JPH08329240A - Color scanner - Google Patents

Abstract

PURPOSE: To integrate gray level and color tone to perform the color separation by using a specific gray level transformation formula to not only perform the gray level transformation of the light quantity value of each picture element for each color plate but also control and adjust the color tone. CONSTITUTION: A gray level transformation part 3 based on the gray level transformation formula which integrates the adjustment of the gray level and the color tone to perform the color separation is added to a detection part 1, a color separation part 2, and an output part 4. This gray level transformation formula is expressed by yn =yH+[α(1-10<-kx> )(yS-yH)/(α-β)] where (x) is the fundamental light quantity value obtained by subtracting a light quantity value xH, which corresponds to a density information value DH in the H part of a color document picture obtained by using the characteristic curve of a recording medium, from a light quantity value xn corresponding to a density information value Dn at an arbitrary picture element point (point (n)) of the color document picture obtained in the same manner and yn , yH, and yS are dot % values set on a color print picture respectively and (α) is the surface reflection factor of a picture expressing medium for recording of the color print picture and (k) is the numerical value determined by k=θ/(xS-xH) and γ is an arbitrary coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate-making scanner for producing a printing plate for producing a color printing image by subjecting image information obtained by photoelectrically scanning a continuous tone color original image to tone conversion. (Hereinafter referred to as a color scanner).

In particular, the present invention relates to a color scanner having a new function in a gradation converting section which is a core component of the color scanner. More specifically, the gradation conversion unit of the color scanner of the present invention does not use the conventional density information value as the image information of the color original image, but the characteristic curve (recording) of the recording medium on which the color original image is recorded. In order to eliminate the influence of the light quantity value incident on the medium and the characteristic curve defined by the density value formed on the recording medium, the light quantity value is used and a color original image is formed using a specific gradation conversion formula. The feature is that the function of adjusting the color tone is incorporated when the light intensity value is converted into gradation. The color scanner of the present invention is capable of quantitatively and rationally controlling not only gradation (also referred to as density gradation or gradation) but also color tone (color tone). A high-value-added color scanner that integrates the adjustment of is provided.

The present invention relates to a color scanner incorporating a new gradation conversion technique in which gradation and color tone controls are integrated as described above. However, the following description of the present invention streamlines the prior art color adjustment method,
In the sense of being quantified, the emphasis will be placed on the point that the gradation conversion unit of the color scanner is configured to have a new color tone management and adjustment function.

[0004]

2. Description of the Related Art As is well known, a print image, a copy image (copy image), a printer output image, a TV (video) image, and the like are printed from a color original image recorded on various recording media by various color reproduction techniques. Various color reproduction images have been produced. In the production of these color reproduction images, firstly, the density gradation (gradation) and color tone (color tone) of the color original image are Hi-Fi color (High-Fidelity, high fidelity color) on the color reproduction image. It is a very important subject to reproduce by the second, and secondly, to adjust to a tone having a desired tone (including both tone and color tone).

However, in the conventional technology, it is the current situation that the above-mentioned problems cannot be reasonably carried out with work regularity. This is a technique for faithfully reproducing the tone (gradation and color tone) of the color original image on the color reproduction image, and further for adjusting (correcting or changing) the tone of the color original image to a desired tone. , A non-linear conversion processing technique for converting image information of a color original image which is the basis thereof, particularly image information in a density region into half tone gradation (hereinafter referred to as image gradation conversion technology or image gradation conversion method). .)
This is because it does not support rational theory, and performs image gradation conversion irrationally and irrationally, relying largely on human experience and intuition.

The above-mentioned points will be described below in the field of the technology for producing a color print image, which is directly related to the present invention and in which high quality is always required. In the prior art, color film originals (about 90% of color film originals
% Is a transmission type and a transmission type. When producing a color print image which is a duplicate image from (1) to (4), the lightest part (H part) to the darkest part (S part) of the color film original is reached. The color separation curve (color separation work (color separation work) that determines the correlation between the continuous tone color film original image and the halftone dot color print image that is a duplicate image without the intention to reasonably understand the density characteristics It is said that the characteristic curve, halftone dot characteristic curve, etc.) ”is completely dependent on human experience and intuition.

Generally, in the production of a color print image, a color film original image (hereinafter, simply referred to as a color original image) is color-separated by a color scanner, and a multicolor plate making (generally C plate, M plate). Edition, Y
The four editions, the edition and the BL edition, are considered as one set. ) Is performed to reproduce a halftone dot color print image. As is well known, the C plate (cyan), the M plate (magenta), and the Y plate (yellow) are color-reduced corresponding to R (red), G (green), and B (blue) of the additive method. It has a complementary color relationship according to the law, and the BL plate is called black or black plate. The above-mentioned color scanner is a mechatronics-type extremely expensive device, but one of the major problems in the industry is that its operating rate is about 30 on average.
That is an extremely low level of%. The main reasons why expensive color scanners etc. have the low operation rate mentioned above are that the setup time (scanner setup time) for operating the color scanner is long, and the quality of the products obtained by the color separation work is unstable and insufficient. Therefore, there are many rescans (rescan, remake).

Considering this from a slightly technical point of view, as described above, as a tool for color separation work, although a color scanner or the like which is highly sophisticated and expensive at first glance is used, Multiple elemental technologies for disassembly work, such as color reproduction, color correction, and color correction (Color Reproduc
technology and density gradation (Gradat
It can be said that the ion () conversion technology is not systematically organized, which is the main reason for the low availability of color scanners.

As is well known, the masking equation (Ma
sking equation) and Neugebauer equation (Neugebauer
has been pursued scientifically by applying equations). However, the latter technique of converting the density gradation of the image (this is attributed to the problem of what size halftone dots should be set for all pixels in the color original image).
Has been left unchecked without rational theoretical support, and this part is largely dependent on human experience and intuition.

Since various devices for color separation have been developed under such a state, from the viewpoint of practicing color separation under the unified adjustment of color tone and gradation, the device itself In addition to being undeveloped in the basic design technology of, the operator's guessing work and the operator's experience and intuition are eliminated while using an expensive electronic color separation device (color scanner) that is expensive in actual work. Can't do (withou
t operator evalution, without operator's guess wor
k), it is not always possible to produce stable high-quality color print images.

In particular, when the color original image is not a standard original produced under appropriate photographing and exposure conditions and appropriate development conditions, for example, an overexposed overbright original, an underexposed overexposed original, a high key or low key Manuscript,
Furthermore, if the original is a non-standard original such as an original with color cast or a faded original,
Color separation work cannot be carried out reasonably and efficiently. That is, it is impossible to rationally perform color separation work on these non-standard color original images, and there are problems such as the low operation rate of the color scanner, the instability of the product quality, and the increase in the rescan rate. I have.

[0012]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present inventors not only faithfully reproduce the image quality of a color original image (the quality evaluated by both the gradation and the color tone), but further proceed to the above. In order to rationally produce a halftone gradation color reproduction image having a desired tone (gradation and color tone) from various color original images, prior to improvement of color reproduction and color correction (correction) technology. We have a basic recognition that the technology for converting the density gradation of each pixel of a color original image must be rationalized.

Based on the basic recognition by the present inventors, the present inventors previously proposed a method for rationally converting the gradation of a color original image based on a novel gradation conversion formula. And achieved certain results (for example, Japanese Patent Application No. 63-114599, U.
SP4, 924, 323; Japanese Patent Application No. 1-135825
No., USP 5,313,310; Japanese Patent Application No. 1-2121.
No. 18, USP 5,057,931; Japanese Patent Application No. 3-78.
668, USP 5,134,494, etc.).

Since the novel gradation conversion method previously proposed by the present inventor has a deep relationship with the present invention, the outline of the gradation conversion method will be described here, and its improvements will be described.
Needless to say, the above-mentioned improvements are essential technical constitutional requirements of the present invention.

In the prior art, color separation of a color original image is performed by literally separating an original image (subject, entity image, actual image).
A scene is the apple itself if the subject is an apple. ) To a "recording medium" called a photographic light-sensitive material (photographic light-sensitive emulsion) under a predetermined exposure condition (as is well known, the intensity I of the incident light and the incident time t are E, the exposure amount E is E = It.) Based on the density information of the color photographic image recorded (the color separation operation includes both reproduction of gradation and reproduction of color tone as described above). I am doing it. As is well known, photographic density (photographic d
ensity) is formed, and this becomes a medium image. The curve showing the correlation between the above-mentioned photographic density (blackening degree) and the exposure amount E of the photographic light-sensitive material is a photographic density characteristic curve. This is the photographic density (D) on the vertical axis (D = logIo /
I) and the horizontal axis is the logarithmic value (logE) of the exposure amount E and is displayed. For a film or a dry plate (transparent original), the ratio of the intensity I of transmitted light to the intensity Io of incident light is
It goes without saying that the ratio of the intensity I of reflected light to the intensity Io of completely reflected light is used for printing paper (reflection original).

