JP5278257B2 - Color processing apparatus, image processing apparatus, and program - Google Patents

Description

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

Execute toner save processing only in the black and white image area, or execute toner save processing in the image area desired by the operator in the black and white image area or color image area, and execute each area at the desired toner save rate Such a technique is known (for example, see Patent Document 1).
Also, RGB image data obtained by scanning a document with a CCD is converted from an RGB color space to a Lab color space. In the toner saving mode, L (lightness) is used in image processing such as ground color correction and color correction. A technique is also known in which the component is made larger (brighter) than usual, the Lab color space is converted into a CMYK color space, the image data converted into CMYK is binarized, and output to a printer (for example, Patent Document 2). reference).

Japanese Patent Laid-Open No. 11-308450 JP 2005-86289 A

  An object of the present invention is to reduce the usage amount of a single color material based on a color signal obtained by monochromatizing a color signal composed of a plurality of color components while suppressing the influence on the processing performance.

The invention according to claim 1 comprises a detecting means for detecting a signal indicating that an instruction to reduce the amount of color material used has been made, and a plurality of color components when the signal is detected by the detecting means. Instead of using the first conversion formula instead of the predetermined first conversion formula, the monochromatic color material for converting the first color signal into the second color signal of the single color is used. A color processing apparatus comprising: a monochromizing processing unit that performs using a second conversion formula that reduces the amount of use of the color.
According to a second aspect of the present invention, the first conversion formula is obtained by multiplying each color component of the plurality of color components by a coefficient determined in advance for each color component, and adding the result. An equation for converting a color signal into a luminance signal, wherein the second conversion equation is a new coefficient for each color component and a new coefficient for at least one color component. 2. The color processing apparatus according to claim 1, wherein is a formula for multiplying and adding a new coefficient larger than the predetermined coefficient for the at least one color component.
According to a third aspect of the present invention, there is provided the color processing apparatus according to the second aspect, further comprising a determining unit that determines the new coefficient based on a feature amount of the first color signal. is there.
According to a fourth aspect of the present invention, the determining means multiplies the predetermined coefficient for each color component of the plurality of color components by a correction coefficient common to all the color components of the plurality of color components. The color processing apparatus according to claim 3, wherein the new coefficient is determined.
According to a fifth aspect of the present invention, the feature amount is a value of any one of brightness and luminance of a color reproduced by the first color signal, and the determining unit is configured to select each color of the plurality of color components. 5. The color processing apparatus according to claim 3, wherein the new coefficient is determined by multiplying the predetermined coefficient for a component by a larger correction coefficient as the value is smaller. 6.
According to a sixth aspect of the present invention, the determining means multiplies the predetermined coefficient for each color component of the plurality of color components by a correction coefficient that differs for each of the plurality of color components, thereby obtaining the new coefficient. The color processing apparatus according to claim 3, wherein:
According to a seventh aspect of the present invention, the feature amount is a difference between a maximum value of the values of the plurality of color components constituting the first color signal and a value of each color component of the plurality of color components, The determining means determines the new coefficient by multiplying the predetermined coefficient for each color component of the plurality of color components by a correction coefficient larger than 1 if the difference is equal to or less than a threshold value. 7. The color processing apparatus according to claim 3, wherein the color processing apparatus is a color processing apparatus.
The invention according to claim 8 is characterized in that the determining means multiplies the predetermined coefficient for each color component of the plurality of color components by the correction coefficient that is larger as the difference is smaller. The color processing apparatus according to claim 1.
The invention according to claim 9 is the acquisition unit that acquires the first color signal composed of a plurality of color components and the acquisition unit that receives the instruction to reduce the amount of color material used. Instead of using the first conversion formula instead of the predetermined first conversion formula, the monochromatic color material for converting the first color signal into the second color signal of the single color is used. Monochromatic processing means performed using a second conversion formula for reducing the amount of use, and output means for outputting the second color signal obtained by monochromatic processing by the monochromatic processing means to a printing mechanism. An image processing apparatus is provided.
According to a tenth aspect of the present invention, there is provided a function of detecting a signal indicating that the computer is instructed to reduce the amount of use of the color material, and a first composed of a plurality of color components when the signal is detected. The monochromatic processing for converting the color signal of the first color signal into the second color signal of the single color uses the monochrome color material instead of using the first conversion formula instead of the predetermined first conversion formula. This is a program for realizing the function performed using the second conversion formula for reducing the amount.

