JPH022015A - Color image processing apparatus - Google Patents

Abstract

PURPOSE:To perform proper color reproduction by mounting a correction means for applying predetermined correction for proper color reproduction to the color signal which is hard to be reproduced in proper color among a plurality of color signals corresponding to the detection result of a detection means. CONSTITUTION:When the correction only of the fluorescent colors belonging to both of an M-system and a YM-system is performed, the color signal outputted from a matrix converting circuit 3 is inputted to a fluorescent color detection circuit 4 and a correction quantity calculation circuit 5 but, in the fluorescent color detection circuit 4, a code figure is inputted to a decoder 9 and, when the signal AM1 from the decoder 9 is an H-level, an input color is regarded as the M-system and, when a signal AR1 is an H-level, said input color is regarded as the YM-system. When the code figure output signals of ROM tables 14, 15 are set to AR2, AM2, the input color is judged as the fluorescent color of the M-system when the AND AM3 of AM1 and AM2 is an H-level and judged as that of the YM-system when the AND AR3 of AR1 and AR2 is an H-level and said input color is outputted to the correction quantity calculation circuit 5 and a color signal is inputted to a ROM table 19 and these two color signals are set as an address to calculate the correction quantity of the Y-ink of the fluorescent light of the YM-system. As a result, a fluorescent color can be sharply reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention 1 (Field of Industrial Application) This invention is a method for converting color signals obtained by reading with a color sensor V in a color copying machine, for example, into an ink color signal in a color printer. The present invention relates to a color image processing device for performing correction and emphasis on specific areas to improve color reproducibility.

(Prior Art) Generally, in a color copying machine, a color image on a document is read by a line image sensor through primary color filters of R (red), G (border), and B (border), and Y (yellow) is read by a line image sensor. , M (magenta), C (cyan), and if necessary, rough K (black) ink to output as a hard copy using a color printer. In this way, the ink signal to be output is obtained from the input signal through color conversion processing.

However, if the color of the document is a highly pure chromatic color or a fluorescent color that has both high saturation and brightness, the combination of the above three or four color inks used in a normal printer It was often impossible to reproduce.

In particular, for fluorescent colors, when the amount of ink is determined using conventional masking methods, some of the above inks show large negative values.

Since it is not possible to print ink with negative density, there is a problem in that if this is simply made into a pillow, the output color of 1q will be very pale.

As a countermeasure to the negative ink gap caused by the masking method, there is a method described in Japanese Patent Application Laid-Open No. 62-276963, but this method involves removing the undercolor in the black additive color (
This is an improvement measure for tJcR) and is not effective in improving the color reproducibility of fluorescent colors.

Furthermore, there is a method described in Japanese Patent Laid-Open No. 7774/1983 as a color conversion method for reproducing colors that are out of the range that can be reproduced by the dark blue matching of ordinary Prohis ink. This method uses an input signal as an address and uses a lookup table (L
tJ T ). This method is effective when the output corresponding to the input signal value is slightly out of the range that can be reproduced by the above-mentioned combination of three or four color inks due to the introduction of noise. It is extremely difficult to create a look-up table that can handle cases where the input color is far outside the above-mentioned tH reproducible range, especially for fluorescent colors. Ta.

(The section that the invention attempts to solve! 1IJ) Conventional color image processing Jg! The device has a problem in that the saturation decreases when the original is a chromatic color with extremely high purity or a fluorescent color.

This invention was made based on the above circumstances, and it is possible to detect a highly saturated color or fluorescent color part and process that part differently from other parts, thereby improving the reproducibility of the detected part. It is an object of the present invention to provide a color image processing FJ device that can perform correction to improve the image quality and emphasize the detected portion.

E Structure 1 of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention converts a plurality of color signals into three or four color process ink drop signals for color reproduction or three or four color process ink signals for color reproduction. an ink base signal converting means for converting into either a process ink amount signal of a color or another ink signal; and an ink base signal converting means for converting the process ink amount signal of a color into either a color process ink amount signal or other ink signals; a detection means for detecting a color signal for which proper color reproduction is difficult; and a detection means for detecting a color signal for which proper color reproduction is difficult, and a predetermined color rN for current use, which is appropriate for each color signal for which proper color reproduction is difficult among the plurality of color signals, according to the detection result of the detection means. The gist of the present invention is to have a correction means for performing correction.

