JP5050790B2 - Color processing apparatus, image forming apparatus, and program - Google Patents

Description

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

  In an image forming apparatus, generally, the total amount of color materials is limited to a certain value. This limit value varies depending on the number of colors of the image forming apparatus and the recording method. For example, in the case of an image forming apparatus that forms an image with four colors of cyan, magenta, yellow, and black (that is, the total amount is 400%), the offset printing method is 300 to 350 (%), and the electrophotographic method is used. In the case of an ink jet system, it is often limited to about 200 to 300 (%) and about 150 to 250 (%). As for the electrophotographic image forming apparatus, for example, Patent Documents 1 and 2 describe conventional techniques.

FIG. 5 is a block diagram schematically showing a conventional total amount limitation of color materials. The color conversion unit 91 shown in the figure is described in a color space (for example, CMYK color space) in which the image forming apparatus uses color signals described in a uniform color space (for example, L ^* a ^* b ^* color space). The total amount limiting unit 92 converts the input color signal so as not to exceed the limit value described above. The total amount restriction unit 92 converts the color signal using, for example, a predetermined lookup table or function. The limit value setting unit 93 sets a limit value representing the limit amount of the color signal in the total amount limit unit 92.

As shown in FIG. 5, the color conversion unit 91 and the total amount limiting unit 92 are generally functionally separated. The reason for adopting such a configuration is that color conversion is designed not to depend on individual image forming apparatuses, while the total amount limitation can be designed according to individual image forming apparatuses. It is.
In such a configuration, when the black signal (K) is included in the color signal for which the total amount is limited, the black component color signal is generally passed through in the total amount limiting unit 92. That is, the total amount limiting unit 92 generally outputs a black component color signal without changing it. For example, both Patent Documents 1 and 2 have such a configuration.
JP 2000-25274 A (paragraphs 0046, 0048, etc.) JP 2004-21202 A (paragraph 0063 etc.)

However, in the configuration in which the color signal of the black component is not changed, there is a problem that the color gamut is narrowed particularly in a tertiary color that does not include the black component or a quaternary color that has a relatively small black component.
In view of the above, an object of the present invention is to suppress the reduction of the color gamut when the total amount of color signals corresponding to the color material is limited.

The color processing apparatus according to the present invention is an input color signal that represents the amount of color material used by the image forming apparatus and that inputs an input color signal including a black component color signal and other color component color signals. And when the minimum value of the color signal of the other color component input by the input unit is not 0, the color signal of the black component and the color signal of the other color component input by the input unit are output. An adjustment value for a black component color signal is determined based on a limit value that defines a total amount of color signals to be determined, and when the minimum value is 0, a determination unit that sets the adjustment value to 0, and the input unit Subtracting means for subtracting the adjustment value determined by the determining means from the input color signals of the other color components; and the adjustment value determined by the determining means for the color signal of the black component input by the input means. Adding means for adding, and said adding means Others in which the adjustment value is subtracted by the subtraction unit based on the color signal of the black component to which the adjustment value has been added, the color signal of the other color component from which the adjustment value has been subtracted by the subtraction unit, and the limit value An adjustment unit for adjusting the color signal of the color component, a color signal of the black component to which the adjustment value is added by the addition unit, and a color signal of the other color component adjusted by the adjustment unit are output as output color signals And an output means.

In the color processing apparatus according to the present invention, there are a plurality of color signals of the other color components, and the determination unit is configured such that when the minimum value of the color signals of the other color components input by the input unit is not 0, The value obtained by dividing the sum of the color signal of the black component and the color signal of the other color component input by the input means by the limit value is divided by a value obtained by doubling the minimum value, and α is set. a value a value obtained by subtracting the color signal of the black component input by the input means divided by the minimum value from the maximum amount when the alpha _max, multiplied by the smaller of alpha or alpha _max at the minimum value Is determined as the adjustment value, and the adjustment unit subtracts the adjustment value from the limit value by subtracting the black component color signal obtained by adding the adjustment value from the addition unit as β. Multiply each of multiple color signals of the other color components The configuration for performing adjustment for dividing the sum of the plurality of color signals may be employed Te.

