JPH03220869A - Control method for gradation in manufacture of copy picture - Google Patents

Abstract

PURPOSE:To obtain an excellent print picture having a picture characteristic with fidelity by setting a gradation characteristic curve based on picture information in correlation to a luminous quantity made incident from a picture element corresponding to an object being an original picture into a recording medium and from the relation of gradation intensity such as a dot area X. CONSTITUTION:Density information (Dn value) of an original picture (medium picture) is not used as a basis but picture information given from an object (real picture, real scene), that is, picture information (Xn value) in correlation to a luminous quantity expressed in X axis is used as a basic data. A value Y corresponding to each picture element, that is, a dot area % is obtained by using an equation (gradation conversion equation) based on the Xn value of each picture element of the original picture (medium picture). Then the gradation characteristic curve is obtained by plotting Y values corresponding to the Xn values in the orthogonal coordinate system whose X axis is the Xn value and whose Y axis is the Y.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention J (Industrial Field of Application) The present invention is directed to document images C and below stored and recorded on various recording media such as photographic light-sensitive materials, photoelectric materials, and photoconductors. , also called a media image. ) to hard images such as printed images and digitally copied images, and soft images such as CRT (video) images (transient display images caused by light), which are essential when creating correlations with various logarithms. Concerning gradation management methods.

More specifically, tone conversion is extremely important in creating a correlation between a continuous tone original image and a printed image such as halftone tone. The aim is to manage conversion work rationally and scientifically using an extremely novel method.

That is, the present invention uses density information values (in the present invention, this term is interpreted in the broadest sense) of a document image (medium image) recorded on a conventional predetermined recording medium when creating correlations with various logarithms. The image gradation management technology that emphasizes the gradation of the image (meaning all physical quantities correlated with density) is applied to the subject (which forms the basis of the original image (media image)).
Hereinafter, it is also referred to as a real image or a real scene. ), the present invention relates to a new image gradation management technique that emphasizes image information values that are correlated with the amount of light incident on a predetermined recording medium system.

Separately, the present invention replaces the conventional image gradation management technology that emphasizes the image information of the original image (media image) with emphasis on the image information of the subject (substantive image) that is the true target of reproduction. This relates to a completely new image gradation management technology. In addition, in the present invention, gradation management means
It is applied when trying to reproduce the gradation of the original image correctly and appropriately in correlation with the logarithm, or when trying to obtain the desired gradation (including correcting or changing the gradation of the original image). It is a management technology that

(Prior art and its problems) As is well known, various reproduction techniques are used to convert continuous-tone original images into printed images, correlations with logarithms, printer images, and even correlations with logarithms such as TV (video) images. Note that in the present invention, the correlation with logarithms should be interpreted in the broadest sense as described above. In creating the correlation with these logarithms, the density gradation (gra
It is an extremely important issue to more faithfully reproduce work regularity based on the correlation between dation and tone (tone) and logarithm.However, despite recent advances in reproduction technology, it is difficult to achieve the above-mentioned reproducibility. The current situation is that it is not possible to perform work regularly, rationally, and efficiently.

This is a technology that faithfully reproduces the tone (gradation and color tone) of the continuous tone image of the original image described above based on the correlation with logarithms, and furthermore, it is a technology that allows the tone of the original image to be arbitrarily adjusted to a desired tone (arbitrary Non-linear transformation processing technology (correction or change) in the density domain of the image is the basis of the technology.
Hereinafter, this will be referred to as an image gradation conversion technique or an image gradation conversion method. ), it originates from the fact that it is unscientific and irrational, relying entirely on human experience and intuition, with no rational theory to back it up.

This will be explained by citing print image production technology as a representative and specific technical field.

In the conventional technology, when producing a color print image that is correlated with logarithm from a color film original (approximately 90% of color originals are transmissive), it is necessary to print from the brightest part to the darkest part of the original image. Furthermore, there is no effort to rationally grasp the density characteristics that lead to the color separation curve, which determines the correlation between the gradations of the continuous tone original image and the halftone printed image. It can be said that the establishment of the characteristic curve (also called a characteristic curve, halftone characteristic curve, etc.) depends entirely on human experience and intuition.

Generally, to produce a color printed image, a color original image is separated into colors using a color scanner, and then multicolor plate making (generally C plate, 9M plate, Y plate, and double plate) is performed to produce a printed image with halftone gradation. be duplicated.

These color scanners and total scanners are mechatronic and extremely expensive devices, but one of the major problems in this industry is that their action rate is approximately 30% on average.
%, which is an extremely low level. The reason for this low operating rate is the setup time required to operate the color scanner.
The etup time is long, and the quality of the product obtained by the color separation process is unstable and insufficient, resulting in a large number of rescans.

Considering this from a technical perspective, as mentioned above, although advanced mechatronic color scanners are used as tools for color separation work, multiple elemental technologies for color separation work, such as Color correction (correction) fco
lor Correction) technology and density gradation (G
conversion techniques (radiation) have not been systematically organized in a consistent manner, and this is the cause of poor tone reproduction and low availability of color scanners. As is well known, of the two elemental technologies mentioned above, the color correction (correction) technology has been pursued in an extremely rigorous scientific manner, such as the masking equation and the Neugebauer equation; The technology (this comes down to the problem of what size halftone dot should correspond to a given pixel in a color original image) has been left unresolved without any rational theoretical support. This part is highly dependent on human experience and intuition.

Color separation equipment has not been developed under these conditions, and in addition to the fact that the basic design technology of the equipment itself is still immature, it is difficult to use expensive and sophisticated electronic color separation equipment in actual work. Eliminate operator guesswork, operator experience and intuition while using
perator evaluation, with
ut operator's guess workl
Therefore, it is not possible to always produce printed images of stable quality. In particular, a serious problem arises when the color original image is not a so-called standard image created under appropriate photographing and exposure conditions and appropriate development conditions. In other words, it is not possible to reasonably perform color separation work on these non-standard color original images, resulting in insufficient gradation reproduction, low scanner availability, unstable product quality, and rescanning. There are problems such as an increase in the ratio of

(Problems to be Solved by the Invention) The present inventors have established a rational theory for image gradation conversion technology, and have determined the tone (
In order to have good reproducibility (gradation and color tone) and to go even further and rationally create a correlation with logarithms that have the desired tone, it is necessary to Conversion of gradation (changing the size of dots such as halftone dots by means of variable area dots, changing the arrangement of specified dots by means of constant dots, or changing the density of the pixel itself by means of variable density dots) , it is well known that pixel density gradations can be reproduced in correlation with logarithms.) We believe that emphasis must be placed on technology that can rationally perform this. This can be seen in the production of color printed images, etc.
This is a call for reflection on the conventional technology that emphasizes color correction (correction) technology, which is relatively easy to scientifically analyze, over image density gradation conversion technology when creating correlations with logarithms. be.