(Function) The detection means detects between three or four colors of process ink R (color signals for which it is difficult to reproduce properly even when using No. A) among the inks that are obtained using a normal masking method. It is determined based on the magnitude of the negative component of Next, the correction means detects the color signal that is difficult to reproduce properly by detecting the color that is closest to the input color within the reproduction area of the process ink for each color system to which the color belongs. Correction is performed, and the process ink drop signal converted from this color-corrected color signal may cause the copy output to be distorted if special colors such as fluorescent colors or highly saturated colors are manually input. Appropriate color reproduction is possible without the color becoming light or distorted.

(Example) Hereinafter, an example in which the present invention is applied to a color printer will be described based on the drawings. 1 to 5 are diagrams showing a first practical example.

First, the overall configuration of a color image processing apparatus will be described with reference to FIG. 1. In the figure, 1 is a scanner, and a color image from a document or the like is converted into a color signal S1 by this scanner 1. Here, i indicates the color of the color separation filter used in scanner 1, for example, 1=R (red),
G (green) and B (blue). The above color signal St is input to the first conversion circuit 2 and converted into an intermediate signal value Sa1. The relationship between Sl and Sal is expressed by the following equation.

S+1=(to(1(St(1-ρ)+ρ))/lo
(]ρ...(1) Here, ρ is a constant of 0, ρ, and 1, and a value of about 0.1 is an appropriate value for the weir in experiments.The above color signal is a matrix conversion It is input to the circuit 3 and converted into a color signal Dj. Here, j indicates the color of the process ink used in the printer, which will be described later. For example, j=Y (yellow), M (
magenta) and C (cyan). The relationship between S+1 and Dj at this time is expressed by the following equation.

DJ=M-8+1...(2)
Here, M is a 3×3 masking matrix, and if the matrix coefficient is Mjl, the color signal Dj in the above equation (2) is: Dj=MJR-8R1+MjG-8G10Mj[+・S
81...(3). That is, Dy=My R0Sr<1 +MYB DM=MMR-8R1 +MM[l DC=MCR-8rt1 +Mcs 1MY G ° S01 ・G81 +MMG ・SG1 ・G81 +1ylc G ・S01 ・G81 (3)- .

These color signals are input to a fluorescent color detection circuit 4 as a fluorescent color detection means, which identifies which of the eight chromatic color systems the input color belongs to and detects the fluorescent color. . Note that the details will be described later. Further, the above color signal is input to a correction amount calculation circuit 5 as a correction means. The correction amount calculation circuit 5 calculates the correction amount ΔDj based on the value of the color signal Dj and the result of the fluorescent color detection circuit 4. This correction amount ΔDj is input to an adder 6 to obtain a color signal @Dj1 of the correction amount. Therefore, D・1=D・+Δ
Dj...(4).

These color signals are transmitted to the second ink level signal converting means.
The signal is input to a conversion circuit 7 and converted into an ink signal T. The relationship between D・1 and Tj is as follows J
It is shown in the J formula.

il ■・=(1-ρ)/(1-ρ)...(5)
The ink side signal Tj obtained here is sent to the color printer 8.
It is designed to be supplied to

Next, details of fluorescent color detection and correction by the fluorescent color detection circuit 4 and the correction amount calculation circuit 5 will be explained using FIGS. 2 to 5.

Fluorescent ink has the property of absorbing light components with shorter wavelengths and emitting the energy as light with longer wavelengths. Due to this characteristic, fluorescent colors have both high saturation and brightness, and when trying to find the ink ■ using the normal masking method, it is found that among the three process inks of Y1M%C, there is a negative value. Era indicating the ink interval occurs. Forcibly opening the space between inks with negative values improves the reproducibility of brightness, but at the same time, the saturation information contained in the negative components is discarded.

As a result, the reproduced color uses less positive component ink to be printed than the color in which the color difference from the fluorescent color is minimal in the region reproducible with the process ink.

Therefore, in order to improve the color reproducibility of fluorescent colors, it is necessary to increase the number of positive component inks among the inks obtained by the normal masking method.

However, it is difficult to find a common function for all fluorescent colors to calculate an appropriate ink correction amount.