An image forming apparatus according to the present invention is an input unit that inputs an input color signal that represents an amount of a color material used by the apparatus, and includes an input color signal including a black component color signal and other color component color signals. When the minimum value of the color signal of the other color component input by the input unit is not 0, the color signal of the black component and the color signal of the other color component input by the input unit are output. An adjustment value for a black component color signal is determined based on a limit value that defines the total amount of color signals, and when the minimum value is 0, a determination unit that sets the adjustment value to 0 and an input by the input unit Subtracting means for subtracting the adjustment value determined by the determining means from the color signals of the other color components, and adding the adjustment value determined by the determining means to the color signal of the black component input by the input means And adding means for Based on the color signal of the black component to which the adjustment value has been added and the color signal of the other color component from which the adjustment value has been subtracted by the subtraction means, and the limit value, An adjustment unit that adjusts a color signal of a color component, a black component according to a color signal of a black component to which an adjustment value is added by the addition unit, and a color signal of another color component that is adjusted by the adjustment unit; An image forming unit that forms an image with a color material corresponding to another color component is characterized.

A program according to the present invention is a computer-executable program, which is an input color signal that represents the amount of color material used by the image forming apparatus, and that includes a black component color signal and other color components. An input means for inputting an input color signal including a color signal, and a black component color signal input by the input means when the minimum value of the color signals of other color components input by the input means is not 0 And the adjustment value of the black component color signal is determined based on the color signal of the other color component and the limit value defining the total amount of the output color signal, and when the minimum value is 0, the adjustment value and determination means to 0, the color signals of the other color component input and subtracting means for subtracting the adjustment value determined by the determining means by the input means, the color of the black component input by the input means Said to the signal An adding means for adding the adjustment value determined by the determining means; a color signal of the black component to which the adjustment value is added by the adding means; and a color signal of the other color component from which the adjustment value is subtracted by the subtracting means; Based on the limit value, an adjusting unit that adjusts the color signal of the other color component from which the adjustment value has been subtracted by the subtracting unit, a black component color signal to which the adjustment value has been added by the adding unit, and the adjusting unit It is made to function as an output means for outputting the color signals of other color components adjusted by the above as output color signals.

  According to the present invention, it is possible to suppress the reduction of the color gamut when the total amount of color signals corresponding to the color material is limited. According to the present invention, reduction of the color gamut of a tertiary color that does not include a black component or a quaternary color that has a relatively small black component can be suppressed.

[Embodiment]
FIG. 1 is a block diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. As shown in the figure, the configuration of the image forming apparatus 10 is roughly divided into an image input unit 110, a color processing unit 120, an image forming unit 130, and a control unit 140.

  The image input unit 110 acquires image data representing an image to be formed, converts the image data into a color signal suitable for processing in the color processing unit 120, and supplies the converted color signal. In the present embodiment, the image input unit 110 supplies color signals described in the CMYK color space to the image forming unit 130. That is, the image input unit 110 supplies four types of color signals, cyan (C), magenta (M), yellow (Y), and black (K), to the color processing unit 120. The image input unit 110 may be connected to, for example, an image reading apparatus such as a scanner, or may be connected to a personal computer via a network.

The image input unit 110 includes a color conversion unit 111. The color conversion unit 111 converts a color signal described in another color space different from the CMYK color space (for example, a uniform color space based on the CIELAB color system) into a color signal described in the CMYK color space. The color conversion unit 111 converts a color signal using, for example, a so-called ICC (International Color Consortium) profile. The color signals output from the color conversion unit 111 are hereinafter referred to as “S1 _C ”, “S1 _M ”, “S1 _Y ”, and “S1 _K ”. Note that the suffix of each symbol corresponds to the color component of the color signal. Each color signal represents the amount of the color material as a percentage, and the color material amount is minimum when “0 (%)”, and the color material amount is maximum when “100 (%)”. Represents that.

The color processing unit 120 adjusts the color signals S1 _C , S1 _M , S1 _Y, and S1 _K supplied from the image input unit 110, which are suitable for processing in the image forming unit 130. The color processing unit 120 performs adjustment so that the total amount of color signals after output does not exceed the limit value based on a limit value that defines the total amount of color signals after output. Here, the limit value is a predetermined value, but any one of a plurality of values may be selectable.
Specifically, the color processing unit 120 includes an input unit 121, a subtraction unit 122, a limit value setting unit 123, an addition unit 124, a CMY adjustment unit 125, and an output unit 126.

