JP3122150U - Two color separation device - Google Patents

Abstract

Kind Code: A1 In a two-color separation apparatus that acquires color separation data of each color component of two-color separation based on color image data representing a color original, the brightness and density of the color original and the printed matter printed by two-color printing. Separation data is automatically acquired so that the brightness and density are comparable.
A color for generating CMY data based on RGB data of each pixel data of color image data and defining one color component in a color cube having three components of a C component, an M component, and a Y component A component definition plane is set, one color component data of the CMY data is acquired based on the distance between the CMY data and the color component definition plane, the density of the CMY data is calculated, and the density of the one color component data is calculated. And the difference data between the density of the CMY data and the density of one color component data is obtained, the other color component data is obtained as color separation data based on the difference data, and the one color component data is obtained. Acquired as color separation data for one color component.
[Selection] Figure 1

Description

  The present invention relates to a two-color separation apparatus that acquires separation data of each color component of two-color separation based on color image data representing a color original.

  Conventionally, it has been proposed to create a two-color plate based on color image data obtained by reading a color original with a scanner or color image data created on a personal computer and perform two-color printing.

Here, when performing two-color printing as described above, for example, color image data composed of RGB data is converted into CMYK data, and C component data and M component data of the CMYK data are used. It is common practice to create a two-color plate (see Non-Patent Document 1).
Infomedia Co., Ltd., “Two-color Printing Design & Techniques”, First Edition, Works Corporation, March 1, 2003

  However, as described above, if two plates are created using only the data of the C component and the M component and printed in two colors, the print result becomes darker or thinner for each color document, and the color The density (brightness) of the original cannot be reproduced.

  Therefore, there is also a method of performing a print test while adjusting the density for each color document using software that edits color image data in order to make it as close as possible to the density of the color document, but this method is very laborious. Yes, it depends on the skill of the person in charge.

  Further, when the two-color plate is created using the C component data and the M component data as described above, for example, when the Y component data is included in the color image data, The Y component image does not appear in the two-color printing.

  Therefore, for example, Non-Patent Document 1 proposes a method of including data of the Y component in the data of the C component and the M component using software for editing the color image data. A method has been proposed in which the user specifies the proportion of the Y component to be included, such as 90% and the Y component of 10%.

  However, if the user specifies the ratio of the Y component as described above, the brightness and density of the printed matter printed by two-color printing may differ from the brightness and density of the color document. In order to make the lightness and density of the printed matter of two colors the same level as that of the color original, it is necessary for the user to repeatedly specify the Y component ratio and to perform printing, which is very time consuming and laborious. .

  In the present invention, when two-color printing is performed on a color document as described above, the color separation data is automatically generated so that the brightness and density of the color document and the brightness and density of the printed matter printed by the two-color printing are comparable. It is an object of the present invention to provide a two-color plate separation apparatus that can be obtained automatically and can obtain appropriate color separation data without labor and cost.

  A first two-color separation apparatus according to the present invention obtains separation data of each color component of a two-color separation based on CMY data of each pixel data constituting color image data representing a color original. In the apparatus, in a color cube having three axes of C component, M component, and Y component, a color component for setting a color component definition surface for defining one of the two color separation color components The definition surface setting unit, a first color component data acquisition unit that acquires one color component data of the CMY data based on the distance between the CMY data and the color component definition surface, and calculates the density of the CMY data Based on the difference data acquired by the difference data acquisition unit that calculates the density of one color component data and acquires the difference data between the density of the CMY data and the density of the one color component data 2 colors A second color component data acquisition unit that acquires the other color component data of each color component, and one color component data acquired by the first color component data acquisition unit among the color components of the two color separations Acquired as color separation data of one color component, and the other color component data acquired by the second color component data acquisition unit is acquired as color separation data of the other color component of each color component of the two color separations And a color separation data acquisition unit.

  A second two-color separation apparatus according to the present invention obtains separation data of each color component of two-color separation based on CMY data of each pixel data constituting color image data representing a color original. In the apparatus, in a color cube having three axes of C component, M component, and Y component, a color component for setting a color component definition surface for defining one of the two color separation color components The definition surface setting unit, a first color component data acquisition unit that acquires one color component data of the CMY data based on the distance between the CMY data and the color component definition surface, and calculates the density of the CMY data The difference data acquisition unit that calculates the density of one color component data and acquires the difference data between the density of the CMY data and the density of the one color component data, and part of the difference data acquired by the difference data acquisition unit The two color version A second color component data acquisition unit that acquires as the other color component data of the color components, one color component data acquired by the first color component data acquisition unit, and difference data other than part of the difference data; Is obtained as color separation data for one of the two color components, and the other color component data is used as color separation data for the other color component of the two color components. And a color separation data acquisition unit to be acquired.

  In the first and second color separation apparatuses of the present invention, when one color component is a red component and the other component is a black component, the color component definition surface is expressed by the following equation: , R <0, s> 0, t> 0.

rC + sM + tY = 0
A third two-color separation apparatus according to the present invention obtains separation data of each color component of two-color separation based on CMY data of each pixel data constituting color image data representing a color original. In the apparatus, in a color cube having three components of the C component, the M component, and the Y component, a first color component defining surface for defining a first color component among the color components of the two color separations; Based on the distance between the CMY data and the first color component definition surface, the color component definition surface setting unit for setting the second color component definition surface for defining the second color component, and the CMY data A first color component data acquisition unit that acquires first color component data and a second color component data of CMY data based on the distance between the CMY data and the second color component definition surface Color component data acquisition unit for calculating the density of CMY data A difference data acquisition unit that calculates the density of the first and second color component data, and acquires difference data between the sum of the first color component data and the second color component data and the density of the CMY data; , Based on the difference data acquired by the difference data acquisition unit, a supplement data acquisition unit that acquires supplement data of at least one of the first color component and the second color component, and a supplement acquired by the supplement data acquisition unit A color separation data acquisition unit that adds the data to at least one of the first color component data and the second color component data to acquire color separation data of the first and second color components; To do.

In the third two-color separation apparatus according to the present invention, the first color component is a red component, the second color component is a green component, and the first color component definition surface is represented by the following formula (1): In the case where r ₁ <0, s ₁ > 0, t ₁ > 0, and the second color component definition surface is represented by the following expression (2), r ₂ > 0, s ₂ <0, t ₂ > 0.

r ₁ C + s ₁ M + t ₁ Y = 0 (1)
r ₂ C + s ₂ M + t ₂ Y = 0 (2)
Further, when the first color component is a red component, the second color component is a blue component, and the first color component definition surface is expressed by the following expression (1), r ₁ <0, s ₁ > In the case where 0, t ₁ > 0 and the second color component definition surface is expressed by the following expression (2), r ₂ > 0, s ₂ > 0, and t ₂ <0.

r ₁ C + s ₁ M + t ₁ Y = 0 (1)
r ₂ C + s ₂ M + t ₂ Y = 0 (2)
Here, since the “density” is uniquely related to the brightness, the “density” here may be the brightness.

