Technical methods and methods of gravure image color processing (a)

The color of commodity packaging is the key to affecting the sale of goods, and is reflected in the form of product content, technicality, and use. Therefore, handling the color of commodity packaging is the most important aspect of the gravure plate making process. Color is a complex issue, and the cost for each plate-making company to spend on color control has been difficult to reduce. Color problems have caused great waste of manpower, material resources, and time.

Of course, the problems are many, but one of the main reasons is that due to the profound changes in our country's gravure pre-press image processing, there are fewer original manuscripts, high-quality color reversal films and photos for scanning. More than 90% are electronic image files produced by advertising design companies, mainly MO discs (magnets, optical discs), most of which are of poor picture quality, various physical colors and original colors in the discs, and colors provided by customers. The color of the manuscript is very different. Therefore, it is necessary for the adjustment personnel to carry out meticulous color correction and re-creation processing so that the color of the picture must conform to the true color of the original object and meet the various requirements of the customer, and it must be consistent with the laws of the electronic engraving and printing art. Processing technology has become the key to the quality of Gravure Packing Plates. The industry calls it the most important face of Gravure. The leaders of many plate-making companies realize that it is powerless to change the quality of customer's original manuscripts. Only those who strengthen their color management and vigorously train planners, they use the higher artistry bases of the planners, the aesthetic vision and operating skills to the customer's electronic image files. Perform technical processing and re-creation processing to compensate defects such as poor picture quality and incorrect hue to improve product quality. The author believes that the current gravure plate making company should try its best to do a good job in the system engineering management of the entire plate making process, so that stable gravure printing proofing, digital proofs, electroplating process, standard electric carving curve, enhanced computer production, based on electricity Toning ensures the accurate transmission of color information and control of color information in the process of copying errors; on the other hand, we must cultivate more excellent colorists, so that they have a certain amount of artistic foundation, aesthetic level and scientific color, The understanding of the artistry and the methods and methods of mastering the color processing of gravure images, as well as the laws of gravure plate making and printing, and the combination of the pattern of color arrangement and the characteristics of merchandise packaging products with the suitability of printing, can exceed the expectations of the customers. Make quality products.

The following is a brief introduction to the techniques, methods, and essentials of color processing of gravure images studied and summarized by the author in the practice of gravure plate making for more than a decade.

First, the theory of gravure image color processing

According to the characteristics of commodity packaging products, the theory of gravure image color processing is: based on the true color of the original physical object, it should be dealt with according to people's heart color, and coordinate the original color and physical color and psychological color. Make a perfect copy consistently. Specifically: It is based on the original (physical, magnetic, and optical) color, based on the true color of the original object, in accordance with the color of people's hearts to re-creation. On the one hand, we must fully respect the original color of the goods and highlight the attributes of the goods; on the other hand, we must meet the requirements of customers, highlight the saturation of colors, and emphasize the commercial effects of color.

The method should be combined with the reduction of process technology and the re-creation of the heart color. The so-called reduction of arts and crafts, first of all to make the entire gravure plate making process standardization, standardization, data color management, combined with software-based automated color management, so that the screen color, digital proofing color and gravure proofing try to try to Close to achieve a digital proofing color and gravure ink proofing color reproduction accuracy to achieve 95% to 98%. And under certain printability conditions, the four basic standards of gravure printing art (gray balance, tone setting, color correction, sharpening enhancement) as the criteria, the first is to do a good job of the standard reduction of ash scanning The balance curve and the calibration color data ensure that the original is scanned after the black and white field is set and the original color can be restored after digital proofing. There must be a special emphasis on a technical point. "In order to produce a good product at the end, all the information needed for the product must be obtained from the original at the time of scanning. This is like recording music, first the microphone It's better, otherwise, quality can't be discussed." The second is the external electronic image file, and then through the adjustment of the picture color, the digital proofing picture reduction electronic fully reflects the picture color or the color draft picture. Finally through the electronic artwork. This is the fundamental of gravure image reproduction technology, and is also the scientific nature of gravure image color processing. It should be treated as a science.