The input unit 121 includes a terminal that is electrically connected to the image input unit 110, and receives input of color signals S1 _C , S1 _M , S1 _Y and S1 _K (input color signals). The subtractor 122 adjusts the color signal S1 _K based on the color signals S1 _C , S1 _M , S1 _Y and S1 _K input by the input unit 121 and the limit value set by the limit value setting unit 123. A value is determined, and a process of subtracting the adjustment value from the color signals S1 _C , S1 _M and S1 _Y is performed. The color signals output from the subtracting unit 122 are hereinafter referred to as “S2 _C ”, “S2 _M ”, “S2 _Y ”, and “S2 _K ”. Note that the color signal S2 _K of black component corresponds to the adjustment value described above. The limit value setting unit 123 sets the limit value described above. For example, the limit value setting unit 123 stores the limit value in advance, and acquires the limit value by reading the limit value. Note that the limit value in the present embodiment is, for example, “200 (%)”. The limit value set by the limit value setting unit 123 is hereinafter referred to as “Lim”.

The adder 124 adds the color signal S1 _K input from the input unit 121 and the color signal S2 _K output from the subtractor 122. The color signal output from the adding unit 124 is hereinafter referred to as “S3 _K ”. The CMY adjustment unit 125 adjusts the color signals S2 _C , S2 _M, and S2 _Y output from the subtraction unit 122. The CMY adjustment unit 125 adjusts the color signals S2 _C , S2 _M and S2 _Y based on the color signal S3 _K output from the addition unit 124 and the limit value Lim. The color signals output from the CMY adjustment unit 125 are hereinafter referred to as “S3 _C ”, “S3 _M ”, and “S3 _Y ”. That is, the CMY adjustment unit 125 performs adjustment so that the total amount of the color signals S3 _C , S3 _M , S3 _Y and S3 _K does not exceed the limit value Lim. The output unit 126 outputs the color signals S3 _C , S3 _M, and S3 _Y output from the CMY adjustment unit 125 and the color signal S3 _K output from the addition unit 124 to the image forming unit 130 as output color signals.

The image forming unit 130 forms an image corresponding to the color signals (S3 _C , S3 _M , S3 _Y and S3 _K ) supplied from the color processing unit 120 on the recording medium. In the present embodiment, the recording medium is a sheet-like material such as paper. The image forming unit 130 of this embodiment forms an image using toner by an electrophotographic method. That is, the image forming unit 130 forms an image on a recording medium through processes such as charging, exposure, development, transfer, and fixing. There are four types of toner used by the image forming unit 130, and each includes color materials representing cyan, magenta, yellow, and black colors.

  FIG. 2 is a diagram illustrating a configuration of the image forming unit 130. As shown in the figure, the image forming unit 130 includes transfer units 131Y, 131M, 131C, and 131K, an intermediate transfer belt 132, a plurality of support members 133, a secondary transfer member 134, and a plurality of transport members 135. And a fixing device 136.

  Each of the transfer units 131Y, 131M, 131C, and 131K includes a photoreceptor 1311, a charging device 1312, an exposure device 1313, a developing device 1314, and a primary transfer member 1315. The photoreceptor 1311 is a cylindrical member having a photosensitive layer on the surface, and is a support that supports an electrostatic latent image and a toner image. The charging device 1312 uniformly charges the surface of the photoreceptor 1311. The exposure device 1313 irradiates the charged photoconductor 1311 with light to form an electrostatic latent image. The developing device 1314 supplies toner corresponding to each color of cyan, magenta, yellow, or black, and forms a toner image corresponding to the electrostatic latent image on the photoreceptor 1311 by applying a predetermined potential (developing potential). Let The primary transfer member 1315 generates a potential such that the toner image moves from the photoconductor 1311 to the intermediate transfer belt 132, and transfers the toner image.

  The intermediate transfer belt 132 is rotated by a plurality of support members 133 to convey the transferred toner image. The support member 133 movably supports the intermediate transfer belt 132 and is driven to rotate by a driving unit (not shown). The secondary transfer member 134 generates a potential such that the toner image moves from the intermediate transfer belt 132 to the recording medium, and transfers the toner image. The conveying member 135 is driven by a driving unit (not shown) to convey the recording medium along the broken line in the drawing. The fixing device 136 heats and pressurizes the recording medium to fix the toner on the recording medium.

  Returning to the description of FIG. The control unit 140 includes an arithmetic device such as a CPU (Central Processing Unit) and various memories, and controls the operation of each unit of the image forming apparatus 10. The control unit 140 exchanges information necessary for a series of processes related to image formation with the image input unit 110, the color processing unit 120, and the image forming unit 130 as necessary. Thereby, for example, when the image forming apparatus 10 can operate in a plurality of operation modes, the control unit 140 controls each unit according to each operation mode.

