JPS62150252A - Device for deciding dot area ratio - Google Patents

Abstract

PURPOSE:To obtain the titled device which can sufficiently cope with a small-capacity memory, by previously preparing combination of the number of color masking systems corresponding to printing conditions or color separating conditions and carrying out color masking calculation by reading out the number of the color masking systems corresponding to various kinds of conditions in accordance with the color density of an original or color sample. CONSTITUTION:A color density measuring section 1 irradiates light upon an object to be measured and obtains color densities DR', DG', and DB' through a logarithmic amplifier after receiving the reflecting the light from and transmitting light through the object at each photoelectrical converter element through R-, G-, and B-filters for three-color separation and converting the light into electric signals. A gray component calculating circuit 2 finds the minimum value from color density values and judges whether or not an India ink plate is to be inserted or not and, when judged that the India ink plate is to be inserted, finds a gray component G which is to be replaced with the India ink plate. The gray component G is inputted to a dot converting circuit 3 and the color density value is converted into a dot area ratio and, as a result, the dot area ratio PBK of the India ink plate is found. Simultaneously, the area ratio PBK is inputted to a subtraction circuit 4 and the color densities DR', DG', and DB' used for masking calculation are found.

Description

[Detailed Description of the Invention] [Technical Field] This invention provides C (cyan), M (magenta), and Y [yellow] for printing based on color information obtained by optically measuring a document. , BK (black) color separations.

[Technical background of the invention and its problems]

Traditionally, the color of certain parts of printed matter? A small piece of paper called a color sample for specifying a color is sometimes attached to the printing layout sheet for the purpose of specifying the color in advance by the orderer.

For example, when it is desired to uniformly fill the background of a picture with a certain color, a small piece of paper having the background color is attached as a color sample and brought to a printing factory.

At the printing factory, the designated area is printed in the same color as the color sample using a 4-color printing method using 0% M, Y, and BK color separation plates, which is the most one-shot multi-color printing method. The above-mentioned C, M, Y, and Br (the dot area ratio of each color separation plate is determined at what percentage should be used for printing, and the color separation plates are produced under these conditions.

Conventionally, the above-mentioned work involves preparing a color chart, which is a collection of many printed matter printed by changing the dot area ratio of each color separation plate of C, M, Y, and BK in 10% intervals. Visually compare the sample and each color on the color chart and choose a color from the color chart that is even close to the color sample? Select each color necessary to print the selected color above, and use the fact that the color chart lists the dot area ratio of each color separation plate required to print each color in the color chart. The halftone area of the separated version is 4? : Knowing the dot area ratio, each color separation plate is created and printed to reproduce the color specified in the color sample.

However, this method requires manual work, and since there are a huge number of colors in the color chart, it takes time to compare the colors with color samples, and the colors selected from the color chart vary depending on the operator. The drawback is that the resulting colors tend to vary.

Will the applicant solve this drawback and use the colors specified in the color sample? For example, the patent application No. 57-20521 proposed a device that can accurately determine the dot area ratio of each color separation plate when reproducing by overprinting ink of each color Y%M%C, BK.
No. 7 (Japanese Unexamined Patent Publication No. 59-94759). This invention device (.)
The color density is determined by the light received by the light receiving element through the a<red), G (green), and B (blue violet) filters. Calculate this measured color density and the color/density of the pre-created color density/halftone surface density ratio table.
Compare and extract the Y, M, C, BK halftone dot area ratio corresponding to the color density in the table that matches or approximates the measured color density and outputs this to an output device such as a liquid crystal. By doing so, the color specified in the color sample can be reproduced by Y%M
, C, and BK can be determined.

However, in this type of dot surface 4-rate determination device, in order to accommodate differences in printing conditions such as printing paper, ink type, print density, print reproduction curve, etc., it is necessary to select as many colors as there are printing conditions. One halftone dot area ratio conversion table once? Must have.

For example, if you create a table in which the dot area ratio of three colors C11Vi and Y is changed in 20% increments from 0% to 100% for reflective originals, the number of colors is 6 = 21 < 5 colors, and each In order to memorize the density of R%G%B3 colors for each color, 216X! 1=648 data, and assuming that 1 data is 1 byte, a memory capacity of 648 bytes is required for one table. Furthermore, having as many tables as there are printing conditions requires a very large memory capacity.

In addition, many reflective or transparent originals are brought to printing companies as originals for printing, and these originals are usually scanned using scanners in four colors: C, Vl, Y%BK. It is converted into a halftone image as a decomposed version.

When performing color separation using a scanner, color separation conditions such as curve selection, highlight and shadow density of the document, and color balance status must be set.

Setting the color separation conditions is left to the operator who operates the scanner, but it takes time to set the color separation conditions, and it is difficult to make the scanner operate efficiently. Due to this, the cents of the color separation conditions vary and the quality also varies, which is a problem.

The dot area determination device measures a certain part of a document when setting color separation conditions to determine the dot area ratio of that part, and can use this as a reference for color separation conditions. I'm going to die.

In such use, it is necessary to write more tables corresponding to various color separation conditions than there are tables for printing conditions, and a large wax memory is required, making it difficult to miniaturize the device. Become.

[Purpose of the invention]

In order to solve the problems of the prior art as described above, this invention aims to determine the color of the barrel to be measured corresponding to printing conditions or color separation conditions. An object of the present invention is to provide an apparatus which can sufficiently cope with the determination of the dot area ratio of each color separation plate of C, M, Y, and BK necessary for reproduction in printing using a small memory.