  Further, since the “CMY data” has a unique relationship with the RGB data, the “CMY data” here may be RGB data.

  According to the first two-color color separation apparatus of the present invention, CMY data is generated based on RGB data of each pixel data constituting color image data representing a color original, and C component, M component, and Y component are set to three. A color component definition plane for defining one color component in a color cube with two axes is set, and one color component data of CMY data is acquired based on the distance between the CMY data and the color component definition plane. , Calculating the density of the CMY data, calculating the density of one of the color component data, obtaining difference data between the density of the CMY data and the density of the one color component data, and based on the obtained difference data The other color component data is acquired, the one color component data is acquired as color separation data of one color component, and the other color component data is acquired as color separation data of the other color component. Thus, the density of the color document can be distributed between the color separation data of one color component and the color separation data of the other color component, and the printed matter printed by the color document brightness and density and two-color printing. Separation data having the same brightness and density can be automatically obtained, and appropriate separation data can be obtained without labor and cost.

  Further, it is possible to prevent a part of the image from being lost from the two-color printing as in the conventional two-color printing.

  According to the second two-color plate separation apparatus of the present invention, CMY data is generated based on RGB data of each pixel data constituting color image data representing a color original, and C component, M component, and Y component are set to three. A color component definition plane for defining one color component in a color cube with two axes is set, and one color component data of CMY data is acquired based on the distance between the CMY data and the color component definition plane. , Calculating the density of the CMY data, calculating the density of one of the color component data, obtaining the difference data between the density of the CMY data and the density of the one color component data, and part of the obtained difference data Is acquired as the other color component data, and an addition value between the one color component data and the difference data other than a part of the difference data is acquired as color separation data of one color component, and the other color component data is acquired. The so was to obtain as separation data of the other color components, it is possible to obtain the same effect as in the first two-color separation device.

  According to the third two-color plate separation apparatus of the present invention, CMY data is generated based on RGB data of each pixel data constituting color image data representing a color original, and C component, M component, and Y component are set to 3 A first color component definition plane for defining a first color component in a color cube having two axes and a second color component definition plane for defining a second color component are set, and CMY data The first color component data of the CMY data is acquired based on the distance between the CMY data and the first color component definition surface, and the second of the CMY data is acquired based on the distance between the CMY data and the second color component definition surface. And the density of the CMY data are calculated, the density of the first and second color component data is calculated, and the sum of the first color component data and the second color component data is calculated. The difference data with the density of CMY data is acquired and Based on the obtained difference data, supplemental data of at least one of the first color component and the second color component is acquired, and the acquired supplemental data is used as the first color component data and the second color component data. Since the color separation data of the first color component and the color separation data of the second color component are obtained by adding to at least one of the color data, the color original is divided into the color separation data of the first color component and the color separation data of the second color component. Can be distributed automatically, and color separation data can be automatically acquired so that the brightness and density of color originals are the same as the brightness and density of printed matter printed in two-color printing. Appropriate separation data can be acquired without cost.

  Hereinafter, a first embodiment of a two-color plate separation apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating a schematic configuration of the two-color plate separation apparatus according to the first embodiment. The two-color color separation apparatus of the first embodiment acquires color separation data for each color component used when performing two-color printing of red and black.

  As shown in FIG. 1, the two-color separation apparatus of the first embodiment includes a CMY data generation unit 10, a red component definition surface setting unit 12, a red component determination unit 14, and a red component data acquisition unit 16. A red component data density acquisition unit 18, a CMY data density acquisition unit 20, a difference data acquisition unit 22, a black component data acquisition unit 24, and a color separation data acquisition unit 26.

  The CMY data generation unit 10 converts RGB data of each pixel data constituting color image data output from a scanner or a personal computer into CMY data based on the following equation (3).

C = 1-R, M = 1-G, Y = 1-B (3)
The red component definition plane setting unit 12 is set with a red component definition plane for defining a red component in a color cube having three axes of C component, M component, and Y component as shown in FIG. Is. The red component definition surface is used for determining whether or not the CMY data includes a red component.

  Here, the red component definition surface can be expressed by the following equation (4).

rC + sM + tY = 0 (4)
r, s, and t are coefficients. The coefficients r, s, and t in the above equation may be set so as to satisfy the following conditions, for example.

1) The gray scale is on the red component definition surface.

2) The distance from red (R = 1, G = 0, B = 0) to the red component definition surface is the maximum.

3) The density is calculated in accordance with the ratio of the C, M, and Y coefficients in the following equation (5).

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (5)
First, from the condition 1), r + s + t = 0.

  Next, a distance d from a predetermined point in the color cube to the red component definition surface is expressed by the following equation (6).

d = | rC + sM + tY | / √ (r ² + s ² + t ² ) (6)
Since red (R = 1, G = 0, B = 0) is represented by (C, M, Y) = (0, 1, 1), the distance from red to the red component definition surface is maximum. In order to achieve this, | rC + sM + tY | may be maximized when (C, M, Y) = (0, 1, 1). That is, s and t may be set so as to have the same sign value.

  Here, for example, when s <t is set, when the distance d is obtained, the distance d increases when the Y component is large, and the distance d decreases when the M component is large. End up. Since it is desired to define that the red component increases as the M component increases, t <s is set so that the distance d increases when the M component is large.

  Further, for example, r = −7, s = 6, and t = 1 may be set so as to satisfy the condition 3).

  The red component determination unit 14 determines whether the input CMY data has a red component using the red component definition surface.

  The red component data acquisition unit 16 acquires red component data based on the distance between the CMY data and the red component definition plane when the red component determination unit 14 determines that the CMY data has a red component. is there.

  The red component data density acquisition unit 18 acquires the density of the red component data acquired by the red component data acquisition unit 16.

  The CMY data density acquisition unit 20 calculates the density of the CMY data converted by the CMY data generation unit 10.

  The difference data acquisition unit 22 acquires a difference between the CMY data density acquired by the CMY data density acquisition unit 20 and the density of the red component data acquired by the red component data density acquisition 18.

  The black component data acquisition unit 24 acquires the difference data acquired by the difference data acquisition unit 22 as black component data.

