How to ensure the consistency of Rigid Cardboard Cigar Paper Boxes color transfer between devices

How to ensure the consistency of Rigid Cardboard Cigar Paper Boxes color transfer between devices

The printing process, in fact, is the process of transferring the image information of the original manuscript in various printing input and output devices. How to achieve the maximum compatibility and consistency of the information from the input and output of the original manuscript information between the printing input and output devices, that is, to ensure that the information transmission is as accurate as possible and achieve the best copy faithful to the original.

In order to copy the printed manuscript, the color separation must be carried out first, and the current color separation technology has developed from the traditional photographic color separation and electronic color separation to the current desktop publishing system.

The color printing and printing process of desktop publishing system is essentially the process of restoring the color through the conversion and transmission of the color information of the original text and text in various devices and different color Spaces. The reproduction of color depends on the device that produces it, but in the integrated environment of desktop publishing system, because each device has different color gamut and color characteristics, it is particularly difficult to accurately control and transmit the graphic color information in the desktop publishing system. To achieve this goal, effective color management independent of devices must be implemented in the desktop publishing system to ensure the compatibility of signal input and output between devices, and to reduce and compensate the impact of differences in device color characteristics and color patterns on color information. Thus, the color distortion of the graphic color data information is minimized when it is converted and transmitted between different color Spaces and devices with different color characteristics, so as to ensure that the effect of the color of the same picture from input to display to output matches as much as possible, so that the reproduction and the original color achieve harmony.

To do a good job of color management in desktop publishing system, the key is to deal with the unified color space, device system characterization and color conversion.

First, to ensure the unity of the color mode and its color space

In desktop publishing system, color reproduction usually involves three color modes: RGB, CMYK and Lab. RGB is the color mode of color light. It consists of three channels: red, green and blue. In this mode, the other colors are formed by superimposing the three primary colors. Since all three colors have 256 brightness levels, a three-color overlay can create 16.7 million colors. In desktop publishing systems, input and display devices such as scanners, digital cameras, and monitors rely on this mode to express colors. When sunlight hits an object, the object absorbs some of the light and reflects other light. The reflected light is the color of the object we see, which is a subtractive color pattern. Depending on this subtractive color mode, the CMYK mode suitable for printing and printing has evolved. Since it is difficult to superimpose the real black ink of these three colors in practice, black is introduced to strengthen the dark tone and deepen the dark color when printing and printing. Although this color mode defines much less color than the RGB color definition, that is, the color space is much smaller, but the desktop color prepress system in the phototypesetter, printer, proof press and other output devices are dependent on this mode to reproduce color. Lab mode is a color mode developed by the CIE (International Commission on Lighting). Any color in nature can be expressed in the Lab space, and its color space is larger than the RGB space. In addition, this mode is a digital way to describe human visual perception, independent of the device, so it makes up for the RGB and CMYK mode must rely on the color characteristics of the device.

Because the color space of Lab is larger than that of RGB mode and CMYK mode. This means that the color information that RGB and CMYK can describe can be reflected in the Lab space. Therefore, in the color management of the desktop publishing system, if all the color conversion and color correction operations are completed based on the Lab space, the color data will not be converted from the Lab space to RGB or CMYK space due to insufficient data. It can be seen that in color management, in order to unify the color space, it should be based on this Lab mode, which is independent of the device and has a large color space.

To sum up, in the process of prepress production, we should store the color information obtained by scanners and digital cameras working in RGB mode in Lab mode, and do color editing and correction in Lab color space, and then convert it to CMYK space when printing or printing. This is the best solution for color processing. Because printers and phototypesetters express color in CMYK mode, many operators are also used to editing and correcting colors in CMYK space in actual operation. This practice is not advisable because it causes color loss, and operating in CMYK also slows down the computation from the computer.

Second, to describe the color characteristics of the equipment and its system characteristics