The present inventors have discovered that the current image density gradation conversion technology used to create a correlation with a logarithm from a manuscript image, as described above, can be used to create a print image that is a correlation with a manuscript image, for example, a logarithm. The density characteristics of color film originals from the brightest part to the darkest part are not reasonably understood, and the density characteristics of the original image are converted into a logarithmic correlation with a fidelity of l = 1. There is no rational theory to determine the correlation (gradation conversion formula) between the two images (the correlation between the original image and the logarithm), which is essential for the process. We have a basic understanding that we still rely on intuition.

Based on this basic recognition, the present inventors previously proposed a specific tone conversion formula in order to make the image tone conversion technology scientific and rational (Japanese Patent Application Laid-Open No. 64-7770
Publication No. 114599, Japanese Patent Application No. 114599, Japanese Patent Application No. 63-2
No. 07326, U.S. Patent No. 4,! No. 311,108).

However, in subsequent research by the present inventors, it was discovered that there are certain limitations to the image tone conversion technique performed under the above-mentioned specific tone conversion formula.

This limitation is that the true target of the correlation with the logarithm should be the subject (substantive image), but in the conventional technology including the previous proposal of the present inventors, This means that image gradation conversion is performed using the density information value of the accumulated or recorded original image (medium image) as a clue.

For example, in the production of color printed images, in the conventional technology, light incident from the subject is set under predetermined exposure conditions (as is well known, when the intensity of the incident light is I and the incident time is t, the exposure amount E is E=It), color separation work is performed based on density information values of a photographic image, which is a medium image recorded on a photographic light-sensitive material.

As is well known, photographic light-sensitive materials on which subjects have been photographed have a photographic density (photographic density) that is obtained by development.
ityl is formed, and this becomes the original image (medium image). The curve representing the correlation between the photographic density (degree of blackening) and the exposure amount E of the photographic light-sensitive material described above is the relationship between the photographic density characteristics.
It is a cteristic curve. This represents the photographic density (DI fD = log'9' 11
, the logarithm of the fog light LtE is plotted on the horizontal axis. In addition, for film and dry plates (transparent originals), the ratio of the intensity of transmitted light I to the intensity of incident light Io, and for photographic paper (reflective originals), the ratio of the intensity of reflected light I to the intensity of completely reflected light Io It goes without saying that the ratio of

A typical photographic density characteristic curve (hereinafter simply referred to as a density characteristic curve) is a complex curve (hereinafter simply referred to as a density characteristic curve) that has a downwardly convex leg, an approximately straight line, and an upwardly convex shoulder. The point is
Please refer to FIG. 1 and FIG. 4, which will be described later. ).

In other words, as is clear from the density characteristic curve, the conventional technology is a color separation technique that uses the image information value read from the vertical axis (density value) of the density characteristic curve, that is, the density information value. .

The density information value of the color original image, which is the basis of the color separation work in the conventional technology, is the subject (
These media have no proportional relationship, and moreover, the image information possessed by the subject The aspect of weight separation of these media varies greatly depending on exposure conditions, development conditions, etc.

In other words, the photographic density, which is the image information value of the color original image, which is the medium image, is affected by the photosensitive characteristics of the photographic material, which is the recording medium.
It is not possible to correlate the exposure amount (logarithmic value), which is the image information value incident on the photographic emulsion layer from 1 to 3, with a linear relationship (for example, a 45° linear relationship of 1:1).

On the other hand, it is well known that human vision has a logarithmic discrimination characteristic for brightness and darkness, and humans can determine the amount of light that enters the visual system from an object (real image, real scene) based on the discrimination characteristic described above. I am evaluating its brightness and darkness. In the real world, where the subject is actually evaluated visually, a linear gradient of density change is perceived as natural.

As described above, in the production of color printed images, the density value (
D = log'9'I), it means that we are using the density information value after being influenced by the characteristics of the photographic material, and the true object of reproduction is the subject ( This does not mean that the image information value (logarithm of the exposure amount) obtained from the actual image, image, or actual scene is used. That is, when a printed image is produced using the density information value of the original image (medium image) as a clue, the image information called the amount of exposure incident from the subject that forms the source of the original image, and the density information value of the medium become more and more It is recognized that faithful reproducibility becomes difficult.

As is well known, a document image (media image) is a predetermined image that is incident from a subject (a real image, a real scene) onto a recording medium (photosensitive round material for photography, a photoconductor such as a CCD, a photoconductor, etc.) having various photosensitive characteristics. It is formed based on the exposure amount. In the gradation conversion technology of the present invention, it has been confirmed that the exposure amount can be used for both absolute and relative media. Image information values related to the amount of exposure will be referred to as image information correlated to the amount of light.

In view of the above-mentioned situation, the present inventors aimed to utilize the image information value correlated with the amount of light from the subject in the production of printed images.
The first image obtained from the subject (real image, real scene) without using the image information of the original image (media image) affected (e.g. non-linearly modified) by the photosensitive properties of
We have conducted extensive research into methods for producing printed images based on image information values that are correlated to the amount of light, such as the following (raw, primitive) exposure amount.

As a result, when producing a printed image, the vertical axis (D =
The value of the horizontal axis (logE) is calculated from the value of IogI9'H) (hereinafter, the vertical axis is also referred to as the D axis, and the horizontal axis is also referred to as the X axis), and if placed separately, the brightest part defined on the concentration characteristic curve The density information value on the D-axis of the color original image (medium image) from the darkest part to the darkest part is projected onto the X-axis. Upper density value (D,)
is projected onto the X-axis via the density characteristic curve to obtain an image information value (Xn) correlated to the light intensity of the corresponding pixel (note that
As a simple method, the image information value xn on the X-axis can be read on a scale in which the X-axis graduation is the same as the D-axis graduation, and in this sense, in the present invention, the value on the X-axis is used as the light amount. Correlated image information is used in these media. However, it goes without saying that the scaling is not limited to this. ), and then (3) the image information value (Xnl) correlated to the light amount of each pixel of the original image (medium image), the coordinate axis (for example, the horizontal axis of an orthogonal coordinate system), and the density information possessed by the halftone dot area % value. value(
In a coordinate system consisting of another coordinate axis (for example, the vertical axis of an orthogonal coordinate system) that displays the Dn value, the Density information value (Dn value (y value)
Set the gradation characteristic curve by displaying the relationship between
(4) When the gradation is managed based on the gradation characteristic curve, an excellent printed image can be obtained that has image characteristics that are faithful to the subject (substantive image, real scene) that is the true object of reproduction. I found out. Note that as a method of displaying the gradation characteristic curve in (3) above, the density information value fDnl of each pixel of the original image (medium image) may be adopted as the horizontal axis, and the coordinate axis that displays the Xn value may also be used. It goes without saying that they may be combined. Based on the above-mentioned new fact, the present invention has revised the conventional production technology of correlation with logarithm that emphasizes the density information value of original image (medium image). This technology aims to provide a completely new method for producing correlations with logarithms that emphasizes the image information value of real scenes (actual scenes), that is, the image information value correlated to the amount of light, and in particular, a completely new method for managing image gradation, which is its core technology. It is.