  The color separation data acquisition unit 26 acquires the red component data acquired by the red component data acquisition unit 16 as color separation data of the red component, and converts the black component data acquired by the black component data acquisition unit 24 into the black component data. It is acquired as version data.

  Next, the operation of the two-color plate separation apparatus of the first embodiment will be described.

  First, the CMY data generation unit 10 receives RGB data of each pixel data constituting color image data output from a scanner, a personal computer, or the like, and the CMY data generation unit 10 receives the above formula (3 ) To CMY data.

  The CMY data converted by the CMY data generation unit 10 is input to the red component determination unit 12, and the red component determination unit 12 uses the red component definition surface set in the red component definition surface setting unit 14. Used to determine whether the CMY data has a red component. That is, the red component determination unit 12 determines whether the CMY data exists in the upper left half (the portion where the red component exists) of the red component definition surface shown in FIG. 2 or the lower right half (the red component of the red component definition surface). Is present in a portion that does not exist.

  Specifically, the plane equation (4) is an area defined as having no red component, and since it can be said that the upper left portion has a red component and the lower right portion has no red component, rC + sM + tY has CMY. When data is input and rC + sM + tY> 0, the CMY data is determined to exist in the upper left half of the red component definition surface shown in FIG. 2 and is determined to have a red component. On the other hand, when rC + sM + tY ≦ 0, the CMY data is determined to be present on the red component definition surface or the lower right half of the red component definition surface shown in FIG. 2, and is determined not to have a red component. To do.

  Then, the determination result determined by the red component determination unit 14 is output to the red component data acquisition unit 16, and the red component data acquisition unit 16 acquires red component data based on the input determination result. Specifically, when the input determination result is a determination result indicating that the red component is not included, the red component data DR (C, M, Y) of the CMY data is set to 0. When the input determination result is a determination result that the red component is included, the distance d (C, M, Y) between the CMY data and the red component definition surface is calculated. Then, the red component data DR (C, M, Y) is calculated by normalization as shown in the following equation (7).

DR (C, M, Y) = d (C, M, Y) / d (0, 1, 1) (7)
D (0, 1, 1) is a distance from red (R = 1, G = 0, B = 0 (that is, C = 0, M = 1, Y = 1)) to the red component definition surface. , The maximum distance.

D (C, M, Y) is calculated according to the above equation (6). With this definition, DR (C, M, Y) is the amount of red component that can take a value between 0 and 1.

  The DR (C, M, Y) acquired by the red component data acquisition unit 16 as described above is input to the red component data density acquisition unit 18, and the density is Calculated. Specifically, for example, when DR (C, M, Y) = 0.7, the red component is the addition of the M component and the Y component, so C = 0, M = 0.7, Y = 0 .7 is input to the following equation (8) to calculate the density Dsty (DR (C, M, Y)) of the red component data.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (8)
When DR (C, M, Y) = 0, the density Dsty (DR (C, M, Y)) of the red component data is also zero.

  On the other hand, the CMY data converted by the CMY data generation unit 10 is input to the CMY data density acquisition unit 20, and the CMY data density acquisition unit 20 calculates the density of the CMY data. Specifically, the CMY data is input to the following equation (9), and the density Dsty (C, M, Y) of the CMY data is calculated.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (9)
Then, the red component data density Dsty (DR (C, M, Y)) acquired by the red component data density acquisition unit 18 and the CMY data density Dsty (C, M) acquired by the CMY data density acquisition unit 20. , Y) is input to the difference data acquisition unit 22, and the difference data acquisition unit 22 acquires the difference data ΔDsty (C, M, Y) according to the following equation (10).

ΔDsty (C, M, Y) = Dsty (C, M, Y)
-Dsty (DR (C, M, Y)) (10)
Then, the difference data ΔDsty (C, M, Y) acquired in the difference data acquisition unit 22 is input to the black component data acquisition unit 24, and the black component data acquisition unit 24 performs the black component data according to the following equation (11). Data DBlk (C, M, Y) is acquired.

Dsty (DBlk (C, M, Y)) = ΔDsty (C, M, Y) (11)
Note that ΔDsty (C, M, Y) = DBlk (C, M, Y). The reason is as follows.

  Gray scales including black have the same values for C, M, and Y. When described in three colors of C, M, and Y, they are (k, k, k). The density Dsty (k, k, k) of the color (k, k, k) can be obtained by the following equation.

Dsty (k, k, k) = 0.299k + 0.587k + 0.114k = k
That is, Dsty (k, k, k) = k.

Since the density difference represented by the difference data ΔDsty (C, M, Y) is the black component,
Dsty (k, k, k) = ΔDsty (C, M, Y).

Therefore, k = ΔDsty (C, M, Y)
Therefore,
Black component data DBlk (C, M, Y) = Dsty (k, k, k) = k = ΔDsty (C, M, Y).

  Then, DR (C, M, Y) acquired in the red component data acquisition unit 16 and DBlk (C, M, Y) acquired in the black component data acquisition unit 24 are input to the separation data acquisition unit 26, The color separation data obtaining unit 26 obtains red component separation data and black component separation data, respectively.

  According to the two-color separation apparatus of the first embodiment, difference data between the density of CMY data and the density of red component data is acquired, and black component data is acquired based on the difference data. The color document density can be distributed between the red component separation data and the black component separation data, and the brightness and density of the color document are comparable to the brightness and density of the printed matter printed in two-color printing. Separation data can be automatically acquired.

  In the first embodiment, the red component definition surface includes a gray scale (that is, r + s + t = 0). However, the red component definition surface does not necessarily include the gray scale. For example, the red component definition plane shown in FIG. 2 may be translated. That is, the red component definition surface may be set by the following equation.

rC + sM + tY = n, where n is a constant For example, when the red component definition plane is translated to the lower right, the gray scale from white to black is not included, and conversely, the grace scale is the upper left of the red component definition plane. Therefore, the gray scale also has red component data. When the red component definition surface is set as described above, the gray scale is printed with two colors instead of one black as a printing result.

  Alternatively, a plurality of values of n may be set in advance so that the user can select a value of n according to his / her preference.

  Next, a second embodiment of the two-color plate separation apparatus of the present invention will be described. FIG. 3 is a block diagram illustrating a schematic configuration of the two-color plate separation apparatus according to the second embodiment.

  The two-color plate separation apparatus of the second embodiment is substantially the same as the two-color plate separation apparatus of the first embodiment, but the method of distributing the difference data acquired by the difference data acquisition unit 22 is different. In the two-color separation apparatus of the first embodiment, the difference data Dsty (C, M, Y) is distributed only to the black component separation data, but the two-color separation of the second embodiment. The apparatus distributes the difference data Dsty (C, M, Y) to both the red component separation data and the black component separation data.

