming unit 4, and the image forming unit 4 performs halftone processing and the like, and based on the color material usage of each component of the CMYK raster data. A color image is formed on the paper.

[Image processing method]
FIG. 8 is a flowchart for explaining the image processing method according to the first embodiment. Hereinafter, for the sake of simplicity of description, description will be made with reference to the configuration of the embodiment described with reference to FIGS. 1 and 5.

  First, the user selects a mode for performing multicolor printing at the same speed as single-color printing by using an operation unit provided in a multifunction peripheral (MFP) or the like (step S10). The result of this selection is transmitted to the print mode selection unit 3 to control the image processing apparatus 2 and the image forming unit 4.

  Next, the rendering unit 1 renders the input data and converts it into CMYK raster data (step S11). Here, rendering includes rasterizing data described in a page description language and processing for converting RGB data into CMYK raster data for image formation such as a printer. In general, color conversion from RGB to CMYK is performed using a 3D-LUT (3D) that defines a correspondence between an sRGB signal that is a standard color space of RGB data and an image forming signal of an image forming apparatus such as a printer. (LookUp Table) or the like is prepared in advance and the interpolation is performed.

  Then, the edge extraction unit 21 performs an edge extraction process on the rendered CMYK raster data (step S12). Further, the color material usage amount calculation unit 22 receives the CMYK raster data, and calculates the CMYK color material total amount for each pixel (step S13).

  Next, the color material usage calculation unit 22 determines for each pixel whether or not the total color material amount of CMYK exceeds 255 (100%) (step S14).

  When the total color material amount of CMYK does not exceed 255, the color material usage amount limiting unit 23 outputs the input CMYK raster data value as it is for the pixel (step S14: No). On the other hand, when the total color material amount of CMYK exceeds 255 (step S14: Yes), the color material usage amount limiting unit 23 determines whether or not the target pixel belongs to the edge portion (step S15). This determination is made by the color material usage amount limiting unit 23 based on the edge information for each pixel extracted by the edge extraction unit 21.

  If it is determined that the pixel belongs to the edge portion (step S15: Yes), the edge color material usage amount limiting unit 231 performs the color material usage amount limiting process for the edge portion (step S16), and the pixel is If it does not belong to the edge portion (step S15: No), the edge portion color material usage amount restriction unit 231 performs the color material usage amount restriction processing for the non-edge portion (step S17).

  After that, the edge information is referred to for each pixel, and the output data composition unit outputs the CMYK raster data subjected to the edge processing when the target pixel belongs to the edge part, and outputs the data when it belongs to the non-edge part. Then, the CMYK raster data subjected to the non-edge processing is combined as an output, and this is used as the CMYK raster data for image formation (step S20).

  Finally, based on the CMYK raster data after the color material usage fee restriction process, the image forming unit 4 performs halftone processing and the like, and forms an image on paper at the same linear speed as that of monochromatic printing.

  As described above, in the image processing apparatus, the image forming apparatus, and the image processing method according to the first embodiment, the edge portion is obtained from the image forming data that holds the information for determining the color material usage amount for each of the plurality of color materials for each pixel. And an edge extraction unit 21 that extracts pixels belonging to the non-edge part and outputs edge information indicating information relating to the pixels belonging to the edge part and the non-edge part, and a total amount of color material usage of all color materials from the image forming data Is calculated for each pixel, and based on the color material usage amount calculation unit 22 that outputs the total amount of color material usage, and the edge information and the total amount of color material usage, the total amount is the color material usage amount of a single color material. A color material usage amount limiting unit 23 that limits the color material usage amount for each pixel of the image forming data so as to be within the maximum value and outputs the image forming data in which the color material usage amount is limited; Depending on the ratio of colorant usage Even if some such, it is possible to perform a sufficient material amount limiting process for multicolor printing in a single color printing the same speed. Furthermore, since different color material usage amount limiting processing is performed in the edge area and the non-edge area, the effect of speeding up multicolor printing can be achieved without degrading the legibility of characters and the like as much as possible.

  In the image processing apparatus, the image forming apparatus, and the image processing method according to the first embodiment, the color material usage amount limiting unit 23 uses a single color or two color materials for the pixels belonging to the edge portion. Limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for the pixels that do not belong to the edge portion and the edge color material usage amount control unit 231 to be limited By providing the edge portion color material usage amount control unit 232, different color material usage amount limiting processes in the edge region and the non-edge portion region are parallelized and can be efficiently processed.