The above-mentioned photographic density characteristic curve (hereinafter, simply referred to as "density characteristic curve") is typically a downwardly convex foot portion, a substantially straight linear portion (linear intermediate portion), and an upward convex shape. Is a complex curve with shoulders (see FIG. 1 below for this point). In the prior art, the color separation work is performed based on the density information value of each pixel of the color original image. In other words, the conventional color separation technology is constructed from the standpoint of the vertical axis (density value) of the density characteristic curve. The image information value (density information value) of the color original image (medium image), which is the basis of the color separation work in the related art, is not proportional to the image information value of the original image (entity image, subject, actual scene). It is greatly influenced by the light-sensitive characteristics (density characteristic curve) of the photographic light-sensitive material (photographic light-sensitive emulsion) which is a recording medium. That is, the photographic density of the color original image which is a medium image is linearly related (the linear relationship of 45 ° of 1: 1) to the exposure amount (logarithmic value) which is the image information value from the subject (substantial image, real scene). Not what I did. It is well known that the discrimination characteristic of light and darkness in human vision is logarithmic, and humans can determine the amount of light incident on the visual system from a subject (substantial image) based on the discrimination characteristic described above. I am evaluating. Here, the gradient of concentration change is linear
I feel something that is natural.

As is clear from the above description, in the production of a color print image, when the color separation work is carried out by using the density value (D = logIo / I) of the medium image recorded on the photographic light-sensitive material as a clue, it becomes a photograph. Since the density information value after being affected by the photosensitivity of the photosensitivity material is used, the image information value (light intensity value) obtained from the subject (real image, real scene) that is the true target of duplication is used. It's not what you're doing. Based on the above situation, the present inventors have
An approach that uses the image information value of the medium image, that is, the density value, which is changed non-linearly by the photosensitive characteristic (density characteristic curve) of the recording medium (photosensitive material) for producing a color print image. Instead of the first (raw, primitive) obtained from the subject (real image, real scene)
The method of producing a printed image based on the image information value related to the light amount such as the exposure amount was earnestly studied.

As a result, in the density gradation conversion work which is primarily important in the color separation work, (1). The density characteristic curve (photographic density characteristic curve of a photographic light-sensitive material on which a color original image is photographed and recorded. ), The value of the horizontal axis (logE) is obtained from the density value of the vertical axis (D = logIo / I) (hereinafter, the vertical axis is also referred to as the D axis and the horizontal axis as the x axis). The light amount value on the x-axis is calculated from the density value on the D-axis of (medium image), and (2) More specifically, the density on the D-axis of any pixel point (n point) on the color original image. The information value (D _n ) is projected on the X axis through the density characteristic curve to obtain the image information value (x _n ) related to the exposure amount of the corresponding pixel, and then,
(3). Based on the x _n value (light amount value) obtained as described above, and the gradation conversion formula previously proposed by the present inventors (this is adopted in the present invention described later). However, the present invention is completely different in terms of use and application of the gradation conversion formula.) Subject (real image,
It has been found that a color print image with excellent image quality that is faithful to real images is produced.

The gradation conversion technology previously proposed by the inventors of the present invention is, as is apparent from the above, the first meaning in producing a color print image of halftone dots. It is applied for the gradation conversion, which is important in particular. That is, the gradation conversion technology proposed by the present inventors has a fidelity of 1: 1 for the density gradation of various original images including color original images, and the human vision It is used to produce a reproduction image of natural color gradation. The gradation conversion technology described above is not limited to standard color original images, but also non-standard originals (overexposed or underexposed, high-key or low-key originals, color fog or fading). Even in this case, it is useful for reproducing the density gradation that is recognized to be possessed by the subject (substantial image). In addition, it was confirmed that the tone conversion technology described above can reproduce a rich tone of color (color tone) based on faithful reproduction of density gradation.

However, as described above, the gradation conversion technology previously proposed by the present inventors is as follows. Firstly, the gradation conversion is emphasized in the color separation work. Emphasizing realization of density gradation Hi-Fi conversion (conversion of gradation with a high fidelity of 1: 1 between a continuous gradation original image and a halftone dot reproduction image) It was confirmed that the gradation conversion technology can perform the gradation conversion with high fidelity and rationally, and that the tone can be reproduced richly along with the gradation conversion.

By the way, the market needs for the quality of the color print image are not limited to the need to reproduce the color print image having the tone (gradation and color tone) according to the color original image, and are becoming more sophisticated, complicated and diversified. It is coming. For example, a specific part (person, ceramics,
Clothes, furniture, woodworking products, paintings, etc.) or specific parts (areas) should be emphasized and reproduced, or the overall color tone should be blue, dark green, light green, pink, sepia. There is a need to change to the desired one. To meet these needs, for example, conventional color correction (color correction)
In the case of using technology, even if the color tone of a specific portion can be reproduced as required, the tone of the entire image is distorted and the image quality is severely deteriorated. Needless to say, in order to meet the above needs, we have established a gradation and color tone conversion technology that gives the human eye a natural feeling in both the tone of a specific portion or region (region) and the tone of the entire image. It is important to.

In order to meet the above-mentioned sophistication and complexity of market needs, it means that in the color separation technology, the gradation conversion technology and the color tone adjustment technology must be unified (integrated). It is a thing. In that case, the point to be noted is that the halftone dots that form the color print image are always in gradation (gradation) and color tone (color tone).
Alternatively, it has a direct relationship with both density and color. This is natural because the image quality is determined by the size of the halftone dot (defines the density gradation) and the colored ink applied on the halftone dot (defines the color tone). . Then, the present inventors have established means for rationally adjusting and managing the size of halftone dots (halftone dot% value) in the gradation conversion technique proposed previously. Therefore, the inventors of the present invention are keenly aware that the integration of the gradation adjustment technology and the color adjustment technology described above is an extension of the gradation conversion technology previously proposed by the inventors. Considered.

As a result, the inventors of the present invention have adopted the tone conversion formula which is the core of the previously proposed tone conversion technique, and when the idea of color tone adjustment is fused to this, the tone separation is performed in the color separation work. We have found that both gradations can be adjusted and managed rationally. The present invention has been completed on the basis of the above-mentioned findings, and according to the present invention, a color separation technique for adjusting and managing both the color tone and the gradation reasonably, and in particular, the rich gradation which is difficult in the prior art. It is intended to provide a color scanner incorporating a color tone management and adjustment technology capable of adjusting a color tone to a desired one in reproducibility.
The color scanner of the present invention has a great feature in that it is equipped with the color separation technology in which both the gradation and the color tone are integrated as described above. However, in the following description of the color scanner of the present invention, in view of the current situation that the prior art cannot reasonably and quantitatively manage the color tone, in particular, the gradation conversion unit, which is a core component of the color scanner, is described. The explanation is given with emphasis on the color tone management adjustment function.

[0024]

The present invention will be summarized as follows.
The present invention relates to a color scanner for producing a printing plate for producing a halftone dot color print image by subjecting image information of a continuous tone color original image to tone conversion by a tone conversion unit of a color scanner, The gradation conversion unit (1). Characteristic curve of a recording medium on which a color original image is recorded [a light amount value (x value) incident on the recording medium and a density value (D value formed on the recording medium A characteristic curve that defines the relationship with D) in a D-x Cartesian coordinate system], the function to obtain the light intensity value (x value) from the density value (D value), (2). Is a gradation conversion using the following <gradation conversion formula> to obtain a halftone dot% value (y value), and (3). The color tone adjusting function is (3) -1. The color print image is formed at a desired portion between the H portion (the brightest portion) and the S portion (the darkest portion) of the color original image. Color management point for managing the tone (M
₁ ) is set, and (3) -2. Color tone management point (M ₁ )
In the case of the color tone adjustment conditions, the desired color plate (C plate, M
Plate, Y plate, and BL plate), and is defined by the halftone dot% value, (3) -3.
The light amount value at the color tone management point (M ₁ ) and the halftone dot% value of the color plate reflecting the adjustment condition of the color tone, and the H part and S
The desired halftone dot value to be set in the part is substituted into the following <gradation conversion formula> to determine the γ value, and the light amount value of the pixels from the H part to the S part of the color plate is converted into the halftone dot% value. Each pixel for each color plate is prepared by using the <gradation conversion formula> for each color plate for which the <gradation conversion formula> for tone conversion is prepared and (3) -4. And a color tone adjusting function configured to manage and adjust the color tone while performing gradation conversion of the light amount value of the color scanner. <Gradation conversion formula> y _n = y _H + [α (1-10 ^−kx ) (y _S −y _H ) /
(Α-β)] In the above item <tonal conversion formula>, the meaning of each symbol are as follows; x: shows the (x _n -x _H). That is, the color similarly obtained from the light amount value (x _n ) corresponding to the density information value (D _n ) at any pixel point (n point) of the color original image obtained by using the characteristic curve of the recording medium. The basic light amount value obtained by subtracting the light amount value (x _H ) corresponding to the density information value (D _H ) of the H portion of the original image is shown. y _n : Halftone dot% value set to a pixel on the color print image corresponding to an arbitrary pixel point (n point) on the color original image. y _H : Halftone dot% value preset in the H portion of the color print image corresponding to the H portion of the color original image. y _S : Halftone dot% value preset for the S portion on the color print image corresponding to the S portion on the color original image. α: Surface reflectance of an image expression medium for recording a color print image. β: Numerical value determined by β = 10 ^−γ . k: Numerical value determined by k = γ / (x _S −x _H ).
However, x _S represents a light amount value (x _S ) corresponding to the density information value (D _S ) of the S portion of the color original image obtained by using the characteristic curve of the recording medium. γ: arbitrary coefficient.

