JPH0530108B2 - - Google Patents
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- Publication number
- JPH0530108B2 JPH0530108B2 JP29174185A JP29174185A JPH0530108B2 JP H0530108 B2 JPH0530108 B2 JP H0530108B2 JP 29174185 A JP29174185 A JP 29174185A JP 29174185 A JP29174185 A JP 29174185A JP H0530108 B2 JPH0530108 B2 JP H0530108B2
- Authority
- JP
- Japan
- Prior art keywords
- black
- black component
- color
- value
- amount
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- 239000003086 colorant Substances 0.000 claims description 17
- 238000001514 detection method Methods 0.000 claims description 13
- 230000007423 decrease Effects 0.000 claims description 10
- 238000010586 diagram Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000004042 decolorization Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 1
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- Color Image Communication Systems (AREA)
- Color, Gradation (AREA)
- Facsimile Image Signal Circuits (AREA)
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は下色除去後のブラツク色の他色との重
なりやホワイト色の増大に起因して、有彩色の彩
度及び濃度が下色除去前に比べて低下するのを防
止した下色除去装置に関する。[Detailed Description of the Invention] [Industrial Application Field] The present invention is characterized in that the saturation and density of chromatic colors are lower than that of the undercolor due to the overlap of black color with other colors and increase in white color after undercolor removal. The present invention relates to an undercolor removing device that prevents the undercolor from being lowered compared to before removal.
従来より、カラー印刷、カラーハードコピーの
分野では、Y(イエロー)、M(マゼンタ)、C(シ
アン)の3色材にK(ブラツク)を加え、4色材
によつて色再現を行つている。かかる色再現法
は、Y、M、Cの3色材を減色混合によつて色再
現する場合、Y、M、Cが重なる部分は基本的に
黒を再現していると考えられることから、黒成分
をKの色材を用いて色再現を行なおうとするもの
であり、Kを用いた部分はY、M、C色材の量よ
りKに相当する量を減ずることによつて実現する
ことができる。
Traditionally, in the field of color printing and color hard copies, color reproduction has been performed using four color materials, by adding K (black) to the three color materials Y (yellow), M (magenta), and C (cyan). There is. This color reproduction method is based on the fact that when three color materials Y, M, and C are reproduced by subtractive color mixing, the portion where Y, M, and C overlap is basically reproducing black. This is an attempt to reproduce the black component using a K colorant, and the parts using K are achieved by subtracting the amount equivalent to K from the amount of Y, M, and C colorants. be able to.
例えば、第7図aに示すように、Y、M、Cの
各信号量の最小値を求め、その最小値の係数倍の
値をKの信号量とし、この信号量をY、M、C量
から減ずることによつて各補正データY′、M′、
C′を第7図bのように得ることができる。 For example, as shown in FIG. Each correction data Y′, M′, by subtracting from the amount
C' can be obtained as shown in Figure 7b.
ところで、第8図aの如き画像を前述の如き補
正手段を用いて下色除去(重ね刷り時における後
刷りインキの付き具合の悪くなるのを補正するた
め、3色が重なるシヤドウ部分の黒を墨インキに
置換し、墨色1色で表現する処理)することによ
つて、第8図bの画像を得ることができ、シヤド
ウ部分の黒が墨即に変換される。尚、図中、Y、
R、K、Wはイエロー、イエロー+マゼンタ、イ
エロー+マゼンタ+シアン、ホワイトを各々示
し、BKはブラツクを示す。 By the way, the image shown in Fig. 8a is removed by removing the undercolor using the above-mentioned correction means (in order to correct the poor adhesion of afterprint ink during overprinting, the black in the shadow part where three colors overlap is removed). The image shown in FIG. 8b can be obtained by replacing the black ink with black ink and expressing it with a single black color, and the black in the shadow portion is immediately converted to black. In addition, in the figure, Y,
R, K, and W represent yellow, yellow+magenta, yellow+magenta+cyan, and white, respectively, and BK represents black.
尚、この種の装置に関するものとして特開昭59
−161981号がある。 Furthermore, regarding this type of device, Japanese Patent Application Laid-Open No. 1983
-There is No. 161981.
