JP3416538B2 - Image processing apparatus and method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and the same.
Regarding the method , for example, an image processing apparatus for converting color data of a document image into color data according to set illumination light, and
Regarding the method .

[0002]

2. Description of the Related Art In conventional color printers, colorimetric color reproduction is generally used in color reproduction of an input color image to the printer. Colorimetric color reproduction refers to the case where the chromaticity of the colors of the original image and the reproduced image are equal and their relative luminances are also equal. In this case, since the spectral reflectances of those images are different, the colors are in the same condition. Further, in this color reproduction method, it suffices that the colorimetric values, X, Y, Z (tristimulus values of the object color) obtained by colorimetry by a spectrocolorimeter are the same in the original image and the reproduced image. This is an effective method under observation conditions.

The observation conditions will be described below. As for color perception, as shown in FIG. 10, a light flux enters the object color from the light source, and the reflected light enters the human eye to cause color perception. This process will be described with reference to FIG.
(a) shows the spectral distribution S (λ) of the light source, (b) shows the spectral reflectance distribution p (λ) of the object, and (c) shows the distribution S (λ) p (λ) of the reflected light.

The radiant energy shown in FIG. 11 (c) enters the human eye. The human eye has color matching functions x (λ), y (λ), z (λ) (Fig. 11 (d)). The incident light S (λ) p (λ) is x
(λ), y (λ), and z (λ) are weighted, and three-color separation is performed as shown in FIG. 11 (e). The integrated value is called the color stimulus value of the object color for the observer. Expressing these with formulas,
It becomes like the following formula (1).

Here, the integration range is a visible range wavelength of 380 nm.
To 780 nm. Further, the coefficient K of the equation (1) is a standardization coefficient represented by the equation (2). K = 100 ∫ S (λ) y (λ) dλ… (2)

That is, the above-mentioned colorimetric values X, Y, Z are obtained by the equation (1)
Calculated by As can be seen from the equation (1), colorimetric color reproduction is required to match the colorimetric values X, Y and Z under the same light source. Therefore, the observation condition is that the original image and the reproduced image are observed under the same illumination.

[0007]

When the color reproduction by the printing apparatus is performed, the reference illumination light source is uniquely determined. Therefore, when the printing result is examined under the illumination other than the reference illumination light source, the color difference is May differ greatly.

[0008] The present invention is intended to solve the above problems, applied to the color data included in the print command conversion in accordance with the illumination light when observing the output image, an input under the illumination light source Colorimetric color reproduction of images and printouts
For the purpose of Rukoto to match.

[0009]

The present invention has the following structure as one means for achieving the above object. An image processing apparatus according to the present invention is an image processing apparatus that converts color data of a document image into color data corresponding to any of a plurality of illumination lights, and observes an output image together with a print command from the external device. Input means for inputting information indicating the illumination light at the time, a plurality of conversion means corresponding to each of the plurality of illumination light, based on the information indicating the input illumination light,
The color data included in the print command is measured according to the illumination light when observing the output image, using the selecting unit that selects one of the converting units and the selected converting unit.
A processing unit that performs conversion processing into color data for performing color-based color reproduction processing, and a pattern development unit that performs dot development using the color data obtained by the conversion processing, and the plurality of illumination lights include: A, B and C light sources, which are standard light sources standardized by the International Commission on Illumination, and D55, D65 and D
It is characterized in that it includes any one of 75 light sources, and further includes any light source of a general light source such as a fluorescent lamp and an incandescent lamp.

An image processing method according to the present invention is an image processing method for converting color data of an original image into color data corresponding to any one of a plurality of illumination lights, and an output image together with a print command from the external device. Input the information indicating the illumination light when observing, hold the conversion conditions corresponding to each of the plurality of illumination lights, and select any of the held conversion conditions based on the information indicating the input illumination light Then, using the selected conversion condition, the color data included in the print command is measured according to the illumination light when observing the output image.
Each step has a step of converting to color data for performing color color reproduction processing and performing dot development using the color data obtained by the conversion, and the plurality of illumination lights are standardized by the International Commission on Illumination. Standard light sources, A, B and C light sources,
In addition, any of the D55, D65, and D75 light sources is included, and further, any one of a general light source such as a fluorescent lamp and an incandescent lamp is included.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a circuit configuration of a printing apparatus according to an embodiment of the present invention. The printing device according to the present embodiment includes a host computer 1 and a printing device main body 2.

The host computer 1 sends print data, print commands, etc. to the printing apparatus main body 2 and causes the printing apparatus main body 2 to perform a printing process. The printer body 2 includes a CPU 26a, a ROM 26b, and a RAM 26, like a control unit 26 described later.
It has a microprocessor system including c. That is, the printing apparatus main body 2 includes an interface 21 for exchanging data with the host computer 1, and a color reproduction processing selection table 22-1 used for selecting a color reproduction processing according to the reference illumination light. A color information storage unit 22 that stores information such as a LUT (look-up table) for reproduction processing, a color reproduction processing unit 23 that actually performs color reproduction processing, and various parameters for controlling printing An operation panel 24 that can be used, a data bus 25, a control unit 26 that controls the entire apparatus, a command analysis unit 27 that analyzes print data and print commands from the host computer 1,
A pattern development unit 28 that develops color data such as characters and figures in a memory for each of C, M, Y, and K colors, and an output unit that forms the developed visible color data on a recording paper by a color laser beam printer, for example. Has 29. The control unit 26 includes a CPU 26a that operates by a program, a ROM 26b that stores a program that operates the CPU 26a, and a RAM 26c that is used as a work area of the program in the ROM 26b.

FIG. 2 shows an example of a colorimetric color reproduction process in which original color image data is processed to be equal to the output result of the printing apparatus. Specifically, the original image, which is the R, G, and B luminance data, is C, M, Y, and K that are necessary for output on the printing device.
An example of color reproduction processing for converting to density data of is shown.

In process 1, density conversion processing is performed in which R, G, and B values that are brightness information are subjected to LOG conversion to be C, M, and Y density information. In process 2, from C, M, Y values
Perform the undercolor removal process to extract the value of K (Black). In process 3, the unnecessary absorption characteristics of the C, M, and Y toners or inks are corrected and masking processing is performed to perform appropriate color reproduction. In process 4, γ conversion processing for adjusting the contrast and brightness according to the image is performed.

The above processing is performed in the color reproduction processing section 23 shown in FIG. FIG. 3 shows an example of a print command used when a color image is output by a printing apparatus by selecting an illumination light as a reference for colorimetric color reproduction.
As shown in the figure, the reference illumination light selection command is made up of the identification number of the corresponding command and the illumination light selection parameter. Here, the standard lights A, B, and C are defined by the CIE (International Commission on Illumination) in 1931, and the D55, D65, and D75 are defined by CIE in 1964 as standard light sources for color measurement. Also, for fluorescent lamps, incandescent bulbs, and OHP light sources, commonly used ones are selected and assigned, or light sources having average spectral distribution characteristics of commonly used light sources are virtually assigned. It is also possible.

FIG. 4 shows a color reproduction processing selection table for selecting the color reproduction processing for each reference illumination light source described in FIG. This table stores a pointer to an algorithm for performing an optimum color reproduction process for each reference illumination light source. Here, the optimum color reproduction processing is processing based on the colorimetric color reproduction processing method such that the color appearances of the input color image to the printing device and the output color image of the printing device match.

FIG. 5 shows the appearance of the operation panel 24 of FIG. As shown in the figure, it is composed of an LCD display unit and switches, and the switch at the right end is used for selecting the reference illumination light, selecting a color reproduction processing algorithm for each reference illumination light, and performing color printing. FIG. 6 shows an example of a print command used when a character is colored and output. As shown in the figure, the character print command includes a command identification number, a print position, and data of a character to be printed, and the character color designation command includes a command identification number and an immediate value of RGB luminance data.

7 and 8 are flow charts for explaining the printing process of this embodiment. In FIG. 7, especially, the reference illumination light selection command (FIG. 3) and the color print command (FIG. 6) sent from the host computer 1 are processed,
The operation up to outputting color printed characters is shown. In step S11, the pattern information including the reference illumination light selection command, the color print command, and the character information (character size, etc.) transmitted from the host computer 1 is read, and the process proceeds to step S12 to analyze the command. In step S13, the illumination light selection parameter is extracted from the reference illumination light selection command, the process proceeds to step S14, the pointer is set at the head of the color reproduction process selection table, and the process proceeds to step S15.

In step S15, information corresponding to the extracted illumination light selection parameter (here, a pointer to the color reproduction processing algorithm, that is, when the parameter value is 3,
The color reproduction processing algorithm for standard light D65 is selected. ) From the color reproduction processing selection table. In step S16, the R, G, B brightness data read from the character color designation command is converted into C, M, Y, K density data in the color reproduction processing unit 23 based on the selected color reproduction algorithm. Convert and proceed to step S17. In step S17,
Based on the density data of C, M, Y, and K and the necessary character information, the pattern development unit 28 performs dot development, and the process proceeds to step S18. In step S18, a character is permanently formed as a visible image on a recording sheet or the like based on the data developed in step S17, the sheet is discharged, and the process ends.

As described above, it is possible to analyze a reference illumination light command from the host computer 1, select a color reproduction processing algorithm corresponding to the reference illumination light, and perform color printing of characters based on the algorithm. . FIG. 9 shows the print result of the character A when the color information immediately after step S16 is Y = 100%, M = 50%, C = 25%, and K = 0%.

Since the printer of the output unit 29 of this embodiment is a binary printer, the desired density is expressed by the density of dots. FIG. 8 shows the operation of selecting the reference illumination light from the operation panel 24 of FIG. 1, processing the color print command (FIG. 6) sent from the host computer 1, and outputting the color print of characters. Has been done.

In step S21, the reference illumination light selection mode is selected from the switches on the operation panel 24, and step S22
Go to. In step S22, select the reference illumination light on the panel,
The reference illumination light selection parameter (FIG. 3) is read, and the process proceeds to step S23. In step S23, the host computer 1
Read the pattern information including the color print command (Fig. 6) and character information (character size etc.) sent from
Go to S24 and analyze the command.

In step S25, a pointer is set at the head of the color reproduction processing selection table, and the process proceeds to step S26.
In step S26, the information (here, a pointer to the color reproduction processing algorithm) corresponding to the illumination light selection parameter read from the operation of the operation panel 24 is taken out from the color reproduction processing selection table. The processing of steps S27 to S29 is exactly the same as the processing of S16 to S18 of FIG.

Here again, the color information immediately after step S27 is Y = 100.
When%, M = 50%, C = 25%, K = 0%, the character "A" is printed as shown in FIG. As explained above, the operation panel 2
It is possible to select a reference illumination light from 4, select a color reproduction processing algorithm corresponding to the reference illumination light, and print characters based on that.

In the above-described embodiment, an example of color reproduction processing when RGB luminance data is input has been described, but other color system data formats such as L * a * b *, L * are used. u * v
Even when inputting data such as * and YIQ, the method of color reproduction processing is only changed, and the present invention is applicable. Further, in the above-described embodiments, only the printing of characters is shown, but the present invention can be applied to the color printing of figures and raster images.

Further, in the above-mentioned embodiment, the reference illumination light is raised only for the one shown in FIG. 3, but needless to say, it is not limited to these. The printer of the output device may be a color laser printer, a color dot printer, a color inkjet printer, a color thermal transfer printer, a bubble jet printer, or the like. Further, the printer is not limited to a binary output printer, and may be a multi-value output printer.

The present invention may be applied to a system composed of a plurality of devices, an apparatus composed of a single device, or achieved by supplying a program to the system or the device. It goes without saying that the present invention can be applied to the case where

[0028]

As described above, according to the present invention,
The color data included in the print command is converted according to the illumination light when observing the output image, and it is converted under the illumination light source.
Match colorimetric color reproduction between input image and printout
Can not Rukoto. In addition, since the image processing device performs conversion according to the illumination light, the number of conversion means (conditions) provided in advance is limited, but as the illumination light that the conversion means (condition) corresponds to, the International Commission on Illumination does Standardized A, B and C
By including a light source, any one of the D55, D65, and D75 light sources, and any one of general fluorescent light sources such as a fluorescent lamp and an incandescent light bulb, it becomes possible to meet various uses of a wide range of users. Further, it is possible to improve the efficiency of the above-described conversion and dot development processing using color data.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a printing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of colorimetric color reproduction processing for performing processing so that color original image data becomes equal to an output result of a printing apparatus.

FIG. 3 is a diagram showing an example of a print command used when an illumination light serving as a reference for colorimetric color reproduction is selected and a color image is output by a printing apparatus.

FIG. 4 is a diagram showing a color reproduction processing selection table for selecting a color reproduction processing for each reference illumination light source described in FIG.

5 is a diagram showing an appearance of an operation panel 24 of FIG.

FIG. 6 is a diagram showing an example of a print command used when outputting characters with colors.

FIG. 7 is a flowchart illustrating print processing according to the present exemplary embodiment.

FIG. 8 is a flowchart illustrating print processing according to the present exemplary embodiment.

FIG. 9 is a diagram illustrating an example of a character print result.

FIG. 10 is a diagram illustrating general human perception.

FIG. 11 is a diagram illustrating the principle of general color tristimulus value calculation.

[Explanation of symbols]

1 host computer 2 Printer body 21 Interface 22 Color reproduction processing information storage 23 Color reproduction processing section 24 Control panel 25 data bus 26 Control unit 27 Command parser 28 Pattern development section 29 Output section

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Claims (2)

(57) [Claims] 1. An image processing apparatus for converting color data of a document image into color data according to any of a plurality of illumination lights, the illumination light being used for observing an output image together with a print command from the external device. Input means for inputting information indicating, a plurality of conversion means corresponding to each of the plurality of illumination light, based on the information indicating the input illumination light, selection means for selecting any of the conversion means, Processing means for converting the color data included in the print command into color data for performing colorimetric color reproduction processing according to illumination light when observing the output image, using the selected conversion means; A pattern developing means for performing dot development using color data obtained by the conversion process, wherein the plurality of illumination lights are standard light sources A, B and C standardized by the International Commission on Illumination. light An image processing apparatus comprising: a light source; and any one of D55, D65, and D75 light sources, and further including any light source of a fluorescent lamp and an incandescent lamp, which are general light sources. 2. An image processing method for converting color data of a document image into color data corresponding to any of a plurality of illumination lights, the illumination light being used for observing an output image together with a print command from the external device. Is input, and the conversion conditions corresponding to each of the plurality of illumination lights are retained, and based on the information indicating the input illumination light, one of the retained conversion conditions is selected, and the selected conversion condition is selected. Using, to convert the color data included in the print command into color data for performing colorimetric color reproduction processing according to illumination light when observing the output image, and converting the color data obtained by the conversion. Each step of performing dot development using, the plurality of illumination light, A, B and C light source, which is a standard light source standardized by the International Commission on Illumination, and any of D55, D65 and D75 light source. Is included, Furthermore, the image processing method is characterized by including any one of a general light source such as a fluorescent lamp and an incandescent lamp.