KR930002877B1 - Tonal conversion method for pictures - Google Patents

Abstract

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Description

Gradation Conversion Method for Making Duplicate Images from Original Images

1 shows the density characteristic curve (basic concentration characteristic curve) of the color film photographing agent (manufactured by F Company).

2 shows a method for setting a reference concentration characteristic curve and a home individual concentration characteristic on a basic concentration characteristic curve.

3 shows the principle of matching the individual individual density characteristic curve with the reference density characteristic curve of a color document image.

[Purpose of invention]

[Industrial use]

The present invention is to provide a method for reasonably producing a duplicate image from an original image which does not have a concentration range serving as a guide for the work in discipleship a duplicate image.

More specifically, the present invention has only one area of white or black in an original image, or a desired density gradation from a continuous image of a gradation gradation such as a color film document (transmission document) having both areas. TECHNICAL FIELD [0001] The present invention relates to a method for producing a replica image such as a halftone gradation having a gradation and a tone, and in particular, a gradation conversion method which is a basic technology thereof.

[Prior art]

Duplicate images such as a print image, a copy image, and a printer image are produced from various gradation original images by various duplication techniques. In producing these duplicate images, it is extremely important to reproduce the gradation and tone of the original image with the regularity and efficiency faithfully and faithfully on the duplicate image. However, despite the current duplication technique, it is a reality that the above reproducibility cannot be reasonably and efficiently carried out with work regularity, and is particularly insufficient for duplication of color original images.

In this regard, a description will be given in detail by quoting a technique for producing a halftone gradation print image from a continuous gradation color film original image (hereinafter referred to as a color original image).

In general, a color print image is produced by color separation of a color original image by a color scanner, and a multicolor plate (generally C plate, M plate, Y plate, and K plate) is reproduced to reproduce a halftone print image. .

At present, almost all color separation operations at the time of engraving in Japan are processed using a color scanner, and the number of movable scanners is about 2,400.

In addition, about 460 total scanners, which can also perform processing such as collecting work after color separation, are used.

These color and total scanners are mechatronics extremely expensive devices, but one of the major problems in the art is that they have a low operating rate of about 30% on average. The reason for such low operation rate is that there is a long setup time for operating the color scanner, and there are many rescans due to insufficient quality of the product obtained by color separation. .

Considering this from a technical point of view, as described above, as a tool for color separation, a highly mechatronicized color scanner or the like is used, but a plurality of element technologies of color separation, such as color correction and density, are used. Gradation is not coherently organized, which contributes to the low cost rate of color scanners.

As is well known, color correction among the above two element technologies has been pursued scientifically with utmost scrutiny, such as masking equations and Neubauer equations, but the latter gradation (this It is a matter of whether or not to match the dots of size.) Is left unsupported by rational theory, and this part is largely dependent on human experience and feeling. In other words, it is always possible to manufacture products of stable quality by using the highly advanced electronic color separation apparatus, without the operator's guess work or without operator's experience and feeling. It is not.

Next, attention is paid to the color original image, apart from problems of color separation apparatuses such as color scanners.

In general, in a color original image, a white area serving as a guide for the production of a printed image (referring to the literal name of the original in the original image, or the term "name part" is relative even when there is no white part in the color original image. The term "white area" is used in the following description to distinguish between the two and the black area (literally the darkest part of the original image). It is common to be.

However, many of the white or black regions contain only one of the color original images, or many of them are not included. In such a case, it is not entirely supported by the scientific theory as described above that a certain size dot (which is a problem of the gradation described above) is required to correspond to a predetermined pixel in a color original image, so that scanning is entirely performed. It depends on your experience and feeling. This significantly increases the set-up time of the color scanner or increases the number of rescans due to dark scanner operation, thereby lowering the operation rate of the color scanner.

[Problems to Solve Invention]

MEANS TO SOLVE THE PROBLEM This inventor thinks that there exist prior art important techniques which must be solved prior to solving these problems in order to solve the above-mentioned problem.

These important prior arts include image gradation conversion technology (technology that converts continuous gradation image state to 1: 1 gradation image to halftone gradation image), elimination of color cast fog in original image, In addition, it is not only simply converting the state of the color original image faithfully to the gradation of the printing image but also a technique of producing a printed image having a desired state of the color original image with work regularity.

In the development of these prior arts, the present inventors and the like, the gradation conversion formula of the image to be the predecessor of the " gradation conversion formula " used in the present invention (although the theoretical basis is the same in both, the application aspects are different. (See Special Elements 63-2590, East 63-114599, East 63-207326, East 63-259360, etc.).

According to the present invention, a color original image having only one of a white region and a black region or having both density regions thereof in a color original image using the gray scale conversion formula of the image as the core of these prior arts. In order to provide a technique for producing a print image with reasonable regularity and efficiency, excluding the experience and feeling of a Scanner operator. In addition, this invention is not limited to manufacture of a print image, It is mentioned later that it is applied to manufacture of all kinds of duplicate images.