  In the image processing apparatus, the image forming apparatus, and the image processing method according to the first embodiment, the color material use amount control unit 23 uses the most color material use amount among a plurality of color materials for pixels belonging to the edge portion. When the color material with a large amount of color is yellow, the color material usage is limited so that the amount of yellow and achromatic color is approximately equal, and the color material with the largest color material usage among the multiple color materials is yellow. In the case of other than the above, by limiting the color material used only for the color material other than yellow, even when the background of the image is white (paper white), the contrast with the background is ensured, It is possible to prevent a decrease in distinguishability such as characters.

  Note that the image processing method according to the present invention may be realized by programming the image processing method according to the first embodiment and causing the information processing system to execute the program.

  FIG. 9 is a diagram illustrating a hardware configuration example of an information processing system capable of executing a program that implements the image processing method according to the first embodiment.

  As shown in FIG. 9, a computer 100 includes a program reading device 100a, a CPU 100b that controls the whole, a RAM 100c that is used as a work area for the CPU 100b, a ROM 100d that stores a control program for the CPU 100b, and the like. A hard disk 100e, a NIC 100f, a mouse 100g, a keyboard 100h, a display 111 that displays image data and allows a user to input information by directly touching the screen, and a color printer 112 are provided. Note that the system according to the present embodiment can be realized by, for example, a workstation or a personal computer. The processing function performed by the CPU 100b can be provided in the form of, for example, a software package, specifically, an information recording medium such as a CD-ROM or a magnetic disk. For this reason, in the example shown in FIG. 9, when an information recording medium is set, a medium driving device (not shown) that drives the information recording medium is provided.

  In the case of the above configuration, the function of the print mode selection unit 3 shown in FIG. 1 can be performed by the mouse 100g, the keyboard 100h, or the display 111. Further, the function of each unit such as the rendering unit 1, the image processing apparatus 2, and the edge extraction unit 21 constituting the rendering unit 1 illustrated in FIG. 1 can be provided to the CPU 100 b. Therefore, the image processing method of this embodiment described with reference to FIG. 8 can be implemented not only in the configuration shown in FIG. 1 but also in the above configuration.

  In this case, the program for executing the color material usage reduction process of the present invention, that is, the program used in the hardware system can be provided in a state recorded in the recording medium. The information recording medium on which the program or the like is recorded is not limited to a CD-ROM, and for example, a ROM, RAM, flash memory, magneto-optical disk, or the like may be used. The program recorded on the recording medium is installed in a storage device incorporated in the hardware system, for example, the hard disk 100e, so that this program can be executed to realize a color material usage reduction function. Further, the program for realizing the color material usage reduction function or the like of the present invention is not only provided in the form of a recording medium, but may be provided from a server by communication via a network, for example. good.

(Second Embodiment)
In general, in an image forming apparatus that forms an image on a paper medium using a plurality of color materials, alignment is not successful when the color materials are superimposed, and so-called misregistration may occur. Therefore, in the second embodiment, in addition to the edge portion and the non-edge portion, the edge vicinity portion is set so that the color material usage amount of each pixel is within 100% even when plate misregistration occurs. And appropriate color material usage limit processing is performed for each. Therefore, the present embodiment is common in many respects to the first embodiment, and the description of the common portions will be simplified with reference to the same drawings and the same reference numerals.

[Configuration of image processing apparatus]
In the image processing apparatus of the second embodiment, the processing in the edge extraction unit 21 and the internal configuration / processing of the color material usage amount limiting unit 23 are different from those in the first embodiment. Therefore, the internal configurations of the edge extraction unit 21 and the color material usage limit unit 23 will be described focusing on the differences.

  The edge extraction unit 21 of this embodiment extracts an edge part from the CMYK raster data received from the rendering unit 1 in the same manner as the edge extraction unit 21 of the first embodiment described with reference to FIG. That is, the edge extraction unit 21 calculates luminance information from CMYK raster data, extracts an edge portion using a Laplacian filter or the like illustrated in FIG. 4, and binarizes the edge portion (see FIG. 3-4). reference). Further, the edge extraction unit 21 of the present embodiment performs a process of setting a flag indicating that the pixel is in the vicinity of the edge in the extracted data after binarization. In the example shown in FIG. 3-5, “2” indicating the vicinity of the edge is set as a flag for the two pixels above, below, left, and right of the pixel indicating the edge portion (having a value of 255).

