JP2000270219A - System lsi for converting gradation of rom type image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a standard specification of a tool for gradation conversion in the case of manufacturing various copy images. SOLUTION: This system LSI stores a program that executes a step where an image information in correlation with a luminous quantity of a corresponding pixel point from an image information in correlation with a density of an optional pixel point on an original image by utilizing a density characteristic curve being a characteristic of a recording medium denoting the cross-relation between original image information in correlation with a density acquired by scanning the original image recorded on a prescribed recording medium and image information in correlation with a luminous quantity incident to the recording medium from an object corresponding to form the original image and a step where the image information in correlation with the luminous quantity of the obtained original image is converted into gradation strength by using a prescribed gradation conversion expression, in an internal ROM 12 of the LSI 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a basic (core) image processing method for an image document when producing a halftone tone duplicate image from a continuous tone document image.
Program-based (ROM type) image gradation conversion system L for high-speed gradation conversion processing as a technology
Regarding SI.

More specifically, the present invention relates to image information processing of an original image when producing a duplicate image such as a halftone color print image from an original image such as a continuous tone color film original. , A built-in program for high-speed processing using a specific gradation conversion program that can standardize (standardize), standardize, and generalize the gradation conversion processing of image information as a basic (core) technology ( ROM type) image gradation conversion system LSI.

[0003]

2. Description of the Related Art Conventionally, in various applications, a system LSI, for example, a program (hereinafter referred to as a system program) built in an LSI under an arithmetic processing unit (hereinafter also referred to as a microprocessor unit or MPU). There is proposed a type of system LSI that executes the above. The system LSI is used for various purposes such as a system LSI for a portable personal computer, a system LSI for a (slim) notebook personal computer, a system LSI for a mobile phone, a system LSI for a digital television, and a system LSI for a network. I have.

The system LSI can be said to be a system in which MPU blocks and blocks such as blocks (IP, intellectual property) for realizing specific applications (functions) are systematized into large-scale logic LSIs. In other words, 10m
It can be said that various blocks such as an MPU block, an IP block, and a memory block for realizing a specific use (function) are systematically arranged (mixed) on an m-square silicon chip.

In the system LSI described above, there are roughly two directions of development. In other words, one is a standard product that is developed for use by an unspecified number of users, and the other is developed in cooperation with a specific customer for a specific application specification. is there.

In a system LSI in the field of image information processing, a block (engine) having high standardity and versatility is as follows. (1) Regarding compression and decompression processing of image information of a still image, a processing standard (JPEG) for a continuous tone image (for full color) and a processing standard (J for a binary image)
BIG), processing standard for FAX (MH, MR, MMR)
and so on. These processing standards include, for example, copy, FA
X, printers, and composite products thereof. (2). There are color moving image processing standards (MPEG1, 2, and 4) for compression and decompression of image processing of moving images.

For example, when producing a halftone color print image from a continuous tone color original image (a color film original as a transparent original or a color print original as a reflective original). There are basic (core) technologies that are qualitatively different from the image information compression and decompression technologies described above. This foundation (core)
The technology is a gradation conversion technology for reproducing the gradation characteristics of a document image into a duplicate image. Among the tone conversion techniques, the one that is primarily important is a tone conversion technique that can faithfully reproduce the tone of the original image, and the second is that the tone of the original image is integrated. This is a gradation conversion technology that can be converted to the intended purpose.

A basic (core) method for producing a halftone halftone copy image from the above continuous tone original image
As described below, the gradation conversion technology, which is positioned as a technology, has not yet been established as standard (standardization) and versatility to date. In other words, although the gradation conversion technology is fundamental and core in image information processing technology, printing equipment,
It relies on proprietary development by image-related manufacturers such as copy devices, and lacks standardity and versatility.

Hereinafter, a conventional gradation conversion technique will be described by taking the field of a color print image as a representative example of a duplicated image.

In order to produce a high quality, high quality halftone image and a color print image meeting the needs of the audience from a continuous tone color original image, as shown in FIG. In order to carry out (all systems, whole field) rationally and efficiently, there are extremely complicated and various check items and examination items, and items that need to be considered. If we take the conclusions ahead, it can be said that such a complex system has prevented the generalization (standardization) of the gradation conversion technology to date.

As shown in FIG. 1, even in a color original image itself to be processed, subsequent processing of image information,
That is, color separation (this term refers to the CMYK
R that is in a complementary color relationship to produce a color print image
This is used in a narrow sense that color information of / G / B is obtained by color separation. ) And tone conversion (this term means to convert and reproduce the gradation of a color original image on a duplicate image, and should be interpreted in a broad sense to include both tone and tone conversions) There are various considerations and issues that need to be considered in order to implement.

As shown in FIG. 1, the image information processing technology applied to all systems for producing a color print image of a final product starting with the submission of a color original image must be systematic. And the image information processing technology, from the viewpoint of the finished tone of the color print image as the final product, from the viewpoint of faithful reproduction of the color original image, as well as rationally incorporating various customer needs, high quality, high image quality, And it must be constructed so that it can be manufactured to match customer needs.

However, to date, it is no exaggeration to say that there is no systematic image information processing technology applied to all systems (total systems) for producing the above-described color print images. . That is, the image information processing technology applied at the time of the conventional color print image production is: image information processing technology of a very limited area in the entire system; It is not an exaggeration to say that when viewed from the viewpoint of the above, they have no organic relationship with each other or the organic relationship is extremely poor.

In connection with the above, even today's expensive image processing equipment (advanced mechatronics equipment), color printing that fully satisfies the desired high quality, high image quality and customer needs. At present, it is not possible to efficiently produce images with regularity, universality, and elasticity using image processing technology that is reasonably integrated with system technology.

Recently, in image information processing technology, a device independent color management system (CMS: Color Management System) has been introduced with the opening of devices, as is finally seen in DTP and the like.
The movement to build is spreading. this is,
With the opening of image information processing devices such as image input devices (image getters) and image output devices (image setters), unified color management is possible regardless of the image processing device used by any manufacturer. (Color management). The construction of the color management (CMS) described above can be said to show one way in view of the fact that the problem of color consistency is an extremely large problem in producing a color print image.

However, the CMS (Color Management System) approach is not well accepted in the market today. Hereinafter, the outline of the CMS approach will be described. However, it should be understood that the difficulty and difficulty in rationally producing a color print image from the approach are described ("Journal of the Printing Society of Japan", Vol. 34, No. 5). , 199
7 years, P320-325).

The CMS provides a function of perceiving an image to be the same to human vision among a plurality of devices (for example, an image input device, a monitor device, and an image output device). Can be defined as The CMS described above has color characteristics (color space, color
This is performed so that the tristimulus values between the original image and the duplicated (reproduced) image match between various devices having different spaces. More specifically, the C
MS methods include scanner (image getter), monitor,
Device values such as CMYK (or RGB) used by each device such as a printer (image setter);
This is a method in which color reproduction is performed by colorimetrically matching the color values that do not depend on the device, such as XYZ, Lab, L (star), a (star), and b (star). In other words, based on the unique color space (color space) of each device (standard)
The color reproduction is intended to be performed by matching the color space. That is, the above-described method handles image data according to color values, and performs device-independent (device-independent) color management (C
M).

In order to convert between the device value and the color value, the color characteristics of each device must be examined and described as data called a device profile. The format of the device profile is ICC (International
l Color Consortium). The IC
C is an organization established in 1993 to realize and standardize a color management system (CMS) in an open environment. ICC members include Kodak, Agfa, Fuji, and Microso
It is made up of the world's leading color image related companies such as ft, Adobe, Apple, etc., and intends to make its standardized specifications substantially the world's standardized specifications (difact standard, world standard).

The device profile of the ICC is:
Known as the ICC profile,
997 ICC Profile Format Specificatoin Vers
ion3.4 has been released and is available for download on the Internet homepage (www.Color.org).

The outline of a color management system (CMS) using the ICC profile is as follows. (1) The system configuration can be roughly divided into:-an image input device such as a scanner or a digital camera;-an image display device such as a monitor;-an image output device such as a printer;-an application unit for processing and correcting images; A system unit (which constitutes a part of the application unit) for performing color management. (2) The device profiles are classified into: an input profile (Input profile), a display profile (Display profile), and an output profile (Output profile), and the respective formats are determined. (3) The color management (CM) is automatically executed when a color processing command is issued in the application unit, while the color management module (CMM) in the system is automatically called.

The color management system (CM)
The CMS in which the original is scanned in S), displayed on the monitor and output by the printer will be specifically described below.

(1). Color management module (C
MM) is the scanner profile, i.
The RGB values obtained by the image information reading mechanism of the scanner are converted into color values L (star) a (star) b (star) using an nput profile). When converting the RGB values into color values L (star) a (star) b (star), a fundamental tool (a fundamental) for the conversion is used.
tool) is ANSI (American National St.
andards Insititute) Standards Comi
ttee IP8. This is a standard manuscript (eg, IP 8.7 / 1 or 7/2) developed by Working Group. Each scanner (each input device) uses the above-mentioned standard original IT8.7 / 1 (transparent original, photographic film original)
Or 7/2 (reflective document) is scanned and input, and the reference color value L (star) a (star) from any document
A scanner profile for obtaining b (star) will be prepared. (2) Next, the color values L (star) a (star) b (star) are converted into RGB values of the monitor by a monitor profile and displayed on the monitor. (3). Furthermore, a printer profile
As a result, the color values L (star) a (star) b (star) are converted into CMYK values of the printer and output on recording paper. By the above-described process, color reproduction by matching of color values, that is, color management (CM) in which color values L (star) a (star) b (star) match are realized.

However, a color management system (CMS) centered on the ICC profile
At present, there is no place to be found in the color-related industry, for example, in the color printing field.
The above-described defects of the color management system (CMS) having the ICC profile as a core can be easily understood from the following points.

(1) A reference (standard) original, for example, a reference transparent original (photo film original, transparency) is easily obtained from Fuji Photo Film (Fuji), Agfa (Agfa), Kodak (EK) or the like. However, these are considerably different from each other visually, and are different from each other even if the color is measured by a colorimeter. This is the current situation in the preparation of the reference manuscript, and the above points must be sufficiently taken into consideration when using the present system. In addition, the present inventor will describe in detail later,
The photographic film photosensitive material used to create the transparency original (transparency original) has a unique photographic (density) characteristic curve (photographic (depth) characteristic depending on the manufacturer.
(nsity) characteristic curve), it is considered that each reference document is also affected by its own photographic characteristic curve, and that the above-mentioned variation among the reference documents can easily occur.

(2). The ICC is a device for producing input profiles (scanner profile generators).
In order to improve the accuracy of MS, for example, the type of light source (for example, D50 with a color temperature of 5000 k) and the measurement conditions (for example, an observation angle of 45 °) are specified. However, these conditions for improving the accuracy are usually extremely limited in view of human visual conditions when a human views a color image (subject, real scene). In other words, it is unlikely that a true color management system (CMS) will be constructed by matching the rich visual sensation of a human to such extremely limited conditions.

(3). The targets (standard manuscripts, ANSI 8.7 / 1, 7/2) recommended by the ICC include three segment patches: (i) dye patches (dye scales), and (ii). A neutral density patch (neutral dye scales) and (iii) a color gamut area (a color gamut area). However, the color information (color information) included in these three elements is extremely limited as a reference for the actual color world. This point is also one of the major limitations of the color management system (CMS) based on the ICC profile.