According to the first aspect of the present invention, it is possible to reduce the usage amount of a single color material based on a color signal obtained by monochromatizing a color signal composed of a plurality of color components while suppressing the influence on the processing performance.
According to invention of Claim 2, compared with the case where it does not have this structure, the usage-amount of a monochrome color material can be reduced by a simple method.
According to the third aspect of the present invention, it is possible to reduce the usage amount of a single color material based on a signal obtained by making the color signal monochromatic by reflecting the characteristic amount of the color signal composed of a plurality of color components.
According to the fourth aspect of the present invention, the configuration for generating the conversion formula for reducing the amount of the single color material used can be simplified as compared with the case where the present configuration is not provided.
According to the fifth aspect of the present invention, the degree of reduction in the amount of use of a single color material based on a color signal obtained by monochromatizing a color signal having low brightness or luminance is greater than that in the case where the present configuration is not provided. can do.
According to the sixth aspect of the present invention, the degree of reduction in the usage amount of the single color material can be changed for each color region.
According to the invention of claim 7, compared to the case where the present configuration is not provided, the degree of reduction in the amount of use of a single color material based on a color signal obtained by monochromatizing a color signal composed of a plurality of color components is reduced. It can be finely controlled.
According to the eighth aspect of the present invention, compared with the case where the present configuration is not provided, the degree of reduction in the amount of use of a single color material based on a color signal obtained by monochromatizing a color signal composed of a plurality of color components is reduced. Even finer control is possible.
According to the ninth aspect of the present invention, it is possible to reduce the usage amount of a single color material based on a color signal obtained by monochromatizing a color signal composed of a plurality of color components while suppressing the influence on the processing performance.
According to the tenth aspect of the present invention, it is possible to reduce the usage amount of a single color material based on a color signal obtained by monochromatizing a color signal composed of a plurality of color components while suppressing the influence on the processing performance.

It is the figure which showed the structural example of the image processing apparatus with which embodiment of this invention is applied. 6 is a graph for explaining a K toner reduction method according to the first embodiment of the present invention. It is the block diagram which showed the function structural example of the K production | generation part in the 1st Embodiment of this invention. It is the flowchart which showed the operation example of the K production | generation part in the 1st Embodiment of this invention. It is a graph for demonstrating the K toner reduction method in the 2nd Embodiment of this invention. It is a graph for demonstrating the K toner reduction method in the 2nd Embodiment of this invention. It is the block diagram which showed the function structural example of the K production | generation part in the 2nd Embodiment of this invention. It is the flowchart which showed the operation example of the K production | generation part in the 2nd Embodiment of this invention. 10 is a table for explaining a K toner reduction method according to a third embodiment of the present invention. It is the block diagram which showed the function structural example of the K production | generation part in the 3rd Embodiment of this invention. It is the flowchart which showed the operation example of the K production | generation part in the 3rd Embodiment of this invention. It is the figure which showed the hardware structural example of the computer which can implement | achieve embodiment of this invention.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 shows a configuration example of an image processing apparatus 10 in the present embodiment.
As illustrated, the image processing apparatus 10 includes a CMY generation unit 20, a UCR (Under Color Removal) unit 30, and a CMYK gradation correction unit 40. Further, a K generation unit 50, a K gradation correction unit 60, and a selector 70 are provided.

The CMY generation unit 20 uses a three-dimensional lookup table from color data expressed in R (red), G (green), and B (blue) colors (hereinafter, referred to as “RGB data”) to generate C ( Color data represented by each color of cyan, M (magenta), and Y (yellow) (hereinafter referred to as “CMY data”) is generated and output. Here, the RGB data may be obtained by interpreting PDL (Page Description Language) data received from a PC (Personal Computer) (not shown), or obtained by reading an image with a scanner (not shown). It may be what was made.
The UCR unit 30 generates K (black) data from the CMY data output from the CMY generation unit 20 by UCR processing (under color removal processing), and expresses color data (hereinafter referred to as C, M, Y, and K colors). , “CMYK data”).
The CMYK gradation correction unit 40 performs gradation correction on the CMYK data output from the UCR unit 30 using data related to TRC (Tone Reproduction Curve), and outputs gradation-corrected CMYK data.