  The color material usage amount limiting unit 23 according to the present embodiment includes edge information from the edge extraction unit 21, information on the total color material amount from the color material usage amount calculation unit 22, and CMYK raster data from the rendering unit 1. Input and output CMYK raster data with limited color material usage. That is, the color material usage amount limiting unit 23 of the present embodiment has the same input format and output format as the color material usage amount limiting unit 23 of the first embodiment. However, the color material usage amount limiting unit 23 in the second embodiment is different from the first embodiment in the internal configuration and processing.

  FIG. 10 is a block diagram illustrating an internal configuration of the color material usage amount limiting unit 23 according to the second embodiment. As shown in FIG. 10, the color material usage limit unit 23 in this embodiment includes an edge color material usage limit unit 231, a non-edge color material usage limit unit 232, and an edge vicinity color material usage limit. A unit 233 and an output data synthesis unit 234.

  The processing in the edge portion color material usage amount limiting unit 231 is similar to that in the first embodiment, but the edge portion color material usage amount limitation unit 231 in this embodiment uses a single color maximum color material. It is not limited to 100% of the amount used, but limited to a certain predetermined amount. Here, for ease of explanation, an example is specifically considered in which, for example, the amount is limited to 80% of the maximum amount of single color material used. That is, the edge portion color material usage limit unit 231 performs processing in which the value 255 in FIG. 6 is replaced with 204 (80% of 255). When the color material usage amount of the Y color material is the maximum among the C color material, the M color material, the Y color material, and the K color material, the edge color material usage amount limiting unit 231 determines that Y = 102, K = 102.

  Next, processing of the edge vicinity color material usage amount limiting unit 233 will be described. The edge vicinity color material usage amount limiting unit 233 determines whether the target pixel belongs to the edge vicinity based on the edge information of the target pixel. Then, the color material usage amount limiting unit 233 near the edge has a total color material amount at the edge portion (in the above example, the maximum value 204 (80%)) and the total color material amount near the edge is 255 (100 %) To limit the amount of color material used. That is, the edge portion color material usage amount limiting unit 231 limits the total color material amount at the edge portion to a first predetermined amount or less, and the edge vicinity color material usage amount limitation unit 233 is the total color material amount at the edge portion. Is limited to the second predetermined amount or less, the sum of the first predetermined amount and the second predetermined amount needs to be 255 (100%). That is, in the above specific example, the edge vicinity color material usage amount limiting unit 233 is changed from 255 (100%) to 51 (20%) in the color material usage amount limitation program shown in FIG. The replacement process may be executed. The condition for replacing the K color material with a single color is “(TOTAL ≧ 51) & (K ≧ 51)”. When the target pixel does not belong to the edge vicinity portion, the edge vicinity portion color material usage amount limiting unit 233 outputs the input CMYK raster data as it is.

  The reason why the above processing is performed is to prevent the total color material amount of the pixel from exceeding 255 even when the color material in the vicinity of the edge shifts and is superimposed on the edge portion.

  For the same reason, in the case of a non-edge portion (excluding the vicinity of the edge), the non-edge portion color material usage amount limiting unit 232 determines the total color material amount in the vicinity of the edge (in the above example, the maximum value 51 (20% )) And the total amount of color material in the non-edge portion are limited so that the color material usage amount is within 255 (100%). That is, the edge vicinity color material usage limit unit 233 limits the total color material amount in the edge vicinity to a second predetermined amount or less, and the non-edge color material usage limit unit 232 provides color material in the non-edge portion. When the total amount is limited to the third predetermined amount or less, the sum of the second predetermined amount and the third predetermined amount needs to be 255 (100%). In the case of the above specific example, the non-edge portion color material usage amount limiting unit 232 executes a process in which 255 (100%) is replaced with 204 (80%) in the color material usage amount limitation program shown in FIG. That's fine. In the above requirement, the first predetermined amount and the third predetermined amount are always equal.

  As described above, the CMYK raster data in which the color material usage amount is limited for each region is sent to the output data synthesis unit 234, and the raster data of the entire image is synthesized. The combined CMYK raster data is input to the image forming unit 4 as in the first embodiment.

[Image processing method]
Next, an image processing method according to the second embodiment will be described. FIG. 11 is a flowchart for explaining an image processing method according to the second embodiment. Since the image processing method according to the present embodiment has many parts overlapping with the image processing method according to the first embodiment, the description will be omitted as appropriate.