[Structure of the Invention] (Means for Solving the Problems) To summarize the present invention, the present invention is capable of calculating the logarithm of halftone gradation, etc. from a medium image as an original recorded on a predetermined recording medium. In a method of managing gradation when producing a correlation, (1) a gradation characteristic curve defining the gradation transformation used to produce a logarithmic correlation from a document image (media image) is defined as ( b) Density information value (D
(b) the image information value (Xn value) correlated to the amount of light incident on the recording medium from the corresponding pixel of the subject forming the source of the original image (medium pixel); and (b) the x value. A gradation characteristic curve is set in relation to the density information value (Dn value (y value)) of each pixel obtained by applying the following <gradation conversion formula>, A method of managing gradation when producing a correlation with a logarithm characterized by .

<Gradation conversion formula> Hereinafter, the configuration of the present invention will be explained in detail.

In addition, the method of managing gradation when producing a correlation with a logarithm from a manuscript image (media image) according to the present invention will be explained by referring to a case where a color printed image is produced as a correlation with a logarithm. Make it.

Therefore, this is for convenience of explanation and does not mean that the image gradation management method of the present invention is applied only to the reproduction of color printed images.

As mentioned above, color scanner color separation devices are currently used in extremely large numbers in the reproduction work of color printed images, and the color separation work by this device is performed by color original images (
This is done based on density information values obtained from media images (including transmissive originals and reflective originals). More specifically, as a conventional method, color print images are produced using C, M, Y versions, etc., based on density information values of each color obtained from a color original image (media image) through R, G, and B filters.
A BK (black) version is being produced.

However, this method of utilizing the density information value of a color original image (medium image) recorded on a recording medium called a photographic light-sensitive material has the above-mentioned limitations (defects).

On the other hand, as described above, in the present invention, the true object of duplication is not the image recorded on the recording medium, but the subject itself (substantive image, real scene), and based on the image information value from the subject. It is based on the idea that it should be done.

The above points are the basic differences between the prior art and the technology of the present invention.

This can be explained from another angle as follows. In color separation technology, it is necessary to convert the density value of the original image into a halftone dot area percentage, but as mentioned above, the correlation between the tones of the continuous tone original image and the halftone print image is specified. This is the gradation characteristic curve, that is, the color separation curve (hereinafter referred to as −
The term color separation curve used in M is used.

). The conventional color separation curve is set based on the density information value of the original image (medium image) on the D axis (vertical axis of the photographic density characteristic curve). On the other hand, in the present invention, as described above, the setting is performed based on the image information value correlated to the light amount of the subject (substantive image) on the X axis. That is, in the conventional color separation technology, the D-axis separation curve (see Fig. 3, which will be described later),
The two are basically different in that the present invention uses an X-axis decomposition curve (see FIGS. 2 and 5, which will be described later).

Next, the image gradation management method of the present invention will be explained in detail for each step for setting the above-mentioned gradation characteristic curve with reference to charts.

fi1 In the present invention, first, an image information value related to the density of a color original image (medium image), specifically a density value (
D = log'9'■) to the image information value that correlates to the amount of light that enters the photographic photosensitive material that is the recording medium from the subject (substantive image), specifically, the logarithm of the exposure amount (E = I t) must be sought. For this purpose, a concentration characteristic curve may be used. In order to reasonably determine the xn value from the Dn value using the concentration characteristic curve, the concentration characteristic curve must be converted into a function. This can be done, for example, by converting various density characteristic curves provided as technical data from photosensitive material manufacturers into functions. If it can be rationally converted into a function, the Dn value on the D axis can be easily converted to the x0 value on the X axis.

The concentration characteristic curves used in the experiments of the present invention are shown in FIG. 1 (manufactured by Company F, Fujichrome) and FIG. 4 (this was arbitrarily created by the inventors). The image shown in FIG. 4 was arbitrarily created by the inventors in order to verify whether the image gradation management method of the present invention has generality, reliability, and elasticity. As will be demonstrated by the examples described later, in the present invention, even if a color film having a density characteristic curve different from that shown in FIG. 1, which is commercially available from a photosensitive material manufacturer, is used, exactly the same results can be obtained. can. It has also been confirmed that the present invention is not subject to any limitations on the shape of the concentration characteristic curve.

Next, a method of formulating the concentration characteristic curves shown in FIGS. 1 and 4 will be explained.

The concentration characteristic curve may be expressed mathematically by any appropriate method, and is not subject to any restrictions.

For example, vertical axis = D = lOgI9/I, D axis = X (however,
The scale of the X axis was made to match the D axis. )
Then, if a + b + C and d + f are constants, then (a) The leg part of the concentration characteristic curve (the region with a downwardly convex shape and a small D value) D = a, b ``'''' + e 10 f (B) Approximately straight part (approximately straight part, area where D value is intermediate value) D=a-x+b or D=a-x2+bx+C (c) Shoulder part (upwardly convex part, D (area where the value is large) D = a - 1og (b + (X + cl ) + d).

Table 1 shows the contents of the concentration characteristic curves shown in FIGS. 1 and 4 expressed in mathematical formulas. In Table 1, in order to mathematically express the concentration characteristic curve as accurately as possible, there are a plurality of mathematical expression categories.

(Margin below) <Table 1> In the present invention, as shown in FIGS. 1 and 4, the D-axis scale indicating the density value of the color original image (medium image) and the subject (substantive image) are used. D and X were converted into numerical numbers on the assumption that the scale of the X axis indicating the image information value indicated by logE is the same.

This is a kind of relativization (fiction) performed from the following viewpoint, and the inventors believe it to be reasonable.

That is, originally in the density characteristic curve, the exposure H is on the X axis.
The logarithm value of E (logE = logIxtl) is considered to be that the visual discrimination characteristic of brightness and darkness is logarithmic.As will be shown in the example described later, under this relativization (simulation), even in the image Excellent results can be obtained in gradation conversion.It should be noted that the above-mentioned graduation in the present invention is a kind of simple method, and it goes without saying that the present invention is not limited to this.

(il) As described above, the present invention is not based on the density information value (Dn value) of the original image (medium image), but is based on the image information value given by the subject (substantive image, real scene), that is, the X-axis Image information value (Xn value) correlated to the amount of light expressed by
It is based on

As mentioned above, as shown in Table 1, the density characteristic curves of Dn and Xn of these media are correlated by the functional expression X = f fDl, so it is easy to do this. value to X
The n value can be determined.