[Configuration of Invention]

[Means to solve the problem]

According to the present invention, a gradation conversion when a duplicate image such as halftone gradation is produced using a continuous gradation document image having only one of a white region and a black region or having both concentration regions thereof. In the method, i) the original individual density characteristic curve which hypothesizes the density characteristic from the white region (concentration value H _n ) to the black region (concentration value S _n ) of the original image (a) in the case of an original image having only a white region. Is assumed to have a black area, and (b) a white area is assumed to have only a black area, and (c) a white area and a black area have both white and black areas. home hameuroseo, each defined, and ⅱ) the other hand, in the production of the replica image, the back region (concentration values H _o) and the black area (concentration values S _o) group of standard originals is used as a standard original having both the Density characteristics defining the curve and, ⅲ) assumes discrete density characteristic curve of the original image of the (ⅰ) (assumed density station _{H n ~ S n = DR n} ) the standard density characteristic area of the standard originals in the (ⅱ) (concentration Contrast H _o ~ S _o = DR _o ) and at the same time the concentration information value (D _o ) on the reference concentration characteristic curve after adjustment corresponding to the concentration information value (home D _n ) of any point on the home individual concentration characteristic curve. ) A gradation conversion curve for converting the density information value of the original image into a gradation intensity value (y) such as the half-dot area% from the above D _o value according to the following gradation conversion equation; Based on the gradation conversion curve obtained in Fig. 2, the density information obtained by actually measuring an arbitrary pixel of the original image (measured D _n ) is converted into a gradation intensity value y such as halftone area%. To convert a grayscale image from a duplicate image.

<Gradation conversion formula>

However, in the above <gradation conversion formula>,

(D _o -H _o): the less the density information value (D _o) back area concentration values (H _o) of the standard original picture from the adjusted density information value corresponding to the original (measured D _n) of a pixel on the image Basic concentration value.

y: gradation intensity value, such as the half-dot area% of the pixel of a duplicate image corresponding to the arbitrary pixel of an original image.

y _H : Gradation intensity value such as the area of halftone point, which is set in the white part existing in the original image, or at the sharpest part of the duplicate image corresponding to the assumed white area.

y _S : Gradation intensity value such as the area of halftone dots set in the darkest part of the original image or the darkest part of the duplicate image corresponding to the assumed black region.

(alpha): The surface reflectance of the base material used for expressing a replica image.

β: A value obtained by β = 10 ^-r .

K: The value obtained by γ / (S _o -H _o ).

γ: arbitrary coefficient

Respectively.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated in detail.

In the following, a case in which a color print image is produced using a gradation conversion method for producing a duplicate image from an original image according to the present invention as a duplicate image will be described. Therefore, this is for convenience of description and does not mean that the present invention applies only to duplication of color print images.

At present, the color scanr color separation apparatus is extremely generally used in the duplication of color print images, and in the case of the standard color image processed by the apparatus, the scanner operator may be changed. Print images of relatively stable image quality are produced. That is, as a color original image, white and black areas exist in the color original image, and when a density range (Density Range = D, R) is used (hereinafter referred to as a standard document), the state is relatively ordered. A color original image can be produced.

Here, the characteristics of the color original image used for producing the color printed image including the standard document will be described based on the density characteristic curve of the photographic material of the color film. 1 shows the density characteristic curve (color film made by F company) of a color film photographic material, and the vertical axis represents the object concentration (D) of the color original image, and the horizontal axis represents the exposure amount (X).

의 발의 부분(AB간), 거의 직선상의 부분(BC간). 위의

의 어깨의 부분(CD간)을 갖는 것이다. 그리고, 그 컬러필름사진감재의 농도특성곡선상에, 표준원고를 포함해서 각 개별의 컬러원고화상의 농도특성곡선이 규정된다. 이것은, 촬영이 끝난 컬러필름의 현상조건을 일정하게 하면(이 조건은 일정하게 유지되어 있다고 보아도 지장이 없다.), 개개의 원고화상의 농도특성을 규정하는 것은 노광량의 상이에 따르기 때문이다.As shown in FIG. 1, the density characteristic curve of the color film photographing material is schematically shown below.

Part of the foot (between AB) and the almost straight part (between BC). Over

It is to have a part of the shoulder (between CD). Then, on the density characteristic curve of the color film photographing material, the density characteristic curve of each individual color original image including a standard document is defined. This is because, if the developing conditions of the photographed color film are made constant (this condition is not impaired even if it is kept constant), the density characteristic of each original image is determined by the difference in the exposure amount.

That is, the density characteristic curve of the color film photographic material shown in FIG. 1 is a basic thing which defines the density characteristic curve of each individual document, and this is called basic density characteristic curve hereafter. The density characteristics of each individual document can be defined on the basic concentration characteristic curve as follows.

I) Standard manuscript

It is appropriate exposure and is located between BCs of the basic concentration characteristic curve. (It has the lowest concentration concentration H _o and the lowest concentration concentration S _o .) As a standard document, for example, the concentration meter measurement is H _o = 0.3 and S _o = 2.80. I can lift it.

Ii) over exposed originals

Because of the overexposure, the brightest part is located between the A point and the darkest part between BCs (having the sharpest part concentration H _n ).

광) Underexposed manuscript

Underexposure causes the darkest part to be located at point D and the brightest part between BC (between the darkest part concentrations S _n ).

Regardless of the standard originals in these color original images, the white (or outermost) region in the color original image of (ii) enters the region of H _o to H _n beyond B in FIG. A color scanner that is not in the vicinity of this S _o value or that the black area of (i) enters the area of S _o ~ S _n beyond C of FIG. 1, and the white area is not in the vicinity of the H _o value. In the case of processing with, it is impossible to reasonably perform the scanning color separation, and production of a print image having good image quality is highly dependent on the experience and feeling of the operator. It is extremely difficult to perform the engraving process if the color original image does not have both the white area and the black area (however, it has a relatively brightest part and the darkest part). Here, the white area is the area having the sharpest portion H _o (specifically, the value of about 0.3 in the densitometer measured value) in the standard document or a concentration value close thereto, and the black area is the darkest concentration S in the standard document. _o (specifically around 2.8 in the concentration measuring instrument) or in an area having a concentration value close to it.