  Steps S10 to S15 of the image processing method according to this embodiment are the same as those in the first embodiment. That is, the user selects a multi-color printing mode at the same speed as the single color printing by the printing mode selection unit 3 (step S10), the rendering unit 1 converts the input data into CMYK raster data (step S11), and edge extraction is performed. Whether the total color material amount of CMYK exceeds 255 after the unit 21 performs edge extraction processing (step S12) and the color material usage amount calculation unit 22 calculates the total color material amount of CMYK (step S13). Is determined for each pixel (step S14). If the total amount of CMYK color material does not exceed 255 (step S14: No), the color material usage amount limiting unit 23 outputs the input CMYK raster data as it is for the pixel, and the CMYK color material. When the total amount exceeds 255 (step S14: Yes), it is determined whether or not the target pixel belongs to the edge portion (step S15).

  If it is determined that the pixel belongs to the edge portion (step S15: Yes), the edge portion color material usage amount restriction unit 231 performs the color material usage amount restriction process for the edge portion (step S16). When the pixel does not belong to the edge portion (step S15: No), the color material usage amount limiting unit 23 further determines whether the pixel belongs to the vicinity of the edge (step S18). Here, the color material usage amount limiting process in the present embodiment is different from that of the first embodiment in that the color material usage amount limiting process is limited to, for example, 80% of the maximum color material usage amount of a single color material as described above (see FIG. 6). reference).

  When it is determined in step S18 that the pixel belongs to the vicinity of the edge (step S18: Yes), the edge vicinity color material usage amount limiting unit 233 performs the color material usage amount limitation processing for the edge vicinity (step S19). When it is determined that the color does not belong to the vicinity of the edge (step S18: No), the non-edge portion color material usage amount limiting unit 232 performs the color material usage amount limiting process for the non-edge portion (step S17). As described above, the color material usage amount limiting process performed by the edge vicinity color material usage amount limiting unit 233 is a process of limiting the total color material amount to 20%, and is performed by the non-edge portion color material usage amount limiting unit 232. The color material usage amount limiting process is a process of limiting the total color material amount to 80% (see FIG. 7).

  After that, the edge information is referred to for each pixel, and when the target pixel belongs to the edge portion, the value of the CMYK component of the raster data subjected to the edge processing is used as an output value. In the case of the non-edge portion, the composition value is set to the output value of the CMYK value of the data subjected to the non-edge processing. It performs (step S20).

  Finally, the image forming unit 4 performs halftone processing and the like based on the CMYK raster data after the color material usage fee restriction processing, and forms an image on paper at the same linear velocity as that of the single color printing.

  As described above, in the image processing apparatus, the image forming apparatus, and the image processing method according to the second embodiment, the edge portion is obtained from the image forming data that holds the information for determining the color material usage amount for each of the plurality of color materials for each pixel. And an edge extraction unit 21 that extracts pixels belonging to the edge vicinity portion and outputs edge information indicating information relating to the edge portion and pixels belonging to the edge vicinity portion, and a total amount of the color material usage amount of all the color materials from the image forming data Is calculated for each pixel, and based on the color material usage amount calculation unit 22 that outputs the total amount of color material usage, and the edge information and the total amount of color material usage, the total amount is the color material usage amount of a single color material. A color material usage amount limiting unit 23 that limits the color material usage amount for each pixel of the image forming data so as to be within the maximum value and outputs the image forming data in which the color material usage amount is limited; To the ratio of color material usage Even when Rigaaru such, it is possible to perform a sufficient material amount limiting process for multicolor printing in a single color printing the same speed. Furthermore, since different color material usage amount limiting processing is performed in the edge area and the non-edge area, the effect of speeding up multicolor printing can be achieved without degrading the legibility of characters and the like as much as possible.

  In the image processing apparatus, the image forming apparatus, and the image processing method according to the second embodiment, the color material usage amount limiting unit 23 uses a single color or two color materials for the pixels belonging to the edge portion. By limiting, the color material usage amount control unit 231 that limits the total color material usage amount of all color materials to a first predetermined amount or less, and the color material of the chromatic color material for the pixels belonging to the edge vicinity portion By limiting the color material usage amount of only the chromatic color material so as to keep the usage rate constant, the color material near the edge that limits the total color material usage amount of all the color materials to a second predetermined amount or less. By limiting the color material usage amount of only the chromatic color material so as to keep the ratio of the color material usage amount of the chromatic color material constant for the usage amount control unit 233 and pixels that do not belong to the edge portion and the edge vicinity portion The total amount of color materials used for all color materials is less than the third predetermined amount. A non-edge portion color material usage control 232 that restricts to a first color, and the sum of the first predetermined amount and the second predetermined amount is a maximum value of the color material usage of a single color material. Since the predetermined amount is equal to the third predetermined amount, there is an effect that the fixing failure of the coloring material does not occur even when a so-called plate shift occurs.