In the manner described above, it is possible to obtain image information values that correlate with the amount of light incident on the photosensitive emulsion layer from the subject (substantive image). Next, the x, value at each pixel of the original image (medium image) reasonably determined in this way is used to calculate the y value corresponding to each pixel using the <gradation conversion formula>.
The value, that is, the halftone dot area % value is determined. Then, when the y values corresponding to the Xn media are plotted on the orthogonal coordinate system of the X axis (horizontal axis) that displays the Xn value and the vertical axis that displays the y value, the gradation characteristic curve, that is, the conventional D axis output An X-axis decomposition curve is obtained instead of the decomposition curve.

1iv1 or more, a gradation characteristic curve that controls gradation conversion, which is extremely important in producing a printed image from an original image (medium image), is set rationally.

As demonstrated in the Examples described below, the Xn of the present invention
In utilizing the gradation characteristic curve created by the gradation conversion formula of the present invention for these media, the gradation conversion formula of the present invention is subject to certain conditions, namely a+ yH+ ys+ γ
The gradation characteristic curve obtained by keeping the values constant is based on the image quality of the original image (i.e., the density range and density information (a) of each original).
) even if the printed image changes from H to 8 in the final product, the printed image.
One line that shows the arrangement of the halftone area % values up to the section (
There is a unique gradation chronological curve. (As shown in the examples below,
Even if the X-axis radii of each document are different, they will become one if they are adjusted to the predetermined X-axis radial). On the other hand, in the D-axis decomposition curve, curves corresponding to each image quality are obtained, so it is unclear whether or not the predetermined gradation conversion has been performed unless each is printed as a proof.

fblIn relation to the above point, due to the nature of the gradation conversion formula of the present invention, by arbitrarily changing the α+ yH+ ys+ γ value (particularly by changing the γ value), the gradation characteristic curve can be rationally created. In other words, the operator who manages the gradation conversion work can adjust (correct, change) the gradation of the printed image as desired.

This is an extremely important characteristic, and the gradation conversion work can be rationally managed based on the gradation characteristic curve.

Note that in order to reproduce a printed image using a predetermined gradation characteristic curve (X-axis separation curve), the color scanner's A desired screen may be formed using a dot generator.

Next, the process of deriving the above-mentioned gradation conversion formula of the present invention is as follows:
I will briefly explain it here.

The gradation conversion formula for calculating the halftone area percentage value (yl) used when producing a printed image, which is the halftone gradation mentioned above, is based on the generally recognized density formula (photographic density, optical density), namely D = logI9 '1 = log J/ T1o
=Amount of incident light ■ =Amount of reflected light or transmitted light T = I/Io = Derived from reflectance or transmittance.

When this general formula regarding density is applied to plate making and printing, it becomes as follows.

Here, A: unit area do: area of each halftone dot within the unit area a: reflectance of printing paper β: surface reflectance of printing ink.

The present invention is based on the density formula (D') related to plate making and printing, and calculates the base &2a degree value fxl at any sample point (pixel) on a continuous tone original image and the corresponding halftone gradation. The gradation conversion formula was derived so that the relationship between the value (yl) of the halftone dot area percentage of the halftone dot at the sample point on the printed image matches the theoretical value and the measured value of the medium.

In the operation of the above-mentioned gradation conversion formula of the present invention, in the case of duplicating a printed image, etc., the parameters of:
+ 95% 9M to ys and 3% to yH in Y version, yg
A dot area percentage of 90% is used. - In addition, when operating the above <gradation conversion formula>, if the densitometer measurement value (basic, E degree value) is used for the density value, and the percentage value is used for y, 4, and ys, the y value is also calculated as a percentage value. be done.

The numerical settings of the parameters of the gradation conversion formula of the present invention are as follows:
This differs depending on whether one is trying to faithfully reproduce the tone of a given subject (substantive image) in a printed image, or the other is trying to produce a printed image with the tone consciously adjusted (corrected or changed). In the latter case, Q * 3'H1
By consciously changing the y8+ γ value, it is possible to change the shape of the X-axis decomposition curve to the desired shape, so the operator who manages the gradation conversion work can create printed images with various tones for the desired purpose. can be produced.

In addition, multicolor plate making (generally 0 plate, 9M plate, Y plate).

K (%) plates of intaglio plates are considered to be one set. ) in order to apply the above-mentioned <gradation conversion formula> of the present invention and set respective X-axis decomposition curves, the following may be done. The above-mentioned <gradation conversion formula> is derived from the viewpoint of rationally determining the C plate, which is the most important plate among multicolor plate making. Therefore, what is derived by applying the above-mentioned <gradation conversion formula> is the X-axis decomposition curve for the C version, and for other M versions,
The X-axis resolution curve for the Y plate may be determined by multiplying by appropriate adjustment values well known in the art so as to maintain gray balance and color balance. Further, the X-axis decomposition curve for K (black) may be determined according to a conventional method in the art from the viewpoint of reducing the consumption of C, M, and Y inks.

In the operation of the above-mentioned gradation conversion formula of the present invention, it is not only possible to use it by transforming it into a linear shape, but also to use it by arbitrary processing, transformation, guidance, etc.

3' = V H+ E (1-10-”x] ・ly
s-yol In the above modification, α=1.

This is based on the surface reflectance of printing paper (base material) used to express a printed image as 100%, for example. These media for α can take any value, but in practice it may be set to 1.0. This also applies to brightness images such as video images.

Furthermore, according to the modification (a=1.0), it is possible to set yH in the brightest part 11 on the printed image and y3 in the darkest part S as planned, which is a big advantage in the present invention. It is characteristic. This means that in the brightest part H on the printed image, X=O according to the formula, and h4
In the dark area S)<=x5. It is clear from the fact that -xHn, that is, . In this way, when using the gradation conversion formula (modified example of a=1) of the present invention, it is possible to always set y, I, and y3 as planned on the printed image. This is extremely important for those who consider the results of their work. For example, y in a printed image. By setting desired values for and y3 and changing the γ value (a=1.0), various X-axis position resolution cubes can be obtained. Then, the origin of these X-axis resolution cubes (4) can be easily evaluated in terms of the relationship between γ and these media.

Furthermore, the above-mentioned gradation conversion formula of the present invention is extremely useful for reproducing the gradation and color tone of a subject (substantive image), that is, for reproducing the tone of the subject in a printed image with regularity in l:I. However, its usefulness is not limited to this. In addition to the faithful reproducibility of the image characteristics of the subject, the above-mentioned gradation conversion formula of the present invention also provides a
,: This is extremely useful for rationally changing or correcting the image characteristics of a subject by appropriately selecting the y'g value.

Note that among the parameters mentioned above, the particularly important one is γ
By changing the γ value, the shape of the X-axis decomposition curve can be changed greatly and arbitrarily, so it is possible to obtain an X-axis decomposition curve that provides the desired image quality.

