JP2002281332A - Color transformation device and method, and program and recording medium therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a color transformation device by which color reproduction under color matching conditions suitable to various image objects constituting an inputted image is realized with comparatively a small amount of hardware at high speed. SOLUTION: In the color transformation device 210 to transform inputted image data expressed by an m-dimensional color space into a control signal of an optional color image output device 301, a control signal value of an output device corresponding to a lattice point of an (m+n) dimensional coordinate including the color matching conditions as coordinate axes is stored as a lookup table and color transformation of the control signal is performed by an interpolating operation of an m+n dimensional lookup table by using inputted color data and the color matching conditions as input. For example, a means 215 to determine color compression rate to a color reproduction range owned by the output device 301 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color conversion device for converting an arbitrary color image signal into a control signal of an arbitrary color image output device having a limited color reproduction range, a color conversion method, a program and a program therefor. It relates to a recorded storage medium.

[0002]

2. Description of the Related Art In recent years, in a multimedia system centered on a host computer, a color matching system (CMS) for performing color matching processing of image data between an input device and an output device has been actively developed. Representative CMS
Apple's ColorSync (TM), which is a framework for converting image signals in an input device-dependent color space (Device Dependent Color Space) into device-independent color space (Device Independent Co
lor Space), and by converting image signals in a device-independent color space to a color space that depends on the output device, a common CMS is realized on the system.

Data representing conversion characteristics for this conversion process is called a profile, which is prepared in the host computer for each device, and which automatically or manually selects an image signal according to the conversion characteristics of the profile. Is converted. In the above color matching system, color conversion of an input signal into an output signal via a device-independent color space enables colorimetrically consistent color reproduction. Generally, the color gamut of an electrophotographic or ink-jet printer is narrower than the color gamut of a television or a CRT display, and conventionally, when the color gamut of an input color image is different from the color gamut of an output device. There are corresponding color correction methods.
In the image processing method disclosed in Japanese Patent No. 88708, a method of extracting a color distribution of an input image and performing color space compression based on a relationship between high chroma data of each hue and a color reproduction range of an image output device is used. However, it has been difficult to perform color conversion according to the compression parameters at high speed.

Further, image data is received from a scanner or a host computer, and a plurality of output color components C (Cyan) and M (Ma) are used as control signals for an image forming apparatus such as a color copying machine.
zenta), Y (Yellow), and K (blacK) are subjected to compression mapping and color conversion of a uniform color reproduction range, image data is sent, and output by an image forming apparatus such as a color copying machine. It is difficult to optimally reproduce the colors of a compound document displayed in a .For example, by combining different types of objects depending on the page description language, it is possible to combine both monochrome and color photos, graphics, text, etc. Because documents can be created, if compression mapping and color conversion of the color gamut according to the output of the photo are performed, the text and graphics in the same document will look faded and the impact will be lost, or reverse If color mapping and color conversion are performed in accordance with the business graphics and color reproduction is performed with high saturation However, since the color of the photographic image is damaged or the color selected as the background color also has a high density, there has been a problem that characters on the background color are difficult to read.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 9-282471 discloses a method of determining the characteristics of each pixel based on the image type (character, graphic, raster image data) in a page description language. Halftone processing, gamma correction,
An image output control device capable of performing a process related to each print quality such as a filter process and a masking process is disclosed. Japanese Patent Application Laid-Open No. 9-193377 discloses a color printing apparatus that refers to the contents of print data, determines an attribute related to color correction for each object, and selects a color correction function corresponding to the determined attribute. Have been. However, in this device, it is difficult to control the detailed color correction according to the attribute of the determined object, and it is not possible to achieve both legibility of characters and line drawings on the background color.

[0006]

When an image is output by an image forming apparatus or the like by performing color conversion using the above-described conventional technique, compression of a color reproduction range optimal for various image object attributes is performed. It has been difficult to perform high-speed color conversion while controlling color matching conditions such as parameters and chromatic adaptation parameters. In other words, color reproduction is performed at a density that is finely tuned according to the attributes (for example, font size and line thickness) and properties (for example, color distribution of the high saturation portion of the image object) of various print objects constituting the image. If this is attempted, a plurality of color conversion parameters for each color matching condition corresponding to the attribute or property are held, or in each case, the color reproduction range is compressed and the calculation relating to the perceived amount of color appearance is performed. Had to be converted to a control signal.

Therefore, a first object of the present invention is to solve these conventional problems and to relatively reproduce color in a color image output device under color matching conditions adapted to various image objects constituting an input image. An object of the present invention is to provide a color conversion device which can be realized at high speed with a small amount of hardware (corresponding to claim 1). A second object of the present invention is to maximize the color reproduction range of a color image output device for an image object constituting an input image, in particular, for a photographic image,
Another object of the present invention is to provide a color conversion device capable of realizing color reproduction with excellent gradation continuity at a high speed with a relatively small amount of hardware (corresponding to claim 2).

A third object of the present invention is to provide a color image output apparatus adapted to the attributes of various image objects constituting an input image to perform color reproduction including compression to a color reproduction range with a relatively small amount of hardware. An object of the present invention is to provide a color conversion device which can be realized at high speed (corresponding to claim 3). Further, a fourth object of the present invention is to make it easy for the image objects constituting the input image to be easily recognized by characters and line drawings on a background color without noticeable defects such as color differences in a document. An object of the present invention is to provide a color conversion device capable of realizing color reproduction of a composite document at a high speed with a relatively small amount of hardware.

A fifth object of the present invention is to provide a color conversion which can realize color reproduction assuming an optimal color appearance for various image object attributes constituting an input image with a relatively small amount of hardware at a high speed. That is, an apparatus is provided (corresponding to claim 5). Further, a sixth object of the present invention is to provide a color conversion apparatus capable of realizing color reproduction for matching the appearance of characters and line drawings on the background color of an image object constituting an input image, with a relatively small amount of hardware at high speed. (Corresponding to claim 6).

A seventh object of the present invention is to perform color matching with a relatively small amount of hardware within an optimum color image forming apparatus total color material amount limit range with respect to attributes of various image objects constituting an input image. An object of the present invention is to provide a color conversion device that can be realized at high speed (corresponding to claim 7). Further, an eighth object of the present invention is to provide a color image forming apparatus which is suitable for various image objects constituting an input image, in particular, characters and line drawings on a background, within a color material total amount limit range of an optimal color image forming apparatus. An object of the present invention is to provide a color conversion device capable of realizing high-speed matching with a relatively small amount of hardware.
Corresponding to).