The so-called re-creation of the heart color, this is because the color is not only a physical phenomenon, but is affected by people's heart factors. Therefore, on the basis of the standardization of the above-mentioned scans, based on the color of the commodity industry, in accordance with people's heart colors, as well as the defects of originals and customer requirements, various tools of photoshop software are used for technical processing and re-creation. Processing, that is, appropriate exaggeration and rendering of the color, so that it is better than the original, but also beyond the expectations of customers, but also to meet people's heart color requirements. This is the art of color processing of gravure images and the beauty of color processing. It should be treated as an art. Only when the two are closely combined, can we produce high-quality products with high quality and efficiency.

Second, before dealing with color, clear color basis

Before the printmaking, what should be the basis for clarifying the color? It is necessary to carefully read the process sheet to understand the customer's requirements for the color of the picture. It is based on the color correction of the optical disc and the color draft, and it is based on the reversal film, photograph, printed matter, etc. Specific basis, these must be made clear in advance. If the basis is ambiguous or the basis is wrong, then all previous efforts will be abandoned. One of the reasons why the plate-making company has caused many internal and external reworks is that the prior color basis is unclear and unclear.

The second is to clarify the printability of the post process. One is to understand what substrates are? Is it film or paper? If it is a film, is EOPP film, PE film, pearl film, optical film, matt film, or PA nylon film, PET polyester film, heat sealing film and so on. Such as paper, white paper, or kraft paper. And understand the characteristics of various paper textures such as tightness, smoothness, and whiteness. The second is to understand the ink characteristics, is the ink, ink or blue sky, pink ink? And master three indicators of various inks, with gray, color cast and efficiency.

Third, we must specify which printing house the customer is. The plant's machine is a high-speed machine, a medium-speed machine or a low-speed machine, and it has mastered the printability conditions and the changing rules of the dots used in the plant, especially to master the transfer of energy. What is the minimum and maximum outlet value? If we do not understand the suitability of printing and we don't grasp the law of dot change, then there will be no basis for scanning settings, tone adjustment, and color adjustment. It must be blind. One of the contradictions between many plate-making companies and printing houses is that the layout planners do not understand the printability of the product and the changing rules of its outlets. This often results in the inability of the transfer of small outlets and the failure of color to catch up with gravure proofing. Sample proof and fur.

Third, the processing steps

When dealing with maps, it is first necessary to have a clear idea of ​​the "purpose" and the approach taken to achieve this "purpose." That is to say, first of all, what kind of picture quality should be produced according to the picture of this product packaging bag? Conversely, what kind of technical processing and re-creative processing should be adopted to produce the expected image quality, in order to ensure the production of a graphic effect that meets the “purpose”, it is necessary to think in advance and analyze it clearly. There are several. Then follow the rules of color processing and adjust according to its sequential steps. It is impossible to adjust anything in any order, what you see, or what you think, and thus cause blind and inefficient repetition of adjustments. Proceed as follows:

1. Interpretation of the original. Before the operation, we must first use our own aesthetic and concave process laws to interpret the manuscript, interpret the main body of the packaged product, what are the characteristics of the product attributes, what are the features of the physical color in the impression, and analyze and contrast the discs What are the differences between the colors of the drawings provided by the customer and the analysis of the gray balance, the tone level, the color reproduction, and the sharpness of the four basic standards? Are the data conforming to the printability requirements of the product? What are the advantages and disadvantages? , And in mind, to what extent is it best to adjust it to the reference screen color?

In practice, the author realized that: in advance, the interpretation of the manuscript is not interpretable, and the interpretation is not deep enough. Only the interpretation is deep, the analysis is thorough, the idea is high, that is, the eye height is achieved, and then the correct method is used for processing; If you are tall, you can make quality products quickly and well. If you don't have high eyes, your hands won't rise.

2. Color space mode conversion. Currently, there are two kinds of color space modes for external electronic image files. One is the GRB mode in which GCR generates color separations; the other is that the RGB mode in which GCR generates color separation has been converted to the CMYK mode, and most of them are now in this mode. Both are GCR's long-range blacktone process. Therefore, it should be converted or adjusted to meet the requirements of gravure packaging products based on the three primary colors, black version of the skeleton of the process data.

The first mode only needs to be transferred by setting the CMYK color separation parameters of the gravure three primary colors as the main process, which is more convenient. The second mode has four conversion methods: automatic calculation method, filling method, selection tool adjustment method, and secondary conversion method. Can be selected according to the simple and complex conditions of the original image.

In the mode conversion, the setting of the CMYK color separation parameter is very important, it will directly affect the printing effect, and the best setting of the gravure is as follows (Figure 1):