As mentioned above, the ICC profile approach for a color management system (CMS) starts with the reference targets as a fundamental tool. . However, due to restrictions on this type of target, measurement conditions, and the like, at present, sufficiently satisfactory results have not been obtained among various devices in an open environment such as DTP.

As is apparent from the above description, in color reproduction technology for producing a color print image from a color original image, image information of the color original image that sufficiently reflects human visual characteristics. Processing technology is essential. The approach of the color reproduction method based on the matching of the color values based on the ICC profile using the reference target as a tool is described in human color vision.
It uses only a small part of that physical phenomenon.

A point to be noted in the color reproduction technique is that a human goes through many stages until he or she understands color as a sensation, as described below. In addition, the color reproduction technology must be based on elemental technologies for realizing rational gradation reproducibility and color tone reproducibility sufficiently reflecting these human visual characteristics.

(1) First, light entering the eyeball is converted into an electrical signal by the cone of the retina. At this point, the mechanism relating to the automatic exposure of the human eye works, scaling to the appropriate signal strength and adjusting the sensitivity to color. (2) Next, various processes are added and perceived in the brain through the optic nerve. Among them, there are phenomena such as color averaging by a spatial filter and stereoscopic vision, such as an automatic white balance mechanism for colors and an illusion due to the influence of surrounding colors. Here, problems such as chromatic constancy and chromatic adaptability of human vision intervene. (3) In addition, the colors that humans remember from experience and the environment, for example,
There is a problem with colors stored as preferred colors such as human skin, blue sky, and plants. Note that the above-mentioned memory colors do not match in terms of color values and color appearance, but indicate that a technique for reproducing an acceptable color is required.

As described above, the current color management system (CMS) based on the ICC profile is as follows.
It uses only a small part of physical phenomena in human color perception. The processing mechanism of human visual information is extremely complicated, which is why interdisciplinary research in biology, psychology, information engineering, etc. is required.

[0032]

SUMMARY OF THE INVENTION The present inventor has established an elemental technology which can uniformly solve the above-mentioned problems of color matching and color resilience (color consistency) in producing a reproduced image such as a color print image. Intense and devoted to the study. In the course of this research and development, the inventor
A technology that faithfully reproduces the tone (gradation and color tone) of a continuous tone original image on a duplicate image, and a technology that adjusts (corrects or changes) the tone (gradation and color tone) of the original image to a desired one In the prior art, the tone conversion technique of the image in the density area of the basic image, that is, what percentage of halftone dots should be arranged in order to obtain the same visual density as the density value of the continuous tone image There is no rational support for the image gradation conversion technology based on the basics of image processing, and it has been recognized that it is unscientific and irrational depending on human experience and intuition.

The above-mentioned limitations of the prior art will be described in more detail in terms of producing a color print image. As a device for color separation work for producing a color print image, an advanced color scanner or the like that has been mechatronized is used. However, the element technology in the color separation work, specifically, a color separation technology (RGB color information In particular, the latter two technologies have been systematically constructed and constructed in terms of color separation technology for importing, color correction technology, gradation conversion technology (gradation compression and conversion technology), etc. No, this is a major confusion factor.

More specifically, the color correction technique (co
Although scientific approaches such as the masking equation and Neugebauer equation have been introduced for the lor correction, the above-mentioned gradation conversion technique (which is based on the size of a given pixel in a color original image) This is related to the technology of arranging halftone dots.), Which has been neglected without being supported by a rational theory, and this part greatly depends on human experience and intuition. It's no exaggeration to say that you do.

It is very strange that the above-mentioned gradation conversion technique has become irrational. That is, the representation method of the duplicated image is that the continuous tone of the original image is a halftone tone (non-continuous tone). For example, for a pixel of a predetermined size, The coverage of the pixel (dot area 5) is determined by the size of the dot (dot)
%), (Ii) a method of changing the coverage of the pixel by an arrangement (coarse / dense) of specified dots used in ink jet recording, and (iii) a non-coloring method used in sublimation dye thermal transfer recording. In view of the fact that the method of changing the density of the pixel itself, which is regarded as a continuous arrangement, is employed, and that the color tone must be reproduced under the halftone gradation expression method, From the viewpoint of rational reproducibility, the lack of rationality in the tone conversion technology means that
Very strange.

As described above, in the production technology of a duplicated image such as a color print image, a comprehensive technology that rationalizes the gradation conversion technology and integrates and integrates the color tone reproduction technology has not been established. It is a big problem. The inventor has
As is clear from the above, in the production of a color reproduction image, since the color tone can be expressed only on discontinuous halftone dots or dots subjected to gradation conversion, for example, in the case of a color print image, a predetermined Because color and tone must be reproduced by applying color ink on halftone dots, the primary elemental technology is the rational and regular image gradation conversion technology. Based on this basic idea, we studied to develop rational gradation and color tone conversion technology.

As is apparent from the above description, the present invention provides, for example, a color original image (including a transparent original and a reflective original) in plate making of a color print image as a duplicate image.
In order to produce high quality, high image quality, and color print images that match the needs of customers, we will rationally solve the problem of color reproduction, which is the biggest problem. The purpose of the present invention is to provide a technology for producing a color print image that can meet customer needs (needs for a finished tone of a color print image) even from a color original image, and in particular, a technology for processing image information of a color original image. .

The present inventors have established the following advanced techniques for producing a color print image: (i) a color original image, for example, a color transparent original (which is
The dynamic range of image density information is large and is considered to be indispensable for producing high-quality color printing, and is also called a photographic film original or a transparency original. ) Has what characteristics, and how these characteristics affect the processing of image information (?) (Ii). For color print images, R / G /
B is obtained by obtaining the image information of B and finally converting the image information into C / M / Y image information.
What is the tone conversion method that can rationally realize customer needs as well as the problem of (color management) (?), And what is the essential tone conversion formula applied to the tone conversion? Must have characteristics (performance) (?) (Note: In the present invention, "gradation conversion"
This should be interpreted in a broad sense to include conversion of color tone as well as gradation and density gradation of a color original image. (Iii). The color print image is a halftone dot color plate (C plate, M plate).
Plates, Y plates, etc.) are produced (duplicated). However, the relationship between the halftone dot arrangement and the color development is based on the primary color (each halftone dot of each color plate does not overlap individually). , The secondary color (color development from the area where the halftone dots of the two color plates partially overlap), and the tertiary color (each color of the three color plates) It is extremely complex as seen in the color development phenomenon from the area where the points are completely overlapped. Under such a color development phenomenon, color consistency satisfying the customer has been realized. Investigations have been made that go back to the roots of conventional color print image production techniques, such as what kind of gradation conversion method is better for providing color print images (?).

As a result, the present inventor can produce a reproduced image such as a color print image having excellent reproducibility of gradation and color matching, based on a specific gradation conversion process, with a very high reproducibility. In other words, we have found that a new tone conversion technology with excellent standardization and versatility can be established.

The present invention is a standard for overcoming the limitations of the prior art of gradation conversion technology, color reproduction technology, and color conversion technology in producing a halftone tone duplicate image such as color printing technology. To provide a new gradation conversion technology with excellent versatility and versatility, and in particular, a program with built-in program (ROM type) of standard specifications and general specifications incorporating the new gradation conversion technology.
To provide a system LSI for gradation conversion of an image.

According to the present invention, a high-speed processing type built-in program (ROM) type used as a standard specification and a general-purpose specification when producing a reproduced image of various halftones such as a color print image. , An image gradation conversion system LSI is provided.

[0042]

SUMMARY OF THE INVENTION In general, the present invention provides image information of a document used when producing a halftone tone duplicate image from a continuous tone document image. Embedded image gradation conversion system LS using a gradation conversion program for converting image into halftone gradation
I, wherein the gradation conversion program is configured to store a program for executing the following operation steps for gradation conversion in a ROM built in an LSI, wherein: The present invention relates to a system LSI for tone conversion of a type image. <Work steps for gradation conversion> The original characteristic information stored in the ROM, that is, original image information (referred to as a vertical axis or a D axis) correlated with the density obtained by scanning an original image recorded on a predetermined recording medium, and the original. A density characteristic curve which is a characteristic of the recording medium and indicates a correlation with an image information value (referred to as a horizontal axis or an X axis) correlated with the amount of light incident on the recording medium from a corresponding subject to form an image is used. Obtaining an image information value (X _n ) correlated with the light amount of the corresponding pixel point (n) from an image information value (D _n ) correlated with the density of an arbitrary pixel point (n) on the original image; , 2. Step of converting the image information values (X _n) correlated with the amount of light obtained document image in the manner described above, the tone intensity value with <tonal conversion formula> following (y _n). <Tonal conversion _{formula> y n = y H + [} α (1-10 -k · xn) / (α-β)] ·
(Y _S -y _H) above in <tonal conversion formula>, each symbol means the following; xn: shows the [X _n -X _H]. That is, image information correlated to the quantity of the characteristic curves by using an arbitrary pixel point on the original image the image information values correlated to the concentration of the (n) (D _n) from the obtained corresponding pixel points (n) From the value (X _n ), the image information value (D _H ) correlated with the density of the brightest portion (H portion) on the original image was correlated with the light amount of the corresponding brightest portion obtained through the density characteristic curve. The basic light amount value obtained by subtracting the image information value (X _H ) is shown. y _n: tone intensity value set to the pixels on the reproduced image corresponding to an arbitrary pixel point on the original image (n). y _H : a gradation intensity value preset in the H portion on the duplicate image corresponding to the brightest portion (H portion) on the original image. y _S : A gradation intensity value preset in the S portion on the duplicate image corresponding to the darkest portion (S portion) on the original image. α: surface reflectance of an image expressing medium used to express a duplicate image. β: Numerical value determined by β = 10− ^γ . k: a numerical value determined by k = [γ / (X _S −X _H )]. Here, X _S is an image information value (D _S ) correlated with the density of the darkest portion (S portion) on the original image, and an image information value correlated with the light amount of the corresponding darkest portion obtained through the density characteristic curve. (X _S ). γ: any coefficient.

Hereinafter, the technical structure of the present invention will be described in detail. First, in order to obtain an understanding of the present invention, a gradation conversion technology as a core technology realized by the program is described in a color original in a system LSI for gradation conversion of a program-containing (ROM type) image of the present invention. The following describes an example of a gradation conversion method of image information of a color original when a color print image is produced using a color film original (transparent original) as an image.

The entire system (whole site) for producing the color print image, that is, producing the color print image of the final product starting with the submission of the color original image, as described with reference to FIG. It involves a very large number of complex and diverse elements. For this reason, the present inventor has sought to rationally achieve many issues such as faithful reproduction of gradation, realization of desired gradation, realization of color matching (color management, CM), and realization of advanced customer needs. In
The entire system is divided into several core "places" (subsystems under the total system), and based on the organic relevance of these "places", streamlined image information processing technology in the production of color print images Adopt the approach of The present inventor believes that such an approach is effective not only in producing color print images but also in producing all other monochrome duplicate images and color duplicate images. Then, the present inventor constructs a (ROM type) gradation conversion system LSI for producing duplicated images of various halftone gradations based on the above-mentioned “place” study contents.
Adopt the approach. Therefore, in the following description, emphasis is placed on the description of the above-mentioned "field" which can be generalized and generalized and which is a tool for establishing the "gradation conversion method (means)". And the present invention relates to this “place”
In this study, a "gradation conversion method (means)" having versatility and generality is found from the contents of the study, and this is realized in a system LSI.