The K generation unit 50 generates K data from RGB data and outputs it.
The K gradation correction unit 60 performs gradation correction on the K data output from the K generation unit 50 using data relating to TRC, and outputs K data subjected to gradation correction.
The selector 70 selects the CMYK data output from the CMYK gradation correction unit 40 when the color mode is selected, and the K data output from the K gradation correction unit 60 when the monochrome mode is selected. Output to a printing mechanism (not shown). In the latter case, information that the C, M, and Y toners are not used is also sent to the printing mechanism.

  Although FIG. 1 shows a configuration example of the image processing apparatus 10 in the color image forming apparatus, the present invention can also be applied to a monochrome image forming apparatus. In this case, the image processing apparatus 10 does not include the CMY generation unit 20, the UCR unit 30, the CMYK gradation correction unit 40, and the selector 70, and RGB data is input only to the K generation unit 50 and converted into K data. Gradation correction is performed by the gradation correction unit 60 and output to a printing mechanism (not shown) without going through the selector 70.

Incidentally, the K generation unit 50 of the image processing apparatus 10 in FIG. 1 generally performs graying processing, that is, processing for converting RGB data into grayscale data, using a predetermined conversion formula. Here, a representative example of the predetermined conversion formula is a conversion formula (hereinafter referred to as “NTSC conversion formula”) used in NTSC (National Television Standards Committee) graying processing. Is done.
Gray = 0.299 × R + 0.58 × G + 0.11 × B (Formula 1)
In this equation, R, G, and B represent R component, G component, and B component values in RGB data, respectively, and Gray represents a gray scale value. Further, “0.299” for the R component, “0.58” for the G component, and “0.11” for the B component are referred to as NTSC coefficients.

However, when the amount of K toner is uniformly reduced by using the NTSC conversion formula as it is, the amount of K toner in the high density region is small and the K toner is reduced in accordance with the high density side. Further, the amount of reduction of K toner in the halftone area and the highlight area increases, and there arises a problem that the image information is lost and cannot be grasped.
Therefore, in the present embodiment, the conversion formula for converting RGB data into K data is changed from the NTSC conversion formula to a conversion formula for reducing the amount of K toner (hereinafter referred to as “toner saving conversion formula”).

Hereinafter, a method of changing the conversion formula will be described as the first to third embodiments.
[First Embodiment]
In the first embodiment, the coefficient of the conversion equation used in the graying process is changed.
FIG. 2 is a graph showing the K amount when the input color data changes.
First, A indicates the amount of K when the K toner reduction process is not performed, that is, when the above Equation 1 is used.

B and C indicate the K amount when the conversion equation is changed as in the following equation 2.
Gray = α ₁ × 0.299 × R + α ₂ × 0.58 × G + α ₃ × 0.11 × B (Formula 2)
Among these, in B, the correction coefficients α ₁ , α ₂ , and α ₃ for the NTSC coefficient are the same values and are larger than 1. Thereby, the K amount is reduced as a whole, but the reduction amount of the blue region indicated by ΔK _B1 is smaller than the reduction amount of the yellow region indicated by ΔK _Y1 .

On the other hand, in C, correction coefficients α ₁ , α ₂ , and α ₃ for the NTSC coefficient are different values, and α ₃ is set larger than the other correction coefficients. Thus, reduction of the blue region indicated by [Delta] K _B2 is increased.
That is, when K toner reduction processing is performed on the K value calculated by the NTSC conversion formula, if processing is performed according to a region where the amount of K is large, K toner in the originally bright color region will be excessively reduced.
Therefore, in C, by changing the correction coefficient for the NTSC conversion formula for each color component, for example, in the region from yellow to cyan, the reduction amount of K toner is reduced, and the region having a large K amount (from blue) In the area up to magenta), the reduction amount of K toner is increased, and the reduction amount is optimized for each hue region.
In addition, since both B and C only change the NTSC conversion formula, even if the toner saving process is performed, the performance is not affected.