  In the image processing apparatus, the image forming apparatus, and the image processing method according to the second embodiment, the color material use amount control unit 23 uses the most color material use amount among a plurality of color materials for pixels belonging to the edge portion. When the color material with a large amount of color is yellow, the color material usage is limited so that the amount of yellow and achromatic color is approximately equal, and the color material with the largest color material usage among the multiple color materials is yellow. In the case of other than the above, by limiting the color material used only for the color material other than yellow, even when the background of the image is white (paper white), the contrast with the background is ensured, It is possible to prevent a decrease in distinguishability such as characters.

  Also in the present embodiment, the image processing method according to the present invention may be realized by programming the image processing method and causing the information processing system to execute the program. In that case, similarly to the first embodiment, the program for realizing the image processing method according to the present embodiment can be executed using the hardware configuration of the information processing system described with reference to FIG.

DESCRIPTION OF SYMBOLS 1 Rendering part 2 Image processing apparatus 3 Print mode selection part 4 Image formation part 21 Edge extraction part 22 Color material usage-amount calculation part 23 Color material usage-amount restriction part 231 Edge part Color material usage-amount restriction part 232 Non-edge part color material usage Amount limiting unit 233 Edge color portion usage limiting unit 234 Output data combining unit 100 Computer 100a Program reading device 100b CPU
100c RAM
100d ROM
100e hard disk 100f NIC
100 g Mouse 100 h Keyboard 111 Display 112 Color printer A Image forming apparatus

JP 2008-52017 A JP 2008-99089 A

Claims (7)