  Specifically, the difference data Dsty (C, M, Y) acquired by the difference data acquisition unit 22 is output to the black component data acquisition unit 28 and the color separation data acquisition unit 30. Then, the black component data acquisition unit 28 acquires black component data DBlk (C, M, Y) according to the following equation (12).

Dsty (DBlk (C, M, Y)) = ΔDsty (C, M, Y) × α (12)
Α is a preset value and 0 ≦ α ≦ 1. The method for calculating DBllk (C, M, Y) is the same as described above.

  On the other hand, the separation data acquisition unit 30 calculates supplementary data ΔDR (C, M, Y) according to the following equation (13), and the supplementary data ΔDR (C, M, Y) and the red component data acquisition unit 16. The red component data DR (C, M, Y) acquired in step S is added to obtain red component separation data.

ΔDR (C, M, Y) = ΔDsty (C, M, Y)
× (1-α) / (0.587 + 0.114) (13)
The above equation (13) is an equation obtained as follows.

The supplemental data ΔDR (C, M, Y) is (0, ΔDR, ΔDR) when expressed in CMY. The concentration is ΔDR × (0.587 + 0.114) from the following concentration calculation formula.

Concentration = 0.299 x C + 0.587 x M + 0.114 x Y
Since the density corrected with the red component is ΔDsty (C, M, Y) × (1−α),
ΔDR (C, M, Y) × (0.587 + 0.114)
= ΔDsty (C, M, Y) × (1−α).

Therefore, ΔDR (C, M, Y) = ΔDsty (C, M, Y)
X (1-α) / (0.587 + 0.114).

  Further, DBlk (C, M, Y) acquired in the black component data acquisition unit 28 is input to the separation data acquisition unit 30, and the separation data acquisition unit 30 acquires it as separation data of the black component.

  According to the two color separation apparatus of the second embodiment, the difference data between the density of the CMY data and the density of the red component data is acquired, and the difference data is distributed to the red component data and the black component data. Therefore, the density of the color original can be distributed between the red component separation data and the black component separation data, and the brightness and density of the color document and the brightness and density of the printed matter printed by two-color printing can be obtained. It is possible to automatically obtain separation data that has the same level.

  In the two-color plate separation apparatus of the second embodiment, the value of α may be changed depending on whether the document is a photographic image or a character image.

  Then, by adjusting the value of α, it is possible to obtain a printing result in which the red component is adjusted to a desired degree.

  Next, a third embodiment of the two-color plate separation apparatus of the present invention will be described in detail. FIG. 4 is a block diagram illustrating a schematic configuration of the two-color plate separation apparatus according to the third embodiment. The two-color plate separation apparatus of the third embodiment acquires color separation data for each color component used when performing two-color printing of red and green.

  The two-color plate separation apparatus of the third embodiment has the same configuration as the two-color plate separation apparatus of the first embodiment. As shown in FIG. A green component determination unit 34, a green component data acquisition unit 36, and a green component data density acquisition unit 38.

  The green component definition plane setting unit 32 is set with a green component definition plane for defining a green component in a color cube having three axes of C component, M component, and Y component as shown in FIG. Is. The green component definition surface is used to determine whether or not the CMY data includes a green component. In FIG. 5, the red component definition plane and the green component definition plane are shown on the same drawing, but are set in the red component definition plane setting unit 12 and the green component definition plane setting unit 32, respectively. ing.

  Here, the red component definition surface and the green component definition surface can be expressed by the following equations (14) and (15).

Red component definition surface r ₁ C + s ₁ M + t ₁ C = 0 (14)
r ₁ , s ₁ , t ₁ are coefficients Note that the method of determining the coefficients of r ₁ , s ₁ , t _{1 on} the red component definition surface is the same as in the first embodiment. For example, r ₁ = -7, s ₁ = 6, and t ₁ = 1.

Green component definition surface r ₂ C + s ₂ M + t ₂ Y = 0 (15)
r ₂ , s ₂ , and t ₂ are coefficients. The coefficients r ₂ , s ₂ , and t _{2 in} the above equation may be set so as to satisfy the following condition, for example.

1) The gray scale is on the green component definition surface.

2) The distance from green (R = 0, G = 1, B = 0) to the green component definition surface is the maximum.

3) The density is calculated in accordance with the ratio of the C, M, and Y coefficients in the following equation (16).

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (16)
First, from the condition of 1), r ₂ + s ₂ + t ₂ = 0.

  Next, the distance d from the predetermined point in the color cube to the green component definition surface is expressed by the following equation (17).

d = | r ₂ C + s ₂ M + t ₂ Y | / √ (r ₂ ² + s ₂ ² + t ₂ ² ) (17)
Since green is represented by (C, M, Y) = (1, 0, 1), in order to maximize the distance from green to the green component definition surface, (C, M, Y) = (1 , 0, 1), | r ₂ C + s ₂ M + t ₂ Y | may be maximized. That is, r ₂ and t ₂ may be set so as to have the same sign value.

Here, for example, when r ₂ <t ₂ is set, when the distance d is obtained, the distance d increases when the Y component is large, and the distance d decreases when the C component is large. Resulting in. Since it is desired to define that the green component increases as the C component increases, t ₂ <r ₂ is set so that the distance d increases when the C component is large.

Further, for example, r ₂ = 3, s ₂ = −4, and t ₂ = 1 may be set so as to satisfy the condition 3).

  The green component determination unit 34 uses the green component definition surface to determine whether or not the input CMY data has a green component.

  The green component data acquisition unit 36 acquires green component data based on the distance between the CMY data and the green component definition plane when the green component determination unit 34 determines that the CMY data has a green component. is there.

  The green component data density acquisition unit 38 acquires the density of the green component data acquired by the green component data acquisition unit 36.

  Next, the operation of the two-color plate separation apparatus of the third embodiment will be described.

  First, the CMY data generation unit 10 receives RGB data of each pixel data constituting color image data output from a scanner, a personal computer, or the like, and the CMY data generation unit 10 receives the above formula (3 ) To CMY data.

  The CMY data converted by the CMY data generation unit 10 is input to the red component determination unit 12, and the red component determination unit 12 uses the red component definition surface set in the red component definition surface setting unit 14. Used to determine whether the CMY data has a red component. That is, the red component determination unit 12 determines whether the CMY data exists in the upper left half of the red component definition surface shown in FIG. 2 or in the lower right half of the red component definition surface.