The technical construction of the color scanner of the present invention will be described in detail below. For convenience of description, the image information value and the document image will be described here. In the color scanner of the present invention, the image information used in producing a color print image from a color original image does not use the image information value correlated with the density as in the prior art, but the image information correlated with the light amount. There is a major feature in using. In the present invention, the color original image is
The image is recorded or accumulated in a predetermined recording medium, and is also called a medium image. On the other hand, an image before being recorded or accumulated in the recording medium, that is, an object that is a true target of duplication is called a substantial image (subject, actual object, real scene).

First, in order to gain an understanding of the present invention, a method of adjusting a color tone will be described in detail later. An outline of a gradation conversion technique using the <gradation conversion formula> will be described below.
explain. As described above, at present, a color scanner color separation device is very commonly used in the duplication work of a color print image, and the color separation work by the device is performed by a color original image (a transparent original and a reflection original as medium images). including.)
It is carried out based on the concentration information value obtained from.
More specifically, as a conventional method for producing a color print image, generally, a C plate (cyan) and an M plate (magenta) based on density information values obtained from a color original image (medium image) through R, G, and B filters. ), Y version (yellow), and BL version (black). However, for example, the method of using the density information value of the color film (transmissive) original image (medium image) recorded on the recording medium, which is a photographic photosensitive material, as the color original image has the above-mentioned limitations (defects). It is a thing.

On the other hand, according to the present invention, as described above,
The true target of the copy is not the image recorded on the recording medium (medium image) but the literal color original image of the medium image, that is, the subject (substantial image) itself, and the image to be used at the time of duplication. The information value is based on the idea that the information value should be based on the image information value correlated with the amount of light incident on the recording medium from the subject. The above points are the basic differences between the gradation conversion technique of the present invention and the conventional technique.

This will be described below from another angle. In the color separation technique, it is necessary to convert a continuous-tone color original image (for example, a transmissive color film original) into a halftone dot-tone color original image. A color separation curve (gradation conversion curve) defines the correlation between halftone dot images. The conventional color separation curve is formed on the D axis (density axis) of the photosensitive characteristic curve (photographic density characteristic curve defined by the D axis-X axis orthogonal coordinate system) of the photographic light-sensitive material as the recording medium. It is set based on the density information value. On the other hand, the color separation curve of the present invention is set on the basis of the image information value correlated with the light quantity of the subject (real image) on the x-axis of the photographic density characteristic curve as described above. That is, while the conventional color separation technology uses the D-axis color separation curve,
It can be said that the present invention uses the X-axis color separation curve, and both are basically different.

Next, in the image gradation conversion method using the <gradation conversion formula> of the present invention, a method of obtaining the image information value of each pixel of the color original image, that is, the light amount value will be described.
First, the characteristic curve of a photographic light-sensitive material as a recording medium used for photographing a color original image (medium image), specifically, the photographic density value (D = logIo / I) and the subject (substantial image, actual scene), The image information value correlated with the amount of light incident on the photographic light-sensitive material that is the recording medium, that is, the exposure amount (E =
A concentration characteristic curve showing the relationship between It) and the logarithmic value is prepared. Next, from the density value (D _n ) of an arbitrary pixel (n point) in the color original image, the light quantity value (x
_The concentration characteristic curve is functionalized to obtain _n ).
For this purpose, for example, a density characteristic curve corresponding to the recording medium provided as a technical material by a photographic light-sensitive material manufacturer may be made into a function. If it can be rationalized into a function, D on the D axis
_{The n} value can be easily converted into the x _n value on the x axis.
FIG. 1 shows the concentration characteristic curve (Fujichrome, manufactured by Company F).
Further, Table 1 shows the result of formulating the concentration characteristic curve of FIG. In addition, as shown in Table 1, in order to formulate the concentration characteristic curve as accurately as possible, the formulating section is set to 8 sections, and the formulating is attempted in each section. It goes without saying that the more functional divisions, the more accurate the functional formula can be obtained.

[0030]

[Table 1]

In the mathematical expression of the density characteristic curve, an image information value correlated with the scale of the D axis indicating the density value of the color original image (medium image) and the light amount indicated by logE of the subject (substantial image). Assuming that the scales on the X-axis are the same, a function that defines the correlation between D and X was obtained. This is a kind of imitation made from the following viewpoints, and the present inventors consider that it is rational.
In this sense, the term canonical value is used on the X axis of FIG. That is, originally, in the photographic density characteristic curve, the logarithmic value of the exposure amount E on the X axis logE = logI ×
t) is located, which corresponds to the fact that the discriminative property for light and darkness of the visual sense is logarithmic as well as the perception of the density (visual sense) of the D axis, and thus the imitation on the above scale is reasonable. I think that is. It is needless to say that the above-mentioned grading in the present invention is a kind of simple method and is not limited to this.

In the present invention, as described above, the density value (D) of the color original image (medium image) formed by photographing and recording the subject (substantial image) on the recording medium (photosensitive material for photography).
_n value) rather than based on, is to subject (entity image) correlated image information value to the amount represented by the x-axis is incident on the recording medium from the (x _n values) based. As described above, since the D _n value and the x _n value are correlated by the functional formula of X = f (D) as shown in the concentration characteristic curve in Table 1, it is easy to change the x _n value from the D _n value. You can ask.

Next, the gradation conversion technique of the present invention uses the light quantity value (x _n value) obtained as described above and the <gradation conversion formula> to perform a color separation curve (gradation conversion curve). That is, it suffices to obtain an x-axis color separation curve that replaces the conventional D-axis color separation curve and perform tone conversion of the image. That is,
Under a predetermined density characteristic curve, an image information value (x _n ) correlated with the light amount of the corresponding pixel is obtained from the density value (D _n ) at an arbitrary pixel (n point) on the original image, and the (x _n ) By substituting the _n ) value into the <gradation conversion formula>, the gradation intensity value (y _n ), that is, the halftone dot area% value (hereinafter, simply referred to as halftone dot% value) (y _n ) is calculated. . This halftone dot% value (y _n ) may be input to the halftone dot generator (dot generator) of the color scanner to form a desired screen.

The above-mentioned <gradation conversion formula> derivation process of the present invention will be briefly described here. Halftone dot% value (y _n ) used when producing a color print image having the above-mentioned halftone dot gradation
<Gradation conversion formula> is a generally accepted density formula (photographic density, optical density), that is, D = logIo / I = log1 / T Io = incident light amount I = reflected light amount or transmitted light amount T = I / Io = It is derived from the reflectance or the amount of transmitted light. The general formula for the density D described above is applied to plate making / printing as follows. Density (D ') in plate making / printing = log (Io /
I) = log unit area × paper reflectance / [(unit area−
Halftone dot area × paper reflectance) + halftone dot area × ink surface reflectance] = log αA / [α {A- (d1 + d2 + ... d
n)} + β (d1 + d2 + ... dn)] where A: unit area dn: area of each halftone dot within the unit area α: reflectance of printing paper β: surface reflectance of printing ink.

The present invention is based on the density formula (D ') relating to plate making and printing, and a basic density value (x) at an arbitrary sample point (pixel) (n point) on a continuous tone color original image, In order to associate the theoretical value with the actually measured value in association with the halftone dot% value (y _n ) of the halftone dot at the sample points on the color print image corresponding to this halftone gradation, Is derived.

[0036] In operation of the of the present invention <tonal conversion formula> generally 5% y _H in C plate, 95% y _S, 3 percent y _H in M plate and Y plate, 90% y _S Is used. In the operation of the <gradation conversion formula>, if the densitometer measurement value is used for the density value and the percentage value (% value) as described above is used for y _H and y _S , the y _n value also becomes the percentage value ( % Value).

In the operation of the <gradation conversion formula> of the present invention, it is possible to use it not only by modifying it as follows, but also by using it by arbitrarily processing, deforming or guiding it. y _n = y _H + E (1-10 ^−kx ) · (y _S −y _H ), where E = 1 / (1−β) = 1 / (1−10 ^−γ ), α = It is one. This is one in which the surface reflectance of the printing paper (base material) used for expressing a color printing image is 100%. The value of α may be any value, but may be 1.0 in practice.