Next, the K generation unit 50 for realizing such a method will be described.
FIG. 3 is a diagram illustrating a functional configuration example of the K generation unit 50 according to the first embodiment.
As shown in the figure, the K generation unit 50 according to the first embodiment includes a mode signal acquisition unit 51, a toner saving conversion type storage unit 52, a graying processing unit 53, and a density calculation unit 54. .

When a mode for reducing the amount of toner used (hereinafter referred to as “toner saving mode”) is designated, the mode signal acquisition unit 51 indicates that a toner saving mode has been designated (hereinafter referred to as “toner saving mode”). Signal)). In the present embodiment, a mode signal acquisition unit 51 is provided as an example of a detection unit that detects a signal.
The toner saving conversion type storage unit 52 stores the toner saving conversion type. Here, as the toner saving conversion formula, the formula itself may be stored, the coefficients for the R, G, and B components may be stored, or the NTSC coefficient is calculated from the coefficients for the R, G, and B components. Only the corrected correction coefficient may be stored.

If no toner save mode signal is given from the mode signal acquisition unit 51, the graying processing unit 53 converts the RGB data into grayscale data using the NTSC conversion formula and outputs the grayscale data. On the other hand, if a toner save mode signal is given from the mode signal acquisition unit 51, the toner save conversion formula is read from the toner save conversion formula storage unit 52, and the RGB data is converted into grayscale data using the toner save conversion formula. Output. In this embodiment, an NTSC conversion formula is used as an example of the first conversion formula, and a toner saving conversion formula is used as an example of the second conversion formula. The second conversion is used instead of the first conversion formula. As an example of a monochromatic processing unit that performs monochromatic processing using an expression, a graying processing unit 53 is provided.
The density calculation unit 54 calculates the density that is the source of the K toner amount from the gray scale data output by the graying processing unit 53.

Next, the operation of the K generation unit 50 in the first embodiment will be described.
FIG. 4 is a flowchart illustrating an operation example of the K generation unit 50 according to the first embodiment.
In the K generation unit 50, first, it is determined whether or not the mode signal acquisition unit 51 has acquired a toner save mode signal (step 201).
As a result, when the mode signal acquisition unit 51 determines that the toner save mode signal has been acquired, the graying processing unit 53 reads the toner save conversion formula from the toner save conversion formula storage unit 52 (step 202). Then, the NTSC conversion formula held by itself is replaced with this toner saving conversion formula, and this toner saving conversion formula is held (step 203).
On the other hand, when the mode signal acquisition unit 51 does not determine that the toner saving mode signal has been acquired, the graying processing unit 53 holds the NTSC conversion formula held by itself without replacing it with another conversion formula. .
Thereafter, the graying processing unit 53 converts the RGB data into grayscale data using a conversion formula held by itself at that time (step 204). Then, K data is generated from the gray scale data and output (step 205).

[Second Embodiment]
In the second embodiment, the coefficient of the conversion formula used in the graying process is changed according to the input color data. In particular, in the second embodiment, the coefficient of the conversion equation is changed according to the brightness obtained from the input color data.
FIG. 5A is a graph showing values obtained by converting the color data given in FIG. 2 into lightness.
In the figure, La represents the lowest lightness that is the lightness of the point with the lowest lightness, and Lb represents the highest lightness that is the lightness of the point with the highest lightness.