As described above, in the production of color printed images, the present invention performs the extremely important gradation conversion work by correlating the light intensity of the subject (substantive image) instead of using the density information value fDn of the original image (media image). Between the gradation characteristics set by using the image information value (Xo) and using the above-mentioned <gradation conversion formula>! ! (X-axis resolution curve), and can produce images that are faithful to the subject (real image, real scene) or color printed images with the desired image quality with work regularity, universality, and elasticity. It is written by making it with.

Next, other features of the image gradation management method of the present invention will be explained.

The image gradation management method of the present invention is not only applied to the production of color printed images as described above;
As will be described later, its application range is extremely wide. That is, light;
The present invention can be applied to all fields in which output information of a reproduced image is obtained by processing image information values obtained by photographing or capturing and converting image information of a physical image using information transmission media such as electromagnetic waves.

Therefore, it goes without saying that the image gradation management method must be adapted to the system that produces the correlation with each logarithm.

First, in addition to the above-mentioned photosensitive materials, the recording medium on which the original image (medium image) is recorded can be any material that functions as a recording medium, such as a photoelectric material, a photoconductor, an optical disk, or a magnetic disk. It may be.

Next, the original image (
Information related to the density of these media (images on media); Image information related to the amount of light incident on each recording medium from the subject (real image, real scene). The density characteristic curve showing the correlation between these media is:
Photographic density characteristic curve (
The density must be defined as (the combination of the logarithmic values of these media exposures). In the production system of the correlation with each logarithm, the density information of the original image (medium image) recorded on the various recording media mentioned above, and the image information value correlated with the amount of light incident from the media subject. Either is fine. The physical quantities related to the image information values that are correlated to the density information values and the amount of light described above should be understood in the broadest sense.For example, the R words include reflection density, transmission density, brightness, brightness, light M (exposure amount), Frequency, current/
There are voltage values, etc.

Other very important consequences of the invention are as follows. Regarding the various recording media mentioned above, such as CCD (charge-coupled device), research and development has been actively conducted to improve the imaging characteristics of each medium in order to produce a correlation with logarithm of high image quality. For example, if the density characteristic curves of various recording media are reasonably defined, the above-mentioned research and development is not necessarily necessary. In other words, even if the recording medium is of current quality, the present invention can be applied as long as its density characteristic curve (density information, a curve that defines the correlation between image information values correlated with the amount of light from the medium subject) is reasonably defined. By managing the tone transformation, it is possible to produce a logarithmic correlation of excellent image quality.

Although the application aspects of the invention have been described above specifically in relation to the production of printed images, they are not limited to the production of printed images.

That is, the image gradation conversion management method of the present invention can be applied to the production of correlations with various logarithms as shown below and related fields;
Printed images such as lithography, halftone dot gravure, and silk screen, as well as halftone dots (dots) found in melt transfer thermal transfer images and piezoelectric inkjet, which can change the size of the dots (multi-level printing). When trying to express gradations and tones in correlation with logarithms by size (this is also called area gradation method), (iii) sublimation transfer type thermal transfer images, (using silver salt) thermal development transfer images, conventional・When trying to express gradations and tones by the shading of pigments and dyes (pigments) such as printing ink that are deposited per pixel of a certain area (for example, per dot), as seen in gravure images (this is called density N). ), fiiiil Digital copying machine (color copy, etc.)
When trying to express gradation by changing the recording density per fixed area, such as the dot El or the number of ink particles, etc., as seen in printers (ink jet type, bubble jet type, etc.), facsimiles, etc. teeth,
This is similar to the area gradation in (i) above. ), from electric signals related to image information such as fivl video signals, television signals, and high-definition signals, we can obtain CRT images that express images by adjusting the brightness intensity of a unit area, as well as printed materials with gradations and hard copies. In this case, fvl not only the case of image conversion processing between the original image and the logarithmic correlation in the almost equivalent density (luminance, illuminance) region described above, but also spatial, luminance, wavelength, and temporal Photographing in an invisible region, for example, the contrast of the original image is extremely low, so the difference in the density range between the original image and the correlation with the logarithm is small, and the input conversion of image information in the low-light region (c) Imaging with a high-sensitivity camera) (In such cases, emphasis is placed on image contrast enhancement conversion rather than image gradation conversion.); (vi) As precision medical images for examinations such as X-rays, (vii) In addition, a densitometer with a density/gradation conversion mechanism that displays the density and halftone area %, etc., for pre-inspection of color separation (e.g. Color proof for proofreading)・
It can be applied to the production of printing-related equipment such as simulators and color separation education simulators.

In order to apply the gradation management method of the present invention to the various application fields described above, as in the case of producing printed images described above,
You can do as follows.

First, in each field, information related to the intensity information of the original image, image information that correlates to the amount of light incident from the medium subject, and based on Numado characteristics and characteristics that indicate the correlation between these media, the original image (As mentioned above, this includes both hard and soft originals.) Corresponds to the image information value (this may be analog or digital as mentioned above, or may be an electrical signal value) regarding the density of the original. The image information value (X
Find Ji). Next, this is processed under the above-mentioned <gradation conversion formula> in an image conversion processing unit (gradation conversion unit) of equipment for producing correlation with logarithms in various application fields, and the y value (having A gradation characteristic 4! (Xn correlation amount L of these medium y values?!) is created using the density information value (Dn value), and it is used as part of equipment in various application fields to make it easier to control the gradation conversion work. The gradation characteristic curve may be displayed.Thereby, the gradation conversion work when creating the correlation with the logarithm can be managed rationally while interacting with the displayed gradation characteristic curve. can.

As explained in the production of printed images, the gradation characteristic M (X-axis position resolution curve) of the present invention indicates the quality of the final product (the arrangement of halftone dots). Therefore 1
In the gradation conversion work, when controlling the gradation and creating a correlation with the logarithm of the desired image quality, the shape of the gradation characteristic curve can be changed by rationally using the gradation conversion formula of the present invention. All you have to do is change it. As described above, in the operation of the gradation conversion formula of the present invention, a gradation characteristic curve (X-axis position resolution curve) that provides a desired image quality can be obtained by changing the γ value. In various application fields, in order to create a correlation with the logarithm, it is necessary to use the current value or voltage value of the recording section (recording head) of the device, or By controlling the application time, etc., and changing the halftone dot area, the number of dots per fixed area (for example, 1 pixel), and the density per fixed area (for example, 1 dot), the density gradation of the subject (substantive image) is adjusted to l= 1
What is necessary is to output the correlation with the logarithm of the halftone gradation, etc., which is faithfully reproduced.