What size dot should be matched to the white (or outermost) region or the black (or darkest) region, or both, which are broken in the non-standard manuscript; This is because there is a lack of rational means for determining how to set the concentration gradient between the two. In addition, the density characteristic curve of the standard document defined by the specific density range of the basic density characteristic curve is called the reference density characteristic curve, and is set between BCs in FIG. In addition, the density characteristic curves of the non-standard manuscripts described above are also defined at different ranges on the basic concentration characteristic curves and are referred to as individual concentration characteristic curves.

The present inventors have made various studies aiming at automating the color separation work using a color scanner as described above, and as a result,

1) Gradation conversion technology capable of converting the state of original image (density gradation and hue) of continuous gradation into faithfully duplicated image of halftone gradation with a work relation of 1: 1 and faithfully. Of the above-mentioned <Gradation Transformation Formula> (Special Elements 63-2590, East 63-114599)

2) Adjust the individual density characteristic curve of the color original image by performing a mathematical process on the standard density characteristic curve of the standard document, that is, the density information value of any pixel in the color original image corresponds to the standard density characteristic curve of the standard document. After adjusting to the density value, it was processed by the gradation change technique of the above (1), and the technique (Special element 63-207326) which always produces the same printed image as what is obtained from a standard document was developed.

The present invention utilizes an extremely inappropriate color original image as a color original image, which has only one of a white region and a black region, or has both density regions thereof, for reproducibility of the state of an original image. It is to provide a way to reasonably produce excellent printed images. To this end, the present invention utilizes the above-described techniques (1) and (2) proposed by the present inventors, but here again, the characteristics of the color original image to be processed by the present invention will be described again.

The inventors of the present invention have one of the white region or the black region in a color original image or use a color original image missing both of them to perform rational color separation based on the following assumptions. I think it is important.

In other words, it is assumed that there is a white area and a black area in a specific color original image to be processed, and it is assumed that the density range of the color original image can be specified.

This is because, from the value of the specific concentration range assumed in this way, the individual concentration characteristic curve of the home (the above-described individual concentration characteristic) is shown on the density characteristic curve (basic concentration characteristic curve) of the color film photographic material of the color original image shown in FIG. This is because the distinction from the curve can be defined as a home individual density characteristic curve.), And sufficient density information of an image is obtained necessary for color separation therefrom. After making this assumption, as described above, the inventors adjust the individual concentration characteristic curve proposed by the present inventors to the reference concentration characteristic curve, and further, by using the density information of the image after the adjustment, it is always equivalent to that obtained from the normalized image. The gradation conversion technique which guarantees the production of a print image of image quality may be combined.

For example, the back has a regions black area if the color separation by the color original image does not have the (above-mentioned region having a near concentration values in the S _o of the standard originals as) the color scan too, that the color of the original image the darkest part (It is important to note that this is the relative darkest part and not the black area.) How much halftone is set is always an important consideration.

In the present invention, in view of the normalized concentration range (shown in FIG. 1 as H _o -S _o = DR _o ), the color original in relation to the size of the halftone set in S _o of the standard original. It is to rationally decide what size of dot is to be set at the darkest part of the image (relative), and to completely exclude the extra work, experience, and feeling of the scanner operator.

In order to determine the home density range of the specific color original image described above, an objective fact can be used that the difference in density of many color original images in parallel between the white area and the black area takes almost a constant value.

However, the difference in density between the white and black areas in the color original image varies from 0.10 to 0.20 depending on the brand of the color film, the type of the subject, the determination criteria of the black and white area, and the exposure conditions at the time of photographing. Therefore, in order to accurately grasp the difference in density between the white and black areas, the density values of the white area and the black area in the color document image are accumulated, arranged, and processed for each film trademark, and data for specifying the density range or density gradient is obtained. You need to get it.

An example of setting the individual individual concentration characteristic curve will be described with reference to the drawings. FIG. 2 is a diagram for explaining a method for setting a hypothetical individual density characteristic curve on the assumption of the density range of the color original image from the white area (most part) concentration value or the black area (most part) density value of the color original image.

In the case of the color film manufactured by Company F by irradiation of the color original image having the white area and the black area described above, a color original image of a light state with a large amount of exposure at the time of shooting (overexposure) or a standard image exposure (suitability exposure) It is possible to grasp the general tendency that the density range of an image is about 2.60, and the density range of a color original image having a low exposure amount (underexposure) is about 2.50. Their empirical facts are reflected in the drawing of FIG. That is, in the color original image having the white area H ₁ , the assumption of individual individual density curves (H ₁ to S ₁ ) is made on the assumption that the black density is S ₁ = H ₁ +2.60, and the color having the black area S ₂ is defined. In the manuscript image, it is assumed that the white concentration H ₂ = S ₂ -2.50, and the individual individual concentration characteristic curves H ₂ to S ₂ are defined.

If both the white and black areas are missing in the color original image (of course, the relative edges and darkest portions exist, of course), the individual density characteristic curves of the color original image are color. By measuring the relative edges and shadows in the manuscript image, it can be specified on the basic density curve. The individual density characteristic curve of the color original image is defined as a specific range on the standard density characteristic curve of the standard document. This is because if either side exceeds the density value at both ends of the density area of the standard document, it belongs to the category of the color original image which is missing either the white area or the black area or the black area. In the present invention, it goes without saying that the concentration range of the home concentration characteristic curve described in the three examples can be arbitrarily set.