Then, in the second embodiment, as shown in FIG. 5 (b), it becomes minimum at the maximum brightness Lb, determines a correction coefficient beta _L having a maximum in the minimum lightness La. In addition, the correction coefficient β _L for the brightness between the maximum brightness Lb and the minimum brightness La is increased when the brightness is low, and is decreased when the brightness is high.
In this case, the conversion formula is as shown in the following formula 3.
Gray = β _L × 0.299 × R + β _L × 0.58 × G + β _L × 0.11 × B (Formula 3)
Further, as in the following Expression 4, it may be multiplied by the correction coefficient used in the first embodiment.
Gray = α ₁ × β _L × R + α ₂ × β _L × G + α ₃ × β _L × B (Formula 4)

As described above, in this embodiment, the K toner reduction amount is increased in the high density area of the input color data, and the K toner reduction amount is suppressed in the high brightness area. is there.
FIG. 6 is a graph showing the reduction of K toner as in FIG.
In the figure, A is the amount of K when K toner reduction processing is not performed for low-lightness color data, and B is the amount of K when the conversion formula is changed to Equation 3 for the same color data as A. Respectively. A ′ represents the K amount when the input color data is not subjected to the K toner reduction process for the color data whose brightness is higher than A, and B ′ represents the conversion formula for the same color data as A ′. The amounts of K when changed as in Equation 3 are shown. For example, as can be seen from the fact that the reduction amount indicated by ΔK ₂ is smaller than the reduction amount indicated by ΔK ₁ , the reduction amount of K toner decreases as the lightness increases even for the same hue.
In addition, the present embodiment provides a conversion formula corresponding to the lightness of each color region by using it together with the correction coefficient for each color component as shown in Formula 4.

In the above, the correction coefficient beta _L, was determined using the minimum brightness La and maximum brightness Lb in all hues, not limited to this. For example, the correction coefficient β _L may be calculated using the minimum brightness and the maximum brightness in a predetermined hue.
In the above description, the coefficient of the conversion formula is changed according to the brightness, but the coefficient of the conversion formula may be changed according to the luminance.
Or, if the color data is high saturation data, multiply by a large correction coefficient, and if the color data is low saturation data, multiply by a small correction coefficient, so that the case of low saturation than in the case of high saturation However, the reduction amount of K toner may be reduced.

Next, the K generation unit 50 for realizing such a method will be described. In the following description, it is assumed that a conversion expression such as Expression 3 is obtained according to lightness.
FIG. 7 is a diagram illustrating a functional configuration example of the K generation unit 50 according to the second embodiment.
As shown in the figure, the K generation unit 50 in the second embodiment includes a mode signal acquisition unit 51, a toner saving conversion type storage unit 52, a graying processing unit 53, a density calculation unit 54, and a correction coefficient calculation. A unit 56 and a toner-saving conversion formula generation unit 57. Note that the mode signal acquisition unit 51, the toner-saving conversion type storage unit 52, the graying processing unit 53, and the density calculation unit 54 are the same as those described in the first embodiment, and thus description thereof is omitted here.

Correction coefficient calculating unit 56 based on the RGB data to calculate a correction coefficient beta _L.
The toner save conversion formula generation unit 57 uses the correction coefficient β _L calculated by the correction coefficient calculation unit 56 to generate a toner save conversion formula. If only the correction coefficient is stored in the toner save conversion formula storage unit 52, the toner save conversion formula generation unit 57 may not be provided. In the present exemplary embodiment, a toner saving conversion expression generation unit 57 is provided as an example of a determination unit that determines a new coefficient.

Next, the operation of the K generation unit 50 in the second embodiment will be described.
First, an operation when a toner save conversion formula is generated and stored in the toner save conversion storage unit 52 will be described.
FIG. 8 is a flowchart showing an operation example of the K generation unit 50 at this time.
In the K generation unit 50, first, the correction coefficient calculation unit 56 calculates the lightness L from the RGB data by a known calculation method (step 221).
Further, the correction coefficient calculation unit 56 obtains the function f (L) for determining the correction coefficient beta _L (step 222). Here, f (L) takes a maximum value when L = La and a minimum value 1 when L = Lb, and satisfies the condition “if L1 <L2, f (L1) ≧ f (L2)”. For example, it is assumed that the function is as shown in FIG.
Further, the correction coefficient calculation unit 56 substitutes the lightness L calculated in step 221 for the function acquired in step 222 to obtain a correction coefficient β _L (step 223).
Thus, the toner save conversion formula generating unit 57 multiplies the correction coefficient beta _L each NTSC coefficient in NTSC conversion formula held by itself, to produce a toner save conversion equation (step 224).
Then, the toner save conversion formula generation unit 57 stores the toner save conversion formula thus generated in the toner save conversion formula storage unit 52 (step 225).

