Talking about Color Management Technology (2)

Third, several mainstream color management system

1. Adobe's Photoshop color management system. As Adobe's most famous image processing software, Photoshop has an irreplaceable position in image processing. At the same time, Adobe also strives to develop Photoshop into a complete color management system. The color management features of Photoshop software are controlled by the "Monitor Setup" - Display Settings, "Printing Inks Setup" - Printing Ink Settings, and "Separation Setup" - Separation Settings.

In order to make the color the user sees on the screen be as close as possible to the color of the output proofs, the user's system must first be calibrated. The accurate color workflow must begin with an accurate display correction and correct display settings. Monitor Setup includes monitor correction and monitor setup. In the display, the display type, phosphor powder, color temperature and other parameters are correctly selected. In this way, when the image is converted to the color mode, the correct color conversion can be performed according to the setting of the above parameters.

The basic purpose of the printing ink setup is to provide Photoshop with information on the inks, papers, and printing machinery used in the final printing. Different papers have different ink absorption and dot gain, and different inks have different color rendering properties. The dot gain rates of different printing methods are also different. So you need to set these parameters in Photoshop Inks Setup. After the basic information is obtained from the RGB image data and the display data obtained in the Monitor Setup, the color mode conversion is performed according to the characteristics of the final printing conditions.

The most important item in the separation is the determination of the black version. In theory, multiple CMYK values ​​can be generated from one RGB value separation, and the final printing effect should be the same. However, due to the ink receiving capacity of different printing papers and the characteristics of different printing machines, the theoretical possibility may not be realized. Therefore, it is necessary to set the percentage of printing separation, the amount of black printing, and the percentage of printing total dots.

2. Apple's ColorSync color management system. ColorSync is a color management system released by Apple. It adopts the ICC standard and uses the Lab color space as the standard reference space. It is a system-level color management software applied under the Mac operating system. It is an open color management system, users can use ColorSync's Plug-in module to perform color conversion between different color management systems. The ColorSync system consists of three components, an ICC standard color profile, a color matching method (CMM), and an application software interface (API).

The device description file defines the color characteristic information of the device, and through this information, the color range that can be displayed, captured and reproduced by the used device can be obtained. When using ColorSync to create a file, a Profiles file is stored in the file so that when processing images with the ColorSync description file on other devices, ColorSync compares the device characteristics of the created image with the characteristics of the display. Color space matching operations to get the best color effect.

The color matching method is the core part of ColorSync. It realizes the conversion of different color spaces. More importantly, ColorSync's color conversion mode adopts Linotype HELL's high-quality color matching technology. Users can use a better color gamut compression method to process color. Outside the domain.

Because various application softwares have different color performances, the same image color will have different appearance from image scanning to final copying. In order to be able to grasp the quasi-color at any time during the work, it is necessary to apply these application software to perform effective color matching. The color matching method can be used for color matching through the ColorSync application software to achieve a consistent purpose.

3. Kodak's color management system. Kodak is a color management system that supports both PC and Mac platforms. Unlike Apple's ColorSync and Adobe's Photoshop, Kodak's color management system tends to use color management in a modular way, and it provides several localized modules that can be combined to form a complete color management. system. And it also has color management capabilities for the Photo CD image input process.

Kodak color management system generally includes four modules: KPCMS, DCP, PICC and PCS100. They can be used separately or combined into a complete color management system.

The KPCMS module (Kodak Precision Color Management System) provides a sufficient number of device description files that conform to the ICC standard format. Its input devices include RGB image sources and CMYK image sources, and its output devices include hitting machines and proofers. However, since it cannot edit the custom device description file itself, it has great limitations.

DCP module (device color description file startup software package) is a software package that provides display and output color correction specifically for Photo CD images. When opening a Photo CD image, the user is required to select two device description files. The input device description file is a The description file of the Photo CD device. The output device description file may be a display description file or a color proofer description file. The PICC module (Precision Input Color Characterization) provides a scanner utility calibration routine that enhances the DCP functionality.

For advanced image processing and scanning applications, Kodak provides the PCS100 module to speed up the color conversion process of Photo CD images. With the PCS100 module, direct links between various devices can be generated to skip the intermediate conversion process of the CIE color space, saving time for each conversion and color loss during conversion.

Fourth, how to choose the right color management system

At present, many companies at home and abroad have developed color management systems. Although the International Color Organization (ICC) formulates the standard ICC Profile describing the color expression of devices, the color management systems developed by companies under this standard have the ability to manage the color of devices. Different from each other, the color space conversion between devices should be based on their own needs to choose the most suitable color management system, the following factors should be considered when choosing:

1. The color management system on the market can hardly provide complete color management for the entire process of copying. Each system has its own color management part. Therefore, the user must determine which devices need to obtain a consistent color in order to select the right one. system.

2. Determine the self-describing file in the color management system, and whether it supports the establishment of description files in the open system; if it is a closed system, the description file must be established by the factory, so you need to determine whether it can bear the cost of establishing a description file .

3. Comparing various color management systems and comparing the specific conditions of the users, it is possible to compare various performances such as system reliability, device support capability, scalability, compatibility, and ease of use.

4. Test the selected color management system and test the system with the same color manuscript. Observe which system can achieve the best results with the manuscript under the specific operating environment.