しかし、従来の下色除去装置にあつては、第8
図bのようにブラツクの色材がY、R、Kの画点
と重なる場合及びホワイトが増大する場合には、
下色除去前の色に比べて有彩色の彩度の低下、及
び濃度が低下するため、画質が劣化する不具合が
ある。
However, in the conventional undercolor removal device, the eighth
As shown in Figure b, when the black color material overlaps with the Y, R, and K pixels, and when the white color increases,
There is a problem that the image quality deteriorates because the saturation of the chromatic color and the density of the chromatic color decrease compared to the color before removing the undercolor.
本発明は上記に鑑みてなされたものであり、下
色除去に伴う有彩色の彩度及び濃度の低下を防止
するため、無彩色に対しては無条件に下色除去処
理を適用し、有彩色に対しては彩度が高くなるに
従つて黒成分量が少なくなるように下色除去量を
作用させるようにした下色除去装置を提供するも
のである。
The present invention has been made in view of the above, and in order to prevent the decrease in saturation and density of chromatic colors due to removal of undercolor, undercolor removal processing is applied unconditionally to achromatic colors, and undercolor removal processing is applied unconditionally to achromatic colors. An object of the present invention is to provide an undercolor removal device in which an undercolor removal amount is applied to a color so that as the saturation increases, the amount of black component decreases.
本発明の下色除去装置によれば、Y、M、Cの
信号量の最小値と最大値に基づいて算出した黒成
分により、Y、M、Cの各信号より減ずる黒成分
量を算出して下色除去を実行させ、有彩色の彩度
の低下及び濃度の低下を防止する。
According to the undercolor removal device of the present invention, the amount of black component that is reduced from each signal of Y, M, and C is calculated using the black component calculated based on the minimum value and maximum value of the signal amount of Y, M, and C. Undercolor removal is performed to prevent a decrease in saturation and density of chromatic colors.
以下、本発明による下色除去装置を詳細に説明
する。
Hereinafter, the undercolor removing device according to the present invention will be explained in detail.
第1図は本発明の一実施例を示し、Y1、M1、
C1、の各色信号の最小値を検出する最小値検出
回路1と、Y1、M1、C1、の各色信号の最大値を
検出する最大値検出回路2と、該検出回路2及び
最小値検出回路1の検出出力に基づいて黒の信号
量K2を算出する黒成分算出回路3と、該回路3
の出力信号K2に基づいてY1、M1、C1の各々より
減ずる黒成分量K1を算出する補正値算出回路4
と、Y1、M1、C1の各信号から黒成分量K1を減算
し、Y2、M2、C2の各々を算出する減算回路5,
6及び7より構成される。 FIG. 1 shows an embodiment of the present invention, in which Y 1 , M 1 ,
A minimum value detection circuit 1 that detects the minimum value of each color signal of C 1 , a maximum value detection circuit 2 that detects the maximum value of each color signal of Y 1 , M 1 , C 1 , a black component calculation circuit 3 that calculates the black signal amount K 2 based on the detection output of the value detection circuit 1; and the circuit 3.
A correction value calculation circuit 4 that calculates a black component amount K 1 to be reduced from each of Y 1 , M 1 , and C 1 based on the output signal K 2 of
and a subtraction circuit 5 that subtracts the black component amount K 1 from each signal of Y 1 , M 1 , and C 1 to calculate each of Y 2 , M 2 , and C 2 ,
Consists of 6 and 7.
以上の構成において、B(ブルー)、G(グリー
ン)、R(レツド)の各色を変換処理して得られた
Y1、M1、C1の各信号の各々の最小値KMIN及び最
大値KMAXが最小値検出回路1及び最大値検出回
路2によつて検出される。ここで、
KMIN=MIN(Y1、M1、C1)であり、
KMAX=MAX(Y1、M1、C1)である。 In the above configuration, each color of B (blue), G (green), and R (red) is converted.
Minimum value K MIN and maximum value K MAX of each signal Y 1 , M 1 , and C 1 are detected by minimum value detection circuit 1 and maximum value detection circuit 2 . Here, K MIN = MIN (Y 1 , M 1 , C 1 ), and K MAX = MAX (Y 1 , M 1 , C 1 ).