FIG. 2 shows an arrangement of the above-mentioned "places" from the viewpoint of image information processing in the entire system for producing a color print image shown in FIG. Hereinafter, the "field of image information processing" shown in FIG. 2 will be outlined and then described in detail.

(1) A "place" for organizing the image information of the color original image (hereinafter, also referred to as a "place" relating to (1)):
The “place” related to this includes a process of setting an H portion (lightest portion) and an S portion (darkest portion) of a color film original (transparent original) image. In this step, first, in order to obtain image information for producing a production color plate (C / M / Y) of a color print image from a predetermined photographic photosensitive material that is a photographing medium of a color film original image, R that is complementary to the color plate
And setting the density range of the color original image on the photographic characteristic curve of the / G / B photosensitive emulsion layer. Needless to say, the photographic density characteristic curve (hereinafter, sometimes referred to as a photographic characteristic curve) of each emulsion layer (R / G / B) depends on the setting of the H portion and the S portion. This defines a dynamic range from the H section to the S section where image information is to be received.

The "field" relating to the above (1) is the influence of the photographic density characteristic curve of the "photographic photosensitive material" which is a photographing (recording) medium for a color film original image. From the viewpoint of giving a distortion to the substrate.).

In the present invention, as a recording medium for the original image, in addition to the above-described photographic photosensitive material, an original image (subject) such as a CCD (Charge Coupled Device), a photoconductor, or a photoconductor used in a digital camera or the like. ) May be any as long as it can photograph and record and hold. What should be emphasized here is that these recording media record original images with their own unique recording characteristics. In other words, when an original image (subject) is recorded on these recording media, the original image (subject) is affected by its characteristics, for example, in the case of a CCD camera, the recording is affected by the characteristics of the CCD (photoelectric conversion characteristic curve). That is to be done. In other words, a document image recorded (photographed) on a predetermined recording (photographing) medium is not a true document image (subject) but is distorted by the characteristics of these recording media. Therefore, when producing a duplicate image having high image quality and high fidelity from a document image recorded (photographed) on a predetermined recording (photographing) medium, image information must be handled with the above points in mind. . In the present invention,
An original image (subject) recorded (photographed) on a predetermined recording (photographing) medium is considered to be of continuous tone. That is, even if an original image is photographed on a photographic photosensitive material (silver salt photosensitive material) or an original image recorded on a CCD of a digital CCD camera, these original images are regarded as having continuous tone. .

A method for removing true image information of the original image (subject) from the color film original image by removing the influence of the characteristics (photographic characteristic curve) of the photographic photosensitive material as the photographing medium will be described below. I do. In the image tone conversion method of the present invention, when using image information from a document image (subject) recorded (photographed) on a predetermined recording (photographing) medium as described above, The use of true image information of a document image (subject) by removing characteristics is one of the major feature points.

As a method for removing the influence of the photographic characteristic curve of the photographic photosensitive material, the photographic characteristic curve itself may be converted into a mathematical expression (function). First, the photographic characteristic curve of the photographic photosensitive material is converted from the image information (vertical axis-D value) correlated with the density of the original image obtained from the color film original image and the subject forming the original image to the photographic photosensitive material. A function expression (photograph characteristic curve) indicating a correlation with an image information value (horizontal axis-X value) correlated with the amount of incident light is defined, and then a photograph as a photographing medium of the color film original (transmission original) image is formed. Using the photographic characteristic curve of the photosensitive material, from the image information correlated with the density of the color film original image, from the H portion (lightest portion) to the S portion (darkest portion) of the original image excluding the characteristics of the photographic photosensitive material. Standardized light value image information, which is image information of all pixels, and is image information correlated with the light amount incident on the photographic photosensitive material from a subject (for example, an actual scene called an apple) which is the source of the color film original image. (standard It suffices to determine the light intensity value). In the present invention,
If the recording (photographing) medium for the original image is not a photographic photosensitive material as described above, for example, a CCD or the like, the photoelectric conversion characteristic curve is converted into a mathematical expression, and the light quantity related information is obtained from the density related information of the CCD. Good. In the present invention, the “density characteristic curve” should be interpreted to include the above-mentioned photoelectric conversion characteristic curve.

Further, the "field" relating to the above (1) indicates that the dynamic range of the light amount image information (standardized light amount) is "1.
00 ”. This point
Details will be described later.

(2) A “place” for designing a processing strategy for the image information obtained in the step (1) (hereinafter, also referred to as a “place” for (2)): "
The R / G / B image information from the arranged color original image obtained from the “place” relating to (1) is subjected to gradation conversion to produce halftone halftone color plates (C / M / Y). It can be said that this is a place for plate making design.

The important work of designing the "place" relating to (2) includes a work of qualitatively and quantitatively designing at least the following four items (i) to (iv). In the present invention, in order to meet the needs of advanced customers, the following (i)
The four items (1) to (4) are characterized in that they are dealt with in the design work as inseparable items. Note that this point will be described later in detail. (i) H part (lightest part) and S part (darkest part) of a color print image
settings of. (ii). Setting of halftone dot values (gradation intensity values of the H and S portions) to be disposed in the H and S portions. (iii). Setting conditions for maintaining gray balance (color balance). (iv) Setting of the adjustment condition of the halftone contrast from the H section to the S section.

(3) In accordance with the processing design specifications determined in the step (2), a “place” (hereinafter, “(field)” for executing the processing of the arranged image information obtained in the step (1). The “place” for (3) is the same as the “place” for (3). The “place” for (3) is obtained by converting the image information of the color original image obtained from the “place” for (1) into While satisfying the determined processing design specifications, each color plate (C / M /
Y) is a tone conversion (conversion of continuous tone to halftone tone, tonal conversion) in order to produce Y), which is an extremely important “field”. Needless to say, the “field” related to (3) includes the determination of what “gradation conversion formula” (or gradation conversion method) is to be adopted in gradation conversion. .

The gradation conversion work in the “place” related to the above (3) is inseparable from the design items in the “place” related to the above (2), specifically, the “place” related to the above (2) ( i) ~
It must be performed using a gradation conversion formula that simultaneously satisfies item (iv). In the present invention, for example, when a color print image is produced from a color original image as a duplicate image, the following <gradation conversion formula> is adopted as the "gradation conversion formula".

[0056] <gradation conversion _{formula> y n = y H + [} α (1-10 -k · xn) / (α-β)] ·
(Y _S -y _H) However, in the above <tonal conversion formula>, each symbol means the following; xn: shows the [X _n -X _H]. That is, the image information value (D) correlated with the density of an arbitrary pixel point (n) on the color original image
_n ), the image information value (X _n ) correlated with the light amount at the corresponding pixel point (n) obtained using the photographic characteristic curve, and correlated with the density of the H portion (lightest portion) on the color original image. The basic light amount value obtained by subtracting the image information value (X _H ) correlated with the light amount of the corresponding H portion (brightest portion) obtained using the photographic characteristic curve from the image information (D _H ) is shown. y _n : A dot% value set for a pixel on a color print image corresponding to an arbitrary pixel point (n) on a color original image. y _H : Halftone dot value preset for the H portion on the color print image corresponding to the H portion (lightest portion) on the color document image. y _s : a dot% value preset for the S portion on the color print image corresponding to the S portion (darkest portion) on the color document image. α: Surface reflectance of printing paper used for color printing. β: Numerical value determined by β = 10− ^γ . k: a numerical value determined by k = [γ / (X _S −X _H )]. Wherein X _S is correlated to the amount of S section corresponding calculated by utilizing the photographic characteristics curve from the S portion of the color original image the image information values correlated with the concentration of (darkest) (D _S) (darkest part) The image information value (X _S ) is shown. γ: any coefficient.

(4) A “place” for applying the image information (image information for gradation conversion) obtained in the step (3) to the production of a color print image (hereinafter, “place” relating to (4)) ): The “field” relating to (4) is based on the gradation conversion information obtained in the step (3), and a dot generator (dot
(C / M / Y) plates used for producing and printing a color print image by a generator.

Hereinafter, the technical structure of the present invention will be described in more detail. Next, the present invention will be described by taking an example of producing a halftone color print image from a color original image as an example of producing a halftone reproduced image. In particular, the content of the "place" that is important for rationalizing the process in producing a duplicate image such as a color print image will be described in detail below. As described above, the present invention provides a
An approach of extracting a generalization and generalization as the most important gradation conversion method (core technology) in the production of a duplicate image, and implementing this as a system LSI is adopted.

As can be seen from the schematic description of each "field" constituting the entire system, the present invention is applied to all processes (all steps) when producing a color print image from a color original image. Technology (for example, acquisition of image information by color scanner or image getter, color separation, gradation conversion, output of halftone gradation image by dot generator or image setter, production and calibration of each color plate, CRT monitor image for check of each color plate) In view of the wide range of output, dot gain adjustment during printing, etc., and the need to respond to diversified customer needs as well as color consistency, the entire system ) Is newly reconstructed, and a new method for rationally producing a color print image from among them is proposed.

The reason for adopting the above-mentioned “field” approach is that the current technology for producing color print images sufficiently solves the problem of color consistency found in the aforementioned color management system (CMS). And the lack of answers to the diversified needs of customers for the quality of color prints, and the challenges these are so great, have led to the development of color print image production techniques to date. The idea is that it needs to be reconsidered.

The present invention divides the entire "field" of the production of a color print image into several "fields" which are closely related to each other as described above, and these "fields" have clear roles and functions. Adopt an approach that shares Then, in each “place”, in order to realize customer needs, an approach that positions each of a variety of complex elemental technologies in each “place” and clarifies the roles and functions that these elemental technologies must share Is adopted. The present invention is based on the concept of the entire "field" described above, and the "field" as a set of several subsystems constituting the field (hereinafter, "field").
There is a concept of "ba" or a concept of "ba". ), It is possible to construct a new technology system that can uniformly and rationally respond to sophisticated and diversified customer needs in a complex and diverse system for producing color print images.

In the whole "place" (all systems) for producing a color print image, in the "place" which handles the color original image at the first stage, the color original image itself has already been given high image quality, high quality, and customer needs. There are hindrance factors, complexity factors, and disturbance factors in producing a corresponding color print image.

As shown in FIG. 1, the obstructive factors, the complex factors, and the disturbance factors in producing a high-quality, high-quality, color print image corresponding to customer needs from the above-described color original image are as follows. It is as follows. (1) Document type (reflective, transmissive, positive, negative) (2) Photosensitive material type (manufacturer brand, brand) (3) Photographic exposure (over / suitable / under) (4). Image quality (high key, low key, normal) (5). Color fog colors (red, green, blue) and their degree (6). Degree of fading (large, medium, small) (7). Color document storage conditions (8) .Other

Among the characteristics of the color original image, some types of photographic photosensitive materials (manufacturers and their brands) are shown below.
It is as follows. EK (Eastman Kodak) Ektachrome 64, Eclachrome Dupe Film 6121, Ektachrome 50 (Professional Film, Tungsten), Ektachrome 200 (Professional Film 3036), Kodachrome 2
5 (professional, tungsten), Ektachrome 200 (professional daylight), etc.
AGFACHROME-1000-R manufactured by AGFA
S, 50-RS, 200-RS, 100-RS, and the like, such as Fujichrome-50 (professional, daylight) and Fujichrome 100 (professional, daylight) manufactured by Fuji Film Co., Ltd.