Therefore, the fluorescent colors are divided into several color systems, and the correction amount is calculated for each color system. First, the color signal D, which is the output of the matrix conversion circuit 3, is divided into eight types of systems depending on its sign as shown in the table of FIG. Among these, the system to which the fluorescent colors in circulation generally belong is (Y).
There are four types: magenta (M), red (YM), and green (YC). The color of this fluorescent original and the color of the copy obtained by the normal masking method are
- Australia a#i) 1 A comparison diagram on the chromaticity diagram is shown in Figure 3.

Among these systems, the Y system has almost no difference even on the B fist bIs plane. Furthermore, since the YC system has weak fluorescent color characteristics, the masking method has good output reproducibility, and a color with the minimum color difference within the reproducible region can be obtained, so there is no need for any particular correction.

On the other hand, the output reproducibility of the M system and YM system due to the masking method is poor, and the colors obtained are far from those with the minimum color difference within the reproducible area, so corrections should be made for each of these two systems. Let's do it. That is, in these two systems, if proper correction is performed, the reproducibility is improved even when recording with normal ink.

As a result of measuring the appropriate amount of correction for these two systems of fluorescent colors, it was found that the M ink requires a fixed amount of correction for both systems. In addition, Y in YM-based fluorescent colors
The ink correction amount is the color signal D that is the output of the masking method.
j is determined by a linear function based on the ratio of the color signal Dy to the sum of the color signals Dy and DM.

FIG. 4 shows in detail an example of the internal configuration of the fluorescent color detection circuit 4 and the correction amount calculation circuit 5, which perform correction of only the fluorescent colors belonging to these two systems.

The color signal Dj output from the matrix conversion circuit 3 is input to the fluorescent color detection circuit 4 and the correction amount calculation circuit 5, respectively. The fluorescent color detection circuit 4 includes a decoder 9 and three adders 1.
1.12.13.2 Read Only Memory (ROM)
14, 15, and two AND elements 16, 17.

Then, the code digit of the color signal output from the matrix circuit 3 is input to the (octal) decoder 9.

Here, the code digits of the three color signals are allocated to the inputs of the decoder 9 so that the code digit of [)C is the least significant bit and the code digit of DY is the least significant bit.

The signal whose output from the decoder 9 corresponds to 2 is AM+,
The signal corresponding to output 6 of decoder 9 is designated as AR+. When the signal AM+ from this decoder is at the H level, the input color is regarded as the M color, and when the signal AR+ is at the I'' level, the input color is regarded as the YM color. In this way, only colors belonging to two types of colors are separated.

The DY and DM phases ([)y+[)u) and DC are input to the ROM 14, respectively. The above ROM14 is ([)
Using Y 10M > and [)C as addresses, the value obtained by subtracting the function f from the threshold h1 is obtained from the ROM table 14. At this time, f+ = ABS ((DY + DM)/Dc)
...(6), where hl is a threshold value for YM fluorescent color discrimination, and is usually a value of about 0.3.

The ROM15 contains DY and [)c phases (DY + DC) and 2
Each DM is input. The above ROM15 is (DY
+DC> and 2DM as addresses, the level of the sign digit of the value obtained by subtracting the function r2 from the threshold F12 is set in ROM table 1.
Find from 5. At this point, r2=AI3S (20M/
(DY + Dc )) - < 7), and hl is a threshold value for determining the fluorescent color of the M system, and is usually a value of about 0.3.

Assuming that the code digit output signals of the ROM tables 14 and 15 are AR2 and AM2, respectively, if these signals are at H level, they are regarded as fluorescent colors. Therefore, if the logical product AM3 of the signals AMI and AM2 is at H level, it is an M-based fluorescent color, AR+ and Δl? Logical product A of 2 (3
If it is 1 level, it can be determined that it is a YM fluorescent color. In this way, fluorescent color detection is performed.

The above signal is output to the correction m0 output circuit 5.

The correction amount calculation circuit 5 has a ROM 19 with 18.3 OR elements.
．． 21, 22 and two switches 23, 24.

Then, the color signal output from matrix circuit 3 is RO
These two color signals are input to the M table 19, and using these two color signals as addresses, correction of the Y ink of the fluorescent color of the YM system, ΔDY of 01, is determined from the ROM table 19.