Desktop publishing system is an open system, its each device can only reproduce or display a specific range of colors, like scanners, monitors, digital cameras generally use RGB space to express colors; Color printers, proof presses, phototypesetters generally use CMYK space to express color. In addition, because the color characteristics of different devices will be different, as well as the impact of the use of the environment and equipment status, even if it is the same device, its color characteristics are relatively unstable. The result of color reproduction depends on the device that produces it, and without understanding the differences between each device, the conversion and transmission of color information will inevitably be greatly affected, so that the expected color can not be obtained. The process of device system characterization is essentially the formation of the color characteristic description file of different devices in the desktop publishing system, and the use of the file to coordinate the whole desktop publishing system. In order to ensure the stability, reliability and continuity of color information in the transmission process, the input, display and output devices must be systematically characterized to make the equipment in a standard state. Color management is to detect the device through a series of color measurement tools, and draw the chroma or gamut characteristic curve of the device, and then make the color description file of the device against the color model independent of the device. These color description files are the credentials for the conversion between the color space of the respective device and the standard, device-independent color space, ensuring the stability of the color characteristics of the device itself. In order to enable the sharing of color information in multi-device environments, ICC has developed a cross-platform and system ICC standard. In this standard, they specify the format and type of the device color description file, while defining a virtual device-independent color space. Then according to this format, the original device color space is converted to the virtual space, and then the virtual space is converted to the target device color space, so as to ensure the correct transmission of color information in the input and output devices.

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Third, pay attention to the choice of color space conversion and its common methods

Color space conversion is the conversion of color image data between different devices using color space independent of equipment as a bridge. The conversion of color space involves two problems. One is the choice of color pattern. In the process of color management, the description of color should be independent of equipment. The Lab color space model defined in CIE is based on a large number of color vision measurements, which is independent of equipment, so it is widely used in color management systems. The second is the allusion relationship of color space transformation. Because of the disunity of many color Spaces, it will inevitably involve the problem of color gamut compression or choice. It is the requirement and goal of color conversion to make the color displayed on the display screen and the color output of the color printer and phototypesetter as close as possible to the original manuscript. However, because the CMYK space of the output device is smaller than the RGB space of the input and display devices such as scanners and monitors, in the color space conversion, it is necessary to establish the insinuation relationship between the display and the scanner that cannot be covered by the ink, in order to ensure that the ink as large as possible color gamut reproduction space. According to the requirements of color production and restoration, color conversion is often used in the following ways, each way is suitable for different objects.

1. Visual perception shift. In the process of image reproduction, the relative relationship of the original color is maintained, that is, according to the color gamut space of the output device, the conversion ratio is adjusted in order to mix the colors in the visual perception. This conversion is often used to restore more demanding continuous manuscripts.

2. Chroma conversion. Chroma conversion can be divided into relative chroma conversion and absolute chroma conversion. The difference between the two lies in the different ways of processing the color that exceeds the matching color space before matching. The former replaces this part of the excess color with a boundary color, while the latter compresses this part of the color into the matching color space. This conversion is often used to adjust the display to ensure the same shade of color on different monitors.

3. Best color gamut conversion. This conversion is required to produce the purest and most saturated colors within the color space limited by the output device, rather than seeking to obtain the same colors as the original manuscript or display, and does not aim at color matching between different output devices. This conversion is often used for creative commercial printing.

To sum up, in order to ensure the maximum compatibility between the devices of the desktop publishing system, it is necessary to implement effective color management, first of all, to unify the color space of the entire system, and the unity of the space must rely on the Lab space independent of the device and the color gamut is very wide or other appropriate color space; Secondly, the system equipment should be characterized, and the system can be coordinated and unified when transmitting color information by using the color feature file of the equipment. In addition, when carrying out color space conversion, a color description language independent of the device should be selected, and the color gamut that can be displayed by printing should be used as a benchmark to establish a suitable innuendo relationship. At the same time, we should choose the appropriate color space conversion mode according to different situations.

Generally speaking, the specific operation and implementation of color management can be divided into two kinds: one is manual management method; The other is a software management approach. The so-called manual management method refers to the measurement and adjustment for color control in the input and output cycle, which is basically a color management method that relies on the judgment and vigilance of professionals and is implemented with calibration and calibration as the main means. The so-called software management method is the color management method that uses the color management system in the production system.

The purpose of using this method is that the CMS can make the colors from the display to the proof to the print look the same regardless of the device and the manuscript used. The user simply presses the button and the computer does the rest. For example, some color management software can convert scanners, color monitors and final proofing or printing colors, and manage them in a coordinated manner, and ultimately achieve WYSIWYG. As long as the user operates according to the requirements of the color management software, the color compensation is automatically carried out by the color management software, and the best color reproduction effect is finally achieved. Even if you have no experience or expertise in color processing, you can produce satisfactory color pictures. In the entire process of printing graphic reproduction, pre-press treatment is the key to the whole process, give full play to the maximum compatibility of the performance of the pre-press treatment equipment, the implementation of the most effective color management, is the most important part of the realization of printing products to achieve good quality.