A color original image having various characteristics described above, for example, a color film original (transmissive, transparen)
It should not be overemphasized that cy) must be dealt with in the first stage of producing a color print image. This is because R / G / B
The image information is obtained, and the corresponding C / M / Y image information (for producing a color plate having a complementary color relationship) is obtained, whereby each color plate (C / M
/ Y or C / M / Y / BL), that is, in view of the fact that the color original image is the origin for obtaining image information.

A color original image having various characteristics described above is submitted to a section (section) for producing a color print image. In such a situation, the present inventor believes that it is necessary to reconsider a `` place '' for obtaining image information from a color original image in order to make the manufacturing process of a color print image rational. thinking. The inventor of the present invention obtains color film originals (transparent originals) when obtaining image information in order to produce high quality, high image quality and color print images meeting customer needs from color original images having various qualities and image qualities. In the case of a (transparency) image, it is necessary to obtain image information in which the influence of the photosensitive characteristic of the color film as the photographing medium is removed (eliminated).

The inventor of the present invention has unified and uniformized image information from color film original images of any quality and quality, and from color film original images photographed using color films of any manufacturers. From the viewpoint of realization, it is considered necessary to obtain image information from which the characteristics of the photographic characteristic curves of the respective color film originals have been removed to the minimum necessary. The inventor of the present invention considers that the image information acquisition attitude described above is an indispensable requirement for realizing unified color management (CM) in the current situation where image processing devices are open. .

In the present invention, as shown in FIG.
The entire system (total "place") that obtains image information from a color original image and performs image processing (color separation and gradation conversion) based on this to produce the final color print image
It is referred to as "a place for image information processing." The “place” where the image information is obtained is referred to as a “place for organizing image information”. Hereinafter, the "place for organizing image information"
Will be described in detail.

The "place for organizing image information" is the first important "place" for producing a color print image from a color film original (transparent original) as shown in FIG. This is a "place" for obtaining image information from.

As shown in FIG. 1, the “place for organizing image information” is as follows: (i) Each R / R of a photographic photosensitive material that is a photographing medium (recording medium) of a color film original (transparent original). G
(Ii) a step of designating the density range (dynamic range) of the color film original on the characteristic curve of the / B photosensitive layer with an H portion (highlight portion, brightest portion) and an S portion (shadow portion, darkest portion); . Obtaining light amount information (value) from density information (value) of the original image using a photographic characteristic curve of the photographic photosensitive material;
(iii) normalizing the light amount information (value) to obtain a normalized light amount information value.

In FIG. 1, the “color separation” positioned after the “place for organizing image information” refers to R / G
An existing information detecting means for separating the R / G / B image information of the original image into C / M / Y image information (signal value) of the copy system using the / B filter, for example, a masking equation or a Neugebauer equation Means existing color correction (color correction) means.

Hereinafter, the "place for organizing image information" will be described in more detail.

In the conventional production of a color print image, image information for gradation conversion of an image (conversion of continuous gradation to halftone gradation) is based on “density information value” (density value). Things. On the other hand, the present invention does not depend on the image quality of a color film original, for example, an over / normal / under-exposed original, a high-key / low-key original, an original with various color fogs, or faded (fading). In order to create color print images of excellent image quality without being affected by the image quality of originals such as originals, the conventional `` density value '' is used as image information for gradation conversion obtained from color film original images. There is a great feature in using the “light amount value” instead.

This is a point that is distinguished from the prior art. In the present invention, the reason why the "light amount value" is used instead of the "density value" of the color original image at the time of gradation conversion is as follows. Even if various color film original images having different image qualities are used together with the use of different photographic photosensitive materials of the above-mentioned various manufacturers, in order to rationally convert the image information of these image originals into gradations, it is necessary to use each color film photosensitive material. The use of a "density value" that depends on (or is affected by) a photographic density characteristic curve inherent in the material is a problem in performing uniform gradation conversion. For this reason, image information “light amount value” from a subject (a literal base of a document image; for example, a real image such as an actual scenery, an actual scenery) incident on the color film photosensitive material at the time of shooting, Then, the photographic density characteristic curve of the color film photosensitive material (the characteristic of the photographic photosensitive material)
Image information that does not depend on (are not affected by)

The above-mentioned image information “light amount value” is obtained by using a characteristic curve of a color photographic film photosensitive material (photosensitive emulsion) on which the original image is photographed, that is, a so-called photographic characteristic curve. It can be easily obtained from photographic desity (density information value).

The photographic density characteristic curve is represented by a DX orthogonal coordinate system in which the vertical axis (D) is the density and the horizontal axis (X) is the exposure. The "light amount value" can be easily obtained from the density information value of the document image by making the photographic density characteristic curve of the color film photosensitive material on which the image document is photographed a function. That is, by determining the function formula of the photographic density characteristic curve, the light amount value (X _n ) of the corresponding pixel point can be obtained from the density value (D _n ) of an arbitrary pixel point (n) in the color original image. it can. Since the photographic density characteristic curve is given as technical data from each photographic material maker, it may be converted into a function.

FIG. 3 shows an example of the photographic density characteristic curve.
Shows the photographic density characteristic curves of Ektachrome 64 manufactured by EK and a professional film (Delight). The method for converting the photographic density characteristic curve into a function is not particularly limited, and may be in accordance with a desired method. Needless to say, as shown in FIG. 3, the respective R / G / B emulsion layers of the color photographic film photosensitive material have their respective characteristic curves. , Corresponding color plate (C /
M / Y) may be obtained. Table 1 below shows the results obtained by converting the photographic density characteristic curve into a function. In Table 1, in order to formulate the photographic density characteristic curve as accurately as possible, the number of formula divisions is plural. It goes without saying that the more the number of sections increases, the more accurate the function expression of the photographic density characteristic curve can be obtained.

[0078]

[Table 1]

In the present invention, when the photographic density characteristic curve shown in FIG. 3 is converted into a function, the photographic density characteristic curve is represented by a scale (scale) on the D axis indicating the density value of the color film original and a log E of the subject (substantial image). D value (density value) with the same scale of the X axis indicating the light amount value
And the X value (light amount value) may be converted into a function. D mentioned above
The scaling with respect to the axis and the X axis is performed from the following viewpoints, and is considered to be quite reasonable by the present inventors. That is, in the photographic density characteristic curve, the logarithmic value of the exposure amount E (log E = logI × t) is positioned on the X axis, and this physical amount is evaluated by the logarithmic discrimination characteristic for the light and darkness of human visual perception. On the other hand, the physical quantity relating to the density on the D axis is also logarithmically evaluated in human vision. Therefore, when correlating the D axis and the X axis, it is considered that there is no unreasonableness even if the scaling is performed under the same scale.
Note that the above-described grading (scaling) is a kind of simple method, and it is needless to say that the present invention is not limited to this. For example, it goes without saying that a function may be formed based on the relationship between the numerical values (actually measured values) shown on the D axis and the X axis shown in FIG.

In the present invention, in view of the relative relationship between the D value and the X value, the physical quantity on the X axis is represented by the exposure (log E =
logI × t).

According to the present invention, as described above,
As in the prior art, the density value (D_n 
Values), rather than the subject (actual image, actual
Image information value given by scenery, that is, represented by X axis
Light intensity value (X_n Value). As described above
In addition, D shown in Table 1 is obtained by functionalizing a photographic density characteristic curve.
_nValue and X_nThe value is correlated with the function of X = F (D)
Because it is easy to D_nX from value_nCan determine the value
You.

Hereinafter, a function of a photographic density characteristic curve of another photographic film is shown. (1) Table 2 shows the function formula of AGFACHROME-1000-RS. (2) Table 3 shows the functional formula of FujiCHROME-50 (Professional D).

[0083]

[Table 2]

[0084]

[Table 3]

Next, the photographic density characteristic curve of a predetermined color photographic film is converted into a function, and the measured data of each pixel point (n) on the color film original photographed on the color photographic film, that is, D _n ( Tables 4 to 6 below show the relationship between the density value) and X _n (light amount value). (1). Table 4 shows KODAK EKTACHROME-64.
Is actual measurement data for a color film original. (2) Table 5 shows actual measurement data of a color film original of AGFA CHROME-100-RS. (3) Table 6 shows actual measurement data of a color film original of FUJI CHROME-100.

[0086]

[Table 4]

[0087]

[Table 5]

[0088]

[Table 6]

In the "field for organizing image information" of the present invention, the image information of a color film original image is obtained from the density value (D _n ) of a predetermined pixel point (n) as the image information of the color film original according to the above-described procedure. The light amount value (X _n ) that is not affected by the characteristics (photographic density characteristic curve) of the (photographic photosensitive material) (the characteristics are removed or “distortion” due to the characteristics is removed) is obtained. The light amount value (X _n ) is more uniform and has less distortion compared with the density value (D _n ) based on the conventional image information processing technology from the viewpoint of the qualitative characteristics of the image information. Standardized image information,
In addition, it can be said that it reflects the substance of the subject (substance image) more accurately. The present invention, the X _n value obtained from D _n value in the manner described above, may be referred to standardize light value.

In the "place for organizing image information" of the present invention, each pixel point (n) in the entire dynamic range from the H portion (brightest portion) to the S portion (darkest portion) of a continuous tone image document. When the image information is relatively compressed, the quality of the image relatively changes, so that there is no problem in processing the image information. For this reason, the “place for organizing image information” sets the dynamic range of the standardized light amount value to 0.00 to 1.0.
This includes processing for compressing the data to 0 [1.00]. It is apparent from Tables 4 to 6 that the dynamic range of the _Xn value is of various values. In the present invention, the process of compressing the dynamic range to “1” is referred to as “normalization”. The normalized (standardized) light amount value is referred to as a normalized light amount value (see FIGS. 1 and 2). It is needless to say that the “normalized” light amount value has a great advantage in image processing, particularly in calculation processing at gradation conversion (operation processing at gradation conversion). is there.

In the image information processing technology for producing a halftone color print image from a continuous tone color film original (transparent original), the image information processing technique must be considered next to the "place for organizing image information". Important "place" must be based on the image information obtained in the process of "arrangement of image information", based on the image information, to consider what kind of color print image to produce, "place", that is, This is a place for plate making design (plate making design).

Image information obtained from the above-mentioned "place for organizing image information" (light intensity information value instead of conventional density information value)
The “place of plate making design (plate making design)” for producing each color plate (C / M / Y) and black plate (BK) using
As shown in the following, the following items must be considered overall and organically.