Pixels belonging to the edge portion and the edge vicinity portion are extracted from the image forming data holding information for determining the color material usage amount for each of the plurality of color materials, and information relating to the pixels belonging to the edge portion and the edge vicinity portion is shown. Edge extraction means for outputting edge information;
Color material usage amount calculating means for calculating a total amount of color material usage amounts of all color materials from the image forming data for each pixel;
Based on the edge information and the total amount, the color material usage amount for each pixel of the image forming data is limited so that the total amount is within the maximum value of the color material usage amount of a single color material, Color material usage amount limiting means for outputting image forming data whose usage amount is limited;
Equipped with a,
The color material usage limit means is:
Edge portion color material usage amount control for limiting the total amount of color material usage of all color materials to a first predetermined amount or less by limiting the color material to be used to a single color or two color materials for pixels belonging to the edge portion. Means,
By limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for the pixels belonging to the vicinity of the edge, the total amount of the color material usage amount of all the color materials Edge vicinity color material usage control means for limiting the amount to a second predetermined amount or less;
By limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for pixels that do not belong to the edge portion and the edge vicinity portion, the color material of all color materials A non-edge portion color material usage control means for limiting the total amount of usage to a third predetermined amount or less;
The sum of the first predetermined amount and the second predetermined amount is a maximum color material usage amount of a single color material, and the first predetermined amount and the third predetermined amount are equal. An image processing apparatus. Pixels belonging to the edge portion and the edge vicinity portion are extracted from the image forming data holding information for determining the color material usage amount for each of the plurality of color materials, and information relating to the pixels belonging to the edge portion and the edge vicinity portion is shown. Edge extraction means for outputting edge information;
Color material usage amount calculating means for calculating a total amount of color material usage amounts of all color materials from the image forming data for each pixel;
Based on the edge information and the total amount, the color material usage amount for each pixel of the image forming data is limited so that the total amount is within the maximum value of the color material usage amount of a single color material, Color material usage amount limiting means for outputting image forming data whose usage amount is limited;
With
The color material usage amount control means, for the pixels belonging to the edge portion, when the color material with the largest color material usage amount is yellow among the plurality of color materials, the yellow and achromatic colors are approximately equal. If the color material with the largest color material usage amount is other than yellow among the plurality of color materials, the color material used only for the color material other than yellow is restricted. An image processing apparatus. An image forming apparatus comprising the image processing apparatus according to claim 1 or 2. Pixels belonging to the edge portion and the edge vicinity portion are extracted from the image forming data holding information for determining the color material usage amount for each of the plurality of color materials, and information relating to the pixels belonging to the edge portion and the edge vicinity portion is shown. An edge extraction process for outputting edge information;
A color material use amount calculating step for calculating a total amount of color material use amounts of all color materials from the image forming data for each pixel;
Based on the edge information and the total amount , the color material usage amount for each pixel of the image forming data is limited so that the total amount is within the maximum value of the color material usage amount of a single color material, A color material usage limit process for outputting image forming data with limited usage, and
Only including,
The color material usage limit step includes
Edge portion color material usage amount control for limiting the total amount of color material usage of all color materials to a first predetermined amount or less by limiting the color material to be used to a single color or two color materials for pixels belonging to the edge portion. Process,
By limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for the pixels belonging to the vicinity of the edge, the total amount of the color material usage amount of all the color materials An edge vicinity color material usage control step for limiting the amount to a second predetermined amount or less;
By limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for pixels that do not belong to the edge portion and the edge vicinity portion, the color material of all color materials A non-edge portion coloring material usage control step for limiting the total usage to a third predetermined amount or less,
The sum of the first predetermined amount and the second predetermined amount is a maximum color material usage amount of a single color material, and the first predetermined amount and the third predetermined amount are equal. Image processing method. Pixels belonging to the edge portion and the edge vicinity portion are extracted from the image forming data holding information for determining the color material usage amount for each of the plurality of color materials, and information relating to the pixels belonging to the edge portion and the edge vicinity portion is shown. An edge extraction process for outputting edge information;
A color material use amount calculating step for calculating a total amount of color material use amounts of all color materials from the image forming data for each pixel;
Based on the edge information and the total amount, the color material usage amount for each pixel of the image forming data is limited so that the total amount is within the maximum value of the color material usage amount of a single color material, A color material usage limit process for outputting image forming data with limited usage, and
Including
In the color material usage amount control step, when the color material having the largest color material usage amount is yellow among the plurality of color materials for the pixels belonging to the edge portion, yellow and achromatic colors are approximately equal in amount. If the color material with the largest color material usage amount is other than yellow among the plurality of color materials, the color material used only for the color material other than yellow is restricted. An image processing method. Pixels belonging to the edge portion and the edge vicinity portion are extracted from the image forming data holding information for determining the color material usage amount for each of the plurality of color materials, and information relating to the pixels belonging to the edge portion and the edge vicinity portion is shown. An edge extraction process for outputting edge information;
A color material use amount calculating step for calculating a total amount of color material use amounts of all color materials from the image forming data for each pixel;
Based on the edge information and the total amount , the color material usage amount for each pixel of the image forming data is limited so that the total amount is within the maximum value of the color material usage amount of a single color material, A color material usage limit process for outputting image forming data with limited usage, and
To the computer,
The color material usage limit step includes
Edge portion color material usage amount control for limiting the total amount of color material usage of all color materials to a first predetermined amount or less by limiting the color material to be used to a single color or two color materials for pixels belonging to the edge portion. Process,
By limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for the pixels belonging to the vicinity of the edge, the total amount of the color material usage amount of all the color materials An edge vicinity color material usage control step for limiting the amount to a second predetermined amount or less;
By limiting the color material usage amount of only the chromatic color material so that the ratio of the color material usage amount of the chromatic color material is kept constant for pixels that do not belong to the edge portion and the edge vicinity portion, the color material of all color materials A non-edge portion coloring material usage control step for limiting the total usage to a third predetermined amount or less,
The sum of the first predetermined amount and the second predetermined amount is a maximum color material usage amount of a single color material, and the first predetermined amount and the third predetermined amount are equal. An image processing program. Pixels belonging to the edge portion and the edge vicinity portion are extracted from the image forming data holding information for determining the color material usage amount for each of the plurality of color materials, and information relating to the pixels belonging to the edge portion and the edge vicinity portion is shown. An edge extraction process for outputting edge information;
A color material use amount calculating step for calculating a total amount of color material use amounts of all color materials from the image forming data for each pixel;
Based on the edge information and the total amount, the color material usage amount for each pixel of the image forming data is limited so that the total amount is within the maximum value of the color material usage amount of a single color material, A color material usage limit process for outputting image forming data with limited usage, and
To the computer,
In the color material usage amount control step, when the color material having the largest color material usage amount is yellow among the plurality of color materials for the pixels belonging to the edge portion, yellow and achromatic colors are approximately equal in amount. If the color material with the largest color material usage amount is other than yellow among the plurality of color materials, the color material used only for the color material other than yellow is restricted. An image processing program.

Images