JP3134744B2 - Color management method and system in color image system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color management system for realizing color reproduction of a color image between different color input / output devices such as a scanner, a display, and a printer.
The present invention relates to a method and a system for realizing accurate color reproduction for each color image for a color image in an arbitrary format.

[0002]

2. Description of the Related Art Recently, with the rapid spread of color devices such as scanners, displays, and printers, attention has been paid to color management for realizing color reproduction of color images between color input / output devices having different color characteristics. As a system for achieving this, a color management system is being developed. Current color management systems obtain color characteristics of color input / output devices actually used, such as scanners, displays, and printers, by some method, and perform color correction processing, color conversion processing, and the like on color images.

As a simple example of color information required by a color management system, a case of a color image device based on the R (red), G (green), and B (blue) color system will be described. Device RG in color image equipment based on RGB color system
The color created by the B value and the XYZ tristimulus values (CI
The relationship of E (defined by the International Commission on Illumination) can be expressed by equation (1).

[0004]

(Equation 1)

The element a _ij of the 3 × 3 matrix in the equation (1) is
Given RGB phosphors and white XYZ tristimulus values,
Can be calculated. That is, if the RGB phosphors set in the color image device and the white XYZ tristimulus values are given, a color reproduction range that can be handled by the device can be obtained.

Further, as a characteristic that must be considered in a color image display device such as a display,
Has gamma characteristics. This is a light emission characteristic of a cathode ray tube when displaying a color image on a display. In general,
A color device whose gamma characteristic is represented by γ has a non-linear characteristic approximated by Expression (2) with respect to an input voltage E and an output luminance I.

[0007]

(Equation 2)

Here, A is a proportionality constant. NTSC
In the signal, the γ value is set to 2.2.

For a color image recording apparatus such as a printer that reproduces colors using multicolor inks such as C (cyan), M (magenta), Y (yellow), and K (black),
Since color reproduction is performed by subtractive color mixing or juxtaposition color mixing with multiple color inks, the color characteristics to be reproduced are complicated, and linearity using only color data obtained by color measurement of several color patches like a display The equations do not accurately represent the color gamut. Accurate color characteristics of color image recording equipment are based on the fact that hundreds to thousands of color patches are actually output and measured with a measuring device such as a spectrophotometer to measure the ink density and the XYZ tristimulus at that time. (Refer to the document “NewAlgorithm”).
m for UCR Using Direct Co
lorMapping ", M. Tsukuda et.
al. , SPIE, Vol. 2413 (1995)).

[0010] The format of a file for describing the color characteristics of a color image device as described above is being defined and standardized. International Color Con, founded by United States APPLE
Sortium has proposed a profile format for describing the color characteristics of a color imaging device so that it can be used on different platforms (Reference: International Color Con).
sortium Profile Format (ve
r3.0a), 1995). Here, for convenience of explanation, I
international Color Console
Tium is called ICC.

[0011] The ICC profile is configured in a tag format with three types of elements: a file header section, a tag table section, and a tag element data section. Here, an ICC profile describing the color characteristics of a color image device based on the RGB color system such as a scanner or a display is simply shown in FIG. In the ICC, as shown in FIG. 4, as a color space for connecting different device colors such as RGB and CMYK, a profile connection space (PCS) using an XYZ color system or an L ^* a ^* b ^* uniform color space is used. LUT which can describe the relationship between PCS and device color
Tag is prepared. By using this LUT,
A color image device of the CMYK color system having complicated color characteristics can also describe the color characteristics in the ICC profile. As described above, a profile for describing the color characteristics of a color image device such as a scanner, a display, and a printer can be created from the ICC profile.

If attention is paid to a color image file, BITMAP V is used in consideration of the color characteristics of image data.
ERSION 4.0 has been improved so that RGB phosphor, white XYZ values, and RGB gamma values can be described in the file header. Further, the ICC states that a tag of an ICC profile can be newly incorporated as it is for three types of image or document file formats of TIFF, PICT, and EPS in addition to the color image device.

[0013]

In order to realize color reproduction of a color image between different color image devices such as a scanner, a display, and a printer, a color management system having a highly accurate color correction or color conversion processing function. Even if the detailed color characteristic data of the color image device and the color image device are given, good color reproduction is realized unless the color information of the image data of the color image exchanged between the color image device and the computer is provided in some way. Can not.

TIFF, PICT, EPS or BITMAP Ver, which incorporates color information described in ICC.
Regarding the four types of image formats, the color information of each image can be obtained in a color image system that can handle them. However, the above four types of image formats have conventionally existed, and the current image reading unit of a color image application that can handle these image formats does not consider color information in the image format at all. That is, in order to obtain color information newly added to these four color image formats from an image file, there is a problem that a reading unit of image data in an existing color image application needs to be modified. Many image formats other than the above four types of image formats do not consider color information of image data at all. Therefore, since color information cannot be obtained from the image data, good color reproduction is difficult even if a high-precision color management system is used.