According to the modification (α = 1.0), the y _H value is planned in the brightest part (H part) and the y _S value is planned in the darkest part (S part) on the color print image. It can be set as described above, which is a major feature of the present invention.
By the definition, the above-mentioned point is that x = 0 in the H portion on the color print image, and x = in the S portion.
It is clear that x _S −x _H , that is, −k · x = γ · (x _S −x _H ) / (x _S −x _H ) = − γ. Thus, according to the present invention
By using the gradation conversion formula> (a modified example of a = 1), it is possible to always set the planned y _H value and y _S value in the H portion and the S portion on the color print image. This point is
This is a very important point for users to evaluate and consider the work results. That is, y _H and y _S in the color print image
Set the desired value to and change the γ value (however,
= 1.0), various X-axis color separation curves (gradation conversion curves) can be obtained. Then, the image quality contents of the color print image produced under these X-axis color separation curves can be easily evaluated in relation to the γ value.

X of each color plate for multi-color plate making (generally, four plates of C plate / M plate / Y plate / BL plate are used) utilizing the <gradation conversion formula> of the present invention. To set the axis color separation curve (gradation conversion curve), the following may be done.
In the industry, it is common practice to first set a reference C color separation curve (gradation conversion curve), and then set the other color plates so that the gray balance and color balance are maintained. Is. The maintenance of the gray balance described above is a condition for reproducing a neutral density (gray) by three color plates (C / M / Y plates), and is an important requirement. In the industry, standard values shown in Table 2 below are generally adopted in order to maintain the gray balance. In Table 2, M ₁ is a gray balance management point (hereinafter, also referred to as an intermediate point) set in the intermediate portion of the dynamic range (density area) of the H portion to the S portion. In the art, the M ₁ point is usually set at a dot% value of C plate of 50% as shown in Table 2.
The main reason that the M ₁ point is set to the halftone dot 50% value of the C plate is that it is widely recognized that the halftone dot% value region is a reproduction region with rich gradation. From Table 2, in the art, in the M ₁ point (halftone), the halftone dot value of C plate is 50%, and the halftone dot value of other color plates (M / Y plate) is 4%.
It is understood that the gray balance is maintained by setting it to 0%.

[0040]

[Table 2]

As described above, the gradation conversion technique of the present invention is
In producing a color print image, the density information value (D _n ) obtained from a color original image (medium image) is not used, but is incident on a recording medium for forming a medium image from a subject (substantial image). It is premised that the image information value (x _n ) correlated with the amount of light is used and the <gradation conversion formula> is used, and the color has gradation characteristics faithful to the subject (real image). It is possible to produce a print image, and further, a color print image in which gradation characteristics are changed to a desired one, with work regularity, universality and elasticity.

Next, the core technical constitution of the present invention, that is, incorporating the tone adjustment technique into the above-mentioned tone conversion technique, in other words, integrating the tone conversion technique and the tone adjustment management technique. Will be described. The trigger for the integration of the gradation and the color tone was as follows. (1). The <gradation conversion formula> proposed by the present inventors and used in the present invention is, as described above, a network of all pixels from the H part to the S part of the color print image. Dots
The halftone dot% value (in other words, the size of the halftone dot) of the original faithfully reproduces the gradation characteristic of the color original image, and the gradation characteristic is natural to human vision. It is an important tool for adjusting to. (2). The halftone dot value set for each pixel always has a direct relationship and influence on both gradation and color tone (or density and color). (3). As market needs, not only 1: 1 reproduction of color original image (Hi-Fi reproduction), but also enhancement of color tone of specific part of image, specific part of dynamic range of H part to S part,
The number of cases requiring (changing) changes and modifications is increasing. In addition, in the above request, customers and designers
The requested contents are presented and specified by halftone dot% values by a color chart owned by them (which will be described later in detail). (4). When responding to the above needs by conventional color separation technology, particularly conventional color correction (color correction), even if the color tone of a specific portion is approximated to the requested content,
In many cases, the tone (gradation and color tone) of the entire image is distorted, and the value of the product is lost.

The color chart is a basic scale (reference table) for color reproduction in which all the colors are expressed by density gradation of halftone dots using the printing process 4 primary color inks. For example, "DIC GRAF-G Color Chart" issued by Dainippon Ink and Chemicals, Inc.
(March 1991). In the color chart, there are various combinations as shown below as combinations of each color plate for color reproduction. 1. Basic combination: C (cyan) and M (magenta)
There is a chart based on the combination of. For example, (C) is printed on the vertical axis and (M) is printed on the horizontal axis in 12 gradations with halftone dot% values of 0 to 100% to form a basic pattern. There is a structure in which Y (yellow) and BL (sumi) having a% value are printed and overlapped. As Y or BL of the constant halftone dot% value, Y = 10
%, BL = 10%, Y = 10%, BL = 30
%, Y = 50%, BL = 10%,
and so on. 2. Other combinations: (1). A combination of (Y) on the vertical axis and (M) on the horizontal axis,
(2). A combination of (C) on the vertical axis and (Y) on the horizontal axis,
(3). A combination of (BL) on the vertical axis and (Y) on the horizontal axis,
(4). A combination of (BL) on the vertical axis and (M) on the horizontal axis,
(5). A combination of (C) on the vertical axis and (BL) on the horizontal axis.

As described above, the color tone on the color chart is designated by the dot% value of each color plate (C / M / Y / BL). Therefore, in response to a color tone change request from a customer or a graphic designer based on the color chart, a technology for quantitatively and rationally managing and adjusting all halftone dot% values of each pixel is used as a color separation technology. It goes without saying that we must secure it.

From the background described above, the present inventors have
The gradation conversion formula> has the ability to completely quantitatively and reasonably manage and adjust the halftone dot value of all pixels from the H point to the S point, and is therefore effective for adjusting the color tone. I thought it would be a powerful tool. This is an opportunity to develop a color separation technique that integrates gradation and color tone using the <gradation conversion formula> as a main tool.

As described above, the color scanner of the present invention is characterized in that the gradation conversion section, which is the core component thereof, incorporates the color separation technology in which gradation adjustment and color tone adjustment are integrated. Is to have. Particularly, in the present invention, the color separation technique incorporating the color tone management adjustment is significantly different from the conventional technique, and this point will be described below.

1. First, a color tone management point (M ₁ ) for managing the color tone of the color print image is set at a desired portion between the H portion and the S portion of the color original. In the present invention, the same symbol (M ₁ ) as the halftone point (M ₁ ) for maintaining the gray balance in Table 2 is used as the symbol of the color tone management point (M ₁ ). This reflects that the tone reproduction in the halftone region is an important point in the color separation technique, and thus is also important in the tone reproduction. Needless to say, the color tone management point (M ₁ ) is not limited to the halftone point for maintaining the gray balance, and may be a desired point between the H portion and the S portion. .
The color tone management point (M ₁ ) displays a vertical axis (y-axis: halftone dot% value) and a horizontal axis (x-axis: light amount value), as will be described later in the embodiment and in FIG. .) Cartesian coordinates are displayed with the light amount value on the horizontal axis. Since the light quantity value correlates with the density value of the color original image, it may be displayed as the density value.

2. Next, at the color tone management point (M ₁ ) designated as described above, the color tone adjustment condition is determined by the halftone dot value of the desired color plate (C plate, M plate, Y plate, and BL plate). To do. The specific content of the adjustment (change) condition of the color tone is as described in the description of the color chart.

3. The next step is to use each of the color plates (C plate, M plate, Y plate, BL
Preparation of the color separation curve (gradation conversion curve) used for producing the color separation image of (version), more specifically, the <gradation conversion formula> for setting the color separation curve for each color plate. Preparation. By the above steps (1 to 2), the light quantity value of the color tone management point (M ₁ ), for example, M ₁
= 0.400, ・ Color tone adjustment conditions, for example, C plate halftone dot% value (50%),
Halftone dot value for M plate (20%), Halftone dot value for Y plate (10%), B
The halftone dot% value (10%) of the L plate is set. The halftone dot% values (y _H , y _S ) set in the H and S parts of each color plate are set to values given in advance or desired values. The y _H value and the y _S value given as the above-mentioned conditions are 5% and 95% for the C plate, respectively, as described in the description regarding the operation of the <gradation conversion formula> of the present invention. %, And 3% and 90% for M plate and Y plate, respectively (see Table 2). Under the above conditions, the γ value of the <gradation conversion formula> used to determine the color separation curve for each color plate is determined. For example, the γ value of the <gradation conversion formula> for determining the color separation curve for C plate is determined as follows. <
Gradation conversion formula>, x _H = 0.00, x _S = 1.00, x _n = M ₁ = 0.4
0, α = 1.00, y _H = 0 (%), y _S = 95
By substituting (%), y _n = 50% for solving, a value of γ = 0.45 is obtained. As a result, <gradation conversion formula> for setting the color separation curve for C plate is prepared. The same applies to other color plates.

4. The next step is the γ value (0.
45) is used, the light amount values (x _n ) of all pixel points (n points) from the H section to the SH section are subjected to gradation conversion, and the C separation color separation curve ( This is a step of obtaining a gradation conversion curve). In other words, the color separation work is performed using the <gradation conversion formula> for the C plate in order to produce the C plate color plate image. The same applies to other color plates.