_{Specifically,} enter the CMY data into _{r 1 C + s 1 M +} t 1 Y, in the case of _{r 1 C + s 1 M +} t 1 Y> 0 , the CMY data is in the upper left half of the red component definitions for surface shown in FIG. 5 It is determined as existing, and determined as having a red component. On the other hand, in the case of r ₁ C + s ₁ M + t ₁ Y ≦ 0, it is determined that the CMY data exists on the red component definition surface or the lower right half of the red component definition surface shown in FIG. It is determined that it does not have.

  Then, the determination result determined by the red component determination unit 14 is output to the red component data acquisition unit 16, and the red component data acquisition unit 16 acquires red component data based on the input determination result. Specifically, when the input determination result is a determination result indicating that the red component is not included, the red component data DR (C, M, Y) of the CMY data is set to 0. When the input determination result is a determination result that the red component is included, the distance d (C, M, Y) between the CMY data and the red component definition surface is calculated. Then, the red component data DR (C, M, Y) is calculated by normalization as shown in the following equation (18).

RD (C, M, Y) = d (C, M, Y) / d (0,1,1) (18)
Note that d (0, 1, 1) is the distance from red to the red component definition surface, and is the maximum distance.

D (C, M, Y) is calculated according to the above equation (6).

  The DR (C, M, Y) acquired by the red component data acquisition unit 16 as described above is input to the red component data density acquisition unit 18, and the density is Calculated. Specifically, for example, when DR (C, M, Y) = 0.7, the red component is the addition of the M component and the Y component, so C = 0, M = 0.7, Y = 0 .7 is input to the following equation (19), and the density Dsty (DR (C, M, Y)) of the red component data is calculated.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (19)
When DR (C, M, Y) = 0, the density Dsty (DR (C, M, Y)) of the red component data is also zero.

  On the other hand, the CMY data converted in the CMY data generation unit 10 is input to the green component determination unit 34, and the green component determination unit 34 uses the green component definition surface set in the green component definition surface setting unit 32. To determine whether the CMY data has a green component. That is, the green component determination unit 32 determines whether the CMY data exists in the upper left half of the green component definition surface shown in FIG. 5 or the lower right half of the green component definition surface.

Specifically, CMY data is input to r ₂ C + s ₂ M + t ₂ Y, and r ₂ C + s ₂ M + t
_{2 When} Y> 0, the CMY data is determined to be present in the lower right half of the green component definition surface shown in FIG. 5 and is determined to have a green component. On the other hand, when r ₂ C + s ₂ M + t ₂ Y ≦ 0, the CMY data is determined to be present on the green component definition surface or the upper left half of the green component definition surface shown in FIG. Judge as not having.

  And the determination result determined in the green component determination part 34 is output to the green component data acquisition part 36, and the green component data acquisition part 36 acquires green component data based on the input determination result. Specifically, when the input determination result is a determination result that the green component is not included, the green component data DR (C, M, Y) of the CMY data is set to 0. When the input determination result is a determination result that the green component is present, the distance d (C, M, Y) between the CMY data and the green component definition surface is calculated. Then, normalization is performed as shown in the following equation (20) to calculate green component data DG (C, M, Y).

DG (C, M, Y) = d (C, M, Y) / d (1, 0, 1) (20)
Note that d (1, 0, 1) is the distance from green to the green component definition surface, which is the maximum distance.

D (C, M, Y) is calculated according to the above equation (17).

  Then, the DG (C, M, Y) acquired in the green component data acquisition unit 36 as described above is input to the green component data density acquisition unit 38, and the density is determined in the green component data density acquisition unit 38. Calculated. Specifically, for example, when DG (C, M, Y) = 0.7, the green component is the addition of the C component and the Y component, so C = 0.7, M = 0, Y = 0 .7 is input to the following equation (21) to calculate the density Dsty (DR (C, M, Y) of the green component data.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (21)
When DG (C, M, Y) = 0, the density Dsty (DG (C, M, Y)) of the green component data is also zero.

  On the other hand, the CMY data converted by the CMY data generation unit 10 is input to the CMY data density acquisition unit 20, and the CMY data density acquisition unit 20 calculates the density of the CMY data. Specifically, the CMY data is input to the following equation (22), and the density Dsty (C, M, Y) of the CMY data is calculated.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (22)
Then, the red component data density Dsty (DR (C, M, Y)) acquired by the red component data density acquisition unit 18 and the green component data density Dsty (DG) acquired by the green component data density acquisition unit 38. (C, M, Y)) and the density Dsty (C, M, Y) of the CMY data acquired by the CMY data density acquisition unit 20 are input to the difference data acquisition unit 40. Difference data ΔDsty (C, M, Y) is acquired according to equation (23).

ΔDsty (C, M, Y) = Dsty (C, M, Y)
-Dsty (DR (C, M, Y))
-Dsty (DG (C, M, Y)) (23)
Then, the difference data ΔDsty (C, M, Y) acquired by the difference data acquisition unit 22 is input to the supplemental data acquisition unit 42, and the supplementary data acquisition unit 42 acquires the supplementary data of the red component according to the following equation (24). ΔDR (C, M, Y) and supplemental data ΔDG (C, M, Y) of the green component are calculated.

ΔDsty (C, M, Y) = Dsty (ΔDR (C, M, Y))
+ Dsty (ΔDG (C, M, Y)) (24)
Specifically, ΔDR (C, M, Y) and ΔDG (C, M, Y) are calculated as follows according to the coefficient of the following equation (25) for obtaining the concentration.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (25)
ΔDR (C, M, Y) = ΔDsty (C, M, Y) × α / (0.587 + 0.114)
ΔDG (C, M, Y) = ΔDsty (C, M, Y)
× (1-α) / (0.299 + 0.114)
Α is a preset value, and 0 ≦ α ≦ 1. A printing result with a strong red color can be obtained by increasing α, and a printing result with a strong green color can be obtained by reducing α. By adjusting α as described above, a print result desired by the user can be obtained.

  Then, the red component supplement data ΔDR (C, M, Y) and the green component supplement data ΔDG (C, M, Y) acquired by the supplement data acquisition unit 42 are input to the color separation data acquisition unit 44. In addition, the red component data DR (C, M, Y) acquired by the red component data acquisition unit 16 and the green component data DG (C, M, Y) acquired by the green component data acquisition unit 36 are separated data. Input to the acquisition unit 44.

  Then, the color separation data acquisition unit 44 acquires red component separation data and green component separation data according to the following equations (26) and (27).