In addition, if the color original image is a reflective document (it should be noted that the above description is based on the transmission document). For example, color paper, ilast painting, watercolor painting, etc. In the case of color separation, the basic density characteristic curve is almost linear, and in this case, the individual density characteristic curve of the color original image is defined by any predetermined range on the basic density characteristic curve on the straight line. For example, it is set between the density ranges of the white density of color paper, drawing paper, etc., and black density, such as gray, black ink, cloth.

Therefore, the hypothetical individual density characteristic curve of the color original image which has dropped both the white area (the area having a density value close to the standard value of H _o of the standard document) and the black area (the area having the density value close to the standard value of S _o of the standard document) is obtained. In the case of a transmissive document, the standard concentration characteristic curve can be assumed in the standardization, and in the case of the reflective document, the basic concentration characteristic in the straight line can be assumed. That is, in the color separation operation, in the case of a color original image having neither the white region nor the black region, the procedure for adjusting the home individual concentration characteristic curve to the reference concentration characteristic curve is omitted.

In the case of such a color original image, the steps (i) to (iii) of the present invention to be described later are largely omitted, and the color separation may be performed using a <gradation conversion equation> as it is. When color separation is performed according to the conversion formula>, a print image of a natural state is always obtained with a regularity of work, and an individual density characteristic curve of such a color original image is defined on a reference density characteristic curve. Because. It goes without saying that the individual density characteristic curves of the color original image in which both the white region and the black region mentioned above can be arbitrarily moved within the range of the reference density characteristic curve. This is because the color original image is not manufactured under appropriate exposure conditions (in this case, individual concentration characteristic curves can be defined within a range on the reference concentration characteristic curve. Means necessary for matching the appropriate exposure conditions) to be.

As described above, in the individual color original images to be subjected to the color separation work by the color scanner, the home concentration range is specified and the home individual concentration characteristic curve is specified. That is, the process of said (i)-(ii) of this invention is complete | finished.

Next, a method (described step (i) of the present invention) of adjusting the individual individual concentration characteristic curve to the reference concentration characteristic curve will be described. This adjustment method was previously limited by the present inventors, etc. (Japanese Patent Application No. 63-207326), The summary of the adjustment method is as follows.

The principle of adjusting the individual individual concentration characteristic curve to the reference concentration characteristic curve is shown in FIG.

First, it is necessary to define a function of the basic concentration characteristic curve in order to mathematically perform the adjustment.

For example, this can be defined as a function of D = f _D (X) shown in the following first table. It is to be understood that the function definition of the basic concentration characteristic curve in the first table is one example, and it goes without saying that it can be specified arbitrarily. Further, in the first table, in addition to D = f _D (X) for obtaining the concentration value D from the exposure amount X, X = f _X (D) for obtaining the exposure amount X from the concentration value D, which is its inverse function, is shown. have.

TABLE 1a

TABLE 1b

Note: In the basic concentration characteristic curve shown in FIG. 3, a function f _D (X) for obtaining X → D and a function f _X (D) for obtaining D → X as its inverse function are shown.

Note: In order to faithfully define the basic concentration characteristic curve, it is formulated in each domain of X or D.

As shown in Fig. 3, the standard density characteristic curve of the standard document and the individual individual density characteristic curve of the color original image are specified on the basic density characteristic curve of the color film photographing agent, and the density value of the color original image is D _Hn to D _Sn. Is projected onto the X-axis to match the range (X _Hn to X _Sn ) of the color original image on the X axis to the range (X _Ho to X _So ) on the X-axis of the standard density characteristic curve.

Next, the concentration values D _Ho to D _So on the D axis of the reference concentration characteristic curve are obtained.

In this way, the color original image can adjust the density information value D _n of the home density range to the density information value D _o on the reference density characteristic curve. As a matter of course, it is needless to say that when the home individual density characteristic curve of the color document coincides with the reference density characteristic curve, the matching of both is unnecessary.

As a means of matching the individual and reference density characteristic curves, it generally does not coincide with XR _o (the exposure range of the standard density characteristic curve of the standard document) and XR _n (the exposure range of the individual individual characteristic curves of the non-standard individual document). Since it is normal, it is necessary to mathematically proportionally match both characteristic curves.

Of course, a simple matching method such as simply matching the starting point (or end point) of the range may be employed. This is necessary to eliminate both the white and black areas as described above, and to move the individual concentration characteristic curve within the standard concentration characteristic curve in a color document image whose individual concentration characteristic curve is defined in the reference density characteristic curve. Means.

In addition, in order to simplify the adjustment procedure, the individual individual concentration characteristic curve may be directly projected on the X-axis, and the value on the X-axis may be read as the concentration value, or the reference concentration may be read in the same manner. The image may be subjected to gradation conversion using the &lt; gradation conversion equation &gt; above with applying a desired process such as matching the density value of the characteristic curve.

As shown in FIG. 3, adjustment is performed by substituting the basic concentration characteristic curve D = f _D (X) from the concentration information value (D _n ) of the individual individual concentration characteristic curve, which is used for mathematical proportional matching operation. The relational equation for obtaining the X value for obtaining the density information value D _o of the color document is as follows.