ΔDY = C2 (DY / (OY +DM) ) +03 ...<8)
Here, C2 and C3 each represent a correction constant.

In addition, correction constants C1 and C4 for fluorescent colors of the M system and YM system are recorded in the ROM 21, and the ROM 22
A correction amount of zero is recorded.

Among the signals output from the fluorescent color detection circuit 4.

Eight[? 3 is the Y ink correction switch 23 and R0M2
1 will be entered. Then, if this signal AIg3 is at the "L" level, that is, the input color is a fluorescent color of the YM system, the Y ink correction amount is changed to the ROM table 19...11 by the switch 23, and the Y ink correction interval is determined by equation (8). is set to the value determined by On the other hand, if the signal ARa is a torque signal, the switch 23 is turned to the ROM 22 side, and the Y ink correction amount ΔDY is released.

Further, the switch 24 is switched depending on the level of the logical sum of the signal AM3 and the signal Ana. If this logical sum is a trubel, that is, if the input color is a fluorescent color of the YM system or the M system, the correction interval ΔDM of the M ink is output from the ROM 22.

If the inter-correction ΔDM amount signal AR3 is Trubel, that is, if the input color is a YM fluorescent color, C4 is selected, and if it is Trubel, that is, if the input color is an M fluorescent color, C1 is selected. Each of the above correction amounts is input to an adder 6, respectively.

FIG. 5 is a table summarizing these correction intervals ΔD· for four types of fluorescent colors. In this way, the correction interval ΔD
Correction is performed by adding j to the color signal D.

Note that the correction constants 01 to C4 are set in advance so as to minimize the color difference between the original color and the copy.

Specifically, the optimum values of the above correction constants are C1=0.
21, C2=0.24, C3=0.16.0A=0.1
It was 5. By performing the correction in this manner, it becomes possible to reproduce bright fluorescent colors, which are often pale and have low saturation in conventional masking processing. In addition, in the above embodiment, three process inks, Y, M, and C, are used.
Although I have only explained colors, K
(Black) ink may be added to make the process ink four colors. However, in this case, the output DK of the first conversion circuit 2 corresponding to K is not related to the fluorescent color detection circuit 4.

Next, FIG. 6 shows a second embodiment of the present invention. In this embodiment, the configuration of the first embodiment is slightly changed so that fluorescent color portions can also be emphasized. That is, in the first embodiment described above, correction was performed by adding a correction amount that minimized the color difference between the color of the copy and the color of the original, but in this embodiment, for example, only the saturation is the same as the color of the original. It is also possible to adjust the ink level so that the ink level is close to that level.

In FIG. 6, 25 is a correction magnification selection switch installed on a control panel or the like, and the correction magnification selection switch 25 is used to set the correction magnification α. Here, hypothetically,
If the magnification α is 1, normal fluorescent color correction is performed. The magnification α set by the switch 25 is CP LJ 2
6 is input.

A ROM table 27 is also connected to the CPU 26.

7--The product of the ink star correction constants C+, C2, C3, and C4 described in the first embodiment and the correction magnification α is recorded in the bull 27. This ROM table 27 is configured so that the ROM table 27 can be switched by the number of times corresponding to the number set by the correction magnification selection switch 25 by the magnification α.

Normally, the magnification α of the correction magnification selection switch 25 is set to 1, and when the value of the correction magnification α is changed, the CPU 2
The contents of the ROM 27 taken in by 6-bl and 7I are changed.

The output from the correction ff1i output circuit 5, in which the correction magnification α has been changed, is input to the adder 6, and the output of the ink load is j! !
adjustments will be made. In this embodiment, rewritable memory (RAM) is used instead of ROM for tables 19 and 21 in the correction R calculation circuit 5, and the contents are rewritten each time the magnification α is changed. . If the value of the correction magnification α is increased, it is also possible to output a portion determined to be a fluorescent color as a solid image. In this way, this embodiment can also be used to perform partial emphasis. .

FIG. 7 does not show the third embodiment of the invention. In this embodiment, fluorescent color detection is carried out in exactly the same manner as in the first and second embodiments, but for correction, a part of the apparatus is changed to the configuration shown in FIG. So, I decided to do this. In the figure, the result of the fluorescent color detection circuit 4 is input to the fluorescent color ink addition m calculation circuit 28, and the same circuit 28 calculates the color signal Ds of the fluorescent color ink corresponding to the color signal Dj of the process ink. Here, S represents the color of one or more fluorescent inks, such as 5=fy (fluorescent yellow), fm (fluorescent magenta), and fC (fluorescent cyan).