Red component separation data: DR (C, M, Y) + ΔDR (C, M, Y) (26)
Separation data of green component: DG (C, M, Y) + ΔDG (C, M, Y) (27)
According to the two-color separation apparatus of the third embodiment, difference data between the density of CMY data and the density of red component data and green component data is acquired, and the difference data is converted into red component data and green component data. Therefore, it is possible to distribute the density of the color document between the red component separation data and the green component separation data, and the brightness and density of the color document and the printed matter printed by two-color printing. It is possible to automatically obtain color separation data with the same brightness and density.

  In the two-color plate separation apparatus of the third embodiment, the supplementary data for both the red component and the green component is calculated. However, only the supplementary data for one of the color components is calculated according to preference. It may be calculated and added to any one of the color component data.

  In the third embodiment, the red component definition surface and the green component definition surface include the gray scale. However, the gray component may not necessarily include the gray scale. For example, the red component definition plane and / or the green component definition plane shown in FIG. 5 may be translated. That is, the red component definition surface and the green component definition surface may be set by the following equations.

Red component definition surface r ₁ C + s ₁ M + t ₁ Y = n ₁ , n ₁ is a constant green component definition surface r ₂ C + s ₂ M + t ₂ Y = n ₂ , n ₂ is a constant Also, the values of n ₁ and n ₂ above May be set in advance so that the user can select the value of n according to his / her preference.

  Next, a fourth embodiment of the two-color plate separation apparatus of the present invention will be described in detail. FIG. 6 is a block diagram showing a schematic configuration of the two-color plate separation apparatus of the fourth embodiment. The two-color plate separation apparatus of the fourth embodiment acquires the color separation data of each color component used when performing two-color printing of red and blue.

  The two-color plate separation apparatus of the fourth embodiment has a partly the same configuration as the two-color plate separation apparatus of the first embodiment, and further, as shown in FIG. A blue component determination unit 48, a blue component data acquisition unit 50, and a blue component data density acquisition unit 52.

  The blue component definition plane setting unit 46 is set with a blue component definition plane for defining a blue component in a color cube having three axes of C component, M component, and Y component as shown in FIG. Is. The blue component definition surface is used to determine whether or not the CMY data includes a blue component. In FIG. 7, the red component definition plane and the blue component definition plane are shown on the same drawing, but are set in the red component definition plane setting unit 12 and the blue component definition plane setting unit 46, respectively. ing.

  Here, the red component definition surface and the blue component definition surface can be expressed by the following equations (28) and (29).

Red component definition surface r ₁ C + s ₁ M + t ₁ C = 0 (28)
r ₁ , s ₁ , t ₁ are coefficients Note that the method of determining the coefficients of r ₁ , s ₁ , t _{1 on} the red component definition surface is the same as in the first embodiment. For example, r ₁ = -7, s ₁ = 6, and t ₁ = 1.

Blue component definition surface r ₃ C + s ₃ M + t ₃ Y = 0 (29)
r ₃ , s ₃ , and t ₃ are coefficients. The coefficients r ₃ , s ₃ , and t _{3 in} the above equation may be set so as to satisfy the following conditions, for example.

1) The gray scale is on the blue component definition surface.

2) The distance from blue (R = 0, G = 0, B = 1) to the blue component definition surface is the maximum.

3) The density is calculated in accordance with the ratio of the C, M, and Y coefficients in the following equation (30).

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (30)
First, from the condition of 1), r ₃ + s ₃ + t ₃ = 0.

  Next, a distance d from a predetermined point in the color cube to the blue component definition surface is expressed by the following equation (31).

d = | r ₃ C + s ₃ M + t ₃ Y | / √ (r ₃ ² + s ₃ ² + t ₃ ² ) (31)
Since blue is represented by (C, M, Y) = (1, 1, 0), in order to maximize the distance from blue to the blue component definition surface, (C, M, Y) = (1 , 1, 0), | r ₃ C + s ₃ M + t ₃ Y | may be maximized. That is, r ₃ and s ₃ may be set so as to have the same sign value.

Here, for example, when s ₃ <r ₃ is set, when the distance d is obtained, the distance d may increase when the C component is large, and the distance d may decrease when the M component is large. Resulting in. Since it is desired to define that the blue component increases as the M component increases, r ₃ <s ₃ is set so that the distance d increases when the M component is large.

Further, for example, r ₃ = 3, s ₃ = 6, and t ₃ = −9 may be set so as to satisfy the condition 3).

In this embodiment, r ₃ , s ₃ , and t ₃ are determined as described above. However, the ratio of the C, M, and Y coefficients in the above equation (30) for calculating the concentration is not necessarily limited. For example, r ₃ , s ₃ , and t ₃ may be set in accordance with a sense seen by humans. In this case, for example, r ₃ > s ₃ may be set. _{r 3 = 6, s 3 =} 3, may also be set to t 3 = -9.

  The blue component determination unit 48 uses the blue component definition surface to determine whether or not the input CMY data has a blue component.

  The blue component data acquisition unit 50 acquires blue component data based on the distance between the CMY data and the blue component definition surface when the blue component determination unit 48 determines that the CMY data has a blue component. is there.

  The blue component data density acquisition unit 52 acquires the density of the blue component data acquired by the blue component data acquisition unit 50.

  Next, the operation of the two-color plate separation apparatus of the fourth embodiment will be described.

  First, the CMY data generation unit 10 receives RGB data of each pixel data constituting color image data output from a scanner, a personal computer, or the like, and the CMY data generation unit 10 receives the above formula (3 ) To CMY data.

  The CMY data converted by the CMY data generation unit 10 is input to the red component determination unit 12, and the red component determination unit 12 uses the red component definition surface set in the red component definition surface setting unit 14. Used to determine whether the CMY data has a red component. That is, the red component determination unit 12 determines whether the CMY data exists in the upper left half of the red component definition surface shown in FIG. 2 or in the lower right half of the red component definition surface.

_{Specifically,} enter the CMY data into _{r 1 C + s 1 M +} t 1 Y, in the case of _{r 1 C + s 1 M +} t 1 Y> 0 , the CMY data is in the upper left half of the red component definitions for surface shown in FIG. 5 It is determined as existing, and determined as having a red component. On the other hand, in the case of r ₁ C + s ₁ M + t ₁ Y ≦ 0, it is determined that the CMY data exists on the red component definition surface or the lower right half of the red component definition surface shown in FIG. It is determined that it does not have.

  Then, the determination result determined by the red component determination unit 14 is output to the red component data acquisition unit 16, and the red component data acquisition unit 16 acquires red component data based on the input determination result. Specifically, when the input determination result is a determination result indicating that the red component is not included, the red component data DR (C, M, Y) of the CMY data is set to 0. When the input determination result is a determination result that the red component is included, the distance d (C, M, Y) between the CMY data and the red component definition surface is calculated. Then, the red component data DR (C, M, Y) is calculated by normalization as shown in the following equation (32).