  When the toner save conversion formula is stored in the toner save conversion formula storage unit 52 in this way, the K generation unit 50 converts the toner save conversion formula into the toner save conversion formula by the same processing as described in the first embodiment. Used to convert RGB data to K data.

[Third Embodiment]
In the third embodiment, the coefficient of the conversion formula used in the graying process is changed according to the input color data. However, in the third embodiment, the coefficients of the conversion formula are changed according to the values of the RGB color components in the input color data. Specifically, when the difference between the maximum value of all RGB color components and the value of a certain RGB color component is smaller than a predetermined threshold, a correction coefficient larger than 1 for that color component of the conversion formula give. At this time, the correction coefficient larger than 1 is changed according to the difference. On the other hand, if the difference is greater than or equal to the threshold, the correction coefficient for that color component in the conversion formula is 1. That is, the coefficient for the color component remains the initial coefficient.

FIG. 9 illustrates such a correction coefficient determination method. In the following description, the threshold value is assumed to be 50.
For example, in the first line, the maximum value of each color component of RGB is 255. Accordingly, the difference between the value of R and the maximum value is 0, which is equal to or less than the threshold value, and thus γ ₁ is set to 1.5, which is a value greater than 1. Further, since the difference between the value and the maximum value of G is 255, and the threshold value or more, 1 is set in the gamma _2. Moreover, the difference is also 255 next to the value and the maximum value of B, because it is above the threshold, the gamma ₃ 1 is set.
In the second row, values are set in γ ₁ and γ ₃ as in the first row. In contrast, the gamma _2, the difference is 5 next to the value and the maximum value of G, because it is below the threshold, 1.25 is a value greater than 1 is set.

Further, even in the 19th line, the maximum value of each color component of RGB is 255. Therefore, since the difference between the value and the maximum value of R is 255, and the threshold value or more, 1 is set for the gamma _1. Further, the difference between the value and the maximum value of G is next 127, since it is above the threshold, the gamma ₂ 1 is set. Further, the difference becomes zero between the value and the maximum value of B, because it is below the threshold, 2.0 to gamma ₃ is a value greater than 1 is set.
In the 20th line, values are set in γ ₁ and γ ₃ as in the 19th line. On the other hand, since the difference between the G value and the maximum value is 15 and is equal to or less than the threshold value, γ ₂ is set to 1.8, which is a value larger than 1.
In the figure, both the difference between the G value and the maximum value and γ ₂ are smaller in the second row than in the twentieth row. This is because the hue is different between the second line and the twentieth line.

In this case, the conversion formula is as shown in the following formula 5.
Gray = γ ₁ × β _L × R + γ ₂ × β _L × G + γ ₃ × β _L × B (Formula 5)
In this case, the value obtained by multiplying γ ₁ , γ ₂ , γ ₃ by β _L is not a new coefficient, but the value obtained by multiplying γ ₁ , γ ₂ , γ ₃ by the NTSC coefficient is a new coefficient. The conversion formula may be obtained.

Next, the K generation unit 50 for realizing such a method will be described.
FIG. 10 is a diagram illustrating a functional configuration example of the K generation unit 50 according to the third embodiment.
As shown in the figure, the K generation unit 50 according to the third embodiment includes a mode signal acquisition unit 51, a toner saving conversion type storage unit 52, a graying processing unit 53, a density calculation unit 54, and a maximum value calculation. Unit 55, correction coefficient calculation units 56r, 56g, and 56b, and a toner-saving conversion formula generation unit 57. Note that the mode signal acquisition unit 51, the toner-saving conversion type storage unit 52, the graying processing unit 53, and the density calculation unit 54 are the same as those described in the first embodiment, and thus description thereof is omitted here.