For example, in order to produce an original plate for a printed image that is a halftone image, that is, a printing original plate, an existing system well known in the industry may be used, and a commercially available electronic color field device (color scanner total) may be used.・The output value of the y value may be used in a color separation/shading mechanism such as a scanner). More specifically, a small spot light is irradiated onto an original image (media image) that is a continuous tone image such as a color photograph, and this reflected or transmitted light (image information signal) is converted into a photoelectric conversion unit (photomultiplier). ), the intensity of the light is converted into the intensity of voltage, the obtained image information electrical signal (voltage value) is organized and processed as required by a computer, and the processed image information electrical signal is output from the computer. The exposure light source light may be controlled based on the (voltage value), and then a laser spot light may be applied to the raw film to create a printing original plate. At that time, the manuscript image (
Organize and organize image information electrical signals correlated to the density of media images)
In the calculation processing unit of the computer for processing, the information value related to the density of the original image (medium image) is adjusted to the image information value correlated to the light intensity of the corresponding object (substance image), and the It is only necessary to install software that can convert image information of halftone gradation into electric signals (y values) using the conversion formula. Such software converts the information value fD,) related to the density of the original image (medium image) under a predetermined density characteristic curve into the image information value IXn) correlated to the light intensity of the subject (substantive image). At the same time, the above-mentioned <gradation conversion formula> algorithm is stored as software, and a general-purpose computer has an A/D (analog-digital conversion) and D/A I/F (interface), and the algorithm is used as logic by a general-purpose IC. Nine different types of electrical circuits can be used, such as an embodied electrical circuit, an electrical circuit containing a ROM that stores algorithm calculation results, a PAL that embodies the algorithm as internal logic, a gate array, and a custom IC. Particularly in recent years, modularization has been developed, and a forward calculation implementation mechanism that can perform gradation conversion of an image in the density domain based on the above-mentioned ``gradation conversion formula'' of the present invention is a dedicated IC, LSI, It can be easily manufactured as a module such as a microprocessor or microcomputer. Then, if the spot light for photoelectric scanning is sequentially divided into points and progressed, and the laser exposure section is also synchronized with this, the value of the halftone area percentage derived from the above-mentioned <gradation conversion formula> A printing original plate having a halftone gradation having (y) can be easily created.

(Example) Hereinafter, the image gradation management method of the present invention will be explained in more detail with reference to an example in which a color print image is reproduced from a color original image, but the present invention is not limited to the example. In the following embodiments, examples of setting color separation curves (gradation characteristic curves), which are indispensable for color printing image duplication work, particularly for controlling the quality of final products, will be explained with emphasis.

(Example 1) 1. Concentration characteristic curve used in the experiment The concentration characteristic curve shown in FIG. 1 (D-X orthogonal coordinate system) (manufactured by Company F, Fujichrome) was used as the concentration characteristic curve. In FIG. 1, the D axis (vertical axis) indicates the density value of the color original image.

On the other hand, the X-axis is the exposure amount fl in a general density characteristic curve.
ogE=logI x tl, which is expressed numerically using the same scaling as the D axis. Further, the functional formula for the concentration characteristic curve used was the one listed in Table 1, 11+.

2. Experimental manuscript image The image quality of color manuscript images varies widely depending on the exposure conditions at the time of photography, such as standard (proper exposure) and non-standard (over/under exposure). It is. In order to verify whether the present invention can be rationally applied to these wide variety of color original images, we investigated the density range (DRI) of color original images.
Experiments were conducted on samples with different values (different concentration ranges on the D axis).

3. Calculation of data for setting the X-axis resolution curve Using the density characteristic curve in Figure 1 and the density characteristic curve function formula in Table 1 11+, calculate the D7 value on the D axis of various color original images on the X axis. It was converted to the X0 value above. Next, use the X1 value as the gradation conversion formula
It was converted into a halftone dot area % value (y value).

Note that the operating conditions for the <gradation conversion formula> are as follows.

x=Xn　−x+411 yH=5%, yg=95%.

γ=1.00. β=IO-0,1, α=1.00=
y/x sn x Hn.

(In the case of Table 2 below +11, XH, = 0.4781X
, , = 2.2300. In other cases, the second
Please refer to the table below. ) The results are shown in Table 2.

In Table 2, ■ to ■ in Table 2 are overexposed images (light original images), ■ to ■ in Table 2 are close to proper exposure, and ■ to [phase] in Table 2 are underexposed images. (a large original image) are shown respectively.

(Margin below) pale color <Table 2> Pig for setting the X-axis decomposition curve for the original (that) <Table 2> For color originals with close to proper exposure Data for setting the X-axis decomposition curve Ta (Part 2) ■ manuscript DR=O.

20~20 ■ Original DR=0 30~2.80 Dark color <Table 2> Data for setting the X-axis decomposition curve for the original (Part 3)
) 4, X Amber color separation curve Table 2 data are shown in FIGS. 2 and 3.

In addition, in FIGS. 2 and 3, the vertical axis indicates the γ value (halftone dot area % value), but it must be noted that the horizontal axis has a different character. The horizontal axis in FIG. 2 shows the image information value correlated to the amount of light, and the horizontal axis in FIG. 3 shows the density of the color film original. In creating the graph, for convenience of comparison, adjusted numerical values (2,5000 in the case of this example) were used as ranges regarding the same light amount and density.

The values after this adjustment are shown in Table 2 (Dn-I Dn, (X
n, -)X'. D n ”D n'
In the case of Table 2 H, the adjustment to 2.52 can be made by calculating 2.50 = (DI, -1,800) X□. Similarly, Xn-Ix,,' is 2,500 X,' = iX, -047811x - 1,75
19 All you have to do is calculate.

FIG. 2 shows the gradation characteristic curve according to the present invention, that is, the X-black color separation curve (as described above, the relationship between Xn and y), and the third
The figure shows a D-axis separation curve (as described above, it shows the relationship between R and y, and can be considered as an example of setting a conventional color separation curve).

As is clear from FIGS. 2 and 3, an extremely surprising fact can be discovered. In other words, no matter what quality of color original image is used, α, y in the <gradation conversion formula>
H.

It is a surprising fact that when the four values of ys + γ values are made the same, the respective X candy color separation curves are combined into one identical curve as shown in Figure 2, and the results obtained after color separation are This is the fact that the tone of a color printed image is displayed uniformly. In other words, the gradation characteristic song of the present invention! According to the I (X-color separation curve) setting technology, no matter what quality of color original image is used, a gradation characteristic curve that can produce a printed image of the same quality with the same array of halftone dots is created. is obtained. In addition, the gradation conversion operator can change the X-ame color separation curve obtained as described above into a desired shape by changing the parameters in the <gradation conversion formula>, especially the γ value. That is, the gradation can be rationally managed based on the above-mentioned X-black color separation curve so as to obtain desired image quality and tone.

In contrast, in the conventional color separation curve setting example shown in FIG. 3, a D-axis separation curve corresponding to the image quality content of each color original image is obtained, and the color printed image obtained after color separation It is not possible to know in advance exactly how things are going. In other words, under the conventional D-axis decomposition curve, it is difficult to determine whether the image quality and tone of the final product, the printed image, is appropriate unless you actually produce a proofing plate and evaluate the proof. It has the disadvantage of not being clear.