RD (C, M, Y) = d (C, M, Y) / d (0,1,1) (32)
Note that d (0, 1, 1) is the distance from red to the red component definition surface, and is the maximum distance.

D (C, M, Y) is calculated according to the above equation (6).

  The DR (C, M, Y) acquired by the red component data acquisition unit 16 as described above is input to the red component data density acquisition unit 18, and the density is Calculated. Specifically, for example, when DR (C, M, Y) = 0.7, the red component is the addition of the M component and the Y component, so C = 0, M = 0.7, Y = 0 .7 is input to the following equation (33) to calculate the red component data density Dsty (DR (C, M, Y)).

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (33)
When DR (C, M, Y) = 0, the density Dsty (DR (C, M, Y)) of the red component data is also zero.

  On the other hand, the CMY data converted in the CMY data generation unit 10 is input to the blue component determination unit 48, and the blue component determination unit 48 uses the blue component definition surface set in the blue component definition surface setting unit 46. Used to determine whether the CMY data has a blue component. That is, the blue component determination unit 48 determines whether the CMY data exists in the upper left half of the blue component definition surface shown in FIG. 7 or the lower right half of the blue component definition surface.

_{Specifically,} enter the CMY data into _{r 3 C + s 3 M +} t 3 Y, in the case of _{r 3 C + s 3 M +} t 3 Y> 0 , the CMY data, front half of the blue component definitions for surface shown in FIG. 7 It is determined that it has a blue component. On the other hand, in the case of r ₃ C + s ₃ M + t ₃ Y ≦ 0, the CMY data is determined to exist on the blue component definition surface or the back half of the blue component definition surface shown in FIG. It is determined that it does not have.

  Then, the determination result determined by the blue component determination unit 48 is output to the blue component data acquisition unit 50, and the blue component data acquisition unit 50 acquires blue component data based on the input determination result. Specifically, if the input determination result is a determination result indicating that the component does not have a blue component, the blue component data DB (C, M, Y) of CMY data is set to zero. If the input determination result is a determination result that the component has a blue component, the distance d (C, M, Y) between the CMY data and the blue component definition surface is calculated. Then, the blue component data DB (C, M, Y) is calculated by normalization as shown in the following equation (34).

DB (C, M, Y) = d (C, M, Y) / d (1, 1, 0) (34)
Here, d (1,1,0) is the distance from blue to the blue component definition surface, and is the maximum distance.

D (C, M, Y) is calculated according to the above equation (31).

  The DB (C, M, Y) acquired in the blue component data acquisition unit 50 as described above is input to the blue component data density acquisition unit 52, and the density is determined in the blue component data density acquisition unit 52. Calculated. Specifically, for example, when DB (C, M, Y) = 0.7, the blue component is the addition of the C component and the M component, so C = 0.7, M = 0.7, Y = 0 is input to the following equation (35) to calculate the density Dsty (DB (C, M, Y) of the blue component data.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (35)
When DB (C, M, Y) = 0, the density Dsty (DB (C, M, Y)) of the blue component data is also zero.

  On the other hand, the CMY data converted by the CMY data generation unit 10 is input to the CMY data density acquisition unit 20, and the CMY data density acquisition unit 20 calculates the density of the CMY data. Specifically, the CMY data is input to the following equation (36), and the density Dsty (C, M, Y) of the CMY data is calculated.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (36)
Then, the red component data density Dsty (DR (C, M, Y)) acquired by the red component data density acquisition unit 18 and the blue component data density Dsty (DB) acquired by the blue component data density acquisition unit 52. (C, M, Y)) and the density Dsty (C, M, Y) of the CMY data acquired by the CMY data density acquisition unit 20 are input to the difference data acquisition unit 54. Difference data ΔDsty (C, M, Y) is acquired according to equation (37).

ΔDsty (C, M, Y) = Dsty (C, M, Y)
-Dsty (DR (C, M, Y))
-Dsty (DB (C, M, Y)) (37)
Then, the difference data ΔDsty (C, M, Y) acquired by the difference data acquiring unit 54 is input to the supplemental data acquiring unit 56, and the supplementary data acquiring unit 56 acquires the supplementary data of the red component according to the following equation (38). ΔDR (C, M, Y) and supplemental data ΔDB (C, M, Y) of the blue component are calculated.

ΔDsty (C, M, Y) = Dsty (ΔDR (C, M, Y))
+ Dsty (ΔDB (C, M, Y)) (38)
Specifically, ΔDR (C, M, Y) and ΔDB (C, M, Y) are calculated as follows according to the coefficient of the following equation (39) for obtaining the concentration.

Concentration = 0.299 × C + 0.587 × M + 0.114 × Y (39)
ΔDR (C, M, Y) = ΔDsty (C, M, Y) × α / (0.587 + 0.114)
ΔDB (C, M, Y) = ΔDsty (C, M, Y)
× (1-α) / (0.299 + 0.587)
Α is a preset value, and 0 ≦ α ≦ 1. A printing result with a strong red color can be obtained by increasing α, and a printing result with a strong blue color can be obtained by reducing α. By adjusting α as described above, a print result desired by the user can be obtained.

  Then, the red component supplement data ΔDR (C, M, Y) and the blue component supplement data ΔDB (C, M, Y) acquired by the supplement data acquisition unit 56 are input to the color separation data acquisition unit 58. In addition, the red component data DR (C, M, Y) acquired by the red component data acquisition unit 16 and the blue component data DB (C, M, Y) acquired by the blue component data acquisition unit 50 are separated data. Input to the acquisition unit 58.

  Then, the color separation data acquisition unit 58 acquires red component separation data and blue component separation data according to the following equations (40) and (41).

Red component separation data: DR (C, M, Y) + ΔDR (C, M, Y) (40)
Blue component separation data: DB (C, M, Y) + ΔDB (C, M, Y) (41)
According to the two-color separation apparatus of the fourth embodiment, difference data between the density of CMY data and the density of red component data and blue component data is acquired, and the difference data is converted into red component data and blue component data. Therefore, it is possible to distribute the density of the color document between the red component separation data and the blue component separation data, and the brightness and density of the color document and the printed matter to be printed by two-color printing. It is possible to automatically obtain color separation data with the same brightness and density.

  In the two-color plate separation apparatus of the fourth embodiment, the supplementary data for both the red component and the blue component is calculated. However, only the supplementary data for one of the color components is calculated according to preference. It may be calculated and added to any one of the color component data.