The configuration of the image forming apparatus 10 is as described above. With the above configuration, the image forming apparatus 10 obtains the color signals S3 _C , S3 _M , S3 _Y and S3 _K from the image data, and forms an image using the toner corresponding to the color signal. The image forming apparatus 10 according to the present embodiment is characterized by processing in the color processing unit 120. Hereinafter, color processing for obtaining the color signals S3 _C , S3 _M , S3 _Y and S3 _K from the color signals S1 _C , S1 _M , S1 _Y and S1 _K executed by the color processing unit 120 will be described.

FIG. 3 is a flowchart illustrating color processing executed by the color processing unit 120. In the figure, “min (S1 _C , S1 _M , S1 _Y )” represents the minimum value of the color signal S1 _C , S1 _M or S1 _Y. As shown in the figure, the color processing unit 120 first determines whether or not the minimum value of the color signal S1 _C , S1 _M or S1 _Y is “0” (step S1). The color processing unit 120 changes the determination method of the ratio α for determining the adjustment value according to the determination result of step S1.

When the minimum value of the color signals S1 _C , S1 _M or S1 _Y is “0” (step S1: YES), that is, when any one of the color signals S1 _C , S1 _M or S1 _Y is “0”, The color processing unit 120 substitutes “0” for the ratio α (step S2). On the other hand, when the minimum value of the color signal S1 _C, S1 _M and S1 _Y is not "0" (step S1: NO), i.e., the chrominance signal S1 _C, S1 _M and S1 also _Y are both "0" is greater than, The color processing unit 120 determines the ratio α according to the following procedure.

The color processing unit 120 first calculates a value (S1 _C + S1 _M + S1 _Y + S1 _K −Lim) obtained by subtracting the sum of the color signals S1 _C , S1 _M , S1 _Y and S1 _K by the limit value Lim with respect to the ratio α. A value obtained by dividing the minimum value min (S1 _C , S1 _M , S1 _Y ) by “2” is substituted (step S3). Next, the color processing unit 120 defines a value α _max corresponding to the upper limit value of the ratio α, and a value obtained by subtracting the color signal S1 _K from “100” which is the maximum value of the color signal (100−S1 _K). ) Is divided by the minimum value min (S1 _C , S1 _M , S1 _Y ) (step S4). Then, the color processing unit 120 determines whether or not the obtained ratio α exceeds the value α _max (step S5), and if it exceeds (step S5: YES), the ratio α is limited to limit the ratio α to the upper limit value. The value α _max is substituted for (step S6). When the ratio α is equal to or less than the value α _max (step S5: NO), the color processing unit 120 uses the value obtained in step S3 as it is.

When the ratio α is determined in this way, the color processing unit 120 obtains the black component color signal S2 _K (adjustment value) as follows. That is, the color processing unit 120 substitutes a value obtained by multiplying the minimum value min (S1 _C , S1 _M , S1 _Y ) of the color signal S1 _C , S1 _M or S1 _Y by the ratio α into the color signal S2 _K (step S7). ).
Subsequently, the color processing unit 120 obtains the color signals S2 _C , S2 _M and S2 _Y of other color components using the obtained black component color signal S2 _K. Color processing unit 120 substitutes the value obtained by subtracting the color signal S2 _K from each of the color signals S1 _C, S1 _M and S1 _Y each color signal S2 _C, S2 _M and S2 _Y (step S8).

The color processing unit 120 obtains the color signal S3 _K using the black component color signals S1 _K and S2 _K. The color processing unit 120 substitutes a value obtained by adding the color signal S1 _K and the color signal S2 _K into the color signal S3 _K (step S9).

After obtaining the color signal S3 _K , the color processing unit 120 adjusts the color signals S2 _C , S2 _M and S2 _Y based on this. In this case, the adjustment performed by the color processing unit 120 is basically an adjustment for preventing the total amount of the output color signals S3 _C , S3 _M , S3 _Y and S3 _K from exceeding the limit value Lim.
In this adjustment, the color processing unit 120 first defines the ratio β. The color processing unit 120 substitutes a value (Lim−S3 _K ) obtained by subtracting the color signal S3 _K from the limit value Lim into the ratio β (step S10). Subsequently, the color processing unit 120 multiplies each of the color signals S2 _C , S2 _M and S2 _{Y by} the obtained ratio β, and sums this color signal S2 _C , S2 _M and S2 _Y (S2 _C + S2 _M + S2 _Y). ) Is substituted for the color signals S3 _C , S3 _M and S3 _Y (step S11).