This requires setup work in which an appropriate color separation curve must be selected from among a large number of color separation curves during color separation work using a scanner, and grooving work for color originals in the process prior to setup work. It means that. That is, the conventional D-axis decomposition curve setting technique cannot efficiently perform or manage the gradation conversion work.

(Example 2) Concentration characteristic curve used in the experiment The concentration characteristic curve shown in FIG. 4 (D-X coordinate system) (created arbitrarily by the inventors) was used as the concentration characteristic curve. Further, the relational expression for the concentration characteristic curve was used as shown in Table 1 (2). Note that this concentration characteristic curve is clearly different from that of Example 1.

2. Experimental Original Images Similar to Example 1, various color original images with different density ranges (DR) were used.

3. Calculation of data for setting the X-axis resolution curve The calculation was performed in the same manner as in Example 1. Note that the operating conditions for the <gradation conversion formula> are also exactly the same. The results are shown in Table 3. In addition, Table 3
(Nl, DR of 03 to 2.80 is normal, that is, a standard original with proper exposure.

(Left below) <Table 3> Data for setting the X-axis decomposition curve for any concentration characteristic curve (Part 1) <Table 3> Pig for setting the X-axis decomposition curve for any concentration characteristic curve (Part 1) 2) <Table 3> Data for setting the X-axis position decomposition curve for an arbitrary density characteristic curve (part 3) 4. The data of the X-candy color decomposition curve Table 3 are shown in FIGS. 5 and 6.

The graphing procedure is exactly the same as in Example 1. Figure 5 (
(present invention) and FIG. 6 (prior art), the same surprising fact as explained in Example 1 can be discovered. Also,
When FIG. 5 and FIG. 2 are superimposed, it can be seen that the X-ame color separation curves of both are exactly the same.

This means that even if the assumed concentration characteristic curves are different, (
Under the operating conditions of gradation conversion formula>, G, 310, 3
This means that if the .gamma.'s and .gamma. values are the same, the same X-ame color separation curves will be obtained.

The significance of this is important, and even when the density characteristic curves of each color of R, G, and B of a photographic light-sensitive material are not represented by a single density characteristic curve, and color original images are strongly affected by color fog (
This means that the image gradation conversion management method of the present invention can be effectively applied even when the density characteristic curves of each color are mutually shifted in parallel or have different slopes.

(Example 3) 1. For those whose concentration characteristic curve is a straight line.

In FIG. 6 of Example 2, the concentration characteristic curve is a straight line f
The D-axis integration curve of (linear) is shown (see (Ll) in Figure 6).
This was determined for a 5° diagonal line. next,
Using the density characteristic curve of FIG. 1, another example in which the density characteristic curve is a straight line will be investigated.

Using the density characteristic curve of FIG. 1, a straight density characteristic curve was drawn in the following manner.

That is, the concentration range on the D axis is DR・0.39 to 2.70.
A straight line parallel to the X axis is drawn from the two points, a point where it intersects the concentration characteristic curve is found, and the straight line is obtained by connecting both of the intersection points. Data for setting the X candy color separation curve was calculated from the thus obtained linear characteristic line.

In addition, <Gradation conversion formula> The operating conditions of This is exactly the same as Example 1.

Table 4 shows calculation data. Indicates evening.

(Left below) Table 4 Data for X-axis stem decomposition settings in Table 4 (Xn and γ after adjustment
When the values) are plotted in FIG. 2, it becomes the same as the X candy color separation curve shown in FIG. This is the X of the present invention.
This means that the technology for setting the candy color separation curve gives exactly the same results as in Example 1, regardless of whether the density characteristic curve at the original stage is linear or curved.

Next, we examine the case of OR・0.55 to 3200 in the same way. This is because the above is OR・039~2
70, which is an overexposed color original image (light quality), whereas an underexposed color original image (
This is an attempt to verify the image quality (dark image quality). The data for setting the X candy color separation curve in Table 5 is shown.

(The following is a blank space) <Table 5> When the data in FIG. 5 is plotted in FIG. 2, it becomes exactly the same as the X candy color separation curve shown in FIG. 2 as described above.

From the above, by using the X-color separation curve setting technology of the present invention, even if the density characteristic curve of the original image (medium image) is shown as a straight line, a, y in the <gradation conversion formula>
,.

y8. It can be seen that by making the γ values the same, all the same X-ame color separation curves can be obtained.

Then, the gradation conversion work can be efficiently managed based on the X-tone color separation curve obtained in this way.

As is well known, the original images that are subject to the color separation work of a color scanner include paintings such as water strokes and oil paintings that have a density characteristic curve or a straight line, and reflective originals such as illustrations (the actual object itself is not color separated). (Actual objects are evaluated by human vision using logarithmic optical density, that is, the density gradient is evaluated to be linear), and positives recorded on photographic light-sensitive materials whose density characteristic curves are curved. There are transparent originals such as negative film images. As mentioned above, it is clear that the present invention is effective even in the case of a reflective original whose density characteristic curve is a straight line, and is highly versatile as it does not require any distinction whether it is a reflective type or a transmissive type.

(Example 4) As a color original image, the following f of 4''x5'' manufactured by Company F
I tried producing a color printed image using il (21).

fi) Color original image In order to verify whether the gradation conversion method of the present invention is effective for color original images of any image quality, H (brightest part) shown in Table 6 below was used. ) and S (darkest part) were prepared with different density values.

Note that the light original/standard original/dark original in Table 6 below refers to overexposure/normal exposure/dark originals, respectively.
It means a photograph taken with underexposure.

(The following is a blank space.) <Table 6> (ii) Setting of the X-axis combination and separation curve Table 6 shows the X-axis combination and separation curve of the C plate cylinder used for color separation of each color original image. 1, the data for setting the X-axis combination and decomposition curves for various concentration ranges (DR) is obtained, so the results are used (Table 2 and Figure 2 sidebar).

The parameter conditions for setting the C-plate X-axis color separation curve are as follows.

3'H=5%, y,=95%, a=1.00°γ=1.00. β = 0.10 On the other hand, the X-axis combination and decomposition curves for M version and Y version are y H =
3%, y, = 90%, halftone dots in the midtone area are 10 more than the C version
% less, and decided to use the same curve. Furthermore, the X-axis combination/resolution curve for the K plate was created in accordance with a conventional method.

(iii) Magnuscan M-6 is used as a color scanner for color separation and color calibration.
Color separation was performed using 45 (manufactured by Crossfield). For color proofing, a color proof printed image was produced using a Cromarin proofing machine (manufactured by DuPont), and the image quality was evaluated.

(iv) Results As expected, all three color proof print images produced as described above had the same quality.

In addition, the contrast between highlights and shadows was well expressed, and the density gradient from the highlights to the shadows felt natural to the human visual sense, which was satisfactory.