Where m is the required amount of parallel movement

XR _o : Exposure range of standard density characteristic curve of standard document on X axis

XR _n : Exposure range of individual individual density characteristic curve of non-standard individual document on X axis

When the matching of the individual individual density characteristic curves with the reference density characteristic curve is completed, the density information value (D _o ) of the color originals adjusted from all density information values (D _n ) on the individual individual density characteristic curves is adjusted. You can get it. Substituting the D _o value obtained in this way into the &lt; gradation conversion formula &gt;, the color separation curve, that is, the density information value of the color original image (the density value of the continuous gray scale) and the image information value of the color print image (the halftone dot area of the halftone gradation) A gradation conversion curve (also referred to as a halftone gradation characteristic curve) is obtained, which deals with the correlation with. This process corresponds to the above-mentioned of this invention.

As a result, all the preparatory work for color separation of a color tone image of a continuous gradation having no one or both of the white region or the black region in the color original image using a color scanner are completed. The rest only leaves the process corresponding to the above-mentioned of this invention. This process is made by adjusting the density information value (actual D _n ) of an arbitrary pixel of the original image obtained by scanning a color original image (actual D _n → D _o ), and adjusting D _{o This} value is substituted by converting the value into the halftone area% (Y value) by substituting the above &lt; gradation conversion equation &gt;.

Based on the above-mentioned &lt; gradation conversion formula &quot; of the present invention, the standard density characteristics of standard originals satisfying the assumption of producing individual individual density characteristic curves of color original images and printed images with desired image quality When a curve is set and the two are connected by a rational method such as mathematical processing, even if the color original image does not simultaneously include both of its copy and the white region and the black region which serve as guides of the work, the regularity of work is always maintained. Can produce a printed image having a desired image quality (which is a natural state in human vision).

Furthermore, since there are many parameters at first glance in the parameter of the above <gradation conversion formula> of the present invention, the question arises whether or not the operation of the <gradation conversion formula> will be interrupted. However, in the cloning technique, such as printing the image, the parameters of the electric <gradation conversion formula> of y _H, y _S got the screen substantially constant, for example, in the case of printing an image, a 5% y _H of C plate, y A halftone area% of 95% is used for _S. Further, in the operation of the &lt; gradation conversion _formula &_gt;, when the concentration meter measurement value is used for the concentration value and the percentage value is used for y _H and y _S , the y value is also calculated as the percentage value. α is the surface reflectivity of the printing paper and may be α = 1.0.

A characteristic parameter in the present invention is a gamma value. This can be fixed at a value of gamma = 0.9 to 1.0 by suffocating the civil ink concentration value of the yellow ink at the time of color separation of a standard document. And in many cases, the outstanding result is obtained by the value of (gamma) = 0.9-1.0.

In the present invention, since the means for adjusting the home individual concentration characteristic curve of the color film original image to the standard concentration characteristic curve of the standard image is designed, the? Value may be fixed to the above value. The significance of being able to integer this gamma value is important, and that the term of the &lt; gradation conversion formula &gt; Therefore, the calculation of the tone conversion formula and the mechanism at that time can be simplified. Further, the numerical setting of these parameters differs depending on the position of faithfully reproducing the state of the given color original image as a printed image to the last, and the position of trying to produce a printed image whose state differs from the consciousness.

For example, since the shape of the color separation curve can be changed to a desired one by converting the? Value, printed images of various states are obtained.

In addition, the above-mentioned &lt; gradation conversion formula &gt; of the present invention is operated on a multicolor plate (generally, four plates of the C plate, the M plate, the Y plate, and the K (weapon) plate) are used. To set up, just do The above <gradation conversion formula> is derived from the viewpoint of reasonably determining the C plate, which is the most important plate among the multicolor plates.

Therefore, the color separation curve for the C plate is derived by the operation of the <Gradation Conversion Formula>, and the remaining color separation curves for the M and Y plates may be determined by multiplying the appropriate adjustment values to maintain gray balance or color balance. . Decomposition curve for the K (wet) plate may be determined according to a conventional method in the art in terms of reducing the consumption of C, M, Y ink.

Next, features of the operation surface of the &lt; gradation conversion equation &gt; of the present invention and the application surface of the tone conversion method of the present invention will be described.

In the operation of the &lt; gradation conversion formula &quot; of the present invention, the density information value means the density of each pixel of the original image (the present invention is not limited to the color original image when creating a color print image as described above). Anything that reflects the physical quantities in relation to is good and should be interpreted broadly. Synonyms include reflection concentration, transmission concentration, luminance, intensity, light intensity amplitude, current, voltage value, and the like.

In the operation of the &lt; gradation conversion formula &gt; of the present invention, it is free to use it by transforming and applying as follows, as well as by using any processing, deformation, or induction.

The above modification is made to be α = 1. This is, for example, 100% of the surface reflectivity of a printing paper (substrate) used to express a print image.

Although the arbitrary value can be taken as the value of (alpha), you may make it 1.0 for practical use. This also applies to luminance images such as video images.

In addition, according to the modified example (α = 1.0), for the y _H printed image choemyeongbu H (i.e., H _o portion on the normalized) on, the darkest part S hanba scheduled y _S (i.e., S _o portion on the normalized) It can set as it is, and this is the big characteristic in this invention.

This means that (D _o -H _o ) = 0 by definition for the brightest part H of the printed image, and (D _o -H _o ) = [reference image density range] for the darkest part S.