KMIN及びKMAXは黒成分算出回路3に入力され、
該回路3によつて次式が演算される。 K MIN and K MAX are input to the black component calculation circuit 3,
The circuit 3 calculates the following equation.
K2=KMIN−fRI(KMAX−KMIN)
(但し、fRI(KMAX−KMIN)は有彩色の彩度の大き
さを加味する関数であり、RI1(KMAX−KMIN)は
例えば、r1(KMAX−KMIN)で表わされ、r1は係数
を示す)
黒成分算出回路3より出力される信号量K2は
補正値算出回路4に入力され、該回路4は、Y1、
M1、C1の各信号量から減算するための黒成分量
K1を算出する。この黒成分量K1は、例えば、K1
=r2×K2で表わされる信号量である(r2は係数)、
この黒成分量K1によつて減算回路5,6,7の
各々は、
Y2=Y1−K1、M2=M1−K1、C2=C1−K1の各
補正信号を出力する。 K 2 = K MIN − f RI (K MAX − K MIN ) (However, f RI (K MAX − K MIN ) is a function that takes into account the magnitude of the saturation of chromatic colors, and RI 1 (K MAX − K MIN ) is expressed as, for example, r 1 (K MAX - K MIN ), where r 1 indicates a coefficient) The signal amount K 2 output from the black component calculation circuit 3 is input to the correction value calculation circuit 4, and the corresponding Circuit 4 has Y 1 ,
Black component amount to be subtracted from each signal amount of M 1 and C 1
Calculate K 1 . This black component amount K 1 is, for example, K 1
= signal amount expressed as r 2 × K 2 (r 2 is a coefficient),
Based on this black component amount K1 , each of the subtraction circuits 5, 6, and 7 produces correction signals of Y2 = Y1 - K1 , M2 = M1 - K1 , and C2 = C1 - K1. Output.
ここで、第2図a〜dを参照して本発明の処理
を詳細に説明する。先ず、第2図aのように、
Y1、M1、C1の内の最大を示すものと最小を示す
もの(KMAX=Y1、KMIN=C1)を検出する。つい
で第2図bに示すように、(KMAX−KMIN)を求
め、(KMAX−KMIN)≠0によつて、無彩色では無
いものの、かと云つてさほど彩度の高い色ではな
いことを判定する。これは黒成分算出回路3の処
理に相当する。さらに第2図cに示すように、
K2の係数をr1=0.5として設定する。これは有彩
色であるために黒成分の量を無彩色の場合よりも
小さ目に設定しているものである。つぎに、第2
図dに示すように、補正値を算出するK1の係数
を、例えば、r2=0.5として、Y2、M2、C2を算出
する。 The process of the present invention will now be described in detail with reference to FIGS. 2a to 2d. First, as shown in Figure 2 a,
Among Y 1 , M 1 , and C 1 , the maximum value and the minimum value (K MAX =Y 1 , K MIN =C 1 ) are detected. Next, as shown in Figure 2b, (K MAX - K MIN ) is calculated, and since (K MAX - K MIN )≠0, it is not an achromatic color, but it is not a very saturated color. to judge. This corresponds to the processing of the black component calculation circuit 3. Furthermore, as shown in Figure 2c,
Set the coefficient of K 2 as r 1 =0.5. Since this is a chromatic color, the amount of black component is set smaller than in the case of an achromatic color. Next, the second
As shown in FIG. d, Y 2 , M 2 , and C 2 are calculated by setting the coefficient of K 1 for calculating the correction value to, for example, r 2 =0.5.