A ninth object of the present invention is to provide a color conversion method capable of realizing color reproduction under a color matching condition adapted to various image objects constituting an input image at high speed. 9). It is a tenth object of the present invention to provide a color conversion method capable of realizing color reproduction at high speed under an optimum color matching condition for an image object on a background constituting an input image (claim 10). Corresponding to).

An eleventh object of the present invention is to provide a color conversion program capable of realizing color reproduction under color matching conditions adapted to various image objects constituting an input image at high speed. (Corresponds to item 11). A twelfth object of the present invention is to provide a color conversion program capable of realizing color reproduction under an optimal color matching condition at a high speed on an image object on a background constituting an input image. 12).

[0013]

In order to achieve the above object, a first aspect of the present invention is to convert input image data expressed in an m-dimensional color space into a control signal of an arbitrary color image output device. In the color conversion device for conversion, a control signal value of the color image output device corresponding to a grid point of (m + n) -dimensional coordinates including a color matching condition as a coordinate axis is stored as an (m + n) -dimensional lookup table. Means, and color conversion means for performing color conversion to the control signal by interpolation of the (m + n) -dimensional lookup table which receives input color data represented in the m-dimensional color space and color matching conditions as inputs. (Claim 1
Corresponding to).

According to a second aspect of the present invention, the color matching condition in the first aspect is color-converted as a color compression ratio of input image data to a color reproduction range of the color image output device. (Corresponding to claim 2). According to a third aspect of the present invention, the color conversion condition according to the first aspect of the present invention is obtained by converting the color matching condition as a color compression direction relating to saturation and lightness on a constant hue plane for an input color outside the color reproduction range of the color image output device. (Corresponding to claim 3). A fourth invention according to the present invention is the color conversion device according to the third invention, wherein the extraction means for extracting background color information on which the predetermined image object is formed, and input of the background color information and the predetermined image object Determining means for determining the color compression direction according to the color data (corresponding to claim 4).

According to a fifth aspect of the present invention, the color matching condition in the first aspect is color-converted as a color adaptation parameter (corresponding to claim 5). A sixth invention according to the present invention is the color conversion device according to the fifth invention, wherein the extraction means for extracting background color information on which the predetermined image object is formed, and input of the background color information and the predetermined image object Determining means for determining a color adaptation parameter according to the color data (corresponding to claim 6). According to a seventh aspect of the present invention, the color matching condition in the first aspect is color-converted as a color material total amount limit value of a color image output apparatus that forms an image using a plurality of color materials. 7).

According to an eighth aspect of the present invention, in the color conversion apparatus according to the seventh aspect, there is provided an extracting means for extracting color information of a background on which a predetermined image object is formed; Determining means for determining a color material total amount limit value according to the input color data of the object (corresponding to claim 8). According to a ninth aspect of the present invention, in a color conversion method for converting input image data represented in an m-dimensional color space into a control signal of an arbitrary color image output device, a color matching condition is included as a coordinate axis (m (n) The control signal values of the color image output device corresponding to the lattice points of the dimensional coordinates are set in advance in an (m + n) -dimensional lookup table, and the input color data represented in the m-dimensional color space is color-matched. (M
(+ n) Color conversion into the control signal is performed by interpolation of a dimensional lookup table (corresponding to claim 9).

According to a tenth aspect of the present invention, in the color conversion method according to the ninth aspect, color information of a background on which a predetermined image object is formed is extracted, and input of the background color information and the predetermined image object is performed. The color matching condition is determined according to the color data.
0). An eleventh invention according to the present invention is a recording medium storing a program for converting input image data expressed in an m-dimensional color space into a control signal of an arbitrary color image output device, comprising: A step of setting and storing a control signal value of the color image output device corresponding to a grid point of (m + n) -dimensional coordinates including a condition as a coordinate axis in an (m + n) -dimensional lookup table; The procedure of performing color conversion to the control signal by interpolation of the (m + n) -dimensional lookup table that receives input color data expressed in space and color matching conditions as inputs is recorded as a program to be executed by a computer. (Corresponding to claim 11).

According to a twelfth aspect of the present invention, there is provided a recording medium according to the eleventh aspect, wherein a procedure for extracting color information of a background on which a predetermined image object is formed; The procedure for determining the color matching condition in accordance with the input color data is recorded as a program to be executed by a computer (corresponding to claim 12).

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Configuration of Image Processing System) FIG. 1 is a block diagram of a color conversion apparatus 1 according to a first embodiment of the present invention. Figure 1
Is a computer for controlling the color conversion device 210. Computer 101
Upon receiving an output command from the operator, a color conversion device converts image data captured by capturing an image or image data of a composite document such as monochrome and color photographs, graphics, and texts created by various DTP software. Send to 210.

The color converter 210 analyzes the image data transmitted from the computer 101 and sends a plurality of output color components C (Cya) as control signals to an image forming apparatus such as a color copying machine.
n), M (Mazenta), Y (Yellow), and K (blacK) are executed, and the result is transferred to the image forming apparatus 301. Then, the image forming apparatus 301 prints the transmitted image. The color conversion device 210 may be mounted inside a color printer to perform color conversion,
It may be implemented in the computer 101 side. Also,
The image data may be sent to a printer after being mounted in a printer controller provided independently of the color printer and subjected to color conversion. Further, in the present embodiment, it is also possible to execute by software, and in that case, it can be executed by a printer driver existing as a program in a computer.

(Configuration of Color Conversion Apparatus 1) In FIG. 1, the color conversion apparatus 210 includes an image object type determination unit 20.
1 and the image forming apparatus 301 according to the attributes and properties of the image object, specifically, the color distribution of the high saturation portion in the image object with respect to the input image data.
And a control signal (CMYK) for the image forming apparatus 301 based on the input color signal and the color compression rate set by the color compression rate determining means 215. Color conversion means 202 for converting to
In accordance with a drawing instruction described in a page description language (PDL) or the like, development, synthesis,
A drawing unit 203 that performs γ conversion, halftone processing, and the like, and temporarily stores input data when color distribution is detected by the color compression ratio determining unit 215 and a print image for one page drawn by the drawing unit 203. Image storage means (storage buffer) 204 to be stored.

Of course, the color conversion device 210 of the present invention converts the color conversion means 202 for obtaining a printer output faithful to the displayed image and the resolution corresponding to each model in accordance with the characteristics of the image display device and the characteristics of the printer. It may be constituted by a resolution conversion means or the like. Note that the image data input to this color conversion device is more specifically RGB (green, blue,
Red) gradation data, and the number of gradations of each color component is generally 8 bits = 256 gradations, but L * a * b
* And the number of gradations are also 64 or 512.
Such a case is acceptable.

(Operation of Color Conversion Apparatus 1) Next, the operation of the color conversion apparatus 210 in FIG. 1 will be described. The object type determining unit 201 receives image data of a compound document or the like, recognizes the type of the image object (character code, graphic code, raster image data), and controls the color compression ratio within the color reproduction range of the printer. It is determined whether or not to perform the processing, and the image data is sent to the color conversion unit 202 or the color compression ratio determination unit 215. For example, image data such as fonts and graphics sent directly from the object type determination unit 201 to the color conversion unit 202 is stored in the color conversion unit 20.
2, the image forming apparatus (printer) 30 performs color conversion based on the characteristics of the image forming apparatus (printer) 301.
A plurality of output color components C (Cyan) and M
(Mazenta), Y (Yellow), and K (blacK) data, and are converted to the drawing unit 203 and the image storage unit (storage buffer).
204.

FIGS. 2 and 3 are explanatory diagrams of the principle of the memory map interpolation of the color conversion means in FIG. 3
Output color components C (Cyan) and M are obtained from gradation data of RGB (green, blue, red), which is a three-dimensional color space, and L * a * b * data.
(Mazenta), Y (Yellow), and K (blacK) data are converted into CMYK by memory map interpolation. As shown in FIG. 2, when the RGB space is used as an input color space, the memory space is divided into three-dimensional figures (here, cubes) of the same type, and an output value P at input coordinates (RGB) is used. Is determined by selecting a cube including the coordinates of the input, outputting the eight points of the selected cube on preset vertices, and the position of the input in the cube (distance from each vertex) , A linear interpolation is performed by a weighted average of the volumes V1 to V8 of the eight small rectangular parallelepipeds divided at the point P. Here, in the case of the present embodiment, the output value Q
Correspond to the C, M, Y, and K values, respectively, and the coordinates (RGB) on the input space used for the interpolation operation have the relationship between the actual input / output (L *, a *, b * -CMYK). Is measured, and using this data, an optimal solution is obtained by a least square method or the like for a CMY combination having (L *, a *, b *, K) as an input, and RGB (L *
The values of C, M, Y, and K for a * b *) are set in advance.

The image image object sent from the object type determining means 201 to the color compression ratio determining means 215 has a maximum saturation value (C) for each hue (H) for each object.
h) is detected. When the input signal is RGB, the calculation as shown in the following equation, the hue (H) is given by equation (3), and the maximum saturation value (C
h) is calculated by equation (4). X = 0.4124 x R + 0.3576 x G + 0.1805 x B Y = 0.2126 x R + 0.7152 x G + 0.0722 x B Z = 0.0193 x R + 0.1192 x G + 0.9505 x B (1) L * = 116 (Y / Y ₀ ) ^1/3 -16, (Y / Y ₀ > 0.008856) a * = 500 [(X / X ₀ ) ^1/3 − (Y / Y ₀ ) ^1/3 ], (X ₀ , Y ₀ , Z ₀ are values of the reference reflecting surface) b * = 200 [(Y / Y ₀ ) ^1/3 − (Z / Z ₀ ) ^1/3 ], (2) Hue: H = atan2 (B *, a *) × 180 / π However, when a = b = 0, C = 0, and when H <0, H = 360 + H (3) Saturation: C = (a ** a * + b) ** b *) ^0.5 (4)

The maximum saturation value (Ch_I) for each hue (H) calculated for each image object and the maximum saturation for each hue (H) which is a preset color reproduction range of the image forming apparatus (printer) 301. The ratio of the degree value (Ch_P) is calculated and sent to the color conversion means 202 as the color compression ratio (α) of the target image object which is the maximum value among all the hues. Color compression ratio: α = MAX (Ch_P / Ch_I) (5) At this time, the color conversion means 202 performs R, G, B, F (= α) → C by interpolation of a four-dimensional lookup table.
M, Y, and K color conversions are performed.

This interpolation operation is a four-dimensional interpolation operation in which the axis of F (= α) is added to the input of the above-mentioned memory map interpolation. Specifically, in a space obtained by dividing the F axis (0.2 <α <1.0) into eight, if the color compression ratio α for the input object is 0.75, α = 0.7 and α = 0. A three-dimensional (RGB) lookup table corresponding to 8 is selected,
Each output value, Q according to the input color value P (RGB)
L (R, G, B) and KU (R, G, B) are obtained by linear interpolation using a weighted average of the volumes V1 to V8 of the eight small rectangular parallelepipeds divided at the point P. Here, the input value Fin (the color compression ratio α = 0.
75) is between PL and PU, and the Q to be calculated is: Q = (QL (R, G, B) + QU (R, G, B)) / 2 (6) (see FIG. 3) ). In the case of this embodiment, the output value Q
Correspond to the C, M, Y, and K values, respectively.

In this four-dimensional lookup table, C, M, Y, and K values corresponding to combinations of representative R, G, B, and α (saturation compression ratio) are set in advance. . Specifically, L * a * b * corresponding to the representative grid point (RGB)
The values (obtained from the expressions (1) and (2)) are color-compressed by the following expression, the actual input / output (L *, a *, b * -CMYK) relationship is measured, and this data is used. , (L *, a *, b *, K) as input, find the optimal solution by the least square method or the like, and obtain the values of C, M, Y, and K for RGB (L * a * b *) Ask for. L * ′ = L * × (Lwhite−Lblack) ÷ 100 + Lblack a * ′ = a * × αb * ′ = b * × α where Lwhite: maximum brightness of the printer (white point) Lblack: minimum brightness of the printer (black point) (7) The interpolation method of the four-dimensional look-up table described above is an example. In actuality, in order to increase the calculation speed, the space formed by the four inputs is divided into 16 vertices of each interpolation target area. Is divided into 24 five-vertex bodies that pass through one grid point that composes the interpolation, and interpolation is performed, but the present invention is not limited thereto.

(Configuration of Color Conversion Apparatus 2) FIG. 4 is a block diagram of a color conversion apparatus according to a second embodiment of the present invention. In FIG. 4, the color conversion device 220 performs image object type determination means 201 and
According to the color and attribute of the image object, specifically, the saturation and lightness of a color outside the color reproduction range of the image forming apparatus 301 on a constant hue plane in accordance with the font size of the character object and the line width of the graphic object. A color compression direction determining unit 225 for determining a color compression direction, and a color for converting an input color signal and a color compression direction set by the color compression direction determining unit 225 into a control signal (CMYK) for the image forming apparatus 301. Conversion means 202 and a page description language (P
DL) for rendering, synthesizing, γ-conversion, halftone processing, etc. into a print image (image data) in accordance with a rendering command described in DL, etc., and a one-page print image rendered by the rendering means 203 Image storage means (storage buffer) 204 for temporarily storing

(Operation of Color Converter 2) Next, the operation of the color converter 220 in FIG. 4 will be described. Image data such as a compound document is received, and the type (character code, graphic code, raster image data) and the contents (type, size, color, thickness, etc.) of the drawing object are recognized by the object type determination means 201, and the image is determined. It is determined whether or not to control the compressed image direction to the color reproduction range of the forming device 301, and the image data is sent to the color conversion unit 202. For example, an image object or image data within the color reproduction range of the image forming apparatus 301 sent from the object type determining unit 201 directly to the color converting unit 202 is transmitted to the color converting unit 202 by the image forming apparatus (printer) 301. By the above-described color conversion using the three-dimensional lookup table based on the characteristics, a plurality of output color components C (Cya) which are control signals of the image forming apparatus (printer) 301 are obtained.
n), M (Mazenta), Y (Yellow), and K (blacK) data, which are sent to the drawing means 203 and the image storage means (storage buffer) 204. Here, processing in the color conversion device 220 when character information is input will be described.

FIG. 5 is an explanatory diagram of the color conversion means in FIG. When the object type is determined by the object type determination means 201 as a character object, at least
The size and color information are extracted, and for example, by equation (8),
According to the size information (S) of the character object to be controlled, the compression direction θ is determined for each hue with a constant hue and within a range from the direction of preserving lightness to the direction of preserving saturation (FIG. 5).
) And sent to the color conversion means 202. θ = −α × S + βh However, when θ <γh, θ = γh θ: Intersection angle with lightness preserving compression direction (see FIG. 5) S: Size information of character object α: Constant βh: Maximum determined for each hue Intersection angle γh: Minimum intersection angle determined for each hue (default compression direction) (8)

At this time, the color conversion means 202
R, G, by interpolation operation of the dimensional lookup table
B, F (= θ) → C, M, Y, K color conversion is performed. In the four-dimensional lookup table, values of C, M, Y, and K corresponding to combinations of representative R, G, B, and θ (color compression directions) are set in advance. In particular,
L * a * b * corresponding to the representative grid point (RGB) ((1),
Among the values (determined from equation (2)), colors within the color reproduction range of the image forming apparatus 301 are stored, and colors outside the color reproduction range of the image forming apparatus 301 are in the direction of θ (see FIG. 5). L * of the outermost shell in the color reproduction range of the image forming apparatus 301 of the same hue
Calculate a * b * value and input / output actual (L *, a *, b * -CMYK)
Is measured, and using this data, (L *, a *,
b *, K) as input, finds an optimal solution by the least square method or the like, and obtains C, M, and RGB for RGB (L * a * b *).
Find the values of Y and K.

(Configuration of Color Conversion Apparatus 3) FIG. 6 is a block diagram of a color conversion apparatus according to a third embodiment of the present invention. In FIG. 6, a color conversion device 230 includes an image object type determination unit 201 and a background color information extraction unit 206 that extracts color information of a background on which a designated image object is formed from input image data. And a color for determining a color compression direction related to saturation and brightness on a hue constant plane for a color outside the color reproduction range of the image forming apparatus 301 according to the attribute and color of the image object and background information on which the image object is formed. Compression direction determining means 23
5, a color conversion means 202 for converting the input color signal and the color compression direction set by the color compression direction determination means 235 into a control signal (CMYK) for the image forming apparatus 301, and a page description language (PDL) Etc., according to a drawing command described in the drawing unit 203 for performing development, synthesis, gamma conversion, halftone processing, etc. on a print image (image data), and temporarily prints one page of the print image drawn by the drawing unit 203. Image storage means (storage buffer) 204 for temporarily storing the image data.

(Operation of Color Converter 3) Next, the operation of the color converter 230 in FIG. 6 will be described. The object type determination unit 201 receives image data such as a compound document, and recognizes the type (character code, graphic code, raster image data) and the content (type, size, color, thickness, etc.) of the drawing object, It is determined whether or not to control the color conversion, and the image data is sent to the color conversion unit 202 or the background color information extraction unit 206.

For example, image data that is sent directly from the object type determination unit 201 to the color conversion unit 202 and that is within the color reproduction range of the image object or graphic or the color reproduction range of the image forming apparatus 301 is sent to the color conversion unit 202. In the above, a plurality of output colors which are control signals of the image forming apparatus (printer) 301 that match the image display as much as possible by the above-described color conversion using the three-dimensional lookup table based on the characteristics of the image forming apparatus (printer) 301 Components C (Cyan), M (Mazenta), Y (Yello
w), converted into K (blacK) data,
It is sent to the image storage means (storage buffer) 204.

FIG. 7 is an explanatory diagram of the background color information extracting means in FIG. For example, image data corresponding to character information outside the color reproduction range of the image forming apparatus 301 sent from the object type determination means 201 to the background color information extraction means 206 Information such as the size and the type of character is extracted, and the area where the character is formed is calculated. As shown in FIG. 7, the background color information extracting means 206 converts the color information in the background of the calculated area into the area in the image developed in the image storage means (storage buffer) 204 as shown in FIG. L * a * b * of all pixels (determined from equations (1) and (2))
, Extracted as an average value (L * g, a * g, b * g), and sends the data to the color compression direction determining means 235.

The color compression direction determining means 235 calculates the color (L * obj, a * obj, b * obj) of the character to be color-converted and the lightness difference (ΔL) between the character color and the background color. Then, in accordance with the lightness difference (ΔL), for example, the compression direction θ is determined for each hue within the range from the lightness preserving direction to the chroma preserving direction by the equation (9) (FIG. 5). ) And sent to the color conversion means 202. θ = −α × ΔL + βh However, when θ <γh, θ = γh θ: intersection angle with the brightness preserving compression direction (see FIG. 5) ΔL: brightness difference between the color of the object and its background color α: constant βh: Maximum intersection angle determined for each hue γh: Minimum intersection angle determined for each hue (default compression direction) (9)

This is because when (L * g-L * obj)> 0, if it is determined that the color of the character to be color-converted and the background color are both close and bright, a high-density color with the same hue is output. (Color difference minimum to saturation preservation) is set. Conversely, as the lightness difference between the color of the character to be color-converted and the background color increases, the compression direction θ ( This indicates that the color is converted to a color that preserves lightness (minimum color difference).
At this time, in the color conversion means 202, R, G, B, F (= θ) by the interpolation operation of the above-described four-dimensional lookup table is used.
→ C, M, Y, K color conversion is performed.

In the four-dimensional lookup table, C, M, Y, and K values corresponding to combinations of representative R, G, B, and θ (color compression directions) are set in advance. Specifically, L * a * b * corresponding to the representative grid point (RGB)
Among the values (determined from the expressions (1) and (2)), the colors within the color reproduction range of the image forming apparatus 301 are stored, and the image forming apparatus 3
For the color outside the color reproduction range of 01, the L * a * b * value of the outermost shell in the color reproduction range of the image forming apparatus 301 having the same hue in the direction of θ (see FIG. 5) is obtained. (L *, a *, b *
−CMYK), and using this data,
An optimal solution is obtained by a least squares method or the like for a combination of CMY with (L *, a *, b *, K) as input, and values of C, M, Y, and K with respect to RGB (L * a * b *) are calculated. Ask.

(Configuration of Color Conversion Apparatus 4) FIG. 8 is a block diagram of a color conversion apparatus according to a fourth embodiment of the present invention. In FIG. 8, a color conversion device 240 includes an image object type determination unit 201 and, for input image data, a color and an attribute of an image object, specifically, a font size of a character object and a line width of a graphic object. A color adaptation parameter determining unit 245 for determining a color adaptation parameter in accordance with the color conversion parameter, and a color conversion unit for converting a color adaptation parameter set by the input color signal into a control signal (CMYK) for the image forming apparatus 301. 202, a drawing unit 203 that performs development, synthesis, γ conversion, halftone processing, and the like on a print image (image data) in accordance with a drawing command described in a page description language (PDL) or the like, and is drawn by the drawing unit 203. Image storage means (storage buffer) 204 for temporarily storing the print image of one page.

(Operation of Color Converter 4) Next, the operation of the color converter 240 in FIG. 8 will be described. Image data such as a compound document is received, and the type (character code, graphic code, raster image data) and the contents (type, size, color, thickness, etc.) of the drawing object are recognized by the object type determination means 201, and the color is determined. It is determined whether or not to control the adaptation parameter.
The image data is sent to 2. Object type determining means 20
For example, the image data of the image object, which is sent directly to the color conversion unit 202 from the
In the above, a plurality of output color components C (Cyan) and M (which are control signals of the image forming apparatus (printer) 301 by the above-described color conversion using a three-dimensional lookup table based on the characteristics of the image forming apparatus (printer) 301). Mazenta), Y
(Yellow) and K (blacK) data are sent to the drawing means 203 and the image storage means (storage buffer) 204. Here, the color conversion device 2 when character information is input
The processing in 40 will be described.

When the object type determination unit 201 determines that the character is a character object, the type, size, and color information of the character are extracted at the same time.
In step 5, for example, according to equation (10), the CI is determined according to the size information (S) of the character object to be controlled.
CIECAM97 proposed by ETCI-31
The luminance La (cd / m2) of the adaptive visual field in the s (color appearance) model is determined and sent to the color conversion means 202. La = −α × S × (1−Lobj / 100) 2 + βLa where, when La <γLa, La = γLa La: luminance of the adaptive visual field (cd / m2) S: size information of the character object Lobj: lightness of the character object α: constant γLa: minimum value βLa: default value determined in the standard observation environment (10) At this time, the color conversion means 202 performs R, G, B, F (= L) by interpolation of the above-described four-dimensional lookup table.
a) → C, M, Y, K color conversion is performed.

In this four-dimensional lookup table, C, M, Y, and K values corresponding to combinations of representative R, G, B, and La (color adaptation parameters) are set in advance. Specifically, the perception amount JCH (defined by the CIECAM97s model) relating to the color appearance under a plurality of viewing environments (color adaptation parameters) corresponding to the representative grid points (RGB) is obtained, and the actual input / output (JCH-CMYK) Is measured, and using this data, an optimal solution is obtained by a least square method or the like for a combination of CMY using (J, C, H, K) as an input, and C, M, Y, and K for RGB are determined. Find the value of

(Configuration of Color Conversion Apparatus 5) FIG. 9 is a block diagram of a color conversion apparatus according to a fifth embodiment of the present invention. In FIG. 9, a color conversion device 250 includes an image object type determination unit 201 and a background color information extraction unit 206 that extracts color information on a background on which a designated image object is formed from input image data. A color adaptation parameter determining unit 255 for determining a color adaptation parameter according to attributes and colors of the image object and background information on which the image object is formed; and an image forming apparatus from the color adaptation parameter set by the input color signal. Color conversion means 2 for converting into a control signal (CMYK) 301
02 and drawing means 203 for executing development, synthesis, gamma conversion, halftone processing and the like on a print image (image data) in accordance with a drawing instruction described in a page description language (PDL) or the like.
And an image storage unit (storage buffer) for temporarily storing a print image of one page drawn by the drawing unit 203
204.

(Operation of Color Converter 5) Next, the operation of the color converter 250 in FIG. 9 will be described. The object type determination unit 201 receives image data such as a compound document, and recognizes the type (character code, graphic code, raster image data) and the content (type, size, color, thickness, etc.) of the drawing object, It is determined whether or not to control the chromatic adaptation parameters, and the image data is sent to the color conversion means 202 or the background color information extraction means 206.
For example, the image data of the image object, which is sent directly from the object type determination unit 201 to the color conversion unit 202, is output from the color conversion unit 202 using a three-dimensional lookup table based on the characteristics of the image forming apparatus (printer) 301. , A plurality of output color components C (Cyan), M (Mazenta), Y (Yellow), and K (blac), which are control signals for the image forming apparatus (printer) 301.
K) The data is converted into data and sent to the drawing means 203 and the image storage means (storage buffer) 204.

For example, the image data corresponding to the character information sent from the object type determining means 201 to the background color information extracting means 206 is processed by the background color information extracting means 206 such as a drawing start address, a character size, and a character type. Information is extracted, and a region where a character is formed is calculated.
As shown in FIG. 7, the background color information extracting means 206 extracts the color information in the background of the calculated area from the image developed in the image storing means (storage buffer) 204, as shown in FIG.
It is extracted as the average value (Yave) of the luminance Y (determined from the equation (1)) of all the pixels in the area, and the data is sent to the chromatic adaptation parameter determining means 255.

In the chromatic adaptation parameter determining means 255, the average value Yave of the luminance of the background color is calculated from the CIE TCI-31 proposed by the CIE TCI-31 using, for example, the equation (11).
The luminance ratio Yb of the background in the CAM 97s (color appearance) model is determined and sent to the color conversion means 202. Yb = −α × (1−Yave / 100) 2 + βYb However, when Yb <γYb, Yb = γYb Yb: luminance ratio of background Yave: luminance average of background color α: constant γYb: minimum value βYb: maximum value ( 11) At this time, in the color conversion means 202, R, G, B, F (= Y
b) → C, M, Y, K color conversion is performed.

In this four-dimensional lookup table, C, M, Y, and K values corresponding to combinations of representative R, G, B, and Yb (color adaptation parameters) are set in advance. Specifically, the perception amount JCH (defined by the CIECAM97s model) relating to the color appearance under a plurality of viewing environments (color adaptation parameters) corresponding to the representative grid points (RGB) is obtained, and the actual input / output (JCH-CMYK) Is measured, and using this data, an optimal solution is obtained by a least square method or the like for a combination of CMY using (J, C, H, K) as an input, and C, M, Y, and K for RGB are determined. Find the value of

(Configuration of Color Conversion Apparatus 6) FIG. 10 is a block diagram of a color conversion apparatus according to a sixth embodiment of the present invention. In FIG. 10, a color conversion device 260 includes an image object type determination unit 201 and a color and an attribute of an image object with respect to input image data, specifically, a font size of a character object and a line width of a graphic object. The control signal for the image forming apparatus 301 is obtained from the color material total amount limit value determining unit 265 for determining the total amount limit value of the color material (CMYK) in accordance with the color material total amount limit value set by the input color signal. CMYK) color conversion means 20
2 and a drawing unit 203 that executes development, synthesis, γ conversion, halftone processing, etc. on a print image (image data) in accordance with a drawing command described in a page description language (PDL) or the like.
And an image storage unit (storage buffer) for temporarily storing a print image of one page drawn by the drawing unit 203
204.

(Operation of Color Converter 6) Next, the operation of the color converter 260 in FIG. 10 will be described. Receiving image data such as a compound document, the object type determining means 201 recognizes the type (character code, graphic code, raster image data) of the drawing object and its contents (type, size, color, thickness, etc.) and It is determined whether or not the control of the limit value is to be performed.
Send image data to Object type determination means 201
For example, the image data of the image object, which is sent directly to the color conversion unit 202 from the image forming apparatus (printer) 301, is based on the characteristic of the maximum color material total amount limit value (for example, 300%) of the image forming apparatus (printer) 301. By the above-described color conversion using the three-dimensional lookup table, a plurality of output color components C (Cyan), M (Mazenta), and Y (Yel), which are control signals of the image forming apparatus (printer) 301, are output.
low), K (blacK) data,
3. Sent to the image storage means (storage buffer) 204.

Here, the processing in the color conversion device 240 when character information is input will be described. When the object type is determined by the object type determination unit 201 as a character object, the type, size, and color information of the character are simultaneously extracted,
In the color material total amount limit value determining unit 265, for example, (1
The total amount limit value T of the color material (CMYK) is determined according to the size information (S) of the character object to be controlled by Expression 2), and is sent to the color conversion unit 202. T = α × S + βLa where T> γT T = γT T: Total amount limit value (%) of color material (CMYK) S: Size information of character object α: Constant γT: Maximum color material total amount limit value βT: Minimum color material total amount limit value (12)

At this time, the color conversion means 202
R, G, by interpolation operation of the dimensional lookup table
B, F (= T) → C, M, Y, K color conversion is performed. In this four-dimensional lookup table, C, M, Y, and K values corresponding to combinations of representative R, G, B, and T (total amount limit values) are set in advance. In particular,
As the line width of the character becomes narrower, the total amount of the coloring material placed on the paper is controlled to be smaller.

(Configuration of Color Conversion Device 7) FIG. 11 is a block diagram of a color conversion device according to a seventh embodiment of the present invention. In FIG. 11, a color conversion device 270 includes an image object type determination unit 201 and a background color information extraction unit 206 that extracts color information of a background on which a designated image object is formed from input image data. When,
Color material total amount limit value determination means 275 for determining the total amount limit value of color material (CMYK) according to the attribute and color of the image object and the background information on which the image object is formed; input color signal and color material total amount limit value determination A color conversion unit 202 for converting the color material total amount limit value set by the unit 275 into a control signal (CMYK) for the image forming apparatus 301 and a drawing command described in a page description language (PDL) or the like. A drawing unit 203 for performing development, synthesis, gamma conversion, halftone processing, and the like on a print image (image data), and an image storage unit for temporarily storing a print image of one page drawn by the drawing unit 203 (Storage buffer) 204.

(Operation of Color Converter 7) Next, the operation of the color converter 270 in FIG. 11 will be described. The object type determination unit 201 receives image data such as a compound document, and recognizes the type (character code, graphic code, raster image data) and the content (type, size, color, thickness, etc.) of the drawing object, It is determined whether or not to control the total amount limit value, and the image data is sent to the color conversion unit 202 or the background color information extraction unit 206.

For example, the image data of the image object, which is sent directly from the object type determination unit 201 to the color conversion unit 202, is converted by the color conversion unit 202 into the maximum color material total amount limit value of the image forming apparatus (printer) 301 (for example, , 300%), a plurality of output color components C (Cyan), M (Mazenta), and Y (control signals) of the image forming apparatus (printer) 301 by the above-described color conversion using the three-dimensional lookup table based on the characteristics. Yello
w), converted into K (blacK) data,
It is sent to the image storage means (storage buffer) 204.

For example, the image data corresponding to the character information sent from the object type determining means 201 to the background color information extracting means 206 is processed by the background color information extracting means 206 such as a drawing start address, a character size, and a character type. Information is extracted, and a region where a character is formed is calculated.
As shown in FIG. 7, the background color information extracting means 206 extracts the color information in the background of the calculated area from the image developed in the image storing means (storage buffer) 204, as shown in FIG.
The luminance is extracted as the average value (Yave) of the luminance Y (determined from equation (1)) of all the pixels in the area, and the data is sent to the color material total amount limit value determining means 275.

In the color material total amount limit value determining means 275,
From the size information (S) of the character object to be controlled and the average value Yave of the luminance of the background color, the size information (S) of the character object and the average value (Yave) of the luminance of the background color are obtained by, for example, equation (13). Depending on the color material (CMYK)
Is determined and sent to the color conversion means 202. T = α1 × S + α2 × (1−Yave / 100) + βLa where T> γT, T = γT T: Total amount limit value (%) of color material (CMYK) S: Size information of character object Yave: Background color Α1, α2: constant γT: maximum color material total amount limit value βT: minimum color material total amount limit value (13)

At this time, the color conversion means 202
R, G, by interpolation operation of the dimensional lookup table
B, F (= T) → C, M, Y, K color conversion is performed. In this four-dimensional lookup table, C, M, Y, and K values corresponding to combinations of representative R, G, B, and T (total amount limit values) are set in advance. In particular,
As the line width of the character becomes thinner or the luminance of the background color rises, the total amount of the coloring material applied on the paper is controlled to be smaller.

(Description of Storage Medium Claim) FIG. 12 is a configuration diagram of an information processing apparatus capable of executing the image processing program of the present invention. In this image processing system, a workstation 400 and a printer 430 are connected. The workstation 400 realizes the function of the above-described color tone correction processing, and includes a display 402, a keyboard 4
05, program reading device 401 and arithmetic processing device 4
03 and the like. The arithmetic processing unit 403 is connected to a CPU capable of executing various commands via a ROM, a RAM, or a bus. The bus is connected to DlSK, which is a mass storage device, and NIC, which communicates with devices on a network.

The program reading device 401 is a storage medium storing various program codes, that is, a floppy disk, a hard disk, an optical disk (CD-R0).
M, CD-R, CD-R / W, DVD-ROM, DVD
-RAM, etc.), a magneto-optical disk, a device that reads program codes stored in a memory card, etc., for example, a floppy disk drive, an optical disk drive,
Such as a magneto-optical disk drive.

The program code stored in the storage medium is read by the program
By executing the program code stored in DlSK or the like by the CPU, the above-described image processing method or the like can be realized. Also, by executing the read program code from the computer, based on the instruction of the program code, an OS (operating system) or device driver running on the computer 400 or a part of the actual processing or It also includes the case where all the operations are performed and the above-described functions are achieved by the processing.

[0062]

As described above, in the first invention (claim 1) according to the present invention, input image data expressed in an m-dimensional color space is converted into a control signal of an arbitrary color image output device. In a color conversion device for conversion, a control signal value of the color image output device corresponding to a grid point of (m + n) -dimensional coordinates including a color matching condition as a coordinate axis is represented by (m +
n) storage means for storing as a dimensional lookup table; and the control signal by interpolation of the (m + n) dimensional lookup table which receives input color data expressed in the m-dimensional color space and color matching conditions as inputs. And a color conversion device capable of realizing color reproduction under a color matching condition adapted to various image objects constituting an input image with a relatively small amount of hardware at a high speed. Can be provided.

In the second invention (claim 2) according to the present invention, the color conversion conditions in the first invention are converted as a color compression ratio of input image data to a color reproduction range of the color image output device. Therefore, the color reproduction range of the color image output device is maximized and the color reproduction with excellent gradation continuity is relatively achieved for the image objects constituting the input image, particularly the photographic image. A color conversion device that can be realized at high speed with a small amount of hardware can be provided.

In the third invention (claim 3) according to the present invention, the color matching conditions in the first invention are determined by setting the saturation on a constant hue plane for an input color outside the color reproduction range of the color image output device. Since color conversion is performed as a color compression direction relating to lightness, a relatively small amount of hardware for color reproduction including compression to a color reproduction range of a color image output device adapted to attributes of various image objects constituting an input image. And a color conversion device that can be realized at high speed.

According to a fourth aspect (claim 4) of the present invention, in the color conversion apparatus according to the third aspect, an extracting means for extracting color information of a background on which a predetermined image object is formed; Since there is a determining means for determining the color compression direction according to the information and the input color data of the predetermined image object, the image object constituting the input image may have a defect such as a color difference in a document. It is possible to provide a color conversion device that can realize color reproduction of a composite document inconspicuously and at the same time the visibility of characters and line drawings on a background color can be realized at a high speed with a relatively small amount of hardware.

In the fifth invention (Claim 5) according to the present invention, the color matching conditions in the first invention are color-converted as chromatic adaptation parameters. A color conversion device capable of realizing color reproduction at a high speed with a relatively small amount of hardware by assuming an optimal color appearance for the attribute of the image.

According to a sixth aspect of the present invention (claim 6), in the color conversion apparatus according to the fifth aspect, an extracting means for extracting background color information on which a predetermined image object is formed, and a background color Determining means for determining a color adaptation parameter in accordance with the information and input color data of a predetermined image object, so that the appearance of the image object constituting the input image, in particular, characters and line drawings on the background color can be matched. A color conversion device capable of realizing color reproduction to be performed at high speed with a relatively small amount of hardware can be provided.

According to a seventh aspect of the present invention (claim 7), the color matching conditions in the first aspect are set as color material total amount limit values of a color image output apparatus for forming an image using a plurality of color materials. Color conversion that can achieve high-speed color matching with a relatively small amount of hardware within the range of the total color material amount of the optimal color image forming apparatus for the attributes of various image objects constituting the input image. Equipment can be provided.

According to an eighth aspect (claim 8) of the present invention, in the color conversion apparatus according to the seventh aspect, an extracting means for extracting color information of a background on which a predetermined image object is formed; Determining means for determining the total color material amount limit value in accordance with the information and the input color data of the predetermined image object; therefore, various image objects constituting the input image, in particular, characters and line drawings on the background However, it is possible to provide a color conversion apparatus capable of realizing color matching within a limited range of the total amount of color materials of an optimal color image forming apparatus at a high speed with a relatively small amount of hardware.

According to a ninth aspect of the present invention, in a color conversion method for converting input image data represented by an m-dimensional color space into a control signal for an arbitrary color image output device, A control signal value of the color image output device corresponding to a grid point of (m + n) -dimensional coordinates including a matching condition as a coordinate axis is preset in an (m + n) -dimensional lookup table, and is represented in the m-dimensional color space. Inputting the input color data and the color matching condition
+ n) Since color conversion into the control signal is performed by interpolation of a dimensional lookup table, color reproduction can be realized at high speed under color matching conditions adapted to various image objects constituting an input image.

The tenth invention according to the present invention (claim 1
0) In the color conversion method according to the ninth aspect, in the color conversion method, color information of a background on which a predetermined image object is formed is extracted, and a color matching condition is determined according to the background color information and input color data of the predetermined image object. Is determined, the color reproduction under the optimal color matching condition can be realized at high speed in the image object on the background constituting the input image.

The eleventh invention according to the present invention (claim 1
1) is a recording medium that records a program for converting input image data represented in an m-dimensional color space into a control signal of an arbitrary color image output device, and includes a color matching condition as a coordinate axis ( a (m + n) -dimensional lookup table for setting and storing control signal values of the color image output device corresponding to grid points of (m + n) -dimensional coordinates, and an input represented by the m-dimensional color space The above-mentioned (m +
n) the procedure of performing color conversion to the control signal by interpolation calculation of the dimensional lookup table is recorded as a program to be executed by a computer, so that a color matching condition adapted to various image objects constituting an input image is recorded. A color conversion program capable of realizing color reproduction at high speed.

The twelfth invention according to the present invention (Claim 1)
2) A procedure for extracting color information of a background on which a predetermined image object is formed in the recording medium according to the eleventh aspect of the present invention, and a method of extracting color information under the color matching conditions adapted to the background color information and the predetermined image object. Reproduction can be realized at high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color conversion apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of memory map interpolation of a color conversion unit in FIG. 1;

FIG. 3 is an explanatory diagram of memory map interpolation of a color conversion unit.

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

FIG. 5 is a diagram illustrating a color conversion unit in FIG. 4;

FIG. 6 is a block diagram of a color conversion unit according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a background color extracting unit in FIG. 6;

FIG. 8 is a block diagram of a color conversion unit according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram of a color conversion apparatus according to a fifth embodiment of the present invention.

FIG. 10 is a block diagram of a color conversion unit according to a sixth embodiment of the present invention.

FIG. 11 is a block diagram of a color conversion apparatus according to a seventh embodiment of the present invention.

FIG. 12 is a configuration diagram of an information processing apparatus capable of executing the image processing program of the present invention.

[Explanation of symbols]

101: computer, 201: object type determining means, 210, 220, 230, 240, 250, 26
0, 270: color conversion device, 202: color conversion means, 203
.., Drawing means, 204, image storage means, 215, color compression ratio determining means, 301, image forming apparatus (printer), 225
... color compression direction determining means, 206 ... background color information extracting means,
235: color compression direction determining means, 245: chromatic adaptation parameter determining means, 255: chromatic adaptation parameter determining means, 26
5 ... Color material total amount limit value determining means, 275 ... Color material total amount limit value determining means, 400 ... Computer, 410 ... Digital still camera, 420 ... Scanner, 430 ... Printer, 4
01 ... program reader, 402 ... display, 4
03: arithmetic processing unit, 404: mouse, 405: keyboard.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA24 AA26 AB11 AB19 BA02 BA16 BA19 BC01 BC15 BC19 CA04 EA12 5B057 AA11 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE17 CE18 CH07 CH11 5C077 LL17 LL18 PP19 MP08 PP08 PP32 PP33 PP36 PP37 PQ08 PQ12 PQ23 RR19 TT02 5C079 HB01 HB03 HB05 HB06 HB08 HB11 KA15 LA02 LA07 LA28 LB02 MA04 MA11 NA03 NA06 NA09 NA11

Claims (12)

[Claims] 1. A color conversion device for converting input image data expressed in an m-dimensional color space into a control signal of an arbitrary color image output device, wherein (m + n) -dimensional coordinates including a color matching condition as a coordinate axis. Storage means for storing, as an (m + n) -dimensional lookup table, control signal values of the color image output device corresponding to the lattice points of the above, and input color data and color matching conditions expressed in the m-dimensional color space. A color conversion unit for performing color conversion to the control signal by interpolation of the (m + n) -dimensional lookup table. 2. The color conversion device according to claim 1, wherein the color matching condition is a color compression ratio of input image data to a color reproduction range of the color image output device. . 3. The color conversion device according to claim 1, wherein the color matching condition is a color compression direction related to saturation and lightness on a hue constant plane for an input color outside the color reproduction range of the color image output device. A color conversion device, comprising: 4. The color conversion apparatus according to claim 3, wherein said color matching condition input means includes extraction means for extracting color information of a background on which a predetermined image object is formed, A color conversion apparatus comprising: a determination unit that determines a color compression direction according to input color data of an image object. 5. The color conversion device according to claim 1, wherein the color matching condition is a color adaptation parameter. 6. A color conversion apparatus according to claim 5, wherein said color matching condition input means includes extraction means for extracting color information of a background on which a predetermined image object is formed, Determining means for determining a color adaptation parameter according to input color data of the image object. 7. The color conversion device according to claim 1, wherein the color matching condition is a color material total amount limit value of a color image output device that forms an image using a plurality of color materials. . 8. The color conversion apparatus according to claim 7, wherein said color matching condition input means includes extraction means for extracting color information of a background on which a predetermined image object is formed; A color conversion device comprising: a determination unit configured to determine the color material total amount limit value according to input color data of an image object. 9. A color conversion method for converting input image data expressed in an m-dimensional color space into a control signal of an arbitrary color image output device, wherein (m + n) -dimensional coordinates including a color matching condition as a coordinate axis. (M + n) -dimensional look-up tables are set in advance for the control signal values of the color image output device corresponding to the lattice points, and the input color data and the color matching conditions represented in the m-dimensional color space are input. A color conversion method comprising performing color conversion to the control signal by interpolation of the (m + n) -dimensional lookup table. 10. The color conversion method according to claim 9, wherein
As the color matching condition, color information of a background on which a predetermined image object is formed is extracted, and a color matching condition is determined according to the color information of the background and input color data of the predetermined image object. Color conversion method. 11. A color conversion program for executing each step of the color conversion method according to claim 9 or 10 by a computer. 12. A computer-readable recording medium, wherein each step of the color conversion method according to claim 9 or 10 is converted into a program, and the program is stored.