The maximum value calculation unit 55 obtains the maximum value of each color component of RGB.
The correction coefficient calculation unit 56r calculates the correction coefficient γ ₁ based on the maximum value calculated by the maximum value calculation unit 55 and the R value.
Correction coefficient calculating unit 56g, based on the value of the maximum value and the G maximum value calculating unit 55 is calculated, to calculate a correction coefficient gamma _2.
Correction coefficient calculating unit 56b, based on the value of the maximum value and B the maximum value calculating unit 55 is calculated, to calculate a correction coefficient gamma _3.
The toner-saving conversion formula generation unit 57 generates a toner-saving conversion formula using the correction coefficients γ ₁ , γ ₂ , and γ ₃ calculated by the correction coefficient calculation units 56r, 56g, and 56b, respectively. If only the correction coefficient is stored in the toner save conversion formula storage unit 52, the toner save conversion formula generation unit 57 may not be provided. In the present exemplary embodiment, a toner saving conversion expression generation unit 57 is provided as an example of a determination unit that determines a new coefficient.

Next, the operation of the K generation unit 50 in the third embodiment will be described.
First, an operation when a toner save conversion formula is generated and stored in the toner save conversion storage unit 52 will be described.
FIG. 11 is a flowchart showing an operation example of the K generation unit 50 at this time.
In the K generation unit 50, first, the maximum value calculation unit 55 obtains the maximum value M among the values of the respective RGB color components (step 241).
Next, the correction coefficient calculation unit 56r determines whether or not the difference between the maximum value M and the R value is smaller than the threshold value Th (step 242). If the difference is smaller than the threshold value Th, a correction coefficient γ ₁ is obtained according to the magnitude of the difference (step 243). If the difference is greater than or equal to the threshold Th, the correction coefficient γ _{1 is set} to 1 (step 244).

Further, the correction coefficient calculation unit 56g determines whether or not the difference between the maximum value M and the G value is smaller than the threshold Th (Step 245). If the difference is smaller than the threshold value Th, a correction coefficient γ ₂ is obtained according to the magnitude of the difference (step 246). Further, the difference is equal to or larger than the threshold Th, the correction coefficient gamma ₂ and 1 (step 247).
Further, the correction coefficient calculation unit 56b determines whether or not the difference between the maximum value M and the value B is smaller than the threshold value Th (step 248). If the difference is smaller than the threshold Th, a correction coefficient γ ₃ is obtained according to the magnitude of the difference (step 249). If the difference is greater than or equal to the threshold Th, the correction coefficient γ _{3 is set} to 1 (step 250).

As a result, the toner saving conversion formula generation unit 57 uses the correction coefficient γ ₁ calculated by the correction coefficient calculation unit 56r as a coefficient for the R component, and uses the correction coefficient γ ₂ calculated by the correction coefficient calculation unit 56g as the G component. coefficients, the coefficients respectively determined for the B component by using the correction coefficient gamma ₃ the correction coefficient calculating unit 56b is calculated to produce a toner save conversion formula for (step 251).
Then, the toner save conversion formula generation unit 57 stores the toner save conversion formula thus generated in the toner save conversion formula storage unit 52 (step 252).

  When the toner save conversion formula is stored in the toner save conversion formula storage unit 52 in this way, the K generation unit 50 converts the toner save conversion formula into the toner save conversion formula by the same processing as described in the first embodiment. Used to convert RGB data to K data.

This is the end of the description of the present embodiment.
In this embodiment, the conversion coefficient used in the graying process is changed according to the input color data. However, the coefficient may be changed according to the document to be processed. For example, in the first embodiment, it is conceivable to increase the correction coefficient α1 when a document to be processed includes a large amount of R component.
In this embodiment, the graying process is assumed. However, the present invention can also be applied to a monochromatic process that converts input color data into single color data other than gray.

Incidentally, the image processing apparatus 10 according to the present embodiment may be realized in an image forming apparatus such as a printer, but can also be realized in a general-purpose computer such as a PC.
Hereinafter, the hardware configuration of such a general-purpose computer as the computer 90 will be described.