(1). Setting of the position and halftone dot value of the H portion for the color plate (C / M / Y) (2). The position and halftone dot portion of the S portion for the color plate (C / M / Y) Value setting (3). Setting for black plate (BK) (UCR amount, UCA amount, ST
(P / EDP settings) (4). Related adjustment of gradation conversion and tone conversion (color correction) when setting a tone curve (gradation conversion curve) (gradation conversion first principle) (5). Adjustment considering unnecessary components of process ink when setting tone conversion curve) (Maintaining color balance and gray balance in all ranges) (6). DOT when setting tone curve (gradation conversion curve)
・ Adjustment considering GAIN (7). Adjustment of contrast of halftone (8). Maintenance of gray balance and color balance (9). Reduction and enlargement magnification of finished image (10). S. The amount of M, etc.

[0094] High quality, high image quality, and color print images that meet advanced customer needs can be reasonably (ratinall).
y) In order to manufacture efficiently and with good reproducibility, the above-mentioned items must be considered in plate making design. Less than,
The specific contents of the above various examination items will be described.

The above (1) and (2) are used for producing the color plates (C / M / Y), in which the H portion (highlight portion, brightest portion) and the S portion (shadow portion, darkest portion) of each color plate. Indicates that it is important to set the position and the dot% value (the size of the dot) to be disposed here. The above (3) is a black plate used in combination with a color plate (C / M / Y) (an important plate used from the viewpoint of reproduction of halftone tone, black balance, control of the total amount of halftone dots, etc.). Here is an example of how to design from the viewpoint. In the present invention, it should be understood that the black plate (BK) may not always be required. The UCR is an Under C
color Romoval (under color removal), UCA is Un
der Color Addition (under color addition). In addition, STP / EDP is the start point (Start
point) and the end point (End point).
This means from the halftone dot position to the halftone dot position of the plate.

In the plate making process, setting of a gradation conversion curve (tone curve) is extremely important.
When converting a continuous tone color original image into a halftone dot color print image, the present invention primarily performs tone conversion (conversion of density gradation and gradation of the original). Think important. This is obvious from the viewpoint that the process ink is applied (covered) on the halftone dots formed by the gradation conversion and the gradation and the color tone are reproduced (the color reproduction is performed). It is. Therefore, the present invention should reconsider the conventional color correction (color correction) technology based on the relative (organic) relationship with the entire area (entire dynamic range) of the color print image to be produced. Take the position that there is.

In view of the above-mentioned drawbacks and limitations of a CMS (color management system) based on an ICC profile based on colorimetric values (color values), the present invention provides color correction (color curve) when setting a gradation conversion curve (tone curve). Correction), and the process ink (C ink =
Considering the separation of the process blue ink, M ink = process red ink, and Y ink = process yellow ink) from the ideal color (unnecessary and impure components of each process ink), how to achieve gray balance or Color balance (in other words, color / match,
It emphasizes the position of maintaining color-consistency. The emphasis is placed on utilizing the contents of these studies when setting a gradation conversion curve (tone curve).

As shown in FIG. 1, when setting an important gradation conversion curve (tone curve) in the production of the color print image, other considerations other than those described above include dot gain at the time of printing. (Optical and physical
Dot Gain), color / contrast adjustment of specific color (for example, skin color), specific area (halftone), etc., and related tones, maintaining the overall gray balance and color balance with other areas ,and so on. In relation to the above various considerations, a gradation conversion curve (tone curve) should be set objectively and quantitatively.

In the above-mentioned "place of plate making design (plate making design)", as another consideration, as shown in FIG. (How large a halftone dot should be arranged for a given pixel point depending on the reduction / enlargement magnification) and the amount of USM (unsharp mask) to give Or to set the order.

As is apparent from the above description, the present invention provides a color plate (plate making design) for producing a color print image, which is one of the biggest problems in the color image industry today. CM, color
In order to solve the problem of coincidence and color-consistency, taking into account the characteristics of a halftone dot which is a medium for forming a color image and a process color ink (C / M / Y ink) applied on the halftone dot, In addition, a method of setting a gradation conversion curve (tone curve) so as to maintain a gray balance and a color balance in the entire range (entire dynamic range) of a color print image to be produced is adopted.

As a solution of the color management (CM), as described above, the IC having the same colorimetric value (color value) is used.
A CMS (color management system) using a C profile has been proposed, which is based on a colorimetric value of a color film original (IT8.7 / 1) which is a standard original (reference original). This is a standardization that uses only a part of the color reproduction from the viewpoint of human vision (standa
rdization) as described above. On the other hand, according to the present invention, regardless of the type of printing ink (process ink) that is a color image forming medium (color reproduction medium), these ink characteristics can be converted into a gradation conversion curve ( The tone conversion curve (tone curve) is objectively set so that the gray balance and the color balance are maintained over the entire range (entire dynamic range) of the color print image to be produced, taking into account when setting the tone curve). , Is adopted.

The approach to CM (color management) of the present invention is based on the printing ink (which may be of any type) which is a commercially available color image forming medium (color reproducing medium). Is used, and when the gray balance and the color balance are maintained in the entire range of the color print image (the entire range extending from the H portion to the S portion) that is reproduced for the human visual sense, It is based on the idea that satisfactory colors are reproduced (color reproduction). Therefore, the approach to CM (color management) of the present invention can overcome the limitations of CMS due to the ICC profile.

As can be seen from the above description, the present invention provides a method for setting a gradation conversion curve (tone curve) serving as a work reference curve for converting continuous gradation into halftone gradation. Taking into account the characteristics of the printing ink (process ink), which is the forming medium (color reproduction medium), the gray balance and color in the entire dynamic range of the color print image to be produced (the entire dynamic range from H to S). It is assumed that a <gradation conversion formula> that ensures that the balance is set is adopted. <Tone for setting a gradation conversion curve (tone curve) that overcomes the problem of the CM (color management) and enables production of a high-quality, high-quality, color print image that meets customer needs. The conversion formula> will be described later in detail.

Here, the problem of maintaining the gray balance and the color balance will be described in more detail.
The maintenance of the gray balance and the maintenance of the color balance
This is extremely important for color reproduction (color reproduction). (1). Maintenance of gray balance: three-color process ink (C /
Gray balance is a very important requirement when reproducing a neutral original (M / Y) as a neutral (gray) printed image. (2). Maintaining the color balance: In order to maintain the color balance, a given ratio of the three-color process ink (C / M / Y) is applied to all the pixels (dots,
R / G / B light reflected from the pixel) should be printed to match the color of the color original image. However, since the process ink has an impurity component (because it deviates from the ideal ink), maintaining the above-mentioned color balance is a complicated process.
Usually, a gray balance of the three-color process ink is required to maintain the color balance. And this color balance is along the entire gradation range (along the
In the production of color printed images with different ratios of C / M / Y inks, gray scale as neutral gray (a gray sca)
le) by color separation and printing. As can be seen from the above, the color management (C
In M), it is extremely important that the gray balance and the color balance are maintained over the entire range (full dynamic range) of the color print image to be produced.
The present invention employs a specific <gradation conversion formula> in order to satisfy the above-mentioned requirements, and in addition to maintaining the above-mentioned gray balance and color balance, high quality, high quality, and color printing matched to customer needs. An image can be produced.

In the present invention, the “design place for processing image information”, that is, the “plate making design (plate making)” for producing (plate making) a color plate (C / M / Y) and a black plate (BK). The “place for plate making design” is a “place” for examining various related items that must be considered at the time of plate making design (plate making design), assuming that the above-mentioned specific <gradation conversion formula> is adopted. In other words, in the "design place for processing image information", the consideration of the <gradation conversion formula> itself, which can make use of the examination result of the related item, should also be considered. As for the specific <tone conversion formula>, a "place" to be considered next to the "place for design for image information processing", that is, a "place for execution of image information processing"
Now, the theoretical derivation process and operation will be described in detail.

In the above-mentioned "place for design for processing image information", that is, "place for plate making design (plate making design)", as described above, it is assumed that a specific <gradation conversion formula> is employed. The fact that plate making designs are made from various angles
As described above. The greatest consideration in the above-mentioned "place of plate making design (plate making design)" is a problem of CM, that is, a problem of color management (color consistency). According to the present invention, as described above, the problem of the CM (color management), that is, the problem of the color management (CM) in the entire area (entire dynamic range) of the H section to the S section of the color print image to be produced is described as “ In the case of plate making design (plate making design), it is considered that the gradation conversion curve (tone curve) can be overcome by setting each pixel of the entire dynamic range so that the gray balance and the color balance can be maintained. In this sense,
The CMS (color management system) system of the present invention is completely different from the above-mentioned conventional management system based on matching of colorimetric values using an ICC profile.

Next, specific design contents for achieving CM (color management) in the “place of plate making design (plate making design)” will be described. (1) In the H and S parts of each color plate (C / M / Y), a predetermined printing ink (for example, G
EOS-G, TK Hi-Echo manufactured by Toyo Ink Mfg. Co., Ltd.) is used to set a condition of a dot% value at which a gray balance (color balance) is maintained when multicolor plate making is performed. (2) At a control point of a color plate serving as a predetermined reference, for example, a predetermined control point of a C plate (for example, a part where 50% halftone dots are set, or a part of 1/4 tone of the dynamic range) How large is the halftone dot value of another color plate (M / Y) at the control point relative to the halftone dot value (for example, 50% halftone dot value) provided at the control point of the C plate. Sets whether the gray balance (color balance) is maintained at that time. (3) While utilizing the conditions of (1) and (2) above, each color plate (C /
A gradation conversion curve (tone curve) is set over the entire range from the H section to the S section of (M / Y).

In the present invention, an indispensable tool for setting a gradation conversion curve (tone curve) of each color plate (C / M / Y) using the above conditions (1) and (2) is as follows. Needless to say, it is a <gradation conversion formula>. In the present invention, in order to set the gradation conversion curve (tone curve) of each color plate (C / M / Y) using the <gradation conversion formula>, the conditions (1) and (2) must be satisfied. Besides γ
The value must be set for the purpose, and this will be described in detail in the following description of the <gradation conversion formula>. If the conclusion is taken in advance, the γ value can be rationally calculated by operating the <gradation conversion formula> while utilizing the above-described conditions. Note that the γ
The value is k value (k = γ / [density area of color original image] = γ
/ [Light amount range of color original image]), β value (β = 10
^-γ ), which is an extremely important parameter in the operation of the <gradation conversion formula>.

The conditions for maintaining the gray balance (color balance) under the desired printing ink (process ink) will be further described. (1). The halftone dot values to be arranged in the H portion and the S portion of each color plate (C / M / Y) are, for example, 5% in the H portion of the C plate and 95% in the S portion.
And 3% in the H section and 90% in the S section of the other M and Y versions
Should be arranged. Naturally, these conditions should be changed depending on the printing ink (process ink) used.

(2). As a control point in the plate making design of the C plate, in the production of a halftone color print image, a dot% value =
Since the pixel point at 50% is a very important part in reproducing the tone of the image (including both the gradation and the color tone), the part with halftone dot value = 50% is used as the control point. It is preferable to set. Note that the control point of the halftone dot value = 50% is about 1% of the density of the dynamic range of the H part to the S part.
/ 4 (quarter tone), which is extremely important in visual evaluation of a color printed image in order to observe the tone reproducibility of the image. The above-mentioned quarter tone portion is a halftone region of an image, and in the present invention, may be referred to as (halftone portion) (M). In the present invention, the site of the control point can be arbitrarily set to a desired site.

When the control point (halftone) (M) of the C plate is set at a portion where the halftone dot of the C plate is 50%, the M plate / Y of the control point (M) under a certain printing ink is used. Gray balance (color balance) can be maintained by setting 40% halftone dots on the plate. At the control point (M), the M plate and the Y plate maintain the gray balun (color balance) when they have the same halftone dot value (40%). Both values for maintaining the gray balance (color balance) may be different values, for example, 40% for the M plate and 38% for the Y plate.

By setting the conditions (1) and (2), the γ value of the <tone conversion formula> can be obtained. For example, in the case of the C version, y _n = 50 (%) (the halftone dot%
Values), y _H = 5%, y _s = 95%, and x _n values, a light amount value (normalized light amount value) obtained from a halftone (M) density value of a color original image using a photographic density characteristic curve. ), Α = 1.
0, β = 10 ^−γ , and k = −γ in the above <gradation conversion formula>
Γ value can be obtained by substituting into γ. For example, the value can be obtained as γ = 0.45. Also,
Other color plate, gamma value of M / Y _{version, y n = 40 (%)} ( dot% values arranged in halftone _{M), y H = 3%} , values such as y _s = 90% For example, a value of γ = 0.168 can be obtained.

By using the γ value for the C plate and the γ value for the M / Y plate, the gradation conversion for each color plate for maintaining the gray balance (color balance) in the entire range from the H section to the S section. A curve (tone curve) can be set rationally. In the present invention, the control point (M) of the C plate is used.
1 point (1/4 quarter tone, halftone)
However, when it is desired to maintain the gray balance (color balance) at a high level over the entire dynamic range, two or more control points may be provided. In the plurality of control points (M), the operation division of the <gradation conversion formula> is set to the number of control points (M) so that the halftone dot value set at the control point (M) is obtained. What is necessary is just to classify and operate according to.

The advantages of setting the two or more management points (M) are as follows. In a halftone dot color print image, in a region where the halftone dots are small, the halftone dots of each color plate become a primary color developing region that does not overlap each other, and a region where the halftone dots are larger than the above-mentioned region. In this case, each color plate becomes a color region of a secondary color that overlaps with each other, and in a region where the halftone dot is larger than the above-mentioned region, each color plate becomes a color region of a tertiary color that completely overlaps. This is because the coloring phenomenon differs. In consideration of these points, in order to execute a more advanced CM (color management), it is preferable to set a plurality of management points (M) and perform the CM (color management).

Table 7 below summarizes the conditions for maintaining the gray balance (color balance) realized under the above-mentioned predetermined printing ink (process ink).

[0116]

[Table 7]

As shown in FIG. 1 and as described above, items to be considered in the “place of plate making design (plate making design)” include items other than the items related to the CM (color management). Although there are various types, the contents of the examination for these items can be rationally used at the time of setting a gradation conversion curve (tone curve) due to the characteristics of the <gradation conversion formula>.

Next, the "place for executing image information processing" following the "place for plate making design (plate making design)" will be described (see FIG. 1). First, a description will be given of the <gradation conversion formula> used in the "place for executing image information processing", particularly its guiding process and characteristics.

The <gradation conversion formula> is derived based on a density formula (photo density, optical density) expressed by the following formula (1). D = logIo / I = log1 / T (1) where Io = incident amount, I = reflected light amount or transmitted light amount, T
= I / Io = reflectance or transmittance. Now, let the pixel area of a predetermined pixel point (n) be 1.0 (regardless of the area unit), α be the surface reflectance of the printing paper, and β be the surface reflectance of the printing ink. Is the dot% value (y _n )
When (for example, 5%, the halftone dot percentage value, such as 10%) was printed, the concentration of the pixel point (n) (D _n) is calculated by the following equation (2). D = logIo / I = log { α / [α (1-y n) + β · y n]} ...... (2)

From the above equation (2), the halftone dot value (y _n ) is
It can be obtained by (3). _{y n = [α / α-} β)] (1-10 -Dn) ................................. (3) the formula (3) in the base color for formula (3) The following conditions required for producing a print image: (1) A predetermined halftone dot value can be set in an H portion (highlight portion) and an S portion (shadow portion); (2). The density area of the original image and the density area of the print image (gradation expression area) are diverged, but the compression of the gradation is rational so that this is evaluated as natural for human vision. (3) Along with the above-described gradation compression,
Formulas that reflect the demands of plate-making practice to be able to change the tone (including both gradation and color tone) rationally and that the theoretical values and measured data match
By modifying (3), the following equation (4) can be obtained. _{y n = y H + [α} (1-10 -k · Dn) / α-β)] (y s -y H) ...... (4) In Formula _{(4), y H, y} s, k is It means the following: (1) .y _H is a dot% value (for example,
When 5% halftone dots are set in the H portion of the C plane, y _H = 5. ) (2) .y _s is dot% values are preset in the S portion (e.g.,
When 95% of halftone dots are set in the S portion of the C version, y _s = 95. (3). K is a numerical value determined by k = [γ / (density area of color original image)]. Although the γ value for determining the k value is an arbitrary numerical value, it is a numerical value for determining the β value by β = 10 ^−γ .
The γ value is, for example, a solid density value of printing ink (solid
When taking the numerical value of density), the β value indicates the surface reflectance of the printing ink. At this time, since D _n = solid density value of printing ink = density range of color original image, k · D _n = γ by definition.

In the above equation (4), when the basic density value obtained by subtracting the density value of the H part pixel from the density value of the predetermined pixel is used as the D _n value, and a value of α = 1.0 is used. In this case, the predetermined y as set in advance in the H section and the S section
_H value, it is possible to set the y _s value. This is based on the above (1)
The answer to the request. That is, in H section, since the D _n = (density value of the density values -H portion of the H portion) = 0 by definition, equation (4) becomes y _n = y _H. In the S part, D _n = (the density value of the S part−the density value of the H part) by definition.
= Since the (color density region of the original image), -k · D _n
=-Gamma, and the addition beta = 10 ^- since it is ^gamma, the formula (4)
Becomes y _n = y _s.

According to the present invention, as described in detail in the above-mentioned "Scene for organizing image information", the light intensity value (D _n ) is not used as the image information value of the predetermined pixel point (n). X _n ). Therefore, when D _n → X _n is changed in equation (4), the above-mentioned <gradation conversion equation> is obtained. Wherein <tonal conversion formula> is conventional density value as the image information value but is intended to employ the light value instead of the (D _n) to (X _n), it can be adapted to various requirements for making practices described above are It has been recognized that the theory (operation of <gradation conversion formula>) and the practice match in many plate-making practices.

[0123] The output data obtained by operating the <tonal conversion formula>, the horizontal axis (X axis) to the light quantity value (xn), if the vertical axis shown by taking the tone intensity value (y _n) to Needless to say, this is what is generally called "color separation curve" or "gradation conversion curve (tone curve)" in the art.

Here, the difference between the prior art gradation conversion method and the gradation conversion method employed in the present invention will be described using the term "color separation curve". (1) Since the conventional color separation method is performed based on the density information value positioned on the density axis (D axis) of the photographic density characteristic curve as described above, the color separation depending on the D axis color separation curve is performed. It can be called a law. (2) On the other hand, since the color separation method of the present invention is based on the light amount information value positioned on the light amount value (X axis) of the photographic density characteristic curve, it depends on the X axis color separation curve. It can be said that this is a color separation method.

Next, the operational characteristics of the <gradation conversion formula> employed by the present invention will be described. Multicolor (C / M /
Y) In the case of plate making, y _H and y _s are generally constant values (constant values) as described above. For example, in the case of the plate C, 5% is _added to y _CH of the C plate, 95% to y _CS , In the M and Y versions, 3% is set in y _MH = y _YH and 90% is set in y _MS = y _YS . In the operation of the <gradation conversion formula>, the (xn) value obtained in relation to the (D _n ) value measured by a densitometer is used, and y _H and y _s are represented by percentage values (%).
With value), y _n value is also calculated as a percentage figure (% value).

In the operation of the <tone conversion formula>, the γ value as another parameter takes an arbitrary value as described above. For example, the X-axis color separation curve for the C plane (tone conversion) Curve, tone curve) setting, γ value =
It may be fixed at a value of 0.45 (it can be used as a default value). Many experiments by the present inventors have confirmed that a high quality and high quality color print image can be produced even when the γ value is set to 0.45.

However, the γ value as a parameter can appropriately change the shape of the X-axis color separation curve. In other words, by operating the γ value appropriately, the desired gradation characteristic ( (Including color tones), which is a very important parameter and is not fixed to the above-mentioned value. The numerical value setting of the parameter of the <gradation conversion formula> is based on the standpoint of reproducing the tone of a given subject (substantial image) faithfully on a color print image, and consciously adjusting the tone (correcting the tone). Is changed) depending on the standpoint of producing the changed color print image. In the latter case,
By appropriately changing the γ value, the shape of the X-axis color separation curve can be changed purposefully so that a color print image having a desired gradation can be produced. (Color tone) can be produced. For example, when it is desired to make the shape of the X-axis color separation curve convex upward (in other words, when it is desired to emphasize the tone from the H portion to the halftone), the γ value is set to a positive value larger than 0, and is substantially linear. (In other words, when the density is linear over the entire range), the γ value approaches 0, and conversely, when it is desired to have a concave shape (in other words, when it is desired to emphasize the tone of the halftone to the shadow portion) ) May be a negative value of the γ value.

Next, other parameters of the <gradation conversion formula> will be described.
Α value (the surface of the printing paper
(Reflectance) will be described. For the β value,
As described above. In the present invention, α value = 1.0
May be set. In other words, α value = 1.0
May be. This is to represent a color print image
100% surface reflectance of printing paper (substrate) used
It was done. α value varies depending on the type of printing paper.
However, in practice, to adjust the whiteness of paper to zero point
There is no inconvenience even if 1.0 is set. Modification (α =
1.0), the brightest portion H on the print image is y_HThe most
Dark part y_sCan be set as planned.
This is a significant feature of the <gradation conversion formula>. Previous
What has been described is that in the brightest part H on the print image, the definition
Xn = (X_n-X_H) = 0 and the darkest part
In S, xn = X _s-X_HsThat is, -kx
n = −γ · (X_s-X_H) / (X_s-X_H) =-Γ
It is clear from this. Thus, under α value = 1.0
By using the <gradation conversion formula> in
Y_HAnd y_sTo the H and S parts on the color print image
This can be set by the prepress operator
This is extremely important when considering the results. For example,
Y in color print image_HAnd y_sTo the desired value (dot%
Value) to change the γ value for the purpose (however,
α = 1.0), various X-axis color separation curves are obtained. So
The color produced under these X-axis color separation curves
-Evaluate printed images rationally in relation to γ value
be able to.

A particularly important point in plate making practice is that
The X-axis color separation curve (gradation conversion curve, tone curve) obtained by using the gradation conversion formula> is different from the conventional D-axis color separation curve, and reaches H to S of the printed image as the final product. The point is that gradation characteristics and tone characteristics are displayed.
Therefore, prepress operator, given y _H, through consideration of the y _s and γ values X axis color separation curve shape obtained under eligibility predicts finish of the final printed image (tone) be able to. This is because, even when gradation conversion is performed on a plurality of color original images having different image qualities (for example, different exposure conditions), the X-axis color separation curves set for each color original image are all one. This is due to the great feature of the gradation conversion method of the present invention that the color conversion curves converge. In contrast, (adopting the same y _H, y _s and γ values.) Conventional D axis color separation curve, the number of D axis color separation curves corresponding to different respective color original image of quality And their curved shapes are complex. Therefore, the plate-making operator is required to
The quality and image quality of the final color print image cannot be predicted properly only by considering the axial color separation curve. The meaning of the above is extremely important. Under the X-axis color separation curve according to the present invention, a plate-making operator can calculate the X-axis color separation curves of each color plate (C, M, Y) and black plate (B) by: For example, by displaying on a monitor, the finish of the final print image can be accurately predicted, so that various calibration operations can be made unnecessary.
In other words, the present invention enables direct plate making (direct plate making method).

In the operation of the <tone conversion formula>, the k value may be normalized so as to be the γ value, that is, the (X _s -X _H ) value may be 1.0. . Thus X
The dynamic range of _H to X _S from 0.00 to 1.00 =
When normalized to 1.00, it is easy to compare and examine a plurality of X-axis color separation curves, and the above-mentioned <tone conversion formula> by a computer or the like of a tone conversion unit of a color print image production device. Is extremely easy (high-speed processing). Naturally, the basic light amount value (xn) of each pixel point (n) within the dynamic range changes due to the above-described normalization, but it is a relative change, and does not hinder the setting of the color separation curve. is not. The normalized basic light intensity value (xn) is referred to as a normalized light intensity value in the present invention. In the following description, the calculation of y _n value is obtained by calculation using the value after normalization.

The “place for executing image information processing” is a multi-color plate making (generally, C
The four editions of the edition, the M edition, the Y edition, and the BK (Sumi) edition are considered as one set. This is a “place” for producing each color plate and black ink plate for). The setting of the gradation conversion curve (X-axis color separation curve) for producing each of these color plates and black plates is performed by the color plate (C
/ M / Y) and black plate (BK) according to the contents determined in the “place of plate making design (plate making design)”, for example, according to the condition setting for maintaining the gray balance and the color balance in the entire dynamic range. A tone conversion curve (X-axis color separation curve) may be set.

That is, the above-mentioned "place for executing image information processing"
Is the light amount value obtained from the image information of the color image of the continuous tone color while utilizing the contents of the examination items determined in the "place of plate making design (plate making design)" in the operation of the <gradation conversion formula>. (normalized light intensity value, xn) the halftone gradation image data value (dot% value, y _n) is a "place" for the tone conversion into. In this “field”, X instead of the conventional D-axis color separation curve
An axis color separation curve (gradation conversion curve, tone curve) is obtained, and each color plate (printing plate) (C / M / Y) and black plate (BK) are manufactured according to the tone curve.

Each color plate (printing plate) and black plate (BK) for producing a color print image by using the above <gradation conversion formula>
As a method of producing the, an existing system known in the art may be used. For example, commercially available electronic color separation devices (color scanners, total scanners)
It is only necessary to incorporate a ROM-type image gradation conversion system LSI that operates (calculates) the <tone conversion formula> in the gradation conversion unit. More specifically, a small spot light is irradiated on a color film original (medium image) of continuous tone, and the reflected light or transmitted light (image information signal) is converted into a photoelectric conversion unit (photomultiplier or CCD light receiving unit). ) To convert the intensity of light into the intensity of voltage, digitize the obtained image information electric signal (voltage value), perform high-speed processing by the image gradation conversion system LSI, and output. Controlling the light source light for exposure of the dot generator (dot generator) using the tone conversion data, and applying a laser spot light to the raw film to create a halftone printing original plate (printing plate). A known system may be used.

As described above, in the present invention, a color-printed image is taken as an example of the production of a duplicate image, and the system LS for gradation conversion of a program built-in type (ROM type) image of the present invention is used.
I has described in particular the method of converting the tone of image information of a color original image, which is a core technical means thereof. The tone conversion method, which is the core technical means of the present invention, introduces the concept of “field”, which is not found in the prior art, and clarifies the roles of the functions of each “field”. It is to produce color print images reasonably and efficiently, and at that time, CM (color management) such as color-consistency, which is the biggest problem in producing color print images, is rational. It can be accomplished.

However, the present invention is not limited to the color print image described above as an example of producing a duplicate image for the following reason. As is well known, various methods are known for expressing pixels of halftone (halftone) gradation. For example, a method of changing the pixel coverage by the size of a dot (also called a size modulation method).
This method is found in monochrome and color scanners for producing printed images, piezoelectric inkjets, and the like. ), Or a method of changing the pixel coverage by a prescribed (same size) number of dot arrangements (dot density) (also called a density modulation method. This method is found in thermal fusion transfer, etc.), and further. A method of changing the density of a prescribed (same size) dot itself (also referred to as a direct density modulation method. This method is found in thermal sublimation transfer. In addition, a CRT or liquid crystal that forms a pixel by adjusting the luminance of the pixel is used. Composed T
V receivers are also included in this category. ).

The present invention is useful when producing a duplicate image by employing the above-described various pixel expression methods. That is, the present invention is applicable to all devices having a function of producing a color or monochrome duplicate image by a copying device, a printer device, a plate-making device, an image transmission device, a TV imaging device, an electronic camera device, and the like. Can be done.

In the case of producing a duplicate image by employing the above-described various pixel expression methods, the yn value obtained by the arithmetic processing of the <tone conversion equation> of the image tone conversion system LSI of the present invention ( It is necessary to produce a duplicate image in accordance with a gradation display method (variable dot method, constant dot method, variable density dot) or a luminance display method suitable for each image forming apparatus. Needless to say.

The greatest feature of the present invention resides in a color separation technique incorporating a function of converting a gradation (gradation) and a function of adjusting a color tone (color tone) in a gradation conversion section. The feature will be described below. The present invention relates to various color or monochrome original images, that is, various types of color or monochrome original images in which a subject (substantial image) is recorded on a desired recording medium using an information transmission medium such as light or electromagnetic waves, photographed, or image-converted. Images (medium images) can be used. Examples of the recording medium for the image original include a transmission type color film (photosensitive emulsion), a photoelectric conversion element such as a two-dimensional CCD and a photodiode, an optical disk and a porcelain disk. It goes without saying that a reflection original such as a painting or a color print can be used as an original image in addition to a film original (transparent original).

In each of the above-mentioned various recording media, in order to obtain the light amount value from the density information value, a characteristic curve of the recording medium, for example, a photographic density characteristic curve or a photoelectric conversion characteristic curve may be used. In the case of a reflection original such as a picture or a color print, the characteristic curve is treated as having a linear relationship between the density information value and the light amount value of 1: 1 (corresponding with a 45 ° linear relationship). It is needless to say that.

According to the present invention, in various recording media such as a photodiode and a CCD constituting the above-mentioned recording medium system, by defining a unique density characteristic curve (or light quantity conversion characteristic curve) possessed by these recording media. It is possible to provide a high value-added image forming apparatus based on the performance of an existing recording medium. In other words, by using these existing recording media, it is possible to produce a color duplicate image having much better tone (density gradation and color tone) than before.
In the art, efforts are being made to improve the characteristics (photosensitive characteristics and photoelectric conversion characteristics) of various recording media in order to produce high-quality color reproduction images (for example, to increase the dynamic range and to improve the characteristic curve). Linearity, etc.). However, when producing a high-quality duplicate image according to the present invention, as is apparent from the above description, it is not always necessary to upgrade the recording medium and improve the performance, and it is necessary to obtain (determine) the characteristic curve of the recording medium. The existing performance (characteristics) is sufficient. This is based on the tone conversion technology that is the core of the present invention, and is another major feature of the present invention.

[0141]

Next, the present invention will be described in more detail with reference to examples. Hereinafter, first, as an example of producing a duplicate image, a color print image is taken as an example, and the program built-in type (RO
In an M-type image gradation conversion system LSI, the gray balance (color balance) is maintained over the entire dynamic range which is the center of the image gradation conversion work.
Tone conversion curve (tone curve, color separation curve) that can easily perform CM (color management)
A setting example will be described. Next, the system LS for gradation conversion of a program-containing (ROM type) image of the present invention.
The configuration of I will be described with reference to the drawings.

(Example 1) (Setting method of gradation conversion curve): (1) Regarding color film original image and photographic density characteristic curve of the color film: Color film original image (transparent original) manufactured by Company F The following three types of images were taken using a photosensitive material film (FUJI CHROME, manufactured by Fuji Corporation). The reasons for selecting the above three types of color film original images are as follows. The image quality of a color film original image (medium image) varies widely, such as a standard image (appropriate exposure) and a non-standard image (over / under exposure) depending on the exposure conditions at the time of photographing.
In order to verify whether or not the present invention can reasonably cope with these various color film originals, a color film original having a different density range (Density Range = DR) (D-axis density range) Are different). (a). Density range (dynamic range) D =
0.18 to 2.70 (bright original, overexposed) (b). Density range (dynamic range) of original image D =
0.30 to 2.80 (normal original, exposure correction) (c). Density range (dynamic range) D =
0.60-3.10 (dark original, underexposure)

FIG. 4 shows a photographic density characteristic curve of the photosensitive material film manufactured by Company F. Further, a function formula indicating a correlation between the D value (density value) and the X value (light amount value) of the photographic density characteristic curve is shown in Table 8 below.

[0144]

[Table 8]

(2). Conditions for setting gradation conversion curves (tone curve and X-axis color separation curve): Various types of functions are used by using the photographic density characteristic curve in FIG. D _n the value X on the D-axis of the color film original image
The light quantity value (standard value) is obtained by converting the value into an _Xn value on the axis, and the normalized light quantity value (xn) is obtained by normalizing this. Next, the xn value was converted to a dot area% value (y _n value) by a <gradation conversion formula>.

The operation conditions of the <gradation conversion formula> are as follows. (i) Under the printing ink (process ink) used,
<Gray balance (color balance) maintenance condition> in Table 7 was adopted as the condition for maintaining the gray balance (color balance) at the control point (the part where the 50% halftone dot of the C plate is set). (ii). Other operating conditions are as follows. . The γ value of each color plate to satisfy the <gray balance (color balance) maintaining condition> in Table 7 is γ (C) =
0.45 and γ (M / Y) = 0.168. In this embodiment, in addition to the color plate (C / M / Y), a black plate (BK) was also created. This black plate (BK) is the dot 5 of the C plate.
It was set so that 0% of the area was defined as the starting point (STP) and 95% of the C-plated area was defined as the end point (EDP). The γ value for the black plate (BK) was set to γ (BK) = − 0.50. . The α value was set to 1.0.

(3) Regarding the data for setting the gradation conversion curve (tone curve, X-axis color separation curve): Under the operating conditions of the <gradation conversion formula>, the above three types of color film original images Was subjected to gradation conversion to obtain gradation conversion curve setting data. The results are shown in Tables 9, 10 and 11 below.

[0148] In Table 9 to Table 11 below, the tone intensity value (y _n) is shown as a color plates dot% value of (C / M / Y) and black plate (BK). Further, in the table, the normalized light intensity value (xn) is to standardize light value dynamic range _{(DR) (X s -X H} ) of (xn) was determined by normalizing to 1.0. When the standardized light value (X _n ) is converted into the normalized light value (xn), k = γ / (X _S −X _H ) = 1/1 = 1 in the operation of the <gradation conversion formula>.
, And the calculation load is greatly reduced. Even if the DR of the standardized light amount value (X _n ) is adjusted to 1.0, the gradation intensity value (y) set at each pixel point (n point) also changes relative to each other, so that color printing is performed. It does not adversely affect the image quality. The following equation may be used to determine the normalized light value (xn) from the standardized light value ( _Xn ). _{(Xn) = (X n -X} H) × [(DR Adjustment range) /
(X _S -X _H)] For Table 9, the formula for determining the normalized light intensity value from normalized light intensity values (X _n) the (xn) is a following equation. ( _Xn ) = ( _Xn− 1.02) × [1 / (2.85-1.02)] = ( _Xn− 1.02) × (1 / 1.83)

[0149]

[Table 9]

[0150]

[Table 10]

[0151]

[Table 11]

[0152] In the present invention, the table is normalized light intensity value indicated in 9 Table 11 (xn) dot percentage data (y _n) is to be seen if graphed, the color film original image Whatever the image quality (in the above case,
Exposure over / normal / under. ), The surprising fact that the gradation conversion curves (tone curve, X-axis color separation curve) fit into one thing. On the other hand, a conventional D-axis color separation curve (a curve showing the relationship between the density value and the dot% value in Tables 9 to 11)
Can be understood as curves corresponding to each other and a complicated curve. The usefulness of the facts described above in plate making is important in plate making, and the person making plate making needs to know how the color printed image as the final product to be made by the gradation conversion curve (X-axis color separation curve) of the present invention. It is possible to consider in advance whether the tone has a proper tone (gradation and color tone).
However, the above cannot be performed under the conventional D-axis color separation curve.

In the prepress operation using the <gradation conversion formula>, it is possible to produce a high quality and high quality color print image in which the gray balance and the color balance are maintained by the entire dynamic range. That is, the inventor of the present invention has found that 455 and 405D manufactured by ISOMET of the United States, which are known in the art as high-end (meaning producing high-quality printed images) and low-end color scanners.
An experiment was conducted in which the concept of the “place” of the present invention was incorporated into IGTAL COLOR SCANNER to make a plate.

More specifically, in the color scanner, software for obtaining a light amount value (X _n ) from a density value (D _n ) is incorporated in a density detection unit, and a control of an image processing control unit (control unit) is performed. The panel allows the user to instruct the contents of the plate making design (design), and incorporates software capable of operating the <gradation conversion formula> in the gradation conversion unit that operates based on the instruction. M /
Y / BK) was output, and the printing plate was proof-printed to confirm the effects of the present invention. As a result, it was found that the gradation conversion method of the present invention produces a high-quality, high-quality color print image that meets customer needs, regardless of the image quality of the color original image. In addition, the produced color print image has excellent gray balance / color balance over the entire dynamic range,
The present invention has been found to be an important tool in CM (color management).

In the plate making operation, (1) the density detecting section is to share the function of the “place for organizing image information”, and (2) the image processing control section (control section)
Needless to say, (3). The gradation conversion section performs the function sharing of the "place for executing the processing of image information". There is no such thing.

(Embodiment 2) (Configuration of ROM-type image gradation conversion system LSI): FIG. 5 shows a program-contained (ROM-type) image gradation conversion system LS of the present invention.
It is a block diagram of I (1). System LSI of the present invention
(1) As shown in the figure, a microprocessor (arithmetic processing unit, MPU) (11), an R including a program for executing the following <work steps for gradation conversion>
It comprises an OM (12) and a read path (13) connecting the microprocessor (11) and the ROM (12).

<Work steps for gradation conversion> The original characteristic information stored in the ROM, that is, original image information (referred to as a vertical axis or a D axis) correlated with the density obtained by scanning an original image recorded on a predetermined recording medium, and the original. A density characteristic curve which is a characteristic of the recording medium and indicates a correlation with an image information value (referred to as a horizontal axis or an X axis) correlated with the amount of light incident on the recording medium from a corresponding subject to form an image is used. Obtaining an image information value (X _n ) correlated with the light amount of the corresponding pixel point (n) from an image information value (D _n ) correlated with the density of an arbitrary pixel point (n) on the original image; , 2. Step of converting the correlation image information value to the amount of the obtained original image as described above the (X _n), said the tone intensity value (y _n) using the <tonal conversion formula>.

The program built-in type (R) shown in FIG.
The continuous tone of a document image such as a color film document is converted at high speed into a halftone dot tone by a system LSI (1) for tone conversion of an OM) type image.

FIG. 6 shows a program built-in type (RO) of the present invention.
FIG. 16 is a block diagram of a gradation conversion system LSI (1) for another image (M type), which is a modified example of the one shown in FIG. The system LSI (1) shown in FIG.
What is different from the one shown in (1) is that when a bug (error) is found in the built-in program (12) stored in ROM,
Having a "change program storage RAM" (14) for using a "conversion program" instead of an erroneous program; (ii). A mistake bus connecting the RAM (14) and the microprocessor (11); (15), and the other configurations are substantially the same.

[0160]

According to the present invention, in a process of producing a duplicate image such as a halftone color print image from a continuous tone color original image, the continuous tone of the original image is a core technical element thereof. The present invention relates to a program-incorporated (ROM type) image gradation conversion system LSI for converting to a halftone gradation at high speed.

In particular, the present invention is directed to a disadvantage of the conventional method of processing image information in producing a halftone reproduced image such as a color print image, that is, the color problem which is regarded as the biggest problem. In view of the fact that the management (CM) has not been solved with sufficient satisfaction, not only the solution of the color management (CM) but also the image information processing technology of the color original image at the time of producing a duplicate image such as a conventional color print image. In addition to generalizing (generalizing), it is intended to speed up the gradation conversion processing of an image which is the core of the generalization.

The present invention relates to a method of processing image information of a document image applied to the production of a duplicate image such as a color print image, and more particularly to a gradation conversion method for converting continuous gradation of a document image to halftone gradation. In, all systems related to the processing of image information (whole "places") are divided into several "places" whose functions or roles are clearly different, and each "place" specialized for such functions We have studied the processing method of image information in each field and integrated the processing method of the image information of each "field". Can be converted.

The tone conversion system LSI of a program built-in type (ROM type) image of the present invention, in particular, is a tone conversion of image information for converting a continuous tone of an original document image which is a core thereof into a halftone tone. Since the method is integrated and constructed based on the concept of the above-mentioned "field", it is extremely useful in the production of various duplicate images as a general technology (general-purpose technology) without being limited to the production of color print images. It is. Further, the present invention can eliminate opacity and ambiguity in image information processing in all processes relating to processing of image information at the time of producing a duplicate image. For this reason, the present invention can convert the color separation technology located at the beginning of the image information processing system (entire “field”) into a system component technology that is rational and regular. Can be streamlined.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the complexity of a color separation technique when producing a color print image.

FIG. 2 is a workflow diagram of image information processing according to the present invention.

FIG. 3 is a diagram showing a photographic density characteristic curve of a color film manufactured by EK.

FIG. 4 is a view showing a photographic density characteristic curve of a color film manufactured by Company F.

FIG. 5 is a ROM-type image gradation conversion system LSI.
It is a block diagram of.

FIG. 6 is a system LSI for gradation conversion of a ROM-type image.
It is another block diagram of.

[Explanation of symbols]

 1… System LSI 11… Microprocessor 12… ROM 14… RAM

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C262 AA29 AB07 AB11 AC02 AC05 BA02 BB03 BC10 BC11 GA12 5B057 AA11 BA02 CA01 CA02 CA08 CA12 CA16 CB01 CB02 CB07 CB12 CB16 CC01 CE13 CE17 CE18 CH01 CH07 CH08 CH11 DA17 DB02 DB05 DB06 DB06 DC25 5C077 LL17 LL18 MP08 NN04 NN06 PP15 PP33 PP38 PP52 PP53 PP74 PQ12 PQ22

Claims (3)

[Claims] 1. A gradation conversion program for converting image information of a document used when producing a halftone gradation image from a continuous gradation document image into a halftone gradation. In a system LSI for gradation conversion of an image with a built-in program, the gradation conversion program is LS
A program built-in type image gradation conversion system LSI, characterized in that a program for executing the following operation steps for gradation conversion is stored in a ROM built in the I. <Work steps for gradation conversion> The original characteristic information stored in the ROM, that is, original image information (referred to as a vertical axis or a D axis) correlated with the density obtained by scanning an original image recorded on a predetermined recording medium, and the original. A density characteristic curve which is a characteristic of the recording medium and indicates a correlation with an image information value (referred to as a horizontal axis or an X axis) correlated with the amount of light incident on the recording medium from a corresponding subject to form an image is used. Obtaining an image information value (X _n ) correlated with the light amount of the corresponding pixel point (n) from an image information value (D _n ) correlated with the density of an arbitrary pixel point (n) on the original image; , 2. Step of converting the image information values (X _n) correlated with the amount of light obtained document image in the manner described above, the tone intensity value with <tonal conversion formula> following (y _n). <Tonal conversion _{formula> y n = y H + [} α (1-10 -k · xn) / (α-β)] ·
(Y _S -y _H) above in <tonal conversion formula>, each symbol means the following; xn: shows the [X _n -X _H]. That is, image information correlated to the quantity of the characteristic curves by using an arbitrary pixel point on the original image the image information values correlated to the concentration of the (n) (D _n) from the obtained corresponding pixel points (n) From the value (X _n ), the image information value (D _H ) correlated with the density of the brightest portion (H portion) on the original image was correlated with the light amount of the corresponding brightest portion obtained through the density characteristic curve. The basic light amount value obtained by subtracting the image information value (X _H ) is shown. y _n: tone intensity value set to the pixels on the reproduced image corresponding to an arbitrary pixel point on the original image (n). y _H : a gradation intensity value preset in the H portion on the duplicate image corresponding to the brightest portion (H portion) on the original image. y _S : A gradation intensity value preset in the S portion on the duplicate image corresponding to the darkest portion (S portion) on the original image. α: surface reflectance of an image expressing medium used to express a duplicate image. β: Numerical value determined by β = 10− ^γ . k: a numerical value determined by k = [γ / (X _S −X _H )]. Here, X _S is an image information value (D _S ) correlated with the density of the darkest portion (S portion) on the original image, and an image information value correlated with the light amount of the corresponding darkest portion obtained through the density characteristic curve. (X _S ). γ: any coefficient. 2. A system LSI for gradation conversion of an image having a built-in program, comprising: an arithmetic processing unit (MPU); and a ROM for storing a system program executed by the arithmetic processing unit (MPU). 2. The system LSI for gradation conversion of an image with a built-in program according to claim 1. 3. A system LSI for gradation conversion of an image having a built-in program, comprising an arithmetic processing unit (MPU), a ROM for storing a system program executed by the arithmetic processing unit (MPU), and a ROM stored in the ROM. 2. The system LSI according to claim 1, further comprising: a RAM for storing a program for switching at the time of a bug of the program or an additional program.