In other words,

Therefore, it is apparent from the fact that -k [(D _o -H _o ] =-γ .. Thus, in using the &lt; gradation conversion equation &gt; (a variation of α = 1) of the present invention, y _{H is} always as intended. and y is that _S be set to the printing screen imagination it will very important to to the user examines the work result. for example, when setting the change value γ values desired to y _H and y _S in the printing image (note , α = 1.0), and various color separation curves can be obtained, and the printed image obtained based on these color separation curves can be easily evaluated in relation to the? value.

In addition, the conversion processing method for image characteristics based on the &lt; gradation conversion formula &quot; of the present invention reproduces the gradation or color tone of an original image, i.e., reproduces the state of the original image as 1: 1 on the printed image with a regularity. Although extremely useful, its usefulness is not limited thereto. As described above, the &lt; gradation conversion _formula &_quot; of the present invention selects α, β, γ values, and even more y _H , y _S values as well as faithful reproducibility of the original image characteristics, thereby reasonably changing the image characteristics of the color original image. It is extremely useful for modification.

The operation of the &lt; gradation conversion formula &gt; of the present invention has been described so far in particular in connection with the creation of a print image, but its application surface is not limited to the creation of a print image only.

That is, as the operating surface of the <gradation conversion formula> of the present invention, it is (i) to change the size of the print image or dot of the flat plate, flat plate, halftone gravure, silk, screen, etc., or the size of the dots (multi-valued). Of course, if the manufacture of the duplicate image or the color tone is to be expressed by the size of the dot (dot) seen in the thermal transfer image, etc. (this is also called the area gradation method), and (ii) the sublimation transfer type thermal transfer For shades such as pigments, dyes (pigments) such as printing inks to be attached to a certain area per pixel (e.g. per dot) that can be seen in images, (using silver salts) thermal development transfer images, conventions, gravure images, etc. If you want to express gradation or hue by color (this is also called density gradation method), (i) Schedule that can be seen in digital copier (color coppy, etc.), printer (ink jet, bubble jet, etc.), all facsimile Example of recording density per area G., The number of dots, in the case of trying to express gradation by changing the number of ink particles such case (which, it is similar to the area gradation of the (ⅰ).

(Iii) From electric signals related to image information such as video signals, television signals, hi-vision signals, etc., a CRT image expressing an image by adjusting the intensity of the luminance of a unit area or a grayscale printed matter or hardcopy (I) spatial, luminance, wavelength and temporal impossibility, as well as in the case of the conversion process of the image between the original image and the duplicate image in the above-mentioned substantially equal density (luminance, illuminance) region. Input conversion of image information in a low-light region where shooting in the field of view, for example, the original image is extremely low, and the density difference between the original image and the duplicate image is small, such as shooting by a high-sensitivity camera. (In this case, the emphasis is on the conversion of the contrast of the image rather than the conversion of the type of image.), (I) In addition to the density display, the halftone area% is also displayed. It can be applied to printing-related equipment such as a density gradation conversion mechanism part concentration meter, a color separation pre-check (for example, color proofing for calibration), and a shoe mill for color separation education.

Image related to image density obtained from continuous gradation (including hard originals and lofted originals) when the conversion processing method of image characteristics using &lt; gradation conversion formula &quot; of the present invention is applied to various applications described above. The information and / or image information electric signal (either analog or digital) may be performed by the image conversion processing unit (gradation conversion unit) of the apparatus of the various application fields described above, and correspond to the y value (gradation intensity value) which is its processing value. Control the current value, voltage value, or application time of the recording section (recording head) of the device to change the halftone area, the number of dots per predetermined area (one pixel), the concentration per certain area (eg one dot), and so on. It is sufficient to output a duplicate image such as a halftone gradation in which the density gradation is 1: 1.

For example, to produce an original image of a printed image, that is, a halftone gradation image, that is, a printing original, using a conversion process of image characteristics based on the <gradation conversion formula> of the present invention, an existing system well known in the art may be used. This is achieved by incorporating the image conversion processing method of the present invention into color separation network imaging apparatuses such as commercially available electronic color separation apparatuses (color, scanner, total, scanner). More specifically, a small amount of light is irradiated to an original image, which is a continuous gradation image such as a color photograph, to receive reflected light or transmitted steel (image information signal) by a photomultipler, and the intensity of light is applied to the intensity of voltage. And converting the obtained image information electric signal (electric value) by the computer into a necessary arrangement and processing, and controlling exposure light source light based on the processed image information electric signal (voltage value) output from the computer. In a well-known existing system that produces a printing disc by dividing a laser beam of light into a raw film, for example, a computer individual processing characteristic unit calculates a home individual density characteristic curve in a computer processing unit for processing an electrical signal of image information of an original image. By adjusting the characteristic curve and using the <gradation conversion formula> of the present invention, the image information electric signal of continuous gradation is converted into a halftone gradation image. The software that can be achieved with beam electrical signals only to be put squeeze.

As such software, the individual individual concentration characteristic curve of the present invention is adjusted to the reference concentration characteristic curve, and the above-described algorithm of &quot; gradation conversion formula &quot; is retained as software, and A / D (energy digital transformation), D / General purpose computer with I / F (interface) of A, electric circuit embodied by general-purpose IC with algorithm as logic, electric circuit including ROM which holds algorithm calculation result, PAL embodying algorithm as internal organization It can take various forms such as an array and a custom IC. In particular, in recent years, modulus has been developed, and the individual individual density characteristic curve of the present invention is matched to the reference density characteristic curve, and the conversion process of image characteristics in the density region is performed based on the &quot; gradation conversion formula &quot; The computing realization mechanism can be easily manufactured as a modul such as a dedicated IC, LSI, microprocessor, or microcomputer. Then, if the output light for photovoltaic use is progressed while dividing it into points, while the laser exposure unit is also synchronized with this, a halftone point having a numerical value y of the halftone area percentage derived by the &quot; gradation conversion formula &quot; A gradation printing disc can be easily created.