(Effects of the Invention) The gradation management method of the present invention when producing a correlation with a logarithm adopts an approach completely different from the conventional one. For example, when the present invention is applied to the process of producing a color printed image as a correlation with a logarithm, the conventional color separation technology (core is the technology for setting the D-axis color separation curve) is limited to a photographic light-sensitive material (photographic round material). ), the color separation technology C of the present invention is basically a technology for setting an X-axis combination/separation curve). Previous subject (real image,
The approach is to get close to the actual scene.

Due to the difference in approach described above, the following excellent effects can be achieved; The image quality of the printed image cannot be accurately known in advance. In practice, it is necessary to set an optimal color separation curve for each color original image, which must be evaluated by proof printing. However, the technology for setting the color separation cube of the present invention is applicable to the density range defined on the density characteristic curve (or straight line) and the density characteristic curve (or straight line) in the original image, regardless of the quality of the original image. ) has the same shape, if the Q, yH, yg, and γ values in the gradation conversion formula of the present invention are the same, only one Only. In addition, the X-axis combination/separation curve has the extremely important characteristic that it serves as material for rationally determining the quality (the arrangement of halftone dots) of the printed image that is the final product.

Therefore, in the conventional technology, it is necessary to perform scanner setup work to set the optimal color separation curve, and to perform grooving work on the color original in advance to increase the efficiency of the color separation work. Unable to perform or manage key conversion tasks.

On the other hand, in the present invention, the tone of the color print image to be reproduced (the arrangement state of the halftone dot area percentage values) can be reasonably and objectively confirmed in advance using the X-axis combination/separation curve. In other words, by training in advance the technique of reading the tone of a color print image from the shape of the X-axis combination/separation curve or the arrangement of dot area percentage values, it is possible to check and adjust the tone of the color print image. . With this, apart from external proofreading, internal proofreading and blueprints (hard and soft proofs) can be omitted. Note that in order to change the tone of a color printed image, it can be rationally handled by adjusting the parameters (particularly the γ value) of the above-mentioned <gradation conversion formula> of the present invention.

(iil color original image (medium image) is R,G.

B Even if the density characteristic curve of each color is recorded on a photographic light-sensitive material that is not represented by the same density characteristic curve, it may be a standard one or a non-standard one (under/over exposure). However, there is even more color fogging (color
cast.

fog), an appropriate X-axis decomposition curve can be set according to the present invention. That is, in the present invention, these requirements or abnormal requirements are automatically absorbed or processed into the X-axis combination/separation curve setting technology, and the problems of color fog and color balance (gray balance) are simultaneously and automatically resolved. It can be solved. In addition, by adjusting the parameters in the gradation conversion formula of the present invention based on the initially set X-axis resolution cube, gradation control can be rationalized to obtain the desired image quality. It can be done.

The effects of the present invention have been explained above with emphasis on the production of printed images in terms of correlation with logarithms, but it goes without saying that similar effects can be achieved in the production of correlations with other logarithms. be.

[Brief explanation of drawings]

FIG. 1 shows a density characteristic curve of a color film (manufactured by Company F). FIG. 2 shows an X-axis combination/decomposition curve (according to the present invention) set based on the density characteristic curve of FIG. 1. FIG. 3 shows a D-axis position decomposition curve (conventional example) set based on the concentration characteristic curve of FIG. 1. FIG. 4 shows an arbitrarily created concentration characteristic curve. FIG. 5 shows an X-axis position resolution curve (according to the present invention) set based on the concentration characteristic curve of FIG. 4. FIG. 6 shows a D-axis position decomposition curve (conventional example) set based on the concentration characteristic curve of FIG. 4.

Claims (1)

[Scope of Claims] 1. A method for managing gradation when producing a reproduced image such as halftone gradation from a medium image as an original recorded on a predetermined recording medium, which includes: (i) original image ( (a) The density information value (D) of each pixel of the original image (media image)
(2) An image information value (X_n value) correlated to the amount of light incident on the recording medium from the corresponding pixel of the subject forming the source of the original image (medium pixel); A gradation characteristic curve is set in relation to the gradation intensity value (y value) such as the halftone dot area % value obtained by applying the gradation conversion formula; (ii) the gradation is determined by the gradation characteristic curve; A gradation management method when producing a reproduced image characterized by: <Gradation conversion formula> y=y_H+α(1-10^-^k^x)/a-β・(
y_S−y_H) [However, in the above <gradation conversion formula>, x: (X_n−X_H_n) is shown. That is, the original image (
From the density information value (D_n) of any pixel on the medium image), the density characteristic curve of the medium on which the original image is recorded (the image information value correlated with the density information value and the amount of light of the subject incident on the recording medium) is determined. The image information value (X
__n) to the brightest part (H part) on the original image (medium image)
A basic light amount value obtained by subtracting an image information value (X_H_n) that correlates to the light amount of the subject (substantive image) obtained from the density information value (D_H_n). y: A gradation intensity value such as a halftone area % value of a pixel on a duplicate image corresponding to an arbitrary pixel on the original image (medium image). y_H: A gradation intensity value such as a halftone dot area % value that is arbitrarily set in advance at the brightest part (H part) on the original image (medium image) or the subject (substance image). y_s: A gradation intensity value such as halftone area % that is arbitrarily set in advance at the darkest part (S part) on the original image (medium image) or the subject (substance image). α: Surface reflectance of the base material used to express the reproduced image. β: A value determined by β=10^-^γ. k: γ/(X_S_n - X_H_n) However, X_S_n is image information correlated to the light amount of the subject (substantive image) defined by the density value (D_S_n) of the darkest part (S part) on the original image (medium image) Indicates the value (X_S_n). γ: arbitrary coefficient. respectively. ] 2. The horizontal axis on which the gradation characteristic curve displays the image information value (X_n value) correlated to the amount of light incident on the recording medium from the subject and/or the density information value (D_n value) possessed by each pixel of the medium image , and a gradation intensity value (y value) such as a halftone dot area % value of the reproduced image is displayed in an orthogonal coordinate system with a vertical axis. How to manage gradation. 3. The original image (medium image) is recorded on a photographic photosensitive material, and the image information value correlated to the amount of light of each pixel is the correlation between the photographic density value and the logarithm of the amount of exposure incident from the subject. 2. The method of managing gradation when producing a reproduced image according to claim 1, wherein the gradation is determined from a prescribed photographic density characteristic curve. 4. The original image (medium image) is recorded on a photoelectric material or photoconductor, and the image information value correlated to the light amount of each pixel is the density value of the medium and the light amount value incident from the subject. 2. The method of managing gradation when producing a reproduced image according to claim 1, wherein the gradation is determined from a density characteristic curve that defines the correlation between gradation and gradation. 5. The original image (medium image) is recorded on an optical disk or magnetic disk, and the image information value correlated to the light amount of each pixel is the correlation between the density value of these media and the light amount value incident from the subject. 2. The method of managing gradation when producing a reproduced image according to claim 1, wherein the gradation is determined from a density characteristic curve that defines the gradation.