An object of the present invention is to enable a computer operating system or a color management system to automatically convert an arbitrary color image format to an arbitrary color image format without changing a portion for reading an image file of an existing color image system. It is an object of the present invention to provide a method and a system for acquiring color information of a color image in a format and implementing an accurate color management system for each color image.

[0016]

According to the present invention, there is provided a color management method comprising:
A color management system for realizing color reproduction of a color image between color image devices having different color reproduction characteristics of a color image input device, a color image display device, and a color image recording device; and a color image system using the color management system, An image color information file that describes information on the color and gamma correction of the color image for a color image of the format, and a device that describes the color characteristics of the color image input device, the color image display device, and the color image recording device There is a color information file, and the file name of the image color information file has a mechanism for searching by relating to the file name of the color image. The color image system reads the image data of the color image, and performs the color management. A system wherein the image color information file corresponding to the color image The color space obtained from the image color information file is read and stored in the color management system as the original color space of the color image. If the image color information file does not exist, the color space based on the system color space of the color management system is used. The color space obtained from the device color information file of the color image output device or the color image storage device that stores the color image in the color management system and outputs the color image is stored in the color management system as the target color space. A color correction process or a color conversion process from the original color space to the target color space, and performing the color correction process or the color conversion process on the image data of the color image.

The color management system of the present invention is a color management system for realizing color reproduction of a color image among color image devices having different color reproduction characteristics of a color image input device, a color image display device, and a color image recording device. An image color information file that describes information on the color and gamma correction of a color image in an arbitrary format; and device color information that defines color characteristics of the color image input device, the color image display device, and the color image recording device. A file, a mechanism that allows the file name of the image color information file to be searched for in association with the file name of the color image, an image color information file reading unit that reads the image color information file corresponding to the color image, An element for storing a color space obtained from an image color information file as an original color space of the color image A space memory, a system color space to be used as an original color space of the color image when the image color information file does not exist, and a device color information of the color image output device or the color image storage device for outputting the color image. A device color information file reading means for reading a file, a target color space memory for storing a color space obtained from the device color information file as a target color space, and a color from the original color space to the target color space. Color signal conversion means for constructing signal conversion processing, wherein the color signal of the color image is subjected to color correction processing or color conversion processing in the color signal conversion means.

According to a third aspect of the present invention, in the color management system according to the third aspect, when the color image system using the color management system stores a color image that has been subjected to color conversion processing by the color management system, An image color information file description unit for newly creating or updating the image color information file corresponding to the color image is provided.

The operation of the present invention will be described. The display device for the color image is a display having RGB three-color phosphors, the output device for the color image is a printer capable of printing with CMY three-color ink or CMYK four-color ink, and a computer connected to the display and the printer. A color management system for correcting or converting colors and a color image system using the color management system are incorporated. The color image system displays an original color image of the RGB color system on a display and outputs it to a printer. The case will be described.

First, information on color characteristics required to realize color reproduction of a color image of the RGB color system includes R, G,
These are XYZ tristimulus values of the B phosphor, XYZ tristimulus values of the reference white, and gamma correction data to be applied to each of R, G, and B. One file for writing these color information is created for each image. This is called an image color information file. FIG. 5 shows the contents of the image color information file. In the items in FIG. 5, the gamma curves of R, G, and B represent the gamma characteristics of the display for displaying this image as shown in FIG.
The gamma correction curve represents a curve applied to actual image data as shown in FIG. 6B, and is obtained by inversely converting the gamma curve. For the image color information file format, a tag format such as an ICC profile can be used in consideration of expandability.

One image color information file shown in FIG. 5 is created for all color images of an arbitrary format.
At this time, by naming the file name of the image color information file using the file name of the corresponding color image, the image color information file corresponding to the file of each color image can be selected. For example, in the case of the JPG format, the file name of an image widely used is AAAA. jp
g, the image file name is ".jp"
The extension "g" is often added. The same applies to other image formats. Now, AAAAA. jpg, the part of "AAAAA" is called an image identification part, and ".j
"pg" will be referred to as an image format extension. If the image identification unit with the extension ".ici" is to be an image color information file, the color image file name is image1.image. BI is bmp
The file name of the image color information file corresponding to the TMAP-format color image is image1.image. ici. By defining the naming rules for the image color information files in this manner, a mechanism for selecting an image color information file corresponding to each color image file can be constructed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.