The effectiveness of the color separation technology in the gradation conversion unit in which the gradation adjustment technology and the color adjustment technology in the color scanner of the present invention described above are integrated will be demonstrated in the examples described later. Here, other features and application fields of the color scanner of the present invention, in particular, the color separation technique incorporating the gradation and color tone adjusting function in the gradation converting unit will be described. The color separation technology in the gradation conversion unit of the color scanner of the present invention is
For all fields where color print images are to be produced from color original images (medium images) obtained by recording, photographing or image-converting a subject (substantial image) on a desired recording medium using information transmission media such as light and electromagnetic waves. Can be applied. Therefore, it goes without saying that the color separation technology of the present invention must be operated so as to be compatible with the system for producing each color print image.

First, the characteristic curve of the recording medium, that is, the correlation between the image information value (light amount value) that correlates with the amount of light incident on the predetermined recording medium from the subject (substantial image) and the density information value formed on the recording medium. In the specification of the concentration characteristic curve showing
The prescribed variable (factor) of the characteristic curve is not limited to the combination of the logarithmic value (light amount value) of the exposure amount and the density information value as described in the color original image. Subject (real image)
As the characteristic curve of the sensor which is the input medium (recording medium) of the image information, the density information value (D _n value) which is interpreted in the broadest sense and correlated with the density and the image information value (x _n ) which is correlated with the light amount
A density characteristic curve (photoelectric conversion characteristic curve) that correlates with is defined. As a physical quantity indicating an image information value correlated with this kind of density, it should be understood in the broadest sense.For example, as synonyms, reflection density, transmission density, brightness, brightness, frequency, current / voltage value, etc. There is. Further, as a recording medium on which a subject (substantial image) is recorded, a photographic light-sensitive material,
Alternatively, it may be a photoelectric conversion element such as a two-dimensional CCD, an optical disk, a magnetic disk, a magnetic tape, or a photodiode. In relation to the above-mentioned recording medium, the density characteristic curve which is a characteristic of the recording medium is referred to as a photographic density characteristic curve (in the case of a photographic photosensitive material), a photoelectric conversion characteristic curve (in the case of a photoelectric conversion element), etc. Needless to say. When the color original image is a reflection original, the density characteristic curve is 45 ° in the Cartesian coordinate system.
It goes without saying that it is defined by the straight line of (degrees).

The color scanner in the present invention should be construed in the broadest sense, as is clear from the above, and is construed to mean all devices that perform color separation for producing a color print image. It should be. Specifically, the color scanner referred to in the present invention is not limited to various types of existing stunt alone type (stand alone type) color scanners and total scanners, but a separate type color input device that operates at a workstation. (Color getter) and color output machine (color setter), which are related to the production of color print images, mean all those that have a color separation function that integrates the gradation and color tone described above. Should be interpreted.
The color original image mounting mechanism may be a rotary drum type or a flat bed type.

In the present invention, halftone dot gradation or halftone dot%
Although the term value is used, the reproduction of color printed images is not limited to only the dot format. For example, recent FM (Frequency modulation, or Stocha)
stic) screening method, specifically, a method of modulating the area of a conventional halftone dot (this is also called AM or Amplitude modulation in connection with the FM).
Instead, it also includes a format in which the tone (gradation and color tone) of a predetermined pixel is expressed by density modulation of minute dots (microdots).

Next, in the color scanner of the present invention,
The configuration of the gradation conversion unit, which is the main constituent element (mechanism) of the above-mentioned gradation and color tone adjustment, and which performs color separation by integrating them will be described. 1. In the present invention, the gradation conversion unit is configured as follows, for example. (1) .Predetermined recording medium (sensor)
A density characteristic curve defining the correlation between the density information value obtained from the color original image recorded on the recording medium and the image information value correlated with the amount of light incident on the recording medium (sensor) from the subject (actual image). On the basis of, the correlation with the light quantity corresponding to the image information value and / or the image information electric signal value (analog or digital, either) relating to the density of the color original image (including hard original and soft original) It is configured to include a mechanism (corresponding to software) for obtaining the image information value described above, and a mechanism (corresponding to software) for operating (2).

2. In addition, the configuration of the output unit is the current value or voltage value of the recording unit (recording head) of the device, or its value, corresponding to the value calculated by the <gradation conversion formula>, that is, the y _n value (halftone dot% value) A halftone (halftone dot gradation) color print image in which the gradation and color tone are adjusted as desired is output by controlling the application time and changing the halftone dot size (halftone dot% value). It may be configured as follows.

For example, in order to produce an original plate of a color print image which is a halftone dot image, that is, an original plate for printing (color plate image) using the color scanner of the present invention, a commercially available electronic device well known in the art is used. By incorporating the gradation conversion unit having the above-described gradation and color tone integration function of the present invention into the color separation mechanism unit (gradation conversion unit) of a dynamic color separation device (color scanner, total scanner), etc. To be achieved. More specifically, a small spot light is applied to a color film original image (transmissive medium image), and the transmitted light (image information signal) is received by a photoelectric conversion unit (photomul) to determine the intensity of the light. Is converted into the strength of the voltage, and the obtained image information electrical signal (voltage value) is arranged and processed as required by the computer, and is exposed based on the processed image information electrical signal (voltage value) output from the computer. It is possible to use a known existing system in which the light source light for control is controlled and then the spot light of the laser is applied to the raw film to form the printing original plate (color plate image).

At this time, the computer processing mechanism for organizing and processing the image information electric signals of the color original image (medium image) is reconfigured, and the color original image recorded on the color film (recording medium) ( The image information value correlated with the light amount is obtained from the density information value of the medium image) through the density characteristic curve of the color film (recording medium), and the halftone dot value (y _n value)
All you have to do is to incorporate software that outputs.

As can be seen from the above description, a color original image (a medium image photographed and recorded on a recording medium called a photographic light-sensitive material) is recorded by a scanner image information acquisition mechanism, specifically, a photoelectric conversion unit (photomul). Image information values that are processed to correlate with density are obtained. Strictly speaking, since the photoelectric conversion unit has its own characteristic curve (photoelectric conversion characteristic curve), in the photoelectric conversion unit, the image information of the color original image is equivalent to that of the photoelectric conversion unit. It will be affected (altered or deteriorated) by the photoelectric conversion characteristic curve. Therefore, it is preferable to eliminate the influence of the photoelectric conversion characteristic curve, but this may be ignored. In other words, the image information of the color original image is affected (altered or deteriorated) by the photoelectric conversion characteristic curve of the photoelectric conversion unit. Therefore, it is preferable to eliminate the influence of the photoelectric conversion characteristic curve, but this may be ignored in consideration of the characteristics of the photoelectric conversion unit.

As the software applied to the above-mentioned gradation conversion unit, image information which correlates the density information value (D _n ) correlating with the density of the color original image with the corresponding light quantity under a predetermined density characteristic curve is used. A general-purpose computer that converts into a value ( _xn ) and has the algorithm of <gradation conversion formula> as software and has an A / D (analog-digital conversion) and a D / A I / F (interface), An electrical circuit that embodies a general-purpose IC with the algorithm as logic, and an RO that holds the algorithm operation result
Various forms such as an electric circuit including M, a PAL in which an algorithm is embodied as an internal logic, a gate array, a custom IC, and the like can be taken. Particularly in recent years, modularization has been developed, and an arithmetic mechanism capable of performing gradation conversion of an image based on the above <gradation conversion formula> of the present invention is a dedicated IC, LSI, microprocessor, or microprocessor. It can be easily manufactured as a module such as a computer. Then, the spot light for photoelectric scanning is sequentially scanned while being divided into dots, while the laser exposure unit for irradiating the raw film with the laser light is also synchronized with this, by the <gradation conversion formula> described above. A printing original plate (color plate image) in which the gradation of halftone dots and the color tone having the derived halftone dot value (y _n ) are adjusted as desired is rationally produced.

[0061]

Embodiments of the color scanner of the present invention will be described in detail below with reference to the drawings. Further, the color separation method (gradation conversion method integrating gradation and color tone adjustment) using the color scanner of the present invention will be described in detail. It should be noted that the color scanner of the present invention can be said to apply a new gradation conversion unit to an existing color scanner to rationalize and simplify the configuration and improve added value, as shown below. .

FIG. 2 is a block diagram showing the arrangement of the color scanner of the first embodiment of the present invention. As shown in the figure, the existing color scanner (rotating drum type) to which the present invention is applied is made up of the following four blocks. (1). A detection unit (1) for reading image information of a color original image. The detection section (1) reads the density information value of the color original image by the R / G / b color filters. (2). A color separation unit (2) that converts the output signal of the detection unit (1) into C, M, Y, and BL color separation signals. In the following, BL
The (black) component is represented by the symbol K. The color separation unit (2)
Is BM (8) (basic mask circuit, C / M / Y
The basic <one-stage> color correction circuit that corrects the deviation from the ideal color of (1) and CC (9) (a two-stage color correction circuit in the color correction circuit). (3). Gradation adjustment section (3). This is because the existing color scanner mainly consists of the gradation correction circuit.
It is composed of a circuit for determining how to adjust the tone of halftone dots between the H part and the S part. (4). An output unit (4) for exposing the raw film with a laser beam based on the output signal of the gradation adjusting unit (3).