第3図a,bは本発明において下色除去を行つ
た場合の色画素図を示したものであり、第3図a
は第7図aに対応している。第3図bと第7図b
を比較して明らかなように、黒画点の数が変わら
ず(3点)、しかも黒画点と重ならないY、Rの
画点が別個に生じているため、有彩色の彩度の低
下を目立たなくすることができる。また、W(ホ
ワイト)部の画点も従来に比して少ないため、濃
度の低下を押えることができる。 Figures 3a and 3b show color pixel diagrams when undercolor removal is performed in the present invention, and Figure 3a
corresponds to FIG. 7a. Figure 3b and Figure 7b
As is clear from the comparison, the number of black dots remains the same (3 points), and Y and R dots that do not overlap with the black dots occur separately, resulting in a decrease in the saturation of chromatic colors. can be made less noticeable. Furthermore, since there are fewer pixels in the W (white) portion than in the past, it is possible to suppress a decrease in density.
第4図a,bは無彩色の信号に対して下色除去
を行う場合を示し、この場合、Y1=M1=C1とな
るため、KMAX=KMINとなり、K2=KMIN、K1=
1/3KMINとなる。しかし、第4図bに示すよう
に、K2がそのまま黒成分となつて出力されるた
め、第5図a,bに示すように画点数には変化が
無く、黒が再現される。 Figures 4a and b show the case where undercolor removal is performed on an achromatic signal. In this case, Y 1 = M 1 = C 1 , so K MAX = K MIN , and K 2 = K MIN , K 1 =
1/3K MIN . However, as shown in FIG. 4b, since K 2 is directly output as a black component, there is no change in the number of pixel points, and black is reproduced as shown in FIGS. 5a and 5b.
第6図a,bは彩度が高い信号に対する下色除
去を示し、彩度の高い色の場合には第6図aのよ
うに(KMAX−KMIN)が大きくなるために、K2=
KMIN−fR1(KMAX−KMIN)式における第2項のfR1
(KMAX−KMIN)が大きくなる。このため、K2すな
わち黒成分の量が少なくなり、Y2、M2、C2の信
号量は変化を受けなくなる。したがつて有彩色の
彩度が高くなるに従い黒成分量が少なくなり、第
6図のように高彩度の色に対しては、下色除去は
行われない。 Figures 6a and b show undercolor removal for signals with high saturation. In the case of highly saturated colors, (K MAX - K MIN ) increases as shown in Figure 6 a, so K 2 =
fR 1 of the second term in the K MIN − fR 1 (K MAX − K MIN ) formula
(K MAX − K MIN ) increases. Therefore, the amount of K 2 , that is, the black component, decreases, and the signal amounts of Y 2 , M 2 , and C 2 do not change. Therefore, as the saturation of a chromatic color increases, the amount of black component decreases, and undercolor removal is not performed for colors with high saturation as shown in FIG.
以上説明した通り、本発明の下色除去装置によ
れば、無彩色に対しては無条件に下色除去処理を
適用し、有彩色に対しては彩度が高くなるに従つ
て黒成分量が少なくなるように下色除去量を変え
るようにしたため、濃度及び彩度の低下を抑えた
下色除去が可能となる。さらに、係数およびスタ
ートポイントを可変することによつて、画像に応
じた調整を施すことができ、画質の向上を図るこ
とができる。
As explained above, according to the undercolor removal device of the present invention, the undercolor removal process is applied unconditionally to achromatic colors, and the amount of black component is applied to chromatic colors as the saturation increases. Since the amount of undercolor removal is changed so that the amount of undercolor is reduced, it is possible to remove undercolor while suppressing a decrease in density and saturation. Furthermore, by varying the coefficients and start points, adjustments can be made depending on the image, and image quality can be improved.
第1図は本発明の一実施例を示すブロツク図、
第2図a,b,c,dは本発明による下色除去処
理を示す説明図、第3図a,bは画素配列による
本発明の下色除去説明図、第4図a,bは本発明
における無彩色入力時の黒成分算出説明図、第5
図a,bは本発明における無彩色入力時の下色除
去説明図、第6図a,bは本発明における高彩度
色入力時の黒成分算出説明図、第7図a,bは従
来の下色除去処理における補正データ算出説明
図、第8図a,bは従来の下色除去説明図。
符号の説明、1……最小値検出回路、2……最
大値検出回路、3……黒成分算出回路、4……補
正値算出回路、5,6,7……減算回路。
FIG. 1 is a block diagram showing one embodiment of the present invention;
FIGS. 2a, b, c, and d are explanatory diagrams showing the undercolor removal process according to the present invention. FIGS. Explanatory diagram of black component calculation when inputting achromatic color in the invention, No. 5
Figures a and b are illustrations of undercolor removal when achromatic color is input in the present invention, Figures 6a and b are illustrations of black component calculation when high chroma color is input in the present invention, and Figures 7a and b are illustrations of conventional color removal. An explanatory diagram of correction data calculation in color removal processing, and FIGS. 8a and 8b are explanatory diagrams of conventional undercolor removal. Explanation of symbols: 1... Minimum value detection circuit, 2... Maximum value detection circuit, 3... Black component calculation circuit, 4... Correction value calculation circuit, 5, 6, 7... Subtraction circuit.