[Summary of the invention]

The above purpose? The present invention has been made to achieve this by creating a combination of color masking coefficients in accordance with valley printing conditions or color separation conditions, and then based on the color quadrature optically measured on a manuscript or color sample. Color masking coefficients according to each of the four conditions for that one basic disaster? By reading and performing color masking calculations, it is possible to obtain the halftone dot area ratio of the color separation plate necessary for reproducing the colors of the original or color sample.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on the embodiments shown in the drawings.

Figure 5g1 is a block diagram of the apparatus of the present invention. The color density measuring section 1 irradiates the object to be measured with yt, and converts this reflected light or transmitted light into three color separations: R (red), G (green),
The signals are each received by a photoelectric conversion element through a B (blue violet) filter, and after receiving a drowsiness signal, they are passed through a logarithmic amplifier to obtain a color signal *DQbDB. Here, s DR% DG and DB are the color A degrees obtained through R%G and H filters, respectively. Gray component calculation circuit 2
calculates the minimum value of the color density values and determines whether or not to include a black plate. If a black plate is included,
A gray component G to be temporarily replaced with black is determined. This gray component is input to the halftone conversion circuit 6, where the color 6 degree value is converted to the same point surface 4, and the halftone area ratio P8 of the black plate is determined.The gray component is input to the subtraction circuit 4, and is masked using the following formula. DR', Do', and D8' used in the calculation are determined.

Next, this value is input to the masking calculation circuit 5, and masking calculation is performed using the color masking matrix indicated by the linear equation, and the dot area ratio P of C, M, and Y is calculated. %9, P
Y is required.

The problem here is the 5×3 matrix of aij, which is the masking coefficient. These masking coefficients are stored in the masking coefficient table memory 6 in association with each condition for the number of mark e11 conditions and color separation conditions, and are read out and transferred to the masking calculation circuit 5 by specifying the conditions. It has become.

Next, how to determine this masking coefficient will be explained for a reflective original. First, set the dot area ratio of C, M%Y5 colors to 0.
A color chart is created by printing at an appropriate stripe spacing between 100% and 100%, for example, 20%. This color chart will be composed of 6;216 colors.

The dot area ratio P0, PPY of C1M%Y of each color
and color density DR/.

The masking coefficient can be found by substituting D,/, 1) B/ into the cutting allowance. However, for each of the 216 colors, the masking factor d 6' - will not be the same.

Therefore, here we use the method of least squares to determine the masking factor aaijG? use For example, for cyan, P C'=a,, DR' + a12DG' + "
13D15' +31)-Tari, Wataru's breakthrough point surface P, and the error E of the total direct value P6' E = Po-Pa'
It is calculated by +41. The masking coefficient 811 is set so that this error is minimized for gold, that is, the sum of the squares of the errors shown in the following equation is the minimum. a1
Find 2'''15・EE=jyE・2(5) 1.11 Other coefficients can be found in the same way.

As mentioned above, if you have 216 colors of color A-dot surface and cinder conversion table, you will have 83 colors of R, G, and 83 colors for each color, so a total of 648 f-colors will be required. On the other hand, the masking coefficient according to the present invention? The way to have it is
It takes some time to determine the masking coefficient, but 9
It requires only data, reduces memory capacity, and reduces calculation time by 4 hours.

In this embodiment, primary masking is performed, but the same applies to cases where secondary masking is performed to improve accuracy.

Also, reflective +I4f! :Separate the colors using a scanner and output each version of C1M, Y, Bt Then, formulas 11) to 15) are obtained from the color density value of the color chart and the halftone dot area ratio of the color separation plate. Using masking factor? Ask for these and write them down in your memory.

The same goes for transparent originals: create a transparent color chart using a color plotter, etc., and set the transparency of R, G, and B at 4 degrees? Measure. Also, this? What are the decomposition conditions such as separation, curve, highlight and shadow density in the scanner? The colors are separated into four different colors, and the dot area ratio of each color is measured. Thereafter, masking coefficients can be obtained in the same manner as in the case of the reflective object, and these are stored in the memory B.

The halftone dot surface fif ratios of the M, Y versions and the BK halftone dot area ratio obtained by the masking calculation are output to an output device 7 such as a CRT, liquid crystal, or printer. .

〔Effect of the invention〕

According to the dot area ratio determination device of the present invention, it is possible to achieve a highly accurate dot area ratio that can accommodate many printing conditions or color separation conditions with a small memory capacity. can be determined, and the calculation time is short. In addition, when a color is specified with a reflective object such as a reflective original or a color sample, it is extremely easy for an experienced person to determine the halftone area ratio of each color to reproduce the specified color in a short time. can be found.

Also, the manuscript? When performing color separation, is it possible to change the color separation conditions to achieve the final result? Simulation jb can be performed and used as a reference for setting color separation conditions.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the half-point surface +# rate determination device of the present invention.

Claims (1)

[Claims] 1) In a device that calculates the dot area ratio of a color separation plate necessary to reproduce the colors of a transparent or reflective original or a color sample in print, multiple color masking coefficients corresponding to multiple printing conditions or color separation conditions are used. a color information measuring means for determining color information of a document or color sample for which a halftone dot area ratio is to be determined; and a color information measuring device for determining color information of a document or color sample for which a halftone dot area ratio is to be determined; A halftone dot area ratio determining device, comprising means for reading out the combination from the storage means, performing color masking calculation on the color information obtained by the color information measuring means, and calculating a halftone dot area ratio. .