In the present invention, among the four blocks,
The detection unit (1), the color separation unit (2), and the output unit (4)
The mechanism and structure of the conventional color scanner are used as they are. In other words, the gradation adjusting unit (3) is the object of the improvement of the present invention. Strictly speaking, the gradation conversion unit based on the <gradation conversion formula> which integrates the gradation and color tone adjustment of the present invention to perform color separation is a color separation unit. This is related to the function improvement of (2). . Therefore, the color scanner of the present invention is configured by using the color separation unit (2) of the existing color scanner and changing the configuration of the conventional gradation conversion unit to the gradation conversion unit of the present invention. You can

Regarding the configuration of the color scanner of the present invention,
Hereinafter, a specific description will be given. The detection unit (1) described above detects the transmitted light or the reflected light of each portion of the color original image (5) such as photomul, and detects R, G, B, and US as current values.
Each M signal is output, and this signal is converted into a voltage signal in the A / V converter (6). The color separation unit (2) includes R, G, B and USM of the detection unit (1) in the log amplifier (7).
Each voltage signal is logarithmically calculated and converted into a density, and the basic masking (BM) (8) separates each color component (basic color component) of C / M / Y and the component into gray. Next, in the color correction (CC) section (9), the C plate component, the M plate component, and the Y plate component are controlled for each of the R, G, B, and C, M, Y document colors, and the K plate component is UCR. / UCA Department (10) UCR
(Undercolor removal) or UCA (under color
In addition), the ratio expressed in the three color plates of C, M, and Y and the ratio expressed in the K plate are determined.

That is, in the color scanner of the present invention,
A color original image (5), which is an object to be reproduced (color print, color transparent original, etc.), is first read by an image information reading mechanism configured by a photomultiplier or a solid-state imaging device (CCD) in the detection unit (1) by a conventional method. For each color (R,
The image information of G and B) is detected, and color separation is performed in the color separation unit (2) to obtain a density information value (D _n ) for producing a color print image. This is obtained for each color (C, M, Y) component (basic color component) as described above. The density information value (D _n ) is an image information value (x _n ) correlated with the light quantity, and further, a basic light quantity value, by using a photographic density characteristic curve of a recording medium for color original images, for example, a photographic photosensitive material. It goes without saying that it is converted into (x). In addition, in order to obtain the image information correlated with the above-described light amount, it may be performed by software or hardware (not shown). In the present invention, the above-mentioned density information value image information values correlated with the amount of light from the (D _n) (x _n) and the function for obtaining basic amount value (X) is described next gradation adjusting unit (3)
May be incorporated into. This is because the gradation adjusting unit (3) operates an algorithm of <gradation conversion formula>, and the image information of the light quantity value correlation is also obtained by a predetermined algorithm, so that the calculation function is integrated. It is based on. Needless to say, the present invention is not limited to this method.

After the C, M, Y, and K components have been obtained as described above, in the prior art, the gradation control unit in the gradation adjusting unit (3) uses the halftone dot area ratio ce ', me ′, ye ′, ke ′ are obtained, and this is inversely log transformed by the inverse log transformation unit. On the other hand, in the color scanner of the present invention, the conventional gradation control unit described above
Based on the gradation conversion formula>, the gradation and the color tone are both replaced by a gradation conversion unit (11) capable of being integrated and adjusted. Here, from C, M, Y, BL to ce ′, me ′. , Ye
Convert to ', ke'. The gradation conversion unit (11) is simply represented as the conversion unit (11) in the drawing. The gradation converting unit (11), the algorithm obtains the light quantity value from the density value (D _n) by utilizing the characteristic curves of the recording medium having recorded thereon a color original image (x _n), and <gradation conversion It has a calculation algorithm of formula> inside. And C, M,
By applying the <gradation conversion formula> to each of Y and K, ce
Find ', me', ye ', ke'.

The gradation conversion unit (11) has the algorithm of <gradation conversion formula> as software and
/ D, D / A general-purpose computer having I / F (interface), general-purpose I using algorithm as logic
It can take various forms such as an electric circuit embodied by C, a PAL embodying an algorithm as an internal logic, a gate array, a custom IC, and the like. The halftone dot effective area ratio obtained by the gradation conversion unit (11) is input to the color channel selector (12), where ce ',
Me ', ye', and ke 'are sequentially and selectively output. This output value is A / D converted by the A / D conversion unit (13) and input to the output unit (4).

In the output section (4), based on the output of the gradation adjustment section (3), the dot control section (1
In 4), the laser beam is controlled. The laser beam controlled from the output unit (4) is irradiated onto the raw film to produce each color plate (C, M, Y) and BL plate.

Using the <gradation conversion formula> of the present invention as an important tool, in order to examine whether the gradation and color tone of a color print image can be reasonably managed and adjusted, the following 3
Experiments were carried out in stages: (1). Basic experiment (2). Applied experiment (3). Practical application experiment

In order to carefully examine the effect and effect of incorporating the tone adjustment management in the <tone conversion formula>, which is a useful tool for tone conversion, Experiments were carried out by incorporating the two methods. (1). Experiment A: Experiment of adjusting the halftone dot% values of both the color tone control point (M ₁ ) and S part of the three color plate images (C plate / M plate / Y plate). (2). Experiment B: Experiment in which only M ₁ points of three color plate images (C plate / M plate / Y plate) were adjusted.

<M ₁ point, light intensity value of M ₁ point and determination method of γ value for each color plate> (1). Color tone management point (M ₁ ) Color tone management point (M ₁ ) (see FIG. 3) The halftone widely used in the prior art for adjusting the gradation is set to a more precise point at which the halftone dot value of the C plate halftone image (color plate image) is 50%. This is in conformity with the standard value generally used in the industry for maintaining an appropriate gray balance. Needless to say, the color tone management point (M
It goes without saying that ₁ ) is not limited to the area of the halftone dot value 50% of the C plate.

(2). Light intensity value of color tone management point (M ₁ ) The light intensity value of the color tone management point (M ₁ ) was determined from the C plate color separation curve (gradation conversion curve). That determines the C plate color separation curve in <tonal conversion formula>, and screening use _{range: 0~95% (y H = 0} %, y S = 9
5%) ・ γ value: 0.45 ・ x _S = 1.00, x _H = 0.00 (x _S −x _H =
1.00) (Note) • y _n = 50 (%) (this is the halftone dot% value of the color tone management point (M ₁ )) is substituted into the <gradation conversion formula>, and the x value (Light intensity value at color tone management point) was determined. That is, the above conditions were substituted into the <gradation conversion formula>, and the following formula was solved for the calculation. As a result,
x = 0.40. 50 = 0 + [(1-10 ^-0.45x ) (95-0) / (1-
10 ^-0.45)] Note Generally, the dynamic range of light intensity values obtained from a color original image (medium image) (x _S -x _H) is 1.0
Although not 0, here the dynamic range is 1.
The value normalized to 00 is used. Needless to say, the dynamic range is 1.00
Even if the image quality is normalized to,
There is no problem in image processing.

(3). Method for Determining γ Value for Determining Color Separation Curve for Each Color Plate (C / M / Y / BL) In the following experimental example, a value for setting the C color separation curve is set. Uses the value of γ = 0.45 as described above. For other color plates, the γ value for setting each color separation curve (gradation conversion curve) must be obtained according to the content of the color tone adjustment conditions. For example, in the case of the M plate, at the color tone management point (M ₁ ) (this light amount value is 0.40), when the halftone dot value of the M plate is 20% and the halftone dot use range is 0 to 68%. , Can be obtained by solving the following equation. The following solution is γ = 0.20. 20 = 0 + [(1-10- ^{γ (0.40)} ) (68-0) /
(1-10 ^−γ )] In this experiment, the light intensity value at the color tone management point (M ₁ ) and the γ value for each color plate are automatically calculated, and a desired color separation curve is automatically prepared. I used software.

<Equipment and materials used in the experiment> (1). K. An image of a standard quality brown pottery jar taken with a 4 ″ × 5 ″ positive color film manufactured by the company was selected. (2). As a color scanner, ISOMET (US
A) A digital color scanner model 455 manufactured by A) with a modified gradation conversion unit was used. That is, software for obtaining a light quantity value (normalized light quantity value) from a density value through a photographic density characteristic curve (12 characteristic curves of typical photographic light-sensitive materials such as Fujichrome, Agfachrome, Ektachrome were prepared). A gradation conversion unit having software for performing color tone management using <gradation conversion formula> and software for calculating a color separation curve was incorporated into an ISOMET digital color scanner 455 type. (3). AGFA S712P was used as a color separation film. (4). For color proofing, DUPON's Cromamarin system was adopted.