  In the fourth embodiment, the red component definition surface and the blue component definition surface include the gray scale. However, the gray component may not necessarily include the gray scale. For example, the red component definition surface and / or the blue component definition surface shown in FIG. 7 may be translated. That is, the red component definition surface and the blue component definition surface may be set by the following equations.

Red component definition surface r ₁ C + s ₁ M + t ₁ Y = n ₁ , n ₁ is a constant blue component definition surface r ₃ C + s ₃ M + t ₃ Y = n ₃ , n ₃ is a constant Also, the values of n ₁ and n ₃ above May be set in advance so that the user can select the value of n according to his / her preference.

  Further, in the calculation of the density in the description of the two-color plate separation apparatus of the first to fourth embodiments, the density and the brightness have a unique relationship as expressed by the following expression. Also good.

Lightness = 1-Density Further, the two-color plate separation apparatus of the first to fourth embodiments may be applied to obtain the color separation data of both a photographic image and a character image in a color document, You may apply only for acquisition of the separation data of a photographic image.

The block diagram which shows schematic structure of 1st Embodiment of the 2 color separation apparatus of this invention. The figure which shows the color cube which uses C component, M component and Y component as three axes, and the red component definition surface The block diagram which shows schematic structure of 2nd Embodiment of the 2 color separation apparatus of this invention. The block diagram which shows schematic structure of 3rd Embodiment of the 2 color separation apparatus of this invention. The figure which shows the color cube which uses C component, M component, and Y component as three axes, the red component definition surface, and the green component definition surface The block diagram which shows schematic structure of 4th Embodiment of the 2 color separation apparatus of this invention. The figure which shows the color cube which uses C component, M component, and Y component as three axes, the red component definition surface, and the blue component definition surface

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 CMY data generation part 12 Red component definition surface setting part 14 Red component determination part 16 Red component data acquisition part 18 Red component data density acquisition part 20 CMY data density acquisition part 22, 40, 54 Difference data acquisition part 24, 28 Black Component data acquisition unit 26, 30, 44, 58 Separation data acquisition unit 32 Green component definition surface setting unit 34 Green component determination unit 36 Green component data acquisition unit 38 Green component data concentration acquisition unit 42, 56 Supplementary data acquisition unit 46 Blue component definition surface setting unit 48 Blue component determination unit 50 Blue component data acquisition unit 52 Blue component data density acquisition unit

Claims (6)

In a two-color separation apparatus that acquires separation data of each color component of two-color separation based on CMY data of each pixel data constituting color image data representing a color document,
Color component definition surface for setting a color component definition surface for defining one of the two color separation components in a color cube having three axes of C component, M component, and Y component A setting section;
A first color component data acquisition unit that acquires the one color component data of the CMY data based on a distance between the CMY data and the color component definition surface;
A difference data acquisition unit that calculates the density of the CMY data, calculates the density of the one color component data, and acquires difference data between the density of the CMY data and the density of the one color component data;
A second color component data acquisition unit that acquires the other color component data among the color components of the two-color separation, based on the difference data acquired by the difference data acquisition unit;
One color component data acquired by the first color component data acquisition unit is acquired as color separation data of the one color component among the color components of the two-color color separation, and the second color component data 2. A color separation data acquisition unit that acquires the other color component data acquired by the acquisition unit as color separation data of the other color component among the color components of the two color separations Separation device. In a two-color separation apparatus that acquires separation data of each color component of two-color separation based on CMY data of each pixel data constituting color image data representing a color document,
Color component definition surface for setting a color component definition surface for defining one of the two color separation components in a color cube having three axes of C component, M component, and Y component A setting section;
A first color component data acquisition unit that acquires the one color component data of the CMY data based on a distance between the CMY data and the color component definition surface;
A difference data acquisition unit that calculates the density of the CMY data, calculates the density of the one color component data, and acquires difference data between the density of the CMY data and the density of the one color component data;
A second color component data acquisition unit that acquires a part of the difference data acquired by the difference data acquisition unit as the other color component data among the color components of the two-color separation;
An addition value of one color component data acquired by the first color component data acquisition unit and difference data other than a part of the difference data is used as the color component of the one color component of the two color separations. A color separation data acquisition unit that acquires the color separation data as the color separation data and acquires the other color component data as color separation data of the other color component among the color components of the two-color color separation; 2 color separation device. The one color component is a red component, and the other color component is a black component;
3. The two-color separation apparatus according to claim 1, wherein r <0, s> 0, and t> 0 when the color component definition surface is represented by the following expression.
rC + sM + tY = 0 In a two-color separation apparatus that acquires separation data of each color component of two-color separation based on CMY data of each pixel data constituting color image data representing a color document,
In a color cube having three components of C component, M component, and Y component, a first color component definition surface for defining a first color component and a second color component among the color components of the two color separations A color component definition surface setting unit for setting a second color component definition surface for defining a color component;
A first color component data acquisition unit that acquires the first color component data of the CMY data based on a distance between the CMY data and the first color component definition surface;
A second color component data acquisition unit that acquires the second color component data of the CMY data based on a distance between the CMY data and the second color component definition surface;
The density of the CMY data is calculated, the density of the first and second color component data is calculated, an added value of the first color component data and the second color component data, and the CMY data A difference data acquisition unit for acquiring difference data with the density of
A supplementary data acquisition unit that acquires supplemental data of at least one of the first color component and the second color component based on the difference data acquired by the difference data acquisition unit;
The supplement data acquired by the supplement data acquisition unit is added to at least one of the first color component data and the second color component data to acquire color separation data of the first and second color components. A two-color separation apparatus comprising a separation data acquisition unit. The first color component is a red component and the second color component is a green component;
In the case where the first color component definition surface is represented by the following formula (1), r ₁ <0, s ₁ > 0, t ₁ > 0,
3. The method according to claim 1, wherein r ₂ > 0, s ₂ <0, t ₂ > 0 when the second color component definition surface is represented by the following expression (2): Color separation device.
r ₁ C + s ₁ M + t ₁ Y = 0 (1)
r ₂ C + s ₂ M + t ₂ Y = 0 (2) The first color component is a red component and the second color component is a blue component;
In the case where the first color component definition surface is represented by the following formula (1), r ₁ <0, s ₁ > 0, t ₁ > 0,
3. The method according to claim 1, wherein r ₂ > 0, s ₂ > 0, and t ₂ <0 when the second color component definition surface is represented by the following expression (2): Color separation device.
r ₁ C + s ₁ M + t ₁ Y = 0 (1)
r ₂ C + s ₂ M + t ₂ Y = 0 (2)

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