A color management system for realizing color reproduction for each color image corresponding to an arbitrary image format according to a first embodiment of the present invention will be described with reference to FIG. First, the color management system 3, the color image system 2, the image memory 100, and the display image buffer 1 of the present invention.
01 and the device color information file selection means 5 are provided in a color image display device 2 of an RGB color system.
00, which is connected to the device color information file 50 as shown in FIG. 3 representing the color characteristics of the color image display device 200, a color image file 51 of an RGB color system of an arbitrary format, and color information of the color image file 51. It is assumed that the image color information file 52 shown in FIG.

Color image system 2 in computer 1
May be considered as a general application that handles color images. First, the image data reading means 4 in the color image system 2 reads the color image file 51,
The image data is recorded in the image memory 100.

The image color information reading means 8 in the color management system 3 includes an image color information file 5 corresponding to the color image file 51 read by the image data reading means 4.
2 is read and the obtained color information is stored in the original color space memory 102.
To record. The device color information file selection means 5 in the computer 1 displays all the device names of the color image display devices registered in the computer 1 and designates the device name of the color image display device 200 currently used to the user. The designated color image display device 200
Is passed to the device color information reading means 9 in the color management system 3. Device color information reading means 9
Reads the corresponding device color information file 50,
The obtained color information is recorded in the target color space memory 103.
Upon confirming that the color information has been set in the original color space memory 102 and the target color space memory 103, the flow control unit 10 creates a color correction process for creating a color correction process from the original color space to the target color space. An instruction to start creation is issued to the means 11. The color correction processing unit 11 computes the expression (1) obtained from the original color space and the following expression (3) obtained from the target color space.
Get one formula.

[0026]

(Equation 3)

Here, when the white color in the original color space and the target color space are the same, the R in the original color space is obtained from the equations (1) and (3).
The following relational expression (4) between GB and R'G'B 'of the target color space
Can be obtained.

[0028]

(Equation 4)

Now, a color correction formula (5) for realizing a color correction process from the original color space RGB to the target color space R'G'B 'by multiplying both sides by the inverse matrix of the 3 × 3 constant matrix on the left side.
Is obtained.

[0030]

(Equation 5)

The image processing means 7 in the color image system 2 is equipped with various processes such as image size change and image filters, and performs processes on image data in the image memory 100 in accordance with a user's instruction. The image display means 6 writes the image data in the image memory 100 to the display image buffer 101 in the computer 1.

The color correction processing means 12 in the color management system 3
Performs color correction processing on the image data written in the display image buffer 101 from the original color space created by the color correction processing creation means 11 to the target color space according to the color correction formula (5). . The color image display device 200 displays the image data on which the color correction processing has been performed.

A color management system for realizing color reproduction for each color image corresponding to an arbitrary image format according to a second embodiment of the present invention will be described with reference to FIG. The color management system 17 of the present invention exists in a computer system 16 to which a color image display device 200 of RGB color system and a color image recording device 201 of CMY (K) color system are connected. Color display image display device 200 and color image recording device 2
FIG. 5 shows a device color information file database 53 storing a device color information file according to a format such as an ICC profile showing the color characteristics of No. 01 and a color image file 51 of an arbitrary format and color information of the color image file 51. It is assumed that the image color information file 52 as shown in FIG. Further, the computer system 16 has a color image processing application 150, an operating system 151, and a device driver 152.

The color image file 51 read by the color image processing application 150 is displayed on the color image display device 200 or the color image recording device 20.
1, the image data signal 54 of the color image file 51 passes through the operating system 151 and the device driver 152, and is passed to each device to be subjected to color correction processing or color conversion processing.

First, in the color management system 17, an image color information file 52 corresponding to the color image file 51 read by the color image processing application 150.
Is read by the image color information reading means 8 and the obtained color information is recorded in the original color space memory 102 as the original color space. Next, the device color information reading means 9 reads the operating system 151 or the device driver 1
The color information of the color image display device 200 and the color image recording device 201 is obtained from the device color information file database 53 in response to the instruction from the device 52, and the color information of the color image display device 200 is recorded in the display color space memory 104. And
The color information of the color image recording apparatus 201 is recorded in the recording color space memory 105. Then, the color image display color correction processing means 13 constructs a color correction process according to the formula (5) from the original color space to the display color space when displaying the color image file 51 on the color image display device 200. The color conversion processing unit 14 constructs a color conversion process from the original color space or the display color space to the recording color space when outputting the color image file 51 to the color image recording device 201. Here, the color conversion processing from the original color space or the display color space to the recording color space can be constructed according to the automatic color gamut conversion method described in JP-A-6-339016, but other methods can also be used. The color space selecting means 15 stores the original color space memory 1
02 or the color information recorded in the display color space memory 104 is selected and input to the color conversion processing means 14. here,
Which color information should be selected depends on the color image file 5
1 outputs the color correction image data signal 55 subjected to the color correction processing by the color image display color correction processing means 13, selects the color information from the display color space memory 104 and performs the color correction processing of the color image file 51. When the image data signal 54 to which the color data is not applied is output, the color information from the original color space memory 102 is selected.

