JPH0462684A - Color picture processor - Google Patents

Abstract

PURPOSE:To simply and precisely obtain required color by assigning the color data of an XYZ color specification system by an input device and executing transformation between the color data of the XYZ color specification system and the color data of the RGB color specification system of an inout/output device. CONSTITUTION:An operator executes the synthesizing of a picture, color tone changing and print distributing interactively by using a keyboard 47 and a pointing device 48 by watching a picture displayed on a display 43 and prepares the picture that he intends. Then, the color data of a Munsell color specification system are inputted to a Mumsell XYZ transforming circuit 425. On interactive picture processing, the efficiency of operation is improved by comparing with color assignment by relative RGB 3 bytes. Picture data are inputted to a printer correcting circuit, are transformed into the data of a printer RGB color specification system by interpolating a three-dimensional lookup table and printer- outputted. Accordingly, the operator can obtain the hard copy of the picture as he intends.

Description

[Detailed description of the invention] [Industrial application field]

The present invention provides color image processing that corrects color differences due to the characteristics of input/output equipment, allows accurate input and output of colors, and allows an operator to intuitively and easily specify desired colors. Regarding equipment.

[Conventional technology]

In computer graphics, when expressing the color of an image numerically, a method is generally used in which the three primary colors are red (R), green (G), and blue (B), and the color is expressed by additive color mixture of the three primary colors. For each primary color, 8 bits and a numerical value from 0 to 255 are given as color intensity, and approximately 16.7 million colors are expressed in 3 bytes by a combination of these three numerical values. This is because: 1) Graphic displays, which are currently standard output devices, reproduce colors by additive color mixing of three primary colors, and 2) The number of colors is sufficient for the human eye's discernment ability. The following points are true: ■ Calculation is easy because one byte, which is the basic unit of computer calculations, is used to represent the intensity of each primary color. ■ Values are applied only to colors that can be reproduced. Therefore, this method has become popular because the color space is closed, there is no need to consider colors that cannot be reproduced, and it is easy to handle. This method can be said to be the most effective method from the point of view of controlling various input/output devices. Image processing by this method will be explained using the flowchart of FIG. First, an original image is input using an image input device such as a scanner and a color camera (S11). The RGB data output from the human-powered image device is input directly to the processor and stored in the processor's internal memory. At that time, processing such as gamma correction and edge enhancement may be performed within the input device to improve image quality. The RGB data on the image memory inside the processor is sent as is to the graphic display, and the image is displayed on the display. The operator interactively processes the image using a keyboard or pointing device while checking the image displayed on the screen (S12). When the operator specifies colors for the RGB data of this image, It is common to specify each byte of RGB. The final RGB data that has undergone image processing is converted into C (soane), M (magenta), and Y (yellow) data using the following (Equation 1), and is further subjected to image processing such as dithering and gamma correction. It is sent to the printer, which is an output device. Then, a hard copy is output by the printer (S13
). Based on the sample thus output, the operator checks whether the color is the one he or she desires (S14). If it is determined that the sample does not have the color you desire, perform color correction (S12) and output (S13) on the image data on the processor until the color you desire is achieved.
) was repeated.

[Problem to be solved by the invention]

In this way, in the conventional color image processing method described above, RG
Processing is done consistently using color data from the B color system, and the color characteristics of input and output devices differ, so you have to look at the output results to determine what color the specified color will actually be. As explained above, if you look at the output image and perform extremely unstable and inefficient color correction that relies on the color sense of the operator's eyes, The problem was that it didn't. In addition, color designers and engineers who are operators at a practical level have traditionally used the Munsell color system (
JIS X8721) is often used. Naturally, there has been a strong need for image processing devices to use the Munsell color system instead of specifying relative colors for each byte of RGB. However, a practical image processing device using the Munsell color system has not been developed, and there is a problem in that colors must be specified using the RGB color system, which is difficult to understand intuitively. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color image processing apparatus that can easily and accurately obtain a color image desired by an operator by correcting differences in color due to characteristics of input/output equipment. Another object of the present invention is to provide a color image processing device that is capable of specifying colors using the Munsell color system, and is therefore intuitively easy to understand, and that allows color specification to be performed simply and accurately. .