Claims (1)
4色を用いて色再現をする際、前記ブラツクを除
く各色より黒成分を減算して下色除去処理を施す
下色除去装置において、 前記イエロー、マゼンタ及びシアンの各信号中
の最小値を検出する最小値検出回路と、 前記イエロー、マゼンタ及びシアンの各信号中
の最大値を検出する最大値検出回路と、 前記最大値検出回路の出力と前記最小値検出回
路の出力との差に基づいて彩度を検出し、検出し
た彩度が高くなるに従つて黒成分量が少なくなる
ように調整量を決めるとともに、この調整量を前
記最小値検出回路の出力から減算して黒成分量を
算出する黒成分算出回路と、 該黒成分算出回路の出力信号に予め定めた係数
を乗じて前記イエロー、マゼンタ、及びシアンの
各々より減すべき黒成分量を算出する補正値算出
回路と、 該補正値算出回路の出力値を前記イエロー、マ
ゼンタ、シアンの各色信号から減算する減算部を
設けるとともに、前記調整値は前記最大値と最小
値との差値が0から大きくなるとともに0から最
小値までの値をとることを特徴とする下色除去装
置。[Scope of Claims] 1. An undercolor removal device that performs undercolor removal processing by subtracting a black component from each color other than black when reproducing colors using four colors: yellow, magenta, cyan, and black, a minimum value detection circuit for detecting the minimum value in each of the yellow, magenta and cyan signals; a maximum value detection circuit for detecting the maximum value in each of the yellow, magenta and cyan signals; and the maximum value detection circuit. Saturation is detected based on the difference between the output and the output of the minimum value detection circuit, and an adjustment amount is determined so that the black component amount decreases as the detected saturation increases, and this adjustment amount is a black component calculation circuit that calculates a black component amount by subtracting it from the output of the minimum value detection circuit; and a black component calculation circuit that multiplies the output signal of the black component calculation circuit by a predetermined coefficient and subtracts it from each of the yellow, magenta, and cyan. A correction value calculation circuit that calculates the expected black component amount, and a subtraction unit that subtracts the output value of the correction value calculation circuit from the yellow, magenta, and cyan color signals are provided, and the adjustment value is set to the maximum value and the minimum value. An undercolor removing device characterized in that the difference value from 0 increases from 0 and takes a value from 0 to a minimum value.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP29174185A JPS62150967A (en) | 1985-12-24 | 1985-12-24 | Under color eliminating device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP29174185A JPS62150967A (en) | 1985-12-24 | 1985-12-24 | Under color eliminating device |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS62150967A JPS62150967A (en) | 1987-07-04 |
JPH0530108B2 true JPH0530108B2 (en) | 1993-05-07 |
Family
ID=17772798
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP29174185A Granted JPS62150967A (en) | 1985-12-24 | 1985-12-24 | Under color eliminating device |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS62150967A (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2987393B2 (en) * | 1987-11-20 | 1999-12-06 | キヤノン株式会社 | Color image processing method |
JPH0270173A (en) * | 1988-09-02 | 1990-03-09 | Fuji Xerox Co Ltd | Digital picture processor |
JP2952489B2 (en) * | 1988-11-18 | 1999-09-27 | コニカ株式会社 | Image recording device |
-
1985
- 1985-12-24 JP JP29174185A patent/JPS62150967A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
JPS62150967A (en) | 1987-07-04 |
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