The device driver 152 outputs the image data signal 54 that has not been subjected to color correction processing or color conversion processing.
Is displayed on the color image display device 200, the color corrected image data signal 55 that has been subjected to the color correction processing by the color image display
Send to 00. When outputting the image data signal 54 or the color correction image data signal 55 to the color image recording device 202, the device driver 152 converts the color conversion image data signal 56 that has been subjected to the color conversion processing by the color conversion The image is sent to the color image recording device 201.

Finally, when the color image processing application 150 saves a color image file, the color management system 17 updates or newly creates an image color information file corresponding to the color image file. The image color information file description means 19 in the color management system 17
Original color space memory 102, display color space memory 104, recording color space 105
And updates the contents of the image color information file 52. Here, if the image color information file does not originally exist, the image color information file 52 is newly created.

[0038]

According to the method and system of the present invention, color management corresponding to all image formats can be realized.
Since a color information file is created for each color image, there is no need to change the existing image format. Further, the image load / save utility of each image format that is currently widely used and the existing color image application are changed. Without this, accurate color management can be realized for all color images.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a color management system.

FIG. 2 is a block diagram illustrating an embodiment of a color management system.

FIG. 3 is an explanatory diagram showing an ICC profile.

FIG. 4 is an explanatory diagram showing a profile connection space (PCS) that connects an RGB space and a CMYK space.

FIG. 5 is an explanatory diagram showing an image color information file.

FIG. 6A is an explanatory diagram showing a gamma characteristic curve of a color image display device of an RGB color system. FIG. 4B is an explanatory diagram illustrating a gamma correction curve applied to a color image of the RGB color system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Computer 2 Color image system 3 Color management system 4 Image data reading means 5 Device color information file selection means 6 Image display means 7 Image processing means 8 Image color information reading means 9 Device color information reading means 10 Flow control means 11 Color correction processing Creation means 12 Color correction processing means 13 Color image display color correction processing means 14 Color conversion processing means 15 Color space selection means 16 Computer system 17 Color management system 18 System color space 19 Image color information file description means 50 Device color information file 51 Color Image file 52 Image color information file 53 Device color information file database 54 Image data signal 55 Color correction image data signal 56 Color conversion image data signal 100 Image memory 101 Display image buffer 102 Original color sky Memory 103 target color space memory 104 display color space memory 105 recording color space memory 150 color image processing application 151 operating system 152 device driver 200 color image display apparatus 201 a color image recording apparatus

Claims (3)

(57) [Claims] 1. A color management system for realizing color reproduction of a color image between color image input devices, color image display devices, and color image recording devices having different color reproduction characteristics, and a color management system using the color management system. In an image system, an image color information file that describes information on the color and gamma correction of the color image for a color image of an arbitrary format, and color characteristics of the color image input device, the color image display device, and the color image recording device There is a device color information file in which is described, and has a mechanism that allows the file name of the image color information file to be searched for in association with the file name of the color image, and the color image system stores image data of the color image. Reading the color management system, the image color corresponding to the color image Information file, and the color space obtained from the image color information file is stored in the color management system as the original color space of the color image. If the image color information file does not exist, the system colors of the color management system are stored. A color management system stores a color space as an original color space in a color management system, and a color space obtained from the device color information file of the color image output device or the color image storage device that outputs the color image, as a target color space. Storing a color correction process or a color conversion process from the original color space to the target color space, and performing the color correction process or the color conversion process on the image data of the color image. Color management method. 2. A color management system for realizing color reproduction of a color image between color image input devices, color image display devices, and color image recording devices having different color reproduction characteristics. An image color information file describing information on color and gamma correction of a color image; a device color information file defining color characteristics of the color image input device, the color image display device and the color image recording device; A file name of an information file that can be searched by relating to a file name of the color image; image color information file reading means for reading the image color information file corresponding to the color image; An original color space memory for storing the obtained color space as an original color space of the color image; If there is no information file, a system color space used as an original color space of the color image, and a device color for reading the device color information file of the color image output device or the color image storage device for outputting the color image Information file reading means, a target color space memory for storing a color space obtained from the device color information file as a target color space, and a color for constructing a color signal conversion process from the original color space to the target color space. A color management system comprising: signal conversion means; and performing color correction processing or color conversion processing in the color signal conversion means on color signals of the color image. 3. The color management system according to claim 2 , wherein
An image color information file for newly creating or updating an image color information file corresponding to the color image when a color image system using the color management system saves a color image subjected to color conversion processing by the color management system; A color management system comprising a description unit.