The color processing performed by the color processing unit 120 is as described above. The color processing unit 120 thus obtains the color signals S3 _C , S3 _M , S3 _Y and S3 _K and outputs them to the image forming unit 130. As a result, the image forming apparatus 10 of the present embodiment can suppress the reduction of the color gamut reproduced with multi-order colors even when the limit value Lim is set to a small value (less than 300%). Become.

FIG. 4 is a diagram for explaining the effect of the embodiment, and a color gamut reproducible in the image forming apparatus 10 of the present embodiment can be reproduced with a conventional configuration (that is, a configuration without the configuration of the present embodiment). It is a schematic diagram shown in contrast with a different color gamut. In the figure, the vertical axis represents lightness (metric lightness) L ^* , and the horizontal axis represents saturation (metric saturation) C ^* . In the figure, the configuration (total amount limiting unit 92) shown in FIG. 5 is used as the conventional configuration, and the reference numerals of the color signals are the same as those in FIG. Further, in this schematic diagram, the color gamut is schematically shown by a straight line for convenience of explanation.

  The minimum lightness point in the color gamut shown in FIG. 4 indicates a case where a color signal of 100% (%) for cyan, magenta, and yellow and 0% (%) for black is input as the input color signal. Further, the color gamut indicated by the solid line in FIG. 4 is a color gamut that can be reproduced when the limit value Lim is set to 200 (%) in the image forming apparatus 10 of the present embodiment, and is a broken line or a one-dot chain line in FIG. The color gamuts shown are reproducible color gamuts when the limit value Lim is 200 (%) and 300 (%) in the conventional configuration.

  As shown in FIG. 4, in the conventional configuration (broken line), when the limit value Lim is set to be small, the color gamut of the low lightness / low saturation region is narrowed. Such reduction of the color gamut is particularly noticeable in a tertiary color region such as a tertiary color that does not include a black component or a quaternary color that has a relatively small black component. On the other hand, according to the image forming apparatus 10 of the present embodiment, since the color signal of the black component is adjusted, the lightness is low even if the limit value is the same as compared with the conventional configuration (broken line). -Reduction of the color gamut in the low saturation region can be suppressed. In other words, the image forming apparatus 10 according to the present embodiment has a configuration capable of greatly increasing the output when the black component of the input color signal is relatively small, thereby enabling low lightness and low chroma regions. This suppresses the decrease in reproducibility.

[Modification]
The present invention is not limited to the above-described embodiment, and may be implemented in other forms. For example, the following modifications can be applied to the present invention. Note that the following modifications may be combined as appropriate.

(1) Modification 1
The color processing according to the present invention is not limited to the above-described embodiment (FIG. 3). In short, the color processing according to the present invention reduces the color gamut associated therewith when the black color signal of the input color signal is relatively small and the total amount limit value (Lim) is relatively small. As long as the adjustment value is obtained so as to be suppressed and added to the color signal of the black component, the specific processing may be different from the above-described embodiment.

(2) Modification 2
The present invention is suitable for performing so-called colorimetric color reproduction. However, the present invention can also be applied to the case where so-called preferred color reproduction (Preferred Color Reproduction) or accurate color reproduction (Exact Color Reproduction) is performed.

(3) Modification 3
The present invention can also be provided in forms other than the image forming apparatus. In the present invention, for example, the above-described color processing unit 120 may be configured by an ASIC (Application Specific Integrated Circuit) or the like and provided as a color processing apparatus. Alternatively, the present invention may adopt a form in which the function (see FIG. 3) of the color processing unit 120 described above is provided as a program that implements software.
Furthermore, the program according to the present invention can be provided as a recording medium such as an optical disk in which the program is stored, and can be downloaded to a computer via a network such as the Internet, and can be installed and used. Can also be provided.