<Basic Experiment> The purpose of this experiment is to confirm whether the tool of the present invention <gradation conversion formula> has a function of rationally adjusting the color tone of a color print image. Especially, it was confirmed whether the color tone can be adjusted rationally while maintaining the gradation. In Table 3,
The platemaking design data of each color plate for the management adjustment of the color tone for the basic experiment is shown. (Note 1) In experiment A, the halftone dot% value of the S part was specified first, and then the halftone dot% value of M ₁ point (color tone control point) was obtained by the following equation (1) and experimented. In addition, the following formula (2)
Standard halftone dot% values for are shown in Table 2. Dot% values of M ₁ point = (M standard dot% values of points ₁₎ × (dot% values specified in the S portion) / (standard dot% value of the S portion) ......... (1) ( Note 2) In Experiment B, the value of Experiment A was adopted as the halftone dot value of M ₁ point, and the standard value (Table 2) was adopted as the halftone dot% value of S part. (Note 3) Since the catch light part is selected as the H part of the color original image (pot), the halftone dot% value of the H part of all the color plate images is “0” (zero).

[0076]

[Table 3]

The four experimental results of the basic experiment were all as expected in light of the plate making practice (experience).
This indicates that the color tone management method using the <gradation conversion formula> of the present invention is rational. The contents of the four color calibration images obtained from the basic experiment are as follows. (1) For all four points, the gradation (density gradation) is well reproduced in the entire dynamic range of the H to S parts, and the halftone volume feeling is also suitable for human vision. (2). The color tone of the vase is blue in Experiment A (No. 1 to No. 2), blue in the halftone area in Experiment B (No. 1 to No. 2), and the original in S part. It was brownish as shown in the image. It should be noted that these color tones are exactly the same as those in plate making practice.

Incidentally, the γ value for setting the color separation curve for each color plate of Experiment A (No. 1 to No. 2) and the halftone dot value (calculated value) at M ₁ point are as follows. (1). Experiment A (No. 1) C version γ = 0.45, M ₁ dot half value% value = 50,0000% M version γ = −0.20, M ₁ dot dot % Value = 30,9878% Y version γ = -0.18, M ₁ dot half value = 35,8678% (2). Experiment B (No. 2) C version γ = 0.45, M ₁ dot% value of the point = 50,0000% M Version gamma = -0.18, dot% values of M ₁ point = 26,9006% Y Version gamma = -0.20, dot% values of M ₁ point = 30,9878% The γ value of the BL plate is γ = -0.25.

Further, the outline of the basic experiment and the experiment A (N
o. FIG. 2 shows a color separation curve (gradation conversion curve) for each color plate used in 1) and Embodiment B (No. 1). (A) in the figure
Is a combination of color separation curves that has been adopted as a standard in the industry for maintaining gray balance. The platemaking design materials are given in Table 2. (A) in the figure
Is a combination of color separation curves (gradation conversion curves) of each color plate of Experiment A (No. 1), and (B) is Experiment B (No. 1).
The combination of the color separation curves (gradation conversion curves) of each color plate of 1) is shown.

<Applied Experiment> In this experiment, a color separation experiment is conducted in a method closer to the daily color separation work, and the color tone management method using the <tone conversion formula> of the present invention determines the color tone of the color print image. The purpose is to check whether or not it has a function for reasonably adjusting and managing. In this experiment, the color tone control point (M ₁ ) was the point at which the halftone dot value of the C plate image was 50%. In addition, the color tone management point (M
_As the basic scale for specifying the adjustment contents of the color tone in ₁ ) (specific details of correction and change of the color tone requested by the user etc.) with the dot% value of each color of C / M / Y of each color plate image, "DIC GRAF-" manufactured by Dainippon Ink and Chemicals, Inc.
G color chart "(March 1991, second edition). In this experiment, six colors were selected from the color chart. In Table 4, the above-mentioned "DIC GRAF-
6 types of colors selected from "G color chart" and designated halftone dot% values for color tone adjustment are shown.

In the color chart, the six types of colors are displayed in 12 levels between 0 and 100 as C / M halftone dot density, and Y / BL (constant halftone dot density, for example, As shown in Table 4, those having a dot density of 10% or 50%) are shown as overprinted colors. Therefore, the specified halftone dot% value for color tone adjustment can be easily specified in the same chart, and Table 4 shows the specified halftone dot% value. Needless to say, it is possible to consider whether the color specified by the halftone dot value described above can be faithfully reproduced on the color plate image without causing deterioration of gradation. , The purpose of this experiment.

[0082]

[Table 4]

Table 5 below shows the plate-making design material for this experiment prepared based on the material of Table 4 above. (Note 1) In this experiment, it goes without saying that the designated halftone dot% value for M ₁ point is the designated halftone dot% value for color tone adjustment in Table 4. (Note 2) In Experiment A of this experiment, the halftone dot% value for the M / Y plate of the S part was obtained by the following equation (2). For the C version,
The value (95%) in Table 2 (standard value for maintaining gray balance) was adopted. In addition, the standard halftone dot% value of the following formula (2) is shown in Table 2. In addition, if the calculation result by the following formula (2) exceeds the standard halftone dot% value, the standard halftone dot% value is adopted. Halftone dot% value of S portion = (standard halftone dot% value of S portion) × (M ₁
Specified dot percentage value) / (standard dot% value of M ₁₎ to .........
(2) (Note 3) Since the catch light part is selected as the H part of the color original image (pot), the halftone dot% value of the H part of all color plate images is "0" (zero). (Note 4) The BL version (black) version is a skeleton type, that is, the starting point (SP) of black ink is M
_One point was set, and the end point (EP) was set as the S section. In addition, the maximum halftone dot% value of the BL plate put in the S part is 8 in Experiment A.
0% and 70% in Experiment B.

[0084]

[Table 5]

The results of the applied experiment were all as expected, as in the basic experiment. The color tone at the color tone management point (M ₁ ) obtained in the color print image is completely in agreement with the color tone on the color chart as the basic scale, and the gradation is not limited to the entire dynamic range of the H part to the S part. The color tone was also natural to human eyes. That is, based on the results of the above-mentioned applied experiments, the color separation technique using the <tone conversion formula> of the present invention as a tool further integrates the tone adjustment and the tone adjustment when performing the tone adjustment management. Above, it was confirmed to have rationality.

<Practical Application Experiment> In this practical application experiment, recently, a print designer or the like uses a standard color original image, and the finish tone of a color print image that is intentionally reproduced is entirely blue or dark green. Considering that the number of operations for changing tones such as tones, light green tones, pink tones, and sepia tones is increasing, and in changing the tone of the above-mentioned image as a whole, in the prior art, it is completely empirical. In view of the current situation that a plurality of complicated work processes based on skill have to be performed, the effectiveness of the gradation and color tone management adjustment method of the present invention for these works was tested. That is, by applying the gradation and color tone management adjustment method of the present invention, it is possible to change the color tone of the image as a whole and to confirm whether or not the gradation of the image can be reasonably managed. And

The color original image for the experiment is 4 "manufactured by Company F, which is recognized as a standard color original in the industry.
A transparent color original of 5 × 5 ″ size was selected. Specifically, as standard color original images, red, blue,
A young female figure with a variety of colors such as green, yellow, and purple and several types of belts (metal, cloth, paper, etc.) were selected.
On the other hand, an experiment was simultaneously performed on a 4 ″ × 5 ″ transmissive target manufactured by AGFA (a color original image created according to the ISO standard), which is widely used as a reference target in the art.

The final color tone of the reproduced color print image is changed to the blue tone. Specifically, on page 29 of the DIC GRAF-G color chart, C version 50%, M version 30%, Y version 10%, and BL
It was decided to manage the color tone with the designated color of 30% of the plate. In addition,
The equipment and materials used in this experiment are the same as those described above.

Table 6 below shows the plate making design material for this experiment.
Further, Table 7 shows the color curve setting data for C plate. In preparing the plate-making design material of Table 6, the following points were taken into consideration while referring to the result of the <applied experiment>. The image that the BL version has in order to give a strong finish to the blue tone of the entire image while naturally suppressing the colors such as red, gray, green, yellow, and purple in the color original image. Consideration was given to making full use of expressive ability and effects. For this reason, the SP (start point) of the BL version is determined to be the part where the halftone dot value of the C version is 10%, the management point (M ₁ ) is 10%, and the maximum halftone dot value of the S part is 95%. %. In addition, for setting the BL plate color separation curve γ
The value, that is, the γ value of <gradation conversion formula> was set to 0.10.

[0090]

[Table 6]

[0091]

[Table 7]

As a result of the experiment, a color print image was obtained as planned in the plate-making design for both the color tone and gradation of the image. That is, in the image of the young woman in the color original image, the finish tone of the entire image visually perceived was a blue color tone and was extremely natural. And, while the overall color tone of the female figure is blue, the delicate gradation of the original flesh color was sufficient to keep the original flesh color even under the blue tone. If the above experimental results are described in more detail, the color tone from the H part to the halftone is the same blue tone as the color tone specified on the color chart, and the magenta (M) color remains in the S part region. It was the one. This is because, as is clear from the plate-making design data (data) in Table 6, many halftone dot% values were designated (68%) in the S part of the M plate, and the experimental results are exactly the same. Met. Also red,
Colors such as green, yellow, and purple were also softly held down, and the image did not feel unnatural with the overall tone. Furthermore, the entire gradation from H to S is not impaired at all, and the characteristic gradation change of materials such as metal, cloth, and flowers is expressed through the overall blue tone. Therefore, these materials could be clearly identified and their details were well reproduced.