The color signal Ds of the fluorescent color ink is input to the fluorescent color ink dedicated conversion circuit 29, and the fluorescent color ink ff1T
s is required. The above-mentioned fluorescent color ink is output to a two-phase color printer 30 equipped with a process ink dedicated printing section 31 and a fluorescent color ink dedicated printing section 32.

The two-phase color printer 30 can be manufactured by adding the above-mentioned fluorescent color ink on top of the process ink, or
Fluorescent color printing is performed using only fluorescent color ink. In the latter case, a negative ink correction value ΔDj is input from the fluorescent color ink ff1tf output circuit 28 to the second conversion circuit 7, and control is performed so that the process ink is not printed. By performing such correction, it is also possible to produce a copy output with better reproducibility than the method of reproducing fluorescent colors using only process ink.

The above embodiments mainly concern the color reproduction method for solid fluorescent colors, but the following embodiments may also be considered in consideration of the case where intermediate fluorescent colors are input. That is, the function f for fluorescent color determination and the correction amount ΔDj obtained in the above example
The value obtained by multiplying by is the final correction amount. By performing such processing, it is possible to avoid over-correcting even intermediate fluorescent colors.

[Effect of the invention 1] As explained above, according to the present invention, colors that cannot be reproduced with a combination of normal process inks used in printers can be reproduced in colors that are more faithful to the original than in conventional masking processing. It can be reproduced with. In other words, even if a highly saturated color or fluorescent color is input, the color will not fade, fade, or not appear, and will be reproduced in vivid color. Even when used in images, the marked areas can be reproduced without getting wet or cut off, eliminating uneven coating.

In addition, by detecting the fluorescent color part and adjusting the correction, replacing the professional ink with fluorescent color ink, or adding fluorescent color ink to the process ink,
It becomes possible to emphasize parts.

[Brief explanation of the drawing]

Figures 1 to 5 show color image processing according to this invention.
This shows the first embodiment of the device. Figure 1 is a Bucock diagram showing body composition, Figure 2 is a table showing the addition of ink and its reproduced colors, and Figure 3 is a table showing the color reproduction. The color of the fluorescent 137i stone and the color of the copy output by the conventional masking method are L0
Figure 4 is a circuit diagram showing the details of the internal configuration of the fluorescence 1fi detection circuit and the corrected early output circuit. Figure 5 is a comparison diagram on the a''b0 chromaticity diagram. Figure 5 is a diagram showing the details of the internal configuration of the fluorescent 1fi detection circuit and the corrected early output circuit. Figure 5 is the diagram for each ink for each fluorescent color system. 6 is a block diagram showing the second embodiment of the present invention, and FIG. 7 is a block diagram showing the third embodiment of the present invention. 4: Fluorescent color detection circuit (fluorescent color detection circuit) 5: correction φ calculation circuit (correction means), 7: second conversion circuit (ink level signal conversion means), 8: printer.

Claims (1)

[Scope of Claims] (1) A plurality of color signals can be either three or four color process ink amount signals for color reproduction, or the three or four color process ink amount signals and other ink amount signals. an ink amount signal converting means for converting the ink amount signal into an ink amount signal converting means; a detecting means for detecting a color signal for which it is difficult to properly reproduce a color by the process ink amount signal converted by the ink amount signal converting means among the plurality of color signals; A color image processing device comprising a correction means for applying a predetermined correction for proper color reproduction to each of the plurality of color signals for which proper color reproduction is difficult according to the detection result of the means. . (2) The detection means detects that it is difficult to properly reproduce colors using the process ink amount signal due to the value of the ink amount signal indicating a negative signal value among the ink amount signals obtained by color conversion by normal masking processing. 2. The color image processing device according to claim 1, wherein the color image processing device detects a color signal. (3) A printer that performs color reproduction processing based on an ink amount signal is one that adds fluorescent color ink over the process ink or replaces the process ink with fluorescent color ink only for the portion detected by the detection means. The color image processing device according to claim 1, characterized in that: