JP2001119592A - Color conversion method, color converter and color conversion program storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high-speed color conversion for the acquisition of a proof image by using a printer. SOLUTION: A printer using CMYK color materials is adopted and linear color conversion is conducted to reproduce a print dot gain characteristic on a printout independently of each of the CMYK.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for outputting a proof image reproducing a color of a color printed matter using a printer when performing color printing by a color printing machine. The present invention relates to a color conversion method, a color conversion device, and a color conversion program storage medium which is loaded into a computer system and stores a color conversion program for operating the computer system as a color conversion device.

[0002]

2. Description of the Related Art Conventionally, when performing color printing using a color printer, before printing, a color printer or the like is used to make the color of the image printed by the printer as similar as possible to the same color. Creating a proof image has been performed. When creating a proof image with a printer, the type of printing machine on which printing is to be performed and the conditions of use of the printing machine (such as the type of ink used and the quality of the paper to be printed, etc .; Collectively, the conditions necessary for one certain printing are referred to as printing conditions.)
A print profile describing the relationship between image data and the actual color of the printed matter, and the type of printer and the conditions of use of the printer. Printer profile that describes the relationship between the image data and the colors of the image actually printed out,
The image data for printing is converted into image data for a printer based on the print profile and the printer profile, and a proof image is created based on the converted image data for the printer. By doing this,
It is possible to create a proof image whose color matches the color of an actual printed matter. Usually, a print profile corresponding to typical printing conditions is provided by a printing company, and a printer profile is also provided by a manufacturer of the printer.

[0003]

When converting print image data into printer image data to obtain a proof image, usually, a print profile and a printer profile are combined to form one LUT (LUT). A look-up table) is created, the LUT is referred to, and the lower bit side, for which the correspondence is not described in the LUT, is subjected to an interpolation operation, so that the image data for printing is converted to the image data for printer. Will be converted to However, this LUT is a four-dimensional LUT that converts four-dimensional image data for printing defined in the CMYK color space into image data for a printer.
It takes time to refer to the UT and to perform an interpolation operation based on the image data obtained from the UT. In particular, when performing color conversion on an image with high resolution, it takes a considerable amount of time because the number of data points is large. is there.

In view of the above circumstances, the present invention provides a color conversion method capable of performing color conversion in a short time while maintaining color reproduction to a certain degree, a color conversion apparatus realizing the color conversion method,
It is another object of the present invention to provide a color conversion program storage medium storing a color conversion program for using a computer system as a color conversion device.

[0005]

According to a color conversion method of the present invention for achieving the above object, a printing image data representing an input network% of four CMYK colors is converted into an image based on image data representing an input network% of four CMYK colors. Is converted to image data for a printer for outputting a proof image that reproduces the color of the image obtained by printing the image based on the image data for printing under predetermined printing conditions using a printer that outputs In the color conversion method, image data for printing is converted into image data for a printer using four one-dimensional color conversion definitions for performing color conversion independently for each of the four CMYK colors.

Some printers, like printing,
There is a type that outputs an image based on image data defined in a CMYK color space, that is, a type that outputs an image using four CMYK color materials.

The present invention has been made by focusing on this point. The CMYK color material of the printer which is to output the proof image is used for the printing condition in which the proof image is to match the color. When the color is close to the CMYK ink color (this is referred to as a target printing condition), for example, CMYK may be used instead of referring to a four-dimensional LUT that takes a long time for color conversion and accompanying multidimensional interpolation calculation.
By using one-dimensional conversion definitions including one-dimensional LUTs and one-dimensional interpolation calculations, high-speed color conversion can be realized, and good color reproduction can be ensured.

Here, in the color conversion method of the present invention, as the four one-dimensional color conversion definitions, the gradation characteristics representing the effective halftone% with respect to the input halftone% of the printing are independently reproduced by the printer for each of CMYK. In this manner, image data for printing is converted into image data for a printer using four one-dimensional color conversion definitions for performing color conversion as described above.

If the color of the ink in the printing conditions is similar to the color of the colorant of the printer, one of the major factors that determines whether or not the proof image output from the printer matches well with the target printed matter is as follows. Actual net% on printed matter
There is a phenomenon called so-called dot gain in which (effective dot%) is different from dot% (input dot%) on image data, and effective dot% is larger than input dot%.

Therefore, in the color conversion method of the present invention, if the printing dot gain characteristics are reproduced by a printer by reproducing the gradation characteristics of the printing with a printer, even a general color conversion such as one-dimensional conversion is satisfactory. A proof image with excellent color reproduction can be obtained.

Here, in the first color conversion method of the color conversion method of the present invention, as a method of reproducing the gradation characteristics of printing by a printer, the method corresponds to each of CMYK of printing.
The tone characteristic functions for converting the input dot% (a) to the effective dot% correspond to T _c (a), T _M (a), T _Y (a), T _K (a), and CMYK of the printer, respectively. , P _c (a), P _c (a)
_M (a), P _Y (a), P _K (a), and each tone characteristic function P _c (a), P _M (a), P _Y (a), P _{K of the} printer
P _c ^-1 (b), P _M ^-1 (b), and P _c ^-1 (b), which are the inverse functions of (a) and which convert the effective halftone% (b) to the input halftone%, corresponding to CMYK of the printer, respectively. P _Y ^-1 (b), P
_{Assuming that K} ⁻¹ (b), S _c (a) = P _c ⁻¹ (T _c (a)) S _M (a) = P _M ⁻¹ (T _M (a)) S _Y (a) = Four one-dimensional color conversion definitions S _c (a), S represented by P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K (a))
By adopting _M (a), S _Y (a), and S _K (a), CMYK
A method of independently converting image data for printing into image data for a printer is adopted for each of the four colors.

In this case, the gradation characteristic function for converting the input halftone% (a) in the gray direction in printing into an effective halftone% is represented by T
_g of (a), the printer, the gray direction input halftone% gradation characteristic function of converting (a) the effective network% P _g (a), the tone characteristics of the gray direction of the printer function P _g (a) P _g ⁻¹ (b) is a function of converting the effective halftone% (b) in the gray direction into an input halftone% of the printer, and S _g (a) = When P _g ⁻¹ (T _g (a)), the above four one-dimensional color conversion definitions S _c (a),
Instead of S _M (a), S _Y (a), and S _K (a), these four
One-dimensional color conversion definitions S _c (a), S _M (a), S
_At least one of the color conversion definitions _Y (a) and S _K (a) is corrected based on the color conversion definition S _g (a) in the gray direction. The method of converting the image data of the above into image data for a printer may be adopted.

One of the major factors that determines whether the color of the proof image matches well with that of the target printed matter
Finally, there is a point as to whether or not the gray balances match. Therefore, by performing the color conversion in consideration of the gray gradation characteristics as described above, it is possible to obtain a proof image that further approximates the color of the target printed matter.

In the color conversion method according to the present invention, the second color
In the conversion method, the gradation characteristics of the print are reproduced by the printer
As a method, paper corresponding to each of CMYK of printing
Let the reflectance of white be t_c0, T_M0, T_Y0, T_K0, Input network
The reflectance when% is 100% is t_c1, T_M1, T
_Y1, T_K1, The reflectance when the input net% is a% is t
_c(A), t_M(A), t_Y(A), t_K(A), printer
The reflectance of paper white corresponding to each of CMYK
Each p_c0, P_M0, P_Y0, P_K0, Input network% is 100%
Each reflectivity_c1, P_M1, P_Y1, P_K1, Input network
The reflectance when% is a% is p_c(A), p
_M(A), p_Y(A), p_K(A) and CMY for printing
The input net% (a) corresponding to each K is changed to the effective net%.
Each gradation characteristic function T to be replaced_c(A), T_M(A), T
_Y(A), T_K(A) and CMYK of the printer
Convert the corresponding input net% (a) to effective net%
Tone characteristic function P _c(A), P_M(A), P_Y(A), P
_K(A) is T_c(A) = (t_c0-T_c(A)) / (t_c0-T_c1) T_M(A) = (t_M0-T_M(A)) / (t_M0-T_M1) T_Y(A) = (t_Y0-T_Y(A)) / (t_Y0-T_Y1) T_K(A) = (t_K0-T_K(A)) / (t_K0-T_K1) P_c(A) = (p_c0-P_c(A)) / (p_c0-P_c1) P_M(A) = (p_M0-P_M(A)) / (p_M0-P_M1) P_Y(A) = (p_Y0-P_Y(A)) / (p_Y0-P_Y1) P_K(A) = (p_K0-P_K(A)) / (p_K0-P_K1) And each gradation characteristic function P of the printer
_c(A), P_M(A), P_Y(A), P_KIn the inverse function of (a)
Certain printers, corresponding to CMYK, effective
Each function that converts halftone% (b) to input halftone% is P
_c ^-1(B), P_M ^-1(B), P_Y ^-1(B), P_K ^-1In (b)
When expressed, S_c(A) = P_c ^-1(T_c(A)) S_M(A) = P_M ^-1(T_M(A)) S_Y(A) = P_Y ^-1(T_Y(A)) S_K(A) = P_K ^-1(T_K(A)) Four one-dimensional color conversion definitions S represented by_c(A), S
_M(A), S_Y(A), S_KBy adopting (a), CMYK
Print image data for printing independently for each of the four colors.
The method of converting to image data for linter is adopted.
You.

Here, the reflectivity may be measured by a reflectometer for measuring the reflectivity in a physical sense, but is not limited thereto. For example, the reflectivity may be measured by a colorimeter. XY
Any one of X, Y, and Z in the Z color system, or any one corresponding to the color material, or a combination of a plurality of these X, Y, and Z may be used as the reflectance. In the present invention, the method for measuring the reflectance is not limited.

In the second color conversion method of the present invention,
When adjusting the gradation characteristics as described above,
The reflectance of paper white corresponding to CMY equivalent gray is t _g0 , the reflectance when the input net% is 100% for both CMY and t _g1 , and the reflectance when the input net% is a% for both CMY and t _g. (A),
Printer, corresponding to CMY equivalent amount gray reflectance when the reflectance t _g0, the input halftone dot% is p _g1 the reflectance when the CMY both 100%, the input halftone dot% of CMY both a% of paper white Is P _g (a), and CMY equivalent gray input net% of printing
A tone characteristic function T _g (a) for converting (a) into an effective halftone%,
And printer, CMY equivalent gray input network% (a)
Is converted to the effective dot% gradation characteristic function _{P g (a), T g} (a) = (t g0 -t g (a)) / (t g0 -t g1) P g (a) = (p _g0 is defined as _{-p g (a)) / (} p g0 -p g1), furthermore, an inverse function of the printer CMY equivalent amount gray tone characteristic function P _g (a), a printer, CM
A function for converting the effective halftone% (b) of the Y equivalent gray to the input halftone percentage is represented by P _g ^-1 (b), and the gray color conversion definition is S _g (a) = P _g ^-1 (T _g (A)), the above four one-dimensional color conversion definitions S _c (a),
Instead of three one-dimensional color conversion definitions S _c (a), S _m (a), and S _y (a) among S _M (a), S _Y (a), and S _K (a), S _c '(A) = w _c · S _c (a) + (1-w _c ) S _g (a) S _M ' (a) = w _M · S _M (a) + (1-w _M ) S _g ( a) S _Y ′ (a) = w _Y · S _Y (a) + (1−w _Y ) S _g (a) where w _c , w _M , and w _Y are 0 ≦ w _c , w _M , w It is an adjustable weight coefficient with _Y ≤ 1. The three one-dimensional color conversion definitions S _c '(a), S _M ' (a), and S _Y '(a)
And the above four one-dimensional color conversion definitions S _c
(A), one of S _M (a), S _Y (a), and S _K (a)
It is preferable to adopt one one-dimensional color conversion definition S _K (a) to convert image data for printing into image data for a printer.

By doing so, it is possible to perform color conversion in consideration of gray gradation characteristics.

A color conversion apparatus according to the present invention, which achieves the above object, provides a printer for outputting image data for printing representing an input network% of four CMYK colors and an image based on image data representing an input network% of four CMYK colors. A color conversion device for converting an image based on image data for printing using a printer into image data for a printer for outputting a proof image that reproduces the color of the image obtained when the image is printed under predetermined printing conditions A one-dimensional color conversion definition storage unit that stores four one-dimensional color conversion definitions for independently performing color conversion for each of the four CMYK colors, and a one-dimensional color conversion definition stored in the one-dimensional color conversion definition storage unit. A color conversion unit for converting image data for printing into image data for a printer.

The color conversion apparatus of the present invention performs color conversion using four one-dimensional color conversion definitions for independently performing color conversion for CMYK, and converts image data defined in the CMYK color space. , And can perform high-speed color conversion.

Here, in the first color conversion apparatus of the color conversion apparatus of the present invention, the one-dimensional color conversion storage unit stores the input network% (a) corresponding to each of CMYK for printing as an effective network. %, T _c (a), T
_M (a), T _Y (a), T _K (a), CMY of printer
P _c (a), P _M (a), and P _c (a), P _M (a), P
_{Y (a), P K (} a), and, each tone characteristic function P _c of the printer _{(a), P M (a} ), an inverse function of _{P Y (a), P K} (a), the printer , CMYK,
Each function that converts effective net% (b) to input net% is P
^{_{c -1 (b), P M}} -1 (b), P Y -1 (b), when the ^{_{P K -1 (b), S}} c (a) = P c -1 (T c (a) ) S _M (a) = P _M ^-1 (T _M (a)) S _Y (a) = P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K (a )) Four one-dimensional color conversion definitions S _c (a), S
_M (a), S _Y (a), and S _K (a) are stored.

In the first color conversion apparatus of the present invention, the one-dimensional color conversion definition storage unit stores a tone characteristic function for converting an input halftone (a) in the gray direction of printing into an effective halftone _Tg.
(A), P _g (a) is a tone characteristic function for converting an input halftone (%) in the gray direction into an effective halftone percentage of the printer, and is the inverse of the tone characteristic function P _g (a) in the gray direction of the printer. P _g ^-1 (b) is a function for converting the effective halftone% (b) in the gray direction into an input halftone% of the printer, and S _g (a) = P _g ⁻¹ (T _g (a)), the above four one-dimensional color conversion definitions S _c (a),
Instead of S _M (a), S _Y (a), and S _K (a), these four
One-dimensional color conversion definitions S _c (a), S _M (a), S
_This stores four color conversion definitions obtained by correcting at least one color conversion definition among _Y (a) and S _K (a) based on the color conversion definition S _g (a) in the gray direction. There may be.

As described in the description of the color conversion method, one of the major factors that determines whether the color of the proof image matches the color of the target printed matter is whether or not the gray balance matches. There is also a point. Therefore, by storing the one-dimensional color conversion definition taking into account the gray gradation characteristics as described above and performing color conversion, it is possible to obtain a proof image that is even closer to the color of the target printed matter.

In the color conversion apparatus according to the present invention, the second color
In the conversion apparatus, the one-dimensional color conversion storage unit stores a CM for printing.
The reflectance of paper white corresponding to each of YK
t_c0, T _M0, T_Y0, T_K0, When the input network% is 100%
The reflectance is t_c1, T_M1, T _Y1, T_K1, Input net%
The reflectance at a% is t_c(A), t_M(A),
t _Y(A), t_K(A), each of CMYK of printer
And the reflectance of paper white corresponding to_c0, P_M0,
p_Y0, P_K0, Reflectivity when input net% is 100%
Each p_c1, P_M1, P_Y1, P_K1, When input network% is a%
The reflectance is p_c(A), p_M(A), p_Y(A),
p_K(A), corresponding to each of CMYK of printing
, Each gradation characteristic function for converting the input dot% (a) into an effective dot%.
Number T_c(A), T_M(A), T_Y(A), T_K(A) and
% Of input network corresponding to each of CMYK and printer
Each gradation characteristic function P for converting (a) to effective dot%
_c(A), P_M(A), P _Y(A), P_K(A)
Re T_c(A) = (t_c0-T_c(A)) / (t_c0-T_c1) T_M(A) = (t_M0-T_M(A)) / (t_M0-T_M1) T_Y(A) = (t_Y0-T_Y(A)) / (t_Y0-T_Y1) T_K(A) = (t_K0-T_K(A)) / (t_K0-T_K1) P_c(A) = (p_c0-P_c(A)) / (p_c0-P_c1) P_M(A) = (p_M0-P_M(A)) / (p_M0-P_M1) P_Y(A) = (p_Y0-P_Y(A)) / (p_Y0-P_Y1) P_K(A) = (p_K0-P_K(A)) / (p_K0-P_K1) And each gradation characteristic function P of the printer
_c(A), P_M(A), P_Y(A), P_KIn the inverse function of (a)
Certain printers, corresponding to CMYK, effective
Each function that converts halftone% (b) to input halftone% is P
_c ^-1(B), P_M ^-1(B), P_Y ^-1(B), P_K ^-1In (b)
When expressed, S_c(A) = P_c ^-1(T_c(A)) S_M(A) = P_M ^-1(T_M(A)) S_Y(A) = P_Y ^-1(T_Y(A)) S_K(A) = P_K ^-1(T_K(A)) Four one-dimensional color conversion definitions S represented by_c(A), S
_M(A), S_Y(A), S_K(A) is memorized
There is a feature.

Here, the definition of the reflectance is the same as the definition of the reflectance in the above-described color conversion method.

In the second color conversion apparatus of the present invention, 1
The dimensional color conversion definition storage unit stores the reflectance of paper white corresponding to the CMY equivalent gray of printing as t _g0 , the reflectance when the input _dot % is 100% for both CMY and t _g1 , and the input dot% as CMY. T _g (a) is the reflectance when both are a%, and CMY of the printer
The reflectance of paper white corresponding to the equivalent gray is t _g0 , input net%
Is 100% for both CMY, reflectivity is _pg1 , input network%
There the reflectance when the CMY together a% as P _g (a), of printing, gradation characteristic function The T _g for converting input halftone% of CMY equivalent amount Gray: (a) the effective dot% (a), and Of the printer,
The tone characteristic function P _g (a) for converting the input halftone (%) of CMY equivalent gray to the effective halftone is represented by T _g (a) = (t _g0 −t _g (a)) / (t _g0 − t _g1 ) P _g (a) = (p _g0 −p _g (a)) / (p _g0 −p _g1 ), and further, the gradation characteristic function P _g (a) of the CMY equivalent gray of the printer Printer's CM, which is the inverse function
A function for converting the effective halftone% (b) of the Y equivalent gray to the input halftone percentage is represented by P _g ^-1 (b), and the gray color conversion definition is S _g (a) = P _g ^-1 (T _g (A)), the above four one-dimensional color conversion definitions S _c (a),
Instead of three one-dimensional color conversion definitions S _c (a), S _m (a), and S _y (a) among S _M (a), S _Y (a), and S _K (a), S _c '(A) = w _c · S _c (a) + (1-w _c ) S _g (a) S _M ' (a) = w _M · S _M (a) + (1-w _M ) S _g ( a) S _Y ′ (a) = w _Y · S _Y (a) + (1−w _Y ) S _g (a) where w _c , w _M , and w _Y are 0 ≦ w _c , w _M , w It is an adjustable weight coefficient with _Y ≤ 1. The three one-dimensional color conversion definitions S _c '(a), S _M ' (a), and S _Y '(a)
With storing the above four 1-dimensional color conversion definition _{S c (a), S M} (a), S Y (a), S 1 one-dimensional color conversion definition S _K of the _K (a) Preferably, (a) is stored.

By doing so, it is possible to perform color conversion in consideration of gray gradation characteristics.

Here, in each of the first and second color conversion apparatuses of the present invention, a four-dimensional color conversion definition for storing a four-dimensional color conversion definition for performing color conversion in which four CMYK colors are mutually dependent is stored. The color conversion unit includes a definition storage unit.
A mode for converting image data for printing into image data for a printer using the one-dimensional color conversion definition stored in the three-dimensional color conversion definition storage unit, and the four-dimensional color conversion stored in the four-dimensional color conversion definition storage unit And a mode for converting image data for printing into image data for a printer using the definition.

As described above, it is necessary to perform high-speed color conversion by providing a mode in which color conversion is performed using four-dimensional color conversion definitions in addition to a mode in which color conversion is performed using one-dimensional color conversion definitions. It is possible to adaptively cope with both the case and the case where it is preferable to perform color conversion with higher precision even if it takes time.

Further, the color conversion program storage medium of the present invention uses a printer that outputs image data for printing representing the input network% of four CMYK colors based on image data representing the input network% of four CMYK colors. A color conversion program for converting into image data for a printer for outputting a proof image that reproduces the color of the image obtained by printing an image based on the image data for printing under predetermined printing conditions is stored. A color conversion program for converting image data for printing into image data for a printer using four one-dimensional color conversion definitions for performing color conversion independently for each of the four colors CMYK. It is characterized by being stored.

According to the color conversion program stored in the color conversion program storage medium of the present invention, the computer system is loaded into a computer system,
It can be operated as a color conversion device that performs high-speed color conversion and that is suitable for a printer that outputs an image based on image data defined in the CMYK color space.

Here, the first color conversion program storage medium of the color conversion program storage medium of the present invention stores each floor for converting the input network% (a) corresponding to each of CMYK into the effective network% for printing. T _c (a), T
_M (a), T _Y (a), T _K (a), CMY of printer
P _c (a), P _M (a), and P _c (a), P _M (a), P
_{Y (a), P K (} a), and, each tone characteristic function P _c of the printer _{(a), P M (a} ), an inverse function of _{P Y (a), P K} (a), the printer , CMYK,
Each function that converts effective net% (b) to input net% is P
^{_{c -1 (b), P M}} -1 (b), P Y -1 (b), when the ^{_{P K -1 (b), S}} c (a) = P c -1 (T c (a) ) S _M (a) = P _M ^-1 (T _M (a)) S _Y (a) = P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K (a )) Four one-dimensional color conversion definitions S _c (a), S
A color conversion program for independently converting image data for printing into image data for a printer for four colors of CMYK using _M (a), S _Y (a), and S _K (a) is stored. .

Alternatively, the first color conversion program storage medium stores the tone characteristic function T _g (a) for converting the input halftone% (a) in the gray direction into an effective halftone% for printing, and the gray scale function of the printer. P _g (a) is the tone characteristic function for converting the input halftone% (a) in the direction to the effective halftone%, and the inverse of the grayscale tone characteristic function P _g (a) of the printer. P _g ^-1 (b) is a function for converting the effective halftone% (b) in the direction to the input halftone%, and S _g (a) = P _g ^-1 (T _g (a )), The above four one-dimensional color conversion definitions S _c (a),
Instead of S _M (a), S _Y (a), and S _K (a), these four
One-dimensional color conversion definitions S _c (a), S _M (a), S
_At least one color conversion definition among _Y (a) and S _K (a) is corrected based on the color conversion definition S _g (a) in the gray direction, and the four color conversion definitions are used for printing. A color conversion program for independently converting image data into image data for a printer for each of the four CMYK colors may be stored.

As described above, one of the major factors that determines whether the color of the proof image matches the color of the target printed matter is whether or not the gray balance matches. Also exists. Therefore, by performing the color conversion in consideration of the gray gradation characteristics as described above, it is possible to obtain a proof image that further approximates the color of the target printed matter.

Further, the color conversion program storage medium of the present invention
The second color conversion program storage medium of the
The reflectance of paper white corresponding to each of CMYK
t_c0, T_M0, T_Y0, T_K0, When the input network% is 100%
The reflectance is t_c1, T_M1, T_Y1, T_K1, Input net%
The reflectance at a% is t_c(A), t_M(A),
t_Y(A), t_K(A), each of CMYK of printer
And the reflectance of paper white corresponding to_c0, P_M0,
p_Y0, P_K0, Reflectivity when input net% is 100%
Each p_c1, P_M1, P_Y1, P_K1, When input network% is a%
The reflectance is p _c(A), p_M(A), p_Y(A),
p_K(A), corresponding to each of CMYK of printing
, Each gradation characteristic function for converting the input dot% (a) into an effective dot%.
Number T_c(A), T_M(A), T_Y(A), T_K(A) and
% Of input network corresponding to each of CMYK and printer
Each gradation characteristic function P for converting (a) to effective dot%
_c(A), P_M(A), P_Y(A), P_K(A)
Re T_c(A) = (t_c0-T_c(A)) / (t_c0-T_c1) T_M(A) = (t_M0-T_M(A)) / (t_M0-T_M1) T_Y(A) = (t_Y0-T_Y(A)) / (t_Y0-T_Y1) T_K(A) = (t_K0-T_K(A)) / (t_K0-T_K1) P_c(A) = (p_c0-P_c(A)) / (p_c0-P_c1) P_M(A) = (p_M0-P_M(A)) / (p_M0-P_M1) P_Y(A) = (p_Y0-P_Y(A)) / (p_Y0-P_Y1) P_K(A) = (p_K0-P_K(A)) / (p_K0-P_K1) And each gradation characteristic function P of the printer
_c(A), P_M(A), P_Y(A), P_KIn the inverse function of (a)
Certain printers, corresponding to CMYK, effective
Each function that converts halftone% (b) to input halftone% is P
_c ^-1(B), P_M ^-1(B), P_Y ^-1(B), P_K ^-1In (b)
When expressed, S_c(A) = P_c ^-1(T_c(A)) S_M(A) = P_M ^-1(T_M(A)) S_Y(A) = P_Y ^-1(T_Y(A)) S_K(A) = P_K ^-1(T_K(A)) Four one-dimensional color conversion definitions S represented by_c(A), S
_M(A), S_Y(A), S_KUsing (a), the image for printing
Image data is converted to CMYK 4 colors for printer image data.
Color conversion programs for independent conversion
It was a thing.

Here, the definition of the reflectance is the same as described above.

Alternatively, the second color conversion program
The storage medium is paper white, corresponding to CMY equivalent gray for printing.
The reflectance of t_g0When the input network% is 100% for both CMY
The reflectance of t_g1When the input net% is a% for both CMY
Emissivity is t_g(A), CMY equivalent gray
The corresponding white reflectance of the paper is t_g0, Input network% is 1 for both CMY
The reflectance at 00% is p_g1, Input network% is a for both CMY
% When the reflectance is P _g(A) and print, CMY, etc.
Tone conversion that converts the input gray% (a) to the effective gray%
Sex function T_g(A) and the printer's CMY equivalent
Gray scale characteristic function to convert input halftone% (a) into effective halftone%
P_g(A), T_g(A) = (t_g0-T_g(A)) / (t_g0-T_g1) P_g(A) = (p_g0-P_g(A)) / (p_g0-P_g1) And the printer's CMY equivalent gray scale
Characteristic function P_gThe CM of the printer, which is the inverse function of (a)
A function for converting the effective net% (b) of the Y equivalent gray
Number P_g ^-1(B), and gray color conversion definition
To S_g(A) = P_g ^-1(T_g(A)), the above four one-dimensional color conversion definitions S_c(A),
S_M(A), S_Y(A), S_KThree primary of (a)
Original color conversion definition S_c(A), S_M(A), S_YInstead of (a)
And S_c’(A) = w_c・ S_c(A) + (1-w)_c) S_g(A) S_M’(A) = w_M・ S_M(A) + (1-w)_M) S_g(A) S_Y’(A) = w_Y・ S_Y(A) + (1-w)_Y) S_g(A) where w_c, W_M, W_YIs 0 ≦ w_c, W_M, W_YAdjustment of ≤1
It is a flexible weighting factor. Three primary orders represented by
Original color conversion definition S_c’(A), S_M’(A), S_Y’(A)
And the above four one-dimensional color conversion definitions S
_c(A), S_M(A), S_Y(A), S_KOne of (a)
One-dimensional color conversion definition S_KUsing (a), the image for printing
Image data is converted to CMYK 4 colors for printer image data.
Color conversion programs for independent conversion
It may be something that is not done.

By doing so, it is possible to perform color conversion in consideration of gray gradation characteristics.

[0038]

Embodiments of the present invention will be described below.

FIG. 1 is an overall configuration diagram of a printing and proof image forming system to which an embodiment of the present invention is applied.

In the color scanner 10, a document image is read, and CMY representing the read document image.
K4 color separation image data is generated. This CMYK
Is input to the workstation 20.
At the workstation 20, an operator performs electronic plate collection based on the input image data.
Image data representing an image for printing is generated. The image data for printing is input to the film printer 30 when printing is performed.
CMYK printing plate originals corresponding to the input image data are created.

A printing plate is prepared from the printing film precursor, and the prepared printing plate is mounted on a printing machine 40.
Ink is applied to the printing plate mounted on the printing press 40, and the applied ink is transferred onto printing paper to form an image 41 on the printing paper.

A series of operations for preparing a film master by the film printer 30, preparing a printing plate, mounting the printing plate on a printing machine 40, applying ink to the printing plate, and printing on paper, are extensive. It's work and costly. Therefore, before the actual printing operation is performed, the proof image 61 is created by the printer 60 as described below, and the finish of the print image 41 is checked in advance.

In creating a proof image, image data created by electronic printing on the workstation 20 is input to the personal computer 50.
Here, the image data input to the personal computer 50 is a so-called PDL (Page Deccr).
description language data), and in the personal computer 100,
So-called RIP (Raster Image Proc)
ESSOR), CMY expanded to a bitmap
It is converted to K4 color image data. The image data of the four colors CMYK is substantially the same as the image data for printing input to the film printer 30.

The print image data of the four colors CMYK is stored in the personal computer 50 in the LUT.
A color conversion definition having a format of (Look Up Table) is referred to, and is converted into CMYK image data suitable for the printer 60. The converted CMYK image data is input to the printer 60.
The proof image 61 is created based on the input CMYK image data. The printer 60 used here is a printer that outputs an image based on image data defined in the CMYK color space, that is, a printer that performs print output using four color materials of CMYK.

By creating a proof image and confirming the proof image in this way, the finish of printing can be confirmed in advance.

Here, the degree of color matching between the image 41 obtained by printing by the printing machine 40 and the proof image obtained by the printer 60 is determined by the color conversion definition in the personal computer 50.

The feature of one embodiment of the present invention in the proof image creation system shown in FIG. 1 resides in the processing executed inside the personal computer 50. The personal computer 50 will be described below.

FIG. 2 is an external perspective view of the personal computer 50 shown by one block in FIG. 1, and FIG. 3 is a hardware configuration diagram of the personal computer 50.

The personal computer 50 has a main body device 51, an image display device 52 for displaying an image on a display screen 52a in response to an instruction from the main body device 51, and a main device 51 in response to a key operation. A keyboard 53 for inputting various types of information, and a mouse 5 for designating an arbitrary position on the display screen 52a to input an instruction corresponding to, for example, an icon displayed at the position.
4 is provided. The main unit 51 has a floppy disk loading port 51a for loading a floppy disk, and a CD-ROM for loading a CD-ROM.
It has a ROM loading port 51b.

As shown in FIG. 3, a CPU 511 for executing various programs and a program stored in a hard disk device 513 are read out to
A main memory 512 expanded for execution in 511, a hard disk device 513 storing various programs and data, and an FD for loading the floppy disk 100 and accessing the loaded floppy disk 100
Driver 514, CD-ROM 110 loaded, and CD-R accessing the loaded CD-ROM 110
An OM driver 515, an I / O interface 516 connected to the workstation 20 (see FIG. 1) and receiving image data from the workstation 20, and a printer 6
A built-in printer interface 517 for sending image data to the image display device 52, a keyboard 53, and a mouse 54 shown in FIG.
Are connected to each other via a bus 55.

The CD-ROM 110 stores a color conversion program for operating the personal computer 50 as a color conversion device.
The ROM 110 is loaded into the CD-ROM driver 515, and the color conversion program stored in the CD-ROM 110 is uploaded to the personal computer 50 and stored in the hard disk device 513.

Here, when one embodiment of the color conversion program of the present invention is stored in the CD-ROM 110,
The CD-ROM 110 corresponds to an embodiment of the color conversion program storage medium of the present invention. When the color conversion program is uploaded and stored in the hard disk device 513, the color conversion program is stored. The hard disk device 513 also corresponds to an embodiment of the color conversion program storage medium of the present invention. Further, when the color conversion program is downloaded to the floppy disk 100, the floppy disk 100 in which the color conversion program is stored also corresponds to an embodiment of the color conversion program storage medium of the present invention.

Next, a method for creating a color conversion definition built inside the personal computer 50 will be described.

FIG. 4 is a flowchart showing a procedure for creating a four-dimensional color conversion definition.

Here, first, a print profile is created (step (a)). As described above, a printing profile corresponding to typical printing conditions is often provided by a printing company, and if a printing profile corresponding to desired printing conditions can be obtained, this step (a) is unnecessary. However, here, a basic creation method when the print profile is newly created will be described.

From the workstation shown in FIG.
The halftone% data of the K4 color is, for example, 0%, 10%,.
By changing it to 0%, patch data composed of a combination of four colors of CMYK of each halftone is generated, and a color patch image based on the generated patch data is created according to the above-described printing procedure. Although the image 41 shown in FIG. 1 is not an image representing a color patch image, it is assumed that a color patch image is printed in place of the image 41, and each color patch constituting the color patch image is Measure with In this way, a print profile is created that represents the correspondence between the coordinate values of the four CMYK color spaces and the coordinate values of the colorimetric color space (here, the color space of the XYZ color system).

FIG. 5 is a conceptual diagram of a print profile.

In this print profile, CMYK halftone%
Image data is input, and the CMYK image data is X
It is converted to YZ image data.

Here, the CMYK image data is represented by X
A print profile (forward conversion print profile) for converting to YZ image data is represented by T, and a reverse conversion thereof, that is, a print profile (reverse conversion print profile) for converting XYZ image data to CMYK image data is represented by T.
^Represented by ^-1 .

Next, a printer profile is created (step (b) in FIG. 4). As described above, the printer profile is often provided from the printer maker, and if the printer profile corresponding to the printer for which the proof image is to be output can be obtained, this step (b) is unnecessary. Here, a basic method of creating a new printer profile will be described. The method of creating a printer profile is the same as the method of creating a print profile described above.

The printer 60 shown in FIG. 1 is a printer that outputs an image based on CMYK halftone% image data.

Here, in the personal computer 50 shown in FIG. 1, halftone% is set from 0% to 100% for each of CMYK colors.
%, For example, in increments of 10%, to generate patch data composed of combinations of four colors of CMYK of the dot% data, and the printer 60 creates a color patch image based on the generated patch data. Although the image 61 shown in FIG. 1 is not an image representing a color patch image, it is assumed that a color patch image is output in place of the image 61, and each color patch constituting the color patch image is output to a colorimeter 200. Measure with. By doing so, a printer profile is created that represents the correspondence between the coordinate values of the CMYK color space and the coordinate values of the colorimetric color space (here, the color space of the XYZ color system) for the printer 60.

FIG. 6 is a conceptual diagram of a printer profile.

This printer profile includes CMYK
Is input, and the CMYK image data is converted into XYZ image data. Here, CMYK
A printer profile (forward conversion printer profile) for converting image data of XYZ into XYZ image data is represented by P, and its inverse conversion, that is, XYZ image data is represented by C
A printer profile (inverse conversion printer profile) to be converted into MYK image data is represented by P- ¹ .

FIG. 7 is a diagram showing a color conversion definition in which a print profile and a printer profile are combined.

The CMYK image data is converted into XYZ image data by the print profile T, and then the XY image data is converted.
The Z image data is converted into CMYK image data by the inverse conversion printer profile P- ¹ . Based on the CMYK image data generated in this way, the printer 60
Thus, a proof image of the same color as that of printing can be output.

In the case of the color conversion definition shown in FIG. 7, since the print profile and the printer profile obtained as described above are used, a considerably high-precision color conversion is possible. This is a four-dimensional color conversion definition of CMYK. As described above, the color conversion based on this color conversion definition takes time and has the disadvantage of lacking high speed.

Next, a method of creating a one-dimensional color conversion definition characteristic of this embodiment will be described.

FIG. 8 is an explanatory diagram of a method for creating a one-dimensional color conversion definition.

Here, first, the reflectance in the case of printing is measured (step (a)).

In this case, the workstation 20 shown in FIG. 1 uses the workstation 20 shown in FIG.
Is fixed at 0%, C patch data is generated in which C is sequentially changed from 0%, 10%,..., 100% in increments of 10%, and based on the generated C patch data according to the above-described printing procedure. A patch image of C is created. The reflectance of each patch constituting the patch image of C thus created is measured. Here, the colorimeter 200 shown in FIG. 1 is used for the reflectance measurement, and among the XYZ measurement data obtained by the measurement, the measurement value of C is the largest with respect to the change of the dot% of C. X data that changes greatly is employed.

Similarly, a patch image is created for M, Y, and K, and the reflectance is measured. That is,
As for M, for C, Y, and K, the mesh% is fixed at 0%, and M is 0%, 10%,.
In accordance with the above-described printing procedure, an M patch image is created based on the M patch data thus generated, and the reflectance of each patch constituting the M patch image is measured by a colorimeter. Measure at 200. In the case of M,
Of the XYZ measurement data obtained by the measurement,
The data of Y having the largest change in the measured value with respect to the change in the dot% of M is adopted.

For the Y and K colors, patch images are created and measured in the same manner. As for the Y color, Z data of the XYZ measurement data is adopted, and as for K, Y data of the XYZ measurement data is adopted as in the case of M.

As can be seen from the print profile creation procedure described with reference to FIG. 4, the print profile includes the reflectance data in step (a) in FIG. When the print profile has been created, it is not necessary to create or measure a new patch image in step (a) of FIG. 8, but only to extract necessary data from the print profile.

Next, based on the reflectance measured as described above (or the reflectance extracted from the printing profile), the gradation characteristic of the printing condition is calculated (step (b) in FIG. 8).

Here, the reflectance of paper white for printing, that is, the reflectance of paper when halftone% is 0% for all four colors of C, M, Y, and K is represented by C, M, Y, and K, respectively. , T _c0 , t _M0 , t _Y0 , and t _K0 , respectively. XYZ
Of the measurement data, C color is X, M color is Y,
Since the Y color employs Z and the K color employs Y, the reflectance of the paper is not necessarily the same for each of C, M, Y, and K. Therefore, here, the reflectance of the paper for each of CMYK is represented by a different symbol. Further, the reflectance of the print when the input net% of C is 100% (the input net% of M, Y, and K is 0%) is t _c1 , and similarly, M, Y, and
100% of the input net% of K (0% for colors other than the color of interest)
%) _Are t _M1 , t _Y1 , and t _K1 . Further, when the input net% of C is a% (the input net% of M, Y, and K is 0%), the reflectance is represented by t _c (a).
The input net% for Y and K is a% (colors other than the color of interest are 0
%), T _M (a), t _Y (a), t
Let _K (a).

At this time, for each of CMYK for printing,
The gradation characteristic T representing the effective dot% with respect to the input dot%
_c (a), T _M (a), T _Y (a), T _K (a) are expressed as T _c (a) = (t _c0 −t _c (a)) / (t _c0 −t _c1 ) (1) T _M (a) = (t _M0 −t _M (a)) / (t _M0 −t _M1 ) (2) T _Y (a) = (t _Y0 −t _Y (a)) / ( t _Y0 −t _Y1 ) (3) T _K (a) = (t _K0 −t _K (a)) / (t _K0 −t _K1 ) (4)

FIG. 9 is a diagram showing an example of the gradation characteristics for C (cyan).

Although the gradation characteristics of the above equations (1) to (4) are standardized, FIG. 9 shows the gradation characteristics before the standardization.

In FIG. 9, the horizontal axis is the input net% of C, and the vertical axis is the reflectance (here, X in the XYZ color system). The reflectance t _c0 when the input dot% is 0% is the reflectance of the paper white of the printing paper, and the reflectance t _c1 when the input dot% is 100% is the C ink used for the printing. Is the solid reflectance.

Here, as shown in FIG. 9, the gradation characteristic is represented not by a straight line but by a downwardly convex curve. this is,
When printing is performed with image data of a certain input network% (for example, a1%), the ink spreads on the printing paper and has the same reflectance as a2% when the spread does not exist. This is because a1) occurs.

Here, according to the procedure described with reference to FIG. 8, one-dimensional color conversion definitions for each of CMYK are obtained so that the dot gain characteristics of printing shown in FIG. 9 are reproduced on the printer output.

In step (c) of FIG. 8, the reflectance of the print output is measured.

Here, as in the case of printing, the personal computer 50 shown in FIG. 1 sets the halftone% of the four colors CMYK, for example, to 0% for M, Y, and K, and sets 0% for C in increments of 10%. %, 10%, ..., 10
The patch data of C which is sequentially changed to 0% is generated, and the printer 60 generates the C patch data based on the generated patch data.
Create a patch image. Then, the reflectance of each patch constituting the patch image of C created in this way is measured using the colorimeter 200 shown in FIG. 1 together with the time of printing, and X data is adopted for C.

Similarly, for M, Y, and K, each patch image is created using the printer 60, and the reflectance is measured. In the case of M, Y, K, XY
Among Z, data of Y, Z, and Y are adopted, respectively.

Here, similarly to the case of printing, the printer profile whose procedure has been described with reference to FIG.
When the data includes the reflectance data in step (c) of FIG. 8 and the printer profile has been obtained or created, it is not necessary to create or measure a new patch image in step (c) of FIG. It is only necessary to extract necessary data from the printer profile.

Next, the reflectance measured as described above (or the reflectance extracted from the printer profile)
, The tone characteristics when printing by the printer 60 (see FIG. 1) are calculated (step (d) in FIG. 8).

Here, the reflectance of paper white of the print paper,
That is, halftone% is 0 for all four colors C, M, Y, and K.
%, The reflectance of the paper for C, M, Y, and K
Correspondingly, p_c0, P_M0, P_Y0, P_K0And CMYK
The notation according to each color is the same reason as printing
by. Also, the input network% of C of the print output is 100
% (Input net% of M, Y, K is 0%)
_c1, Similarly, the input network% of M, Y, K is 100% (note that
The reflectance at 0% for colors other than the present color) is p _M1,
p_Y1, P_K1And In addition, the print output color C
When the power net% is a% (the input net% of M, Y, K is 0%)
The reflectance is p_c(A) Similarly, the input network% of M, Y, and K is
Reflectance at a% (0% for colors other than the color of interest)
To p_M(A), p_Y(A), p_K(A).

At this time, the gradation characteristic P representing the effective dot% with respect to the input dot% of each of CMYK of the printer.
_c (a), P _M (a), P _Y (a), P _K (a) are _{expressed as} P _c (a) = (p _c0 −t _c (a)) / (p _c0 −p _c1 ) (5) P _M (a) = (p _M0 −t _M (a)) / (p _M0 −p _M1 ) (6) P _Y (a) = (p _Y0 −t _Y (a)) / ( p _Y0 −p _Y1 ) (7) _PK (a) = (p _K0 −t _K (a)) / (p _K0 −p _K1 ) (8)

FIG. 10 relates to C (cyan). FIG. 10 is a diagram showing the tone characteristics of printing (solid line) and the tone characteristics of print output (dashed line) also shown in FIG. 9. In FIG. 10, FIG.
As in the case of (1), the gradation characteristics before standardization are shown.

FIG. 9 shows the gradation characteristics (solid line) of printing.
, And the description is omitted here. Regarding the gradation characteristics (dot-and-dash line) of the print output, the value _pc0 when the input dot% (horizontal axis) of C is 0% is the reflectance of the paper white of the print paper and the input dot% when the input dot% is 100%. Value p _c1
Is the solid reflectance of the C color material used for the print output.

Here, the gradation characteristic of the print output (dashed line) is also represented by a downwardly convex curve similarly to the gradation characteristic of the printing (solid line), although the degree of the curve is different. this is,
In the case of print output as well, to a different extent than in the case of print, it means that there is a dot gain.

In step (e) of FIG. 8, one step for reproducing the printing dot gain characteristic on the printing output, taking into account both the printing dot gain and the printing output dot gain, as described above. A dimensional color conversion definition is required.

Here, functions P _c (a) and P _M representing the tone characteristics of the print output represented by the equations (5) to (8)
(A) Effective net% corresponding to each of CMYK of print output, which is the inverse function of P _Y (a) and _PK (a) (b)
Are converted to _Pc ^-1 (b), P
_M ^-1 (b), P _Y ^-1 (b), and _PK ^-1 (b), 4
As one one-dimensional color conversion definition, S _c (a) = P _c ^-1 (T _c (a)) (9) S _M (a) = P _M ^-1 (T _M (a)). 10) S _Y (a) = P _Y ^-1 (T _Y (a)) (11) S _K (a) = P _K ^-1 (T _K (a)) S (12) _c (a), S _M (a), S _Y (a), S
_{Find K} (a).

FIG. 11 is a diagram showing a standardized gradation characteristic curve for C (cyan). In FIG. 11, a solid line is a gradation characteristic curve of printing, and a dashed line is a gradation characteristic curve of printing output.

In the case of printing, when printing is performed based on data in which the input network% of C is a1, a printed material having a reflectance of the normalized reflectance r is obtained. In order to reproduce the normalized reflectance r on the print output, data in which the input network% of C is a2% may be sent to the printer 60 (see FIG. 1).
That is, if the C data a1 for printing is converted into the C data a2 for printer, the printing dot gain can be reproduced on the print output.

The above four one-dimensional colors (9) to (12)
Conversion definition S_c(A), S_M(A), S _Y(A), S_K(A)
Is based on the above principle for each color of CMYK
To reproduce the dot gain characteristics of the printout on the printout.
Definition formula that performs color conversion (data conversion) like
I have.

In this manner, when one-dimensional color conversion is performed so as to reproduce the dot gain characteristic of printing on a print output, a proof image very similar to a printed matter can be obtained.

Next, a method for creating another example of the one-dimensional color conversion definition will be described with reference to FIG. 8 again.

In step (a) of FIG. 8, in the same manner as described above, the CMYK patch images are created by printing, and the reflectance of each patch is measured.
.., 100% for the three colors at the same time, and creates a gray patch image by printing. The colorimeter 200 forms the gray patch image. Measure the reflectance of each patch.
Here, the data of Y in XYZ is adopted.

As with the reflectance data of each of CMYK,
When a print profile has been obtained or created, it is not necessary to create or measure a new gray patch image, and it is only necessary to extract necessary data from the print profile.

In step (b) of FIG. 8, the aforementioned (1)
To (4), gradation characteristics _Tc (a), T _M (a), T _Y (a), T T of each of CMYK of printing.
To calculate the _K (a), printing, CMY equivalent amount gray input halftone% gradation characteristics The T _g represents the effective dot% for (a) (a), T g (a) = (t g0 -t _g (a)) / (t _g0 −t _g1 ) (13)

Here, t _g0 , t _g1 , and t _g (a)
Correspond to the CMY equivalent grays of the print,
The reflectivity of paper white, the reflectance when the input dot% is 100% for both CMY, and the reflectance when the input dot% is a% for both CMY.

In step (c) of FIG. 8, the CMYK patch images are printed out by the printer, the reflectance of each patch is measured, and the CMY3
Gray patch data in which the color is simultaneously changed to 0%, 10%,..., 100% is created, a gray patch image is created by a printer, and the reflectance of each patch of the gray patch image is created by a colorimeter. Is measured. Here, Y data of XYZ is adopted in accordance with the case of gray for printing.

Note that, similarly, when a printer profile has already been obtained or created, it is unnecessary to print out or measure a new gray patch image, and it is sufficient to extract necessary data from the printer profile.

In step (d) of FIG. 8, the aforementioned (5)
-(8), the tone characteristics P _c (a), P _M (a), P _Y (a),
It calculates a P _K (a), the printer, the input halftone dot% of the CMY equivalent amount gray tone characteristics P _g which represents the effective dot% for (a) (a), P g (a) = (p g0 - p _g (a)) / (p _g0 −p _g1 ) (14)

Here, p _g0 , p _g1 , and p _g (a)
Correspond to the CMY equivalent grays of the print,
The reflectivity of paper white, the reflectance when the input dot% is 100% for both CMY, and the reflectance when the input dot% is a% for both CMY.

Further, in step (e) of FIG.
Four one-dimensional conversion definitions represented by equations (9) to (12)
S_c(A), S_M(A), S_Y(A), S_KFind (a)
Along with the printer's CMY equivalent gray tone characteristic function
P_gThe printer's CMY equivalence is the inverse of (a).
The function for converting the effective net% (b) of the ray into the input net% is P _g
^-1When expressed by (b), S_g(A) = P_g ^-1(T_g(A)) The gray color conversion definition defined by (15) is calculated.

In actual color conversion, for each of CMY, S _c '(a) = w _c · S _c (a) + (1−w _c ) · S _g (a) (16) S _M '(A) = w _M · S _M (a) + (1−w _M ) · S _g (a) (17) S _Y ' (a) = w _Y · S _Y (a) + (1− w _Y ) · S _g (a) (18) where w _c , w _M , and w _Y are weight coefficients that can be adjusted to satisfy −1 ≦ w _c , w _M , and w _Y ≦ 1. The color conversion is performed independently for each of the CMY in accordance with the one-dimensional color conversion definition expressed by the following equation. For K, the one-dimensional color conversion definition expressed by the above-mentioned equation (12), that is, S _k (a) = P _g ^-1 (T _g (a))... (19) Color conversion is performed.

Here, regarding the equations (16) to (18), the weighting factors w _c , w _M , and w _Y are fixedly determined, and the one-dimensional color conversion definitions S _c ′ (a) and S _M ′ (a ), S _Y ′ (a) may be fixedly calculated in advance, and the adjustment of the values of w _c , w _M , and w _Y is left to the operator who intends to print out the proof image, and the adjustment by the operator is performed. After waiting, the one-dimensional color conversion definitions S _c ′ (a), S _M ′ (a) and S _Y ′ (a) may be calculated. Here, the weighting factors w _c , w _M , and w _Y may be adjusted independently of each other, and are always set to the same value, that is, w is adjusted as w = w _c = w _M = w _Y. It may be.

In order to match the proof image with the printed matter, gray balance is also one of the important factors. If the above-described one-dimensional color conversion definition considering the gray gradation characteristics is adopted, the printed matter is There is a possibility that a more similar proof image can be obtained.

FIG. 12 is a functional block diagram of an embodiment of the color conversion apparatus of the present invention.

This color conversion apparatus is realized by combining the personal computer 50 shown in FIGS. 2 and 3 with a program executed by the personal computer 50.

FIG. 12 shows a one-dimensional color conversion definition storage unit 501 and a four-dimensional color conversion definition storage unit 502.

The one-dimensional color conversion definition storage unit 501 stores C conversion definitions 501C, M conversion definitions 501M, Y conversion definitions 501Y, and K conversion definitions 501K calculated based on the above-described equations (9) to (12). Is stored. Alternatively, the C conversion definition 501C, the M conversion definition 501M, and the Y conversion definition 501Y stored in the one-dimensional color conversion definition storage unit 501 are calculated based on the above-described equations (16) to (18). There may be. Or (1
The one-dimensional color conversion definitions S _c (a), S _M (a), and S _Y (a) and the one-dimensional gray color conversion definition S _g (a) before calculation based on equations (6) to (18) are performed. Are stored in pairs, and the weighting factors w _c , w _M , w
Waiting for adjustment of _Y , S _c '(a), S _M ' (a), S _Y '
(A) may be calculated.

On the other hand, in the four-dimensional color conversion definition storage unit 502, the CMY including the combination of the print profile T and the inverse conversion printer profile P- ¹ described with reference to FIG.
A K4D color conversion definition 502CMYK is stored.

Here, the one-dimensional color conversion definition storage unit 501,
The four-dimensional color conversion definition storage unit 502 is set in the hard disk device 513 shown in FIG. 3 on hardware.

The color conversion apparatus shown in FIG. 12 is provided with a color conversion mode designation section 503. The one-dimensional color conversion definition storage unit 50
The four one-dimensional color conversion definitions C, M,
Y, K conversion definitions 501C, 501M, 501Y, 5
A mode in which color conversion according to 01K or a mode in which color conversion in accordance with CMYK four-dimensional color conversion definition 502 CMYK stored in the four-dimensional color conversion definition storage unit 502 is designated. If you want to perform high-speed color conversion, the color conversion mode that follows the one-dimensional color conversion definition is specified. If you want to obtain a more accurate proof image at the expense of high-speed color conversion, The color conversion mode according to the color conversion definition is specified.

The keyboard 53 or mouse 54 shown in FIGS. 2 and 3 plays the role of the color conversion mode designating section 503 in hardware.

When the mode for performing color conversion in accordance with the one-dimensional color conversion definition is specified by the color conversion mode specifying unit 503, the four CMYK conversion definitions 501C, 501M, 501 stored in the one-dimensional color conversion definition storage unit 501.
When Y and 501K are read and input to the color conversion unit 504, while the color conversion mode specifying unit 503 specifies a mode for performing color conversion in accordance with the four-dimensional color conversion definition,
CMY stored in the four-dimensional color conversion definition storage unit 502
The K4D conversion definition 502CMYK is read and input to the color conversion unit 504.

After the one-dimensional or four-dimensional color conversion definition is input to the color conversion unit 504 as described above,
1 is input from a workstation 20 shown in FIG. 1 to a personal computer 50 (see FIGS. 1 to 3) in which the color conversion device shown in FIG. , The PDL format image data is converted to bitmap format image data by RIP, and the bitmap format
Image data defined in the YK color space is input to the color conversion unit 504, and color conversion is performed in accordance with the one-dimensional or four-dimensional color conversion definition input to the color conversion unit 504. (See FIG. 1), CMYK image data for outputting a proof image is generated.

The CMYK image data generated by the color conversion in the color conversion section 504 is transmitted to the printer 60, and the printer 60 outputs a proof image of a color that matches the print color.

Here, when the one-dimensional color conversion definition is used in the color conversion unit 504, high-speed color conversion is performed and a proof image is immediately output, while the four-dimensional color conversion definition is output in the color conversion unit 504. When used, the color conversion takes time, but a proof image with a color closer to the color of the printed matter is output. However, even when color conversion is performed using the one-dimensional color conversion definition, in this embodiment, the color conversion is performed such that the dot gain characteristics of printing are reproduced on the print output, so that considerably high precision is achieved. A proof image can be obtained.

FIG. 13 is a diagram showing an embodiment of the color conversion program storage medium of the present invention.

The type of the storage medium 600 shown in FIG. 13 does not matter as long as it is a storage medium storing the color conversion program 610. For example, the CD-RO shown in FIG.
When the color conversion program 610 is stored in the M110, the CD-ROM 110 is pointed out. When the color conversion program is loaded and stored in the hard disk drive 513 shown in FIG. The color conversion program 610
Is downloaded to the floppy disk 100 shown in FIG.

Here, the color conversion program 610 stored in the storage medium 600 shown in FIG. 13 includes one-dimensional color conversion means 611, four-dimensional color conversion means 612, and other various means.

The one-dimensional color conversion means 611 and the four-dimensional color conversion means 612 correspond to the color conversion unit 5 of the color conversion apparatus shown in FIG.
The one-dimensional color conversion means 611 includes the C, M, Y and K conversion definitions 501C and 50 stored in the one-dimensional color conversion definition storage unit 501.
1M, 501Y and 501K are read out and the color conversion unit 50 is read out.
4, the CMYK image data for printing is converted into CMYK image data for a printer in accordance with the conversion definitions of C, M, Y, and K. The four-dimensional color conversion means 612 includes: , Four-dimensional color conversion definition storage unit 502
CMYK four-dimensional conversion definition 502CMY stored in
When K is read and input to the color conversion unit 504,
This is means for converting CMYK image data for printing into CMYK image data for a printer in accordance with the CMYK four-dimensional conversion definition 502 CMYK.

Other means constituting the color conversion program 610 shown in FIG. 13 include, for example, means for supporting the operation of creating the four-dimensional or one-dimensional color conversion definition described with reference to FIGS. Means for securing the one-dimensional color conversion definition storage unit 501 and the four-dimensional color conversion definition storage unit 502 shown in FIG. 12 in the hard disk device 513 shown in FIG. 3, and storing and managing various color conversion definitions therein; And means for receiving the operation of the keyboard 53 and the mouse 54 shown in FIG. 3 and decoding the operation to specify the color conversion mode.

[0129]

As described above, according to the present invention, high-speed color conversion can be performed by employing the one-dimensional color conversion definition.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a printing and proof image forming system to which an embodiment of the present invention is applied.

FIG. 2 is an external perspective view of the personal computer shown by one block in FIG.

FIG. 3 is a hardware configuration diagram of a personal computer.

FIG. 4 is a flowchart illustrating a procedure for creating a four-dimensional color conversion definition.

FIG. 5 is a conceptual diagram of a print profile.

FIG. 6 is a conceptual diagram of a printer profile.

FIG. 7 illustrates a color conversion definition in which a print profile and a printer profile are combined.

FIG. 8 is an explanatory diagram of a method for creating a one-dimensional color conversion definition.

FIG. 9 is a diagram illustrating an example of gradation characteristics for C (cyan).

FIG. 10 relates to C (cyan). FIG. 10 is a diagram showing the tone characteristics of printing (solid line) and the tone characteristics of print output (dashed line) also shown in FIG. 9.

FIG. 11 is a diagram showing a standardized gradation characteristic curve for C (cyan).

FIG. 12 is a functional block diagram of a color conversion device according to an embodiment of the present invention.

FIG. 13 is a diagram showing an embodiment of a color conversion program storage medium of the present invention.

[Explanation of symbols]

 Reference Signs List 10 color scanner 20 workstation 30 film printer 40 printing machine 41 print image 50 personal computer 51 main unit 51a floppy disk loading port 51b CD-ROM loading 52 image display device 52a display screen 53 keyboard 54 mouse 60 printer 61 proof image 100 floppy disk 110 CD-ROM 200 Colorimeter 501 1D color conversion definition storage unit 501C C conversion definition 501M M conversion definition 501Y Y conversion definition 501K K conversion definition 502 4D color conversion definition storage unit 502 CMYK CMYK 4D color conversion definition 503 Color conversion mode Designation section 504 Color conversion section 511 CPU 512 Main memory 513 Hard disk drive 514 FDD driver 515 CD-ROM driver 516 I / O interface Interface 517 printer interface 600 storage medium 610 color conversion program 611 1-dimensional color conversion unit 612 4-dimensional color transform

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2C262 AA24 AA29 AB11 AC03 BA09 BB03 BC11 EA12 5B057 AA12 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE17 CH11 CH20 5C077 LL12 LL18 LL19 MP08 PP33 PP37 P0323T035C03 LB01 MA05 NA03 NA11 PA03

Claims (13)

[Claims] An image based on the image data for printing is output by using a printer that outputs an image based on image data representing an input network% of CMYK four colors. A color conversion method for converting image data for the printer to output a proof image that reproduces the color of the image obtained by printing under predetermined printing conditions, the method corresponding to each of CMYK of printing. Input network% (a)
Are converted into effective halftone% by T _c (a), T _M
(A), T _Y (a), T _K (a), CMYK of printer
P _c (a), P _M (a), and P _c (a), P _m (a),
_{Y (a), P K (} a), and, each tone characteristic function P _c of the printer _{(a), P M (a} ), an inverse function of _{P Y (a), P K} (a), the printer , CMYK,
Each function that converts effective net% (b) to input net% is P
^{_{c -1 (b), P M}} -1 (b), P Y -1 (b), when the ^{_{P K -1 (b), S}} c (a) = P c -1 (T c (a) ) S _M (a) = P _M ^-1 (T _M (a)) S _Y (a) = P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K (a )) Four one-dimensional color conversion definitions S _c (a), S
By adopting _M (a), S _Y (a), and S _K (a), CMYK
A color conversion method, wherein the image data for printing is converted into image data for the printer independently for each of the four colors. 2. A gray scale input function% (a) for converting an input halftone (%) in the gray direction into an effective halftone in printing is represented by T _g (a), and an input halftone (%) in the gray direction of the printer is expressed by an effective halftone. is an inverse function of the% gradation characteristic function for converting the P _g (a), the tone characteristics of the gray direction of the printer function P _g (a), the printer,
P _g ^-1 (b) is a function for converting the effective halftone% (b) in the gray direction to the input halftone%, and S _g (a) = P _g ^-1 (T _g ( a)), the four one-dimensional color conversion definitions S _c (a), S _M (a), S
_Y (a), in place of S _K (a), at least one of these four one-dimensional color conversion definition _{S c (a), S M} (a), S Y (a), S K (a) The four color conversion definitions obtained by correcting one color conversion definition based on the color conversion definition S _g (a) in the gray direction are adopted, and the image data for printing is independently converted to the four colors CMYK for the printer. 2. The color conversion method according to claim 1, wherein the image data is converted into image data. 3. Printing for representing an input network% of four colors of CMYK.
Image data representing an input network% of four colors CMYK
Using a printer that outputs an image based on the data,
Printing images based on printing image data under specified printing conditions
Output a proof image that reproduces the color of the image obtained when
Color to convert to image data for the printer
In the conversion method, the reflectance of paper white corresponding to each of CMYK
Each t_c0, T_M0, T_Y0, T_K0, Input network% is 100%
The reflectance at time t_c1, T_M1, T_Y1, T_K1, Enter
When the power grid% is a%, the reflectance is t_c(A), t_M
(A), t_Y(A), t_K(A) CMYK of the printer
The reflectance of paper white corresponding to each is p_c0, P
_M0, P_Y0, P_K0, The reflectance when the input net% is 100%
Each p_c1, P_M1, P_Y1, P_K1, And input network% is a%
Each reflectivity_c(A), p_M(A), p
_Y(A), p_K(A) for each of CMYK for printing
Corresponding, each gradation that converts input halftone% (a) to effective halftone%
Characteristic function T_c(A), T_M(A), T_Y(A), T
_KCompatible with (a) and CMYK printers
To convert the input dot% (a) to the effective dot%
Function P_c(A), P_M(A), P _Y(A), P_K(A)
Each T_c(A) = (t_c0-T_c(A)) / (t_c0-T_c1) T_M(A) = (t_M0-T_M(A)) / (t_M0-T_M1) T_Y(A) = (t_Y0-T_Y(A)) / (t_Y0-T_Y1) T_K(A) = (t_K0-T_K(A)) / (t_K0-T_K1) P_c(A) = (p_c0-P_c(A)) / (p_c0-P_c1) P_M(A) = (p_M0-P_M(A)) / (p_M0-P_M1) P_Y(A) = (p_Y0-P_Y(A)) / (p_Y0-P_Y1) P_K(A) = (p_K0-P_K(A)) / (p_K0-P_K1), And further, each gradation characteristic function P of the printer
_c(A), P_M(A), P_Y(A), P_KIn the inverse function of (a)
Certain printers, corresponding to CMYK, effective
Each function that converts halftone% (b) to input halftone% is P
_c ^-1(B), P_M ^-1(B), P_Y ^-1(B), P_K ^-1In (b)
When expressed, S_c(A) = P_c ^-1(T_c(A)) S_M(A) = P_M ^-1(T_M(A)) S_Y(A) = P_Y ^-1(T_Y(A)) S_K(A) = P_K ^-1(T_K(A)) Four one-dimensional color conversion definitions S represented by_c(A), S
_M(A), S_Y(A), S_KBy adopting (a), CMYK
The image data for printing is independently provided for each of the four colors.
Is converted to image data for the printer.
Color conversion method. 4. Corresponding to CMY equivalent gray for printing.
The reflectance of paper white is t _g0 , the reflectance when input halftone% is 100% for both CMY is t _g1 , the reflectance when input halftone is a% for both CMY is t _g (a), and CMY of the printer corresponding to an equal volume gray, the reflectance of the paper white t _g0, the input halftone dot% is the reflectance when the CMY both 100% p _g1, the reflectance when the input halftone dot% of CMY both a% P _g ( a) and print, CM
The tone characteristic function T _g (a) for converting the input halftone (%) of Y equivalent gray to effective halftone (%) and the input halftone (%) of CMY equivalent gray for the printer are converted to effective halftone (%). gradation characteristic function P _g of _{(a), T g (a} ) = (t g0 -t g (a)) / (t g0 -t g1) P g (a) = (p g0 -p g (a) ) / (P _g0 −p _g1 ), and the printer's CM, which is the inverse function of the printer's CMY equivalent gray tone characteristic function P _g (a).
A function for converting the effective halftone% (b) of the Y equivalent gray to the input halftone percentage is represented by P _g ^-1 (b), and the gray color conversion definition is S _g (a) = P _g ^-1 (T _g (A)), the four one-dimensional color conversion definitions S _c (a), S _M (a), S
Three one-dimensional color conversion definitions S of _Y (a) and S _K (a)
Instead of _c (a), S _M (a), and S _Y (a), S _c ′ (a) = w _c · S _c (a) + (1−w _c ) S _g (a) S _M ′ (A) = w _M · S _M (a) + (1−w _M ) S _g (a) S _Y ′ (a) = w _Y · S _Y (a) + (1−w _Y ) S _g (a) Here, w _c , w _M , and w _Y are adjustable weighting coefficients satisfying 0 ≦ w _c , w _M , w _Y ≦ 1. The three one-dimensional color conversion definitions S _c '(a), S _M ' (a), and S _Y '(a)
And the four one-dimensional color conversion definitions S _c
(A), one of S _M (a), S _Y (a), and S _K (a)
CMYK using one one-dimensional color conversion definition S _K (a)
4. The color conversion method according to claim 3, wherein the image data for printing is converted into image data for the printer independently for each of the four colors. 5. An image based on the image data for printing using a printer which outputs image data for printing representing the input network% of CMYK four colors and an image based on the image data representing the input network% of CMYK four colors. A color conversion device for converting a color of the CMYK four colors into an image data for the printer for outputting a proof image in which colors of the image obtained by printing under predetermined printing conditions are reproduced. Do 4
A one-dimensional color conversion definition storage unit that stores one one-dimensional color conversion definition; and the printer image data using the one-dimensional color conversion definition stored in the one-dimensional color conversion definition storage unit. A one-dimensional color conversion definition storage unit for converting input halftone% (a) into effective halftone% corresponding to each of CMYK for printing. To T _c (a), T _M (a), T _Y (a),
T _K (a), the printer, corresponding to CMYK, the input halftone dot% of each gradation characteristic function of converting (a) the effective _{network% P c (a), P} M (a), P Y (a) , P _K (a) and each tone characteristic function P _c (a), P
Effective halftone% (b) of the printer corresponding to each of CMYK, which is the inverse function of _M (a), _PY (a), _PK (a)
Are converted to _Pc ^-1 (b), P
_{When M} ^-1 (b), P _Y ^-1 (b), and _PK ^-1 (b), S _c (a) = P _c ^-1 (T _c (a)) S _M (a) = P _M ^-1 (T _M (a)) S _Y (a) = P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K (a)) -Dimensional color conversion definition S _c (a), S
A color conversion device for storing _M (a), S _Y (a), and S _K (a). 6. The one-dimensional color conversion definition storage unit stores a tone characteristic function for converting an input halftone (%) in the gray direction of printing into an effective halftone percentage of T _g (a), The tone characteristic function for converting the input dot% (a) into the effective dot% is P
_g (a), gray scale tone function P of the printer
_g is the inverse function of (a), the function of converting the effective gray% (b) in the gray direction of the printer to the input gray% is P
_g ⁻¹ (b) and the one-dimensional color conversion definition in the gray direction is S _g (a) = P _g ⁻¹ (T _g (a)), and the four one-dimensional color conversion definitions S _c (a ), S _M (a), S
_Y (a), in place of S _K (a), at least one of these four one-dimensional color conversion definition _{S c (a), S M} (a), S Y (a), S K (a) 6. The color conversion device according to claim 5, wherein four color conversion definitions obtained by correcting one color conversion definition based on the gray-direction color conversion definition S _g (a) are stored. 7. An image based on the image data for printing, which is based on image data for printing representing the input network% of CMYK four colors, is output by using a printer which outputs an image based on the image data representing the input network% of CMYK four colors. A color conversion device for converting a color of the CMYK four colors into an image data for the printer for outputting a proof image in which colors of the image obtained by printing under predetermined printing conditions are reproduced. Do 4
A one-dimensional color conversion definition storage unit that stores one one-dimensional color conversion definition; and the printer image data using the one-dimensional color conversion definition stored in the one-dimensional color conversion definition storage unit. A one-dimensional color conversion definition storage unit, wherein the one-dimensional color conversion definition storage unit sets the reflectance of paper white corresponding to each of CMYK for printing to t _c0 , t _M0 , and t _M0 , respectively.
t _Y0 , t _K0 , reflectivity when the input net% is 100% are t _c1 , t _M1 , t _Y1 , t _K1 , and reflectivity when the input net% is a% are t _c (a), respectively. t _M (a), t _Y (a),
t _K (a), the reflectance of the paper white corresponding to each of CMYK of the printer is pc ₀ , p _M0 , p _Y0 , p _K0 ,
The reflectances when the input net% is 100% are p _c1 and p
_M1, p _Y1, p _K1, respectively reflectance when the input halftone dot% of _{a% p c (a),} p M (a), p Y (a), the p _K (a), print, CMYK Input network% corresponding to each
Each gradation characteristic function T for converting (a) into effective dot%
_c (a), T _M (a), T _Y (a), T _K (a), and the input network% corresponding to each of CMYK of the printer.
Each gradation characteristic function P for converting (a) to effective dot%
_c (a), P _M (a), P _Y (a), and _PK (a) are respectively expressed as T _c (a) = (t _c0 −t _c (a)) / (t _c0 −t _c1 ) T _M (a) = (t _M0 −t _M (a)) / (t _M0 −t _M1 ) T _Y (a) = (t _Y0 −t _Y (a)) / (t _Y0 −t _Y1 ) T _K ( a) = (t _K0 −t _K (a)) / (t _K0 −t _K1 ) P _c (a) = (p _c0 −p _c (a)) / (p _c0 −p _c1 ) P _M (a) _{= (p M0 -p M (a} )) / (p M0 -p M1) P Y (a) = (p Y0 -p Y (a)) / (p Y0 -p Y1) P K (a) = ( p _K0 −p _K (a)) / (p _K0 −p _K1 ), and further, each gradation characteristic function P
_c (a), P _M (a), P _Y (a), and P _K (a) are converted to effective net% (b) corresponding to CMYK of the printer, which is the inverse function of the printer, to input net%. Each function is P
^{_{c -1 (b), P M}} -1 (b), when expressed in ^{_{P Y -1 (b), P}} K -1 (b), S c (a) = P c -1 (T c (a )) S _M (a) = P _M ^-1 (T _M (a)) S _Y (a) = P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K ( a)) Four one-dimensional color conversion definitions S _c (a), S
A color conversion device for storing _M (a), S _Y (a), and S _K (a). 8. The one-dimensional color conversion definition storage unit stores the reflectance of paper white corresponding to CMY equivalent gray of printing as t _g0 , and the reflectance when the input network% is 100% for both CMY in _tMY . _g1 , the reflectance when the input network% is a% for both CMY is t _g
(A), the printer, corresponding to the CMY equivalent amount gray, the reflectance of the paper white t _g0, the reflectance when the input halftone dot% of CMY both 100% p _g1, the input halftone dot% is CMY both of a% The reflectance at the time is represented by P _g (a), and the gradation characteristic function T _g for converting the input halftone (%) of the CMY equivalent gray to the effective halftone (%) in printing.
(A) and a tone characteristic function P _g (a) for converting the input halftone (%) of CMY equivalent gray of the printer into an effective halftone (%).
_{A, T g (a) = (} t g0 -t g (a)) / (t g0 -t g1) P g (a) = (p g0 -p g (a)) / (p g0 -p g1) And the inverse of the printer's CMY equivalent gray tone characteristic function P _g (a).
A function for converting the effective halftone% (b) of the Y equivalent gray to the input halftone percentage is represented by P _g ^-1 (b), and the gray color conversion definition is S _g (a) = P _g ^-1 (T _g (A)), the four one-dimensional color conversion definitions S _c (a),
Instead of three one-dimensional color conversion definitions S _c (a), S _m (a), and S _y (a) among S _M (a), S _Y (a), and S _K (a), S _c '(A) = w _c · S _c (a) + (1-w _c ) S _g (a) S _M ' (a) = w _M · S _M (a) + (1-w _M ) S _g ( a) S _Y ′ (a) = w _Y · S _Y (a) + (1−w _Y ) S _g (a) where w _c , w _M , and w _Y are 0 ≦ w _c , w _M , w It is an adjustable weight coefficient with _Y ≤ 1. The three one-dimensional color conversion definitions S _c '(a), S _M ' (a), and S _Y '(a)
With storing the said four 1-dimensional color conversion definition _{S c (a), S M} (a), S Y (a), 1 single 1-dimensional color conversion definition S _K of the S _K (a) 8. The color conversion device according to claim 7, wherein (a) is stored. 9. A four-dimensional color conversion definition storage unit for storing a four-dimensional color conversion definition for performing color conversion in which four CMYK colors depend on each other, wherein the color conversion unit stores the one-dimensional color conversion definition storage A mode for converting the image data for printing into image data for the printer using the one-dimensional color conversion definition stored in the storage unit, and a four-dimensional color conversion definition stored in the four-dimensional color conversion definition storage unit. 8. The color conversion device according to claim 5, further comprising a mode for converting the image data for printing into image data for the printer by using the mode. 10. An image based on the print image data using a printer that outputs an image based on the image data representing the CMYK four-color input halftones, using a printer that outputs the CMYK four-color input halftones. A color conversion program storage medium storing a color conversion program for converting the image data for the printer into a proof image that reproduces the color of the image obtained by printing under predetermined printing conditions. Input network% (a) corresponding to each of CMYK for printing
Are converted into effective halftone% by T _c (a), T _M
(A), T _Y (a), T _K (a), CMYK of printer
P _c (a), P _M (a), and P _c (a), P _m (a),
_{Y (a), P K (} a), and, each tone characteristic function P _c of the printer _{(a), P M (a} ), an inverse function of _{P Y (a), P K} (a), the printer , CMYK,
Each function that converts effective net% (b) to input net% is P
^{_{c -1 (b), P M}} -1 (b), P Y -1 (b), when the ^{_{P K -1 (b), S}} c (a) = P c -1 (T c (a) ) S _M (a) = P _M ^-1 (T _M (a)) S _Y (a) = P _Y ^-1 (T _Y (a)) S _K (a) = P _K ^-1 (T _K (a )) Four one-dimensional color conversion definitions S _c (a), S
_M (a), S _Y (a), and S _K (a) are used to convert the printing image data into the CMYK image data for the printer.
A color conversion program storage medium, wherein a color conversion program for independently converting four colors is stored. 11. An input network% (a) in the gray direction of printing.
T _g (a) is a gradation characteristic function for converting the gray scale input halftone percentage (a) into an effective halftone percentage, and P _g (a) is a printer gradation conversion function. P _g ⁻¹ (b) is a function that converts the effective halftone% (b) in the gray direction of the printer into the input halftone%, which is the inverse function of the gray-scale tone function P _g (a), and the gray direction. Is defined as S _g (a) = P _g ^-1 (T _g (a)), the four one-dimensional color conversion definitions S _c (a), S _M (a), S
_Y (a), in place of S _K (a), at least one of these four one-dimensional color conversion definition _{S c (a), S M} (a), S Y (a), S K (a) Using the four color conversion definitions obtained by correcting one color conversion definition based on the color conversion definition S _g (a) in the gray direction, the image data for printing is converted into the image data for the printer for each of the four CMYK colors. 11. The color conversion program storage medium according to claim 10, wherein a color conversion program for independently converting is stored. 12. A print representing an input network% of four colors CMYK.
Image data for CMYK four-color input network%
Using a printer that outputs an image based on image data,
Printing an image based on image data for printing under specified printing conditions
A proof image that reproduces the color of the image obtained by printing.
Convert to image data for the printer for output
A color conversion program that stores a color conversion program
Storage media that correspond to each of CMYK
, The reflectance of paper white is t_c0, T_M0, T_Y0, T_K0,
When the input network% is 100%, the reflectance is t_c1, T
_M1, T_Y1, T_K1, The reflectance when the input net% is a%
Each_c(A), t_M(A), t_Y(A), t_K(A),
Paper white reflectance of linter corresponding to each of CMYK
To p_c0, P_M0, P_Y0, P_K0, Input network% is 100
%, Each reflectivity is p_c1, P_M1, P_Y1, P_K1,
The reflectance when the input net% is a% is p_c(A),
p_M(A), p_Y(A), p_K(A) and print, CM
Input net% (a) corresponding to each of YK is changed to effective net%
Each gradation characteristic function T to be converted_c(A), T_M(A), T
_Y(A), T_K(A) and CMYK of the printer
Convert the input net% (a) to the effective net% corresponding to each
Each gradation characteristic function P_c(A), P_M(A), P _Y(A), P_K
(A) is T_c(A) = (t_c0-T_c(A)) / (t_c0-T_c1) T_M(A) = (t_M0-T_M(A)) / (t_M0-T_M1) T_Y(A) = (t_Y0-T_Y(A)) / (t_Y0-T_Y1) T_K(A) = (t_K0-T_K(A)) / (t_K0-T_K1) P_c(A) = (p_c0-P_c(A)) / (p_c0-P_c1) P_M(A) = (p_M0-P_M(A)) / (p_M0-P_M1) P_Y(A) = (p_Y0-P_Y(A)) / (p_Y0-P_Y1) P_K(A) = (p_K0-P_K(A)) / (p_K0-P_K1), And further, each gradation characteristic function P of the printer
_c(A), P_M(A), P_Y(A), P_KIn the inverse function of (a)
Certain printers, corresponding to CMYK, effective
Each function that converts halftone% (b) to input halftone% is P
_c ^-1(B), P_M ^-1(B), P_Y ^-1(B), P_K ^-1In (b)
When expressed, S_c(A) = P_c ^-1(T_c(A)) S_M(A) = P_M ^-1(T_M(A)) S_Y(A) = P_Y ^-1(T_Y(A)) S_K(A) = P_K ^-1(T_K(A)) Four one-dimensional color conversion definitions S represented by_c(A), S
_M(A), S_Y(A), S_K(A) using the printing
To CMYK image data for the printer
Color conversion program that converts each color independently
A color conversion program characterized by storing
Storage medium. 13. A printing method which corresponds to CMY equivalent gray.
The reflectance of paper white is t _g0, Input network% is 100 for both CMY
% When the reflectance is t_g1, Input network% is a% for both CMY
The reflectance at the time is t_g(A), printer CMY equivalents
The reflectance of paper white corresponding to the ray is t_g0, Input network% is CM
The reflectance when Y is 100% is p_g1, Input network% is CM
When Y is a%, the reflectance is P_g(A)
Convert CMY equivalent gray input net% (a) to effective net%
Tone function T_g(A) and CMY of the printer
Tone for converting input gray% (a) of equivalent gray to effective gray%
Characteristic function P_g(A), T_g(A) = (t_g0-T_g(A)) / (t_g0-T_g1) P_g(A) = (p_g0-P_g(A)) / (p_g0-P_g1) And the printer's CMY equivalent gray scale
Characteristic function P_gThe CM of the printer, which is the inverse function of (a)
A function for converting the effective net% (b) of the Y equivalent gray
Number P_g ^-1(B), and gray color conversion definition
To S_g(A) = P_g ^-1(T_g(A)) where the four one-dimensional color conversion definitions S_c(A), S_M(A), S
_Y(A), S_KThree one-dimensional color conversion definitions S in (a)
_c(A), S_M(A), S_YInstead of (a), S_c’(A) = w_c・ S_c(A) + (1-w)_c) S_g(A) S_M’(A) = w_M・ S_M(A) + (1-w)_M) S_g(A) S_Y’(A) = w_Y・ S_Y(A) + (1-w)_Y) S_g(A) where w_c, W_M, W_YIs 0 ≦ w_c, W_M, W_YAdjustment of ≤1
It is a flexible weighting factor. Three primary orders represented by
Original color conversion definition S_c’(A), S_M’(A), S_Y’(A)
And the four one-dimensional color conversion definitions S
_c(A), S_M(A), S_Y(A), S_KOne of (a)
One-dimensional color conversion definition S_K(A) using the printing
To CMYK image data for the printer
Color conversion program that converts each color independently
13. The color according to claim 12, wherein is stored.
Conversion program storage medium.