(4) Modification 4
The image forming apparatus according to the present invention is not limited to the electrophotographic method, and can employ various recording methods. For example, the image forming apparatus according to the present invention may be an inkjet method or an offset printing method. Further, the color components used in the present invention are not limited to four colors of cyan, magenta, yellow, and black, and color signals corresponding to other color materials can be appropriately used.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the structure of an image formation part. It is a flowchart which shows the color process which a color process part performs. It is a figure explaining the effect of an embodiment. It is a block diagram which shows schematically the total amount restriction | limiting of the conventional color material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 110 ... Image input part 120 ... Color processing part 121 ... Input part 122 ... Subtraction part 123 ... Limit value setting part 124 ... Adder part 125 ... CMY adjustment part 126 ... Output part , 130 ... Image forming unit, 140 ... Control unit

Claims (4)

An input color signal representing the amount of color material used by the image forming apparatus, and an input means for inputting an input color signal including a black component color signal and other color component color signals;
When the minimum value of the color signal of the other color component input by the input unit is not 0, the color signal of the black component and the color signal of the other color component input by the input unit, and the output color signal Determining an adjustment value of the black component color signal based on a limit value that defines the total amount of the image signal, and when the minimum value is 0, a determination unit that sets the adjustment value to 0 ;
Subtracting means for subtracting the adjustment value determined by the determining means from the color signals of other color components input by the input means;
Adding means for adding the adjustment value determined by the determining means to the color signal of the black component input by the input means;
The adjustment value is subtracted by the subtraction unit based on the color signal of the black component to which the adjustment value is added by the addition unit, the color signal of the other color component from which the adjustment value is subtracted by the subtraction unit, and the limit value. Adjusting means for adjusting the color signals of the other color components that have been
Color processing comprising: output means for outputting, as an output color signal, the color signal of the black component to which the adjustment value is added by the addition means and the color signal of the other color component adjusted by the adjustment means apparatus. There are a plurality of color signals of the other color components,
The determining means includes
When the minimum value of the color signal of the other color component input by the input unit is not 0, the sum of the color signal of the black component and the color signal of the other color component input by the input unit is the limit value. The value obtained by dividing the subtracted value by the value obtained by doubling the minimum value is α, and the value obtained by dividing the maximum amount of color material by subtracting the black component color signal input by the input means by the minimum value. _Is determined to be a value obtained by multiplying α or α _{max whichever} is smaller by the minimum value as the adjustment value,
The adjusting means includes
A value obtained by subtracting the color signal of the black component to which the adjustment value is added from the limit value from the limit value is β, and each of the plurality of color signals of the other color components from which the adjustment value is subtracted by the subtraction unit, The color processing apparatus according to claim 1, wherein adjustment is performed by multiplying by β and dividing by the sum of the plurality of color signals. Input means for inputting an input color signal that represents the amount of color material used by the device itself, and that includes an input color signal including a black component color signal and other color component color signals;
When the minimum value of the color signal of the other color component input by the input unit is not 0, the color signal of the black component and the color signal of the other color component input by the input unit, and the output color signal Determining an adjustment value of the black component color signal based on a limit value that defines the total amount of the image signal, and when the minimum value is 0, a determination unit that sets the adjustment value to 0 ;
Subtracting means for subtracting the adjustment value determined by the determining means from the color signals of other color components input by the input means;
Adding means for adding the adjustment value determined by the determining means to the color signal of the black component input by the input means;
The adjustment value is subtracted by the subtraction unit based on the color signal of the black component to which the adjustment value is added by the addition unit, the color signal of the other color component from which the adjustment value is subtracted by the subtraction unit, and the limit value. Adjusting means for adjusting the color signals of the other color components that have been
In accordance with the color signal of the black component to which the adjustment value is added by the addition unit and the color signal of the other color component adjusted by the adjustment unit, an image is formed using a color material corresponding to the black component and the other color component. An image forming apparatus comprising: an image forming unit that forms the image. Computer
An input color signal representing the amount of color material used by the image forming apparatus, and an input means for inputting an input color signal including a black component color signal and other color component color signals;
When the minimum value of the color signal of the other color component input by the input unit is not 0, the color signal of the black component and the color signal of the other color component input by the input unit, and the output color signal Determining an adjustment value of the black component color signal based on a limit value that defines the total amount of the image signal, and when the minimum value is 0, a determination unit that sets the adjustment value to 0 ;
Subtracting means for subtracting the adjustment value determined by the determining means from the color signals of other color components input by the input means;
Adding means for adding the adjustment value determined by the determining means to the color signal of the black component input by the input means;
The adjustment value is subtracted by the subtraction unit based on the color signal of the black component to which the adjustment value is added by the addition unit, the color signal of the other color component from which the adjustment value is subtracted by the subtraction unit, and the limit value. Adjusting means for adjusting the color signals of the other color components that have been
A program for causing a black component color signal to which an adjustment value has been added by the adding means and a color signal of another color component adjusted by the adjusting means to function as an output color signal.

Images