Further, the blue color print image obtained from the standard target of AGFA also had rich gradation despite the overall blue color image. That is, the blue-tone sensation received from the entire image was as natural and harmonious as when viewing a natural scene through a blue filter. This demonstrates that gradation conversion was reasonably performed even in the overall color tone conversion process.

Another embodiment of the color scanner of the present invention will be described below with reference to the drawings. FIG. 4 is a block diagram of the color scanner of the second embodiment of the present invention. In the color scanner of the second embodiment, the conventional inverse log conversion unit (15) is used as it is, and therefore the gradation conversion unit (11) has ce ', me', and ye in the form of logarithm (log). ′, Ke ′ is output. Thus, the color scanner of the present invention can be realized by modifying one component (gradation conversion unit) of the conventional (11) color scanner so as to have the function of the gradation conversion unit (11) of the present invention. .

FIG. 5 is a block diagram of a color scanner according to the third embodiment of the present invention. In a third embodiment,
Conventional gradation control (IMC) section (1
6) is left as it is, and the connection between the inverse log conversion unit 15 and the gradation control unit (16) is cut off. As in the second embodiment, a gradation conversion unit (11) that outputs ce ', me', ye ', ke' in the form of logarithm (log) is adopted. The gradation conversion unit (11) is provided with C, from the preceding stage of the gradation control unit (16).
The signals are taken as M, Y, and K, and the value after gradation conversion is output to the inverse log converter (15).

FIG. 6 is a block diagram of a color scanner according to the fourth embodiment of the present invention. In the fourth embodiment,
The conventional inverse log conversion unit (15) and the color channel selector (12) are connected to each other, and the gradation conversion unit (11)
From the front of the gradation control section (16) to C,
The M, Y and K signals are taken and ce ', me', ye 'and ke' are directly applied to the color channel selector (12) in the gradation conversion unit of the first embodiment without being restricted by the conventional system. Ce ', me with the same optimal processing mode
It is possible to obtain ′, ye ′, ke ′. As with the third embodiment, the color scanner of the present invention can be constructed by a slight modification of the conventional system.

FIG. 7 is a block diagram of a color scanner of the fifth embodiment of the present invention. In the fifth embodiment,
The entire conventional gradation adjusting unit (3) is replaced with a new gradation converting unit (1
1), the gradation conversion unit (11) integrates both gradation and color tone based on the <gradation conversion formula> of the present invention to perform color separation. In this way, by modifying the entire conventional gradation adjusting unit, integration and fusion with other image systems can be performed smoothly, and the processing of image information can be speeded up or the device can be made compact. Also, the performance per system can be improved.

[0098]

The color scanner of the present invention is capable of performing color separation by integrating both the gradation and the color tone by using the specific <gradation conversion formula> in the gradation conversion unit which is the core component of the color scanner. Is. The fact that the adjustment of gradation and color tone can be integrated quantitatively and rationally was difficult in the prior art, and is a breakthrough point of the present invention. In the prior art, when trying to answer the needs of the color tone adjustment (color tone correction, change) of specific parts, specific portions, and even the entire image that have high market needs (high demand), the color tone adjustment is quantitative. In addition, it is impossible to produce a high-quality color duplicate image because the color tone of the part concerned and other parts are unbalanced and the tone of image combination (gradation and color tone) is distorted. It is the current situation.

On the other hand, the color separation (gradation conversion) technique incorporated in the heart of the color scanner of the present invention adjusts the gradation by adopting a specific <gradation conversion formula> and operating it. And color tone adjustment can be completely quantified, color original images can be color-separated for the purpose, and high-quality color print images with color tone adjusted as well as gradation reproducibility can be efficiently produced. can do.

That is, the color scanner of the present invention has the following excellent effects. (1). It can rationally meet the needs for quality of color printed images in the advanced, complicated and diversified markets. (2). Production of color print images, especially color separation work is quantitative,
Since it is practiced rationally, it has a remarkable effect on productivity improvement, work time reduction, efficient use of equipment, consumable material saving, reduction, and so on. (3). It is possible to pave the way to make the most of sensibilities and artistry in the production of color print images. These enable the sensitivity and the artistry to be combined with the industrial production system required in the printing industry and the like, and can contribute to the activation of the image-related industry such as the printing industry.

[Brief description of drawings]

FIG. 1 is a diagram showing a density characteristic curve of a color film (manufactured by Company F).

FIG. 2 is a block diagram of the color scanner according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an outline of a basic experiment of the present invention and a color separation curve used.

FIG. 4 is a block diagram of a color scanner according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a color scanner according to a third embodiment of the present invention.

FIG. 6 is a block diagram of a color scanner according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a color scanner according to a fifth embodiment of the present invention.

[Explanation of symbols]

 1 Detecting unit 2 ...... Color separation unit 3 ………… Gradation adjusting unit 11 ………… Gradation converting unit 4 ………… Output unit 5 ………… Color original image

Claims (7)

[Claims] 1. A color scanner for producing a printing plate for producing a halftone dot color print image by subjecting image information of a continuous tone color original image to tone conversion by a tone conversion unit of a color scanner. The gradation conversion unit is (1). Characteristic curve of a recording medium on which a color original image is recorded [a light amount value (x value) incident on the recording medium and a density value (D) formed on the recording medium. The characteristic curve that defines the relationship with the value) in the Dx orthogonal coordinate system] is used to obtain the light quantity value (x value) from the density value (D value), (2). ) Is gradation-converted using the following <gradation conversion formula> to obtain a halftone dot% value (y value), and (3). Then, the color tone adjusting function is provided in (3) -1. Management point (M
₁ ) is set, and (3) -2. Color tone management point (M ₁ )
In the case of the color tone adjustment conditions, the desired color plate (C plate, M
Plate, Y plate, and BL plate), and is defined by the halftone dot% value, (3) -3.
The light amount value at the color tone management point (M ₁ ) and the halftone dot% value of the color plate reflecting the adjustment condition of the color tone, and the H part and S
The desired halftone dot value to be set in the area is substituted into the following <gradation conversion formula> to determine the γ value, and the light amount value of the pixels from the H portion to the S portion of the color plate is converted into the halftone dot value. Each of the pixels for each color plate is prepared by using the <gradation conversion formula> for each color plate for which the <gradation conversion formula> for tone conversion is prepared and (3) -4. A color scanner comprising: a color tone adjustment function configured to perform tone conversion of the light amount value of and to manage and adjust color tone. <Gradation conversion formula> y _n = y _H + [α (1-10 ^−kx ) (y _S −y _H ) /
(Α-β)] In the above item <tonal conversion formula>, the meaning of each symbol are as follows; x: shows the (x _n -x _H). That is, a color original obtained in the same manner from the light quantity value (x _n ) corresponding to the density value (D _n ) of an arbitrary pixel point (n point) of the color original image obtained using the characteristic curve of the recording medium. The basic light amount value obtained by subtracting the light amount value (x _H ) corresponding to the density value (D _H ) of the H portion of the image is shown. y _n : Halftone dot% value set to a pixel on the color print image corresponding to an arbitrary pixel point (n point) on the color original image. y _H : Halftone dot% value preset in the H portion of the color print image corresponding to the H portion of the color original image. y _S : Halftone dot% value preset for the S portion on the color print image corresponding to the S portion on the color original image. α: Surface reflectance of an image expression medium for recording a color print image. β: Numerical value determined by β = 10 ^−γ . k: Numerical value determined by k = γ / (x _S −x _H ). However, x _S represents a light amount value (x _S ) corresponding to the density value (D _S ) of the S portion of the color original image obtained by using the characteristic curve of the recording medium. γ: arbitrary coefficient. 2. The color scanner according to claim 1, wherein the color original image is a color film (transmissive) original image. 3. The color scanner according to claim 1, wherein the color original image is a color print (reflection type) original image. 4. The characteristic curve of a color print (reflection type) original image is defined by a relationship of a density value (D value) and a light quantity value (x value) of 1: 1. Color scanner. 5. The color according to claim 1, wherein the adjustment of the color tone is carried out by fixing the halftone dot value of the Y plate and the BL (black) plate and using the halftone dot value of the C plate and the M plate. Scanner. 6. The color tone management point (M ₁ ) is x _S −x.
_H = 1.0 (normalized light amount value range), y _H = 0
%, Y _S = 95%, γ = 0.45. In the gradation conversion curve for C plate (color separation curve) determined under the initial conditions, the halftone dot value is set to 50%. The color scanner according to claim 1, which is a color scanner. 7. The color tone management point (M ₁ ) is M ₁ =
The color scanner according to claim 6, wherein the color scanner is set at a portion of 0.400 (light amount value).