EXAMPLE

Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the thing of these Examples.

In the experiment,

○ A task of adjusting the measured concentration range of color original image to a predetermined family concentration range

○ The task of adjusting the individual individual concentration characteristic curve with the family concentration range to the standard concentration characteristic curve

○ A job of converting the measured concentration value (D _n ) of a predetermined pixel of a color original image into a corresponding density value (D _o ) on a reference density characteristic curve.

○ The software performs a series of tasks called creating a color separation curve by operating the above <Gradation Conversion Formula> using the D _o value after adjusting the D _n value and calculating the required amount using a PC-9800 personal computer manufactured by NEC Corporation. It was.

Example 1

As a manuscript, a color original image of 4 "x 5" made by Company F, which is a still object, was used as an interior still image.

The color original image had only a white region (concentration value 0.17) in the image, and the density value of the relatively darkest darkest portion (not the black region) in the image was 2.40.

The density range of the color original image was assumed to be 2.70, and the household concentration range was set from 0.17 to 2.87.

As shown in Fig. 3, the individual individual concentration characteristic curve having this family concentration range is assumed to be the basic concentration characteristic curve (the color original film concentration characteristic curve manufactured by F Company is the basic concentration characteristic curve, and its function display is shown in Table 1). I prescribed it.

On the other hand, on the basic concentration characteristic curve, as shown in Fig. 3, the basic concentration characteristic curve in the concentration range of 0.30 to 2.90 was defined.

Next, the hypothetical individual concentration characteristic curve was adjusted to the reference concentration characteristic curve to produce a color separation curve (for C plate) using the &quot; gradation conversion formula &quot; of the present invention. In addition, the conditions of the parameter at the time of preparation of a color separation curve are as follows.

y _H = 5% y _S = 95% α = 1.00

γ = 1.00 β = 10 ^-γ = 0.10 K = 1 / 2.60

Next, color separation was carried out using Magnuscanner M-645 (manufactured by Rosfield) as a color scanr for color separation. A color calibration printed image was produced by DuPont's chromamarine calibration method, and image quality was evaluated. As the M and Y plates, the halftone was set such that y _H = 3%, y _S = 90%, and the halftone region was 10% less than the C plate, and the K plate was in accordance with the commercial method.

The corrected printed image produced as described above was in a state as described as a whole. The gray balance was also well arranged, and the concentration of the dark portion was also appropriate.

In other words, the state of the proof print image is higher in density than the state of the color original image, and in particular, the contrast is emphasized at the highlight portion to more faithfully reproduce the state of the copy object. By the way, about 92% of the halftones were revealed in the darkest part where the density was 2.40 in the color original image.

In addition, in the course of this experiment, by properly setting the values of the parameters y _H , y _S , α, k, and γ from the characteristics possessed by the gradation conversion equation, the state of the calibration print image can be adjusted with regularity as scheduled. It was confirmed that there was.

Example 2

As a manuscript, a color original image of a still life in a bush in which the image to be reproduced does not include a white area was used. The density value of the black region of the color original image was 3.06, and the density value of the relative edge portion was 0.87.

The density range of the color original image was 2.50, and the household concentration range was 0.56 to 3.06.

Next, in the same manner as in Example 1, the density information of the color original image was converted into density information on the reference density characteristic curve (concentration range 0.30 to 2.90), and a color calibration printed image was produced.

The color correction printed image thus produced was obtained with a state image predicted in advance, and the concentration gradient from the shadow portion to the highlight portion was natural and satisfactory for the human visual sense. In other words, the state becomes brighter as compared to the color original image, and the state of the shadow portion is well represented. In addition, about 23% of the halftones were revealed in the color original image where the density was 0.87.

Example 3

As a manuscript, watercolors in which both white and black areas were missing were used. The maximum concentration of the watercolor was 0.50 and the maximum concentration of 1.19 was 1.19. As is well known, watercolor is a reflection document, and its density characteristic curve is defined by a straight line. In addition, since the reference concentration characteristic curves (concentration range 0.30 to 2.90) prescribed in Examples 1 and 2 may be almost linear, it is considered that the concentration characteristic curve of watercolor is defined on the reference concentration characteristic curve. Therefore, the color separation may be performed as it is. Here, the state of the print image can be adjusted arbitrarily or with regularity by appropriately setting the characteristics of the <gradation conversion _formula >, that is, y _H , y _S , α, γ, K. The experiment was carried out utilizing the characteristics.

Therefore, it is better to increase the state of the calibration image as a whole (in this case, the larger the value of γ is derived from the characteristic of the &quot; gradation conversion formula &quot;), and to increase the contrast of the highlight portion (in this case, y _The numerical value of each parameter was set as follows in order to realize the request that _S is made small.

y _H = 5% y _S = 90% α = 1.00

γ = 1.20 β = 10 ^-γ = 0.063 K = 1.20 / 2.60

Scanner color separation and color correction were performed under the above conditions to produce a color calibration print image. The state of the color correction printed image thus produced is as it is, the density gradient is also natural for the human visual sense, and color balance is also arranged. In addition, when the size of the halftone of the color decomposed under the conditions of γ = 1.00, y _H = 5%, and y _S = 95% was examined from Hyra art to middle toon, it became about 2 to 3% in this experiment, It was consistent with the observation.