[Means to solve the problem]

In order to achieve the above object, the present invention connects relative color data in the RGB color system used for computer graphics and physical color data in the It is characterized by the ability to obtain physically accurate colors without relying on characteristics or the senses of the operator. Furthermore, the present invention is characterized in that it is possible to specify colors in the Munsell color system by converting color data in the Munsell color system to color data in the XYZ color system. That is, the first invention provides a color image processing device that includes an input device, an output device, and a control unit and processes images and changes colors, including a memory that stores color data in an XYZ color system (CIE); The input device includes a first conversion means for converting between the color data of the X, YZ color system in the memory and the color data of the RGB color system of the input device or the output device, and the input device The feature is that it is possible to specify and input color data directly or indirectly. Further, in a second aspect of the invention, the input device is configured to receive color data in the Munsell color system, and to store color data in the Munsell color system in the memory. It is characterized by comprising a second conversion means for converting into data. Further, a third invention provides that the input device and the output device include:
Multiple different R's that have been corrected according to their respective color characteristics
The color data of the GB color system is input and output, and the color data of the plurality of RGB color systems mentioned above and the XY
The present invention is characterized in that it includes a plurality of the first conversion means each converting between the color data of the Z color system and the color data of the Z color system. Further, a fourth invention is characterized in that the first conversion means includes a three-dimensional lookup table that associates RGB color data with XYZ color data. FIG. 1 is a block diagram showing the relationship between each color system used in the present invention and each conversion. The present invention uses XY as a standard color system.
It has a Z color system (21). When color data is stored in an external storage device, it is stored as numerical values in the XYZ color system (21). Here, RGB is corrected according to the color characteristics specific to each input/output device, such as displays, printers, and scanners.
Each color space is a display RGB color system (22),
These will be referred to as a printer RGB color system (23) and a scanner RGB color system (24). The color data specified in the XYZ color system (21) is converted by each first conversion means for each input/output device such as a printer, scanner, or display, and then converted into a table corresponding to each input/output device. Color RGB data is input and output. In addition, the Munsell color system (25) is a perceptually uniform color system, so it has been often used by designers who deal with colors, and is the most suitable color system for operators to specify colors. be. The color data in the Munsell color system (25) is converted into color data in the XYZ color system (21) by the second conversion means. Display RGB color system (22) to XYZ color system (
21) will be explained. Since the display RGB color system (22) is not linear with respect to brightness, it is converted into a numerical value linear with respect to brightness by gamma correction (Equation 2). In (Formula 2), rz L b is the brightness of each phosphor of R and GSB, and R, G, and B are the display RGB color system (22)
The RGB values, HSgaSba, are each 2.0-
It is a constant of 3.0. The values of ra, ga, and ba can be derived by measuring the brightness r, g, and b of each color on the display and from the brightness r, g, and b and the values of each RGB in the RGB color system. Actually, in order to perform conversion at a higher speed, the relative brightness r, g, and b are set with the maximum brightness that can be output on the display as 255, and the values of relative brightness r, g, and b are set from 0 to 255. About the corresponding display RGB
A look-up table of color system values R, G, and H is created and conversion is performed by referring to it. Next, this is linearly converted to the XYZ color system. This is shown in (Equation 3). (Formula 4) is an inverse transformation of (Formula 3). Next, this is subjected to gamma correction (Equation 5) and output to the display. (Xr, Yr, Zr), (Xg, Yg, Zg), (Xb
, Yb, Zb) are the XYZ fluorescent colors of each RGB phosphor.
These are the XYZ values of the color system. Further, t is an arbitrary constant, which is necessary for pseudo-expressing the object color on the display, which is originally the color of the light source. From the XYZ color system (21) to the display RGB color system (
22) is just the opposite of these. X
The color (X, Y. Z) expressed by the YZ color system is subjected to a -order transformation and converted to a linear rgb color space (Equation 4). From the XYZ color system (21) to the printer RGB color system (23
). Conversion from the XYZ color system (21) to the printer RGB color system (23) is performed by interpolation using a three-dimensional lookup table of the present invention created based on measurement data. A three-dimensional lookup table is a color space based on the printer RGB color system shown in Figure 2.
Print out the color of each coordinate point evenly divided for each GB coordinate axis, measure the sample using the chromaticity system, and
The XYZ values are then associated with the RGB values. By searching and interpolating this three-dimensional lookup table, it is possible to accurately convert the XYZ values to the printer RGB color system. Next, a method of converting from the scanner RGB color system (24) to the XYZ color system (21) will be explained. The RGB values read by the scanner undergo look-up table conversion for each RGB value, and then matrix conversion to produce XYZ values. The matrix conversion formula is shown in (Formula 6). In (Formula 7), (Xc Yc Zc), (Xm
Ym Zm) and (Zy Yy Zy) are the measured values of cyan, magenta, and yellow color chips in the XYZ color system, respectively, and (Re Gc Be) and (Rm Gm Bm)
, (Ry GyBy) are RGB values when cyan, magenta, and yellow color patches are read by a scanner. When this is transformed, it becomes (Formula S), and the matrix M can be obtained. M is a 3×3 matrix. To find M, use three brightly colored color charts that are far apart from each other, such as cyan (C).
), magenta (M), and yellow (Y) with a scanner and check their RGB values. The relationship between the XYZ values of these color patches and the scanner RGB values can be expressed by (Equation 7). ...(Equation 8) Next, several types of achromatic color patches with multi-level brightness from white to black are read in with a scanner, and the XYZ values are measured by the scanner's RGB values and the base paper color chart with a chromaticity meter. The RGB values transformed by the inverse transformation of (Equation 6) are compared, and the R obtained by the scanner is
A lookup table for converting GB values to RGB values obtained using a chromaticity meter is created. Next, from the XYZ color system (21) to the Munsell color system (25
) conversion and inverse conversion will be explained. To convert from the XYZ color system to the Munsell color system, solve the Munsell brightness function (Equation 9) below using Newton's method, and calculate the brightness ■
is determined, and further interpolated using a lookup table CJTS8727 Appendix Table 1) on the hue H-saturation C plane. Y = 1.2219V -0,23111V' +
0.23951V3-0.021009V' 〒0.0
O08404V5... (Formula 9) For conversion from the Munsell color system to the XYZ color system, Y is determined using the Munsell lightness function (Formula 9). Furthermore, the hue H-
In the chroma C plane, search from the lookup table,
Find by interpolation.

[Effect]

According to the first invention, the color data of the XYZ color system is directly or indirectly specified by the input device and stored in the memory. Here, "direct" refers to inputting the color data itself in the XYZ color system, and "indirect" means, for example, inputting the color data specified in the XYZ color system via the color data in the Munsell color system. It means to do something. The color data in the XYZ color system stored in the memory is converted into color data in the RGB color system of the output device by the first conversion means, and the color data in the RGB color system is input to the output device. Further, the color data in the RGB color system of an input device such as a scanner is converted into color data in the XYZ color system by the first conversion means, and the converted color data is stored in the memory. In this way, according to the first invention, the RGB of the input/output device
Since color data in the color system is converted into color data in the XYZ color system by the first conversion means, differences in color due to the characteristics of each input/output device can be corrected, and colors can be understood as physical objects. . Therefore, in the color image processing device of the first aspect of the invention, the operator does not need to consider the difference in color due to the color characteristics of the input/output device, and the desired color can be easily and accurately obtained. Further, according to the second invention, the input device can input color data in the Munsell color system. The color data of the Munsell color system input by the input device is the second
The conversion means converts the data into color data of the XYZ color system and stores it in the memory. Therefore, it becomes possible to specify a color in the Munsell color system, which is a perceptually uniform object color. According to the third invention, the conversion between the color data of the plurality of RGB color systems and the color data of the XYZ color system according to the color characteristics of the plurality of input/output devices is performed by the plurality of first conversion means. are carried out respectively. Therefore, even if a plurality of input/output devices have different color characteristics, colors can be specified accurately. Further, according to the fourth invention, since the first conversion means includes a three-dimensional lookup table, accurate conversion can be performed.

【Example】

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments. The configuration of the device is shown in Figure 3. A graphic display (43) is connected to the control unit (4I) via a correction circuit (42).
, printer (44), and scanner (45) are connected. Furthermore, the control unit (41) includes a hard disk (46) which is a storage device for storing image data, and a keychain (47) used by the operator to interactively specify colors in the Munsell color system. ),pointing device(
48) is connected. FIG. 4 shows the inside of the correction circuit (42). Inside the correction circuit (42), there is an XYZ color system memory (421).
On the other hand, from the XYZ color system to Display R
A display correction circuit (422) that converts to and from the GB color system, a printer correction circuit (423) that converts from the XYZ color system to the printer RGB color system, and a scanner RG.
A scanner correction circuit (424) for converting from the B color system to the XYZ color system is connected, and exchanges color data with an input/output device. These display correction circuit (422), printer correction circuit (423), and scanner correction circuit (424) are examples of the first conversion means. In addition, a Munsell/XYZ conversion circuit (
425) is connected to the xyz color system memory (42I) and also to the control unit (41). A case will be described in which a printing plate for printing or dyeing is created using this color image processing device. The flowchart is shown in FIG. Scanner (45
). The loaded original image is scanned RGB
This is color system data. This is the scanner correction circuit (4
24). In the scanner correction circuit (424), each of the RGB data is converted using a lookup table, and then converted to data in the XYZ color system through the matrix operation (26), and stored in the xyz color system memory (421). (S61). Furthermore, this XYZ color system data is input to the display correction circuit (422). The display correction circuit (422) converts the data into the display RGB color system by matrix conversion (Equation 4) and gamma correction for each RGB (Equation 5). This display RG
By inputting the data of the B color system to the display (43), an image having the same chromaticity as the original image is displayed on the display (43). The operator uses the display (43
), use the keyboard (47) and pointing device (48) to interactively
The images are combined, the color tone is changed, and the image is separated to create the image that the operator intended (S62). At this time, the operator or keyboard (47) or pointing device (48)
The color data of the Munsell color system specified by is Munsell
It is input to the YZ conversion circuit (425). Munsell XY
In the Z conversion circuit (425), Y is determined by (Equation 9), and X and Z are determined by searching the lookup table (JI98727 Appendix 1) and interpolating. In such interactive image processing, a physically and visually uniform color space such as the Munsell color system improves the efficiency of operation compared to the conventional color specification using relative RGB 3 bytes. Great effect. The image data thus created is input to the printer correction circuit (423). In the printer correction circuit (423), by interpolating the three-dimensional lookup table, the data is converted into printer RGB color system data and output to the printer (S63). Therefore, the printed image is not displayed on the display. It has the same chromaticity as the original image, allowing the operator to obtain a hard copy of the image exactly as he or she intended. In the above embodiment, color data in the Munsell color system is input from the keyboard (47), or color data in the XYZ color system may be input.

【Effect of the invention】

As is clear from the above, according to the first invention, color data in the XYZ color system is specified directly or indirectly by a human-powered device, the color data in the XYZ color system is stored in a memory, and the color data in the XYZ color system is stored in a memory. Color data of XYZ color system and RG of input/output device
Since the first conversion means converts the color data to and from the B color system, the operator does not have to think about the difference in color due to the color characteristics of the input/output device, and can easily and accurately convert the color data to the desired color data. colors can be obtained. According to the second invention, color data in the Munsell color system is inputted by the input device, and the second conversion means converts the color data in the Munsell color system and the color data in the XYZ color system. Since it is converted, it is easy to understand and use the Munsell color system, which is a visually uniform object color.
In addition, colors can be specified accurately. Further, according to the third aspect of the invention, each first conversion means performs conversion between color data in different RGB color systems and color data in an XYZ color system of the plurality of input/output devices. Therefore, colors can be input and output easily and accurately without considering differences in color characteristics of a plurality of input/output devices. Further, according to the fourth invention, since the first conversion means includes a three-dimensional lookup table, it is possible to accurately process data and to have a general-purpose configuration that does not depend on the color characteristics of hardware.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the relationship between each color system, and Figure 2 is a block diagram showing the relationship between each color system.
FIG. 3 is a block diagram of a color image processing apparatus according to an embodiment of the present invention, FIG. 4 is a block diagram of a correction circuit, and FIG. 5 is a flowchart of image processing according to the present invention. , FIG. 6 is a flowchart of conventional image processing. 41... Control unit, 42... Correction circuit, 43 - Display, 44... Printer, 45... Scanner,
46... Hard disk, 47. Keychain, 48
- Pointing device, 421...XYZ color system memory 422... Display correction circuit, 423... Printer correction circuit, 424... Scanner correction circuit, 425... Munsell-XYZ conversion circuit.

Claims (4)

[Claims] (1) In a color image processing device that is equipped with an input device, an output device, and a control unit and processes images and changes colors, there is a memory that stores color data in the XYZ color system (CIE), and an XYZ table in the memory. The input device includes a first conversion means for converting between the color data of the color system and the color data of the RGB color system of an input device or an output device, and the input device converts the color data of the XYZ color system directly or A color image processing device characterized in that indirect identification and input is possible. (2) The color image processing device according to claim 1, wherein the input device receives color data in the Munsell color system, and stores the color data in the Munsell color system in the memory. A color image processing device comprising a second conversion means for converting into color data of an XYZ color system. (3) The color image processing device according to claim 1 or 2, wherein the input device and the output device each input color data of a plurality of different RGB color systems that have been corrected according to their respective color characteristics. The plurality of first color data are outputted, and each of the plurality of first color data converts between the color data of the plurality of different RGB color systems and the color data of the XYZ color system.
A color image processing device comprising a conversion means. (4) The color image processing device according to any one of claims 1 to 3, wherein the first conversion means includes a three-dimensional lookup table that associates RGB color data with XY2 color data. Characteristic color image processing device.