FIG. 12 is a diagram illustrating a hardware configuration of the computer 90.
As shown in the figure, the computer 90 includes a CPU (Central Processing Unit) 91 as a calculation means, a main memory 92 as a storage means, and a magnetic disk device (HDD: Hard Disk Drive) 93. Here, the CPU 91 executes various types of software such as an OS (Operating System) and applications to realize the above-described functions. The main memory 92 is a storage area for storing various software and data used for execution thereof, and the magnetic disk device 93 is a storage area for storing input data for various software, output data from various software, and the like. .
Further, the computer 90 includes a communication I / F 94 for performing communication with the outside, a display mechanism 95 including a video memory and a display, and an input device 96 such as a keyboard and a mouse.

  The program for realizing the present embodiment can be provided not only by communication means but also by storing it in a recording medium such as a CD-ROM.

50... K generation unit 51. Mode signal acquisition unit 52. Toner-saving conversion storage unit 53. Graying processing unit 54. Density calculation unit 55 55 Maximum value calculation unit 56 r, 56 g, 56 b. Calculation unit, 57... Toner-saving conversion formula generation unit

Claims (10)

Detection means for detecting a signal that an instruction to reduce the amount of color material used has been made;
When the signal is detected by the detecting means, a monochromatic process for converting a first color signal composed of a plurality of color components into a second color signal of a single color is performed using a predetermined first conversion equation. Instead, a color processing apparatus comprising: a monochromatic processing unit that uses a second conversion formula that reduces the amount of use of the monochrome color material compared to the case of using the first conversion formula. . The first conversion equation is an equation for converting the first color signal into a luminance signal by adding each color component multiplied by a predetermined coefficient to each color component. And
In the second conversion formula, a new coefficient for each color component is added to each color component of the plurality of color components, and a new coefficient for at least one color component is determined in advance for the at least one color component. The color processing apparatus according to claim 1, wherein the color processing apparatus is an expression that multiplies and adds a new coefficient larger than the calculated coefficient.   The color processing apparatus according to claim 2, further comprising a determining unit that determines the new coefficient based on a feature amount of the first color signal.   The determining means determines the new coefficient by multiplying the predetermined coefficient for each color component of the plurality of color components by a correction coefficient common to all the color components of the plurality of color components. The color processing apparatus according to claim 3. The feature amount is one of values of brightness and luminance of a color reproduced by the first color signal,
4. The determining means determines the new coefficient by multiplying the predetermined coefficient for each color component of the plurality of color components by a larger correction coefficient as the value is smaller. Or the color processing apparatus of 4.   The determining means determines the new coefficient by multiplying the predetermined coefficient for each color component of the plurality of color components by a different correction coefficient for each of the plurality of color components. Item 4. The color processing apparatus according to Item 3. The feature amount is a difference between the maximum value of the plurality of color components constituting the first color signal and the value of each color component of the plurality of color components,
The determining means determines the new coefficient by multiplying the predetermined coefficient for each color component of the plurality of color components by a correction coefficient larger than 1 if the difference is equal to or less than a threshold value. The color processing apparatus according to claim 3, wherein the color processing apparatus is a color processing apparatus.   The color processing apparatus according to claim 7, wherein the determination unit multiplies the predetermined coefficient for each color component of the plurality of color components by the correction coefficient that is larger as the difference is smaller. Obtaining means for obtaining a first color signal comprising a plurality of color components;
A monochromatic process for converting the first color signal acquired by the acquisition unit into a second color signal of a single color when an instruction to reduce the amount of color material used is given. Instead of using the first conversion formula, a monochromization processing means that performs using a second conversion formula that reduces the amount of use of the color material of the single color compared to the case of using the first conversion formula;
An image processing apparatus, comprising: an output unit that outputs the second color signal obtained by the monochromating process by the monochromatic processing unit to a printing mechanism. On the computer,
A function to detect a signal that an instruction to reduce the amount of color material used has been made;
When the signal is detected, a monochromatic process for converting a first color signal composed of a plurality of color components into a single second color signal is performed instead of the predetermined first conversion formula. The program for implement | achieving the function performed using the 2nd conversion formula which reduces the usage-amount of the said monochrome color material rather than the case where the 1st conversion formula is used.

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