[Effects of the Invention]

The application surface of the gradation conversion method of the present invention is spread over a variety, but when applied to the production of a print image has the following effects.

Currently, mechatronics-priced expensive scanner devices are used to produce printed images, but are in a state of extremely low operation rate. This is due to the long setup time of the scanner and the high rate of rescanning, which determine the color separation of original images such as color documents.

According to the present invention, a color original image which is subject to rescanning due to the arbitraryness, experience, and feeling of the scanner operator, especially a color original image having no density portion corresponding to one or both of white or black. Even if it does, it can also process it automatically. Therefore, since the setup time for such a color original image can be significantly shortened, it is possible to remarkably improve the operation rate of the scanner. It goes without saying that the reduction of rescanning can eliminate waste of restraint and effort.

Further, the present invention is important for establishing the full automation of the scanner decomposition technology, as it is possible to automatically cope with the specific problems occurring in everyday life with the color separation technology by the scanner.

In addition, in the production of a print image based on the gradation conversion method of the present invention, the gradation conversion operation, which is its core, is performed using a `` gradation conversion formula '' that matches theory and practice. It can be done reasonably. That is, under the &quot; gradation conversion formula &quot; of the present invention, creative work such as production of a printed image in which the state is changed in addition to faithfully reproducing the state (density gradation and hue) of the original image in 1: 1. As a result, the plate making technology can be widely trained and practiced.

The gradation conversion method of the present invention is applied not only to the production of the above-described print image but also in the production of various duplicate images, and achieves the same effects as described above.

Claims (7)

A gradation conversion method when producing a duplicate image such as halftone gradation using a continuous gradation original image having only one of the white region and the black region, or both concentration regions thereof, Iii) A hypothetical individual density characteristic curve which hypothesizes the density characteristic from the white area (concentration value H _n ) to the black area (concentration value S _n ) of the original image; (a) In the case of an original image having only white area, By assuming an area, (b) in the case of an original image having only a black area, by assuming a white area, (c) in the case of an original image having neither a white area nor a black area, By assuming a black area, we define each, Ii) On the other hand, in the preparation of duplicate images, a standard density characteristic curve of a standard document used as a standard document having both a white area (concentration value H _o ) and a black area (concentration value S _o ) is specified. Iii) The individual individual density characteristic curves (household concentration ranges H _n -S _n = D _Rn ) of the original image (i) above are the reference density characteristic curves (density ranges H _o -S _o =) of the standard manuscript of (ii). D _Ro ), and the concentration information value (D _o ) on the reference concentration characteristic curve after adjustment corresponding to the concentration information value (home D _n ) of any point on the home individual concentration characteristic curve, Iii) From the above D _o value, a gradation conversion curve for converting the density information value of the original image into a gradation intensity value (y) such as the halftone area% is defined by the following gradation conversion equation, Ⅴ) Based on the gradation conversion curve obtained in the above (i), the density information value (measured D _n ) obtained by measuring any pixel on the image of the original image is converted into gradation intensity value y such as halftone area%. A gradation conversion method when producing a duplicate image from an original image, characterized in that the image is made. <Gradation conversion formula>

However, in the gradation conversion equation, (D _o -H _o ): from the density information value (D _o ) after adjustment corresponding to the density information value (actual D _n ) of any pixel of the original image, Basic concentration minus area concentration (H _o ). y: gradation intensity value, such as the half-dot area% of the pixel of the duplicate image corresponding to the arbitrary pixel of an original image. y _H : Gradation intensity value such as the area of halftone point, which is set in the white part existing in the original image, or the sharpest part of the duplicate image corresponding to the assumed back area. y _S : Gradation intensity value such as the percentage of halftone area set in the darkest part of the original image or the darkest part of the duplicate image corresponding to the assumed black area. α: surface reflectivity of the substrate used to express the replica image. β: A value obtained by β = 10 ^-r . K: The value obtained by γ / (S _o -H _o ). γ: arbitrary coefficient Respectively. 2. The original image according to claim 1, wherein if the original image has only a white region (concentration value H _n ), the duplicate image is assumed to have a density value S _n = H _n + (2.20 to 3.00) of the black region. Gradation conversion method during production. 2. The original image according to claim 1, wherein when the original image has only a black region (concentration value S _n ), the density value H _n of the white region is assumed to be H _n = S _n − (2.20 to 2.80). Gradation conversion method when making duplicate image. The gradation conversion method for producing a duplicate image from an original image according to claim 1, wherein the original image is a color original or a monochrome original. The gradation conversion method for producing a duplicate image from an original image according to claim 1, wherein the original image is any one of a reflective original, a transmissive original, and an electrically or magnetically recorded recording image. 2. The method according to claim 1, wherein when the original image is a color film document (transmission document), a hypothetical individual density characteristic curve and a reference density characteristic curve are plotted on a density characteristic curve (a curve representing the correlation between exposure amount and film density) of a photographic material. A gradation conversion method when producing a duplicate image from an original image characterized in that it is specified. The gradation conversion when producing a duplicate image from an original image according to claim 1, wherein when the original image is a reflective document, a hypothetical individual density characteristic curve and a standard density characteristic curve are defined on a nearly linear density characteristic curve. Way.

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